Research Repository :: Browsing by Author "Temu, Abraham K."

Browsing by Author "Temu, Abraham K."

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Development and Testing of a Probe to Monitor Gas-Side Fouling in Cross Flow
(Taylor & Francis, 2002-05) Temu, Abraham K.; Næss, Erling; Sønju, O. K.
A probe to monitor gas-side fouling in cross flow has been developed and tested in laboratory experiments. The probe is suitable for monitoring both the heat flux and the mass accumulated on the front and rear side of a cylinder in cross flow. A procedure for converting the mass accumulation measurements to thermal resistance is developed. Experimental results obtained using the mass accumulation method are compared to data obtained by heat flux measurements, and show good agreement in terms of the thermal fouling factor. It is also shown that the test results are in good agreement with other experimental results found in the literature. The probe is well suited for distinguishing the thermal effect (thermophoresis) from the other forces contributing to fouling. It is also useful for nonfouling heat transfer studies, providing average heat transfer coefficients on the front and rear sides of a cylinder.
Experimental Investigations of Fuel Properties of Biodiesel Derived from Tylosema Esculentum Kernel Oil
(Taylor & Francis, 2013) Gandure, Jerekias; Ketlogetswe, Clever; Temu, Abraham K.
The alternative fuels debate continues to attract the attention of researchers and scientists globally. This paper reports experimental results on selected properties of biodiesel derived from Tylosema Esculentum kernel oil and compares them with similar properties of petroleum diesel to assess its suitability for use as fuel in diesel engines. Results indicate an ester content of 90% for tylosema biodiesel fuel, while its viscosity profile meets requirements of American standards for biodiesel fuel (ASTM D 6751-02). The flash point and cold flow properties of tylosema biodiesel were found to be typical of a biodiesel fuel, while its acidity is within range of both American and European standards by 72.5%, and 56% respectively. It was also observed that biodiesel engine performance is marginally better than that of petroleum diesel, with lower concentrations of hydrocarbon emissions. Levels of carbon dioxide and carbon monoxide (CO) are largely comparable to those of petroleum diesel.
Fuel properties of biodiesel produced from selected plant kernel oils indigenous to Botswana: A comparative analysis
(Elsevier, 2014) Gandure, Jerekias; Ketlogetswe, Clever; Temu, Abraham K.
Fuel characteristics of biodiesel derived from kernel oils of Sclerocarya birrea, Tylosema esculentum, Schiziophyton rautanenii and Jatropha curcas plants were investigated in comparison with petroleum diesel. The fuel properties under review include flash point, cloud point, kinematic viscosity, density, calorific value, acid value, and free fatty acids. These were determined and discussed in light of major biodiesel standards such as ASTM D 6751 (American Society for Testing and Materials) and EN 14214 (European standards). The best biofuel in terms of cold flow properties was S. rautanenii, with a cloud point of 0°C and a pour point of -5°C. The good cold flow properties demonstrate operational viability during the cold season. The heating values of S. birrea and S. rautanenii biodiesel fuels were found to be 9.2% and 10.3% lower than that of petroleum diesel while those of T. esculentum and J. curcas were both 9.7% lower. Other fuel properties analysed demonstrate that biodiesel fuels produced from kernel oils of S. birrea, T. esculentum, S. rautanenii and J. curcas plants have properties that are comparable to, and in some cases better than, those of petroleum diesel. The results of this study indicate the feasibility of producing quality biodiesel fuel from indigenous seed oils found in Botswana. A balanced allocation of resources however needs to be established to ensure that the cultivation of these oil-bearing plants does not compete with the cultivation of food crops.
Gas Chromatographic Determination of Glycerol and Triglycerides in Biodiesel from Jatropha and Castor Vegetable Oils
(Trans Tech Publications, Switzerland, 2013) Apita, Aldo Okullo; Ogwok, P.; Temu, Abraham K.; Ntalikwa, J.W.
Monoacylglycerols and diacylglycerols are intermediate compounds in biodiesel which result from incomplete transesterification reaction during biodiesel production. Traces of free glycerine and partially reacted triacylglycerols are also found in biodiesel. These contaminants cause serious operational problems in engines, such as engine deposits, filter plugging, and emissions of hazardous gasses. Increased levels of these contaminants in biodiesel compromise quality which is vital for commercialisation of this product. In this work, levels of free glycerine and total glycerine in jatropha methyl ester (JME) and castor methyl ester (CME) were determined using gas chromatography (GC) equipment. Amounts of free and total glycerine in JME and CME were generally high compared to the ASTM D6751 and EN14214 recommended values. Free glycerine from JME was 0.1% wt compared to 0.02% wt (ASTM D6751) and 0.01% wt (EN14214) values whereas the total glycerine from JME was 2.96% wt compared to 0.24 %wt (ASTM D6751) and 0.21% wt (EN14214). These discrepancies could have resulted from insufficient purification of the product and incomplete conversion or due to the high temperature associated with GC analysis that might have caused pyrolysis or thermal degradation of certain lipid components. Castor methyl ester free glycerine was 0.14% wt while total glycerine was 13.21% wt. This can still be explained by the same reasons given for JME. Thermal decomposition of lipid components in a GC could have interfered with the summative mass closure calculations that were done to determine the total composition of the biomass.
Gas Chromatographic Determination of Glycerol and Triglycerides in Biodiesel from Jatropha and Castor Vegetable Oils
(Trans Tech Publications, Switzerland, 2013) Apita, Aldo Okullo; Ogwok, P.; Temu, Abraham K.; Ntalikwa, J.W.
Monoacylglycerols and diacylglycerols are intermediate compounds in biodiesel which result from incomplete transesterification reaction during biodiesel production. Traces of free glycerine and partially reacted triacylglycerols are also found in biodiesel. These contaminants cause serious operational problems in engines, such as engine deposits, filter plugging, and emissions of hazardous gasses. Increased levels of these contaminants in biodiesel compromise quality which is vital for commercialisation of this product. In this work, levels of free glycerine and total glycerine in jatropha methyl ester (JME) and castor methyl ester (CME) were determined using gas chromatography (GC) equipment. Amounts of free and total glycerine in JME and CME were generally high compared to the ASTM D6751 and EN14214 recommended values. Free glycerine from JME was 0.1% wt compared to 0.02% wt (ASTM D6751) and 0.01% wt (EN14214) values whereas the total glycerine from JME was 2.96% wt compared to 0.24 %wt (ASTM D6751) and 0.21% wt (EN14214). These discrepancies could have resulted from insufficient purification of the product and incomplete conversion or due to the high temperature associated with GC analysis that might have caused pyrolysis or thermal degradation of certain lipid components. Castor methyl ester free glycerine was 0.14% wt while total glycerine was 13.21% wt. This can still be explained by the same reasons given for JME. Thermal decomposition of lipid components in a GC could have interfered with the summative mass closure calculations that were done to determine the total composition of the biomass.
High Free Fatty Acid (FFA) Feedstock Pre-Treatment Method for Biodiesel Production
(Trans Tech Publications, Switzerland, 2011) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan; Mrema, Godwill D.
Biodiesel is an alternative fuel for engine and other appliances that is obtained by transesterifying vegetable oils or other materials largely comprised of triacylglycerols with monohydric alcohols to give the corresponding mono-alkyl esters. The quality of feedstocks for the biodiesel production dictates the method of its production and quality. Based on the initial amount of minor components in feedstocks, a process comparison of acid pre-treatment and caustic pretreatment of feedstock for alkali transesterification was done. Acid pre-treatment was carried out with 0.60 w/w methanol-to-oil ratios in the presence of 2% w/w H 2 SO 4 as an acid catalyst in 2 h reaction at 60 °C. In caustic pretreatment process, the same amount of oil was neutralized with the required amount of sodium hydroxide based on the initial amount of free fatty acid and gums in the oil. The acid pretreatment process gives a 4% loss in feedstock compared to 20% from the neutralization process. The yields 96% and 94% of biodiesel from acid pretreated and caustic pretreatment feedstock were obtained respectively. The oxidation stabilities of biodiesel from acid pretreatment and neutralized feedstock were 1.12h and 3h respectively. The biodiesel from acid pretreatment oil could not pass the ASTM standard.
Investigating Schiziophyton Rautanenii Biodiesel as Fuel for the Diesel Engine
(2014) Gandure, Jerekias; Ketlogetswe, Clever; Temu, Abraham K.
The search for plant kernel oils for use as potential substrates for production of biodiesel continues to draw global attention. In the current paper, the performance and emission characteristics of biodiesel derived fromschiziophyton rautaneniikernel oil were investigated in a diesel engine. The parameters investigated are brake thermal efficiency, engine torque, brake power, specific fuel consumption, hydrocarbons, carbon dioxide, carbon monoxide, oxygen and soot production. The results indicate that Schiziophyton rautanenii biodiesel used in this study was comparable to petroleum diesel in terms of performance and emission characteristics, and is recommended for use in diesel engines.
Investigation of the Parameters Affecting Castor Oil Transesterification Reaction Kinetics for Biodiesel Production
(International Journal of Scientific & Engineering Research, 2013-03) Apita, Aldo Okullo; Temu, Abraham K.
Kinetic studies are concerned with the quantitative description of how fast chemical reactions take place and factors affect-ing them. The study is important to a chemist to understand the fundamental aspects of the reaction pathways to achieve the desired product. It enables us to tailor a chemical reaction so as to produce the desired product in a controlled manner. Castor oil was trans-esterified with methanol using a molar ratio of methanol to oil (6:1) and sodium hydroxide catalyst (1% wt of oil). The product of the reaction is castor methyl ester (CME) and glycerol with diglyceride and monoglyceride as intermediate products. The experiment was set to determine the effect of temperature, stirring rate and residence time on the rate constants and a second order rate law was used. Four different temperatures (35, 45, 55 and 65C) and four stirring rates (600, 660, 700 and 800 rpm) were used and the reac-tions were timed. High temperatures (55 and 65C) were unfavourable for castor transesterification; both temperatures provided yields of 91%. Low temperatures (35 and 45C) increased rate constants and produced highest yields (98% and 97% respectively). Increas-ing stirring rate does not favour conversion rates. The optimum reaction time was 60 minutes. Beyond 90 minutes, the reverse reac-tion was favoured. The close fit of the data indicates that the selected model was adequate. These results agree well with reports from literature.
Lemongrass and Cinnamon Essential Oils as Vitamin C Preservative and Flavour Enhencer in Jam
(2014-06) Byarushengo, Denice; Minja, Rwaichi; Temu, Abraham K.
Low Temperature Glycerolysis as a High FFA Pre-Treatment Method for Biodiesel Production
(Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Lee, Keat Teong
A novel low temperature glycerolysis process for lowering free fatty acid (FFA) in crude jatropha oil for alkali catalyzed transesterification has been developed. The response surface methodology (RSM) based on central composite design was used to model and optimize the glycerolysis efficiency under three reaction variables namely; reaction time, temperature and glycerol to oil mass ratio. The optimum conditions for highest glycerolysis efficiency of 98.67% were found to be temperature of 65℃, reaction time of 73 minutes and 2.24 g/g glycerol to oil mass ratio. These conditions lower the high free fatty acid of crude jatropha oil from 4.54% to 0.0654% which is below 3% recommended for alkali catalyzed transesterification. The pre-treated crude jatropha oil was then transesterified by using homogeneous base transesterification resulting to a conversion of 97.87%. The fuel properties of jatropha biodiesel obtained were found to be comparable to those of ASTM D6751 and EN 14214 standards. The process can also utilize the crude glycerol from the transesterification reaction, hence lowering the cost of biodiesel. The glycerolysis is easier implemented than acid esterification thereby avoiding the need for neutralization and alcohol removal step.
Major Observations, Lessons and Recommendations
(2004) Mwamila, Burton; Diyamett, Bitrina; Temu, Abraham K.; Trojer, Lena; Bångens, Lennart
Modelling the Kinetics of Jatropha Oil Transesterification
(Scientific Research, 2015-01) Apita, Aldo Okullo; Temu, Abraham K.
Kinetics of a chemical reaction provides an important means of determining the extent of the reaction and in reactor designs. Transesterification of jatropha oil with methanol and sodium hydroxide as a catalyst was conducted in a well mixed reactor at different agitation speeds between 600 and 800 rpm and temperature range between 35°C and 65°C. The effect of variation of temperature and mixing intensity on rate constants were studied. The initial mass transfer controlled stage was considered negligible using the above impeller speeds and second order mechanism was considered for the chemically controlled kinetic stage. Samples were collected from the reaction mixture at specified time intervals and quenched in a mixture of tetrahydrofuran (THF) and sulphuric acid. The mixture was centrifuged at 2000 rpm for 15 minutes and the methyl ester was separated from the glycerol. The ester was washed with warm water (50°C), dried and analysed using gas chromatography coupled with flame ionization detector (GC/FID) to determine free and total glycerine and methyl ester. A mathematical model was fitted using second order rate law. High temperature and high mixing intensity increased reaction rates. The model fitted well with a high correlation coefficient (R2) of 0.999.
Optimization of Biodiesel Production from Jatropha Oil
(Trans Tech Publications, Switzerland, 2010) Apita, Aldo Okullo; Temu, Abraham K.; Ntalikwa, J.W.; Ogwok, P.
The most important factors that influence biodiesel production are temperature, molar ratio, catalyst amount, time and degree of agitation. This study investigated the effects of temperature, molar ratio and degree of agitation and their interactions on the yield and purity of biodiesel produced from Jatropha oil. Factorial design and response surface methodology (RSM) were used to predict yield and purity of biodiesel as functions of the three variables. Interactions of all the factors were found to be significant on both yield and purity responses. Temperature and molar ratio main effects were found to be significant on the yield whereas only temperature main effect was significant on the purity of the biodiesel. The optimum conditions of operations were; temperature of 54 o C, molar ratio of methanol to oil of 6:1 and stirring speed of 660 rpm. Using these conditions, biodiesel yield of 95% (wt) was obtained with a purity of 97%. This model can be used to predict the yield and purity of biodiesel from jatropha oil within the ranges of temperature (30 – 60C), stirring rate (300 -900 rpm), and molar ratio (3 – 9 mol/mol) studied.
Performance and Emission Characteristics of Tylosema Esculentum Biodiesel in a Diesel Engine: An Experimental Investigation
(David Publishing, 2014) Gandure, Jerekias; Ketlogetswe, Clever; Temu, Abraham K.
Biodiesel derived from indigenous feed stocks such as Tylosema esculentum kernel oil is deemed a feasible alternative to petroleum diesel for the diesel engine. This paper presents results of investigation of performance and emissions characteristics of diesel engine using Tylosema biodiesel. In this investigation, Tylosema biodiesel was prepared, analyzed and compared with the performance of petroleum diesel fuel using a single cylinder compression ignition diesel engine. The specific fuel consumption, engine torque, engine brake power, hydrocarbons, carbon monoxide and carbon dioxide were analyzed. The tests showed a decrease in engine brake power and torque with increase in engine load, while specific fuel consumption showed an increasing trend with maximum variation of 33% between the two fuels at engine load of 90%. Emission levels of hydrocarbons, carbon monoxide and carbon dioxide showed an increasing trend with increase in load for both fuels. Tylosema biodiesel produced significantly lower concentrations of hydrocarbons than petroleum diesel, while levels of carbon dioxide and carbon monoxide were largely comparable to those of petroleum diesel. Soot production from combustion of Tylosema biodiesel was found to be approximately 98% lower than that from combustion of petroleum biodiesel, demonstrating insignificant contribution to environmental pollution
Physico-Chemical Properties of Biodiesel from Jatropha and Castor Oils
(International Journal of Scientific and Engineering Research, 2011-03-11) Apita, Aldo Okullo; Temu, Abraham K.; Ogwok, P.; Ntalikwa, J. W.
Biodiesel is becoming prominent among the alternatives to conventional petro-diesel due to economic, environmental and social factors. The quality of biodiesel is influenced by the nature of feedstock and the production processes employed. High amounts of free fatty acids (FFA) in the feedstock are known to be detrimental to the quality of biodiesel. In addition, oils with compounds containing hydroxyl groups possess high viscosity due to hydrogen bonding. American Standards and Testing Materials, (ASTM D 6751) recommends FFA content of not more than 0.5% in biodiesel and a viscosity of less than 6 mm2/s. The physico-chemical properties of jatropha and castor oils were assessed for their potential in biodiesel. The properties of jatropha and castor oils were compared with those of palm from literature while that of biodiesel were compared with petro-diesel, ASTM and European Standards (EN14214). Results showed that high amounts of FFA in oils produced low quality biodiesel while neutralized oils with low amounts of FFA produced high quality biodiesel. The quality of biodiesel from jatropha and castor oils was improved greatly by neutralising the crude oil
Pre-Treatment of High Free Fatty Acids Oils by Chemical Re-Esterification for Biodiesel Production—A Review
(Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Kansedo, Jibrail; Lee, Keat Teong
Non edible oil sources have the potential to lower the cost of biodiesel. However, they usually contain significant high amounts of free fatty acids (FFA) that make them inadequate for direct base catalyzed transesterification reaction (where the FFA content should be lower than 3%). The present work reviews chemical re-esterification as a possible method for the pre-treatment of high FFA feedstock for biodiesel production. The effects of temperature, amount of glycerol, type and amount of catalyst have been discussed. Chemical re-esterification lowers FFA to acceptable levels for transesterification at the same time utilizing the glycerol by product from the same process. Further researches have been proposed as a way forward to improve the process kinetics and optimization so as to make it more economical.

Browsing by Author "Temu, Abraham K."

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