Numerical study on the effects of homogeneous reactions on the composition distributions of syngas in radiant syngas cooler

Abstract

The radiant syngas cooler (RSC) is a crucial equipment for recovering the sensible heat of high-temperature syngas produced by coal gasification. Most of the previous studies on RSC focused on the flow field and heat transfer, ignoring the chemical reactions in RSC. In this work, a three-dimensional RSC model is established to investigate the effects of homogeneous reactions on the composition distributions of syngas in RSC. The simulation results show that the composition distributions of syngas are similar to the temperature distribution of RSC. From the inlet to the outlet of RSC, the mole fraction of CO decreases by 2.81%, and the mole fraction of H2, CO2 and CH4 increases by 3.44%, 8.08% and 182.09%, respectively. The relationship between temperature and the mole fraction of CH4 is concluded, which can be used as an indirect method to predict the temperature of RSC. The homogeneous reaction in RSC is dominated by water–gas shift reaction (WGSR). There are backward WGSR and forward methane-steam reforming reaction (MSR) in the inlet area, which is contrary to the situation in the outlet area. Moreover, the composition distributions of syngas present a polarized distribution under the influence of operating pressure or operating load, because the homogeneous reactions in the inlet and outlet area of RSC are affected by syngas velocity and temperature, respectively.