[The effects of iron compounds on SO2 and NO emissions in coal combustion process]

The effects of ferric/ferrous chlorides and ferric oxide on emissions in Tongchuan coal combustion process were experimentally investigated using thermogravimetric analyzer. The results show that all iron compounds used in the experiments, namely FeCl3, FeCl2 and Fe2O3 can change the emissions of SO2 and NO, but with different mechanisms and different magnitudes. FeCl3 plays the roles of both a catalyst and an absorbent in the conversions from coal-S to SO2 and from coal-N to NO. Due to the catalysis the activation energy required for the formation of SO2 and NO is reduced, the rates of the reactions leading to SO2 and NO increased. The catalysis is concerned with the forms of coal sulfur. Due to the absorption FeCl3 reacts with SO2 to produce FeSO4 [symbol: see text] Fe2(SO4)3. In addition FeCl3 can decrease the emissions of CO, i.e., the combustion characteristics can be changed. The effects of FeCl2 on the emissions of SO2, NO and CO are similar to those of FeCl3, but weaker. Fe2O3 can also decrease the SO2 and NO emissions to some extent, but has negligible influence on CO emission.