Zachary Siagi - Academia.edu (original) (raw)

Papers by Zachary Siagi

Frontiers of Chemical Engineering in China, 2009

ABSTRACT This study presents findings from experiments on the preparation and characterization of... more ABSTRACT This study presents findings from experiments on the preparation and characterization of locally available fly ash, quicklime and the CaO/fly ash sorbent, synthesized using the atmospheric hydration process. The CaO was obtained from calcination of limestone in a laboratory kiln at a temperature of 900°C. The sorbents were prepared under different hydration conditions: CaO/fly ash weight ratio (1°1 to 1°3), hydration temperature (55°C–75°C) and hydration period (4–8 h). Results show that the specific surface area of CaO/ fly ash sorbents (8.8–23.6 m2/g) was higher than that of the CaO (4.78 m2/g) at all preparation conditions. The SEM micrographs show that the prepared sorbent had a more porous structure than either the fly ash or the CaO. The X-ray diffraction (XRD) analysis shows the presence of complex compounds containing calcium silicate hydrate in the synthesized sorbents. This contributed to the high BET specific surface area. The Brunauer-Emmett-Teller (BET) specific surface area was found to decrease with increase in the amount of fly ash with the ratio of 1:1 (CaO/Fly ash) giving the highest value. It was also found that an increase in the hydration time resulted in an increased BET specific surface area, although there was only a slight effect on the same by an increase in temperature.

Journal of Energy

Gadam sorghum stalks are agricultural residues which can be hydrolyzed into fermentable sugars th... more Gadam sorghum stalks are agricultural residues which can be hydrolyzed into fermentable sugars that can be used to produce bioethanol which is a renewable source of energy. In order to produce bioethanol from lignocellulosic biomass such as Gadam sorghum stalks, several processes including hydrolysis are involved. However, the use of lignocellulosic biomass for bioethanol production is hindered by the low yield of fermentable sugars obtained during hydrolysis. The lack of sufficient information on optimal conditions governing hydrolysis of lignocellulosic biomass leads to inefficient process which hinders the economic viability of large-scale bioethanol production. The objective of this study was to optimize reaction conditions involved in concentrated sulphuric acid hydrolysis of Gadam sorghum stalks. During hydrolysis, the conditions that were varied included temperature (40°C–80°C), time (30-90 minutes), and concentration of acid (30%-70%, w / w ). Central composite rotatable des...

European Journal of Energy Research

Knowing the determinants of household utilization and changing behaviour is an important element ... more Knowing the determinants of household utilization and changing behaviour is an important element in understanding the pathways towards clean, sustainable and modern household energy sources. This study, therefore, examines the drivers of household energy usage and choices in Western Kenya using structural equation modelling from 560 sampled households. The research was carried out in Western Kenya (Uasin Gishu and Bungoma counties) from a target household of 663,000. Data was collected using a structured questionnaire and were analyzed to find standard estimate (path coefficients), standard error, critical ratios and the level of significance using AMOS version 23. SEM analysis found that education level, income, residential status, peri urbanization, house size, house composition, age and gender of the household head were the determinants of household energy choices and changing behaviour among households both for cooking. On the other hand, SEM showed that household energy choices...

Utilization of Thermal Potential of Abandoned Wells, 2022

Advances in Phytochemistry, Textile and Renewable Energy Research for Industrial Growth, 2022

Sugar cane vinasse and maize stalks waste disposal poses serious challenges to the environment. H... more Sugar cane vinasse and maize stalks waste disposal poses serious challenges to the environment. However, anaerobic digestion is an attractive treatment method for these wastes. The current study therefore established the suitability of theses wastes for anaerobic digestion. Specifically, the study aimed at characterizing the substrates and anaerobic digestion of the substrates. The raw materials were collected from Muhoroni Sugar Company and Uasin-Gishu county maize farms, respectively. The pH, moisture content, chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), total organic carbon (TOC), nitrogen content, and CN ratio were determined based on standard methods. Experiment setups were run depending on batch experiment.

, is my own original work and has not previously been submitted to any other institution of highe... more , is my own original work and has not previously been submitted to any other institution of higher education. I further declare that all sources cited or quoted are indicated and acknowledged by means of a comprehensive list of references". Siagi Otara Zachary i This research is dedicated to: My parents And My son Richard Whose love and support has seen me this far. ii ACKNOWLEDGEMENT Many individuals and institutions have contributed either directly or indirectly to the accomplishment of this study. Due to constraints of space, I will only mention a few by name. To my supervisor, Prof. Makame Mbarawa, thank you for the assistance, support, and guidance during the entire study period. Thank you for believing in me and for encouraging me to be all that I am. Dr Mark Van Der Riet deserves credit for his idea for the ranking of South African sorbents, which is the core of the thesis. To Dr. AV Kolesnikov for accepting to be my co-supervisor. Special thanks to Naushaad of eskom for his tireless efforts in acquiring and characterizing the study materials. Thanks to Prof Rahman, Dr Lee, and Irvan Dahlan of the Universiti Sains Malaysia for their assistance during the laboratory tests and for making my stay in Malaysia a memorable one. My gratitude to all my friends and colleagues at the Department of Mechanical Engineering of the Tswane University of Technology for creating an inspiring atmosphere in which the current work was carried out. I acknowledge the financial support of the Tswane University of Technology, the German Academic Exchange Program (DAAD), Technology Services Internationaleskom, and NRF/THRIP funding. I also thank Moi University for granting me a study leave. To my host country, South Africa, the Rainbow Nation for providing the opportunity. Last but not least to my parents and my son, Richard, for their support and patience.

International Journal of Energy and Environmental Engineering

Journal of Energy, 2022

Used tyres are not biodegradable, and the current methods of disposal pose a threat to the enviro... more Used tyres are not biodegradable, and the current methods of disposal pose a threat to the environment. Such tyres can be valorised through decomposition to produce liquid fuel, an alternative diesel fuel, using thermal pyrolysis technique. Microwave pyrolysis is an alternate method which uses microwave irradiation, saves energy, and is better environmentally. The main objective of this study was to perform microwave pyrolysis of used tyres to produce liquid fuel and compare with thermal pyrolysis. The specific objectives were to study the effects of pyrolysis operating variables and optimization of liquid fuel yield for thermal pyrolysis, compare with microwave pyrolysis, and characterize the liquid fuel. Thermal pyrolysis variables were reaction temperature, reaction time, and particle size. Thermal pyrolysis reaction temperatures were 200, 300, 400, 500, 600, and 700°C; reaction time 10, 20, 30, 40, 50, 60, 70, 80, 100, and 120 minutes. Particle sizes were 25, 50, 60, 100, 125, a...

Journal of Energy, 2020

The present technology of transesterification of vegetable oils to produce biodiesel, which is su... more The present technology of transesterification of vegetable oils to produce biodiesel, which is suited to replace petrodiesel, has economic challenges, and therefore, alternative sources are being explored. Microalgae, a renewable, third-generation biofuel resource, have the potential to become a viable feedstock due to their high oil content and environmentally friendly nature. The present study investigates the effect of microwave irradiation on the simultaneous extraction and transesterification of algae lipids to produce fatty acid methyl ester (FAME), in a batch reaction system using sulphuric acid catalyst. In situ transesterification combines the two steps of lipid extraction and transesterification into a single step. The microwave synthesis unit comprised of a 3-neck round bottom flask inside a 1300-Watt microwave oven, fitted with a quick-fit condenser and having an external stirrer. Response surface methodology (RSM) was used to analyse the influence of process variables, ...

This paper is an effort to utilize abundant availability of natural fibres and waste plastics for... more This paper is an effort to utilize abundant availability of natural fibres and waste plastics for the development of composite materials based on polymer and particles of natural fibres for conservation of natural resources such as forests. Ensete false banana (EFB) fibres were used as reinforcement to obtain composites with melted waste polyethylene bottled as matrix phase. The composites were prepared by means of compression moulding, and then the effects of fibres loading on mechanical properties such as impact strength, flexural strength, and wear resistance were investigated. Water uptake was also studied. It was observed that the flexural modulus, compressive strength and flexural strength of treated EBF reinforced PE increased linearly with increment of fibres loadings. This trend was similar for impact strength where it exhibited a slight reduction at the initial stage but increased later as the fibres loading increased. It was also observed the water absorption increased wi...

International journal of energy engineering, 2020

A static aerated Compost Reactor (CR) was developed in Kitele, Kenya, and used for evaluating the... more A static aerated Compost Reactor (CR) was developed in Kitele, Kenya, and used for evaluating the efficacy of generating, extraction, and utilization of compost heat as a source of clean energy. A Compost Heat Exchanger (COHE), hydronically operated, was developed in order to extract and transfer the heat. Energy generated by the compost reactor was calculated, using temperature profiles, captured by the TC-08 data loggers via the K type (PTFE) thermocouples. Heated water to 55°C was obtainable. The total extracted energy from compost was and 174 kWh.

Limited information on optimal biofuel production conditions leads to non-economical and ineffici... more Limited information on optimal biofuel production conditions leads to non-economical and inefficient process hence uncompetitive low grade biofuels. Fermentation process optimization is very crucial especially while using relatively low fermentable sugars substrates. In this research, banana peels derived from Ngombe cultivar were dried, ground into fine powder to pass through a 1 mm screen, and then hydrolyzed using 60% concentrated H 2 SO 4 at 50 0 C. Bioethanol was produced by anaerobic fermentation of the hydrolysate using Saccharomyces cerevisiae. Erlenmeyer Flasks fitted with non-return air valves were used as laboratory scale still reactors. Fermentation systems were subjected to various conditions based on half factorial Central Composite Rotatable Design (CCRD). Total Reducing Sugars (TRS) concentrations and bioethanol yield analyses were done by Dubois and Gas Chromatography methods respectively. Optimum bioethanol yield of 13.09 ml/L was obtained at 180 g/L substrate con...

Limited information on optimal biofuel production conditions leads to non-economical and ineffici... more Limited information on optimal biofuel production conditions leads to non-economical and inefficient process hence uncompetitive low grade biofuels. Fermentation process optimization is very crucial especially while using relatively low fermentable sugars substrates. In this research, banana peels derived from Ngombe cultivar were dried, ground into fine powder to pass through a 1 mm screen, and then hydrolyzed using 60% concentrated H 2 SO 4 at 50 o C. Bioethanol was produced by anaerobic fermentation of the hydrolysate using Saccharomyces cerevisiae. Erlenmeyer Flasks fitted with non-return air valves were used as laboratory scale still reactors. Fermentation systems were subjected to various conditions based on half factorial Central Composite Rotatable Design (CCRD). Total Reducing Sugars (TRS) concentrations and bioethanol yield analyses were done by Dubois and Gas Chromatography methods respectively. Optimum bioethanol yield of 13.09ml/L was obtained at 180 g/L substrate conce...

Journal of Combustion, 2021

Coal reserves at Mui and Taru in Kitui and Kilifi counties in Kenya are estimated to provide over... more Coal reserves at Mui and Taru in Kitui and Kilifi counties in Kenya are estimated to provide over 400 million tons. Being new discoveries, their properties were investigated using the ASTM standards, while the combustion characteristics were studied in a fluidized bed combustor (FBC). Proximate analyses of the Mui1, Mui2, and Taru coal samples were as follows: moisture content 3.75, 5.48, and 3.53%; volatile matter 59.25, 58.05, and 55.10%; ash content 9.25, 11.48, and 24.63%; and fixed carbon 27.80, 25.00, and 16.75%, respectively. Ultimate analysis for Mui1, Mui2, and Taru coal samples is as follows: sulphur wt.% 1.94, 1.89, and 1.07; carbon 65.68, 60.98, and 51.10%; hydrogen 5.97, 5.70, and 5.09%; nitrogen 0.92, 0.94, and 1.00%; and oxygen 11.62, 12.33, and 11.13%, respectively. Temperature–weight loss analysis showed that for Mui and Taru basin coal, devolatilization starts at 200°C and 250°C, and combustion was complete at 750°C and 650°C, respectively. The maximum temperature ...

Journal of Energy, 2021

Used tyres pose a threat to the environment, especially in developing countries, since the curren... more Used tyres pose a threat to the environment, especially in developing countries, since the current disposal methods lead to environmental pollution. Pyrolysis liquid from used tyres can be used as a source of fuel to replace petroleum diesel. Microwave pyrolysis is an alternative valorization process that is supposed to save energy and, therefore, is environment friendly. In the current study, microwave pyrolysis was used to produce liquid fuel. Processing variable levels for microwave were power levels of 20, 30, 40, 50, 60, 80, and 100%; the reaction times were 8, 13, 18, 23, and 28 minutes; and the particle sizes were 25, 50, 100, and 200 mm2. Design-Expert 13 was used for data analysis and optimization, and GC-MS was used for chemical composition analysis, while physiochemical properties were tested using standard methods. Response surface methodology (RSM) was used to study the effects of operating variables and identify the points of optimal yields. For microwave pyrolysis, th...

Cogent Engineering, 2020

While much research has been published on the Compost Heat Recovery Systems (CHRs), little has be... more While much research has been published on the Compost Heat Recovery Systems (CHRs), little has been documented on the design and performance evaluation of the Hydronic compost heat exchangers using numerical and computational methods, occasionally resulting in compost process inhibition. A CHRs (0.036 m3/7.2 m2) Hydronic-type heat exchanger and 12.43 m2/2.83 m3, compost reactor (CR), was designed and developed with the main objective of evaluating the design and its performance. The numerical design and performance evaluation was achieved by using Kern’s and the effectiveness and Number of Transfer Units methods (ε-NTU), respectively. Empirically, data were captured by using the Polytetrafluoroethylene (PTFE) thermocouples connected to the TC-8 Picolog Data loggers. Data validation (empirical and mathematical), was achieved by modifying a free computer-based software developed by the Chemical Engineering Calculations (CHECAL), into a Hydronic Compost Heat Exchanger design and perfor...

Research Journal of Applied Sciences, Engineering and Technology, 2014

Environmental pollution associated with petroleum sources of energy has reinvigorated interest in... more Environmental pollution associated with petroleum sources of energy has reinvigorated interest in the need to find "greener" electrical energy alternatives without a net carbon emission into the ecosystem to solve these problems. This research study analyzed electricity generation through bioelectrolytic reaction from an irish-potato, pineapple and tomato as electrolyte for the vegetative batteries with Zn/Cu as electrode. Treatments were performed on samples. In the first treatment, vegetative samples were heated at varied temperatures (19.5-80°C) and at varied holding times (20-60 min). In the second type, sample tissues were sandwiched between two aluminium plates through which pulses of ac current were passed at varied frequencies (2.63-100,000 Hz) maintained at 312 mV. With 108 cm 3 of sample, the battery capacities in untreated state were: irish-potato 53.7 mAh, pineapple 84.2 mAh and tomato 80.4 mAh; heat treated state: irish-potato 66.86 mAh, pineapple 116.4 mAh and tomato 108.8 mAh; while in electro orated state: irish-potato 68.9 mAh, pineapple 96.0 mAh and tomato 105.67 mAh. All these capacities were found experimentally to power a LED of forward current 1.44 mA, resistance of 270 Ω and supply voltage of 3V. Primary cost analyses showed that electro orated Zn/Cu vegetative battery samples generates portable energy of 5.74-50.54 cts/Wh, which is 14-124 times more than the currently available dry cell (D-type) cells retailed at 7.14 Ksh/Wh. Given that irish-potato is ranked fourth (after maize, wheat and rice) in the world and the second most important food crop after maize in Kenya in terms of abundance, it was recommended as an alternative vegetative battery.

Renewable Energy, 2001

Combustion mechanisms of two types of coffee husks have been studied using single particle combus... more Combustion mechanisms of two types of coffee husks have been studied using single particle combustion techniques as well as combustion in a pilot-scale fluidised bed facility (FBC), 150 mm in diameter and 9 m high. Through measurements of weight-loss and particle temperatures, the processes of drying, devolatilisation and combustion of coffee husks were studied. Axial temperature profiles in the FBC

Fuel, 2007

This study examines the effect of the chemical composition and origin on the performance of two c... more This study examines the effect of the chemical composition and origin on the performance of two calcitic and two dolomitic limestones from different sources in South Africa. The experiments were carried out in a fixed bed reactor maintained at 80° C. The raw sorbent ...

Frontiers of Chemical Engineering in China, 2009

ABSTRACT This study presents findings from experiments on the preparation and characterization of... more ABSTRACT This study presents findings from experiments on the preparation and characterization of locally available fly ash, quicklime and the CaO/fly ash sorbent, synthesized using the atmospheric hydration process. The CaO was obtained from calcination of limestone in a laboratory kiln at a temperature of 900°C. The sorbents were prepared under different hydration conditions: CaO/fly ash weight ratio (1°1 to 1°3), hydration temperature (55°C–75°C) and hydration period (4–8 h). Results show that the specific surface area of CaO/ fly ash sorbents (8.8–23.6 m2/g) was higher than that of the CaO (4.78 m2/g) at all preparation conditions. The SEM micrographs show that the prepared sorbent had a more porous structure than either the fly ash or the CaO. The X-ray diffraction (XRD) analysis shows the presence of complex compounds containing calcium silicate hydrate in the synthesized sorbents. This contributed to the high BET specific surface area. The Brunauer-Emmett-Teller (BET) specific surface area was found to decrease with increase in the amount of fly ash with the ratio of 1:1 (CaO/Fly ash) giving the highest value. It was also found that an increase in the hydration time resulted in an increased BET specific surface area, although there was only a slight effect on the same by an increase in temperature.

Journal of Energy

Gadam sorghum stalks are agricultural residues which can be hydrolyzed into fermentable sugars th... more Gadam sorghum stalks are agricultural residues which can be hydrolyzed into fermentable sugars that can be used to produce bioethanol which is a renewable source of energy. In order to produce bioethanol from lignocellulosic biomass such as Gadam sorghum stalks, several processes including hydrolysis are involved. However, the use of lignocellulosic biomass for bioethanol production is hindered by the low yield of fermentable sugars obtained during hydrolysis. The lack of sufficient information on optimal conditions governing hydrolysis of lignocellulosic biomass leads to inefficient process which hinders the economic viability of large-scale bioethanol production. The objective of this study was to optimize reaction conditions involved in concentrated sulphuric acid hydrolysis of Gadam sorghum stalks. During hydrolysis, the conditions that were varied included temperature (40°C–80°C), time (30-90 minutes), and concentration of acid (30%-70%, w / w ). Central composite rotatable des...

European Journal of Energy Research

Knowing the determinants of household utilization and changing behaviour is an important element ... more Knowing the determinants of household utilization and changing behaviour is an important element in understanding the pathways towards clean, sustainable and modern household energy sources. This study, therefore, examines the drivers of household energy usage and choices in Western Kenya using structural equation modelling from 560 sampled households. The research was carried out in Western Kenya (Uasin Gishu and Bungoma counties) from a target household of 663,000. Data was collected using a structured questionnaire and were analyzed to find standard estimate (path coefficients), standard error, critical ratios and the level of significance using AMOS version 23. SEM analysis found that education level, income, residential status, peri urbanization, house size, house composition, age and gender of the household head were the determinants of household energy choices and changing behaviour among households both for cooking. On the other hand, SEM showed that household energy choices...

Utilization of Thermal Potential of Abandoned Wells, 2022

Advances in Phytochemistry, Textile and Renewable Energy Research for Industrial Growth, 2022

Sugar cane vinasse and maize stalks waste disposal poses serious challenges to the environment. H... more Sugar cane vinasse and maize stalks waste disposal poses serious challenges to the environment. However, anaerobic digestion is an attractive treatment method for these wastes. The current study therefore established the suitability of theses wastes for anaerobic digestion. Specifically, the study aimed at characterizing the substrates and anaerobic digestion of the substrates. The raw materials were collected from Muhoroni Sugar Company and Uasin-Gishu county maize farms, respectively. The pH, moisture content, chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), total organic carbon (TOC), nitrogen content, and CN ratio were determined based on standard methods. Experiment setups were run depending on batch experiment.

, is my own original work and has not previously been submitted to any other institution of highe... more , is my own original work and has not previously been submitted to any other institution of higher education. I further declare that all sources cited or quoted are indicated and acknowledged by means of a comprehensive list of references". Siagi Otara Zachary i This research is dedicated to: My parents And My son Richard Whose love and support has seen me this far. ii ACKNOWLEDGEMENT Many individuals and institutions have contributed either directly or indirectly to the accomplishment of this study. Due to constraints of space, I will only mention a few by name. To my supervisor, Prof. Makame Mbarawa, thank you for the assistance, support, and guidance during the entire study period. Thank you for believing in me and for encouraging me to be all that I am. Dr Mark Van Der Riet deserves credit for his idea for the ranking of South African sorbents, which is the core of the thesis. To Dr. AV Kolesnikov for accepting to be my co-supervisor. Special thanks to Naushaad of eskom for his tireless efforts in acquiring and characterizing the study materials. Thanks to Prof Rahman, Dr Lee, and Irvan Dahlan of the Universiti Sains Malaysia for their assistance during the laboratory tests and for making my stay in Malaysia a memorable one. My gratitude to all my friends and colleagues at the Department of Mechanical Engineering of the Tswane University of Technology for creating an inspiring atmosphere in which the current work was carried out. I acknowledge the financial support of the Tswane University of Technology, the German Academic Exchange Program (DAAD), Technology Services Internationaleskom, and NRF/THRIP funding. I also thank Moi University for granting me a study leave. To my host country, South Africa, the Rainbow Nation for providing the opportunity. Last but not least to my parents and my son, Richard, for their support and patience.

International Journal of Energy and Environmental Engineering

Journal of Energy, 2022

Used tyres are not biodegradable, and the current methods of disposal pose a threat to the enviro... more Used tyres are not biodegradable, and the current methods of disposal pose a threat to the environment. Such tyres can be valorised through decomposition to produce liquid fuel, an alternative diesel fuel, using thermal pyrolysis technique. Microwave pyrolysis is an alternate method which uses microwave irradiation, saves energy, and is better environmentally. The main objective of this study was to perform microwave pyrolysis of used tyres to produce liquid fuel and compare with thermal pyrolysis. The specific objectives were to study the effects of pyrolysis operating variables and optimization of liquid fuel yield for thermal pyrolysis, compare with microwave pyrolysis, and characterize the liquid fuel. Thermal pyrolysis variables were reaction temperature, reaction time, and particle size. Thermal pyrolysis reaction temperatures were 200, 300, 400, 500, 600, and 700°C; reaction time 10, 20, 30, 40, 50, 60, 70, 80, 100, and 120 minutes. Particle sizes were 25, 50, 60, 100, 125, a...

Journal of Energy, 2020

The present technology of transesterification of vegetable oils to produce biodiesel, which is su... more The present technology of transesterification of vegetable oils to produce biodiesel, which is suited to replace petrodiesel, has economic challenges, and therefore, alternative sources are being explored. Microalgae, a renewable, third-generation biofuel resource, have the potential to become a viable feedstock due to their high oil content and environmentally friendly nature. The present study investigates the effect of microwave irradiation on the simultaneous extraction and transesterification of algae lipids to produce fatty acid methyl ester (FAME), in a batch reaction system using sulphuric acid catalyst. In situ transesterification combines the two steps of lipid extraction and transesterification into a single step. The microwave synthesis unit comprised of a 3-neck round bottom flask inside a 1300-Watt microwave oven, fitted with a quick-fit condenser and having an external stirrer. Response surface methodology (RSM) was used to analyse the influence of process variables, ...

This paper is an effort to utilize abundant availability of natural fibres and waste plastics for... more This paper is an effort to utilize abundant availability of natural fibres and waste plastics for the development of composite materials based on polymer and particles of natural fibres for conservation of natural resources such as forests. Ensete false banana (EFB) fibres were used as reinforcement to obtain composites with melted waste polyethylene bottled as matrix phase. The composites were prepared by means of compression moulding, and then the effects of fibres loading on mechanical properties such as impact strength, flexural strength, and wear resistance were investigated. Water uptake was also studied. It was observed that the flexural modulus, compressive strength and flexural strength of treated EBF reinforced PE increased linearly with increment of fibres loadings. This trend was similar for impact strength where it exhibited a slight reduction at the initial stage but increased later as the fibres loading increased. It was also observed the water absorption increased wi...

International journal of energy engineering, 2020

A static aerated Compost Reactor (CR) was developed in Kitele, Kenya, and used for evaluating the... more A static aerated Compost Reactor (CR) was developed in Kitele, Kenya, and used for evaluating the efficacy of generating, extraction, and utilization of compost heat as a source of clean energy. A Compost Heat Exchanger (COHE), hydronically operated, was developed in order to extract and transfer the heat. Energy generated by the compost reactor was calculated, using temperature profiles, captured by the TC-08 data loggers via the K type (PTFE) thermocouples. Heated water to 55°C was obtainable. The total extracted energy from compost was and 174 kWh.

Limited information on optimal biofuel production conditions leads to non-economical and ineffici... more Limited information on optimal biofuel production conditions leads to non-economical and inefficient process hence uncompetitive low grade biofuels. Fermentation process optimization is very crucial especially while using relatively low fermentable sugars substrates. In this research, banana peels derived from Ngombe cultivar were dried, ground into fine powder to pass through a 1 mm screen, and then hydrolyzed using 60% concentrated H 2 SO 4 at 50 0 C. Bioethanol was produced by anaerobic fermentation of the hydrolysate using Saccharomyces cerevisiae. Erlenmeyer Flasks fitted with non-return air valves were used as laboratory scale still reactors. Fermentation systems were subjected to various conditions based on half factorial Central Composite Rotatable Design (CCRD). Total Reducing Sugars (TRS) concentrations and bioethanol yield analyses were done by Dubois and Gas Chromatography methods respectively. Optimum bioethanol yield of 13.09 ml/L was obtained at 180 g/L substrate con...

Limited information on optimal biofuel production conditions leads to non-economical and ineffici... more Limited information on optimal biofuel production conditions leads to non-economical and inefficient process hence uncompetitive low grade biofuels. Fermentation process optimization is very crucial especially while using relatively low fermentable sugars substrates. In this research, banana peels derived from Ngombe cultivar were dried, ground into fine powder to pass through a 1 mm screen, and then hydrolyzed using 60% concentrated H 2 SO 4 at 50 o C. Bioethanol was produced by anaerobic fermentation of the hydrolysate using Saccharomyces cerevisiae. Erlenmeyer Flasks fitted with non-return air valves were used as laboratory scale still reactors. Fermentation systems were subjected to various conditions based on half factorial Central Composite Rotatable Design (CCRD). Total Reducing Sugars (TRS) concentrations and bioethanol yield analyses were done by Dubois and Gas Chromatography methods respectively. Optimum bioethanol yield of 13.09ml/L was obtained at 180 g/L substrate conce...

Journal of Combustion, 2021

Coal reserves at Mui and Taru in Kitui and Kilifi counties in Kenya are estimated to provide over... more Coal reserves at Mui and Taru in Kitui and Kilifi counties in Kenya are estimated to provide over 400 million tons. Being new discoveries, their properties were investigated using the ASTM standards, while the combustion characteristics were studied in a fluidized bed combustor (FBC). Proximate analyses of the Mui1, Mui2, and Taru coal samples were as follows: moisture content 3.75, 5.48, and 3.53%; volatile matter 59.25, 58.05, and 55.10%; ash content 9.25, 11.48, and 24.63%; and fixed carbon 27.80, 25.00, and 16.75%, respectively. Ultimate analysis for Mui1, Mui2, and Taru coal samples is as follows: sulphur wt.% 1.94, 1.89, and 1.07; carbon 65.68, 60.98, and 51.10%; hydrogen 5.97, 5.70, and 5.09%; nitrogen 0.92, 0.94, and 1.00%; and oxygen 11.62, 12.33, and 11.13%, respectively. Temperature–weight loss analysis showed that for Mui and Taru basin coal, devolatilization starts at 200°C and 250°C, and combustion was complete at 750°C and 650°C, respectively. The maximum temperature ...

Journal of Energy, 2021

Used tyres pose a threat to the environment, especially in developing countries, since the curren... more Used tyres pose a threat to the environment, especially in developing countries, since the current disposal methods lead to environmental pollution. Pyrolysis liquid from used tyres can be used as a source of fuel to replace petroleum diesel. Microwave pyrolysis is an alternative valorization process that is supposed to save energy and, therefore, is environment friendly. In the current study, microwave pyrolysis was used to produce liquid fuel. Processing variable levels for microwave were power levels of 20, 30, 40, 50, 60, 80, and 100%; the reaction times were 8, 13, 18, 23, and 28 minutes; and the particle sizes were 25, 50, 100, and 200 mm2. Design-Expert 13 was used for data analysis and optimization, and GC-MS was used for chemical composition analysis, while physiochemical properties were tested using standard methods. Response surface methodology (RSM) was used to study the effects of operating variables and identify the points of optimal yields. For microwave pyrolysis, th...

Cogent Engineering, 2020

While much research has been published on the Compost Heat Recovery Systems (CHRs), little has be... more While much research has been published on the Compost Heat Recovery Systems (CHRs), little has been documented on the design and performance evaluation of the Hydronic compost heat exchangers using numerical and computational methods, occasionally resulting in compost process inhibition. A CHRs (0.036 m3/7.2 m2) Hydronic-type heat exchanger and 12.43 m2/2.83 m3, compost reactor (CR), was designed and developed with the main objective of evaluating the design and its performance. The numerical design and performance evaluation was achieved by using Kern’s and the effectiveness and Number of Transfer Units methods (ε-NTU), respectively. Empirically, data were captured by using the Polytetrafluoroethylene (PTFE) thermocouples connected to the TC-8 Picolog Data loggers. Data validation (empirical and mathematical), was achieved by modifying a free computer-based software developed by the Chemical Engineering Calculations (CHECAL), into a Hydronic Compost Heat Exchanger design and perfor...

Research Journal of Applied Sciences, Engineering and Technology, 2014

Environmental pollution associated with petroleum sources of energy has reinvigorated interest in... more Environmental pollution associated with petroleum sources of energy has reinvigorated interest in the need to find "greener" electrical energy alternatives without a net carbon emission into the ecosystem to solve these problems. This research study analyzed electricity generation through bioelectrolytic reaction from an irish-potato, pineapple and tomato as electrolyte for the vegetative batteries with Zn/Cu as electrode. Treatments were performed on samples. In the first treatment, vegetative samples were heated at varied temperatures (19.5-80°C) and at varied holding times (20-60 min). In the second type, sample tissues were sandwiched between two aluminium plates through which pulses of ac current were passed at varied frequencies (2.63-100,000 Hz) maintained at 312 mV. With 108 cm 3 of sample, the battery capacities in untreated state were: irish-potato 53.7 mAh, pineapple 84.2 mAh and tomato 80.4 mAh; heat treated state: irish-potato 66.86 mAh, pineapple 116.4 mAh and tomato 108.8 mAh; while in electro orated state: irish-potato 68.9 mAh, pineapple 96.0 mAh and tomato 105.67 mAh. All these capacities were found experimentally to power a LED of forward current 1.44 mA, resistance of 270 Ω and supply voltage of 3V. Primary cost analyses showed that electro orated Zn/Cu vegetative battery samples generates portable energy of 5.74-50.54 cts/Wh, which is 14-124 times more than the currently available dry cell (D-type) cells retailed at 7.14 Ksh/Wh. Given that irish-potato is ranked fourth (after maize, wheat and rice) in the world and the second most important food crop after maize in Kenya in terms of abundance, it was recommended as an alternative vegetative battery.

Renewable Energy, 2001

Combustion mechanisms of two types of coffee husks have been studied using single particle combus... more Combustion mechanisms of two types of coffee husks have been studied using single particle combustion techniques as well as combustion in a pilot-scale fluidised bed facility (FBC), 150 mm in diameter and 9 m high. Through measurements of weight-loss and particle temperatures, the processes of drying, devolatilisation and combustion of coffee husks were studied. Axial temperature profiles in the FBC

Fuel, 2007

This study examines the effect of the chemical composition and origin on the performance of two c... more This study examines the effect of the chemical composition and origin on the performance of two calcitic and two dolomitic limestones from different sources in South Africa. The experiments were carried out in a fixed bed reactor maintained at 80° C. The raw sorbent ...