AUSTRALIAN BROWN COAL/OIL MIXTURES AS A FUEL FOR DIESEL ENGINES; ENGINE PERFORMANCE AND ECONOMIC VIABILITY

ABSTRACT

CSIRO Division of Energy Technology has used mixtures of finely ground, chemically beneficiated, Australian brown coal (up to 30% by weight, maximum particle size less than 13 microns) and automotive diesel oil (ADO) to fuel an essentially unmodified single cylinder diesel engine operating at 800, 1200 and 1500 r/min. Engine performance tests indicate that brown coal can be used as a fuel extender to reduce consumption of the conventional liquid diesel fuel (ADO). Partially burnt coal agglomerates were identified in the engine exhaust and there were indications of late burning at the higher engine speeds and coal concentrations. Engine brake thermal efficiency ratio is identified as an important parameter when evaluating the thermal performance and economic viability of new fuels for internal combustion engines. A simple economic model based on ‘payback period’ is developed and used to assess the viability of converting an existing diesel engine powered plant to operate on the coal/oil mixture fuels (COM). The simple economic analysis technique can also be applied to other fuel formulations and fuel extenders. Conversion of large, slow speed stationary diesel engines to operate on brown COM fuels is shown to be uneconomical, given a projected brown coal cost of 215 $A/t (including processing).