Behaviour of nitrogen compounds and tars in fluidized bed air gasification of peat

Abstract

Formation of nitrogen compounds and tars, and the effect of process parameters on these were studied in a laboratory scale fluidized bed air gasifier under atmospheric pressure, using peat as fuel. Benzene was the main component of the tars, representing 50–75 wt% of the total tar. Addition of both secondary air and dolomite reduced the tar content of the gas. NH 3 concentration ranged from 3170 to 4600 ppm and HCN concentration from 520 to 930 ppm in the measurements. With no secondary air, 30% of fuel nitrogen formed NH 3 and 10% formed HCN. A rise in the freeboard temperature, caused by the addition of secondary air, had no significant effect on the concentration of nitrogen compounds. On the other hand, the presence of dolomite increased the NH 3 concentration and reduced the HCN concentration of the gas.