The purpose of the thesis was to investigate if producing a slurry made from char particles could be used as a locally sourced alternative to diesel in developing countries for making electricity with engine generators. The lack of access to electricity in many areas of developing countries is seen as one of the biggest barriers to economic development.
The research investigated all aspects of char slurry fuels including sourcing suitable feedstocks, conversion to char, micronisation and combustion in an engine. A slurry fuel testing facility was built for the purpose encompassing a small diesel engine generator, typical of what is available in developing countries for producing electricity.
Analysis of a wide selection of chars made from several types of material showed that woody biomass was the most suitable for producing slurry fuels. The majority of chars made from agricultural residues were not suitable as the silicon content is likely to cause wear issues in engines. The grindability of chars made from biomass was good and the energy requirements to micronise to particle sizes suitable for an engine were small enough to make producing slurry fuels economically viable. It was recommended that low pyrolysis temperatures are used to make char for slurry fuels because they burn better in an engine whilst still having a high grindability.
Two 10%wt. char-diesel slurry fuels were tested, one using a pyrolysis char, the other using a hydrothermal carbonisation (HTC) char. It was found that the HTC char burned better, producing less CO, THC and soot than the pyrolysis char based fuel because the carbon was less recalcitrant. Issues were found with the engine when using slurry fuels, particularly the injector needle which would sieze. Investigating better injector design and engine construction materials is a priority to make slurry fuels viable for developing countries.
