E208 PREDICTION OF INFLUENCE OF OPERATING CONDITIONS ON GASIFICATION PERFORMANCE OF ENTRAINED FLOW AIR BLOWN COAL GASIFIER

Abstract

Deeply understanding of phenomena in a coal gasifier is very useful for an assessment gasifier performance and for an optimization of a design and operation parameters. In this paper, influence of operating conditions, such as oxygen concentration in oxygen enriched air as a gasifying agent and steam flow rate, on gasification performance of an entrained flow air blown coal gasifier is discussed. A numerical simulation, three-dimensional gas-particles reacting flow calculations were carried out to predict gasification performance of the gasifier. As a target of this simulation, the 2 tons/day (T/D) coal gasifier of CRIEPI was selected. The gas phase properties are calculated by three dimensional time-mean Eulerian conservation equations. The turbulent flow field is determined by the κ-ε two equations model. Radiative energy transfer is calculated by the discrete transfer radiation model. The pulverized coal and ash particle behavior is modeled via a Lagrangian manner. Coal gasification reaction model is constited by three chemical processes in the current model; a pyrolysis, a char gasification and gas phase reactions. Per pass gasification performance were only taken into account in the calculation (without unburnt char recycle system). The model result of the per pass carbon conversion efficiency increases as the oxygen concentration in gasifying agent increases. The per pass carbon conversion efficiency hardly changes even if the steam flow rate increases in the same oxygen concentration condition. The current model is potentially powerful tool for the evaluation of gasification performance.