The effect of particle size on the pollution reduction potential of a South African coal-derived low-smoke fuel

Abstract

The coal combustion in cast-iron stoves leads to health hazards and air pollution. In this study the CO, SO2, NOx, PM and VOC emission concentrations were measured whilst combusting four fuel particle sizes (15, 20, 30, and 40 mm) as well as a composite of the sizes (all pre-devolatilized at a temperature of 550 °C) in a cast-iron stove. The results were compared to their raw coal analogues to evaluate the emission performance of each fuel type. Emission factors for NOx and SO2 were found to depend on the fuel nitrogen and sulphur contents in the coal and the combustion conditions used during pyrolysis. The PM, SO2 and VOC emissions show a strong dependence on the ash percentage and volatile matter yields, which both increased with increasing particle size. In addition, the PM, SO2 and VOC missions were found to only depend on particle size on a mechanistic level. The VOCs and PM emission factors are inversely correlated with particle size. The results from this study offer insight into the combustion environment in the Falkirk Union No 7 cast-iron stove as well as how this environment applies to low smoke fuels. The work contributes to the emission and performance inventories from South African domestic coal combustion in this stove used in informal settlements.