Formation of NH 3 and HCN in slow-heating-rate inert pyrolysis of peat, coal and bark

Abstract

In gasification processes, nitrogen compounds are formed in the gas. There are very few data available on the conversion of fuel nitrogen to nitrogen compounds in pyrolysis conditions that simulate fixed-bed or fluidized-bed gasification or other fuels than coal. In this study, relatively large fuel pieces of peats, bark and coal were pyrolysed in an inert gas atmosphere at a slow heating rate. All fuels produced more NH 3 than HCN. The conversion of fuel nitrogen to NH 3 ranged from 17 to 24 wt% for peat, 10 to 12 wt% for bark and 15 to 17 wt% for coal. The conversion of fuel nitrogen to HCN was 5–11 wt% for coals and considerably less for the other fuels. Increasing the tar cracking can increase the HCN conversion and NH 3 conversion in peat pyrolysis. The pyrolysis of fuel pieces seems to produce the NH 3 and HCN observed in the fixed-bed gasifiers.