Studies on the improvement of biogas production from anaerobic digestion of animal wastes
- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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Performance and emission evaluation of a bi-fuel car
- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
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- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
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Torrefaction of landfill food waste and characterization of the torrefied biomass
- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
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- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
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Phase equilibria modelling for volatile organic compounds in biodiesel using UNIFAC Group contribution methods
- Authors: Ramdharee, Sashay
- Date: 2016
- Subjects: Volatile organic compounds - Environmental aspects , Volatile organic compounds - Analysis , Chemical equilibrium , Phase rule and equilibrium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242876 , uj:25064
- Description: M.Tech. (Chemical Engineering) , Abstract: The legislation on environmental conservation in South Africa, as outlined in the National Environmental Management: Air Quality Act 39 of 2004, has forced all industries to closely monitor any effluents emitted into the environment. This work investigated the suitability of biodiesel (specifically methyl linolenate, methyl palmitate, methyl oleate and methyl stearate) as an absorbent for the recovery of VOCs from waste gas process streams through absorption. The objective was to predict the vapour liquid equilibria (VLE) data, in the form of infinite dilution activity coefficients for five VOC families, in fatty acid methyl ester solvents. The Original Universal Functional Group Activity Coefficient (UNIFAC) model (Fredenslund et al., 1975), Modified UNIFAC (Larsen et al., 1981) and Modified UNIFAC (Bastos et al., 1988) were used to predict the infinite dilution activity coefficients. The solubility of alkanes, amines, alkenes, organic acids and alcohols showed a decrease in activity coefficients with an increase in molecular weight. Shorter chained esters with a lower carbon count had higher activity coefficients when compared to longer chained esters with a higher carbon count. The solubility of VOCs in biodiesel decreases with increases in ester hydrocarbon unsaturation. This work also investigated the vapour liquid equilibria (VLE) data in the form of infinite dilution activity coefficients for five VOC families, in fatty acid methyl ester solvents at varying temperature. Alkanes, alcohols and acids/ester interactions showed increases in activity coefficients with increases in temperature. The influence of temperature on the activity coefficients for alkene and amine families was negligible. The solubility of VOCs in biodiesel decreased with increases in ester hydrocarbon unsaturation and the solubility increased with an increase in ester molecular weight. The results for the modified UNIFAC Bastos and UNIFAC Fredenslund showed good agreement with the experimental measurements for 1,2-Dichloroethane, 2-Chlorobutane and Toluene. This study substantiates the hypothesis biodiesel is well suited as an absorbent for removal of VOC solutes from waste gas streams. The results presented in this report are comprehensive and it is envisaged that this work will assist engineers in making informed decisions when using biodiesel as a scrubbing solvent.
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- Authors: Ramdharee, Sashay
- Date: 2016
- Subjects: Volatile organic compounds - Environmental aspects , Volatile organic compounds - Analysis , Chemical equilibrium , Phase rule and equilibrium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242876 , uj:25064
- Description: M.Tech. (Chemical Engineering) , Abstract: The legislation on environmental conservation in South Africa, as outlined in the National Environmental Management: Air Quality Act 39 of 2004, has forced all industries to closely monitor any effluents emitted into the environment. This work investigated the suitability of biodiesel (specifically methyl linolenate, methyl palmitate, methyl oleate and methyl stearate) as an absorbent for the recovery of VOCs from waste gas process streams through absorption. The objective was to predict the vapour liquid equilibria (VLE) data, in the form of infinite dilution activity coefficients for five VOC families, in fatty acid methyl ester solvents. The Original Universal Functional Group Activity Coefficient (UNIFAC) model (Fredenslund et al., 1975), Modified UNIFAC (Larsen et al., 1981) and Modified UNIFAC (Bastos et al., 1988) were used to predict the infinite dilution activity coefficients. The solubility of alkanes, amines, alkenes, organic acids and alcohols showed a decrease in activity coefficients with an increase in molecular weight. Shorter chained esters with a lower carbon count had higher activity coefficients when compared to longer chained esters with a higher carbon count. The solubility of VOCs in biodiesel decreases with increases in ester hydrocarbon unsaturation. This work also investigated the vapour liquid equilibria (VLE) data in the form of infinite dilution activity coefficients for five VOC families, in fatty acid methyl ester solvents at varying temperature. Alkanes, alcohols and acids/ester interactions showed increases in activity coefficients with increases in temperature. The influence of temperature on the activity coefficients for alkene and amine families was negligible. The solubility of VOCs in biodiesel decreased with increases in ester hydrocarbon unsaturation and the solubility increased with an increase in ester molecular weight. The results for the modified UNIFAC Bastos and UNIFAC Fredenslund showed good agreement with the experimental measurements for 1,2-Dichloroethane, 2-Chlorobutane and Toluene. This study substantiates the hypothesis biodiesel is well suited as an absorbent for removal of VOC solutes from waste gas streams. The results presented in this report are comprehensive and it is envisaged that this work will assist engineers in making informed decisions when using biodiesel as a scrubbing solvent.
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Enhancing biogas production from lawn grass by optimizing selected factors involved in anaerobic digestion
- Authors: Sibiya, Noxolo Thandeka
- Date: 2016
- Subjects: Biomass energy , Renewable energy resources , Refuse and refuse disposal - Biodegradation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225327 , uj:22755
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas technology via anaerobic digestion (AD) is considered as an alternative option to reduce the emission of greenhouse gases, improve energy efficiency and address increasing dependency on imported fossil fuel. Although biogas can be produced easily, numerous researches have shown that the efficiency of methane production, especially from grass, is not optimal due to some factors affecting the AD rocess directly and indirectly. Therefore, this master’s dissertation focuses on evaluating the techniques that can be used to enhance the biodegradability of lawn grass, and subsequently improves biogas and methane production under anaerobic condition. The effects of operational parameters such as temperature, pH, loading rate, and retention time were evaluated. Techniques including recirculation of digestate, alkaline (NaOH) pre-treatment and co-digestion were also investigated. The characteristics of the substrate were determined in order to verify the suitability of the substrate for AD process. Biogas production from lawn grass was studied in the batch laboratory scale digester (1000 mL) with the working volume of 800 mL. Automatic Methane Potential Test System (AMPTS II) was used to measure bio-methane potential and methane content was measured using gas chromatography (GC, claurus 580). Although all the techniques have proven to enhance biogas and methane production from lawn grass, co-digestion has been considered as the most preferable method for enhanced biogas and methane production. The highest biogas yield was obtained when grass was co-digested with cow dung, while the maximum methane was observed when pig manure was a co-substrate with grass at the ratio of 1:1 (25:25 g). The suitable environmental condition for AD on this study was found to be at 45 ºC and pH of 6.5, while the optimal retention time was found to be 8 days, regardless of the effect of temperature and pH. An increase of biogas and methane production by 10% was observed when the digester loading rate was increased from 20 g/L to 60 g/L, whereas higher methane content was obtained in a digester with 30 % recycled solid digestate. It was also found that pre-treating lawn grass with 0.093 M NaOH at 40 and 55 ºC prior the AD process resulted in a significant increase in bio-methane potential from 813 to 1204 NmL and methane content from 40 to 52 %.
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- Authors: Sibiya, Noxolo Thandeka
- Date: 2016
- Subjects: Biomass energy , Renewable energy resources , Refuse and refuse disposal - Biodegradation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225327 , uj:22755
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas technology via anaerobic digestion (AD) is considered as an alternative option to reduce the emission of greenhouse gases, improve energy efficiency and address increasing dependency on imported fossil fuel. Although biogas can be produced easily, numerous researches have shown that the efficiency of methane production, especially from grass, is not optimal due to some factors affecting the AD rocess directly and indirectly. Therefore, this master’s dissertation focuses on evaluating the techniques that can be used to enhance the biodegradability of lawn grass, and subsequently improves biogas and methane production under anaerobic condition. The effects of operational parameters such as temperature, pH, loading rate, and retention time were evaluated. Techniques including recirculation of digestate, alkaline (NaOH) pre-treatment and co-digestion were also investigated. The characteristics of the substrate were determined in order to verify the suitability of the substrate for AD process. Biogas production from lawn grass was studied in the batch laboratory scale digester (1000 mL) with the working volume of 800 mL. Automatic Methane Potential Test System (AMPTS II) was used to measure bio-methane potential and methane content was measured using gas chromatography (GC, claurus 580). Although all the techniques have proven to enhance biogas and methane production from lawn grass, co-digestion has been considered as the most preferable method for enhanced biogas and methane production. The highest biogas yield was obtained when grass was co-digested with cow dung, while the maximum methane was observed when pig manure was a co-substrate with grass at the ratio of 1:1 (25:25 g). The suitable environmental condition for AD on this study was found to be at 45 ºC and pH of 6.5, while the optimal retention time was found to be 8 days, regardless of the effect of temperature and pH. An increase of biogas and methane production by 10% was observed when the digester loading rate was increased from 20 g/L to 60 g/L, whereas higher methane content was obtained in a digester with 30 % recycled solid digestate. It was also found that pre-treating lawn grass with 0.093 M NaOH at 40 and 55 ºC prior the AD process resulted in a significant increase in bio-methane potential from 813 to 1204 NmL and methane content from 40 to 52 %.
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Recovery of base oil from lithium based waste lubricating grease by solvent-flocculation extraction
- Authors: Diphare, Motsumi Joseph
- Date: 2015-03-26
- Subjects: Lubrication and lubricants , Lubricating oils - Recycling , Petroleum waste
- Type: Thesis
- Identifier: uj:13524 , http://hdl.handle.net/10210/13575
- Description: M.Tech. (Mechanical Engineering) , This study investigated process development of recovering base oils from waste lithium based lubricating grease using a novel combination of thermal degradation in an aqueous caustic solution and solvent extraction. Lubricating greases consist of a thickening agent dispersed in mineral or synthetic oil, forming a colloidal suspension [1]. Large and increasing volumes of used lubricating oil and grease are produced each year and are considered hazardous wastes. During operation, grease suffers mechanical and thermal degradation [2]. Subsequently, it is regarded as waste and it must be disposed. The waste oil should be collected and recycled not only to prevent the environmental pollution but also to preserve natural resources. Solvent extraction is the preferred method to recycle waste lubricants as it is cost-effective and requires no further purification of the product [3]. The influence of extraction temperature, agitation strength, extraction time, degrading agent concentration, degrading agent-to-grease and solvent-to-sludge mixing ratios on base oil recovery from waste lubricating grease was investigated. This study further optimised the process by studying the influence of various degrading agents (LiOH, NaOH and KOH) and solvents (n-hexane, toluene, heptane, butane, hexanol and acetone) on oil recovery. Oil recovery was enhanced by increase in both extraction temperature, time and agitation speed. The optimum extraction time was found to be 12 minutes. KOH was found to be the optimum degrading agent compared to LiOH and NaOH. Oil recovery also increased from 8.04% to 36.87% with increase in KOH m/m from 5% to 30%. The recovery also increased with an increase of solvent-to-sludge ratio up to 1:6. n-Hexane gave the highest recovery of 74.39% while acetone gave the lowest of 7.43%. A solvent recovery of 82.6% to 88% was obtained through fractional distillation. The study also investigated the differences between virgin and recycled oil using atomic absorption (AA), inductively coupled plasma (ICP) and Fourier transform infrared radiation (FTIR). Rheological studies of waste grease derived oil (WGDO) were also performed. ICP results showed traces of some elements such as Fe, Cu, Si, Ni and Al at a concentration of less than 0.9 mg/L. Oxidation was observed to occur at a band length of 1716 cm-1 while additives were identified at 1670 - 1725 cm-1. The oil viscosity slightly increased with increasing shear rate at temperatures between 60°C and 120°C. The shear rate was varied from 200 to 1000 1/s, with a viscosity convergence at 100°C. A financial economic model was applied to investigate the feasibility of the recycling technology. For 800 kg/day treatment plant, an investment of R 6,031,304.27 is required with a potential return on investment of 40%. Recovery was found to be favourable option compared to landfilling as it offers both economic and environmental benefits.
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- Authors: Diphare, Motsumi Joseph
- Date: 2015-03-26
- Subjects: Lubrication and lubricants , Lubricating oils - Recycling , Petroleum waste
- Type: Thesis
- Identifier: uj:13524 , http://hdl.handle.net/10210/13575
- Description: M.Tech. (Mechanical Engineering) , This study investigated process development of recovering base oils from waste lithium based lubricating grease using a novel combination of thermal degradation in an aqueous caustic solution and solvent extraction. Lubricating greases consist of a thickening agent dispersed in mineral or synthetic oil, forming a colloidal suspension [1]. Large and increasing volumes of used lubricating oil and grease are produced each year and are considered hazardous wastes. During operation, grease suffers mechanical and thermal degradation [2]. Subsequently, it is regarded as waste and it must be disposed. The waste oil should be collected and recycled not only to prevent the environmental pollution but also to preserve natural resources. Solvent extraction is the preferred method to recycle waste lubricants as it is cost-effective and requires no further purification of the product [3]. The influence of extraction temperature, agitation strength, extraction time, degrading agent concentration, degrading agent-to-grease and solvent-to-sludge mixing ratios on base oil recovery from waste lubricating grease was investigated. This study further optimised the process by studying the influence of various degrading agents (LiOH, NaOH and KOH) and solvents (n-hexane, toluene, heptane, butane, hexanol and acetone) on oil recovery. Oil recovery was enhanced by increase in both extraction temperature, time and agitation speed. The optimum extraction time was found to be 12 minutes. KOH was found to be the optimum degrading agent compared to LiOH and NaOH. Oil recovery also increased from 8.04% to 36.87% with increase in KOH m/m from 5% to 30%. The recovery also increased with an increase of solvent-to-sludge ratio up to 1:6. n-Hexane gave the highest recovery of 74.39% while acetone gave the lowest of 7.43%. A solvent recovery of 82.6% to 88% was obtained through fractional distillation. The study also investigated the differences between virgin and recycled oil using atomic absorption (AA), inductively coupled plasma (ICP) and Fourier transform infrared radiation (FTIR). Rheological studies of waste grease derived oil (WGDO) were also performed. ICP results showed traces of some elements such as Fe, Cu, Si, Ni and Al at a concentration of less than 0.9 mg/L. Oxidation was observed to occur at a band length of 1716 cm-1 while additives were identified at 1670 - 1725 cm-1. The oil viscosity slightly increased with increasing shear rate at temperatures between 60°C and 120°C. The shear rate was varied from 200 to 1000 1/s, with a viscosity convergence at 100°C. A financial economic model was applied to investigate the feasibility of the recycling technology. For 800 kg/day treatment plant, an investment of R 6,031,304.27 is required with a potential return on investment of 40%. Recovery was found to be favourable option compared to landfilling as it offers both economic and environmental benefits.
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Buffering efficacy and interaction of minerals in clayey soil with contaminants from landfills and acid mine drainage
- Agbenyeku, Emem-Obong Emmanuel
- Authors: Agbenyeku, Emem-Obong Emmanuel
- Date: 2016
- Subjects: Acid mine drainage - Environmental aspects , Mines and mineral resources - Environmental aspects , Fills (Earthwork) , Clay soils
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/225168 , uj:22735
- Description: Abstract: The extent to which mining and landfilling activities in South Africa impact the environment and invariably have consequential effects on the health of inhabitants has remained insistently dire. Hence, for the study to assess the efficacy and potency of three subtropical clayey soils as buffers of contaminants, their compatibility with acid mine drainage (AMD) and municipal solid waste (MSW) landfill leachate was investigated through geochemical, mechanical and soil hydraulic conductivity testing, batch sorption, column diffusion, chemical and x-ray diffraction studies. The infusion of roughly 18-24 pore volumes of AMD through the soils triggered a dissolution of metals from soil grains. The soils adsorbed more potassium than sodium after 4-10 pore volumes of MSW landfill leachate intrusion. Generally, the effluent breakthrough curves of the respective soils showed early arrival and delayed desorption of magnesium and calcium while iron and nearly all heavy metals in the leachate were buffered. The effective diffusion coefficients for potassium and sodium were found to range between 1.5-1.9 × 10-10 m/s and 7.1-13 × 10-10 m/s respectively. The source solutions used as permeants in the study triggered desorption of chemical species from the exchangeable sites of the clayey soil minerals leading to the alteration, formation and dissolution of other soil minerals. Irrespective of the physicochemical and mineralogical transformations that occurred in the respective soils, the final hydraulic conductivity values satisfied the maximum soil acceptance criterion by roughly two order of magnitude lower than 1 × 10-9 m/s specified for clay liner construction in South Africa. Nonetheless, the three sampled natural subtropical soils were found to be incompatible with AMD and therefore, should not be solely used as naked natural buffers for AMD containment and related acid producing wastes, as they were mostly inadequate in buffering the potentially harmful AMD chemical species. Furthermore, it is not advisable to use the respective naked soils alone as natural buffers in MSW landfills with high concentrations of leachate chemical species as every soil system has a threshold. The soils can however, be used in composite barrier lining systems. This is such that, complex mechanisms provide the natural soils in-situ and ex-situ with their mechanical and physical behaviours including; adsorption, desorption, attenuation, complexation, pressure and transformations which contribute to the development of changes in net repulsion/attraction and natural bonding in the respective soils. , D.Phil. (Civil Engineering Science)
- Full Text:
- Authors: Agbenyeku, Emem-Obong Emmanuel
- Date: 2016
- Subjects: Acid mine drainage - Environmental aspects , Mines and mineral resources - Environmental aspects , Fills (Earthwork) , Clay soils
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/225168 , uj:22735
- Description: Abstract: The extent to which mining and landfilling activities in South Africa impact the environment and invariably have consequential effects on the health of inhabitants has remained insistently dire. Hence, for the study to assess the efficacy and potency of three subtropical clayey soils as buffers of contaminants, their compatibility with acid mine drainage (AMD) and municipal solid waste (MSW) landfill leachate was investigated through geochemical, mechanical and soil hydraulic conductivity testing, batch sorption, column diffusion, chemical and x-ray diffraction studies. The infusion of roughly 18-24 pore volumes of AMD through the soils triggered a dissolution of metals from soil grains. The soils adsorbed more potassium than sodium after 4-10 pore volumes of MSW landfill leachate intrusion. Generally, the effluent breakthrough curves of the respective soils showed early arrival and delayed desorption of magnesium and calcium while iron and nearly all heavy metals in the leachate were buffered. The effective diffusion coefficients for potassium and sodium were found to range between 1.5-1.9 × 10-10 m/s and 7.1-13 × 10-10 m/s respectively. The source solutions used as permeants in the study triggered desorption of chemical species from the exchangeable sites of the clayey soil minerals leading to the alteration, formation and dissolution of other soil minerals. Irrespective of the physicochemical and mineralogical transformations that occurred in the respective soils, the final hydraulic conductivity values satisfied the maximum soil acceptance criterion by roughly two order of magnitude lower than 1 × 10-9 m/s specified for clay liner construction in South Africa. Nonetheless, the three sampled natural subtropical soils were found to be incompatible with AMD and therefore, should not be solely used as naked natural buffers for AMD containment and related acid producing wastes, as they were mostly inadequate in buffering the potentially harmful AMD chemical species. Furthermore, it is not advisable to use the respective naked soils alone as natural buffers in MSW landfills with high concentrations of leachate chemical species as every soil system has a threshold. The soils can however, be used in composite barrier lining systems. This is such that, complex mechanisms provide the natural soils in-situ and ex-situ with their mechanical and physical behaviours including; adsorption, desorption, attenuation, complexation, pressure and transformations which contribute to the development of changes in net repulsion/attraction and natural bonding in the respective soils. , D.Phil. (Civil Engineering Science)
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Optimization of biogas production from City of Johannesburg market waste by anaerobic digestion for sustainable energy development
- Authors: Singh, Suraya
- Date: 2018
- Subjects: Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295034 , uj:32113
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas, as a renewable energy source, is regarded as a viable alternative to the burning of fossil fuels to meet energy demands. The production of biogas to meet energy needs not only has environmental benefits such as reduction in greenhouse gas emissions and responsible waste disposal but also socio-economic benefits, especially when applied to a rural setting, such as improvements in employment, professional qualification and overall food supply of the local population. The main objective of this study was to determine optimum biogas production from City of Johannesburg (CoJ) market waste, composed primarily of fruit and vegetable waste (FVW), under anaerobic condition. The influence of operational factors such as temperature, pH, loading rate and retention time were evaluated. The co-digestion of FVW with cow dung (CD) at varying mixing ratios was also evaluated as a technique to optimize biogas production. Mono-digestion of FVW at thermophilic temperatures were optimum for both biogas and methane production. Changes in organic loading rate (OLR) indicated that with increases in OLR there were increases in both biogas and methane production. The highest biogas and methane production occurred for an OLR of FVW: 200g. The optimum retention time for biogas and methane production was determined to be 14 days and 10 days respectively. The explanation for the prolonged biogas and methane production has been accredited to the fact that there was a greater component of biodegradable material available for breakdown by methanogenic bacteria but even more critical than that was the alkaline pH of 7.18 of this substrate mixture at the commencement of digestion. However, experimental results indicated that co-digestion is the preferred method to optimize biogas and methane production. According to the experimental results obtained, a mixing ratio of FVW: CD of 20:40g is the optimum substrate mixture for both biogas and methane production. The optimum environmental conditions for co-digestion was found to be at 37°C with a pH range between 7.12 to 7.18, while the optimal retention time was found to be 33 days. It was found that when the mixing ratios contained between 50% and less cow dung with corresponding increases in FVW, there were drastic reductions in the digester stability and overall production rates for those substrate mixing ratios. It was therefore concluded that in order to ensure sustained and good biogas and methane production via co-digestion, the CD content should remain above 50% of the total mixture.
- Full Text:
- Authors: Singh, Suraya
- Date: 2018
- Subjects: Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295034 , uj:32113
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas, as a renewable energy source, is regarded as a viable alternative to the burning of fossil fuels to meet energy demands. The production of biogas to meet energy needs not only has environmental benefits such as reduction in greenhouse gas emissions and responsible waste disposal but also socio-economic benefits, especially when applied to a rural setting, such as improvements in employment, professional qualification and overall food supply of the local population. The main objective of this study was to determine optimum biogas production from City of Johannesburg (CoJ) market waste, composed primarily of fruit and vegetable waste (FVW), under anaerobic condition. The influence of operational factors such as temperature, pH, loading rate and retention time were evaluated. The co-digestion of FVW with cow dung (CD) at varying mixing ratios was also evaluated as a technique to optimize biogas production. Mono-digestion of FVW at thermophilic temperatures were optimum for both biogas and methane production. Changes in organic loading rate (OLR) indicated that with increases in OLR there were increases in both biogas and methane production. The highest biogas and methane production occurred for an OLR of FVW: 200g. The optimum retention time for biogas and methane production was determined to be 14 days and 10 days respectively. The explanation for the prolonged biogas and methane production has been accredited to the fact that there was a greater component of biodegradable material available for breakdown by methanogenic bacteria but even more critical than that was the alkaline pH of 7.18 of this substrate mixture at the commencement of digestion. However, experimental results indicated that co-digestion is the preferred method to optimize biogas and methane production. According to the experimental results obtained, a mixing ratio of FVW: CD of 20:40g is the optimum substrate mixture for both biogas and methane production. The optimum environmental conditions for co-digestion was found to be at 37°C with a pH range between 7.12 to 7.18, while the optimal retention time was found to be 33 days. It was found that when the mixing ratios contained between 50% and less cow dung with corresponding increases in FVW, there were drastic reductions in the digester stability and overall production rates for those substrate mixing ratios. It was therefore concluded that in order to ensure sustained and good biogas and methane production via co-digestion, the CD content should remain above 50% of the total mixture.
- Full Text:
Integrated waste management development in the West Rand District Municipality
- Authors: Ginindza, Bongekile
- Date: 2017
- Subjects: Refuse disposal industry - South Africa - Gauteng , Refuse and refuse disposal - South Africa - Gauteng - Management , Refuse and refuse disposal - Environmental aspects , Waste minimization - South Africa - Gauteng
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242803 , uj:25055
- Description: Abstract: The West Rand District Municipality (WRDM) is currently experiencing major solid waste management and utilization challenges due to rapid population growth and increased waste generation in its four local municipalities, which are Mogale City Local Municipality (CLM), Westonaria Local Municipality (LM), Randfontein LM and Merafong CLM. Increased sustainable waste management and minimisation development have placed enormous pressure on the district. The study objectives were achieved by using a triangular method which included personal interviews, face-to-face questionnaires, site visits, landfill site operational reports, and document analyses. This research focused on the identification of gaps in the current waste management practices in each LM so that waste management planning can focus on addressing the major shortfalls in current waste management practices. The increased waste management demands on the municipality include storage, collection, and transportation facilities. Insufficient provision of these facilities often leads to improper waste management in the municipality. This often results in illegal dumping of waste, and improper management of hazardous or medical waste which cause significant health and environmental impacts. This inadequate management is escalated by insufficient involvement of the municipality in strict enforcement of bylaws, education, awareness creation and about waste management and minimisation strategies. Scavenging is the most important role in WRDM informal solid waste management in recycling, reduction, minimization and material recovery. There are poor waste minimisation programmes in place to encourage waste reduction, re-use and recycling initiatives for WRDM residents, townships and industries. Waste is not managed according to the waste hierarchy in WRDM and thus there is an increase of waste disposal to landfill sites. This has led to the rapid shrinking of landfill site airspace, soil pollution, scarce water resources and the release of landfill site gases or greenhouse gases into the atmosphere, which contribute to climate change. The operation of landfill sites in the WRDM currently do not comply with the license conditions and requirements DWAF (Department of Water Affairs and Forestry), for example leachate management, monitoring, operation, and airspace... , M.Tech. (Chemical Engineering)
- Full Text:
- Authors: Ginindza, Bongekile
- Date: 2017
- Subjects: Refuse disposal industry - South Africa - Gauteng , Refuse and refuse disposal - South Africa - Gauteng - Management , Refuse and refuse disposal - Environmental aspects , Waste minimization - South Africa - Gauteng
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242803 , uj:25055
- Description: Abstract: The West Rand District Municipality (WRDM) is currently experiencing major solid waste management and utilization challenges due to rapid population growth and increased waste generation in its four local municipalities, which are Mogale City Local Municipality (CLM), Westonaria Local Municipality (LM), Randfontein LM and Merafong CLM. Increased sustainable waste management and minimisation development have placed enormous pressure on the district. The study objectives were achieved by using a triangular method which included personal interviews, face-to-face questionnaires, site visits, landfill site operational reports, and document analyses. This research focused on the identification of gaps in the current waste management practices in each LM so that waste management planning can focus on addressing the major shortfalls in current waste management practices. The increased waste management demands on the municipality include storage, collection, and transportation facilities. Insufficient provision of these facilities often leads to improper waste management in the municipality. This often results in illegal dumping of waste, and improper management of hazardous or medical waste which cause significant health and environmental impacts. This inadequate management is escalated by insufficient involvement of the municipality in strict enforcement of bylaws, education, awareness creation and about waste management and minimisation strategies. Scavenging is the most important role in WRDM informal solid waste management in recycling, reduction, minimization and material recovery. There are poor waste minimisation programmes in place to encourage waste reduction, re-use and recycling initiatives for WRDM residents, townships and industries. Waste is not managed according to the waste hierarchy in WRDM and thus there is an increase of waste disposal to landfill sites. This has led to the rapid shrinking of landfill site airspace, soil pollution, scarce water resources and the release of landfill site gases or greenhouse gases into the atmosphere, which contribute to climate change. The operation of landfill sites in the WRDM currently do not comply with the license conditions and requirements DWAF (Department of Water Affairs and Forestry), for example leachate management, monitoring, operation, and airspace... , M.Tech. (Chemical Engineering)
- Full Text:
Biogas purification and upgrading for vehicular fuel application
- Authors: Maile, Olivia Ireen
- Date: 2016
- Subjects: Reneable energy sources , Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243015 , uj:25082
- Description: M.Tech. (Chemical Engineering) , Abstract: Energy is used in the form of electricity, heat, and fuel for lighting, cooking, transportation, and manufacturing of different kind of products. South Africa has faced a long-term struggle on energy shortages which may be related to the 20% growth in the country’s electricity consumption and underinvestment on energy. Thus, the need for producing clean energy from alternative renewable and sustainable energy sources remains an attractive technology. Biogas is energy produced by anaerobic digestion of biodegradable organic waste such as garden waste, food waste, municipal waste, industrial waste and sewage sludge. However, it may not be fully exploited because it contains impurities which limit its application. It can be purified and upgraded using techniques such as high-pressure water scrubbing, pressure swing adsorption, membrane separation, activated carbon sieve, cryogenic separation, chemical absorption. This study focuses on chemical absorption as it can yield biogas with over 95 % CH4 by volume. The substrate used to produce biogas in this study was grass inoculated with cow dung. Sodium hydroxide and acetic acid were used to adjust the pH of the feedstock. The chemicals absorbents of focus are sodium hydroxide, potassium hydroxide, ammonia solution and monoethanolamine. Two kinds of setups were used for this study; biochemical methane potential (BMP) assay tests using the Bioprocess Control AMPTS II and a custom made setup using Buchner flasks. Gas Chromatography was used for biogas analysis. The raw biogas contained on average 52% CH4 by volume which improved to over 80% CH4 after CO2 absorption. The CO2 removal efficiency improved from 22% to 66% for the alkalis and was also quite comparable for MEA and NH3 as it increased from 51% to 67%. The removal efficiency for NH3 and MEA increased from 69% to 79% on average with CH4 concentration reaching over 85% volume at 40 °C. The achievable calorific value for this study ranged from 25 to 33.5 MJ/Nm3.
- Full Text:
- Authors: Maile, Olivia Ireen
- Date: 2016
- Subjects: Reneable energy sources , Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243015 , uj:25082
- Description: M.Tech. (Chemical Engineering) , Abstract: Energy is used in the form of electricity, heat, and fuel for lighting, cooking, transportation, and manufacturing of different kind of products. South Africa has faced a long-term struggle on energy shortages which may be related to the 20% growth in the country’s electricity consumption and underinvestment on energy. Thus, the need for producing clean energy from alternative renewable and sustainable energy sources remains an attractive technology. Biogas is energy produced by anaerobic digestion of biodegradable organic waste such as garden waste, food waste, municipal waste, industrial waste and sewage sludge. However, it may not be fully exploited because it contains impurities which limit its application. It can be purified and upgraded using techniques such as high-pressure water scrubbing, pressure swing adsorption, membrane separation, activated carbon sieve, cryogenic separation, chemical absorption. This study focuses on chemical absorption as it can yield biogas with over 95 % CH4 by volume. The substrate used to produce biogas in this study was grass inoculated with cow dung. Sodium hydroxide and acetic acid were used to adjust the pH of the feedstock. The chemicals absorbents of focus are sodium hydroxide, potassium hydroxide, ammonia solution and monoethanolamine. Two kinds of setups were used for this study; biochemical methane potential (BMP) assay tests using the Bioprocess Control AMPTS II and a custom made setup using Buchner flasks. Gas Chromatography was used for biogas analysis. The raw biogas contained on average 52% CH4 by volume which improved to over 80% CH4 after CO2 absorption. The CO2 removal efficiency improved from 22% to 66% for the alkalis and was also quite comparable for MEA and NH3 as it increased from 51% to 67%. The removal efficiency for NH3 and MEA increased from 69% to 79% on average with CH4 concentration reaching over 85% volume at 40 °C. The achievable calorific value for this study ranged from 25 to 33.5 MJ/Nm3.
- Full Text:
Assessing the chemiabsorptive potency of chemical solvents and potential utilization of co2 after biogas upgrading
- Authors: Bambokela, Jonathan Empompo
- Date: 2019
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/399091 , uj:33252
- Description: Abstract : Please refer to full text to view abstract. , M.Tech. (Chemical Engineering)
- Full Text:
- Authors: Bambokela, Jonathan Empompo
- Date: 2019
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/399091 , uj:33252
- Description: Abstract : Please refer to full text to view abstract. , M.Tech. (Chemical Engineering)
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