ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES DEPARTMENT OF CHEMICAL ENGINEERING
Cleane Cleanerr Product ion Opportunit y Assessment of Soap and Detergent Detergent Factory: the case of Repi Repi Soap and Detergent Detergent S.Co. S.Co.
A Thesis Submitted To the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Chemical Engineering (Environmental Engineering)
BY: MULUGETA YILMA TSEGAYEA ADVISOR: Dr Ing. NURELEGNE TEFERA
January, 2009 Addis Ababa
ACKNOWLEDGMENTS I would like to express my deepest gratitude to Dr Ing. Nurelegne Tefera for his guidance, support and advice throughout the study and preparation of this thesis.
I would also like to express my gratitude to department heads and staffs in the quality control, production, technical and administration of Repi Soap and Detergent S. Co, for their valuable information and support during the assessment work.
I am indebted to Coal Phosphate Fertilizer Complex Project (COFCOP) management and staff (especially Ato Kassaye Yeshitela, Ato Bogale Kena and Desta W/Gabreiel) for their assistance and understanding.
I am very much grateful to my parents, brothers and sisters for their support and encouragement. Thank you so much.
I very much thank my friends (especially Andinet Abebe, Endashaw Kinfe, Tsegaye Gebre, Eyob Tefera, Jemal Yassin, Debrish Menberu and Tatek Temesgen) for sharing their thoughts, ideas and encouragement. Last but not least, I am very much grateful to my dear friend Abaynesh Yihdego for encouraging me in a unique way.
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ABSTRACT As consumption trend of soaps and detergents rise in Ethiopia, assessment of the environmental performance of the industry becomes vital. Hence, Cleaner Production Assessment was conducted on Repi Soap and Detergent Share Company (RSD). This paper focuses on determining the quantity and quality of waste water generated, the prospect of utilizing laundry wastewater for irrigation in RSD and its impacts on the environment, the amount and type of raw material used and energy consumed by the processes using Cleaner Production Assessment principles. Literature review of this study suggests that that Sodium tri-poly phosphate (STPP), which was used as a raw material in RSD, causes disposal problem due to its potential to cause eutrophication. This raw material can technically be replaced by zeolite A and polycarboxylates in combination. However the Quality and Standards Authority of Ethiopia's regulation requires that a detergent must must contain a minimum of 10 per cent phosphate content. Hence, there is a need to adjust this regulation in accordance with the current local environmental condition. From the assessment in RSD, the wastewater from the factory was mixed with wastewater overflow from toilet septic tank to be used for growing vegetables; however, from experimental results the quality of the wastewater far exceeds some of irrigation water standards and can pose potential threat to the environment. By implementing Cleaner Production options (good housekeeping and input substitution) wastewater discharge to the environment would be reduced by 84.28 per cent. On the other hand thermal insulation of the furnace and improving thermal efficiency of the spray dryer can save birr 55,232.63 and 187,834.04 per year respectively. Moreover, lowering the moisture content of the slurry and powder can save birr 487,258.44 per year. In addition to these, thermal insulation of deareator, recovering condensate and replacing dilapidated steam trap can save birr 195,277.45 per year. Therefore by implementing Cleaner Production options, the company can save birr 926,158.61 per year. The results of this paper would be used to evaluate environmental performance of the detergent industry and the reuse potential of laundry wastewater for irrigation purpose. Also it can serve the purpose of assessing both raw material and energy consumption of the detergent industry.
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Table of Contents Title
Page
ACKNOWLEDGMENTS
I
ABSTRACT
II
LIST OF FIGURES
VI
LIST OF TABLES
VII
ABBREVIATION
VIII
1. INTRODUCTION
1
1.1. DETERGENT PRODUCTION IN ETHIOPIA AND ASSOCIATED PROBLEMS
2
1.2. THE STATEMENT OF THE PROBLEM
3
1.3. OBJECTIVE OF THE STUDY
4
1.3.1. Specific Objectives
4
2. LITERATURE REVIEW
5
2.1. CLEANER PRODUCTION
5
2.1.1. Types of Cleaner Production Options
5
2.1.2. Reasons to Invest in Cleaner Production
6
2.2. OVERVIEW OF DETERGENT PRODUCTION
6
2.2.1. Composition of Laundry Detergents
6
2.2.2. Formulation of Detergents
10
2.2.3. Powder Detergent Production
11
2.2.4. Liquid Detergent Production
15
2.2.5. Bar Detergent Production
15
2.3. UTILITIES REQUIRED FOR DETERGENT PRODUCTION
17
2.3.1. Energy
17
2.3.2. Steam
17
2.3.3. Water supply
17
2.4. EFFLUENT DISCHARGE
18
2.4.1. Laundry Water Reuse Potential for Irrigation
iii
18
2.4.2. Reclaimed Laundry Water Quality for Irrigation
19
2.4.3. Health Assessment of Laundry Water Reuse
22
2.5. E NVIRONMENTAL STANDARDS
23
2.5.1. Surface Water Standards
23
2.5.2. Irrigation Water Standards
23
3. CLEANER PRODUCTION METHODOLOGY
27
3.1. I NITIAL CHECKLIST
27
3.2. TASK 1: PLANNING AND ORGANIZATION
28
3.3. TASK 2: PRE-ASSESSMENT
28
3.3.1. Company Description and Flow Diagrams
28
3.3.2. Walk-Through Inspection
29
3.4. TASK 3: ASSESSMENT
30
3.4.1. Compiling Facility Data
30
3.5. TASK 4: EVALUATION AND FEASIBILITY STUDY
35
3.5.1. Prioritization of Opportunities
35
3.5.2. Evaluation of Technical, Economic and Environmental Feasibility
35
3.6. TASK 5: IMPLEMENTATION AND MONITORING 4. CLEANER PRODUCTION ASSESSMENT IN RSD
37 38
4.1. STEPS TAKEN FOR CLEANER PRODUCTION ASSESSMENT IN RSD
38
4.2. GENERAL DESCRIPTION OF R EPI SOAP AND DETERGENT S.CO
39
4.3. PROCESS DESCRIPTION AND PROCESS FLOW DIAGRAM FOR POWDER DETERGENT PRODUCTION
41
4.3.1. Slurry Preparation
42
4.3.2. Slurry Filtration and Pumping
43
4.3.3. Slurry Drying and Powder Storage
45
4.3.4. Hot Air and Steam Production
46
4.4. PROCESS DESCRIPTION AND FLOW DIAGRAM FOR LIQUID DETERGENT PRODUCTION
47
4.5. PROCESS DESCRIPTION AND FLOW DIAGRAM FOR BAR DETERGENT PRODUCTION
48
4.6. MATERIAL AND E NERGY BALANCE
49
4.6.1. Powder Detergent (ROL) Production Quantitative Data
iv
50
4.6.2. Liquid Detergent (Largo) Production Quantitative Data
62
4.6.3. Bar Detergent (Ajax) Production Quantitative Data
63
4.6.4. Summary of Results
65
5. DISCUSSION
69
5.1. GOOD HOUSEKEEPING AND STAFF TRAINING
69
5.2. HEAVY FUEL LOSS
69
5.2.1. Furnace
69
5.2.2. Spray Dryer
70
5.2.3. Boiler
74
5.3. STEAM LOSS
76
5.3.1. Boiler Steam Header
76
5.3.2. Deareator
76
5.4. CONDENSATE LOSS
76
5.5. SERVICE WATER LOSS
76
5.6. LAUNDRY WASTEWATER
77
5.6.1. Replacing STPP with Zeolite A
77
5.6.2. Laundry Wastewater for Irrigation Purpose
79
5.7. Implementation and Monitoring
84
6. CONCLUSION AND RECOMMENDATION
86
REFERENCES
88
APPENDIX 1 - LABORATORY A NALYSIS METHOD,R EAGENT AND APPARATUS REQUIRED
93
APPENDIX 2 - EXPERIMENTAL A NALYSIS R ESULT
99
APPENDIX 3 - R ESOURCE CONSUMPTION AND WASTEWATER GENERATION
100
APPENDIX 4- PROCESS PARAMETER MEASUREMENTS
102
APPENDIX 5 - STEAM PIPE CAPACITIES
103
APPENDIX 6- STANDARD R EQUIREMENTS FOR DETERGENTS IN ETHIOPIA
104
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LIST OF FIGURES
Figures
Page
2.1.
Simplified flow sheet for powder detergent production
11
2.2.
Flow diagram for a typical bar detergent production
16
3.1.
Hourly steam loss from leaks as a function of steam plume length
31
3.2.
Quantity of heat released at various temperatures
33
4.1.
Flow diagram of powder detergent production in RSD
41
4.2.
Flow diagram for slurry preparation
42
4.3.
Flow diagram for filtration and pumping of slurry
43
4.4.
Flow diagram for processes from slurry drying and powder storage
45
4.5.
Flow diagram for hot air and steam production
46
4.6.
Flow diagram for Largo (Liquid detergent) Production
47
4.7.
Flow diagram for Ajax (bar detergent) production
48
4.8.
Flow diagram for paste preparation
52
4.9.
Flow diagram for slurry preparation
53
4.10. Flow diagram for filtration and pumping of slurry
55
4.11. Flow diagram for air lift and cleaning
58
4.12. Flow diagram for packing
59
4.13. Flow diagram for furnace (hot air preparation)
60
4.14. Flow diagram for boiler
61
4.15. Flow diagram for Largo production
62
4.16. Flow diagram for bar detergent (Ajax) production
64
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LIST OF TABLES
Tables
Page
2.1. Indicative composition of typical laundry powder detergent
10
2.2. Amount of water lost due to leakage
18
2.3. Effluent discharges to land waters
23
2.4. The 1989 WHO guidelines for the use of treated wastewater in agriculture
25
2.5. Controlled application of effluent to lands
26
4.1. Raw materials used for powder, liquid and bar detergents production in RSD
40
4.2. Raw material to be used for powder, bar and liquid detergents
65
4.3. Electrical energy and fuel consumption
66
4.4. Steam consumed and wasted by the processes
67
4.5. Service water used in the processes
67
4.6. Wastewater generated in the process
68
5.1. Thermal efficiencies for various possible hot gas temperatures in RSD
71
5.2. Parts water evaporated to produce a part of powder
72
5.3. Benefits to be obtained on the tower
73
5.4. Comparative presentation of RSD wastewater laboratory results with standards
79
5.5. Technical, Economic and Environmental feasibility in RSD
83
5.6. Summary of Cleaner Production (CP) Opportunities for RSD
85
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ABBREVIATION
BOD
Biological Oxygen Demand
CMC
Carboxy Methyl Cellulose
COD
Chemical Oxygen Demand
CP
Cleaner Production
EC
Electrical Conductivity
EPA
Environmental Protection Authority
FAO
Food and Agriculture Organization of the United Nations
GHK
Good House Keeping
LABS
Linear alkylbenzene sulfonate
MPN
Most Probable Number
RSD
Repi Soap and Detergent S. Co.
SAR
Sodium Adsorption Ratio
SCMC
Sodium Carboxy-methyl Cellulose
STS
Sodium Tolune Sulfonate
TDS
Total Dissolved Solids
TN
Total Nitrogen
USEPA
United States Environmental Protection Agency
UNIDO
United Nations Industrial Development Organization
UNEP
United Nation Environment Program
WHO
World Health Organization
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1. INTRODUCTION Detergents are any substance or preparation containing soaps and/or other surfactants intended for washing and cleaning processes. Detergents may be in any form (liquid, powder, paste, bar, cake, moulded piece shape, etc.) and marketed for or used in household, or institutional or industrial purposes [1].
A detergent derives its cleaning ability from its dual water-attracting (hydrophilic) and waterrepelling (hydrophobic) properties. When detergents are introduced into water these properties cause the detergent molecules to aggregate into spherical clusters called micelles with the hydrophilic components in the water and the hydrophobic components in air or dissolved in fatty soils (dirt). This causes a reduction in interfacial tension which when combined with the mechanical action of washing causes dirt molecules to be easily removed from the fabric and into the wash water [2].
Population growth, particularly households with children, drives demand in the consumer sector, while economic growth drives demand in the commercial sector. The profitability of individual companies depends on efficient operations and effective sales and marketing. Large companies have scale advantages in purchasing, manufacturing, distribution, and marketing. Major companies in the consumer sector include divisions of Proctor & Gamble (P&G), Unilever, and Dial. Major companies in the commercial sector include divisions of Ecolab and US chemical. The industry is highly concentrated: the top 50 companies hold almost 90 percent of the market. Small companies can compete effectively by offering specialized products, providing superior customer service, or serving a local market [3, 4].
A distinction must be made between developed and developing countries because their needs are not the same. In developing countries soap remains the main (and often only) detergent for almost all types of cleaning. In developed countries, the range of products is much wider to meet specific consumer needs [4].
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1.1. Detergent Production in Ethiopia and Associated Problems Synthetic detergents have been in the Ethiopian market for decades. However, similar to other developing countries, soap has been mainly used in Ethiopia. Nowadays, the demand for detergents is growing because of better awareness towards the performance of detergents. In parts of northern Ethiopia where surface water is hard, detergents are used widely due to their superior performance over soaps. It is expected that the demand for synthetic detergents will continue to grow and this in turn will induce growth in the industry. Factors contributing to this demand include the rapid population growth, greater awareness, increased urbanization and expected growth in incomes.
In Ethiopia detergents are produced in four main factories: Repi Soap and Detergent S. Co., East African Group Chemical Industry, Star Soap and Detergent Factory and Geteshet Soap and Detergent Industry. Among these industries, Repi Soap and Detergent S. Co. and Star Soap and Detergent Factory are located in Addis Ababa and the other two are along the main road between Dukem and Debrezeit. Repi Soap and Detergent S. Co. was established in 1974. The other three have been in business for less than a decade. Most of these industries were not operating in full capacity mainly due to market unavailability for their products. Imported products among many, Zahara and Aerial, have been very popular in the Ethiopian detergent market. Hence, imported products enjoy the wide domestic market for powder detergents.
The detergent industry uses water, energy and chemical raw materials like Sodium Tri-Poly Phosphate (STPP) that can be a problem for disposal. Spray dryers in detergent factories use high energy and can be inefficient, if the operating parameters are not well controlled. Steam can be wasted in detergent industries in the form of leakage or through failed steam traps. Condensate un-recovered can result in substantial loss of energy. Heat loss from hot surfaces like furnace can be saved by performing thermal insulation. Water in detergent industries is used mostly for the process, but wastewater is still created due to mismanaged processes.
2
For production processes, Cleaner Production aims in particular at conserving raw materials and energy, eliminating toxic raw materials, and reducing the quantity and toxicity of all emission and wastes before they leave the process or source reduction. In the case of products, Cleaner Production aims at reducing the environmental impact along the life cycle of a product, from raw materials extraction to its ultimate disposal. Finally, for services, Cleaner Production entails the incorporation of environmental concerns into designing and delivering services. Cleaner Production requires changing attitudes, responsible environmental management and evaluating technology options [5].
1.2. The Statement of the Problem Environmental policy of chemical industries cannot limit itself simply to ensuring that safe products are put on the market which do not accumulate in the natural environment. It applies as well as to the production of raw materials for which systematic research toward cleaner and more energy-efficient processes needs to be mounted [4]. When phosphate detergents are used, disposal of wastewater is an issue. One consequence of the use of STPP in the domestic environment can be increased phosphate in household waste water, which may then contribute to the phosphorus load in rivers, lakes and inshore waters. The presence of phosphates in waste water can be an environmental issue because of “eutrophication”, the increase of nutrient levels in water, which can lead to environmental problems such as the formation of large masses of algae or blooms which are unsightly, causing slow moving water to be turbid, and may be toxic [6]. This may increase decomposer organisms that require oxygen, which can deplete the amount of oxygen dissolved in the water. Excessively large numbers of decomposers may reduce the oxygen levels to the extent that other aquatic organisms die from lack of oxygen. Decomposer populations grow in response to an increase in their food, such as detergent components and, in the drier summer months, the dying excess algae [7].
Reusing greywater for gardens may detrimentally alter the properties of soil and gradually kill plants sensitive to phosphorus. Many of these contaminants are classified as plant nutrients and if disposed to waterways or groundwater may cause environmental damage and toxicity to animal
3
and human through consumption. The microbiological contamination in laundry water also raises concern on the risk of human infection by bacteria, viruses and other infectious pathogens [8].
In RSD, STPP is used as a builder for the detergent formulation. Wastewater from toilet and factory were mixed and used in the factory compound for Salad and cabbage irrigation purpose for fear that it might upset the quality of the nearby river if discharged to it. However, this can pose potential threat to public health and plant growth and may also affect the basic structure of the soil used for irrigation.
In RSD electrical and fuel energy consumption by the processes such as spray drying was high that optimization is important to save energy loss.
1.3. Objective of the Study The general objective of this research is to conduct cleaner production assessment for the soap and detergent production: the case of Repi Soap and Detergent S. Co.
1.3.1. Specific Objectives The specific objectives are to:
Generate cleaner production options. Analyze cleaner production options generated in terms of technical, financial and environmental feasibility.
Assess costs and benefits of switching from STPP to zeolite-based detergents.
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2. LITERATURE REVIEW 2.1. Cleaner Production Cleaner Production is generally defined as “the continuous application of an integrated preventive environmental strategy to processes, products, and services to increase eco-efficiency and reduce risks to humans and the environment” (UNEP, 1994). Cleaner Production aims at progressive reductions of the environmental impacts of processes, products and services, through preventative approaches rather than control and management of pollutants and wastes once these have been created [5].
2.1.1. Types of Cleaner Production Options 1. Good housekeeping practices imply procedural, administrative, or institutional measures that
a company can use to minimize waste and emissions. Many of these measures are used in industry largely as efficiency improvements and good management practices. Good operating practices can often be implemented with little cost. These practices can be implemented in all areas of the plant, including production, maintenance operations, and product storage [9]. 2. Input substitution refers to the use of less polluting raw and adjunct materials and the use of
process auxiliaries (such as lubricants and coolants) with a longer service lifetime [5]. 3. Technology modifications are oriented towards process and equipment modifications to
reduce waste and emissions, preliminary in a production setting. Technology changes can range from minor changes that can be implemented in a matter of days at low cost, to the replacement of processes involving large capital costs. These include the following:
Changes in the production process
Modification of equipment, layout, or piping
Use of automation
Changes in process conditions, such as flow rates, temperatures, pressures, and residence times [9].
5
4. Product modifications change the product characteristics, such as shape and material
composition. The life time of the new product is, for instance, expanded, the product is easier to repair, or the manufacturing of the product is less polluting
[5].
2.1.2. Reasons to Invest in Cleaner Production
Financial: Cleaner production improves your financial bottom line by: increasing
efficiency and productivity, reducing costs for waste disposal and treatment, reducing raw material, energy and water costs and reducing liability risks.
Environmental: Cleaner production improves your environmental bottom line by:
reducing pollution of waterways, air and land, and reducing risk of non-compliance with regulatory requirements.
Social: Cleaner production improves your social bottom line by: enhancing corporate
profile and marketing edge by demonstrating environmental responsibility (also indirectly improving your financial bottom line), reducing health and safety risks, improving staff morale and service [10].
2.2. Overview of Detergent Production 2.2.1. Composition of Laundry Detergents Detergents are comprised of four major types of ingredients: builders, surface active agents (surfactants), additives, and fillers [11]. Although the chemical composition of (phosphate and non-phosphate) detergents is continually being refined to maximise washing efficiency, the main ingredients have remained relatively constant over the last 20 years [1]. Surfactant
The surfactant or surface active ingredient performs the primary cleaning in detergents through the reduction of interfacial tension. This consists of completely wetting the dirt and surface of the item being washed, removing the dirt from the surface, and maintaining the dirt in solution
6
[2].
Basically, every surfactant is an organic compound consisting of two parts: a hydrophobic portion, normally including a long hydrocarbon chain, and a hydrophilic portion, which renders the entire compound sufficiently soluble or dispersible in water or other polar solvent to sieve its intended use [12]. Dodecyl Benzene or linear alkyl benzene sulfonates (LABS) are important raw materials (surfactants) required for the manufacture of synthetic detergents. Dodecyl benzene has no biodegradable property so it causes pollution and sewage problems. The use of dodecyl benzene is not encouraged nowadays. LABS surfactants are accepted as adequately biodegradable [4, 13]. Builder
Builder is a compound which works in synergy with the surfactant and is generally employed in domestic laundry detergents. Un-built detergents require the surfactant to perform the cleaning unaided and are mostly utilised by industries for washing of hard surfaces. The function of the builder is inactivation of the hardness ions by sequestration, precipitation or ion-exchange. Builders also counteract soil redeposition and provide pH buffering in the wash liquor
[2].
Phosphates had been widely used as builders since 1947. Comprised of condensed or complex phosphates and sodium, the most common phosphate used by the detergent industry was sodium tri-poly phosphate [11].
There was a move to phosphate-free detergents from the mid-1980s to the mid-1990s all over Europe. Countries like Belgium, Germany, Ireland, Italy, Netherlands and Austria have gone completely phosphate free. The rest European countries have banned the use of phosphate based detergents in some affected localities [1]. However, in 1995 phosphates remained un-banned and still widely used in Latin America and other developing regions. They were also used in industrial applications and in dishwashing detergents [5].
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Alternatives to phosphates in detergents
Concern about the environmental impact of phosphates in synthetic detergents resulted in the introduction of various controls and restrictions on the use of phosphates in household detergents. This led to a search for alternative builders [6]. The following are alternatives to STPP in synthetic detergent production.
Carbonates
Sodium carbonate is used in both phosphate and phosphate-free detergent formulations largely due to its low cost and other properties, notably alkaline buffering. Sodium carbonate softens the wash water by precipitation of hardness ions. To produce free-flowing powders carbonates have to be used together with silicates [2].
Sodium carbonate in household cleaning products has a negligible effect on the aquatic ecosystems and it has no adverse effect on consumers [1]. Sodium silicate
Sodium silicate is used in laundry detergent formulation to provide alkaline buffering and for corrosion control. Silicate has no effect on water softening or redeposition, but is a source of alkalinity in the wash water [2].
Although considered corrosive to eyes and skin, sodium silicates have a low toxicity and their use in detergents is not considered to present significant risks to human health or to the environment [1]. Carboxylic acids
Polycarboxylates are used in formulations as co-builders to disperse dirt particles and precipitates which would cause greying and encrustation on washing machine parts and fabrics. Polycarboxylates are unable to substitute STPP completely because they possess insufficient complexing capability, but their use during detergent manufacture are of considerable economic advantage as they result in better homogenization and stabilization [2].
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Zeolite A and its cobuilders
Zeolite A is a water-insoluble sodium aluminosilicate and is one of the many types of sodium aluminium silicates that is applicable for use in detergents
[2].
Zeolite A has a reasonable performance in abstracting calcium and magnesium ions but is limited as a builder. It does not buffer during the washing process and does not prevent redeposition of soil particles in the wash liquid, so it has to be used with a cobuilder, usually polycoarboxylic acids. Zeolites do not present significant risks to people or to the environment
[1, 6].
The United Nations stated that with regard to natural resources and future production capacities, there were no serious restrictions against total replacement of STPP by zeolite A
[2].
Hence, a
combination of zeolite A with polycarboxylates can be used to replace STPP for detergent production. There by, minimize eutrophication problems caused due to phosphate in detergents. Additives
Additives are used to improve the performance of the detergent and include anti redeposition agents, bleach stabilizers, enzymes, fabric-whitening agents, foam controllers, corrosion inhibitors, perfumes and colourants [2]. Fillers
All of the ingredients in a detergent are not active. In so-called conventional powders, some ingredients do not play a part in wash performance. However, some of these components are necessary for the manufacturing process, such as water (in sufficient quantity to hydrate the salts, particularly in phosphate formulas), and toluenesulfonate (to reduce slurry viscosity), for example. In general, powders contain a certain quantity of fillers. The most frequently used of these is sodium sulfate, which is cheap because in general it is a by-product of chemical manufacture [4].
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2.2.2. Formulation of Detergents Laundry detergents are produced in two major types of formulations: Powder and Liquid. Powders are generally more effective in removing clay and ground-in dirt, while liquids work well on oily soils [11].
Each large manufacturer has particular secrets and know-how that make a difference in the final product. For example, the simple application of a well-known process, such as spray drying a conventional powder, will not always result in product with little sodium tri-poly phosphate breakdown, good flow properties, and satisfactory behavior in the washing machine [4]. Although there are numerous formulations of phosphate detergents, Table 2.1 provides an indication of the typical compositions of the main product types used in laundry detergents [1].
Table 2.1. Indicative composition of typical laundry powder detergent Raw materials
Surfactants
Composition (%) for STPP
Composition (%) for
based detergents
zeolite based detergents
12
15-30
Builders STPP
20-25
Zeolite A
0
25
Polycarboxylates
0
4
Phosphonates
0-0.2
0.4
Sodium silicate
6
4
Sodium carbonate
5
12
Sodium perborate
14
24
Activators
0-2
2
Performance additives
12-35
1.5
Water
balance
balance
Bleaches
10
2.2.3. Powder Detergent Production The primary production methods for powder detergents are spray-drying, agglomeration, and dry mixing. Spray-drying involves spraying a mixture of liquid and dry ingredients through nozzles to form small droplets, which then fall through a current of hot air and form hollow granules as they dry. In agglomeration, dry raw materials are blended with liquid materials by rolling or mixing. Dry mixing is used to blend primarily dry raw materials, although small quantities of liquids may be added [11].
Air
Builder
Cyclone
Active matter Spray dryer
Dust collection
Slurry mixer
Hot air Slurry Water
Powder for cooling and separation Figure 2.1. Simplified flow sheet for powder detergent production
Traditional detergent powders are manufactured in three stages. 1. Preparation of a mixture of liquid and solid raw materials (the ‘‘slurry’’), which can stand high temperatures, and which is then atomized (‘‘spray drying’’). 2. The ‘‘base powder’’ thus produced is allowed to cool before the more sensitive ingredients are added, that is ‘‘post dosing’’. 3. The final powder is packed. Figure 2.1 shows a simplified flow sheet for spray-drying powder detergent production [4].
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Slurry preparation
When slurry is made batch wise, the main liquid ingredients are charged and the powders added to them, as is necessary to maintain a mixable liquid through the process [14].
It is obvious that if a sulphonic acid is used as the basic material it must be neutralized, either continuously or batch-wise, and it is essential to do this before the acid comes into contact with the rest of the ingredients of the slurry. Otherwise, insoluble silica may be precipitated, the polyphosphate can easily be hydrolyzed to orthophosphate; and the optical brightener may also be affected adversely. In continuous operations, the sulphonic acid and caustic soda should be fed into a neutralizing vessel with all the water required for the slurry. This sodium sulphonate paste is then fed into the slurry preparation vessel, where the rest of the ingredients are added [15]. After treatment of slurry
Some ageing of the slurry is desirable for the formation of sodium tripolyphosphate hexahydrate, as well as necessary to provide a small buffer from which the drier can be fed; about 20-30 minutes is often suitable [14].
Conversion of the slurry into powder requires the use of pressures upto 8.0MPa. The most practical means slurry transport uses a slowly moving three-plunger pump, usually preceded by a low-variety. Between the storage vessel and the high-pressure pump, it is advantageous to provide a magnetic separator, sieves, and /or wet-grinding mills for removing metallic objects and large particles or agglomerates that might otherwise clog the spray nozzles. Bulk density can be increased by evacuating the slurry, where as deliberate introduction of air can be used to reduce the density. Any sudden changes in pressure in the high-pressure portions of the system are compensated in an air vessel [16]. The hot gas generator and the fans
Inlet temperatures of 250 O C -400 O C have been common for detergent powders, but improved hot gas inlet design may permit up to about 450 O C. It will be seen that thermal efficiency increases as the gas inlet temperature rises. This is because a smaller mass of gas is required to achieve a given amount of drying; and this gas, which leaves at a temperature substantially
12
independent of the inlet temperature, carries with it less heat than larger mass of gas used when the inlet temperature is lower [14]. Atomization
The purpose of the atomizer is to meter flow into the chamber, produce populations of liquid particles of the desired size and distribute those liquid particles p articles uniformly in the drying chamber. ch amber. The selection of a specific atomizer is made based on the feedstock, the required powder properties, the dryer type and capacity and the atomizer capacity [17]. Slurry is distributed in the tower head by a ring tube connecting a series of nozzle guns, each equipped with swirl nozzles. Atomization occurs as the slurry emerges from the nozzles. The number of nozzles and their types must be such that individual spray cones do not overlap, and the sides of the tower should remain clean [16].
Spray drying
Spray drying chambers typically are vertical vessels with a cylindrical cross-section and a conical bottom. The size of the cylindrical and conical sections depends on the application needs. Different spray dryer designs can be obtained by passing the heating gas either co-currently or counter-currently to the feed solution by a different choice of atomizer. Normal counter-current detergent powder towers include an element of mixed flow in that a small proportion of cold air is drawn into the base of the tower where the powder leaves. This would be difficult to avoid because the tower is operated at a very slight negative pressure (a few mm water gauge), so as to avoid the blowing out of hot gas, spray or powder. The cold air provides useful cooling of the powder, so there is no need to attempt any form of sealed powder discharge which would be difficult with warm sticky powder [14, 18].
The residence time in the chamber refers to the time required for the droplets to fall, due to gravitation and air flow, through the chamber. The amount of drying is, therefore, a function of the driving potential (vapor pressure differential), the mass transfer coefficients, and the residence time in the chamber [19].
13
Air-pressures in spray-drier towers are usually balanced to range between 0-5 pa vacuum water gauge. This is accomplished by means of dampers on either the inlet air duct or exhaust duct, or both. The rate of exhaustion of air a ir plus vapour is adjusted to be either equal to or slightly greater than the rate of ingress of hot air into the chamber. Positive pressure inside the tower is not advisable since it may cause blowing out of dust. The vacuum in the chamber can be raised, however, quite easily to 125 pa water gauge provided that the tower is sealed off at its base with a rotary valve or other sealing-discharging device. The increased vacuum will retard the rate of fall of the dried particles and thus extend the residence in the tower. At the same time the higher vacuum will tend to add to the amount of fines produced, the actual increase being dependent on the particle spread of the powder [15].
Counter-current contact gives powders a bulk density 0.15-0.45 (more usually 0.3-0.4) g/mL and a moisture content of 6-15%, commonly about 10%. Contrary to general belief the outlet air temperature need not be above 100oC to obtain a desirable product. Spray-driers can work efficiently at temperatures well below 100oC. However, for a bone dry powder the temperature must be in the vicinity of 100oC or near the boiling point of water at the altitude of the particular plant [14, 15].
Separation
The powder which leaves the tower at 60-70oC required to be:
Cooled further and weathered; that is salts allowed to crystallize in hydrate form. Mixed with ingredients not included in the slurry, such as perfume, sodium perborate, and enzymes.
Screened to remove any coarse material, which needs to be re-slurried (this may be done before, or after, dosing with ingredients, or both).
Conveyed directly to the packaging machines, or to intermediate storage [14]. Storage and packing
If a powder must be stored in ambient relative humidity exceeding 60 per cent, the risk of lump formation can be minimized by discharging the powder from the spray-tower with at least threequarters of the stable moisture content. It is economically unsound to dry a powder to 1 per cent
14
moisture content when the powder must revert to, say 7 per cent. The operation would be a lot more efficient if the powder were dried to 7 per cent in the first place. After storage, the product obtained is then put into packets, boxes, or drums equipped with a dosing system
[4].
2.2.4. Liquid Detergent Production Liquid detergents can be made from a variety of starting materials, but in every case the plant is the same. A vessel equipped with a slow-speed stirrer is all that is required and the stirrer should be positioned so that it is well under the surface of the liquid, so as not to cause foaming. It is, however, necessary that the vessel be of a non-corrdible material. Stainless steel is satisfactory, but expensive; concrete or asbestos cement vessels are eminently suitable, and so are those of glass-fiber reinforced plastics. To the user, the advantages are that they are instantaneously dispersed in water, the material can be perfumed and be given a very attractive appearance [15].
Liquid detergents are produced through both batch and continuous blending processes. In the typical blending process, dry and liquid ingredients are combined and blended to a uniform mixture using in-line or static mixers [11]. Liquid detergents are distinctive because of their relatively high surfactant content (up to 40%). For reasons of solubility and stability, they seldom contain builders and generally are devoid of bleaching agents [16]. Liquid detergents can be packed in a range of containers including glass bottles and drums, but plastic bottles of various shapes and sizes are now normal for the domestic trade. Types of polythene of varying rigidity are most usual. Some products are packed in rigid bottles, but flexible squeeze bottles, with caps provided with a small hole, are virtually standard for dishwashing liquids. Packaging lines can be very simple, with hand operations and semiautomatic fillers; but with the very large tonnages now being produced by major companies, the trend is to highly mechanized, high-speed, lines [14].
2.2.5. Bar Detergent Production Bar detergents are found predominantly in developing countries [4]. The sulphonic acid is mixed with the dry ingredients in a dough-mixer. After neutralization, the addition of any special
15
ingredients, the mass is allowed to age. This ageing varies with the formulation and further manipulation. If a bar of high active-matter content (60%) is being made, the mass should be aged for 12 hours. If a low active matter material (40 percent) is being manufactured, the mass can be transferred to the next stage immediately. In fact, it is not advisable to allow it to age, as it will set hard and become unworkable [15]. After the requisite ageing period, the mass is passed through a soap mill. In certain factories this milling is dispensed with and the aged mass is fed directly into a plodder. However, the appearance and texture of the finished product is definitely inferior if it is not passed through a mill [15].
LABS and solid ingredients
Dough mixer
Miller
Cutter
Plodder (extruder)
Packing and storage Figure 2.2. Flow diagram for a typical bar detergent production After milling, the chips are fed into a plodder and extruded into the required shape, cut on soapcutting tables and stamped [15]. Flow diagram for bar detergent production is shown in figure 2.2.
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2.3. Utilities required for Detergent production 2.3.1. Energy Industry uses energy for a variety of purposes. Steam production via conventional boilers and cogenerators is the largest use. Electric motor drive, which includes motors and the corresponding pumps, fans, compressors, and materials processing and handling is the next largest category [20].
Bare or improperly insulated steam pipes are a constant source of wasted energy because they radiate heat to the surroundings instead of transporting it to steam-using equipment. The heat losses reduce the steam pressure at the terminal equipment. This situation increases the boiler load because extra steam is required to make up the losses
[21].
2.3.2. Steam A steam-distribution and condensate-return system should deliver steam efficiently from the boiler plant to heating systems and processing equipment and return condensate to the boiler for re-use. Some energy is always lost from a steam and condensate system, most significantly in steam trap loss. Others include heat loss from piping and fittings (insulated and un-insulated), leaks and flash losses, condensate loss to drain and overall system losses
[21].
Techniques used to measure steam loss include hole size or equivalent circle method and Plume height method [22].
Energy losses can also be reduced with proper attention to steam distribution systems. This includes maintenance of steam traps and increased insulation of steam carrying pipes [20].
2.3.3. Water supply Inadequate water management is accelerating the depletion of surface water and ground water resources. A facility may have several water systems, some for process use (process cooling water, chilled water) and some for building services (potable water, domestic hot water).Whatever their function; water systems tend to have similar inefficiencies and energy management opportunities. Water losses are detailed in Table 2.2 [19, 21, 23].
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Table 2.2. Amount of water lost due to leakage Leakage rate
Daily loss (m3)
Monthly loss (m3)
Yearly loss (m3)
One drop/second
0.004
0.129
1.6
Two drops/second
0.014
0.378
4.9
Drops into stream
0.091
2.6
31.8
1.6 mm stream
0.318
9.4
113.5
3.2 mm stream
0.984
29.5
354.0
4.8 mm stream
1.6
48.3
580.0
6.4 mm stream
3.5
105.0
1,260.0
2.4. Effluent Discharge 2.4.1. Laundry Water Reuse Potential for Irrigation Water quality has been degraded by domestic and industrial pollution sources as well as non point sources. In some places, water is withdrawn from the water resources, which become polluted owing to a lack of sanitation infrastructure and services. Over-pumping of groundwater has also compounded water quality degradation caused by salts, pesticides, naturally occurring arsenic, and other pollutants. In urban areas, demand for water has been increasing steadily, owing to population growth, industrial development, and expansion of irrigated peri-urban agriculture [23]. Agricultural irrigation has, by far, been the largest reported reuse of wastewater. About 41 percent of recycled water in Japan, 60% in California, USA, and 15% in Tunisia are used for this purpose. In developing countries, application on land has always been the predominant means of disposing municipal wastewater as well as meeting irrigation needs. In China for example, at least 1.33 million hectares of agricultural land are irrigated with untreated or partially treated wastewaters from cities. Reuse has advantages as well as disadvantages at each level. The choice is conventionally technical and economic one, though some view it as important that the community as a whole should become more involved in the working of reuse systems [24].
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Wastewater contains a wide spectrum of pathogens and sometimes heavy metals and organic compounds that are hazardous to the environment and human health. Therefore, the World Health Organization advises treatment of wastewater before application to the fields, to protect farmers and crop consumers [25]. Laundry water is quite different in its quality from the potable water. It contains many substances, such as boron and phosphate, and the water is often alkaline and saline. Detergents used for washing clothes comprise of phosphorus, ammonia, organic nitrogen and boron in varying quantities [8].
Standards for wastewater reuse in many countries have been influenced by the WHO (1989) Health Guidelines and the USEPA/USAID (1992) Guidelines. The WHO guidelines (WHO, 1989), are significantly less strict, with the intention to introduce some treatment of wastewater prior to crop irrigation, particularly in developing countries. WHO guidelines are therefore more appropriate for these countries, at least as an interim measure until there is an ability to produce higher quality reclaimed water [26, 27].
2.4.2. Reclaimed Laundry Water Quality for Irrigation The chemical constituents in reclaimed water of concern for agricultural irrigation are salinity, sodium, trace elements, excessive chlorine residual, and nutrients. Sensitivity is generally a function of a given plant’s tolerance to constituents encountered in the root zone or deposited on the foliage. Reclaimed water tends to have higher concentrations of these constituents than the groundwater or surface water sources from which the water supply is drawn [28].
The potential environmental impacts associated with greywater are due to the many pollutants it contains, such as particles of dirt, lint, food and human waste products (even greywater from laundries and bathrooms will contain some body fats, urine, faeces or blood), and chemicals derived from detergents and other cleaning agents. If the greywater is untreated these pollutants can build up in the soil, damaging the soil’s structure, altering soil acidity/alkalinity balances and possibly harming plant growth [29].
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Salinity
Salinity is the single most important parameter in determining the suitability of the water to be used for irrigation. Salinity is determined by measuring the electrical conductivity (EC) and/or the total dissolved solids (TDS) in the water [28]. High salt concentration in wastewater applied to soil will lower the total water potential of soil and will affect water and nutrient uptake by plat roots. In addition, high ion accumulation inside plants may reach toxic level, which is detrimental to plants. Therefore, irrigation with highly saline effluent on soils may reduce plant productivity or, in extreme cases, kill crops and native vegetation [8].
Sodium
Laundry products, in particular, use a variety of chemicals that can be harmful to plants. Most soaps and detergents contain sodium compounds. High levels of sodium can cause discoloration and burning of leaves, and can contribute toward an alkaline soil condition. In addition, high sodium can be toxic to certain plants and can prevent calcium from reaching them. A second possible effect of some types of sodium is a disturbance of the soil’s ability to absorb water. The sodium adsorption ratio (SAR) is the parameter that measures the effect on the soil’s structure of sodium compounds. A high SAR (13 or above) will result in soils with reduced permeability and aeration, and a general degradation of the soil’s structure
[30].
Boron
Elevated levels of boron (B) may arise in laundry greywater due to presence of borate in bleaches and some detergents. Boron is considered as a plant micro-nutrient which plants require in very small amounts for their growth and physiological functions, such as aiding calcium and carbohydrate metabolism in plants. Most soils provide adequate amounts of this nutrient naturally [8].
Plant damage from exposure to excessive amounts of boron is first displayed by a burnt appearance to the edges of the leaves. Other symptoms of boron toxicity include leaf cupping, chlorosis, branch dieback, premature leaf drop and reduced growth [30].
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Trace elements
The elements of greatest concern at elevated levels are cadmium, copper, molybdenum, nickel, and zinc. Nickel and zinc have visible adverse effects in plants at lower concentrations than the levels harmful to animals and humans. Zinc and nickel toxicity is reduced as pH increases. Cadmium, copper, and molybdenum, however, can be harmful to animals at concentrations too low to impact plants [28]. Chlorine residual
Bleaches commonly contain chlorides that can also damage plants, particularly if the bleach water actually touches the foliage. One symptom of chlorine-induced damage is a tendency for new, expanding leaves to appear bleached. Ammonia is often used as a substitute for bleach, as it also breaks down grease, and is preferable as a household cleaning and deodorizing agent. Chlorine is undesirable for plants in large amounts, although it is found in small amounts in many municipal water supplies. Bleaches and detergents carry large amounts of chlorine [30].
Nutrients
The nutrients most important to a crop’s needs are nitrogen, phosphorus, potassium, zinc, boron, and sulfur. Reclaimed water usually contains enough of these nutrients to supply a large portion of a crop’s needs [28].
Leaching of N to the groundwater is one of primary factors limiting the re-use of effluent, containing high N concentration. Nitrate is the dominant form of N leached into groundwater and nitrate in drinking water has adverse effects on human health. Algal growth or eutrophication problem is also associated with runoff with high concentration of nitrogen into surface water bodies. For these reasons, information on nitrogen is needed for wastewater quality analysis [8].
Phosphorus is used in laundry detergents as a builder and deflocculating agent. The amount of phosphorus in laundry wastewater varies depending on the types of detergents used. Irrigation with laundry greywater could increase the amount of available phosphorus in soil for plant uptake; in particular, laundry wastewater discharge associated with the use of phosphate-based detergents. However, potential problems could occur from excess P loading when drainage
21
occurs, which could contaminate groundwater and may cause eutrophication through erosion of P-rich topsoil and a discharge of dissolved P in runoff to surface water bodies [8].
2.4.3. Health Assessment of Laundry Water Reuse Domestic wastewater, or “sewage”, can be divided into two categories: blackwater which originates from toilets and kitchens has gross faecal coliform contamination and generally has high concentrations of organic matter; and greywater which originates from bathrooms and laundries and constitutes the largest flow of wastewater [30].
Use of untreated wastewater for crop irrigation causes significant excess infection with intestinal nematodes in farm workers, in areas where such infections are endemic. In India, sewage farm workers had a significant excess of Ascaris and hookworm infections, compared with farm workers irrigating with clean water. The intensity of the infections (number of worms per person) and the effects of infection were also higher, e.g. the sewage farm workers suffered more from anaemia, one of the symptoms of severe hookworm infection. Transmission of cholera can occur to consumers of vegetable crops irrigated with untreated wastewater, as during the outbreak of cholera in Jerusalem in 1970. It appears that typhoid can also be transmitted through this route [27].
Indicator organisms
Coliform is a family of bacteria that is always present in soils and in all types of water and wastewater, even in high quality drinking water. The coliform group of organisms survives better in water environment than other pathogens; hence, coliform groups are commonly used as an indicator of water quality. Commonly, there are three ways of using coliform groups to indicate the quality of water. First, the test of total coliform bacteria indicates the cleanliness of the water supply to judge the adequacy of disinfection. The next common indicator group is thermotolerant (or faecal) coliform bacteria, which are a subset of total coliform and are used to indicate possible faecal contamination of water [8].
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2.5. Environmental Standards 2.5.1. Surface Water Standards General standards for industrial effluents in Ethiopia are shown below in Table 2.3.
Table 2.3. Effluent discharges to land waters Constituent group or
Emission limit value(mg/L)
parameter
pH
6-9 pH units
BOD5 at 20oC
80
COD
250
Total Kjeldhal Nitrogen (as N)
80
Nitrate (as N)
20
Total phosphate (as P)
10
Magnesium (as Mg)
100
Calcium (as Ca)
100
Chloride (as Cl)
1000
Sulphate (SO4)
1000
Total Coliforms (Number per 400 100mL) Source: Standards for Industrial Pollution Control in Ethiopia (2003) 2.5.2. Irrigation Water Standards
While wastewater reuse for agriculture has many benefits, it should be carried out using good management practices to reduce negative human health impacts. The WHO initially published Guidelines for the Safe Use of Wastewater and Excreta in Agriculture and Aquaculture in 1989 and later revised it as “Guidelines for the safe use of wastewater, excreta and grey water, volume 2: wastewater use in agriculture” (WHO 2006). The Guidelines are set to minimize exposure to workers, crop handlers, field workers and consumers, and recommend treatment options to meet the guideline values (WHO, 2006). The Guidelines are focused on health-based targets and
23
provide procedures to calculate the risks and related guideline values for wastewater reuse in agriculture [23].
WHO (1989) Guidelines for the safe use of wastewater in agriculture took into account all available epidemiological and microbiological data and are summarised in Table 2.4. The faecal coliform guideline (e.g. =1000 FC/100mL for food crops eaten raw) was intended to protect against risks from bacterial infections, and the newly introduced intestinal nematode egg guideline was intended to protect against helminth infections (and also serve as indicator organisms for all of the large settlable pathogens, including amoebic cysts). The exposed group that each guideline was intended to protect and the wastewater treatment expected to achieve the required microbiological guideline were clearly stated. Waste stabilisation ponds were advocated as being both effective at the removal of pathogens and the most cost effective treatment technology in many circumstances [27].
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Table 2.4. The 1989 WHO guidelines for the use of treated wastewater in agriculture Category
Reuse conditions
Exposed group
Intestinal nematodes b (arithemetic mean no. per 100mLc)
Feacal coliforms (geometric mean no. per 100mLc)
Wastewater treatment expected to achieve the required microbiologica quality
A
Irrigation of crops likely to be eaten uncooked, sports fields, public parksd
Workers, consumers, public
1
1000d
B
Irrigation of cereal crops , industrial crops, fodder crops, pasture and treesc
Workers
1
No standard recommende
C
Localized irrigation of crops in category B if exposure of workers and the public does not occur
None
Not applicable
Not applicable
A series of stabilization ponds designed to achieve the microbiological quality indicated, or equivalent treatment Retention in stabilization ponds for 8-10 days or equivalent helminth and fecal coliform removal Pretreatment as required by the irrigation technology, but not less than primary sedimentation
a. In specific cases, local epidemiological, sociocultural and environmental factors should be taken into account and the guidelines modified accordingly. b. Ascaris and Trichuris species and hookworms. c. During the irrigation period. d. A more stringent guideline ( 200 faecal coliforms per 100 ml) is appropriate for public lawns, such as hotel lawns, with which the public may cone into direct contact. e. In the case of fruit trees, irrigation should cease two weeks before fruit is picket, and no fruit should be picked off the ground. Sprinkler irrigation should be used [27].
25
In Ethiopia, the standard for application of effluent to lands is given in Table 2.5. Table 2.5. Controlled application of effluent to lands Constituent group or
Emission limit value(mg/L)
parameter
pH
5.5 - 9 pH units
BOD5 at 20 oC
500
Chloride (as Cl)
1000
Sulphate (SO4)
1000
Source: Standards for Industrial pollution control in Ethiopia (2003)
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3. CLEANER PRODUCTION METHODOLOGY Initial check list was used to see the significance of Cleaner Production assessment in RSD. Then, based on methodology developed by UNEP and UNIDO the assessment is described, and consists of the following basic steps:
planning and organising the Cleaner Production assessment pre-assessment (gathering qualitative information about the organization and its activities)
assessment (gathering quantitative information about resource consumption and waste generation and generating Cleaner Production opportunities)
evaluation and feasibility assessment of Cleaner Production opportunities implementation of viable Cleaner Production opportunities and developing a plan for the continuation of Cleaner Production efforts.
3.1. Initial Checklist The following simple checklist was used in identifying initial Cleaner Production opportunities likely to lead to cost savings and increased profitability in RSD. 1. Does RSD provide services or manufacture goods which use:
energy water raw materials? 2. Are the costs of one or more of these a significant proportion of operating costs in RSD? 3. Does RSD generate solid, liquid, gaseous or chemical wastes? 4. Do any of the products manufactured in RSD become a ‘problem’ for disposal at the end of their life [10]?
For all the above questions, the answer was ‘yes’. Therefore, cleaner production is likely to lead to cost savings and increased profitability. The details of methods and materials were used to assess cleaner production opportunities in RSD are given below.
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3.2. Task 1: Planning and Organization This section includes obtaining management commitment, setting aims and establishing a proper project organization for conducting the Cleaner Production assessment [5]. At Repi Soap and Detergent S.Co the management was committed and ensured collaboration and participation. The arrangement for a Cleaner Clean er Production team set up was to identify, investigate and evaluate cleaner production options. A plan was aimed to include a cross-section of staff on the team, from major business functions such as manufacturing, purchasing, marketing, distribution, human resources, finance/accounting, and research and development. However, due to staff limitation, it was not possible to organize a team and yet almost everybody in the factory cooperated for the realization of the cleaner production assessment.
3.3. Task 2: Pre-Assessment Prior to the assessment a facility description, a process description, a process flow diagram, major energy consuming equipment, raw material information, and energy and waste data were collected in RSD. Collection of this data prior to the assessment gave an idea of where attention should be focused during the actual assessment [31]. 3.3.1. Company Description and Flow Diagrams
In this section the company was described along with flow diagrams for each one of the processes. Process description
The process description was a very important part of the information collection process as it provided the basic information needed to generate process flow diagrams and for opportunity analysis in RSD. The process description includes the following elements:
Description of the products produced (i.e., ROL, LARGO and AJAX) Brief list of raw materials (LABS, Sodium Hydoxide, Zeolite, Sodium Tripoly phosphate, Sodium Silicate, Soda ash, Sodium Sulphate, Sodium Chloride, SCMC, Triethanolamine, Photine, STS, Perfume and water ) and
Step-by-step description of unit operations from the beginning of the product manufacture following through to the finished product.
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Process flow diagram
The flow diagram for all processes in RSD was drawn by a series of block diagrams (chapter four) that visually visually describe the flow flow of materials. materials. For each block in the flow diagram, data including raw material input, waste stream output, utilities, products, and co-products were obtained.
3.3.2. Walk-Through Inspection During the walk-through in RSD, talking to several staff members, heads of production, technical and quality departments, and operators presented valuable information. Observations about the operations and general appearance of the facility (e.g., evidence of leaks and spills) were recorded. The following check-list was used for assessment during the walk-through:
Are there any drips, leaks or spills or emissions? Is all equipment operating properly at design capacity/efficiency? wa sted? Are energy, water or raw materials being wasted?
Are hazardous materials and wastes stored appropriately? Are different wastes kept separated? Are wastes necessary? Are there any opportunities for reuse or recycling on site?
Could any hazardous raw materials or consumables be substituted for less hazardous materials [10]?
It was necessary to return to the process as often as necessary to gather adequate data to develop a list of opportunities. From the pre-assessment in RSD: high fuel consumption at the spray tower per unit of product, boiler short-cycling due to over sizing, steam loss through steam traps, STPP being used u sed as raw material, wastewater from factory washing and toilet septic tank overflow being used for agricultural purpose were noted.
29
3.4. Task 3: Assessment This consists of the in-depth evaluation of the selected audit focuses in order to develop a comprehensive set of alternate Cleaner Production options in RSD. This required a quantification of the volume and composition of the various waste streams and emissions as well as a detailed understanding of the causes of these waste streams and emissions [5]. 3.4.1. Compiling Facility Data
Measurements, production log book, product quality control sheets, energy consumption records and interview with production and technical personnel were main sources for data compilation. Compiled data were used for material and energy balance of the whole process.
Spray dryer
During analysis on the air used for spray drying in RSD, it was taken that upstream (i.e. before the heaters) the mass flow rate was not modified when air was heated up to 283oC. This was due to opposite effects of temperature on pressure losses in the equipment, through decreased air density and viscosity and increased by the total cross section gave the velocity. Therefore, it was considered that the mass flow rate of dry air delivered by the fans was not significantly modified by temperature [32]. Speeds of air were measured by a digital anemometer at exhaust air pipe and tower base at ambient temperature. At the tower base, air flow rate was measured while all machineries were operating but no product was being discharged. This was done to avoid measuring disruption due to be caused by detergent powder. However, at the exhaust pipe measurement was taken while production was going on. Then, to determine the air flow rates at exhaust air outlet and tower base were measured with anemometer at 3 positions of the section of straight cylindrical ducts. The weighted average of velocities multiplied by the cross-sectional area gives the volume flowrates. Fifteen replications were performed.
A hygrometer and thermometer were used to measure the relative humidity and temperature of the air into and from the spray drier. The mass flow rate of concentrated slurry was calculated from the daily production mass and production hour taken.
30
Steam leaks
In RSD, steam trap of the steam header was one point where there was a continuous steam leaking. However, this point steam loss was substantial. Steam leaks at pipe fittings, valves and traps can result in substantial energy losses. Figure 3.1. indicates how to calculate the hourly loss from a steam leak by measuring the length of the steam plume, which is the distance from the leak to the point at which water condenses out of the steam [33].
Figure 3.1. Hourly steam loss from leaks as a function of steam plume length
Steam and electrical energy consumption
The electrical energy and steam consumption for sections and unit operations is estimated by recording the time of consumption and taking the design capacity of processes, motors and pumps [34].
31
The steam demand of a plant can be determined using a number of different methods: calculation, measurement and thermal rating [35].
The design steam demand (thermal rating) of the processes in RSD is not known. There was no steam flow meter measuring equipment either. Therefore, time take for steam consumption by the process was recorded; steam pressure and the size of the pipe the steam was passing through were identified. Then, a ‘steam pipe capacity table’ (Appendix 5) was used to estimate hourly steam consumption of the processes.
The total variable cost of raising steam (CG) in RSD was calculated using equation (3-2). Fuel cost is usually the dominant component, accounting for as much as 90% of the total. It is given by [36]:
Cf
af H h
.......................................... ………. (3-1)
Where:
af
fuel cost, $/kJ
H
enthalpy of steam, kJ/kg
h
enthalpy of boiler feed water, KJ/kg
overall boiler efficiency, fractional
Then the cost of raising steam:
CG = C f (1 + 0.3)………………………….….……. (3-2)
Heat loss from furnace surface
The quantity of heat loss from surface of furnace body is the sum of natural convection and thermal radiation. This quantity can be calculated from surface temperatures of furnace. The temperatures on furnace surface should be measured at as many points as possible, and their average should be used. If the number of measuring points is too small, the error becomes large.
32
For finding the temperature of the furnace wall temperature in RSD: the tip of the thermometer is placed to the outer wall of the furnace. It was made sure that the tip of the thermometer touches the furnace. Then it was waited a couple of minutes for the temperature to stabilize. Then the temperature was read when it stabilized. This was conducted fifteen times for each of the three spots on the surface (a total of 45 measurements). The average result was taken as furnace wall temperature (Appendix 4). The following Figure 3.2 shows the relation between the temperature of external wall surface and the quantity of heat release calculated with this formula.
Figure 3.2. Quantity of heat released at various temperatures Therefore from the above figure, the quantities of heat released from ceiling, sidewalls and hearth per unit area can be found [37].
33
Water flow rate measurement
Water and wastewater flow rates were measured by recording the time taken to fill a known volume of flask and in some cases by measuring the change in water level in a tanker with a known volume in a given time.
Water samples collection
Water in RSD was sampled to see its suitability for the environment and agriculture. Looking at the process in detergent industries, almost all the water used goes in a closed loop. However, faulty processes like it was in RSD generate wastewater at different points in different times. As there was no constant source of wastewater in the process, the mixture of different wastewaters in the factory were sampled three times in a judgmental sampling method. This factory wastewater in RSD was mixed with toilet wastewater overflowing from septic tank. From this mixture also three samples were taken. Hence, a total of six samples were taken for laboratory analysis and each analyzed for 16 parameters. The number of samples was limited by project funding. Judgmental sampling method was used for sampling wastewater.
Samples were collected in clean transparent plastic buckets after rinsing several times, first with hot and cold water and final thorough rinses with the actual wastewater being sampled. As the water flows in RSD were shallow, samples were collected by lowering plastic buckets to the bottom, opening and closing them there by hands, and taking out. The water samples after proper marking and labeling were taken to the Addis Ababa Environmental Protection Authority laboratory immediately for analysis to avoid any change or deterioration in its quality due to chemical and microbial activity. The time taken to transport the samples was 45 minutes. Samples were then analyzed immediately [38]. Wast water analysis
Due to economical constraints associated with project funding, a certain physical, chemical and biological quality parameters and number of samples were selected for the laundry (3 samples) and laundry and toilet mixture (3 samples) water analysis. These analyses included pH, electrical conductivity (EC), biochemical oxygen demand (BOD), chemical oxygen demand (COD), concentration of selected cations (Na, Ca, Mg and K), chloride(cl-), nutrients (total
34
nitrogen, phosphate, nitrate and nitrite), and faecal coliforms. As no heavy metal and boron were used in laundry water in RSD, the analysis on heavy metal and boron was not covered in this thesis. In order to evaluate the potential health hazard associated with laundry and toilet water reuse, faecal coliform analysis was used. Reagents and apparatus required for the analyses of each parameter for this particular study are presented in appendix 1.
Material and energy balance
Material and energy balances in RSD were calculated based on the conservation laws of mass and energy. Whenever possible direct measurements were made for both the material flow and energy flow, and then calculations were used to determine unknowns.
3.5. Task 4: Evaluation and Feasibility study A set of Cleaner Production options were obtained from previous stage of the assessment in RSD. Next, the technical, economic and environmental feasibility of the options were examined.
The feasibility analysis phase consists of three post-assessment activities: (1) prioritization of opportunities, (2) evaluation of technical and economic feasibility, and (3) generation of an assessment report [10].
3.5.1. Prioritization of Opportunities Because of time and resource constraints, most facilities have to set priorities among their energy conservation and pollution prevention options based on the original goals and criteria specific to the processes evaluated [31].
3.5.2. Evaluation of Technical, Economic and Environmental Feasibility Following the assessment in RSD it was necessary to evaluate the technical, economical and environmental feasibility of each energy conservation and pollution prevention options identified.
Technical evaluation
Technical evaluation in RSD included calculations of energy conservation or waste reduction and the associated costs, impacts on operations, and its advantages and disadvantages.
35
Additionally, the technical evaluation included evaluation of the implementation aspects of the option including such things as: is there room in the facility for new equipment and will the new process affect the quality of the product [31].
Economic evaluation
Economic feasibility compares current savings with costs of implementing the option. The likely payback period for any capital investment is often the simplest method for assessing economic feasibility.
The payback period is the time it will take to save the money spent to change or improve a process or operation, and is expressed as [10]:
Paybackper iod years
Capital investment and project cos ts Net savings in operating cos ts per year
….…………. (3-3)
Environmental evaluation
The objective of environmental evaluation is to determine the positive and negative impacts of the options for the environment [9]. Selection of feasible options
In RSD first, the technically non-feasible options and the options without a significant environmental benefit were to be eliminated. All remaining options can in principle be implemented. However, a selection is required in case of competing options or in case of limited funds [9].
Based on these considerations, the viable options were re-screened and priorities were set for implementation. Priorities were based on greatest return or urgency [10].
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3.6. Task 5: Implementation and Monitoring Management support is the most important element in successfully implementing Cleaner Production opportunities. Actions taken to implement energy conservation and pollution prevention projects vary greatly from project to project and company to company. One facility may decide to use in-house expertise to implement projects while another may find it beneficial to contract the work to an outside organization. After successful implementation of the project, it is beneficial to track and advertise the resulting cost savings and impacts to give feedback to facility personnel. This allows personnel to see the results of changes in procedures or installation of new equipment and to participate in the energy conservation and pollution prevention program [31]. The expected result of this phase is threefold: obtain 1. Implementation of the feasible Cleaner Production measures 2. Monitoring and evaluation of the progress achieved by the implementation of the feasible options 3. Initiation of ongoing Cleaner Production activities [9].
37
4. CLEANER PRODUCTION ASSESSMENT IN RSD The results obtained from the cleaner production assessment in RSD are described in this chapter.
4.1. Steps Taken for Cleaner Production Assessment in RSD In RSD, it was first realized that the company used chemical raw materials, water and energy in the course of producing detergents. It was also recognized that significant proportion of the cost was spent on energy and raw materials. The factory generated liquid waste and used raw materials like STPP that can be a problem for disposal. Therefore, it was believed that cleaner production could offer a great opportunity to reduce costs, improve the company’s environmental performance and increase profitability. Then based on the methodology developed by UNEP and UNIDO, the assessment in RSD was conducted. By recognizing the rewards of implementing cleaner production, the management in RSD expressed commitment to its realization. The management, however, did not officially organize a team. The management, instead, laid a level ground where every department could participate and contribute to its realization. At this stage, the objective was to:
Generate cleaner production options. Analyze cleaner production options generated in terms of technical feasibility, financial feasibility and environmental benefit.
Assess costs and benefits of switching from STPP to zeolite-based detergents. Therefore, at this stage in RSD the framework of the study was developed. At this third stage in RSD or the so called "pre-assessment stage" process description, facility description, process flow diagram, major energy consuming equipment (like spray dryer), raw material information, and energy and waste data were collected in RSD. Walk-through in the factory and company compound was important in this process. From these data of energy consumption, wastewater generation, raw material that can be a problem for disposal were observed and recorded for further assessment. Therefore, at this stage the focus of the study was decided.
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Fourth, in-depth assessment of energy, raw material and waste were undertaken to develop a comprehensive set of cleaner production options. Therefore, at this stage set of cleaner production options were prepared. Fifth, the technical, economic and environmental feasibility of the options were undertaken. This is explained in chapter five. The following are assessments in RSD from pre-assessment to assessment stage.
4.2. General Description of Repi Soap and Detergent S.Co Repi Soap and Detergent S. Co (RSD) is the oldest soap and detergent factory in Ethiopia. The factory is located in the west of Addis Ababa in Kolfe Keranio sub-city along Jimma road. The factory compound has an area of 28,384m2. The factory was first owned by six foreign citizens. It was commissioned and commenced production in 1967. It was confiscated and registered as government property when the Derg regime came to power in 1974. In 2006, the company was privatized and now owned by Alsam private limited company. RSD produces mainly detergents of different forms such as: ROL:
powder detergent for laundry
AJAX:
bar detergent for laundry
LARGO: liquid detergent for laundry. The powder plant operated below four months in a year mainly due to high production cost and lack of domestic market for its powder detergent products. Also, other major domestic detergent producers face the same challenge. ‘Zahara’ and ‘Aerial’ are among many imported powder detergents that enjoy the wider domestic market. However, RSD also produced bar and liquid detergents seven to eight months in a year. The factory enjoys wide domestic acceptance and market for its bar and liquid detergents. For this budget year 2008/9, it aims to produce 1500 tons powder, 3000 tons bar and 1200 tons liquid detergent. When seen in light of the volume of energy, manpower and number of machineries used, the powder detergent plant was the highest. The average production capacity of the plants in RSD was 0.58ton/h, 1.65ton/h and 0.60ton/h for powder, liquid and bar detergents respectively. Currently the factory has 150 total number of
39
manpower of which 40 are female. The factory used water well as service water source ever since it has become operational. Heavy fuel was used by boiler and furnace for steam and hot air production respectively. All other energy demands of the processes are electrical energy from the national grid. Wastewater from laboratory, factory floor washings, toilet (mixture of urine and feces), clothes washing and chemical leakage washings are all used for irrigation purpose to grow vegetables in the factory compound or directed to open storage pond that overflow on grassland in the factory compound. In RSD the raw materials that were used for powder liquid and bar detergents are listed in the table below (Table 4.1). The composition of each product in RSD was intentionally omitted to protect the company’s commercial secret, upon their request. Table 4.1. List of raw materials used for powder, liquid and bar detergents production in RSD Ingredients used for the production of: No.
Raw material
Powder detergent Liquid detergent
Bar detergent
1
LABS
2
Sodium hydroxide
3
Zeolite
4
STPP
5
Sodium silicate
6
Soda ash
7
Sodium sulphate
8
Sodium chloride
9
SCMC
10
Photine
11
STS
12
Monstral blue
13
Triethanol amine
14
Perfume
15
Water
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4.3. Process Description and Process Flow Diagram for Powder Detergent Production This section contains a brief process description and process flow diagram for powder detergent (ROL) production in RSD. Figure 4.1 shows the general flow diagram for powder detergent production in RSD.
Hot air
Cyclones
NaOH solution Water
LABS Dust Neutralizer Spray drier
Solid raw materials
Pneumatic conveyor for cooling and dust separation
Dust
Paste
Mixing vessel (slurry)
Powder
Sieve
Perfume dosing
Slurry Storage
Hot air Figure 4.1. Flow Diagram of powder detergent Production in RSD
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4.3.1. Slurry Preparation Electricity
Electricity
Electricity
Water
NaOH
LABS
Paste preparation (Reactor)
Electricity
Paste
Water for washing
Spillages from sieve
LABS
Water pumping
NaOH pumping
Electricity
Slurry preparation
Chemical ingredients (Solids)
Spillages Slurry
Wastewater Ageing tank
Slurry to spray drier Figure 4.2. Flow diagram for slurry preparation
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Electricity
4.3.2. Slurry Filtration and Pumping
Slurry from ageing tank
Electricity
Slurry bleeding
Filter (lumps and solids)
Circulating cooling water
Washing water
Leakage
Cooling water leakage Electricity
Centrifugal pump
Waste water Cooling water leakage
Cooling water Electricity Cooling water
Reciprocating pump Slurry to spray tower
Figure 4.3. Flow diagram for filtration and pumping of slurry
In RSD, Sodium hydroxide, LABS and water were mixed in a reactor to produce paste. These raw materials were first made ready in overhead tankers by pumping. However, LABS was not pumped because of its corrosive nature. Instead, it was hoisted in a container then poured down to an over head tanker. The paste was then put into a reactor where it was mixed with soda ash, sodium sulfate, sodium-tri-poly-phosphate, zeolite, sodium chloride, sodium tolune, optical brighteners, sodium carboxyl methyl cellulose and sodium silicate. Then it was sent to ageing tank through a simple open sieve where there usually occurred spillage. The ageing process enables to finalize reaction.
43
Slurry in RSD was filtered to prevent clogging of the atomizing nozzles in the spray dryer. Electro mechanical sieve was used for this purpose. Because of high pressure development in this filter, slurry bleeding through hinges and joints was usually observed. This was washed with water.
After filtering the slurry, centrifugal pump was used for homogenizing the slurry. This pump also conditioned the head for the following high pressure reciprocating pump. The working load on the reciprocating pump was controlled by a pressure gauge. The change in pressure usually tells the amount of slurry entering into the spray dryer. Therefore it was used to control drying process. Water used for cooling both pumps was leaking continuously.
In RSD, furnace is used to heat ambient air. The air from the furnace was induced countercurrently by a fan in to the spray dryer. The air in the tower, after drying the slurry, was exhausted by a fan. Before this hot air was released into the open air, ten cyclones were used to remove the dust with the air. The dried product is collected by belt conveyor at the base of the tower. This powder was conveyed to an air lift where it was cooled in due course. This powder was lifted to the fifth floor of the building by the air lift where dust is separated by a cyclone. During its journey back to the first floor, the powder was perfumed and stored in open buggies on the first floor. From these buggies, powder was transferred by gravity to the packing machine.
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4.3.3. Slurry Drying and Powder Storage Electricity for scraper
Exhaust air and dust Air 10 cyclones (Each five in parallel)
Spray drier
Hot air Cold air
Electricity Power detergent
Air
Dust collection Electricity
Air lift
Air Electricity
Cyclone Dust collection
Electricity
Vibrating sieve Coarse product
Electricity
Perfume dozing
Perfume
Powder detergent to temporary storage buggies
Figure 4.4.
Flow diagram for processes from slurry drying and powder storage
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4.3.4. Hot Air and Steam Production Electricity Steam
Steam
Hot water
Deareator Water
Electricity
Boiler
Heavy fuel Heavy fuel
Steam blow down
Heavy fuel
Electricity Hot air
Steam
Furnace Heavy fuel Air
Electricity
Hot air Hot air induce fan
Electricity
Figure 4.5. Flow diagram for hot air and steam production
In RSD the furnace and boiler used heavy fuel and electrical energy. Boiler feed water was heated by direct steam in un-insulated deareator. The boiler burner was observed to experience short-cycling. The furnace outer surface was un-insulated while the inside part was insulated with fire brick. Heavy fuel used by both the boiler and furnace was heated by steam in a coil inside a tanker.
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4.4. Process Description and Flow Diagram for Liquid Detergent Production
Water
Active matter Reactor
Chemical ingredients
Electricity Liquid detergent (Largo) Largo manual packing
Washing water Leakage
Trickling Largo Wastewater
Packed Largo to Store Figure 4.6. Flow diagram for Largo (Liquid detergent) Production
All raw materials were mixed in a reactor to produce liquid detergent. The packing was done in jerrycans manually. The meager leakage on each of the jerrycans was washed with water by collecting all the jerrycans together after each batch. This water contributes to the amount of wastewater in the factory.
47
4.5. Process Description and Flow Diagram for Bar Detergent Production Water
LABS Chemical ingredients
Sigma mixer Electricity Mixture to milling Electricity Circulating cooling water
Cooling water
Circulating cooling water
Cooling water
Miller (3 rollers)
Mixture to plodder Plodder (double screw)
Electricity
Cutter
Bar detergent to Store
Electricity
Figure 4.7. Flow diagram for Ajax (bar detergent) production
In RSD for bar detergent (AJAX) production the raw materials were first mixed in sigma mixer. This was then milled by a miller with three rollers. This served the purpose of homogenizing. Then, it was allowed to pass through a duplex plodder. Finally, it was cut and packed.
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4.6. Material and Energy Balance A material balance taken over the complete process will determine the quantities of raw materials required and products produced. Balances over individual process units set the process stream flows and compositions. Material balances are also useful tools for the study of plant operation and trouble shooting. They can be used to check performance against design, to extend the often limited data available from the plant instrumentation, to check instrument calibrations, and to locate sources of material loss.
In process design, energy balances are made to determine the energy requirements of the process: the heating, cooling and power required. In plant operation, an energy balance (energy audit) on the plant will show the pattern of energy usage, and suggest areas for conservation and savings [39]. In order to do these balances for RSD not many problems were faced with data collection and acquisition for the material balance. In addition to material balance data collected, production log book and quality control data sheets were used as a source of data.
Water and wastewater flow rates were measured by recording the time taken to fill a flask with known volume or the change in water level in a tanker of known volume in a given time. Fuel consumption by the boiler and furnace are measured by taking changes in fuel level in the tankers with in a given time.
The reciprocating slurry pump, boiler and steam header were the only ones that had pressure measuring devices. Temperature sensors were put in place for induced hot air to the spray tower and exhausted air from the spray tower. Complete energy balance could not be conducted using measurements collected from these devices alone. Therefore thermometer was used whenever necessary to measure process temperature and hygrometer was used to measure humidity changes in the process. Also, anemometer was used to measure the speed of air to and from the spray tower and then air flow rate was calculated from speed of air and pipe cross sectional area. Steam pipe capacity table (Appendix 5) was used to estimate the steam consumption of each process section as there was no steam measuring instrument for flow rate. Steam produced by the
49
boiler is used to heat heavy fuel to be used by furnace and boiler, to heat boiler feed water in the dearator, during slurry preparation and pipe line washing to prevent clogging.
The electrical energy consumed in the different sections are used by stirrer motors, pump motors, fan motors, spray tower scraper motor, conveyor belt motor, air lift motor, sieve motor, folding and packing machine drive motor, air compressor motor, mixer motor, duplex plodder motor and cutter motor. The production hours for powder, liquid and bar detergents were calculated from their respective existing production capacity.
Boiler in Repi Soap and Detergent S.Co had a design capacity of 1ton/h at 12 bar. As there was no process steam load estimating means, a new water flow meter device was bought and fixed right before boiler feed water tanker. Then, the steam load of the process was determined by using the water flow meter, considering the amount of all water fed to the boiler was converted into steam. From 15 days data it was found out that the steam produced was 0..106ton/h at 7 bar on average (Appendix 4).
To estimate steam loss from the steam header fig 3.1 was used. And Q = mc pT was used to estimate the steam consumption and loss from deareator.
Most of the service water used in RSD was consumed directly by the process. Wastewater generations in the process were related mainly to floor washings, Largo jerrycans and spillages washings, laboratory wastewater, canteen wastewater, clothes washings, slurry and chemical leakage cleanings. The mixture of these wastewaters was again mixed with toilet wastewater in the factory compound and it was used for salad and cabbage irrigation purpose in the factory compound.
4.6.1. Powder Detergent (ROL) Production Quantitative Data Raw material transfer to storage tanks for paste preparation
All water in RSD was pumped ground water from an area near the factory compound. This had been done since the company became operational and that is for more than three decades. After
50
the water was pumped, it was stored in three tankers that contain a total of 30m 3. From here water was again pumped to two overhead tankers from which to be used for all processes.
At this stage of the process, solid NaOH in a metal barrel was diluted with water to 36% by weight solution in a tanker on the ground. Since the reaction is exothermic no mixing is used to assist solution formation. Then, it was pumped to a storage tanker on the first floor to be used for paste preparation.
LABS in plastic barrels were lifted up to second floor using hoisting machine. It was, then, poured empty to a tanker on the first floor to be used for paste preparation. While filling up tankers on the first floor with LABS, caustic soda and water, they overflowed once in a while. This same floor is also used for temporary storage of powder in buggies until it can be packed. In the course of this storage, powder dusts fall on the floor dispersedly. Therefore, water was used to wash both dispersed powder dusts and overflowed chemicals.
Electrical energy was used in this section for:
caustic soda pumping, water pumping and
hoisting LABS.
Paste preparation
In RSD paste was prepared on a tower above the ground floor in a jacketed rector with an agitator. The reactor had neither temperature sensor nor pressure gauge. Thermometer was used to measure the temperature of the paste for this study. As most of the operators had decades of experience on this section, no major discrepancy was observed in product quality. However, the production procedure was open for product variation. For this section LABS, water and NaOH were used from 1st floor, all flowing down by gravity. Paste preparation in Repi Soap and Detergent is prepared at a temperature of 62OC. Each mole of LABS and 36% concentrated NaOH was allowed to under go neutralization reaction in the reactor. During this neutralization process, 1 mole of water created for each mole of reaction taken place stochiometrically. Water is added to make the solution 50% concentrated.
51
The moisture content and pH of the paste was checked in laboratory every production hour by shift chemists and recorded on quality control sheet. This showed on average a moisture content of 51% and pH of 8.1.
Every batch of the paste produced was pumped to slurry preparation reactor on the second floor. Steam from ¾ inch pipe was used in this process for pipe line clearing for three minutes after each batch paste was pumped for three minutes. Washing pipe lines after each batch paste pumping avoids pipe line clogging as paste tends to solidify quite easily.
In
this
section
electrical
energy
is
used
by
motors
for
hoisting,
mixing
and
pumping.
Qam1= 382.37 ton/yr
Qsp1 = 12.04 ton/yr
Qwp 1 = 284.46 ton/yr
Paste preparation Ep1 = 42,296.83 kwh/yr
Qp1 = 764.74 ton/yr Figure 4.8. Flow diagram for paste preparation Where: Qam1 Qwp1 Qsp1 Qp1 Ep1
Active matter Water Steam Paste Electrical energy input
Raw material transfer for slurry preparation
In RSD the paste prepared had been pumped to second floor where the slurry was prepared. All solid ingredients, all in sacks, were hoisted to second floor using an electromechanical hook. The
52
solid ingredients are zeolite, STPP, sodium sulphate, sodium chloride, SCMC, photine and STS. Water from overhead tanker was also used to make the slurry 59% concentrated.
Qp1 = 764.74 ton/yr Qs1 = 1,261.95 ton/yr Slurry Preparation
Qss1 = 49.50 ton/yr
Qws1 = 455.11 ton/yr
Es1 = 45,795.84 kwh/yr
Qs1 = 2,786.97 ton/yr Figure 4.9. Flow diagram for slurry preparation Where: Qp1 Qs1 Qws1 Es1 Qss1 Qs1
Paste Solid ingredients Water Electrical energy input Steam Slurry
In the course of slurry preparation, 7 bar steam was directly injected for 10 minutes. This was repeated for each batch through a ¾ inch pipe. Each slurry preparation batch takes 20 minutes. The reactor was jacketed and had agitator. Steam was also applied for 3 minutes to clear pipeline after sending down slurry to ageing tank which was on ground floor. Neither pressure nor temperature sensors were put in place here. Variation of product quality is inevitable, no matter how well experienced the operators were. The slurry was kept in ageing tanks with continous gentle agitators for completing reaction. For ten minutes, twice in a day the pipe lines were washed thoroughly with steam.
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Electrical energy was used by motors for preparing the slurry and ageing it by gentle agitation. The slurry was prepared on third floor while the ageing tank was on ground floor. Therefore no pump was used.
Filtration and pumping of slurry
The slurry from ageing tank was filtered in a closed sieve with an agitator, on its way to the spray tower. The agitator facilitates filtration and prevents sieve clogging. This filtration helped to avoid lumps and solid materials, which if not filtered could block atomizer nozzle orifice and disrupt regular production procedure. The filter was followed by a homogenizing centrifugal pump and then by a high pressure reciprocating pump. High pressure was developed in side the sieve because of the pumps. This high pressure caused slurry bleeding from joints and hinges of the filter. Water was used to wash the bleedings.
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Qs1 = 2,786.97 ton/yr Qww1 = 1,144.25 ton/yr Ef 1 = 1,929.6 kwh/yr
Sieve filter (Electro mechanical)
Qwf 3 = 17.37 ton/yr
Eh1= 56,601.6 kwh/yr
Homogenizing pump (Centrifugal pump) Leakage
Qwf 1= 450.75 ton/yr
Er 1= 47,725.44 kwh/yr
Qwf 2 = 676.13 ton/yr High pressure (reciprocating) pump
Qs1
Figure 4.10.
Flow diagram for filtration and pumping of slurry
Where: Qs1 Slurry Ef 1 Electrical energy input to filter motor Eh1 Electrical energy input to homogenizer pump motor Er 1 Electrical energy input to high pressure pump motor Qwf 1 Cooling water leakage from homogenizer pump Qwf 2 Cooling water leakage from high pressure pump Qwf 3 Water used for floor washing Qww1 Wastewater generated The homogenizer pump mixed the slurry well after filtration. It also conditioned the slurry for the high pressure reciprocating pump by providing suction pressure. Pressure gauge is installed
55
for the high pressure pump. It was normally expected to run at 8 bar. The high pressure pump working pressure determined the quality of atomization, quantity of slurry sprayed, product bulk density and exhaust air temperature and moisture.
Cooling water from the same tanker was used for both pumps. Part of this cooling water leaked continuously because the amount of cooling water used was more than required. This leaking water was mixed with slurry escaping through piston clearance of the reciprocating pump. As a result the water created foaming. Here the amount of water leaked was measured using the change in water level in the tanker in a given time.
Electrical energy is used by motors for filter, homogenizing centrifugal pump and high pressure reciprocating pump.
Spray drying
The spray dryer in RSD was a countercurrent spray dryer and had a plate capacity of 1 ton per hour. However, actual daily production for a month was 0.583 ton per hour. From measurements of fuel level in tanker, 0.194 m3 of heavy fuel used to produce 1 ton of powder. The dryer had 4 nozzles of which only two were used at most. When more than two nozzles were used, distinctively wet product is produced. This accounted mainly for old, rarely inspected, misaligned and worn nozzles to say the least. The amount of heat contained in the hot air and moisture content of the slurry also contributed to it significantly. The dryer has a scraper which was initiated periodically to remove dried slurry on the sidewall of the dryer. These scraps contaminated product and increased the volume of rework. The volume of scraped product increases with disorder in any of the nozzles, hot air or slurry. Under this working condition with two nozzles, the product is dried as low as 3 % moisture content. This is uneconomical for a product that was packed at 10 % anyway. Hot air of 12,844.04 m3/h at a temperature of 283OC from furnace is induced by a fan to the lower part of the dryer and 13,810.80 m3/h air at a temperature of 118OC is exhausted by an exhaust fan. The exhaust air is cleaned by ten cyclones, five of which were in parallel. Since the dryer is under depression (300 Pa), 966.76 m3/h of cold air is drawn in from the base of the dryer
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which was normally product out let. The speed of exhaust air and cold air drawn in were measured using anemometer. Then air flow rate in both cases were calculated from the crosssectional area of openings and speed of the air. Temperature sensors for induced and exhausted air were put in place. Therefore, one month data was taken and the average was calculated. The product was at a temperature of 82OC at the time it emerged out from the base of the dryer. It was then transferred to the air lift for cooling and cleaning by conveyor belt. As packing the product at 3% moisture content was uneconomical, it was kept in open buggies to take advantage of its hygroscopic nature. In this process, the product reaches 10 % moisture content.
Air lift and cleaning
The temperature of the powder from the spray dryer was cooled down to 35OC by the air lift and during flowing down all the way to the storage buggies. The air lift was on the fourth floor of the building. Therefore the air from the air lift is separated on the fourth floor by a cyclone. Then coarse powder was separated by vibrating sieve on the third floor. Finally the cleaned powder was perfumed on the second floor and stored in open buggies on first floor and remains absorbing moisture from ambient air up to the time of packing.
Electrical energy was used by motors for fans, vibrating sieve, and perfume doser.
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Qpr 1 = 1,586.68 ton/yr Ea1 = 58,531.2 kwh/yr
Qpd3 = 50.76 ton/yr Qpd2 = 52.66 ton/yr
Air lift
Qpc1 = 9.84 ton/yr
Qpr 2 = 1,524.18 ton/yr
Qpd4 = 1.9 ton/yr
Vibrating sieve
Evs1 = 7,666.94 kwh/yr
Cyclone
Qpc2 = 24.27 ton/yr
Qpr 3 = 1,499.91ton/yr Perfume dosing
Ed1 = 11,577.6 kwh/yr
Qp2 = 0.09ton/yr
Qpr 4 = 1,500 ton/yr Qm1 = 105.00ton/yr
Storage buggy
Qpr 5 = 1,605 ton/yr Figure 4.11. Flow diagram for air lift and cleaning Where: Qpr 1 Ea1 Qpr 2 Qpd2 Qpc1 Qpd3 Qpd4 Evs1 Qpc2 Qpr 3 Ed1 Qp2 Qpr 4 Qm1 Qpr 5
Powder Electrical energy input to air lift Powder from the air lift Air loaded with dust to cyclone Coarse product from the air lift Air from cyclone loaded with dust Collected dust from cyclone Electrical energy input to vibrating motor Coarse product from sieve Powder from sieve Electrical energy input to perfume dosing motor Perfume Perfumed powder Moisture absorbed by the powder during storage Powder to packing
58
Packing
Folding and packing machines were used for powder packing with carton. The folding machine, with a capacity of 3,000 pieces per hour, made the carton ready for the packing machine. The packing machine had a capacity of two cartons holding fifty gram per second. Electrical energy was used for both. Qc1 = 32.1x10 6 cartons/yr
Ef 2 = 26,666.88 kwh/yr
Folding machine
Packing machine
Qpr 5 = 1,605.00 ton/yr
Epm1 = 65,300.52 kwh/yr
Packed product to store
Figure 4.12. Flow diagram for packing Where: Qc1 Ef 2 Qpr 5 Epm1
Cartons Electrical energy input to driving motor (folding machine) Powder to packing Electrical energy input to driving motor (packing machine)
Furnace (hot air preparation)
In RSD heavy fuel, heated by steam to 34OC in fuel tanker, was pumped to heater attached to the burner. Here the heavy fuel is heated to 50OC. Ambient air was drawn in to the furnace by an induce fan and this same fan was used to induce hot air into the spray dryer. The temperature of the hot air produced was on average 283OC. The furnace outer wall was not insulated and on average the outer wall temperature was 102OC (Appendix 5). Electrical energy was used by the burner and pump motor.
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Qhf 1 = 291.19 m 3/yr Ehf 1 = 1,470.78kwh/yr
Qsf 1 = 108.59 ton/yr Heavy fuel Qaf 1 = 39,323.72 ton/yr Qhf 1
Furnace Ef2 = 90,562.56kwh/yr Qaf 1 Figure 4.13. Flow diagram for furnace (hot air preparation) Where: Qhf 1 Ehf 1 Qsf 1 Ef 2 Qaf 1
Heavy fuel Electrical energy input to pump fuel Steam Electrical energy input to the furnace Air
Boiler
The boiler in RSD had design capacity of 1ton per hour of 12 bar steam. Thermostat is used to heat fuel from 23 O C to 48 O C in two stages in fuel tanker and burner. Water at 23 O C in deareator is heated by direct steam injection. Hot water at 67 O C from deareator was used as feed water. It was observed that there was burner short cycling which is one of the main symptoms for an oversized boiler. To find out the scale of over sizing and to determine the extent of process load on the boiler, steam consumption of the process had to be first known. To measure steam load of the process was difficult because there was no single steam flow meter in the factory. Therefore, water flow meter was fixed before boiler water feed tanker (deareator). And it was taken that the amount of water used by the boiler to be equal to the amount of steam produced. By taking fifteen days data the process load of the process was found out to be 0.106ton/h including blown down steam. (Appendix 5)
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At this stage steam was used to heat boiler feed water. Electrical energy was used by the burner, to pump water to deareator, to pump fuel to tanker in the boiler room, to heat fuel by thermostat and to feed hot water to the boiler. Qw8 = 242.50 m 3/yr
Qsd = 31.52 ton/yr
Qsh2 = 172.91 ton/yr
Boiler feed water tanker (deaerator)
Steam Header Qhw = 274.03 m3/yr
Qsh1 = 46.31 ton/yr
Qsh1 = 7.19 ton/yr
Qhf 2 = 19.29 m3/yr
Qts = 219.22 ton/yr
Heavy fuel tanker
Ehf 1 = 156.75 kwh/yr
Boiler Qhf2 Eb = 1,418.64 kwh/yr
Figure 4.14. Flow diagram for boiler Where: Qw8 Qsd Qhw Qsh1 Qts Ehf 1 Qsh1 Qsh2 Qbd Eb Qhf 2
Water Steam for water heating Hot water to boiler Steam for fuel heating Total steam produced Electrical energy input for pumping Steam loss through header steam trap Steam to the process Steam blow down Electrical energy input to boiler Heavy fuel
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Qbd = 18.87 ton/yr
4.6.2. Liquid Detergent (Largo) Production Quantitative Data In RSD, on the second floor of the building, liquid detergent is produced in a reactor with a gentle mixer. Water flowmeter was used to know the volume of water added. The other ingredients were weighed by a balance. Every batch was 1.65 ton and it took an hour to prepare it. Which means 24 batches could be produced in a day. However, only three batches were produced in a day. Although the company claimed to enjoy wide domestic market for its liquid detergent product, it uses only 12.5% of its nominal capacity.
The liquid detergent after produced on the second floor flew down by gravity to ground floor where it was packed manually in jerrycans. During manual packing, a little bit of largo was wasted on each of the jerrycans. The jerrycans filled and packed were collected and washed for each batch. The jerrycans were then dried, labeled and taken to store by a fork lift lorry. 88.34 m3 of water was used per year to wash jerrycans.
Electrical energy is used by mixer motor. Qw2 = 909.81 m3/yr
Qbs = 290,185.23 ton/yr
Em1 = 2,167.26 kwh/yr
Mixer
QL1 = 1,200.00 ton/yr Largo manual packing
Largo to packing Figure 4.15. Flow diagram for Largo production Where: Qw2 Qbs Em1 QL1
Water Solid ingredients Electrical energy input Liquid detergent (Largo) ready for packing
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4.6.3. Bar Detergent (Ajax) Production Quantitative Data
In RSD all liquid and solid raw materials transferred manually were well mixed in a sigma mixer. Then it was manually transferred to a miller, and a duplex plodder. Then it was allowed to pass through a cutter. Finally the product was packed and taken to store by a lorry.
The amount of water used for cooling was determined by measuring change in water level in a give time. This circulating water was stored on a tanker on the ground and then pumped to overhead tanker from which cooling water was used by the miller and plodder. Electrical energy was used by motors for mixer, miller, plodder, cutter and cooling water pump.
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EmL = 437.50ton/yr
Qw10 = 235 m 3/yr
Em2 = 37,494 kwh/yr Sigma mixer Qbs2 = 2,765 ton/yr Qbs3 = 3,000 ton/yr
Em3 = 109,982.40 kwh/yr
Qw11 = 3,600 m 3/yr
Miller Qw11 Qbs4
EpL = 47,992.32 kwh/yr
Ecc = 24,996 kwh/yr
Plodder Cutter Qw12 = 3,600.00 ton/yr 3,000 ton/yr packed product to store
Qw12
Figure 4.16. Flow diagram for bar detergent (Ajax) production Where: Em Qw10 Em2 Qbs2 Qbs3 Em3 Qw11 Qbs4 EpL Qw12 Ecc
LABS Water Electrical energy input to mixer motor Solid ingredients input Mixture to miller Electrical energy input to miller motor Circulating cooling water for miller Mixture to plodder Electrical energy input to screw drive motor Circulating cooling water for plodder Electrical energy input for cutter drive motor
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4.6.4. Summary of Results
The total raw materials used in RSD for powder, bar and liquid detergent production to produce 1500 ton powder, 3000 ton bar and 1200 ton liquid detergents is listed below in table 4.2.
Table 4.2. List of raw material to be used for powder, bar and liquid detergents No
Raw material used
Amount (ton/yr)
1
LABS
1,024.79
2
Sodium Hydroxide (36%)
147.17
3
Zeolite
438.41
4
STPP
268.86
5
Sodium Sulphate
1,229.41
6
Sodium Carbonate
1,167.71
7
Sodium Silicate
503.78
8
Sodium Chloride
46.82
9
SCMC
30.58
10
Photine
3.87
11
STS
23.72
12
Monstral Blue
2.50
13
Triethaloamine
10.91
14
Perfume
12.27
15
Water
1,884.38 Total
6,795.18
65
Electrical energy and fuel required to produce detergents using the raw materials given above are listed below in Table 4.3.
Table 4.3. Electrical energy and fuel consumption
No
Unit Operation/ Section
Electrical energy
Heavy fuel
consumption
consumption
(kwh/yr)
(m3/yr)
1
Paste preparation unit
42,296.83
2
Slurry preparation unit
45,795.84
3
Slurry filtration and pumping
106,256.64
4
Spray drying unit
101,625.60
5
Section of air lift
77,775.74
6
Hot air generator unit
92,033.34
291.19
7
Boiler unit
1,575.39
19.29
8
Folding machine
26,666.88
9
Packing machine
65,300.52
10
Bar detergent unit
231,662.93
11
Liquid detergent unit
2,167.26
12
Lighting
15,284.55 Total
808,441.52
310.48
In RSD both bar and liquid detergents did not use steam. In table 4.4, steam consumed and wasted by the processes of powder detergent production is given.
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Table 4.4. Steam consumed and wasted by the processes No.
Unit operation and/or section
Steam consumption (ton/yr)
Steam wasted (ton/yr)
Total steam taken (ton/yr)
1
Heavy fuel heating
115.78
115.78
2
Paste preparation
12.04
12.04
3
49.50
49.50
4
Slurry preparation Deareator ( boiler feed water heater)
5 6
Steam header Boiler blow down Total
25.00
6.53
31.53
46.31 18.87
46.31 18.87
202.32
71.71
Remark Steam was used to heat the fuel. Direct steam was used for pipe line washing Direct steam was injected on the slurry. The loss accounted for un-insulated heater Steam trap fixed to the header has failed.
274.02
Service water used by the powder, liquid and bar detergent production is given in table 4.5 and wastewater generated by the processes is presented in table 4.6 consecutively. Table 4.5. Service water used in the processes No.
Unit operation/section
1
Paste preparation
2 3
Slurry preparation Liquid detergent (Largo preparation) Bar detergent (Ajax preparation) Total
4
Service water used (m3/yr) 284.46 455.11 909.82 235.00 1,884.39
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Remark This includes water for caustic soda dilution. The slurry was 41% water 727.27 batches and 1252 kg water per batch 12500 batches and 18.8kg water per batch
Table 4.6. Wastewater generated in the process No.
Section
Wastewater generated, m3/yr 88.34
1
Largo jerrycans washing
2
Cooling water leakage slurry pumps Water used to wash spillage from slurry filter and chemical overflow (1st floor) Toilet waste water Laboratory
1,126.89
Slurry filter leakage, pipe line washing spillage, powder dust blowing (ground floor) Boiler blow down Clothes washing Canteen washings Total
17.36
3
4 5
6
7 8 9
6.00
3,784.32 255.13
Remark During manual packing Largo flows over jerrycan body Cooling water amount was not optimized. Most of the time the place is kept untidy and stagnant water lying over the floor.
24 tests each about 5 minutes lab materials washing – not mentioning hand washing (each hand washing takes sometime because of foaming) Every day washing of spillages, leakages and powder dust on the ground.
18.87 596.84 86.40 5,980.168
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5. DISCUSSION In chapter four, the Cleaner Production opportunity assessment in RSD has gone through steps from initial check list to assessment stage. Therefore, upto this stage a set of cleaner production options were investigated. Hence, in this chapter the technical, financial and environmental feasibility of the cleaner production options will be dealt with.
5.1. Good Housekeeping and Staff Training In RSD ‘Good Housekeeping’ and ‘Input substitution’ can be undertaken to improve productivity, obtain cost savings, and reduce the environmental impact of operations. The adoption of ‘Good Housekeeping’ practices does not require major investments in cleaner technologies. This can be achieved by: changing Organizational Culture, creating Problem – Awareness, Information Dissemination and taking Simple Actions Such as rational use of resources and optimizing production processes [55].
5.2. Heavy Fuel Loss In RSD 310.50m3 fuel was used by the furnace and boiler. The furnace consumed 93.79% of the total fuel used in the factory.
5.2.1. Furnace The efficiency of furnace was determined by using the total heat in put from the fuel and the heat supplied to heat air from 23 O C to 283OC. From this calculation, in RSD the furnace was 49.60% efficient. This implied loss of 146.77 m3 of fuel per year. This amounts to birr 1,083,161.42 per year. The losses accounted for: heat loss due to evaporation of moisture present in fuel, loss due to evaporation of water formed due to hydrogen in fuel, heat loss through openings and doors, radiation heat loss from surface of furnace, heat storage loss, loss of furnace gases around charging door and opening, heat loss by incomplete combustion, loss of heat by conduction through hearth, and loss due to formation of scales. Among the many losses heat loss from furnace surface can be prevented by insulating the furnace. The total heat loss from furnace surface was 186,330.58 MJ/yr. The cost of furnace insulation with fibreglass is 130 birr/m2. The total surface area of the furnace is 19.22 m2. Hence, the total insulation cost would be birr 2,498.18. Equation (5-1) and (5-2) were used for calculating heat loss from furnace with
69
insulation and with out insulation respectively
[40].
From the calculations, insulation would save
161,135.50 MJ/yr. This equals 4.05 m3 heavy fuel per year (birr 29,872.90 per year). The payback period would be 0.08 year. Moreover, by insulating the duct to the spray tower and induce fan birr 25,359.73 can be saved per year with a payback period of 0.07 year.
q
2 L T i T
1 r i 1 ln k r o r i h
………………………………………… (5-1)
q = 2rh (Ti – T o)…………………………………………….. (5-2)
Where:
L
Furnace length
Ti
Furnace wall temperture
T
Ambient air temperature
To
Ambient air temperature
r o
Furnace outer diameter with insulation
r = r i
Furnace outer diameter with out insulation
k
Thermal vonductivity
h
Convective heat transfer coefficient
5.2.2. Spray Dryer The spray dryer in RSD was well insulated. It used a hot air from furnace that consumed 93.79% of the total fuel used in the factory. Hence, energy optimization at this unit operation was important. Fifteen days wall temperature measurement with thermometer showed that the temperature was 42OC on average. And from temperature sensors, induced and exhausted air temperatures were 283 OC and 118 O C on average repectively. From measurements made by anemometer and pipe area calculation, the cold air (23 O C) drawn in from the base of the tower was 7% of the total gas. It is convenient to consider that the total mass of gas drawn through the tower and to allow for the cold portion in assessing the corrected, inlet temperature, tc. tc = (0.93 x 283) + (0.07 x 23) = 264.8 O C
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The quantity of heat supplied in the furnace to heat 93% of the gas from 23 O C to 283 O C is the same as that which would be required to heat 100% of the gas from 23 O C to 264.8 O C.
From the wall temperature and corrected temperature of the hot gas, the lagging efficiency of the tower was 92.14%. Hence, the final exhaust temperature of the tower under adiabatic condition becomes 128 O C instead of 118OC.
283O C 42O C 283O C 23O C
100 % 92.14%
The heat supplied for various values of tc equals mass of gas x specific heat of gas x (tc-23). The heat used to achieve drying equals mass of gas x specific heat of gas x (tc -128).
[14] Therefore,
with a tc of 264.8 O C, the thermal efficiency of RSD equaled 56.58%. This means, out of all the fuel spent only 56.58% is used to drying the slurry. The effective amount of fuel (losses deducted) used by furnace was 140.62m3 per year. Hence, the amount of fuel loss was 61.06m 3 per year. This loss amounts to 450,594.19birr/yr. By increasing the thermal efficiency, the amount of fuel used to dry same amount of slurry can be decreased.
Table 5.1. Thermal efficiencies for various possible hot gas temperatures in RSD Inlet gas temperature, O C 450 400 350 300 283 250 200
Gas temperature (after admixture with 7% cold air at 23 O C), tc 420.11 373.61 327.11 280.61 264.80 234.11 187.61
Thermal efficiency t C 128
73.56 70.05 65.47 59.24 56.58 50.26 36.21
t C 23
Thermal efficiency t C 100
t C 23
80.61 78.04 74.68 70.11 68.15 63.53 53.22
From the above analysis, the energy loss was so big that optimization of energy utilization was a necessity. Efficiency in RSD can be improved widening the gap between inlet and outlet temperatures. This reduces the specific energy consumption of the process. This is because a smaller mass of gas is required to achieve a given amount of drying; and this gas, which leaves at
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a temperature substantially independent of the inlet temperature, carries with it less heat than mass of gas used when the inlet temperature is lower. Inlet temperatures of hot air can be raised to 400OC and outlet temperature can be lowered as low as 90-100OC [14, 15, 41]. Therefore, from table 5.1, the thermal efficiency can be improved in RSD simply by increasing the inlet temperature (by optimizing the air volume and correcting nozzle spraying) up to 350 O C and decreasing the outlet temperature down to 100 O C. This yields 74.68% thermal efficiency. Therefore saves 25.45 m3 liters fuel oil per year or 187,834.04 birr per year.
Table 5.2. Parts water evaporated to produce a part of powder Water content of slurry, (%) 50 45 41 40 35 30
Parts water to be evaporated to produce 1 part of powder Powder 10% water Powder 7% water Powder 3% water 0.80 0.64 0.52 0.50 0.39 0.29
0.86 0.69 0.58 0.55 0.43 0.33
0.94 0.76 0.64 0.62 0.49 0.39
From one month total material balance in the factory, loss of powder in the spray dryer was 6.4%. This accounts for product carried away with the air, spillages and losses during raw material handling.
Simple arithmetic shows the importance of the water content of slurry in relation to the quantity of water to be evaporated; and hence its effect upon both fuel consumption and plant capacity. On the average moisture content of the slurry in RSD is 41% water and 59% other ingredients, described as solids, dried to powder which contains 3% water (from one month quality control data sheet).
Therefore, 100 parts slurry contains 59 parts solids plus 41 parts water. They produce 59*(100/97) = 60.82 parts powder. This contains 60.82-59.00=1.82 parts water. Hence water evaporated = 41.00-1.82 = 39.18 parts; equivalent to 39.18/60.82 = 0.64 parts water evaporated per part powder produced. Table 5.2 summarizes the results of similar calculations for slurries
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with various possible water contents dried to produce powders of 10%, 7% and 3% moisture contents. A selection of the best scenario can be made that suits most for the existing condition in RSD.
Table 5.3. Benefits to be obtained on the tower Activity
Change in Inlet hot air temperature Outlet
350OC
Change in moisture content
35%
Total
Slurry
O
100 C
Thermal efficiency (%)
Fuel saved (m3/yr)
74.68
25.45
Powder 7% 74.68
Electrical energy saved (kwh/yr)
Economic saving: electrical and fuel (birr/yr)
Increase in Spray tower capacity (%)
187,834.04
46.12
253,231.18
487,258.44
49
71.57
253,231.18
675,092.49
49
To lower the amount of water evaporated per part of powder produced, the amount of moisture per cent in the slurry can be decreased. Conventional heavy duty powders are usually dried to about 10% moisture content. At least in part this is because removal of water from sodium tri polyphosphate hexahydrate, which these powders normally contain in substantial proportions, results in undesirable decomposition of the tripolyphosphate. For economic reasons it may be unnecessary to retain a certain amount of residual water in the powder. As the powder must of necessity be free flowing, this water can only be present as water of crystallization and not as surface moisture. Generally a spray dried powder containing a fair proportion of inorganic salts can be expected to pick up moisture on storage. However, the absorption will be slower the closer the moisture content of the powder is adjusted to that of the stable form. If a powder must be stored in ambient relative humidity exceeding 60 per cent, the risk of lump formation can be minimized by discharging the powder from the spray-tower with at least three-quarters of the stable moisture content. It is economically unsound to dry a powder to 1 per cent moisture
73
content when the powder must revert to, say, 7 percent. The operation would be a lot more efficient if the powder were dried to 7 per cent in the first place [14, 15]. In Repi Soap and Detergent S. Co, if we are to make the slurry 35% moisture content instead of 41% and dry it to 7% instead of 3% ( because it was packed 10% anyways), the fuel consumption per tone of powder with 35% water is about 0.43/0.64 = 67.2% of that with a 41% water slurry. Also, as this case was not limited by ancillaries in RSD, the productive capacity of a plant is 0.64/0.43 = 1.49 times as great. This shows that even a small change in slurry concentration has a significant effect.
Benefits to be obtained from this cleaner production opportunity on the tower are presented in table 5.3. As it can be seen from the table 675,092.49 birr per year can be saved on the tower with few operational changes (good housekeeping) and with out any additional investment. 5.2.3. Boiler
The boiler in Repi soap and detergent share company (RSD) had design capacity of 1ton of 12 bar steam per hour. The steam load of the process was measured to be 0.106ton of 7 bar steam per hour and 274.03 ton steam per year. The measurement was conducted in winter to estimate the highest steam load of the process. For fifteen days: fuel consumption of the boiler was measured by taking change in fuel level in the tanker; the working pressure was read from boiler pressure gauge and then the average was calculated. The temperature of feed water from the deareator was measured to be 67OC on the average. The efficiency of the boiler was calculated to be 76.52% using the formula shown below [21]. The process in RSD was in instantaneous load demand mode; where by a large volume of steam is required for a short period of time. In such a case a boiler with large energy storage reserve, such as a firetube, is appropriate [42].
Oversized boilers waste fuel and, because of short cycling, ultimately shorten the life of the system. A boiler cycle consists of a firing interval, a post surge, an idle period, a pre-purge, and a return to firing. Boiler “short cycling” occurs when an oversized boiler prematurely satisfies process demand and shuts down until heat is again required. Efficiency decreases when short
74
cycling occurs because heat demand is smaller than the boiler output. The decrease in efficiency occurs in part because fixed energy losses are magnified under lightly loaded conditions.
Boiler efficiency
Heat output
Heat input Q hg
100%
h f
q GCV
100% …………………. (5.3)
Where: Q
Quantity of steam generated per hour (0.106ton/h)
Q
Quantity of fuel used per hour (0.0075ton/h)
GCV Calorific value of the fuel (10,392Kcal/kg of fuel) Hg
Enthalpy of saturated steam in kcal/kg of steam (659.69)
hf
Enthalpy of feed water in kcal/kg of water (99.72)
For example, if the radiation loss from the boiler enclosure is 1% of the total heat input at full load, at half load the losses increase to 2%: and at one quarter load, the loss is 4%. Hence, over sizing of the boiler in RSD could intensify losses [43].
% Oversized
oversize proper size ……………….. (5.4) propersize
Using equation (5.4), the boiler in RSD was 838.88% oversized. This increases the radiation loss eight folds. However, for typical oil fired new boiler on full load the efficiency is 80% and on low load the efficiency is 72%
[57].
Therefore, the efficiency (76.52%) in RSD is within the
acceptable range. However, the capacity of the boiler can be used for any future expansion in the factory. In doing so, the efficiency of the boiler can be increased.
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5.3. Steam Loss 5.3.1. Boiler Steam Header The steam header in RSD was well insulated. However, steam trap installed to it released 0.95m plume length steam into the atmosphere. This is caused by an over used steam trap failure that is connected to the steam header with 7.0 bar average working pressure. The steam loss is determined to be 46.31ton/yr (fig 3.1) which amounted to 168,569.87birr/yr. The cost of steam was 3.64 birr per kg of steam produced (equations 3-1 and 3-2). This loss can be minimized by changing the stream trap. The pay back period for the steam trap is 34.14 hours.
5.3.2. Deareator The dearator in RSD used 31.53ton steam per year to heat 274.03 m3 boiler feed water. The steam loss at the dearator was 20.71% which amounted to 23,765.74 birr per year. This loss was mainly caused because the deareator was not insulated. When it is insulated with fiberglass 21,512.62 birr will be saved per annum. The payback period is 0.09 year.
5.4. Condensate Loss Condensate was formed from heavy fuel heating by steam coil. However, it was not recovered. The total amount of condensate wasted was 115.78 ton/yr. When this amount of condensate was wasted, equal amount of make up water at 23OC was heated to 67 O C in the deareator. The amount of heat required for heating water equal in amount to lost condensate in RSD (calculated using Q = mc pt) was 21,324.09 MJ/yr. In RSD the boiler was 76.52% efficient. Therefore, the energy supplied to heat the lost amount of condensate amounted [(21,324,086.78 kJ/yr) / (43,031kJ/kg) (0.920 kg/m3) (0.7652)] = 0.70 m3 of heavy fuel. This amounted to 5,194.96 birr/yr.
5.5. Service Water Loss Service water lost by washing of jerricans during liquid detergent packing process amounted to 88.35 m3/yr. This water could be reused for liquid detergent production, as long as the jerricans were clean in the first place. Therefore, if this water was to be recycled, wastewater generation can be reduced by 1.48% and 24.74 kwh can be saved.
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Pump cooling water used for homogenizer and high pressure pumps was overflowing. This was because of the amount of water used for cooling was more than required. This water is amounted to 1,126.89 m3 per year. By supplying just the right amount of cooling water controlled by valve, the service water loss can be eliminated. By doing so, 915.03kwh (530.72birr/yr) can be saved per year. And this decreases the volume of wastewater from the factory by 18.9%. Water used to wash slurry spillages from sieve filter in the first floor amounted to 6.00 m3 per year. Spillages could be avoided by putting covering metal. By doing so, 0.1% of the waste water generated can be reduced. Rare overflowing of water, caustic and LABS from storage tankers could be avoided by installing pump switch next to tankers instead of remote switch.
Water used to wash slurry spillage during pipe line washing with steam and occasional slurry bleeding from filter amounted to 17.37 m3 per year. This could be eliminated by avoiding spillage (covering with metal), and tightening bolts of the filter. This saves 0.29% of the wastewater generated.
5.6. Laundry wastewater Laundry wastewater in RSD is not high in quantity. However, its potential impact on the environment was seen in light of experimental results and current global view on the subject. In RSD the waste from the factory mixed with toilet waste water was used to grow vegetables in the factory. When excess it was stored in an open pond and over flew on the grass land.
5.6.1. Replacing STPP with Zeolite A It is evident that STPP can contribute to eutrophication problem in surface waters due to its phosphorus content. On this basis, although the debate of ‘going completely to zeolite based detergents’ continues, practically many rich countries, as described in chapter two, have decided to shift from STPP based to zeolite based detergents since the 1970’s at least in some of their seriously affected localities. According to studies conducted by the European Environment Directorate [44], most of the debates focused on the long run environmental impact of ingredients
77
(polycarboxylates) added with zeolite to replace STPP completely. Detergent reformulation and change in the cost of detergents during reformulation was also one of the concerns. In RSD already more amount of zeolite than STPP was used in the formulation and no polycarboxylate was used. Although it might be expected that some of the larger formulators would find it relatively easy to substitute one phosphate detergent with a comparable zeolite detergent currently marketed elsewhere, the situation becomes more complex where there are smaller formulators like RSD serving only the domestic market with phosphate detergents. A change in formulation may well place RSD at a disadvantage leading to a loss of its market share to the large international companies like Zahara and Aerial because in Ethiopia there is limited, if not none, experience of zeolite based detergent formulation. However, it is worth noting that the current co-existence of phosphate and zeolite detergents in many countries suggests that there would be a limited impact on the costs of detergent products to consumers. In other words, there is not a significant price differential between phosphate and zeolite detergents [1].
According to studies conducted, there may also be costs in terms of increased risks to people and to the environment associated with the increased use of those ingredients used in zeolite based detergents. Because polycarboxylates are a mixture of compounds, it has not been possible to trace their fate in the environment. As with Zeolite A, there appears to be no reason to fear toxic effects. And it is unlikely that a move from phosphate to zeolite based detergents would lead to a significant increase in risks to people and the environment
[1, 44].
The key benefit associated with moving from phosphate to zeolite detergents is reducing the phosphorus load to the environment which, in turn, will reduce problems of eutrophication. In qualitative terms, the greatest benefits would accrue in those countries with a high phosphate detergent use and existing severe problems of eutrophication. On the other hand, countries with limited phosphate detergent use would obtain few benefits from any future requirement to move to zeolite (or other phosphate-free) detergents. According to Louis Ho Tan Tai (2000), in Africa detergent consumption is below 0.002ton per person per year and in North America it is 9.8kg per person per year [1, 44].
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In Ethiopia soap is used as main cleaning aid and the amount of detergents used is meager. Hence, it is possible that the impact of using STPP based detergents on surface waters in Ethiopia has not yet been felt. In RSD or in the nearby river no occurrence of major eutrophicaton problem was observed. Therefore, under the conditions prevailing, not only that RSD did not have enough reason to shift from STPP to zeolite based detergents but also did not have legal basis to do so. The Quality and Standards Authority of Ethiopia states that a detergent must contain a minimum of 10% STPP (Appendix 6). However, the agenda will be on the table one day in the future, in fact when consumption becomes significant. And that is what happened in the developed part of the world.
5.6.2. Laundry Wastewater for Irrigation Purpose According to FAO irrigation and drainage paper number 47, properly planned use of municipal wastewater alleviates surface water pollution problems and not only conserves valuable water resources but also takes advantage of the nutrients contained in sewage to grow crops. The availability of this additional water near population centers will increase the choice of crops which farmers can grow. The nitrogen and phosphorus content of sewage might reduce or eliminate the requirements for commercial fertilizers. It is advantageous to consider effluent reuse at the same time as wastewater collection; treatment and disposal are planned so that sewerage system design can be optimized in terms of effluent transport and treatment methods. However, from the point of view of health, a very important consideration in agricultural use of wastewater, the contaminants of greatest concern are the pathogenic micro- and macroorganisms. Even if toxic materials are not present in concentrations likely to affect humans, they might well be at phytotoxic levels, which would limit their agricultural use
[45].
Therefore, wastewater reclamation for irrigation purpose and discharging wastewater require scrutiny to prevent their impact on the environment and human health. In RSD wastewater (laundry and toilet) are mixed and used to grow vegetable and grass in the factory compound. Six samples of this wastewater taken from two spots in a judgmental sampling method were analyzed at the Addis Ababa EPA laboratory. The level of pollution of the wastewater was seen and studied in light of Ethiopian EPA, WHO and FAO standards according to their relevance. Laboratory results with corresponding results are listed in table 5.4.
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Table 5.4. Comparative presentation of RSD wastewater laboratory results along with standards Parameters
PH Conductivity, ms/cm Chloride (cl-) Sulphate (SO42-), mg/L Phsphate (PO43-), mg/L Nitrate (NO3), mg/L Nitrite (NO2-), mg/L COD, mg/L Alkalinity (as HCO3), mg/L Total Nitrogen (as N), mg/L BOD5 at 20 0C, mg/L Sodium (Na), mg/L
RSD factory wastewater before and after mixing with toilet wastewater Before After mixing mixing 9.6-10.2 9.4-9.7 2.2-5.3 2.0-3.4 75.8-79.0 62.8-66.6 200-210 200-300 99.0-113.5 68.5-78 14.4-124.6 108.4117.2 0.059-0.987 0.2060.209 800-1426 500-960 119.6-237.7 237.6406.4 1.0-4.0 26.8-29.2
Potassium (K), mg/L Calcium (Ca), mg/L
58-132 481.251190.00 3.53-17.87 0.276-1.07
Magnesium (Mg), mg/L SAR Coliforms Total MPN/100mL Fecal
0.51-1.17 960.75 14Ex5 17Ex5 14Ex5
102-136 397.50725.00 14.05-29.5 0.5453.920 1.17-2.31 318.64 17 Ex5 35Ex5 22Ex5 33Ex6
FAO standards
Ethiopian EPA standards of effluent application to: Lands
6.5-8.4 7-30 4-10
5.5 - 9 1000 1000
5-30
Inland waters 6-9 1000 1000 10 20
250
80 500
80
100 100 0.2 - 5.0
WHO (1989): Water to be used for irrigation purpose Fecal Coliforms (geometric mean number per 1000mL :
400
1000)
Pathogenic bacteria will be present in wastewater at much lower levels than the coliform group of bacteria, which are much easier to identify and enumerate (as total coliforms/100 mL). Escherichia coli are the most widely adopted indicator of faecal pollution and they can also be isolated and identified fairly simply, with their numbers usually being given in the form of fecal colifoms (FC)/100 mL of wastewater
[45]. Therefore,
coliforms were used to investigate the level
of health risk that the wastewater in RSD posed on all that might be in touch with it in some way.
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In the course of mixing factory and toilet wastewaters, some compositions increased while others decreased. This accounted for composition of both streams and the effect of dilution. Nutrient surplus such as phosphorus (P) and nitrogen (N) are major causes of eutrophication and algal bloom if high amount of these nutrients are discharged into water bodies. As mentioned in previous section (Chapter 2) N concentration is not considered to be a major problem with laundry water reuse due to its low concentration in soils. Instead, laundry water is more likely to have a problem with elevated P content. Phosphorus from detergents does not pose a major problem when disposed to land since it is normally required as a nutrient for plants. However, soil may become phosphorus saturated if the application rate is higher than the plant’s uptake rate. Hence there is a potential for leaching to groundwater or transport via runoff to a watercourse if laundry water is used for irrigation with high concentration of these nutrients. Laundry water samples in this study exhibited higher values of P than the maximum limit mentioned in the Ethiopian standard for in land water. The elevated P levels observed in these laundry water samples might be due to the STPP in the detergent formulation. A comparison of laundry water quality obtained in this study with the water quality recommended for irrigation in the above standards showed that chemical parameters, such as pH, BOD, COD, sodium, nitrate, phosphate, SAR and coliforms reached unacceptably high levels at which the irrigation with this water could pose a potential hazard to trees, soils, groundwater and may also have health impact on farmers and consumers. Therefore, direct laundry water reuse for irrigation in RSD needs to be approached with some care and that specific irrigation practices or treatment methods might be required to overcome problems associated with the elevated levels of these quality parameters. However, the levels of total dissolved salt estimated from EC values, calcium, sulphate, chloride, nitrite and total nitrogen in the wastewater in RSD were found to be quite reasonable with the quality requirement for irrigation. This indicates that laundry water may not cause severe salinity or nitrogen pollution related problems if it is used for irrigation. The elevated sodium concentration in laundry water can lead to sodicity problem which cause damage to plants after a long period of application. The soil structure may also be affected by the use of high sodium content laundry water, such as soil particle dispersion, reduction in filtration
81
rate and soil pore blockage. However, more information on the soil properties is required in order to conclude whether or not laundry water severely impacts on the soil structure stability. According to WHO (1989) directions, low cost interventions could include information on hygiene behavior for farmers, wearing of shoes and gloves while working in wastewater irrigated fields. The idea of reclaiming wastewater for irrigation purpose has a longstanding history and it is commendable to use wastewater in RSD for same purpose so long as it is safe for use. As it can be seen from the table 5.4, neither discharging to surface water nor using the wastewater for irrigation purpose was advisable even for one reason alone. The coliforms far exceed all standards that its use can result in spreading of some epidemic diseases according to guide lines given by WHO (1989). To make things even worse, the water is used to irrigate vegetables that are eaten uncooked. Therefore this puts the health of the farmers and consumers at stake. The groups potentially most at risk from wastewater reuse in agriculture are the farm workers, their families, crop handlers, consumers of crops, and those living near wastewater-irrigated areas. The approach required to minimize exposure depends on the target group. Farm workers and their families have higher potential risks of parasitic infections. Protection can be achieved by low-contaminating irrigation techniques (as above), together with wearing protective clothing (e.g. footwear for farmers and gloves for crop handlers) and improving levels of hygiene both occupationally and in the home can help to control human exposure. Provision of adequate water supplies for consumption (to avoid consumption of wastewater) and for hygiene purposes (e.g. for hand washing) is important. Consumers can be protected by cooking vegetables, and by high standards of personal and food hygiene [27]. In RSD the wastewater quantity can be reduced 84.28% and its quality can be improved by keeping toilet wastewater in the septic tank and implementing cleaner production opportunities in the factory. Improving housekeeping, developing formal operating procedures and training staff in cleaner production techniques presented a very low-cost opportunity to provide substantial annual savings. The feasibility of Cleaner Production in RSD is summarized below in table 5.5.
82
Table 5.5. Technical, Economic and Environmental Feasibility in RSD No. Action
1
Estimated
Estimated
Payback
Technical
Economic
Environmental
cost (birr)
annual benefit
period
feasibility
feasibility
feasibility
Priority
(birr)
(years)
187,834.04
Very good
Very good
Very good
1
487,258.43
Very good
Very good
Very good
1
Spray tower thermal efficiency improvement
2
Slurry moisture reduction
3
Furnace insulation
2,498.18
29,872.90
0.08
good
good
good
2
4
Duct and fan insulation
1,775.18
25,359.73
0.07
good
good
good
2
5
New steam trap installation
330.00
168,569.86
0.0019
Very good
Very good
Very good
2
6
Dearator insulation
1,936.14
21,512.62
0.09
good
good
fair
2
7
Condensate recovery
1,075.00
5,194.96
0.21
good
fair
fair
2
8
Recycling jerrycans
Very good
1
Very good
1
Very good
Very good
1
Very good
good
1
Very good
Very good
1
good
washing water 9
Optimizing pump cooling
530.72
Very good
fair
water 10
Tightening bolts and nuts for slurry filter
11
Covering slurry filtering sieve
12
Halting toilet wastewater discharge 83
5.7. Implementation and Monitoring Now a list of options has been studied with their feasibility. Hence, it’s time to implement them. To get the best out of the cleaner production assessment, the Cleaner Production Implementation Plan in RSD should be integrated into the company’s business and operating plans. Resources needed for these initiatives need to be provided in the company’s budgeting process.
The options to be implemented first should be those involving operational or procedural changes with least cost (priority 1 in Table 5.5). This will provide speedy results and greater impetus for implementing other options. This approach will also highlight the need for a new discipline in the operations, and the need to establish a cleaner production culture in the business. Without this cultural change, isolated measures (such as installing equipment or instruments) will not be fully effective, and will not yield long-term improvement [10].
Cleaner production assessment is not a one-time-task. Once Cleaner Production is implemented in RSD, it is a process that should be monitored and undertaken continuously. Then, the company will benefit a lot from it continuously. The summary of the cleaner production opportunities in RSD is given in Table 5.6.
84
Table 5.6. No. I
II
III IV
V
Summary of Cleaner Production (CP) Opportunities for Repi Soap and Detergent Share Company
Problem area Heavy fuel loss
Steam loss
Steam condensate loss Service water loss
Wastewater for irrigation
Grand total
CP opportunities 1.Spray tower thermal efficiency improvement 2. Slurry and powder moisture content change 3. Furnace outer wall insulation 4. Duct and fan Insulation Sub total 1. Steam header steam trap change 2. Deareator insulation Sub total Condensate recovery 1. Recycling jerrycans washing water 2. Optimizing pump cooling water 3. Avoiding spillage, slurry bleeding from filter 4. Prevent slurry spillage (1stf loor) Sub total 1. keeping toilet wastewater in septic tank
Amount saved (ton/yr)
Electrical energy saved (kwh/yr)
253,231.18
Fuel saved (m3/yr) 25.45
Economic benefits (Birr/yr) 187,834.04
46.12
487,258.43
4.05
29,872.90
Qualitative benefits
25,359.73 253,231.18
75.62
46.31
730,325.10 168,569.86
6.19 52.22 115.78
22,536.66 190,082.48 5,194.96
88.35
24.74
14.35
1,126.89
915.03
530.72
17.37
14.10
8.18
6.00
4.87
2.82
1,238.60 3,784.32
958.74
556.07
Meets environmental standards and prevents health risks 254,189.92
85
75.62
926,158.61
6. CONCLUSION AND RECOMMENDATION From the result and discussion chapters, Cleaner Production options in RSD are technically, financially and environmentally feasible. And, the economic and environmental benefits that can be obtained from implementing cleaner production are substantial. As a result, prevents pollution, rewards the company financially, creates good company image, and enables the company to meet environmental standards.
In RSD the idea of using wastewater for irrigation purpose can be encouraged. However, the wastewater having the quality that exceeds safety limits in light of both local and international standards should not be released to surface water nor be used for irrigation purpose because of its potential hazard to the public and the environment. After cleaner production opportunities forwarded in this paper are implemented, the source of wastewater will be only laboratory wastewater, canteen wastewater serving few people and cloth washing wastewater. Therefore, the quantity and pollution level of the water will be significantly reduced as the main sources of pollution were wastewaters from factory and toilet. Nevethless, even after implementation of these cleaner production opportunities, the quality of water should be checked periodically whether to use it for irrigation purpose or release it to the nearby river.
From the cleaner production assessment in RSD: by controlling operating parameters and manipulating hot air temperature and slurry moisture on the spray dryer 253,231.18kwh/yr electrical energy and 75.62m3/yr fuel can be saved. This amounts to 730,325.10 birr/yr. By avoiding steam loss at the deareator and boiler steam header 190,082.48 birr/yr can be saved. By recovering condensate 5,194.96birr/yr can be saved. Also by just undertaking good house keeping 1,238.60m3/yr service water can be saved moreover discharge of wastewater can be reduced by 84..28%.
86
Therefore, it can be concluded that RSD can obtain wide financial and environmental rewards, if it implements and continues to implement Cleaner Production. From this Cleaner Production Assessment in RSD, it is recommended that:
1. RSD release no toilet wastewater nor should it use the wastewater for irrigation purpose by mixing it with factory wastewater or whatsoever. By so doing, it can meet environmental standards and prevent health risk on consumers and farmers.
2. RSD shall use water for irrigation purpose by taking all precautionary measures to prevent health risk both to the farmers and consumers. In addition, avoid damage to soil, plants and water.
3. RSD implement the proposed cleaner production opportunities continually. As a result, obtain economic and environmental benefits.
4. The standard requirements for detergents formulation in Ethiopia needs to be adjusted to enable it protect the environment from eutrophication problem especially in relation to the standard requirement of phosphates in builders such as STPP. 5. In this study of cleaner production opportunity assessment for RSD, the methodologies and procedures taken to assess the processes, pinpoint problem areas and addressing them can also be used in industries similar to RSD, when there is analogy in the p rocesses.
87
REFERENCES 1. Risk & Policy Analysts Limited (RPA): prepared for the European Commission, (2006). non-surfactant organic ingredients and zeolite-based detergents, London, UK http://ec.europa.eu/enterprise/chemicals/legislation/detergents/studies/non_surfactant_org anic_ingredients_and_zeolite_based_detergents.pdf , ( March 7, 2008) 2. Manushani Pillay. Detergent Phosphorus in South Africa: Impact on eutrophication with specific reference to the Umgeni catchment, University of Natal, Durban, South Africa. http://www.nu.ac.za/department/data/WRC465.pdf , (May 2, 2008) 3. Hoovers: A D&B Company, (2008). Industry Review: Soap and Detergent Manufacture, Boulevard Austin, U.S.A. http://www.hoovers.com/soap-and-detergent-manufacture/-ID__223--/free-ind-fr-profile-basic.xhtml, (April 12,2008) 4. Louis Ho Tan Tai, (2000). Formulating detergents and personal care products: A guide to product development, AOVS press, Lambersart, France 5. Rene Van Berkel, (2000). Cleaner Production for Process Industries, Curtin University of Technology, Western Australia http://www.cleanerproduction.curtin.edu.au/ , (March11,2008) 6. Dr. Jonathan Köhler, (2001). Detergent phosphates and detergent Ecotaxes:: a policy assessment, University of Cambridge, UK http://canadagazette.gc.ca/partI/2008/20080628/html/regle2-e.html, (March 3,2008) 7. Environmental Protection Authority (EPA 547/04), (2004). The Disposal of Soaps and Detergents, Adelaide, South Australia. www.epa.sa.gov.au/pdfs/soaps _d etergents.pdf , (May5, 2008) 8. Minh Nhat LE, (2005). Investigation on Reuse Potential of LaundryWater for Household Garden Irrigation in Toowoomba, University of Southern Queensland Faculty of Engineering and Surveying, Australia. http://eprints.usq.edu.au/503/1/Final_Thesis_MINH_NHAT_LE.pdf , (March13, 2008) 9. UNEP CP, (2001). Cleaner Production Assessment in Industries, Paris, France 10. NSW Environment Protection Authority, (2000). Cleaner Production: A Self-Help Tool for
Small
to
Medium-Sized
Businesses,
Sydney
South
NSW,
Australia.
(http://www.epa.nsw.gov.au/cleaner_production/selfhelptool.htm, (May2, 2008)
88
11. Mariette T. Johnson and Barbara Marcus, (1996). Competitive implications of environmental regulation:in the laundry detergent industry, Washington, D.C. 12. Douglas M. Cosidine, (1974). Chemical and Process technology encyclopedia, McGrawHill, New York, U.S.A. 13. Gir Raj Prasad, (1996). Manufacture of Perfume, Cosmetics and Detergents: 7th edition, SiRi publication division, Delhi, India. 14. Edgar Woollatt, (1985). The manufacture of Soaps, other Dteregents, and Glycerine, Ellis Horwood Ltd, Great Britain. 15. A. Davidsohn and B.M. Milwidsky, (1978). Synthetic Detergents, 6th edition, John Wiley & Sons, New York. 16. Wolfgang Gerhartz, (1987). Ullmann’s Encyclopedia of Industrial Chemistry, Graphiscer Betrieb konrad Triltsch, Germany 17. BETE Fog Nozzle, Inc., (2005). BETE Spray Dryer Manual. www.bete.com/pdfs/BETE _S prayDryManual.pdf , (April 9, 2008) 18. Vikram Shabde, B.E., (2006). Optimal design and control of a spray drying process that manufactures hollow micro-particles, Texas tech university , U.S.A. http://etd.lib.ttu.edu/theses/available/etd11062006115730/unrestricted/Shabde_Vikram_ Diss.pdf , (May 11, 2008) 19. Stephen Zehr, (1997). Process energy efficiency improvement in wisconsin cheese plants, university of Wisconsin, Madison. http://minds.wisconsin.edu/bitstream/handle/1793/7763/Zehr.pdf?sequence , (March 24, 2008) 20. U.S. Congress, Office of Technology Assessment, (1993). Industrial Energy Efficiency, Washington,D.C.,U.S.A www.theblackvault.com/documents/ota/Ota_1/DATA/1993/9330.PDF , (March 28,2008) 21. Office of Energy Efficiency, (2002). Energy Efficiency Planning and Management Guide, Ottawa, Canada. http://oee.nrcan.gc.ca/publications/infosource/pub/cipec/efficiency/pre.cfm?text=N&print vie, (May16 , 2008)
89
22. Missouri Industrial Assessment Center, (2007). Industrial Energy Au dit Workshop, College of Engineering, University of Missouri-Columbia. http://iac.missouri.edu/Workshop _presentation.pdf , (March 13,2008) 23. United
Nations
Environment
Programme.
Water
and
Wastewater
Reuse:
an
environmentally sound approach for sustainable urban water management, Osaka, Japan. www.unep.or.jp/Ietc/Publications/Water _Sanitation/wastewater _ reuse/Booklet euse.pdf , (April 4, 2008) Wastewater _R 24. S.Vigneswaran and M.Sundaravadivel, (2004). Recycle and reuse of domestic wastewater, Sydney, Australia. www.eolss.net/ebooks/Sample%20Chapters/C07/E2-1401.pdf , (March 2, 2008) 25. Sabiena Feenstra, Raheela Hussain and Wim van der Hoek, (2000). Health risks of irrigation with untreated urban wastewater in the southern Punjab, Pakistan. www.iwmi.cgiar.org/health/wastew/R-107.pdf , (March 19, 2008) 26. A. Andreadakis*, E. Gavalaki, D. Mamais and A. Tzimas, (2001). WASTEWATER REUSE
CRITERIA
IN
GREECE,
Ermoupolis,
Syros
island,
www.gnest.org/journal/Vol5_No1.asp?url=Vol5_No1/02_Andreadakis.pdf ,
Greece.
(May
17,
2008) 27. Dr Ursula J. Blumenthal, Dr Anne Peasey, Prof. Guillermo Ruiz-Palacios and Prof. Duncan D. Mara, (2000). Guidelines for wastewater reuse in agriculture and aquaculture: recommended revisions based on new research evidence, London School of Hygiene & Tropical
Medicine,
UK
WEDC,
Loughborough
University,
www.lboro.ac.uk/well/resources/well-studies/full-reports-pdf/task0068i.pdf ,
(April
UK. 9,
2008) 28. U.S. Environmental Protection Agency, (2004). Guidelines for Water Reuse, Municipal Support Division Office of Wastewater Management Office of Water, Washington, D.C. www.epa.gov/nrmrl/pubs/625r04108/625r04108.pdf , (May 4, 2008) 29. EPA Victoria information bulletin: publication 812.2, (2006). Domestic wastewater management
series:
reuse
options
for
household
wastewater,
Australia.
www.emro.who.int/ceha/clearingh_waterdemand/portals/waste/scen2_off_on.doc , (May17, 2008)
90
30. World Health Organization Regional Office for the Eastern Mediterranean Centre For Environmental Health Activities, (2006). Overview of greywater management Health considerations, Amman, Jordan. 31. Environmental Protection Agency: Office of Research and Development, (2001). Guide to Industrial Assessments for Pollution Prevention and Energy Efficiency, Cincinnati, Ohio, U.S. http://www.p2pays.org/ref/19/18351.pdf , (April 11, 2008) 32. Jean-Jacques bimbeneta, pierre schuckb*, michel roignantc, gérard bruléc and serge méjeanb, (2002). Heat balance of a multistage spray-dryer: principles and example of application, 91744 Massy, France. http://lait.dairyjournal.org/articles/lait/pdf/2002/04/16.pdf , (March 27, 2008) 33. Office of energy efficiency, (2004). Energy Efficiency Planning and Management Guide, Canada. http://oee.nrcan.gc.ca/publications/infosource/pub/cipec/efficiency/2_01.cfm?text=N&pri ntvie , , (May16, 2008) 34. Gilbert A. McCoy, Todd Litman and John G. Douglass, (1993). Energy Efficient Electric Motor Selection Handbook, Olympia, Washington. www.wbdg.org/ccb/DOE/TECH/ce0384.pdf , (April 19, 2008) 35. Spirax Sarco, (2005). Methods of Estimating Steam Consumption: Module 2. www.devlieger belgium.com/Brochures/Steam%20Heat%20Consumption%20Calculations.pdf ,
(April
6, 2008) 36. U.S. Department of Energy. How to calculate the true cost of steam: A best practices steam technical brief. www.p2pays.org/ref/40/39595.pdf , (May, 19) 37. Bureau of Energy Efficiency. Furnaces and Refractories. www.energyefficiencyasia.org/docs/ee_modules/workshop%20exercise%20%20Furnaces%20andrefractories.pdf . (May 3, 2008) 38. GTZ - Pilot Programme for the Promotion of Environmental Management in the Private Sector &
of Developing Countries (P3U), (1998). Good Housekeeping Guide for Small
Medium
Sized
Enterprises,
Wachsbleiche
1,
53111
www.ecoparc.ch/smene_f/pdf/good _HK_ guide.pdf , (April 27, 2008)
91
Bonn,
Germany.
39. R. K. Sinnott, (1993). Coulson & Richardson’s Chemical Engineering volume 6: Chemical Engineering Design, Butterworth-Heinemann Ltd, Great Britain 40. J.P. Holman, (2001). Heat Transfer: 8th edtion, McGraw-Hill, Singapore 41. Stewart Gibson, (1999). Improving Spray Drying Efficiency: APV Americas, U.S.A. www.processheating.com/Articles/Feature_Article/cdb76053d9268010VgnVCM100000f932a8c0 , (April 3, 2008) 42. Boiler Selection Considerations. www.boilerspec.com/speci-fire_pdf/i1-boiler_selection-4-10.pdf , (June 25, 2008). 43. Henery Manczyk, (2001). Optimal boiler size and its relationship to several efficiency, New York. www.energy.rochester.edu/efficiency/optimal _b oiler _s ize.pdf , (May 5, 2008) 44. EU environment directorate, (2002). Phosphates and alternative detergent builders – final report, Wiltshire. http://ec.europa.eu/environment/water/pollution/phosphates/pdf/phosphates.pdf , (February 24,
2008)
45. M.B. Pescod, (1992). Wastewater treatment and use in agriculture: FAO irrigation and drainage paper 47, Rome. 46. Roy C Baker, Kenneth G. Oiver Joseph A. Parker, (1985).Basics of industrial steam utilization for plant maintenance and operating U.S.A
92
personnel, Parker Press, Los Angeles,
Appendix 1 - Laboratory Analysis Method, reagent and apparatus required The Physico-Chemical analysis of the wastewater in RSD was conducted in the Addis Ababa Environmental Protection Authority Laboratory. 1. Alkalinity
Method: titration method Reagent
a) Sodium carbonate solution, b) Standard sulfuric acid or nitric acid both 0.1N and 0.02N, c) Bromcresol green indicator solution, d) Mixed bromcresol green-methyl red indicator solution, e) Metacresol purple indicator solution, f) phenolphthalein solution, alcoholic, PH 8.3 indicator, g) sodium thiosulfate, 0.1N Apparatus
a) Electrometric titrator b) Titration vessel c) Magnetic stirrer d) Pipets, volumetric e) Flsks, volumetric, 1000-, 200-, 10-mL. f) Burets, borosilicate glass, 50-, 25-, 10-mL. g) Polyolefin bottle, 1-L 2. 5-Day BOD Test Apparatus:
1. Incubation bottles, of 300mL capacity, having a ground-glass stoper and a flared mouth. Bottles are cleaned with a detergent, rinsed thoroughly and drained well before use. 2. Air incubator, with a thermostatistically controlled temperature of 20 ± 1oC. 3. Magnetic stirrer, with TFE stirring bar. 4. Membrane electrode DO meter, Model 90-D. The meter was calibrated according to manufacturer’s instruction
93
5. Volumetric Pipettes, with 1000-5000 µL capacity. 6. Analytical balance with capacity of weighing to 0.1 mg. 7. Aluminium foil Reagents
1. Phosphate buffer solution: dissolve 8.5 g KH2PO4; 21.75 g K2HPO4; 33.4 g Na2HPO4.H2O and 1.7 g NH4Cl in about 500 mL distilled water and dilute to 1 L. 2. Magnesium sulphate solution: dissolve 22.5g MgSO4.7H2O in distilled water and dilute to1L. 3. Calcium chloride solution: dissolve 27.5 g CaCl2 in distilled water and dilute to 1L solution. 4. Ferric chloride solution: dissolve 0.25 g FeCl3.6H2O in distilled water and dilute to1 L. 5. Acid and alkali solutions: 1N for neutralisation of caustic and acidic samples. Acid solution: slowly add 28 mL concentrated H2SO4 acid while stirring to distilled water and dilute to 1 L. Alkali solution: dissolve 40 g NaOH in distilled water and d ilute to 1 L. 6. Sodium sulphate solution: dissolve 1.575 g Na2SO3 in 1L distilled water 7. Nitrification inhibitor: 2-chloro-6-(trichloro methyl) pyridine 8. Glucose-glutamic acid solution: dry reagent-grade glucose and reagent-grade glutamic-grade acid at 103oC for 1 hour. Add 150 mg glucose and 150 mg glutamic acid to distilled water and dilute to 1 L. All reagents are prepared in advance except sodium sulphate and glucose-glutamic acid solutions, which need to be prepared immediately before use. However, depending on characteristics of water or wastewater samples, only certain reagents are used for BOD5 analysis. Procedure
• Prepare dilution water by adding 1 mL each of phosphate buffer, MgSO4, CaCl2 and FeCl3 solutions to each litre of distilled water. Each sample needs approximately 3 L of dilution water. • Before use bring dilution water to temperature by storing in the incubator at 20oC. • Saturate with DO by shaking in partially filled bottle or by aerating with organic free filtered air. • Bring samples to about 20oC before making dilutions. • Using graduated cylinders or volumetric flasks to prepare solution.
94
• Dilute samples with dilution water in different concentrations so that residual DO of at least 1 mg/L and a DO uptake of at least 2 mg/l after 5 day incubation. For laundry water, use the following dilutions: 2 mL/300 mL bottle, 6 mL/ 300 mL bottle and 20 mL/ 300 mL bottle. • Prepare dilutions directly in BOD bottles using a wide tip volumetric pipet to add the desired sample volume to individual 300 mL bottles. Fill bottles with enough dilution water so that insertion of stopper will displace all air, leaving no bubbles. • Determine initial DO on the bottle of each dilution using membrane electrode DO meter while stirring. Time period between preparing dilution and measuring initial DO should not exceed 30 minutes. • Replace any displaced contents with dilution water before capping. • Stopper tightly, water seal with aluminium foil and inc ubate for 5 days at 20oC. • Determine final DO on the bottle after 5 day incubation. • Rinse DO electrode between determinations to prevent cross contamination of samples. 3. Chemical Oxygen Demand (COD)
Method: Reactor Digestion Method *; USEPA approved for reporting waste water analysis. Table 1. Required reagents and Apparatuses for COD analysis No 1
2
Description
Quantity required per test
Unit
Cat. No
Required reagent
High range, 0 to 1,500 mg/L COD
1 to 2 vials
25/pkg
21259-25
Water, deionized
Varies
4L
272-56
Blender, 2-speed, 240 V
1
each
26161-02
Cap Tool, COD
1
each
45587-00
COD Reactor, 120/240 Vac
1
each
45600-00
Cod vial Adapter, Dr/2010
1
each
44799-00
Pipet, tensette, 0.1 to 1.0 mL
1
each
19700-01
Pipet, volumetric, class A, 2 mL
1
each
14515-36
Pipet filler, safety bulb
1
each
14651-00
Require apparatuses
95
Other apparatus
Other apparatus other than the above includes Flask bottle for dilution of sample. I used 500 mL and 1000 mL class A bottles.
4. Nitrite
Method: Diazotiztion method ( USEPA approved for reporting wastewater analysis) Apparatus: Spectrophotometer Model: DR/2010 Manufacturer: HACH Reagent: NitriVer 3
5. Nitrate
Method: Cadmium reduction method ( USEPA approved for reporting wastewater analysis) Apparatus: Spectrophotometer Model: DR/2010 Manufacturer: HACH Reagent: NitriVer 5
6. Phosphates
Method: Persulfate UV oxidation method Apparatus: Spectrophotometer Model: DR/2010 Manufacturer: HACH Reagent: Potassium persulfate
7. Sulfate
Method: SulfaVer 4 method ( USEPA approved for reporting wastewater analysis) Apparatus: Spectrophotometer Model: DR/2010 Manufacturer: HACH Reagent: SulfaVer 4 sulfate
96
8. pH and EC Determination
Method: potentiometric method Apparatus: pH meter Apparatus 1. pH meter: Model pH 330i
Manufactured by WTW Pty Ltd, capable of reading to the nearest 0.01 1.
EC meter: Model pH/CON 510 series Manufactured by OAKTON Pty Ltd, capable of reading to the nearest 1 µS/cm
2.
Glassware
Procedure
1. pH meter calibration: calibrate the temperature electrode of pH meter against the temperature measured by the good quality mercury thermometer. Then calibrate the meter against the pH buffer solutions obtained from the manufacturer. All calibration standard procedures follow the manufacturer’s instructions. 2. EC meter calibration: Calibrate the temperature electrode against the temperature of the good quality mercury thermometer. Then calibrate the meter against the EC buffer solutions obtained from the manufacturer. All calibration standard procedures follow the manufacturer’s instructions. 3. Warm the chilled samples to room temperature of about 20oC 4. Stir the samples in glass beaker thoroughly before taking the reading 5. pH meter will provide a direct reading of sample pH on the pH screen at 20oC 6. EC meter will read and convert EC values of samples at 20oC into those at 25oC automatically and will display it on screen of EC the meter. Therefore, the results given by EC meter are sample EC at 25oC
97
9. Total Nitrogen (0 to 0.25 m/L N)
Method: TNT Persulfate Digestion Method. Table 2. Required reagents and Apparatuses for total nitrogen analysis No
Quantity
Description
Unit
Cat. No
required / test 1
Required reagent
Total Nitrogen Hydroxide reagent vials 0.1 N
2 vials
25/pkg
26717-25
Total Nitrogen persulfate reagent powder pillow
2 Pillows
100/pkg
26718-49
Total Nitrogen reagent A powder Pillows
2 Pillows
100/pkg
26719-49
TN reagent powder pillow
2 Pillows
100/pkg
26720-49
TN Reagent C vials
2 vials
25/pkg
26721-25
Water, Deinized
varies
4L
272-56
COD Reactor, 115/230, North American plug
1
each
45600-00
COD Vial Adapter, DR/2010
1
each
44799-00
Funnel, micro
3
each
25843-35
Test tube cooling rack
1-3
each
18641.00
Require apparatuses
10. Sodium (Na), Potassium (K), Calcium (Ca) and Magnesium (Mg) were analyzed by using
Atomic Absorption Spectroscopy (Analytik Jena) and the model was: novAA 400-/ novAA 300. Standard solution reagents were used for each one of them respectively
11. Coliforms (Total and fecal)
Method: Membrane filtration (MF method) Model: ELE paqualab 50 Reagent: Lauryl Sulfate
98
Appendix 2 - Experimental Analysis Result Sampling Point
Parameter Analysed
1U
2U
3U
1M
1M
1M
pH
9.6
9.8
10.2
9.7
9.4
9.7
Conductivity, mS/cm
2.2
3.0
5.3
3.1
2.0
3.4
Chloride (Cl-), mg/L
76.4
75.8
79.0
66.6
62.8
65.4
Sulphate (SO42-), mg/L
200
200
210
200
300
300
Phosphate (PO43-), mg/L
106.5
99.0
113.5
68.5
78
69
Nitrate(NO3-), mg/L
124.6
14.4
87.0
117.2
112.8
108.4
Nitrite(NO2-), mg/L
0.059
0.062
0.987
0.206
0.209
0.206
COD, mg/L
800
1426
1320
960
500
680
153.4
119.6
368.0
406.4
237.6
1.0
2.2
28.0
29.2
26.8
Alkalinity (as HCO3), 237.7 mg/L Total Nitrogen (as N), 4.0 mg/L BOD, mg/L
80
58
132
136
102
130
Sodium (Na), mg/L
481.25
661.25
1190.00
725.00
465.00
397.50
Potassium (K), mg/L
17.875
14.750
3.525
25.250
29.500
14.050
Calcium (Ca), mg/L
1.070
0.826
0.276
0.746
3.92
0.545
1.05
0.508
1.35
2.31
1.17
Magnesium (Mg), mg/L 1.17 Coliforms,
Total
17x105
14x10 5
17x10 5
33x10 5
34x10 5
35x10 5
MPN/100 mL
Fecal
14x105
14x10 5
13x10 5
22x10 5
33x10 5
28x10 6
U M
Wastewater from factory before it was mixed with toilet wastewater Wastewater after factory and toilet wastewater are mixed
99
Appendix 3 - Resource Consumption and Wastewater generation Description
Service water used, m3/yr
Wastewater generated, m3/yr
Steam utilized, ton/yr
Steam wasted, ton/yr
1. Powder detergent Production 1.1. Paste preparation unit 1.1.1. NaOH dilution 1.1.2. Mixing and pumping 1.1.3.Pipe line washing 1.2. Slurry preparation unit 1.2.1. Mixing 1.2.2. 1st filtration spillage and leakage washing 1.2.3. 2nd filtration and Pump cooling 1.2.4. Filtration and pumping 1.2.5. pipe line washing 1.3. Spray drying unit 1.3.1. exhausting air 1.3.2. Powder scraping 1.4. Air lift
2,241.99
1,169.12
227.72
71.71
362.59
12.04
Electrical energy consumed, kwh/yr 539,326.78
Heavy fuel utilized, m3/yr 310,500
NaOH, ton/yr
STPP, ton/yr
Zeolite, ton/yr
LABS, ton/yr
Solid ingredients, ton/yr
122.08
143.86
188.41
358.20
929.68
42,296.83
122.08
358.20
42,296.83
122.08
358.20
78.13 284.46 12.04 1,605.37
1,150.26
455.11 6.00
6.00
1,144.26
1,144.26
49.50
152,052.48
37.46
45,795.84
106,256.64 12.04 101,625.60 95,193.60 6,432.00 77,775.74
100
143.86
188.41
929.68
1.5. Packing 1.6. Hot air generator unit 1.6.1. Fuel heating 1.7. Boiler unit 1.7.1. Feed water heating 1.7.2. Fuel heating 1.7.3. Steam header loss 1.7.4. Steam blow down 2. Liquid detergent production and lighting 2.1. Mixing 2.2. Manual packing and jerrycan washing 3. Bar detergent production 3.1. Sigma mixer 3.2. Milling 3.3. Plodding 3.4. Cutting 4. Laboratory 5. Clothes washing 6. Wastewater from canteen 6. Toilet septic tank 7. Ground water pumping Total
108.59
91,967.40 92,033.34
291,210
1,575.39
19,290
108.59 274.03 274.03
18.87
32.19 25.00
71.71 6.53
7.19 46.31 18.87 998.17
88.35
909.82 88.35
88.35
18.87 2,167.26
25.09
229.09
36.01
2,167.26
25.09
229.09
36.01
240.70
231,662.93
125.00
250.00
437.50
1,952.50
235.00 2.85 2.85
38,993.76 109,982.40 47,992.32 36,194.21
125.00
250.00
437.50
1,952.50
268.86
438.41
1,024.79
2,918.19
255.13 596.84
255.13 596.84
86.40
86.40 3,784.32 2,742.41
4,419.23
5,980.17
202.32
71.71
795,899.38
101
310,500
147.17
Appendix 4- Process parameter measurements Boiler steam
Furnace surface temperature at three points, (OC)
production
Hot air duct surface temperature at three points (OC)
(ton/h) 0.068 0.100 0.162 0.088 0.119 0.125 0.118 0.088 0.093 0.102 0.154 0.079 0.107 0.083 0.108 0.106
106 95 104 104 98 103 102 104 95 98 105 103 99 107 102 101.67 -
118 96 120 118 106 109 117 111 103 97 121 109 116 113 124
108 86 91 102 91 101 88 93 103 99 103 106 102 93 82 111.2 96.5
90 92 94 90 94 92 88 91 95 93 92 89 92 95 93 92.0
96 80 84 100 93 98 94 83 92 84 98 87 90 95 89 90.83
90 100 93 96 94 93 97 98 91 87 90 95 90 98 93 93.67
Hot air to spray tower (OC)
280 300 253 276 300 287 293 258 284 287 300 285 258 299 285 283
The numbers in bold are the average quantity
102
Exhaust hot air from spray tower (OC)
115 125 103 128 106 116 133 145 101 108 113 106 123 140 108 118
Coldair From tower base, (m/s)
10.2 10.8 9.3 10.9 8.3 8.8 9.7 9.6 10.2 8.9 9.8 10.7 10.1 10.4 9.5 9.81
Exhaust air from spray tower (m/s)
Induce fan surface temperature
11 11 12 9.3 10 13 12 11 12 10.7 12 11 11 12 11.5 11.3
147 140 164 175 178 164 155 161 171 163 146 162 171 179 173 161.33
(OC)
Dearator
surface temp. (OC)
Boiler feed water (OC)
43 39 38 43 46 42 42 38 43 37 40 41 44 38 42 41.06
72 69 78 66 73 69 67 50 71 64 68 57 63 73 65 67
Appendix 5 - Steam Pipe Capacities Pounds per hour of saturated steam at 7 bar and in pressure drops per 100 feet of pipe Steam at 7.0 bar Pressure Loss Pipe size
1/2
1.00
1.5
¾
65
100
125
1
130
200
250
1-1/4
290
400
500
1-1/2
400
600
750
2
800
1,200
1,500
2-1/2
1,300
2,000
2,400
3
2,300
3,400
4,000
4
4,600
7,000
8,400
6
13,000
21,000
25,000
8
27,000
42,000
50,000
10
50,000
75,000
90,000
Notes on the use of the steam pipe capacity chart given above: 1. The column headings 1/4,1/2,1, etc refer to the pressure drop, in pounds per square inch for 100 feet of pipe or equivalent piping. 2. When three columns are given from which to choose, the highest may be used fro branch runouts, the middle for average main runs and the lowest for special cases. 3. A safety rule to follow is that the total pressure drop throughout a main run of 5% to 10% of the available boiler pressure may usually be tolerated [46].
103
Appendix 6- Standard Requirements for Detergents in Ethiopia Ser.
Characteristics tested
Standard Requirements
No.
(%)
1
Moisture and volatile matter, % by mass
15.0 max
2
Ethanol – insoluble matter, % by mass
76.0 max
3
Phosphates content, % by mass
10.0 min
4
Hydrogen-ion concentration measured in pH
9 to 11
5
Non – detergent organic matter, % by mass
6.0 max
Remark: The result for phosphate content is calculated as the total phosphorus expressed as tri poly phosphate percent by mass of the ethanol – insoluble matter.
Source: Quality and Standards Authority of Ethiopia test result notification sheet for RSD (2007)
104
ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES FACULTY OF TECHNOLOGY CHEMICAL ENGINEERING DEPARTMENT ENVIRONMENTAL ENGINEERING PROGRAM
Cleaner Product ion Opport unity Assessment of Soap and Detergent Factory: the case of Repi Soap and Detergent S.Co.
BY: Mulugeta Yilma Tsegayea
Approved by the Examining Board:
_Dr. Ing. Zebene Kifle
___________________
Chairman, Department’s Graduate Committee _Dr. Ing. Nurelegne Tefera
___________________
Advisor _Dr. Ing. Belay Woldeyes Internal Examiner
__________________
