Numerical simulation of entrained flow coal gasifiers. Part II: effects of operating conditions on gasifier performance

Abstract

The comprehensive entrained flow coal gasification model developed in Part I was used for parametric studies to provide a better understanding of two-stage air blown entrained flow gasifiers. A series of numerical tests was performed for the 200 t/d pilot-scale gasifier under various operating conditions (heterogeneous reaction rate, coal type, particle size, and air/coal partitioning to the two stages). The coal conversion, product gas composition, calorific value and gas temperature profiles throughout the gasifier were simulated. The results show that coal devolatilization and char oxidation were responsible for most of the carbon conversion (up to 80%) in the two-stage air blown entrained flow gasifier. The predicted carbon conversion was independent of devolatilization rate, sensitive to the chemical kinetics of heterogeneous reactions on the char surface, and less sensitive to a change in coal particle diameter. It was found that the air ratio had a significant effect on gasifer performance with strong coal type dependence. The effect of air/coal partitioning to the two stages, and the feed rate of recycle char was found to be limited.