99/00799 Mathematical simulation of a two stage entrained flow coal gasifier

Abstract

A detailed simulation model was developed for a pressurized air blown entrained flow coal gasifier with recycle char. In the model, the coal devolatilization, volatile and char combustion, H{sub 2}O-char and CO{sub 2}-char gasification, and gas phase shift reaction were taken into account both in the combustor and in the reductor in accordance with the actual process. The combustor was assumed to be a well-stirred reactor with uniform gas composition (CO, CO{sub 2}, H{sub 2}, H{sub 2}O, N{sub 2}) and gas-particle temperature (the flame temperature). The gas concentration profiles in the reductor were predicted by considering the gas and particle temperature distribution, which were calculated by a two-dimensional heat transfer model and a Monte-Carlo radiation sub-model. The model was applied to simulate the performance characteristics of the two gasifiers (2t/d and 200t/d) so far tested in Japan. The effects of air/coal ratio, coal and air partition between combustor and reductor on the gasifier performance, such as the carbon conversion, the cold gas efficiency and heating value of the product gas, were predicted by the model. Good agreement was obtained between the predictions and the test measurements.