PROJECT REPORT ON
“ETHANOL PRODUCTION” AT
PATIALA DISTILLERS & MANUFACTURERS Ltd.
(June 4 to July 18, 2012) UNDER THE GUIDANCE OF
SUBMITTED BY
R.K. SHAH
KINSHUK SEMWAL
DISTILLERY MANAGER
B.E. THIRD YEAR
PATIALA DISTILLERY
Roll No. 101181002
DEPARTMENT OF CHEMICAL ENGINEERING THAPAR UNIVERSITY, PATIALA
PREFACE This Project Report has been prepared in partial fulfilment of the requirement for the Subject: Practical Studies of the programme B.E. Chemical Engineering (5th semester) in the academic year 2012-2013. For preparing the Project Report, we have visited the distillery during the suggested duration for the period of 6 weeks, to avail the necessary information. The blend of learning and knowledge acquired during our practical studies at the company is presented in this Project Report. The rationale behind visiting the distillery and preparing the Project Report is to study the technical aspects of industry. The Project Report starts with the basic concepts of ethanol production. The information presented in this Project Report is obtained from sources like Company Personnel, Company Websites, Other Websites, Company Reports, and Other Literature.
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PREFACE This Project Report has been prepared in partial fulfilment of the requirement for the Subject: Practical Studies of the programme B.E. Chemical Engineering (5th semester) in the academic year 2012-2013. For preparing the Project Report, we have visited the distillery during the suggested duration for the period of 6 weeks, to avail the necessary information. The blend of learning and knowledge acquired during our practical studies at the company is presented in this Project Report. The rationale behind visiting the distillery and preparing the Project Report is to study the technical aspects of industry. The Project Report starts with the basic concepts of ethanol production. The information presented in this Project Report is obtained from sources like Company Personnel, Company Websites, Other Websites, Company Reports, and Other Literature.
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ACKNOWLEDGEMENT It was indeed an opportunity for us to visit “Patiala Distillers & Manufacturers Ltd” and prepare a Project Report on the same during the programme B.E. Chemical Engineering (3 rd year). During our visit to the company for preparing this Project Report, we learnt many interesting things about the company, along with the aspects of insurance industry as a whole. Preparation of such kind of report, which is based on secondary information, requires data gathering from many sources like Company Personnel, Company Websites, Other Websites, Company Reports, and Other Literature. We are thankful to Mr. R.K. Shah who permitted us to visit the company and allowed us to prepare the Report. We are also thankful to the Departmental Heads of the company, who provided us the required information. Moreover we thank all those who supported us directly or indirectly in preparing this Report, without whose assistance, preparing this Report might have been much difficult for us. We would like to express our gratitude to Mr. Rakesh Kumar Gupta for their valuable guidance and help in the preparation of this Report. At last but not least, we are thankful to all our friends and other people, who w ho helped us in preparation of this Project Report.
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DECLARATION I hereby declare that the project entitled “ ETHANOL PRODUCTION” submitted for the B.E. Degree is my original work and the project has not formed the basis for the award of any degree, associateship, fellowship or any other similar titles.
Signature of Student: Name of the Student: Kinshuk Semwal Place: Patiala Date: 02.08.2012
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ABSTRACT The main target at the distillery is to produce ethanol efficiently using molasses and grain (wheat and rice). Ethanol is produced using fermentation (anaerobic). The microbe used for this purpose is Saccharomyces cerevisiae (yeast). Before fermentation inoculum is grown in a sterilized pre-fermenter (upstream). After the fermentation different constituents are separated using distillation (downstream). Then these constituents are subjected to blending by adding flavors. After it these different products are kept for maturation to have different tastes and color according to the quality needed. The different products obtained are packed in bottles in bottling and packaging section. The spent media (after fermentation) is subjected to ETP (primary and secondary) section before it is being discharged in nearby fields where it is used as fertilizers by the farmers.
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CONTENTS 1. INTRODUCTION 2. VARIOUS UNITS AT PDM 3. BOILER SECTION Introduction
Page no. 06 07 08
Process 4. FERMENTATION Introduction Grain Spirit Plant Fermentation from Molasses Process parameters Working 5. DISTILLATION Introduction Theory Equipments Maturation Blending
14
29
Filteration 6. BOTTLING AND PACKAGING Working Brands at PDM 7. EFFLUENT TREATMENT PLANT Introduction Some terms Primary Treatment Secondary Treatment 8. CONCLUSION 9. REFERENCES
6
51
57
65 66
7
1.
INTRODUCTION
Ethanol has been used by humans since prehistory as the intoxicating ingredient in alcoholic beverages. Dried residues on 9000-year-old pottery found in northern China imply the use of alcoholic beverages even among Neolithic peoples. Its isolation as a relatively pure Compound was first achieved by Islamic alchemists.Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808, Nicolas-Theodore de Saussure determined ethanol's chemical formula. Ethanol was first prepared synthetically in 1826, through the independent efforts of Henry Hennel in Britain and S.G. Serullas in France. Michael Faraday prepared ethanol by the acid-catalyzed hydration of ethylene in 1828, in a process similar to that used for industrial ethanol synthesis today. With the advent of distillation, which appears to have been discovered first in ancient Arabia, people were able to obtain beverages with higher ethanol content. In its strictest sense, fermentation (formerly called zymosis) is the anaerobic metabolic breakdown of a nutrient molecule, such as glucose, without net oxidation. Depending on which organism it is taking place in, fermentation may yield lactate, acetic acid, ethanol or other reduced metabolites. Normal fermentation processes typically cease when a beverage has achieved an alcohol content of 10 to 15 percent. Distillation is the process by which ethanol is boiled from the fermented mixture and captured, producing a liquid with a much higher concentration of alcohol.
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2. Various Units at Patiala
Distillery
1.
Boiling Section
2.
Fermentation Section
3.
Distillation Section
4.
Bottling Plant
5.
Laboratories ( R & D and Distillery Lab)
6.
9
Effluent Treatment Plant
3. BOILER SECTION
STEAM BOILER UTILISING RICE HUSK FUEL After bagasse, rice husks are probably the largest mill-generated source of biomass available for energy use. large quantities of rice husks are normally available at the rice mills can be put to use for comparatively larger energy applications, like generation of steam for process heating applications.
10
Small process industries in northern India, like Distillers, paper mills, fertilizer industries etc have started using rice husk, as a substitute for firewood and coal, as a fuel in their boilers to generate steam. In recent times, The development of compact, fluidized bed process steam boilers by the boiler manufacturers led to more efficient and environment-friendly utilization of this widely available bio-fuel resource. This, on the one hand, led to the sustainable use of rice husks, which was once a disposal problem, and on the other hand, enabled the process industries to meet their energy needs in a more cost-effective manner. Some of the characteristics of such fluidized bed boilers include: •
the ability to burn low-grade biomass fuels, due to the high thermal inertia and high turbulence of the fluidized bed.
•
the high combustion efficiency, due to the turbulent mixing of the fluidized bed and the long residence time of the fuel in the furnace.
The fluidised bed combustion technology gives a high efficiency of the order of 75-80%, the other advantages are quick start-up, low pollution, simple operation and maintenance.
11
THE PROCESS
First the rice husk is loaded manually on the conveyer trolleys which carries it sequentially to the top of the Thermax heating chamber. The chamber is a long, cylindrical and thick walled furnace in which combustion of fuel takes place. The predominant system used in this process indirect heating, with a heat transfer media. The media undergoes phase change in the process of heating. The most commonly-used heat transfer medium is water, which is converted to steam in the boilers. As the husk is fed from the top, an 8 inch thick layer of husk bed is deposited at the bottom of the chamber, over the set of pipes known as air distribution ducts. These ducts have a number of fluidized nozzles which throw the hot air upwards. These ducts are fed with hot air, generated via hot air generator initially, which may be fueled by burning coal.
12
As the hot air is blown at high pressures and temperatures of about 3600C- 8000C through the fluidized nozzles, the dry husk forms a fluidized bed inside the entire heating chamber. Now the biogas, comprising of primarily methane, is fed into the chamber from one side. This is the same methane gas, which was produced in the Biodigestors I & II. Thus, the biogas acts as a fuel, and when combined with hot air leads to ignition and a blast of fire, inside the furnace.
STEAM GENERATION
The steam and water system absorbs the heat generation in the furnace to turn water, under pressure, into superheated steam. Water flows counter current in the furnace to turn water, under pressure, into superheated steam. For production of steam, an evaporator is fixed at the top of the fluidized bed, inside the heating chamber. This evaporator consists of a number of concentric pipes of uniform diameter, through which water at 700C- 900C is fed. Due to high temperatures attained in the furnace, the liquid in these pipes is evaporated into superheated steam at 2480C, which is then extracted by insulated pipes and used in steam distillation of alcohol, produced after fermentation. Flue gas system The flue gases, rising from the furnace, reach the secondary super heater section then pass across the primary super heater section. The boiler heating surface is specially designed to cool the gases containing dust or husk. The flue gases leave the furnace at a temperature of about 9440C from the spacious furnace zone. At this stage, the flue gas contains dried or burnt husk and dust particles. On coming in contact with relatively cold zones, they adhere to the surfaces. Then, as the flue gas passes out of the furnace area the gases are cooled to around 520 0C before entering the exit screen. At a lower temperature than the above mentioned the particles are entrained in the gas flow. The flue gas is passed through boiler bank which partially removes ash. Then the gases flow through the Electrostatic Precipitator wherein, the burnt ash is collected into the large frustum
13
shaped precipitator chamber. The precipitator collects the fly ash from the flue gases and conveys to the ash mixing tank. Partial and uneven combustion of husks in the furnaces of the boilers also lead to smoke emissions. Also, the disposal of partially burned husks and ash creates environmental hazards. Hence it becomes necessary to collect the burnt particles separately, and emit the smoke out of the system using the Induced Draft Fan. Thus, finally the ‘Indigestive Drops’ are exhausted via long chimneys, into the atmosphere.
Conveyor for loading husk
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Induced draft fan for exhaust
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4. FERMENTATION
INTRODUCTION: Fermentation is a bio-chemical reaction where the substrate is converted into desired product with the help of micro-organism which may be yeast, Mould or bacteria and the enzyme present in the Microorganism actually acts in the reaction.
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Reaction:
C6 H12 O6
------>
2 C2 H5 OH
(sugar)
+
2 CO2
(alcohol)
The yeast Saccharomyces cerevisiae that is used for the culture for Alcohol
fermentation
is
having
two
kinds
of
enzymes,
one’s
INVERTASE and other is ZYMASE. Invertase converts sucrose to invert sugar and Zymase converts invert sugar into Ethyl Alcohol.
Fermentation is a dynamic process involving a series of reactions. These are:
(i)
Enzymes
added
after
cooling
continuous
to
convert
the
gelatinized starch to dextrin’s and fermentable sugars. (ii)
The yeast metabolizes sugar to acetaldehydes and then to
ethanol. The cycle is known as Glycolysis. The lactic acid bacteria produce small amounts of a variety of products, some of which are volatile and contribute to the congeners in the distillate.
Molasses is transported in the cells via specific carrier proteins called Permeases where it is hydrolysed into 2 molecules of glucose. The Permeases are substrate and require metabolic energy for operation.
C6H12O6 --> 2 C2H5OH +2 CO2 + 2 ATP + heat
Two moles of ATP (Adenosine Triphosphate) are also produced which are 17
used
to supply
energy
for
cell maintenance
and
growth.
Theoretically conversion of 1gm of glucose via fermentation yields 0.511grms of ethanol. This theoretical value is never obtained due to carbohydrate utilization for cell maintenance, growth and formation of small amounts of glycerols and higher alcohols.
Fermentation efficiency also depends upon factors such as yeast strain and environmental parameters. In practice efficiency is 60-80%. An increase in temp within a certain range increases activity. The condition in Fermentation vats are such obtained so as to avoid bacterial action. During a normal Fermentation heat is produced from active yeast growth and metabolism which causes a rise in temp. Then this temp rise can drastically affect yeast metabolism and ethanol. An average upper limit temp for growth is around 40’ C with an optimum temp of about 30’C. Increased heat tolerances are obtained with media containing oleic acid. The maximum concentration of ethanol that yeast can produce depends upon the yeast strain used. In general, yeast cell growth is inhibited around 10 to 12% wt/vol. ethanol while 20% ethanol will terminate cellular metabolism.
Ethanol Fermentation With Yeast:
The organisms of primary interest to industrial operations in fermentation
of ethanol
include
Saccharomyces
cerevisiae,
S.
uvarum, Schizosaccharomyces pombe, and Kluyueromyces sp. Yeast ,
under anaerobic conditions, metabolize glucose to ethanol primarily by way of the Embden-Meyerhof pathway. The overall net reaction involves the production of 2 moles each of ethanol, but the yield 18
attained in practical fermentations however does not usually exceed 90 – 95% of theorectical. This is partly due to the requirement for some nutrient to be utilized in the synthesis of new biomass and other cell maintenance related reactions. A small concentration of oxygen must be provided to the fermenting yeast as it is a necessary component in the biosynthesis of polyunsaturated fats and lipids. Typical amounts of O2 maintained in the broth are 0.05 – 0.10 mm Hg oxygen tension. The relative requirements for nutrients not utilized in ethanol synthesis are in proportion to the major components of the yeast cell. These include carbon oxygen, nitrogen and hydrogen. To leaser extent quantities of phosphorus, sulfur, potassium, and magnesium must also be provided for the synthesis of minor components. Minerals (i.e. Mn, Co, Cu, Zn) and organic factors (amino acids, nucleic acids, and vitamins) are required in trace amounts.
Yeast are highly susceptible to ethanol inhibition. Concentration of 1-2% (w/v) are sufficient to retard microbial growth and at 10% (w/v) alcohol, the growth rate of the organism is nearly halted.
Fermentation at PDM is done through two ways: 1) Grain spirit plant (From wheat or rice flour) 2) Fermentation from Molasses
Grain Spirit Fermentation Plant 19
Nowadays, along with the use of molasses as a sugar source for fermentation, Distilleries are using grains, which are a potential source of fermentable sugars. For this, first the starch present in the grains has to be extracted and then converted into glucose either by acid hydrolysis, or by enzymatic hydrolysis. The process/methodology applied, is described below sequentially. Screening: The first step is screening of grain. There are two meshes, one for the dust particles and other for foreign particles. Size of the dust mesh screen is 0.5mm and of the other 2.4mm. Once the screening is over, grain is stored in the tank called ‘SILO’. Loading of grain: The grain (atta) is loaded into a vertical conveyer which carried it to a large Hopper (or Chute). The Hopper is a vertical or inclined path, channel, or passage through which objects are moved by means of gravity. It has some additional width and depth to provide a volume for temporary storage of material(s). The bottom of the hopper/ chute typically has a mechanism to control the flow of materials (usually a stop valve), thus allowing them to be metered out at the desired rate. From the hopper, the grain is carried to the Grinding section. Mashing: Once grinding is done, the milled grain is mixed with hot water, in a ratio of 90-10 upto 50-50, (notably at 45°C, 62°C and 73°C), to allow enzymes to break down the starch in the grain into sugars. This section is also referred as PRE COOKER. The purpose of the mashing operation is to (1) mix the proper proportions of grains, (2) increase the availability of the starch for enzyme action, and (3) convert the starches into fermentable sugars. Mashing is done in a vessel called a mash tun, which is equipped with a means of agitation for mixing and is either jacketed or contains coils for heating and cooling. In mashing, the starch cells of the grain, enclosed in their own protective coatings, are broken to allow wetting and liquefaction of the entire starch mass. After pre-cooking, the slurry is stored in storage tank, wherein pH is maintained at 6.0-6.4.
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Gelatinisation: This process involves the dissolution of the nanogram-sized starch granules to form a viscous suspension. This is achieved by heating starch with water, and occurs necessarily and naturally when starchy foods are cooked. For this purpose, a JET COOKER is installed right after the balance tank, wherein temperatures up to 110 0C are attained due to steam heating. Liquefaction: Gelatinised starch is then readily liquefied by partial hydrolysis with enzyme Biotemptase (α- amylase, added in ¼th ratio) in the LIQUIFICATION TANK. This enzyme cleaves α-1,4 oligosaccharide links in starch, to yield larger sugar units. Liquefaction is carried out for approximately 2hrs at 950C. This process leads to only 4% conversion of starch to glucose. Saccharification: This process involves further production of glucose via enzymatic hydrolysis. During the saccharification of liquefied starch, the larger sugar units produced during liquefaction are broken down to glucose, using glucoamylases (Spirizyme), which cleave α-1,4-oligosaccharide and α-1,6-oligosaccharide links to yield β-glucose. Here 18-20% 0 conversion of starch of is achieved at 88-90 C, and retention time is 67 hrs. Once the above processes are done, the temperature of slurry is further reduced to 22-24 0C via heat exchangers. Then the thick liquid containing sugars is fed to the pre fermenter.
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The process
Fermentation from Molasses Molasses is used as nutrient and acts as reducing sugar. Here the yeast
is grown
in laboratory applying the
strain improvement
technique used at PDM. The various stages in process of going from lab to production fermenter are: 1) Seed fermenter 2) Prefermenter 3) Production/Industrial fermenter
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1) Seed Fermenter: Inoculum produced in lab is transferred to grow in sterilised seed fermenter where a specific nutrient level is maintained. Basically we are preparing our inoculum to adapt to harsh conditions and nutrient level in fermenter. In seed fermenter the pH is approximately 4.7 and temp of 360C. At PDM we have four vessels basically working as seed fermenters, But only two are working at a time. The capacities of these vessels are 500,1500,2000,2500 Bulk litres. Cell concentration in seed fermenter reaches to 300 cell/ml.
2) Prefermentor: The inoculum grown in sterile environment in the seed-fermenter is transferred to the prefermenter (50,000 bulk litres capacity) after growing cell mass to a specified amount. In prefermenter the cell is allowed to grow to its maximum size by supplying all the necessary nutrients required for its growth. Basically the process of growing inoculum(yeast) first in lab, then in seed fermenter than transferring it to pre-fermenter is to allow cell to adapt slowly to the coniditons prevailing in the fermenter. Here also we get less than 2% yield of alcohol. Here pH of 4.5(approx) and temp of 36 0C is maintained.
23
PROCESS
Prefermenter
The figure is showing an internal look of a pre-fermenter. It is containing SPARGERS for supply of sterilized air to carry out aerobic
24
fermentation. Here we grow the inoculum to its maximum size, to be able to feed the inoculum to the production fermenter.
3) Industrial fermenter The final alcohol production is done in industrial or production fementer. The production fermenter of capacity 3,50,000 bulk Litres capacity. All pipelines and production fermenter is steam sterilized before running for next batch. ph here is more than 4. 7 and normal temp of 36-380C. The sum of glucose, fructose, and sucrose, i.e. the total sugar content or Total Dissolved Sugar (TDS) in the molasses, sets the potential alcohol yield. Theoretically, 100 kg sugar (glucose, fructose) will yield approximately 51 kg or 64.5 l alcohol. Less than theoretical yield is caused by sugar consumption by the yeast, incomplete fermentation, the formation of fermentation side products (e.g. fusel alcohols), and alcohol loss in the distillation process. For these reasons a yield of only 56 liters of pure alcohol per 100 kg glucose or fructose is generally realized in practice. Starch is a polymer composed of repeating units of glucose; therefore, it is necessary to break the starch down to the basic glucose unit for the yeast to convert the sugar into alcohol. This process is called hydrolysis and can be accomplished by use of enzymes or acids.
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PROCESS FLOW PRESERVED SLANT CULTURE ↓
SHAKER FLASK [ 4-5 % OF FREEZE CULTURE] ↓
SEED FERMENTER – 1 [10% OF WORKING VOLUME = INOCULUM ADDED] ↓
SEED FERMENTER – 2 ↓
PRE-FERMENTER ↓
PRODUCTION FERMENTER
PROCESS PARAMETERS A)
FILLING STRATEGY:
Before inoculation 300liters to 2000liters dilute molasses of specific gravity 1.050 is taken. The specific gravity gradually increases.
B)
pH:
The pH in fermentation is maintained at 2.2
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C)
NUTRIENTS:
Generally di ammonium phosphate (DAP) and urea are used as nutrients. These are used so as to form aminpo acid to give energy and to carry out propagation faster.
D)
TEMPERATURE:
Temperature of the material in the fermenter is 32 to 34’ C.
E)
PRESSURE:
The process is carried out at Normal Pressure
F)
ANTIFOAM: 25% Silicon antifoam was prepared to control the foam formation in the pre-fermenter and the fermenter.
WORKING In Batch Fermentation, the yeast culture are taken from laboratory and then putinto yeast vessel (100 lt) where it is fed with dilute molasses and is propagated. Then it is passed to next yeast vessel (1000lt) where it is also fed with dilute molasses for further propagation.
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Fermentation is anaerobic in nature and through the degradation of molasses by yeast( Saccharomycies cerevisiae) we get our desired product. Before operating any batch all reactors and pipelines are steam sterlised. We get alcohol and carbon dioxide during the fermentation. CO2 is continously ejected from top of the fermenter. The CO2 ejected also contain some content of alcohol that it carry with it self. We pass the CO2 from a tank and it is washed with water. And thus we extract the ethanol content from the CO2 and we send this CO2 to nearby plants which uses it for dry ice. Our fermentation product-Ethanol is extracted from the bottom of the fermenter.
REACTION
C6 H12 O6
------>
2 C2 H5 OH + 2 CO2 +Heat
ADVANTAGES OF BATCH FERMENTATION:
Contamination and Salts don’t recycle.
Cleaning and Sterilization is regularly maintained.
Any kind f mishandling leads to minimum losses.
DISADVANTAGES OF BATCH FERMENTATION:
While transferring the material, there is some loss of material and thus efficiency reduces.
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As the losses increases efficiency decreases.
Time taken is more during Batch Fermentation.
PHYSICAL
AND
CHEMICAL
COMPOSITION
SUGARCANE MOLLASSES Quantity
Measure
pH
5.3
Sucrose % (W/W)
33.78
Reducing Sugar % (W/W)
26.96
Total Sugar % (W/W)
60.94
Sulphated Ash % (W/W)
9.46
K (ppm)
2.68
Mg (ppm)
0.98
Ca (ppm)
0.88
Na (ppm)
0.06
B (ppm)
410
Fe (ppm)
158
Mn (ppm)
57
Cu (ppm)
28
Zn (ppm)
11
Ni (ppm)
1
Pb (ppm)
0.75
Co (ppm)
0.54
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OF
Metabolic Byproducts of Alcoholic Fermentation SECONDARY BYPRODUCTS 2,3-butanediol acetoin diacetyl higher alcohols these fermentation byproducts are part the cell building metabolism (byproducts of AA synthesis valine, leucine, isoleucine) Sulfur compounds (SO2, H2S, mercaptans,…)
Nutrient Limitation Nitrogen (amino acids, short peptides, ammonia) Pi (H3PO4) nicotinic acid (B-vitamin) important for NAD (nicotinamid adenine dinucleotide) thiamin (B1) (pyruvate ---> acetaldehyde), lack: accumulation of pyruvate and ketoglutarate
5. DISTILLATION
30
INTRODUCTION Distillation, process of heating a liquid until its more volatile constituents pass into the vapor phase, and then cooling the vapor to recover such constituents in liquid form by condensation. The main purpose of distillation is to separate a mixture of several components
31
by taking advantage of their different volatilities, or the separation of volatile materials from nonvolatile materials. In evaporation and in drying, the purpose usually is to obtain the less volatile constituent; the more volatile constituent, in most cases water, is discarded. In distillation, on the other hand, the principal object of the operation is to obtain the more volatile constituent in pure form. The removal of water from glycerin by vaporizing the water, for example, is called evaporation, but the removal of water from alcohol by vaporizing the alcohol is called distillation, although similar apparatus is used in both cases.
DISTILLATION IN ‘PDM’
32
If the difference in volatility (and hence in boiling point) between the two constituents is great, complete separation may be easily accomplished by a single distillation. Seawater, for example, which contains about 4 percent dissolved solids (principally common salt), may be readily purified by vaporizing the water, condensing the steam thus formed, and collecting the product, distilled water. This product is, for most purposes, equivalent to pure water, although actually it contains some impurities in the form of dissolved gases, the most important of which is carbon dioxide.
THEORY OF DISTILLATION: In the simplest mixture of two mutually soluble liquids, the volatility of each is undisturbed by the presence of the other. In such a case, the boiling point of a 50-50 mixture, for example, would be halfway between the boiling points of the pure substances, and the degree of separation produced by a single distillation would depend only on the vapor pressure, or the volatility, of the separate components at this temperature. This simple relationship is called as the Raoult's Law. Raoult's law applies only to mixtures of liquids that are very similar in chemical structure, such as benzene and toluene. In most cases wide deviations occur from this law. Thus, one component is only slightly soluble in the other, its volatility is abnormally increased. In the example above, the volatility of alcohol in dilute aqueous solution is several times as great as predicted by Raoult's law. In extremely concentrated alcohol solutions, the deviation is even more striking: The distillation of 99 percent alcohol produces vapor that has less than 99 percent alcohol.
For this
reason, alcohol
cannot be
concentrated by distillation beyond 97 percent, even by an infinite number of distillations. 33
At PDM, there is distillation plant of Rectified Spirit of capacity 60 KL/day. But the plant is generally operated at 40-50 KL/day. Distillation are of the different types. The main types of distillations are:1. Batch Distillation 2. Fractional Distillation 3. Steam Distillation 4. Vacuum Distillation 5. Azeotropic Distillation 6. Extractive Distillation Out of these, fractional distillation is the most common type of distillation or rectification. The distillation used at PDM is also fractional distillation. The principle of the Fractional distillation is:If a portion of the distillate in distillation of ethyl alcohol is returned from the condenser and made to drip down through a long column onto a series of plates, and if the vapor as it rises on its way to the condenser is made to bubble through this liquid at each plate, the vapor and liquid will interact so that some of the water in the vapor condenses and some of the alcohol in the liquid vaporizes. The interaction at each plate is thus equivalent to a redistillation, and by building a column with a sufficient number of plates, 95 percent alcohol can be obtained in a single operation. Moreover, by feeding the original 10 percent alcohol solution gradually at a point in the middle of the column, virtually all the alcohol may be stripped from the water as it descends to the lowest plate, so that no alcohol need be wasted.
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This process, known as rectification, fractionation, or fractional distillation, is common in industrial usage, not only for simple mixtures of two
components
(such
as
alcohol
and
water
in
fermentation products, or oxygen and nitrogen in liquid air) but also for highly complex mixtures such as those found in coal tar and petroleum. The only disadvantage of fractional distillation is that a large fraction (as much as one-half) of the condensed distillate must be refluxed, or. returned to the top of the tower and eventually boiled again, and more heat must therefore be supplied. On the other hand, the continuous operation made possible by fractionation allows great heating economies, because the outgoing distillate may be used to preheat the incoming feed. Fractional Distillation is most widely used distillation at industrial level. At PDM, fermented wash of composition 7% alcohol and 93% water are fed for the distillation to purify the ethanol upto 96.8%. Ethanol can be purified upto 96.8% by simple distillation but cannot be further purified by simple distillation. After that the azeotrope forms
and
azeotropic
distillation
is
required
for
the
further
purification. Benzene is the solvent that is needed for the break up of the azeotrope. At PDM, feed introduced in the distillation column is at the bubble point
i.e. saturated liquid. Fermented wash is entered at 74-750C,
after coming from fermentation, the feed is heated in spiral heat exchangers to temp. of 74 0C.
EQUIPMENTS
35
At PDM, tray towers are used for the effective separation. Tray towers are particularly useful as compared to the packed towers when fluctuations in the vapor or liquid rate may occur or where the major changes in the overall capacity of the column are anticipated. The problems of the poor liquid or gas distribution encountered at various loading capacities with packed towers can be avoided with plate or tray towers. The main parts of the tray columns are:1. Shell and Trays 2. Weirs 3. Downcomers
Shell and Trays: Cylindrical shells are commonly used for the tray columns. The shell may be constructed of short sections that are bolted together or in the form of one long cylinder. Manholes should be provided to give access to the individual trays for cleaning, maintenance and installation. Adequate foundations and tower supports must be provided. Both the corrosion characteristics of the fluids involved and costs dictate the acceptable materials of construction for the shell and trays. Trays are usually made of suitable metal to facilitate fabrication and the shell material can be steel , resin lined steel or any alloy. Supporting beams are used to stiffen the trays, and the trays must be fastened securely to prevent movement caused by gas surges.
Weirs and Down comers:
36
Downcomers for conducting the liquid from one tray to the next tray below may be in the form of circular pipes or segments of the tower isolated from the rising gas by means of vertical or angled plates. Some vapor is entrained in the liquid gas the liquid enters the downcomer, and sufficient residence time should be provided in the downcomer to permit escape of the entrained vapor. A residence time of 5s, is enough to permit release of most of the entrained vapor. The liquid head in the downcomer should not be greater than one half the plate spacing.
TRAY VIEW OF DISTILLATION COLUMN IN ‘PDM’ The depth of the liquid on the tray required for the gas contacting is maintained by an outlet weir, which may or may not be a continuation of the downcomer plate. Straight weirs are the most common; multiple v-notch weirs maintain a liquid depth which is less
37
sensitive to the variations in liquid flow rate The height of the overflow weir is a major factor in determining the head of the liquid on the tray. Although plate efficiency is increased but the pressure drop is more by the high heads.
The type of tray is most important factor while installing the distillation column. The main types of trays are: 1. Bubble Cap Trays 2. Sieve Trays 3. Valve Trays
Bubble Cap Trays
38
Sieve Tray
The most common type and the most efficient tray is the sieve tray because of ease in the handling and less maintenance cost. The bubble cap trays are the efficient trays but the cleaning and maintenance cost of the bubble cap tray is very high, that is why sieve trays are most commonly used for the effective separation. At PDM, sieve trays are used for the distillation of water and ethanol mixture.
39
PROCESS DESCRIPTION: At PDM, there is a distillation plant of Rectified Spirit of 60 KL/day capacity. The Rectified spirit is used to manufacture the IMFL (Indian Made Foreign Liquor). Fermented Wash that is the feed for the distillation mainly consists of ethanol and water but it also contains small fractions of the aldehydes, fusel oil, carbon dioxide, esters etc. These are the main impurities formed during the process of the fermentation. So, these impurities are also removed during the distillation. These fusel oil, Carbon dioxide after treatment are selled to another industries like Pharmeuticals industries. The relative volatility of the mixture is around 2.2 i.e. α = 2.2 .
α
is the major factor that is
required for the distillation. The far is the value of the
α
from 1.0, the
easy is the separation possible.
If the value is near the 1.0 or equal to 1.0 then the mixture is azeotropic mixture and then third entrainer is used to break up the azeotrope. Reflux Ratio is also important factor that is used to maintain the overhead product concentration. At PDM, reflux ratio of 5:1 is generally used.
At PDM, in distillation plant there are five main columns:-
1. MASH COLUMN OR BOILING COLUMN 2. PURIFICATION COLUMN 3. RECTIFIYING COLUMN 4. FAINTS COLUMN 5. METHANOL COLUMN
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MASH COLUMN: Mash column is often known as the Boiling Column. In the mash column, no direct steam is applied but the indirect heating is applied by the vapors of the rectifying column. By this manner, steam is saved in the boiling column. The height of the boiling column is around 20m. The trays used in that column are the sieve trays for the effective separation. The boiling column is operated at total vacuum. Vacuum pumps are used to create the vacuum in the mash column. The vacuum is created because pressure is directly proportional to the temperature and less is the pressure less heating is required to boil the feed. That is why vacuum is created in the boiling column. The boiling point of the fermented wash is around 105 0C. But due to the vacuum it boils at around 75 0C.Therefore it is commonly known as the boiling column. Feed enters at boiling column at around 7% purity of
ethanol and after the distillation the purity of the ethanol is around 71% or 25- 30 Over Proof. In the mash column, 24 trays are used. 41
The temperature at the bottom of the column is around 75 0C and at the top of the column, the temperature is around 60 0C. From the mash column, the fed is sent to the purification column.
DISTILLATION COLUMNS IN ‘PDM’
PURIFICATION COLUMN: From the mash or boiling column, ethanol of purity 71% is fed to the purification column. In the purification column, soft water is added to the mixture to increase the relative volatility of the mixture and making the further separation easy. Direct steam is applied to the purification column. By addition of the soft water, relative volatility of the mixture increases and the impurities settle down and sent to the faints column. The height of the purification column is around 15 m. The pressure at the bottom of the column is around 0.47 mm Hg and pressure at the top is around 0.3 mm Hg. After increasing the relative volatility the mixture is fed to the rectifying column. Purification column have around 32 trays.
RECTIFYING COLUMN: The spirit obtained from the purification column is fed to the rectifier column to increase the purity of the ethanol. Direct steam is supplied to the rectifying column. Sieve trays are used in the rectifying column. Rectification column has 56 trays for the effective separation. In the rectifying column, purity of the ethanol is taken upto the 96.8% (v/v) or 69-70 over proof. The temperature at the bottom of the column is
42
around 1050 C and the temperature at top is around 95 0 C. Pressure at the top of the rectification column is 0.49 mm Hg and the pressure at the bottom is around 0.73 mm Hg.
In this column, there is no cross flow of the liquid, the liquid flows across the tray and vapors passes counter currently through the perforations of the tray. The spirit obtained from the rectification column is 96.8% (v/v) purity. From the vapors of the rectification column, indirect steam is applied to the mash column. This ethanol is sent to the condensers , generally shell and tube type condensers are used for the condensation of the ethanol. A part of the overhead product is sent back to the column as the reflux for the increase the concentration of overhead product. Impurities like aldehydes, esters and fusel oil are sent to the faints column. Spent leese that majority consists of water is sent to the E.T.P. plant.
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CROSS-SECTION VIEW OF SHELL & TUBE HEAT EXCHANGER
FAINTS COLUMN: All the impurities from the rectification column and the purification column collects in the faints column. Impurities like methanol, aldehydes, esters fusel oil collects in the faints column. From the faints column, methanol is sent to the methanol column and aldehydes are collected in the separate column. Fuse oil is used in pharmaceutical industry therefore it is purified in the decanter and then collects as the pure fusel oil.
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MAIN PROBLEMS IN THE DISTILLATION COLUMNS:
The main problems during the distillation arise due to improper flow rate of liquid or vapors. The main problems are faced during the operation of the distillation column are:-
1. Flooding 2. Priming 3. Weeping 4. Coning 5. Dumping
High pressure drop directly lead to the condition of the flooding. With a large pressure difference in the space between the trays, the level of liquid leaving a tray at relatively low pressure and entering one of high pressure must necessarily
assume an elevated position in the
downcomer. As the pressure diff. is increased due to increased rate of flow of either gas or liquid, the level of downcomer will rise further to permit the liquid to enter the lower tray. Ultimately the liquid level may reach the tray above. Further increase in flow rate then aggravates the condition rapidly and liquid will fill the entire space between the trays. Then tower is said to be flooded.
If liquid rates are too low, the gas rising through the openings of the tray may push the liquid away and contact of vapor and liquid is poor. This condition is called the coning.
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If vapor rate is too low, much of the liquid may rain through the perforations of the tray.
This condition is called the weeping.
High gas velocities may lead to a condition of priming. Here the foam persists throughout the space between trays, and a great deal of liquid is carried by the gas from one tray to tray above. This is condition of entrainment.
MATURATION The last step in whishy production is maturation process when over proofed alcohol from distillation unit is sending to the maturation plant. It is first diluted with demineralized water .After maturation for different time periods, according to the brand, we get the finished product, Spirit which is supplied by distillation unit is 96% pure as it contain some traces of aldebydes, esters, fusel oil etc. which can’t be removed completely after distillation process. As this amount of
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impurities does not make any harmful effect, hence it is considered to be as 100% pure. The spirit is firstly diluted with ‘DM’ water in such a way that the spirit contain 60% (v/v) alcohol.
For this need to check the following things •
QUALITY CHECK OF SPIRIT
•
QUALITY CHECK OF DEMINERALIZED
After this above two combinations is taken in different ratio’s to get different types of alcohol. The product of distillation at 105-125 deg. proof is put into new charred white oak barrels. The filling hold is closed with a populate wood and the barrels are entered in a warehouse.
Barrels liquid volume during storage for several reasons. The main loss of 4% per year is due to evaporation. The optimum temperature for maturation ranges from 21-30 0C that results in a whisky production with the desired flavor. If the temperature increases much over 30 0C, the flavor of the product becomes too woody and resinous. At high temperature and low humidity water migrates through the barrels stores at a faster rate then either ethanol or fusel oil. Therefore, the percentage of these alcohol increases.
The tank where the proof gallons are determined. The whiskies are then blended based on the lab formula. The blends are reduced to a few
tenths
of
the
point
as
on
the
desired
proof
by
adding
demineralized water, The blended material is allowed to ‘marry’ i.e. it
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is held for a time to allow it to become completely mixed and smooth. It is then chill filtered, refiltered and sent to a bathing tank. In PDM, The cost of each barrels is 5000 Rs. (Approx.).Each barrel is of 200 lt. capacity. There are 150-500 barrels which are filled each day. These barrels have the tendency to impart colour to the spirit as there is natural oxidation takes place in the barrels. These Barrels are made up of Oak wood which is imported from Scotland as there are large number of Oak Trees found in Scotland. Maturation takes place for a period of 1 year, 2 year, 3 year, 4 year, 5 year. If it is kept for 12 years then the spirit is converted into Scotch. There is the change in the color of the spirit year after year. i.e. there is increase in darkness from the light yellow to dark yellow.
White
Light yellow
Reddish yellow
Brownish yellow.
In maturation unit the temperature is maintained below 17 0C. There was
automatic
blower system which
work automatically
if the
temperature of the unit increases beyond 170C. The blowers are connected with sensors which measure & indicate the temerature of the unit and command the blowers according to that. We maintain the temperature below 17 0C as the increase in temperature further cause evaporation. After maturation there comes the important section of the maturation unit i.e. Blending unit.
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BLENDING After maturation there is blending unit where flavours are added to the spirit to make the final product. In blending unit there is formulation takes place. Formulation usually takes place by the mixing of the following spirits:-
1. Molasses based spirit 2. Grain based spirit 3. Barley based spirit 4. Malt based spirit 5. Low strength Rum spirit 6. Cane-juice spirit 7. Molasses matured spirit 8. Grain matured spirit
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9. Wetted malt spirit
Blending relates to the secret part of company working. Each lot of whisky is periodically checked for its maturation characteristics such as smooth taste & pleasant aroma. The rate of maturation depends upon the grain bill, geographical location of the warehouse and the location of the barrel with in the warehouse. If the blended product is required, a trail blend is made in the lab. Once the blend is identical to its flavor standard, the proper numbers of barrels of each lot are withdrawn and the barrels are emptied i.e. whisky is cleaned to remove barrel char, The whisky is then pumped to a gauged. In blending some flavors are added and mixed in varying compositions in different types of whiskies.
Blending Flavors 50
Blender
FILTERATION After blending, it is made to pass through the filter in order to remove the bumus, Oak wood content and any of the particulars which are not required etc. In , there are types of filters used:-
(A)HORIZONTAL FILTER (B)VERTICAL FILTER
HORIZONTAL FILTER: It
is mainly used to filter the country liquor. It has a capacity of
filtering 1000 liters once. It has less efficiency i.e. the blended product
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can’t be completely pured after boiling through filter, it has some traces of impurities so the product is passed through the filter which is vertical so as to remove the remaining traces of impurities so as to achieve the final product totally neat & clean and sent for bottling. Filter size is less. There is the choking of the filter after the continous usage of it for 24 hours.
VERTICAL FILTER: It is used mainly to filter Indian made foreign liquor. This is used to remove the impurities even presentaion traces. It has a capacity of filtering 30,000-40000 lt. In single time (once). It has more filteration power and efficiency. It has a filter size in the range of 8 mm-20 mm. It can worth for 10 days continuously without choking.
After the filteration the sample of the spirit ore sent to the lab for the testing of alcohol such that it contain 42.8% v/v or 75° proof. If there is 77 proof then water is added to it so as to make the product 75°proof.
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6. BOTTLING AND PACKAGING
53
WORKING In the bottling unit the final blended spirit is filled in the bottles of different sizes of different brands & packed in the boxes. Bottling takes place in the sequence of steps which takes place on a conveynor. In bott bottli ling ng ther there e is clea cleani ning ng of bott bottle les, s, filli filling ng,, co cork rkin ing, g, labe labelin ling g and and packing. There are some processes like filling, corking, labeling is done by two methods on different conveyors as follows:
A.)
MANUALLY WORKING
B.)
AUTOMATICALLY WORKING
Presently, bottling is done automatically with the help of machines like filling filling machin machine, e, sealin sealing g & labeli labeling ng machin machine e etc. etc. This This increa increases ses the efficiency of the bottling unit and decrease the labor, thus it is directly related to the economy.
There are ONE bottling units in the PDM. In the new Bottling unit where English Whisky run on conveyer. There are 4 conveyors lying parallel to each other which can work at a time depending on the load they (conveyers) are used i.e. they have marked the conveyor for their particular type of whisky usually conveyor work at a speed of 1 rpm. rpm. Speed can be increased or decreased depending upon the load.
First step is washing yard. In washing yard, washing of bottles takes place. Mainly ‘surf’ (detergent) is used for this purpose. Further, steam is also used for washing purpose and this steam is supplied by Boiler section. After washing yard, bottles are placed on the conveyor and they are passed through a small opening of the wall. This wall is act as
54
a fence between the washing yard and rest of the bottling unit. Bottles on the conveyor enter at one end of the wall and exit at other end. There is a blower placed on the other end of the wall which work continuously in the opposite direction. The blower is mainly used to avoid the appearance of germs, insect in the bottles. Blower is run by the rotor which is supplied voltage of 440 V. After the blower action, bottles lying on the conveyor are made to pass through the empty light where the checking of dirt, dust particles takes place and affected bott bottle les s are are repl replace aced. d. This This empt empty y light light is plac placed ed on the the top top of the the cardboard which is designed specially in order to check the presence of
dirt particles under the empty light. This is a manual operation and affected bottles are replaced by the worker and ore sent back to the washing yard. After this section, there comes the main section of the bottling unit. i.e. ‘FILLING’. Filling of the blended spirit into the bottles is mainly done by filling machine and this filling machine is attached to the storage tank i.e. where spirit is stored with the help of pipelines. 55
This filling machine work at a rpm of 100. 100. Atleast 10 bottles are filled in one revolution. There is a vaccum pump placed behind the filling machine which work at a pressure of max. 200kg/cm2 .
Then the bottles on the conveyor are made to pass through the float which is used to avoid the overflow from the bottles. After the float sectio section n there there comes comes sealin sealing g sectio section. n. In this this sectio section, n, sealin sealing g of the bottles is done with the help of sealing cap made up of plastic. Sealing machine is used for this purpose which work at 100 rpm.
After the seating section there is first light placed which is used to check the presence of on dust, dirt particles in the spirit. Thus in this way way affe affect cted ed bott bottle les s are are repl replac aced ed manu manual ally ly.. Then Then,, ther there e co come mes s labeling labeling section, section, in this this sectio section n labeling labeling machine machine which which is used used to impor importt the the label label of co comp mpan any y whic which h indi indica cate tes s the the co comp mpan any y name name,, 56
manufacturing date, over proof, % volume(v/v). Thick gums used for this purpose is:-
a.)
Poly gum
b.)
VR gum
Then there is final inspection i.e. second light which is used to check the presence of the dust particles. There is a Box and packing material department which is placed along with the bottling unit. In this section bottles, box commonly called as a ‘CASE’ is manufactured. There is a stitching machine envolved during the manufacturing of the case. The supply line of box department is attached a head to the conveyor of the bottling unit.The bottles are placed in the case and sealed with the help of ‘labelling tapes’. There are 12 bottles in each case and 48 bottles in each case. PDM has a capacity to manufacture 400-500 case/day. These cases are supplied and stored in the Godown there after loaded on the truck and sent to various part of the country.
POPULAR BRANDS PRODUCED AT PDM 57
LIQUOR SANTRA GADAR COMMANDO XXX RUM WINNER XXX RUM BLENDED WHISKY BLENDED RUM WHISKY DRY GIN EXTRA DRY GIN RUM VODKA (MADE FROM
PROOF
(V/V)%
50° 50° 75° 75° 75° 75° 75° 75° 75° 75° 75°
28.50 34.26 42.80 42.80 42.80 42.80 42.80 42.80 42.80 42.80 42.80
GRAINS) GIN & LIME 42.80 75° Both country and foreign liquor are produced at PDM
7. EFFLUENT TREATMENT PLANT 58
Introduction The effluent treatment plant in a distillery plays a crucial role in protecting the ecosystem, by controlling and treating the spent effluent, and disposing it in an appropriate manner, as per environmental norms. The untreated waste, coming out of the distillation house not only contains hazardous chemicals, but also has a high microbial content (cell mass), which is too unsafe to be readily disposed into the soil or any water body. Lowering of pH value, increase in organic load, depletion of oxygen content, destruction of aquatic life are some of the major pollution concerns. The role of the effluent treatment plant in the Distillery is not just to make industrial wastes compatible to be disposed into the 59
environment, but also to generate biogas, which can subsequently be used as a fuel. That is, bio-conversion of organic wastes in the liquor into CO2 and methane gas. The effluent coming out of the distillation house is called Spent Wash. Spent wash, also known as spent broth, is the left over liquor after all the spirit has been recovered or extracted via distillation process. This liquor has very high BOD and COD of approximately 1,00,000mg/l along with very high amounts of potassium, calcium, chloride, Sulphate etc. Effluent Quality standards for Distilleries: Under environmental protection act of 1986, the Govt. of India has specified Minimum National Standards(MINAS) for industries taking into account the characteristics of efflrent based on which the effluent from distilleries should have pH between 5.5-9.0, suspended solids 100mg/l, and a max BOD level of 100mg/l.
Significance of B.O.D : Biological Oxygen Demand (BOD) is one of the most common measures of pollutant organic material in effluent. BOD indicates the amount of putrescible organic matter present. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water. Dissolved oxygen (DO) is consumed by bacteria, when large amounts of organic matter from sewage or other discharges are present in the water, which makes the water unfit to be discharged into water bodies. BOD test is a bioassay procedure that measures the amount of oxygen consumed by living organisms while they are utilizing the organic matter present in waste, under conditions similar in nature. *BOD analysis was not applied in Patiala Distillers. Volatile Fatty Acids (VFA): These are short-chain fatty acids like acetic, propionic, and butyric acids which, apart from their presence in some foods, are produced by bacteria from undigested starch and dietary fibre. To some extent they can be absorbed and used as a source of energy. It is these acids that are actually converted into methane in the bio-digestor. Therefore higher the availability of VFA in the spent wash, more is the biogas produced. 60
To check the VFA content in the spent wash1. take 250ml of distilled water in a conical flask and add 1ml of sample (spent wash). 2. Transfer 20ml of this sol. into a round bottom COD flask. 3. Add 10ml of 0.25N K2Cr2O7 and a pinch of Mercuric Sulphate (catalyst). 4. Now add 30ml of H2SO4 and put the COD flask over heater for 2 hours. Significance of C.O.D : The chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in effluent. It is expressed in milligrams per liter (mg /L), which indicates the mass of oxygen consumed per liter of solution. It may also be expressed in part per million (ppm). In an effluent treatment plant, the spent wash is treated by the following treatments: PRIMARY TREATMENT SECONDARY TREATMENT From the distillation house, the spent wash having a high BOD & COD, from which all the spirit has been recovered, is collected in a large cooling pits. These are large cuboidal open storage tanks having a depth of about 12ft. The spent wash comes at a temperature of 60700C in the first pit and stored so that the higher density particles settle down It is then cooled via heat exchangers before pumping into the second pit. Plate Type Heat exchanger: The plate heat exchanger normally consists of corrugated plates assembled into a frame. The hot fluid flows in one direction in alternating chambers while the cold fluid flows in true counter-current flow in the other alternating chambers. A schematic diagram of the flow is shown in Figure. The fluids are directed into their proper chambers either by a suitable gasket or a weld depending on the type of exchanger chosen. Traditionally, plate and frame exchangers have been used almost exclusively for liquid to liquid heat transfer. The best example is in the dairy industry and distillery. Today, many variations of the plate technology have proven useful in applications where a phase change occurs as well. This includes condensing duties as well as vaporization duties. 61
Plate heat exchangers are best known for having overall heat transfer coefficients (U-values) in excess of 3–5 times the U-value in a shell and tube designed for the same service. Plate heat exchanger is an attractive option when more expensive materials of construction can be employed. The significantly higher U-value results in far less area for a given application. The higher U-values are obtained, by inducing turbulence between the plate surfaces. Owing to this, they are also known to minimize the fouling.
The cooled fluid, from the pit is pumped into storage tank. From here, the spent wash is subjected to primary treatment, after passing through clarifier. The clarifier is a settling tank used to remove dregs by sedimentation before the liquor is pumped into digester.
Primary Treatment Anaerobic digesters serve as an energy conversion process by converting volatile solids into digester gas. The digester gas resulting from the bioenergy conversion, sometimes referred to as biogas, is a renewable fuel. The energy content in digester gas comes from methane: its dominant constituent.
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Phase I Acid phase and methane phase digester: Initial phase, or the acid phase, continually receives an organic feed for short detention times of less than two days under conditions which efficiently liquefy and breakdown the feed, containing organic carbonaceous matter, to volatile fatty acids (VFA) of low molecular weight and other intermediates for conversion to methane. The most abundant VFA is acetic acid, followed by butyric and propionic acid. The volatile fatty acids remain solubilized in the liquid portion of the digester contents. A succeeding phase (methane second phase) is operated, in a separate digester, to treat the lower molecular weight acids and intermediates for detention times of about two to about seven days, in (methanobacterium, which methanogenic microorganisms methanococcus etc) convert the volatile fatty acids to product gas composed primarily of methane and carbon dioxide. Product gas is removed from the methane second phase and processed or scrubbed to separate the methane component that is drawn off as pipeline gas. A typical anaerobic digester product gas may contain, on a dry basis, 55% to 65% methane, 35% to 45% carbon dioxide, and less than 1% of other gases. Phase II The spent liquor from the phase I digesters is fed to a large buffer tank. Also there is a direct supply of spent wash from the cooling pit simultaneously.
AUTO BUFFERING: The pH of the spent wash (from the distillation house) is about 4.64.5, and the pH of the slurry from the phase I digesters, is about 7.5. This increase in pH results from bioconversion of acids in the digesters. The purpose of the buffer tank is to mix these two separate streams of slurries and maintain the pH in the range 5.5-6.0, suitable for feeding the subsequent Bio-Digesters. For example, if the pH reduces, more slurry is drawn from phase I digesters, and if pH increases, more spent wash is circulated from the storage tank. Auto buffering implies, that no external chemicals are added for maintainance of pH in BioDigester feed, or subsequent effluent treatment.
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The phase II consists of two Biodigestors, installed through Western Paque India Ltd, which are simultaneously feeded by the buffer tank. These digesters use acidogenic and methanogenic bacteria to produce CO2 and CH4 gas. This bioconversion of organic matter results in reduction of C.O.D to about 16000-17000mg/l. the following reactions occur in the anaerobic digester4H2 + CO2 CH4 + 2H2O 4HCOOH CH 4 + 3CO2 + 2H2O CH3COOH CH4 + CO2 2CH3OH 3CH4 + CO2 + 2H2O 4(CH3)3N + H2O 9CH4 + 3CO2 + 6H2O + 4NH3 The effluent from the primary reactor is sent to effluent storage lagoon. This effluent is further treated by secondary treatment so as to make it capable for using in irrigation purposes.
Secondary Effluent treatment plant The secondary effluent treatment plant treats the primary treatment plant discharge by anaerobic treatment on the basis of extended aerators form of activated sludge process. The discharge of the biomethanation plant comprises of not easily biodegradable organic matter.
64
Secondary treatment involves the following stepsMIXING TANK The effluent from the primary treatment plant is sent to the mixing tank where the effluent is mixed with water, so that the sludge settles down in the tank. After mixing the effluent is sent to Aeration Tank-I. AERATION TANK In an aeration tank the effluent is agitated in the presence of oxygen, since certain reactions take place in aerobic conditions. The effluent releases some of the gases and solid sludge. The released gases are NH3, NO2 etc, due to action of nitrifying bacteria. And also, due to agitation of the effluent, the Total Dissolved Solids(TDS) level falls and so does the level of BOD & COD. The discharge from the primary aerator is sent to primary Clarifier and to the aeration tank-II. PRIMARY CLARIFIER The Clarifier is a continuously operating, mechanically cleaned sedimentation device, which is designed to promote the separation of solid sludge from liquids. In Patiala Distilleries, the type of clarifier in operation was central feed fixed bridge circular clarifier. Feed enters from bottom of tank through the center column and goes into the clarifier. Feed flows down and then outward (radially) to the periphery of the tank where effluent is collected in a continuous peripheral launder. In circular sedimentation tanks the clarifier mechanism has sludge scrapers attached to a rotating arm scraping the sludge towards a central hopper, into a discharge sump.
65
Final Disposal Effluent collected in the lauder, having BOD and COD approx 100mg/l and 735mg/l (as per environment act norm), is sent to nearby farms for irrigation purposes. The thick and viscous sludge is then pumped into a series of sludge drying beds. Here the solids are dried in open air and then provided to farmers as fertilizers in the nearby areas.
8. CONCLUSION The summer training at Patiala Distillers and Manufactures Ltd. was completed successfully during the period June-July 2008. I am fortunate to have got such such an opportunity to gain knowledge on
66
the various industrial processes and operations. This exposure helped me familiarize with the actual industrial working culture and the practical aspects of the theoretical knowledge learnt in classroom and in the books. During my training period I gained knowledge on the industry scale fermentation process, the equipments and the methodologies employed in the extraction of spirit. I learned the distillation, purification process of alcohol and also the safety and the quality concerns. I got the opportunity to understand the on-site working of the steam boiler, and also the techniques and processes employed in treatment of distillery effluent in the ETP, as per the environmental norms and regulations. Though Patiala Dist. didn’t allow us to work and perform experiments in their laboratories regarding sugar content in raw material, alcohol estimation of final product, BOD and COD tests etc., but we were explained the methodologies of each experiment. Thus, my summer training in Patiala Dist. was a very fruitful experience , and would certainly help me during my study and in future.
9. REFERENCES 1. Patiala Distillery, Hand outs
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