A numerical study on the effect of flow distribution on reactor performance

Abstract

A numerical study was conducted to analyse the effect of flow distribution of stirred part and plug flow part on combustion efficiency at the coal gasification process in an entrained bed coal reactor. The model of computation was based on gas-phase Eulerian balance equations of momentum and mass. The solid phase was described by Lagrangian equations of motion. The k–ϵ model was used to calculate the turbulence flow and the eddy dissipation model was used to describe the gas-phase reaction rate. The radiation was solved using a Monte-Carlo method. A one-step two parallel reaction model was employed for the devolatilization process of a high volatile bituminous Kideco coal. The computations agreed well with the experiments, but the flame front was closer to the burner than the measured one. The flow distribution of a stirred part and a plug flow part in a reactor was a function of the magnitude of recirculation zone resulting from the swirl. The combustion efficiency was enhanced with decreasing stirred part and the maximum value was found to be around S=1·2, having the minimum stirred part. The combustion efficiency resulted from not only the flow distribution but also from the particle residence time through the hot reaction zone of the stirred part, in particular for the weak swirl without IRZ (internal recirculation zone) and the long lifted flame. Copyright © 1999 John Wiley & Sons, Ltd.