Effect of coal type on gasification in pressurized drop tube furnace

Abstract

In order to understand the effect of coal type on coal gasification process at 15 atmospheric pressure of pressurized drop tube furnace (PDTF), a numerical study was conducted. Eulerian approach is used for the gas phase, whereas Lagrangian approach is used for the solid phase. Turbulence is modelled using the standard k-epsilon model. The turbulent gas-phase combustion model incorporates the eddy dissipation model. One-step two-reaction model is employed for the devolatilization. Effect of coal type on carbon conversion at the same coal feed rate and gas flow rate cannot be verified due to the variation of equivalence ratio according to coal composition. Therefore, the same equivalence ratio is chosen to evaluate the effect of coal type on gasification. It is found that the volatile release based on experimental results should be taken in computations to predict accurate carbon conversion, especially in coal gasification due to the low gasification reaction. Even at over 1500 K and 15 atmospheric pressure, at which reactions are primarily diffusion-controlled the exit carbon conversion varies with the coal type. The temperature gradient in near-burner region becomes gentle with increasing proximate volatile and moisture contents, but the volatiles released can make the temperature gradient steep by means of the fast reaction with oxygen. Copyright (C) 2001 John Wiley & Sons, Ltd.