FEASIBILITY STUDY OF RECYCLING USED LUBRICATING OIL
Akilimali, Fortune Christian
BSc. Petroleum Engineering The University of Dodoma July 2017
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CERTIFICATION
The undersigned certify that he has read and hereby recommend for acceptance for Submission of the final year project titled: “Feasibility study of recycling used lubricating oil”
…………………… MR.RAMADHAN BAKARI (Supervisor)
……………………… (Submission date)
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DECLARATION AND COPYRIGHT
I, Akilimali Fortune C. declare that this project report is my own original work and that it has not been presented and will not be presented to any other University for a similar or any other degree award.
………………………… (Signature)
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ACKNOWLEDGEMENT
I praise God the Almighty above all for blessing me with this opportunity and granting me the capability to proceed successfully. The success of this project is due to assistances and supervision I received from several people all of whom deserve my sincere respects. I express my deep appreciation to my supervisor, Mr. Ramadhani Bakari, for his mentorship throughout – from my proposal for the research to the completion of this research project. The excellent assistance I received from the Mr. Masatu (laboratory technicianCOES), Mr. Sangiwa (laboratory technician-CNMS), Mr. Robert Njama (laboratory technician-CNMS). My warmest thanks and appreciation also goes to my parents for their unconditional love and the overwhelming spiritual and material support I ever received from them in all aspects of my life. May the Almighty God splendidly bless you! Akilimali Fortune, July, 2017.
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DEDICATION
I would love to dedicate this project to my parents, Mr. &Mrs. Akilimali, I’m very much humbled yet proud to have such an amazing parents, I love you all very much indeed.
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ABSTRACT
As used lubrication oil is one of the hazardous wastes generated at different development sectors, it should not be utilized and/or disposed in ways which are unsafe to the environment hence calling for its proper management. This study primarily focuses on the recycling of used oil by applying acid-clay treatment process. Used engine oil properties gave expected undesired characteristics caused by oil deterioration. The characterization was indicative to the sources of contaminations from conditions during the oils application period. Recycling experiments utilized 5, 10, 15 and 20% acid and adsorbent (Bentonite clay) ratios with different combinations (0, 10, and 20%). The selected optimum operational parameters were 15% acid and 10% adsorbent. This optimum combination gave a 58% yield; density of 0.89 g/ml and the average kinematic viscosity at 100 °C of 16.230 mm²/s, approximately 2% of valuable light components were recuperated from the dewatering step of the process. Using this yield as a basis for material balance evaluation and by using current market prices, the primary cost analysis shows that a maximum amount of TSh 5123/= is expected to recover a litre of the sample from 1.59 litres of waste oil as summarized in Table 4-4. However, a barrel of base engine oil is imported for US $65 – $68, which is equals to TSh 878 – TSh 920 per litre while the current market price of the engine oil in Tanzania is TS 7000/= per litre in which the profit of Tsh 1877 will be obtained per
litre.
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LIST OF ABBREVIATIONS TPDC -
Tanzania petroleum Development Company
ppm
Parts per millions.
-
VOCs -
volatile organic compounds.
EPA
-
United States Environmental protection Agency.
bbl
-
billion barrels
Mcfd -
million cubic feet.
LP
-
value of loss products (Tsh)
P
-
Price (Tsh)
L
-
the amount of products in liters.
Tsh
-
Tanzania shillings
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Table of Contents CERTIFICATION................................................................................................................. i DECLARATION AND COPYRIGHT ................................................................................ ii ACKNOWLEDGEMENT .................................................................................................. iii DEDICATION .................................................................................................................... iv ABSTRACT ......................................................................................................................... v LIST OF TABLES ............................................................................................................... x LIST OF FIGURES............................................................................................................. xi CHAPTRE ONE .................................................................................................................. 1 1.0 INTRODUCTION .......................................................................................................... 1 1.1 Historical Background ....................................................................................................... 1 1.2 Problem Statement ............................................................................................................. 2 1.3 Project Objectives. ............................................................................................................. 3 1.3.1 Main objective................................................................................................................. 3 1.3.2 Specific objectives. ......................................................................................................... 3 1.4 Significance of the Study. .................................................................................................. 3 CHAPTER TWO ................................................................................................................. 4 2.0 LITERATURE REVIEW ............................................................................................... 4 2.1 Introduction. ....................................................................................................................... 4 2.2 Used Lube Oil .................................................................................................................... 4 2.3 Used Oil Composition........................................................................................................ 5 2.3.1 Water content in used lube oil......................................................................................... 5 2.3.2 Chemical contaminants. .................................................................................................. 6 2.4 Waste Oil Management Options. ....................................................................................... 6 2.5 Recycling Methods. ........................................................................................................... 7 2.5.1 The acid-clay process ...................................................................................................... 7 2.5.2 Conventional methods..................................................................................................... 7 2.5.3 Solvent extraction method .............................................................................................. 8
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2.5.4 Membrane technology..................................................................................................... 8 2.5.5 Vacuum distillation and hydrogenation .......................................................................... 9 2.5.6 Glacial acetic method ...................................................................................................... 9 2.6 Properties of Lube Oil. ..................................................................................................... 11 2.6.1 Pour point. ..................................................................................................................... 11 2.6.2 Viscosity........................................................................................................................ 11 2.6.3 Refractive index. ........................................................................................................... 12 2.6.4 Specific gravity ............................................................................................................. 13 2.6.5 Water and sediments ..................................................................................................... 13 2.6.6 Carbon Residue. ............................................................................................................ 14 2.6.7 Flash point (ASTM D-92, D-93)................................................................................... 14 CHAPTER THREE ............................................................................................................ 15 3.0 METHODOLOGY. ...................................................................................................... 15 3.1 Sampling .......................................................................................................................... 15 3.2 Dewatering Stage ............................................................................................................. 16 3.3 Desludging (Extraction) Stage Using Acetic Acid. ......................................................... 17 3.4 Clay Adsorption Process .................................................................................................. 18 3.4.1 Preparation of activated clay for bleaching................................................................... 18 3.4.2 Adsorption with activated bentonite ............................................................................. 19 CHAPTER FOUR .............................................................................................................. 20 4.0 RESULTS AND DISCUSIONS .................................................................................. 20 4.1 Chemical and Physical properties of Used Oil sample. ................................................... 25 4.2 Amount of Water and Light components in used oil sample .......................................... 20 4.3 Effects of Adsorbent Ratio............................................................................................... 20 4.4 Colour Visualization ........................................................................................................ 20 4.5 Physical Characteristics of produced base oil .................................................................. 22 4.5.1 Density .......................................................................................................................... 23 4.5.2 Kinematic viscosity: ...................................................................................................... 24 4.6 Economic Analysis .......................................................................................................... 25
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CHAPTER FIVE ................................................................................................................ 27 5.0 CONCLUSION AND RECOMMENDATIONS ......................................................... 27 5.1 Conclusion ....................................................................................................................... 27 5.2 Recommendation. ............................................................................................................ 29 REFERENCES ................................................................................................................... 30 APPENDIX ........................................................................................................................ 32
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LIST OF TABLES Table 4-1: Description of the engine oil samples in Figure 4.1 ......................................... 21 Table 4-2: Pictures of the engine oil samples as described in Table 4.1 ........................... 22 Table 4-3: Flow time, Kinetic viscosity and Dynamic Viscosity ...................................... 24 Table 4-4: Balance based on one liter product yield .......................................................... 26
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LIST OF FIGURES Figure 3-1: Heating the sample with the help of a magnetic stirrer ................................... 17 Figure 4-1 : Density of different types of oil treated with different acid ratio. ................. 24
CHAPTRE ONE 1.0 INTRODUCTION 1.1 Historical Background Lubricant oils are used for reducing friction of the moving parts like machinery by interposition of a thin film between the surfaces, as well as remove heat, keeps equipment clean, and prevents rust. When the oil is in use, impurities such as water, dirt, metal scrapings and other mixed in with the oil. Lubricating oils additives also degrades when use, adding contamination therefore, lubricating oil must be replaced. Once replaced; the oil is termed as used oil and require proper management in order to avoid environmental pollution associated with the disposal of used oil (Fox, 2007). Consequently, there are various methods which have been developed, both to reduce the environmental hazard associated with either disposal or burning of the oil, and to conserve valuable used oil resources which can be recycled into base lube oil. Solvent extraction, an innovative adaptation of existing crude oil refining technology, is being studied for its potential to upgrade used/waste lubricant oils. The aim of the study is to recycle used lubricant oil using acetic acid extraction technology to produce base lube oil.
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1.2 Problem Statement Lubricating (lube) oils have predefined useful time at which its quality degrade and therefore oil fail to provide sufficient lubricity and therefore replaced as used oil. Currently, in Tanzania waste lube oil are used in oil furnaces, wood treatment plants, loosening rusted bolts and in preventing rusting in different metal. The burning of these used oil have significance effects to the environment as these pollutants are realised in the atmosphere after combustion. Waste engine oils cause damage to the environment when dumped or into water streams, therefore, require responsible management (Shakirullah & Ahmed, 2006). Recycling of such contaminated oil will be beneficial in reducing the cost of importing base lube oil costs as well as environmental pollution (Martins, 1997). Although there are many technical ways in which this used lubricant oil can be recycled but currently in Tanzania, the waste oil is not collected for recycling purpose. In Ghana the amount of lubricating oils that is collected annually for recycling is approximately 500 to 600 thousand tons which cost millions of dollars to manufacture (Shakirullah & Ahmed, 2006). As such a huge amount of used oil; if discharged into the land, water or even burnt as a low grade fuel, this may cause serious pollution problems (Kenedy, 1976). A recommended solution for this issue is the recycling of the waste oil so that the oil can be used again as a base stock. Therefore the aim of this project is to recycle waste oil and obtain the base lube oil at the low cost as well as to reduce is environmental impacts caused by disposing (burning) the used/waste oils by using acetic acid extraction.
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1.3 Project Objectives. 1.3.1 Main objective. Feasibility study of recycling used lubricating oil.
1.3.2 Specific objectives. 1. To estimate the optimum amount of lube oil that can be recovered from waste lubricating oil and volume ratio of acetic acid to be used. 2. To assess the physical properties of the obtained new base lube oil whether it meets the ASTMD112 test quality. 3. To perform economic analysis of recycling used lubricant oil.
1.4 Significance of the Study. After the successful of this project, the study will help to produce new base lube oil from used/ waste oil that will be used for blending. This study aims to produce the base stock oil at low price by making use of the available waste/used lube oil in low price and finally reduces the cost of buying new base lube oil. Also reduce environmental impacts which associates with improper ways of disposing the used/waste oils (like burning in furnaces).
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CHAPTER TWO 2.0 LITERATURE REVIEW 2.1 Introduction. Lubricant oils are derived from petroleum-based and non-petroleum-synthesized chemical compounds. (Frankl, 2005). They are made up from heavier and thicker petroleum hydrocarbon base stock which consists of hydrocarbons with carbon range between 18 and 34 blended with additives to improve certain properties (Beuther, 1989). One of the important properties of lubricant oil that defines its ability to maintain a lubricating film between the moving parts is viscosity (Frankl, 2005). The viscosity of a liquid is the measure of its resistance to flow; it must be high enough to provide a thick lubricating film, but low enough to allow the oil to flow easly around the engine parts under all conditions (Whisman & Reynolds, 1978). The viscosity of oil changes with temperature, a measure of how much the viscosity of the oil changes as temperature changes is called viscosity index. A higher viscosity index indicates the viscosity changes less with temperature than a lower viscosity index (Georgi, 1990). Other important properties of the lubricant oil are specific density, pour point, refractive index, total acid number Cardoon residual and flash point. 2.2 Used Lube Oil Used/waste lube oil is defined as lubricant oil which remains after its for certain period of useful life (ASTM, 2004). When the lubricating oil is in use it degrades due to contamination with metals, water, varnish, ash, gums, carbon residue and other
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contaminating materials (Whisman, 2002). As it is contaminated with time, the lubricant oil loses its lubricating ability and therefore as a result after a certain predefined useful time become replaced with fresh one and the replaced oil is called used/waste lube oil (Georgi, 1990). 2.3 Used Oil Composition A lubricating oil becomes unfit for further use for two main reasons; accumulation of contaminants in the oil and chemical changes in the oil (Shakirullah & Ahmed, 2006). The main contaminants are combustion products contains water which leads to sludge formation and rust (Rincon & Canizares, 2005). Others are soot and carbon that make the oil go black, Lead (Tetraethyl lead) from bearing wear and is likely to be in the 2 - 12 ppm range (Georgi, 1990) and fuel comes from unburnt gasoline or diesel especially during start-up (Kenedy, 1976). Lubricant oil is also contaminated with abrasives road dust that passes into the engine through the air-cleaner as small particles (Frankl, 2005). 2.3.1 Water content in used lube oil. The amount of water found in used lubricating oil depends on the type of automobile in which it is being used. In normal operating conditions traces of water arising from sources such as leaking oil coolers, engine cooling system leaks and from atmospheric condensation (Rincon & Canizares, 2005). The presence of excessive water will affect the viscosity of the oil and give rise to emulsion formation and can also lead to gear tooth or bearing problems (Henry, 2015).
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In dewatering process the oil can be heated to 180°C and under atmospheric pressure for a period of 1 hour to eliminate the free water and emulsified water. Since water boiling point is 100°C at STP, temperatures above this point are usually practical, but at higher temperatures above 200°C, light hydrocarbon fractions are lost and the water is contaminated requiring thorough treatment. (Whisman, 2002) 2.3.2 Chemical contaminants. The common chemical contaminants mainly are oxidation products where by at an elevated temperatures some of the molecules of the oil tend to oxidize forming complex and corrosive organic acids (Georgi, 1990); other chemical contaminants are depleted additive remnants (Kiss, 2011). 2.4 Waste Oil Management Options. Although dumping and oil burning are practiced in most countries but they are not listed here as oil management options because they are not recommended proper ways to dispose oil (Fox, 2007). The recommended disposal options for waste oils may be one of the following; regeneration of new base oil, thermal cracking and incineration/use as fuel. A variety of technologies has been invented for regeneration of used lube oil to produce various yields of base oil stream, fuel by-products stream and the stream heavier of residue (Whisman & Reynolds, 1978). Regeneration process creates fuel by-product streams (the lighter components) that may be used as fuel and the obtained base oil is used as lubricant oil after been blended with additives. The stream of heavier residual containing carbonaceous species, are used as a blending component in the bitumen
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processing industry, for incorporation into construction products such as road surfaces (Fox, 2007). 2.5 Recycling Methods. Several methods have been developed successful to recycle used engine oil where by every method was developed to improve the previous one. 2.5.1 The acid-clay process Historically, the most successful technology for treating used oils was the acid-clay process developed in Washington State (Hamawand, 2013). This process was capable of producing good quality lubrication stocks, but also produced large volumes of petroleumcontaminated acid clay sludge (Fox, 2007). Based on Resource Conservation and Recovery Act (RCRA) and later legislation, classified acid clay sludge as a hazardous waste and required proper management and disposal method (Martins, 1997). Consequently, the acid-clay process technology classified as uneconomic technology because of the high cost of managing residues and is no longer used in Washington State (Hamawand, 2013). 2.5.2 Conventional methods In later time the conventional methods of recycling of waste engine oil was developed. These methods require a high cost technology such as the use of toxic materials (sulfuric acid) and simultaneously produces by-products which have highly sulfur level therefore did not meet environmental sulfur limits and required additional costs for removal of sulfur (Georgi, 1990).
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2.5.3 Solvent extraction method Later on, solvent extraction method replaced acid treatment method. Solvent extraction method produced better base oil by improving the stability to undergo oxidation and improves viscosity -temperature characteristics of base oils. The solvent dissolves undesired aromatic components, leaving the desirable saturated hydrocarbon components especially alkanes as a distinguished phase (Rincon & Canizares, 2005). Although the oil produced from this process was comparable to that produced by the acid-clay method, extraction process causes huge losses of solvent, and highly skilled operating maintenance. In addition, extraction is conducted at higher pressures (greater than 10 atm.) therefore requires high pressure sealing systems which makes solvent extraction plants expensive to construct (Hopmans, 1974). Later propane extraction was invented. Propane is capable of dissolving waxy/paraffinic material and intermediately dissolved oxygenated material (www.astm.org., n.d.). Materials like asphaltenes which contain heavy aromatic compounds are not soluble in the liquid propane. These properties tend to make propane ideal for recycling the waste/used engine oil, but there are many other issues that have to be considered such as propane is hazardous and very flammable therefore it was regarded as a hazardous process (Hamawand, 2013). 2.5.4 Membrane technology Another method used for regeneration lubricating oils was membrane technology. Three types of polymer fiber membranes [polyethersulphone (PES), polyvinylidene fluoride PVDF), and polyacrylonitrile (PAN)] were used for recycling the used/waste engine oils.
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This process is carried out at 0.1 MPa pressure and 40°C (Martins, 1997) and is a continuous operation which removes metal particles or dusts from used/waste engine oil and also improves the recovered oils liquidity as well as flash point. Despite the above mentioned advantages, the expensive membranes may get damaged and fouled by large particles (Henry, 2015). 2.5.5 Vacuum distillation and hydrogenation Vacuum distillation and hydrogenation was another method used for recycling used engine oil (Whisman & Reynolds, 1978). The Kinetics Technology International (KTI) proposed the combination of vacuum distillation and hydrofinishing (Beuther, 1989). The process begins with atmospheric distillation to remove light hydrocarbons and water then, followed by vacuum distillation at a temperature of 250°C and finally hydrogenation of the distillation products to eliminate the nitrogen, sulphur and oxygenated compounds (Beuther, 1989). Also this stage has been used for many years to improve the odor and color of the oil and produces the products of quality standard (Gp.I) with a yield of approximately 82% of the feed and minimized polluting by-products but it needs high investment cost (Rincon & Canizares, 2005). 2.5.6 Glacial acetic method Later Glacial acetic method was invented. The research shows that acetic acid is very useful for recycling used lubricant oils because it is very powerful in dissolving and attracting polar contaminants, metal particles contaminants from used oil (Kiss, 2011). The method has less cost process in compared to the conventional methods because of the
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low cost and easily availability of the acetic acid. The recycled oil product obtained by this method shown to have potential to be reuse as an oil blend for engine lubricants (Rincon & Canizares, 2005). The KIT research shows that, acetic acid extraction process for used/waste engine oil yields about 80 to 90 % (depending on the method used) of base lubricating. This is to say if the recycling of the used lubricant oil is careful handled with proper technology, the significant amount of base oil will be recovered with relatively cheaper process to producing high yield and good quality lubricating oil base stock comparable to virgin lube oil base stock (Henry, 2015). 2.5.6.1 Acid extraction ratio.
Different researches showed that for dry used lubricant oil, the maximum purification using acetic acid have been proven to fall between 0.02-0.2 (v/v%) when added to it depends on the amount of contaminants present on it (Kiss & Bartels, 2007). Therefore, the ability of acetic acid to separate the base oil from the contaminated used oil, are being studied in series of experiments using oil–acid volume ratios between 0.02(v/v %) to 0.2(v/v ) The two layers are expected to form which are a clear reddish lubricant oil layer and sludge at the bottom of the measuring cylinder. Both the lube oil and the sludge produced in each portion could be weighed in order to obtain the optimal acid-oil ratio for a particular oil sample.
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2.6 Properties of Lube Oil. 2.6.1 Pour point. Pour point of an engine oil is simply defined as the lowest temperature at which the oil will remain in a flowing state (Donald, 1897). Engine base oils may contain waxes and paraffins which solidify in cold temperatures; it have been noted that oils with high wax and paraffin content will always have a higher pour point (Singh & Gulati, 2008). The pour point of lube oil is highly affected by an oil’s viscosity; engine oils with high value of viscosity are normally characterized with high pour points. When starting the engine in cold weather the pour point of an oil become an important variable. The oil must have the ability to flow well into the oil pump for a particular range of conditions and therefore be pumped to the various part of the engine even at low temperatures (Martins, 1997). 2.6.2 Viscosity. Viscosity of a fluid is the measure of its resistance to gradual deform when shear stress is applied. There are two related measures of fluid viscosity; Dynamic (or absolute) viscosity and Kinematic viscosity. 2.6.2.1 Dynamic (absolute) viscosity.
Absolute viscosity is defined as a measure of internal resistance of a fluid. Absolute/dynamic viscosity is the tangential force per unit area required to move one horizontal plane with respect to another plane per unit velocity when maintaining a unit distance apart in the fluid (Diaz & Bernardo, 1996).
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2.6.2.2 Kinematic viscosity.
Kinematic viscosity will be obtained by dividing the absolute viscosity of a particular fluid with the fluid mass density (Diaz & Bernardo, 1996).
Viscosity is a state function of temperature, pressure and density in that, viscosity varies inversely proportional to temperature. Viscosity testing always gives the contamination information as is used to indicate the presence of contamination in used engine oil. The oxidized products as well as polymerized products which are dissolved and suspended will result into increase of the oil viscosity, while the decreases in the viscosity of engine oils will indicate the presence of fuel contamination (Diaz & Bernardo, 1996). 2.6.2.3 Viscosity index
Viscosity Index is strictly an empirical number which indicates the effect of variation in temperature on viscosity. A high viscosity index will always indicates a small variation in viscosity of an oil with temperature, which means better protection of an engine that operates under vast temperature variations. A high value of viscosity index indicates the absence of aromatic and volatile compounds, also means good stability in its thermal properties and low temperature flow behaviours (Singh & Gulati, 2008). 2.6.3 Refractive index. Refractive index (RI) is the ratio of the velocity of light in vacuum to the velocity of light in substances at a specific temperature. The refractive index is used to provide the important information about the composition of lubricant oils. Low values of refractive index indicate the presence of more paraffin material while high values indicate the
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presence of more aromatic compounds. It can also be used to estimate other physical prosperities such as molecular mass (Riazi & Roomi, 2001). 2.6.4 Specific gravity Specific gravity is the ratio of the mass of a fixed volume of substance to the mass of the same volume of water which depends on the temperatures at which the mass of the sample and the water are measured. Specific gravity is highly influenced by the chemical composition of the lubricant oil. An increase in the amount of aromatic compounds in the lubricant oil will results in an increase in its specific gravity, while an increase in the saturated compounds will results in a decrease in the specific gravity (Shakirullah & Ahmed, 2006). 2.6.5 Water and sediments Water is generally classified as a chemical contaminant when suspended in lubricant oils. Based on different researches, it has been noted that water contamination of engine oil affects the oil quality, condition and wear of engines in service (Hamawand, 2013). The water content in engine oil is dependent on oil composition, physicochemical properties, production technology and conditions of use and storage. Water created in engine oil is a result of: condensation (humid air entering oil compartments), absorbing moisture directly from the air (oil is hygroscopic), combustion
(fuel
combustion forms water which may enter the lubricant oil through worn rings), heat exchanger
(corroded or leaky heat exchangers), oxidation (chemical reaction) and
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neutralization (when alkalinity improvers neutralize acids formed during combustion), and free water entry (during oil changes) (Donald, 1897). 2.6.6 Carbon Residue. Carbon residue is defined as the amount of carbonaceous residue remaining after the thermal decomposition of an engine oil in a insufficient amount of air is also called coke or carbon forming tendency. The carbon residue test can be used to evaluate the characteristic of engine oils to depositing carbonaceous material in internal combustion engines. It is important to note that the carbon residue value of engine/motor lubricating oil is regarded as indicative of the amount of carbonaceous deposits that the engine oil would form in the combustion chamber of an engine. For example, an ash-forming detergent additive may increase the carbon residue value of engine oil and will generally reduce its tendency to form deposits (Whisman, 2002). 2.6.7 Flash point (ASTM D-92, D-93). Flash point is the temperature above which a combustible liquid will give off sufficient vapour to form a flammable mixture with air; this mixture should burn momentarily when a small flame is applied under a certain specific conditions. Because it indicates the temperature at which a flammable vapour is produced, flash point is generally the most useful single index of fire hazard potential.
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CHAPTER THREE 3.0 METHODOLOGY. This study aimed to remove the contaminants from the used oil so that it can be reused. The study was accomplished through series of steps such as; sampling, dewatering, desluging/extraction by using glacial acetic acid and finally the economic analysis of recovered products were performed. 3.1 Sampling The used lube oil samples (SAE-40) were collected from TANESCO - Ubungo plant 1 (UGP-1). The samples were taken from the plant engine in 2016 for analysis of its performance in engine as a normal analysis maintenance procedures. At the plant the engine oil samples are taken after every three months in which the physical and chemical properties of the samples are measured and recorded in order to evaluate the oil contamination. The physical and chemical properties of the sample were measured at SGS laboratory located in Dar es Salaam.
After determination of physical and chemical
properties of these sample, the sample were labelled and stored in a sample store. The documents contains physical and chemical properties of these sample were kept in a special file for records. The selection of the sample for this study were just based on the availability of samples and their recorded properties. For the sake of these study, two litres of the used oil were taken from the sample store at UGP-1 and sent to the laboratory for further step. The official document contained data of the physical and chemical properties
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of the sample were taken from the plant. These properties have been summarized in Table 4.1. 3.2 Laboratory Procedures All other procedures involved in this study were conducted in laboratory at the University of Dodoma 3.2.1 Materials and chemicals used The essential laboratory materials and equipment used in this study were Beaker, Conical flask, Bunsen burner, Thermometer, Viscometer, Litmus paper, Hot plate and Magnetic stirrer, Test tube, Measuring cylinder, Digital mass balance Measuring cylinder, Water Bath, Filtering Paper, bentonite clay. The essential reagents used were Glacial Acetic acid, and Sulphuric acid. 3.2.2 Dewatering stage The samples were heated to 180°C as proposed by Whisman under atmospheric pressure for a period of 1 hour to eliminate the free water and emulsified water (explained in section 2.3.1). In this case 500ml portions of a sample were heated in an open beaker with the help of a magnetic stirrer as shown in Figure 3.1.
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Figure 3-1: Heating the sample with the help of a magnetic stirrer
3.2.3 Desludging (extraction) stage using acetic acid. The acid-oil ratio selected in this stage was between 5%v/v and 20%v/v as proposed by Kiss & Bartels, 2007 (explained in section 2.5.6). The process began by mixing 100ml of the oil sample with 5% by volume acetic acid in a flat-bottomed flask. The mixture were continuously stirred using a magnetic stirrer for 2 hours at around 60oC in order to facilitate uniform mixing (Hamawand, 2013). The mixture was allowed to settle for 6 hours (as proporsed by Rincon & Canizares, 2005) in a separating funnel, a heavy layer contain sludge appeared to settle at the bottom of the flask and oil layer appeared on top of it. An acid layer (containing sludge) were gradually discharged at the bottom of the separating funnel. The oil layer were also removed from separating funnel, measured its volume, labeled based on acid-oil ratio used and finally stored for father procedures. The
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process was repeated for the acid-oil ratio of 10%, 15% and 20% by volume. The treated oil in this stage was black in color. 3.2.4 Clay adsorption process The product obtained in section 3.2.3 were treated with an activated bentonite clay to improve its color (Hayalu, 2014). The color improvement were conducted based on the fact that the black color of treated oil may lead into confusion with the used one, therefore this procedures were carried out purposely to distinguish the treated oil from used one. This stage were divided into two steps; first was preparation of activated clay and the second step involved removing the oil colour using prepared activated clay. 3.2.4.1 Preparation of activated clay for bleaching.
In this stage, 200 g of betonite powder were mixed with 400 ml of 50% sulphuric acid to make the slurry. The slurry was then heated for about1 hour at around 80oC as proposed by (Udonne, 2011). This procedure was carried down to remove impurities from bentonite as well as to ionize the bentonite powder (Kiss, 2011). The mixture was left for 24 hours in order to create enough internal space of the bentonite clay for better adsorption process (Udonne, 2011) The clay was washed carefully with distilled water to remove precipitates and until it is free of SO42- ions (until pH is 6–7). The clay was filtered, baked for about 6 hours at 200oC to remove water and stored in dry place so that it can be used later in the adsorption experiments. The obtained dry and clean bentonite clay is called activated bentonite because it is active chemically and electrostatically.
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3.2.4.2 Adsorption with activated bentonite The activated bentonite prepared in section 3.2.4.1 were used at this adsorption step. Activated clay has been use in this step to improve color and oxidation stability of the acid treated oil (Kiss, 2011). Because the adsorption process using activated clay is favored by temperature range 90-120oC (Udonne, 2011), in this experiment the adsorption process were performed at 110oC. The adsorption were studied by using a clay-oil ratio range from 0%v/v to 20%v/v as suggested by (Talal, 2013); that the clay-oil ratio larger than 20%v/v will results large amount of filter cake. As the results of filter cake the filtration process will be expensive; large volume of heavy slurry will remain unfiltered therefore the process will not be economical. By using constant adsorption time 2 hours and constant temperature of 110oC, the oil products obtain from desludging process (in section 3.2.3) were treated with clay-oil volume ratios 10%. The process was carried out while stirring the mixture. For each adsorption process the oil were filtered and the obtained oil were stored for final observations. The process was repeated by using 20% v/v of clay-oil.
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CHAPTER FOUR 4.0 RESULTS AND DISCUSIONS 4.1 Amount of Water and Light components in used oil sample The amount of water and light hydrocarbons present in used oil was calculated by considering the amount (volume) of sample used at the beginning of the dewatering process and the amount of oil obtained at the end of the process (Table A-1; appendix). Since the sample were heated in an open container (see Figure 3-1) it was not possible to collect the distillates (water and some low boiling point components) but the amount of distillate were determined as the volume lost during the heating process. It was observed that, for 500ml of the sample the amount of oil remained after the dewatering process was approximately 490ml, meaning that 10ml equals to 2% of light hydrocarbons and water were evaporated for every 500ml heated. 4.2 Effects of Adsorbent Ratio It is clearly observed that as the quantity of adsorbent used increased with constant acid concentration, the total amount of recovered oil has considerably decreased. But it does not have substantial effects on density and viscosity. Other parameters such as ash contents, Flash Point and Metal Content were not measured in this experiment. 4.3 Colour Visualization The base oil did not show any change in colour when mixed with acetic acid due to its low reactivity of acetic acid with the base oil (see Figure 4.1(b)). This is because acetic acid do
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not react with oil like sulphuric acid, only reacts with contaminants in the used (ChadraSekhar, 2015). However, the base oil resulting from acetic acid treatment shows brighter and has a clear yellowish colour when treated with highly active clay (Hayalu, 2014). In this experiment the oil obtained from clay adsorption did not show the clear yellowish colour but rather brownish (see Figure 4.1(d)). This is because the activated clay were just prepared by using normal laboratory procedures, which obviously not highly active clay. Table 4-1: Description of the engine oil samples in Figure 4.1
Figure Description (a)
Used engine oil
(b)
Used oil treated with 20%v/v glacial acetic acid after mixing for 2 hour.
(c)
Base oil produced by using 20%v/v glacial acetic acid and clay treatment (10%v/v) at 110oC 2 hrs.
(d)
Base oil produced by using 20%v/v glacial acetic acid and clay treatment (20%v/v) at 110oC 2 hrs.
22
(a)
(b)
(c)
(d)
Table 4-2: Pictures of the engine oil samples as described in Table 4.1 The clay treatment with 20 % (v/v) (Figure 4.1 (d)) shows better results in color improvement than 10% (v/v) (Figure 4.1 (c)) clay treatment. The adsorption time has significant effect on adsorption results, in this experiments the adsorption time was kept constant for all samples. It has been observed that the more the concentration of the adsorbent, the brighter the color of the oil. 4.4 Physical Characteristics of produced base oil In this part only some few physical properties of sample were selected for measurement. The selected properties were based on availability of the facilities required to easily conduct the tests. The selected physical properties include: Viscosity and Density. The obtained results were compared with that of the used oil sample and observing similarities with the base oil standards.
23
4.4.1 Density It was observed that the density of the sample is higher than the density of treated oils. The average densities of recovered oils were between 0.88–0.91 g/ml depend on the acid– oil ratio used. Relatively higher densities are observed with lower acid ratio (5%) i.e. 0.910.93 g/ml for all the different adsorbent percentages (Table A-4 Appendix). However the density decreases significantly when treated with adsorbent, for instance when 10% of adsorbent-oil ration used the average density of 0.9g/ml obtained. As the acid ratio increased to 20%, densities of 0.9, 0.89 and 0.88 are obtained for adsorbent-oil ratios of 5%, 10%, and 15% respectively (Figure 4-4). There were no changes in density seen when the acid ration increased from 15% to 20% as seen in Figure 4-4. This implies that the acid ratio of 15% were enough for the extraction process in which any addition acid will remain as an excess. Therefore this have been considered as the optimal acid-oil ratio in this experiment such that any further increment on the acid concentration above 15% will gives similar results as explained in Section 2.5.6.This clearly shows that an acid addition over 15% is insignificant.
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Figure 4-1 : Density of different types of oil treated with different acid ratio. 4.4.2 Kinematic viscosity: Four attempts were used to calculate the average kinematic viscosity. The flow time obtained for each experiment were tabulated in a Table 4.3 in which the kinematic viscosity were calculated as a product of the tube constant and flow time. The average kinematic viscometer were 16.230 mm²/s.
Table 4-3: Flow time, Kinetic viscosity and Dynamic Viscosity Attempt
Tube constant
Flow Time
Kin. Viscosity
No. 1 2 3 4
[mm²/s]/s 0.4637 0.4637 0.4637 0.4637
S 35 36 35 34
[mm²/s] 16.2295 16.6932 16.2295 15.7658
Average kinematic viscosity = 16.230 mm²/s.
Density at 100oC [g/cm³] 0.8291 0.8291 0.8291 0.8291
Dyn. Viscosity [mPa.s] 13.456 13.840 13.456 13.071
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4.5 Comparison of Chemical and Physical properties of Used Oil sample. The chemical and physical properties of the sample (used oil) were compared with that of the same new oil as shown in Table A-5 (appendix) It was observed that the used lube oil contains water, soot, lead, and Sodium which do not contained in new oil sample. 4.6 Economic Analysis The primary cost analysis is completed to estimate and compare costs suffered by the recycling process of used oil and the price of imported generator engine oil. This assessment of costs is necessary in giving information concerning the economic feasibility of the study. Costs accompanying with the recycling process in the study comprise chemical costs, electrical power costs and labour costs where most of them are operating costs. Costs of various equipment which will be vital for the construction and assembly of the recycling plant can also be considered for a complete plant design, which is not the range of this research. From Table A-2 Material balance results of the selected optimum experimental run (in Appendix); it is found that 58% recycling capacity is achieved from the selected optimum operational parameters which were 10% acid and 15% adsorbent. Using this yield as a basis for material balance evaluation and by using current market prices, the primary cost estimation of the process shows that a maximum amount of TSh 5123/= is expected to recover a litre of usable oil from 1.59 litre of waste oil as summarized in Table 4-3. A barrel of base engine oil is imported for US $65 – 68, which is TSh 878 – TSh 920 per
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litre. The current price for the blended engine oil is TS 7000/= per litre in which the profit of Tsh 1877 will be obtained per litre. Table 4-4: Balance based on one liter product yield Material
Unit
Amount
Used Oil
litre
1.59
1272
Acetic Acid
litre
0.159
3190
Grams
126.9
24
Additive (8%) (Caltex lubricants,2013)
litre
0.08
277
Energy
KW
1.0221
360
Bentonite Clay
Total price per litre
Cost (TSh.)
5123
From market sellers; the average prices for bentonite clay (bulk), were $90 per ton equals to TSh 189 per kg, the average prices for acetic acid were $10.5 per litre equals to TSh 22000 per litre and Engine Oil Price US $65-68 / Barrel
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CHAPTER FIVE 5.0 CONCLUSION AND RECOMMENDATIONS 5.1 Conclusion This research has shown that used engine oil can be recycled by using glacial acetic acid and clay treatments. The study proved that the acid treatment is a process that can effectively remove contaminants from used lubricating oil. The recovered oil has a comparable quality with the fresh oil indicating the possibility of reusing it. Used engine oil properties were determined with standard chemical and physical tests. Operational parameters were established in reference with the common acid-clay process and its modification. Acid and clay percentages ranges from 0% to 20% selected to test the effects of these variable factors Effects of acid and adsorbent ratios were studied on the recovery of usable lubricating oil from spent engine oil. The results showed that the efficiency of the recycling operation depends on these reagent ratios. It was noted that the recovery yield increases with decreased percentage in these ratios. A maximum recovery of 58% was obtained when both acid and clay to oil. However, while many variables have been studied in this research, there are many others that need investigation such as temperature, pressure, settling time, mixing, centrifugation speed and type of adsorbent Regarding cost effectiveness of the process, suggests that the process is economical feasible although the difference in the imported oil price and the cost incurred for
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reclaiming used oil increased the appeal of the recycling process to be implemented and gave an insight of its potential and opportunities for scale up.
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5.2 Recommendation. Further research is required in order to take this process to the commercial stage. However, while few variables have been studied in this research, there are many others that need thorough investigation such as pressure, temperature, settling time, mixing speed & time and type & size of adsorbent which have significant effects on the recycled oil qualities. In addition, the following aspects are important concerning the general characteristics of the treatment and recycling of used oils sector: In this experiment, the components (light hydrocarbons and water) were not collected since the oil were heated in an open beaker, in this case the bad odour smell were emitted during distillation. Exclusive investigation on used oil is recommended to identify components that are responsible for bad odour emission during distillation step and gives an indication to come up with effective solutions. Also a detailed cost benefit analysis evaluation should be made that will likens the potential benefits of used oil recycling with the expected costs of construction and erection of the scaled up plant Lastly, Further character testing may also be executed to evaluate oxidation stability, thermal stability and foaming character of the recycled oil. If possible practical application of the recovered oil in a real engine system should be experimented
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REFERENCES ASTM, 2004. Standard Test Method for Pour Points; ASTM Standard D97; ASTM International. West Conshohocken: PA, USA. Beuther, H., 1989. Hydrogenation and Distillation of Lubricating. journal of recyling of used lube oil, pp. 622,312. Brinkman, W., 2010. Used oil: resource or pollutant?. Technology Review, Volume II, pp. 46-52.. Caltex lubricants, 2013. Delo Gold Ultra , South Africa: Caltex lubricants. ChadraSekhar, B. P., 2015. Recycling and Analysis of Spent Engine Oil. International Journal of Scientific & Engineering Research, Volume 6(Issue 11), pp. 711-717. Diaz, R. & Bernardo, M., 1996. Prediction of the viscosity of lubricating oil blends at any temperature.. Fuel, pp. 75, 574–578. Donald, H., 1897. Physical properties of lubricants.. s.l.:s.n. Fox, M., 2007. Sustainability and environmental aspects of lubricants. In Handbook of Lubrication and Tribology,. New York, NY, USA: Elsevia Totten, E., Eds.. Frankl, P. F. P. B. M., 2005. Europe Life Cycle Considerations on recycling used oil. s.l.:s.n. Georgi, C., 1990. Motor Oils and Engine Lubrication.. New York, USA.: Reinhold Publishing Corporation. Hamawand, I., 2013. Recycling of Waste Engine Oils Using a New Washing Agent. 19 February, pp. 1023-1049. Hayalu, A., 2014. Recycling of Used Lubricating Oil Using Acid-Clay Treatment Process, Addis Ababa: s.n. Henry, m., 2015. Re-refining and recycling of used lubricating oil and natural resource conservation in ghana;. ARPN Journal of Engineering and Applied Sciences, VOL. 10,(NO. 2,), p. 797. Hopmans, J., 1974. The Problem of processing spent oil in the member states of EEC; Report for the European Economic Community (EEC). Dordrecht, The Netherlands: National Institute for Wastewater Treatment. Kenedy, M., 1976. A Technical, Economic and Environmental assessment of WasteOil Recovery and Disposal.. Waste oil Recycling Study., p. 455.
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Kiss, R., 2011. Improved atomic absorption techniques for measuring of iron particles in lubricating oil. At. Absorpt. Newsl.. s.l.:s.n. Martins, J., 1997. The extraction fof used lubricating oil using ternary organic solvents.. pp. 36, 3854–3858.. Riazi, M., 1987. Predicting flash and pour points. In: s.l.:s.n., pp. 66,81–83. Riazi, M. & Roomi, Y., 2001. Use of the refractive index in the estimation of thermophysical properties of hydrocarbons and petroleum mixtures. Ind. Eng. Chem. Res., pp. 40,1975–1984.. Rincon, J. & Canizares, P., 2005. Waste oil recycling using mixtures of polar solvents. Ind.. Eng. Chem. Res., pp. 44, 7854–7859.. Shakirullah, M. & Ahmed, I., 2006. Environmentally characterization and friendly recovery of oil from used engine lubricants.. J. Chin. Chem. Soc., pp. 53, 335–342.. Singh, H. & Gulati, I., 2008. Influence of base oil refining on the performance of viscosity index improvers.. Wear, pp. 118, 33–56. Talal, Y., 2013. Recycling of Waste Engine Oils Using a New Washing Agent. Energies, pp. 1023-1049. Udonne, J. D., 2011. A comparative study of recycling of used lubrication Oils using distillation, acid and activated charcoal with clay methods. Journal of Petroleum and Gas Engineering, Volume Vol. 2 (2), pp. pp. 12-19. Whisman, 2002. Waste Lilbricating oil research: an investigation of several re-refining methods,. I.J.S. Bureau of Mines: RI 7884,. Whisman, M. & Reynolds, J., 1978. Re-refining makes quality oils.. Hydrocarb. Process. , pp. 57, 141–145.. www.astm.org., n.d. s.l.: s.n.
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APPENDIX Table A- 1 Amount of used oil before and after dewatering process
Category
Value
Amount of used oil before evaporation
500 ml
Amount of dry oil at the end of evaporation
490 ml
Amount water and hydrocarbon lost
10 ml
Calculation of percentage loss. . . = 2.0 % Material balance of the selected optimum experimental run The material balance of the process is considered based on the selected optimum operational conditions of the variable factors. These are: Acid percentage =10 % Adsorbent (clay) percentage = 15 % Table A- 2: Material balance results of the selected optimum experimental run
Proces
Input
Output
s
Reco very
Distilla 5 98% 4 tion
00 ml
90 ml
H eat Acid treatm
D
istillate loss – 10 ml
O 95% O il 100 ml
il – 95 ml
33
ent
A cid 10 ml
S
ludge – 15ml
Adsorp O 58% O tion Proces s
il – 90 ml
il recovered – 58 ml
B entonite 12.96g*
ludge – 44g
S
34
Material balance based on one liter product yield. 1. Used oil required to produce 1 liter for the process can be calculated as: U = (1-x)/0.58 U = 1.59 liters. Where U = used oil requirement X = additive requirement (8 % (Caltex lubricants, 2013)) 2. Amount of acetic acid required (A.A). A.A. = U × Acid oil ratio = 1.59x10% =0.159 3. Amount of additive required (Additive). Additive
= 8% × 1 liter. = 0.08
4. Power required for the process (
)
(
) (
)
a) Power consumed during evaporation. (
)
(
)
Power consumed during adsorption
( )
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Table A-2: Comparison of new and used oil properties.
Test Water content (%v/v) Fuel dilution (%v/v) Pour point oC Benzene insoluble Neutralization Number (mg KOH/g) Soot content Density (25oC) Lead Calcium Sodium Iron Potassium
Sample New Oil used oil 0.0 0.1 0.0 2.9 -20.0 -20.0 0.0 0.9 0.4 2.6 0.0 0.88 0.93 Metal content (ppm) 0.0 2813.0 543.2 1194 0.0 9.5 0.0 0.0 0.0 0.0
General range for used oil 1.2 - 1.6 -18 - -25 1.17 - 3.33 4.0 - 14.26 5000 - 12000 784 - 2243 27 - 368 15 - 38 24 - 434
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Table A- 3: Comparison of economic aspect of treatment technologies
Recycling Technology
Technology Maturity Energy Demand Recovery Rate Quality of Reclaimed Oil Equipment Demand Operating Cost
Re-Refining
Reprocessing
Incineration
Plant Scale High > 63% Good High High
Plant Scale Low > 58% Fair Low Low
Low -
Table A- 4: Density of Oil when treated different concentration of adsorbent Oil type 0% 5% 10% 15% 20%
10% Adsorbent 20% Adsorbent Density(g/ml) Density(g/ml) Density(g/ml) 93 93 93 0.93 0.90 0.90 0.92 0.90 0.89 0.91 0.89 0.88 0.91 0.90 0.88 0% Adsorbent
Table A- 5 Average used oil sample properties measured at SGS laboratories. Property Soot content Viscocity 100oC ASTM D7279 Kinematic Viscosity 100 cst Flash Point oC Silver – Ag mg/l Silicon – Si mg/l Aluminium – Al mg/l Sodium – Na mg/l Iron – Fe mg/l Calcium – Ca mg/l Density – g/cc
Amount <0.01 14.9
Property Tin – Sn mg/l Copper – Cu mg/l
Amount <0.08 3.1
> 180 < 0.01 4.8 1.6 58 9.4 1194 0.93
Lead – Pb mg/l Chronium – Cr mg/l Nickel- Ni mg/l Zinc – Zn mg/l Vanadium - V mg/l Magnesium – Mg mg/l Water content %
0.68 0.42 0.49 404 <0.01 0.16 <0.04