Sophisticated interplay of operating conditions governs flow field transition and optimal conversion inside tangentially fired gasifiers

Abstract

A computational model is developed to simulate reacting environment inside the pilot-scale, tangentially-fired, Mitsubishi Heavy Industry entrained-flow coal gasifier. Using this comprehensive model, the impact of three operating parameters, namely, swirl number (SN), reactor pressure and mass throughput on the gasifier flow field and coal gasification process is investigated. We demonstrate that for given values of any two of these parameters, it requires a threshold value of the third parameter to form the central recirculation zone (CRZ), the absence of which lowers char conversion. Therefore, a modified SN incorporating the combined effect of conventional SN, reactor pressure and mass throughput on the onset of CRZ formation is proposed for tangentially-fired gasifiers. Furthermore, the impact of variation in reactor pressure and mass throughput on char conversion is shown to be mediated through the corresponding change in particle residence time and pressure effect on kinetics. The results demonstrate that the operating parameters interact in a complex state space that governs the gasifier flow physics and optimal operation.