COAL-GASIFICATION AND COMBUSTION OF LCV GAS

Experiments were performed on the gasification of bituminous coal with air and steam in a 2.5 kW atmospheric fluidized bed. Thermal conversi on efficiencies, the retention of sulphur and the conversion of fuel n itrogen to NH3 were determined fbr various oxygen-to-carbon ratios (eq uivalence ratios between 0.58 and 0.82), with and without limestone in the bed. The conversion efficiency increased with increasing equivale nce ratio, while the conversion of fuel-nitrogen to NH3 decreased with increasing equivalence ratio. The sulphur conversion without the addi tion of limestone increased with increasing equivalence ratio. As expe cted, the presence of limestone in the bed led to increased sulphur re tention, more so at the high and low ends than at intermediate values of the range Of equivalence ratios. In addition, limestone adversely a ffected thermal conversion efficiency and increased the conversion of fuel-nitrogen. The low calorific value (LCV) fuel gas, produced by the AFBG, was combusted in a cyclone combustor at atmospheric pressure. S table combustion of the LCV fuel gas was possible down to a calorific value of 1.57 MJ/m(n)(3). The combustion efficiency in the atmospheric topping combustor varied between 98.72 and 99.96%. Nearly 60% of the NH3 in the fuel gas was converted to NO in the combustor (C) 1998 Else vier Science Ltd. All rights reserved.