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.

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.

Abstract:The increasing concerns over diminishing fossil fuel supplies and rising oil prices, as well as adverse environmental and human health impacts from the use of such fuels have led to the need of finding alternative fuels that will reduce the dependency on fossil fuels. Biodiesel from plant and animal oils sources, has been identified as such an alternative fuel. However, the major obstacle in the production and commercialization of biodiesel is the production cost. This high cost is mainly attributed to the cost of using edible vegetable oil as feedstock. There is a need to obtain biodiesel without compromising food security. In this paper, an alkali catalyzed continuous transesterification process with a capacity of 8000 tonnes/year of biodiesel from jatropha curcas seed oil was designed and simulated in HYSYS. Laboratory data was used for the simulation and the process was able to produce biodiesel of high purity (over 99.65%) and by-product glycerine with the purity grade of 95.3%.

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 (R 2 ) of 0.999.

The rising cost of energy and environmental concerns have led the brewing industry to search for techniques of reducing energy consumption in brewery operations. In this paper, pinch analysis was applied to a typical Ugandan based brewery process to target for the energy requirements of the process. Hint software was used for the analysis. At the chosen ΔTmin of 10˚C, the minimum cooling and heating utility requirements of the brewery studied were determined as being 4862.21 kW and 8294.21 kW respectively, with a pinch temperature at 68˚C. It was observed that using the technique, 1806.59 kW of energy could be recovered through process to process heat exchange which presented an energy saving potential of 21.5%. It is recommended that results from this study could be used in the design or retrofit of a heat exchanger network of a brewery for improved energy efficiency. Considerations can also be made for other values of ΔTmin.