Numerical simulation of radiant syngas cooler with different connection to entrained-flow gasifier

Abstract

The throat region of radiant syngas cooler (RSC) is a key part for connecting the entrained-flow gasifier with RSC, and an annular step is employed in the throat region of the connection to separate the molten slag from the high-temperature gasification products discharged from the gasifier. Multiphase flow and heat transfer in four types of connection designs (i.e., straight cylindrical connection (SCC), straight cylindrical connection with annular-step (SCCA), tapered connection with annular-step (TCA), and divergent connection with annular-step (DCA)) have been studied in this work. The radiation heat transfer is simulated by the discrete ordinates model (DOM). Comparing simulated values with industrial measured values, the reliability and accuracy of the mathematic models are validated with the maximum relative error of 3.7%. Simulation results show that a torch shape inject flow is formed at the top of the RSC, and the temperature of inject region is higher than that of nearby zone. Flow field distribution is changed by the annular step and tapered region, and thus results in twice dissipation of the central jet flow. The annular step can accelerate the dissipation of the turbulent flow, and the geometry of the throat region has a great influence on the size and intensity of the recirculation bubble. The tapered region of TCA makes the first recirculation more obvious than that of the DCA and SCCA, which causes that the recirculation regions have a tendency to coalescence. The jet dissipation position moves upwards due to the changes of connection structure, which is beneficial to enhance the heat exchange performance between the syngas and membrane wall. The changes of connection structure make the particle dispersion position move upward, but can alleviate the particle dispersion.