The effect of Ca on distribution of nitrogen species during coal pyrolysis in N2, CO2 and Ar atmospheres

Nitrogen species distribution during coal pyrolysis with Ca addition in N 2 , CO 2 and Ar was studied at 1000 °C using a horizontal tube furnace. In particular, the effect of Ca on the distribution of nitrogen species in N 2 and CO 2 atmospheres, which were closer to pyrolysis processes of conversional air and oxy-fuel combustion in comparison with inert Ar environment, was investigated for the first time in this work. It was found that Ca has a great effect on nitrogen species distribution during both coal and demineralized coal pyrolysis; on the other hand, CO 2 causes the formation of NO. Demineralization increases the formation of HCN and char nitrogen, but there is little effect on NH 3 formation during pyrolysis in N 2 , in contrast to pyrolysis in Ar atmosphere, which decreases NH 3 formation. A significant reduction in char yield was found after char gasification in CO 2 at 1000 °C. With two different Ca-based additives, i.e., (CH 3 COO) 2 Ca and Ca(OH) 2 , char yield decreases with the increasing amount of Ca additives in both cases. The effect of Ca on HCN and NH 3 formation during pyrolysis depends on both the form of Ca and the amount of addition. In most cases, HCN and NH 3 formation decreases with Ca addition in Ar, but increases in N 2 . Ca addition slightly promotes HCN formation during pyrolysis in CO 2 . There is no NH 3 detected during pyrolysis in CO 2 because of the reaction of NH 3 and CO 2 in the background. In addition, NO concentration decreases sharply with increasing the amount of Ca addition in the atmosphere of CO 2 , which means that Ca has an effect not only on pyrolysis, but also on gasification of char in CO 2 . In most cases, char nitrogen increases with Ca addition in N 2 or Ar. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.