Effect of mineral matter on emissions of SO₂ and NO_x during combustion of lean coal in O₂/CO₂ atmosphere

Combustion experiments of Changzhi coal at 550-1 000℃ were conducted in a tube furnace reactor in air and O₂/CO₂, respectively. The XRF, XRD etc. were employed to study the characteristics of raw coal and its demineralized coal. Effects of mineral matter in coal on combustion characteristics and release of SO₂ and NO_x during combustion were investigated using TG-DTG and Antaris-IGS. The results show that ignition and burnout temperature of the demineralized coal are lower than those of raw coal. In O₂/CO₂ the ignition and burnout temperature of raw coal and the demineralized coal are all higher. This shows that when oxygen concentration is 20%, the coals are easier to ignite and burnout in air. Besides that, SO₂ emission of the demineralized coal is higher than that of raw coal; while NO_x emission is opposite. For raw coal, SO₂ emission is higher when combusted in O₂/CO₂; while for the demineralized coal, it is opposite. During combustion in O₂/CO₂, NO_x emission is always lower whether for the raw or the demineralized coal.