Ammonia present in the product gas from coal gasification may increase NOx emissions from IGCC systems. A fixed bed reactor was used to study the effect of calcined limestone (CaO) on NH3 decomposition and reaction of NH3 and NO. Reactions at temperatures to 900°C in helium and in gas compositions typical of air‐blown gasifiers were studied. Although CaO enhanced ammonia decomposition in helium, reaction in the gasification atmosphere resulted in the loss of this catalytic activity. Increasing the total pressure further reduced the rate of NH3 decomposition. CaO enhanced conversion of NO to NH3 in gasification atmospheres.

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Three coals were combusted in the Alberta Research Council laminar flow combustor in order to understand the changes in the physical structure that occur during pulverized coal combustion. A subbituminous (coal A), and both high-volatile (coal B) and low-volatile bituminous (coal C) coals were chosen to examine coals of different rank and reactivity.The subbituminous coal and the high-volatile bituminous coal were very reactive, with burnouts of 95% and 88% achieved under stable operating conditions. The low-volatile bituminous coal was relatively unreactive. It was not possible to achieve a stable flame with the burnout decreasing below 50% in less than 1 h. Direct comparison of the partially burnt samples from the three coals was difficult because of the different reactivities. The subbituminous and high-volatile bituminous coals burned so rapidly that it was not possible to collect samples below 70% burnout. Conversely, it was not possible to generate samples of low-volatile bituminous coal char at burnouts above 72%.The subbituminous coal showed a continuous decrease in particle size with burnout. The high-volatile bituminous coal showed a significant size decrease only before 70% burnout, whereas the low-volatile bituminous coal actually increased in size up to 60% burnout, followed by a slight decrease. Surface area analysis of the subbituminous coal indicated a large surface area contained in micropores. At high levels of burnout (above 90%), the surface area decreased. The same behavior was observed for the high-volatile bituminous coal. While the low-volatile bituminous coal also showed this large increase in surface area, the decrease occurred at about 50% burnout, much earlier than for the other coals.Results of mercury porosimetry tests on the partially burnt samples revealed a significant change in the pore volume for both the subbituminous and high-volatile bituminous coals, while no large changes were observed for the low-volatile bituminous sample. It was difficult to draw any conclusions from the porosimetry results due to the different panicle size of the chars and wide variance in the measurements.

A non‐steady boundary layer model is developed for numerical simulation of combustion and gasification of a single shrinking char particle. The model considers mass and energy conservation coupled with heterogeneous char reactions producing CO and homogeneous oxidation of CO to CO2 in the boundary layer surrounding the char particle. Mass conservation includes accumulation, molecular diffusion, Stefan flow and generation by chemical reaction. Energy conservation includes radiation transfer at the particle surface and heat accumulation within the particle. Simulation results predict experimentally measured conversion and temperature profiles of a burning Spherocarb particle in a laminar flow reactor. Effects of bulk oxygen concentration and particle size on the combustion process are addressed. Predicted particle temperature is significantly affected by boundary layer combustion of CO to CO2. With increasing particle size, char gasification to char combustion ratio increases, resulting in decreasing particle temperature and increasing peak boundary layer temperature.