NUMERICAL SIMULATION OF GASIFICATION PROCESS

Numerical simulation of the oxygen-blown coal gasification process inside a cross-type two-stage (E-Gas like) gasifier is studied with the commercial CFD solver ANSYS FLUENT. The purpose of this study is to use CFD simulation to improve understanding of the gasification processes in the E-Gas like gasifier. In this paper, chemical reaction time is assumed to be faster than the time scale of the turbulence eddies. All the species are assumed to mix in the intermolecular level. The 3-D Navier-Stokes equations and species transport equations are solved with the eddy-breakup reaction model (instantaneous gasification). The influences of coal slurry concentration and O2/coal ratio on the gasification process are investigated. Under the condition of feeding carbon being almost completely converted, low slurry concentration is preferred over high concentration if more H2 is wanted with lower syngas temperature; while higher slurry concentration is preferable for producing more CO with higher syngas temperature. The case of higher O2/Coal ratio results in more combustion and leads to lower syngas heating values and higher temperatures. Meanwhile, lower O2/Coal ratio involves more gasification reactions and results in higher CO concentration and lower temperature. The flow behavior in the gasifier, especially the single fuel injection design on the second stage, is examined and discussed. In summary, the trends of simulated results of coal combustion and gasification processes in the cross-type two-stage gasifier are reasonable and the developed simulation model in this study can be used as a tool for preliminary examination of the global effect of thermal-flow and turbulence on gasification process. Key words: clean coal technology, gasification modeling, integrated gasification combined cycle (IGCC)