Ammonia yield from gasification of biomass and coal in fluidized bed reactor

Gas from the gasification of coal and biomass can be used for combined production of heat and power or for the synthesis of alternative fuels. In both cases, ammonia, which is created by the conversion of fuel-bound nitrogen, can cause technological difficulties. Therefore, ammonia concentration in the produced gas has to be monitored, or, at least, estimated to take appropriate measures for its abatement. In this paper, we report in detail the analysis of ammonia content in the produced gas as well as results of several experiments of fluidized-bed gasification of Spanish coal, South African coal, Rheinish coal and woody biomass. We focused on the evaluation and comparison of ammonia yield based on the following variables: (1) different fuels, (2) the addition of dolomitic limestone into the fluidized bed and (3) the use of carbon dioxide instead of steam in the gasifying agent. The conversion rate of fuel nitrogen into gas was surprisingly high for the less-reactive coals and within presumed levels for Rheinish coal and biomass. The presence of dolomitic limestone in the fluidized bed substantially increased the conversion rate of fuel-nitrogen into ammonia. The use of different gasifying agents had an ambiguous effect on ammonia yield.