Effect of demineralization and catalyst addition on N2 formation during coal pyrolysis and on char gasification

Six coals with different ranks and different ash contents have been used to study the effect of demineralization on N-2 formation during coal pyrolysis. Chars obtained after pyrolysis have been also gasified with carbon dioxide at 1000 degreesC to investigate the influence of the demineralization on char gasification reactivity. The pyrolysis results show that the demineralization by acid washing drastically changes N-2 formation profiles and decreases nitrogen conversion to N-2 for low rank coals; on the other hand, the demineralization has little effect on N-2 formation for high rank coals. Addition of 0.5 wt% Fe promotes N-2 formation from the demineralized coals, but the catalytic effect depends on the coal type. It is found that the Fe remarkably promotes N-2 formation from the demineralized low rank coals, but the effect is much smaller for high rank demineralized coals. These observations suggest that the existing state of Fe-containing minerals and added Fe catalyst is important for catalytic N-2 formation during coal pyrolysis. Gasification results show that the demineralization lowers char gasification reactivity not only for low rank coals but also for high rank coals. (C) 2003 Elsevier Ltd. All rights reserved.