Impacts of fuel feeding methods on the thermal and emission performance of modern coal burning stoves

Abstract

The extensive use of traditional cooking and heating stoves to meet domestic requirements creates a serious problem of indoor and outdoor air pollution. This study reports the impacts of two fuel feeding methods - front-loading and top-loading on the thermal and emissions performance of a modern coal-fired water-heating and cooking stove using a contextual test sequence that replicates typical patterns of domestic use. Known as a low-pressure boiler, when this stove was fueled with raw coal, the findings indicate that front-loading the fuel, which devolatilizes the new fuel gradually, produced consistently higher space heating efficiency and lower emission factors than top-loading the same stove, which devolatilizes new fuel all at once. Comparing the performance at both high and low power gave the similar results: Front-loading with raw coal produced consistently better results than top-loading. The average water heating efficiency when front-loading was (58.6±2.3)% and (53.4±1.8)% for top-loading. Over the sixteen-hour test sequence, front-loading produced 22% lower emissions of PM2.5 (3.9±0.6) mg/MJNET than top-loading (4.7±0.9) mg/MJNET. The same pattern was observed for carbon monoxide and the CO/CO2 ratio. CO was reduced from (5.0±0.4) g/MJNET to (4.1±0.5) g/MJNET. The combustion efficiency (CO/CO2 ratio) improved from (8.2±0.8)% to (6.6±0.6)%. Briquetted semi-coked coal briquettes are promoted as a raw coal substitute, and the tests were replicated using this fuel. Again, the same pattern of improved performance was observed. Front loading produced 3.5% higher heating efficiency, 10% lower CO and a 0.9% lower CO/CO2 ratio. It is concluded that, compared with top loading, the manufacturers recommended front-loading refueling behavior delivered better thermal, emissions and combustion performance under all test conditions with those two fuels