Browsing by Author "Ntalikwa, J.W."

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    Gas chromatographic determination of glycerol and triglycerides in biodiesel from jatropha and castor vegetable oils
    (Trans Tech Publications Ltd., 2013) Okullo, Apita, Aldo; 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.
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    Optimization of biodiesel production from jatropha oil
    (Trans Tech Publications Ltd., 2010) Okullo, Aldo; Temu, A.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 oC, 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 – 60oC), stirring rate (300 -900 rpm), and molar ratio (3 – 9 mol/mol) studied.
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    Pulping sisal fibres: effects of chemical concentration, na2so3/na2co3 ratio and fiber to chemical ratio
    (University of Dar es Salaam, 1994) Katima, J.H.Y.; Halfani, M.R.; Ntalikwa, J.W.
    This paper reports on pulping of hard fibres extracted from the leaves of agave sisalana using sodium sulphite buffered with sodium carbonate as pulping chemical. The cooking was carried out at I68C for a cooking period of 6 hours, with varying chemical concentration, sodium sulphite to sodium carbonate ratio and fibre to chemical ratio. The results show that both the pulp yield and pulp viscovity decrease with increasing chemical concentration, whereas Kappa number of pulp decreases to a limit of about 16.45. Brightness increases significantly with an increase in the ratio of Na3SO/Na2CO3. The pulp yield obtained indicated the following maximum strength indices: tensile index: 75.60/Nm/gJ, burst index: 6.05/kPa. m2/g/and tear index: 19.30/Nm2/kg). These values are higher than those reported for bleached pine kraft pulp; that is tensile index: 50.52/Nm/g), burst index: 5.77/kPam2/g/and tear index: 18.91/Nm2/kg) with a brightness of 81.0% ISO. These make sisal a promising candidate for non-wood pulping process.