Bio diesel production, utilisation and by-product processing

A major challenge mankind is facing in this century is the gradual and inescapable exhaustion of the earth's fossil energy resources. The combustion of those fossil energy materials lavishly used as heating or transportation fuel is one of the key factors responsible for global warming. One of the most readily applicable alternative energy resources is biodiesel, which is a potential substitute for petroleum-based diesel fuel. Biodiesel is made from renewable biomass mainly by alkali-catalysed transesterification of plant oils. Biodiesel offers a number of interesting and attractive beneficial properties compared to conventional petroleum-based diesel. Most importantly, the use of biodiesel maintains a balanced carbon dioxide cycle since it is based on renewable biological materials. Pure biodiesel or biodiesel mixed in any ratio with petroleum-based diesel can be used in conventional diesel engines with no or only marginal modifications, and it can be distributed using the existing infrastructure. A number of aspects of biodiesel production, by-product glycerol utilization and utilisation in a test diesel engine facility are examined in the work described here. The kinetics of biodiesel production by transesterification of plant oils with methanol are described with reference to a novel solubility model that took into account the phase behaviour of the reacting mixture. It was revealed that the formation of methyl esters during the course of reaction promotes the dissolution of the oil in the methanol phase. Using ternary phase diagrams (oil/methanol/methyl esters) a new kinetic model that accounts for product-facilitated oil dissolution was developed. The model described the experimentally obtained kinetics well and scope for further future improvements to the model were identified. The microbial conversion of by-product glycerol to alcohols could potentially reduce dependency on methanol and improve process economics by re-cycling what will increasingly become a waste product as biodiesel production gains greater prominence. Two species of bacteria, Pantoea agglomerans and Clostridium pasteuranium were used in a fully instrumented bioreactor to investigate conversion of glycerols to alcohols. Overall alcohol yields were promising and it is possible that optimising the fermentation conditions for P. agglomerans still further could result in still higher alcohol yields. Bio diesel fuels in pure form and blended with mineral diesel in this study were tested in a four cylinder direct injection engine, typically used in small diesel genset applications. Engine performance and emissions were recorded at five load conditions and at two different speeds. Results were obtained for measurements of emission and smoke at the different speed and load conditions for the different bio diesel fuels The findings show that there is an increase in the over all specific fuel consumption at higher blends of bio diesel, but emissions were reduced at all blends and oils used with the exception of NOx which increased. A simple combustion analysis was also performed where ignition delay, position and magnitude of peak cylinder pressure and heat release rate were examined to asses how the variation of chemical structure and blend percentage affects engine performance