REACTIVE FLOW MODELLING OF COAL GASIFICATION INCLUDING TAR FORMATION AND CRACKING

Coal gasification faces persistent challenges from tar formation, which reduces conversion efficiency and causes operational issues. This study employs computational fluid dynamics (CFD) to investigate tar decomposition during coal gasification, focusing on the effects of equivalence ratio (ER), tar oxidation and steam reforming reaction. The model integrates a comprehensive reaction network including volatile decomposition, tar cracking, and steam reforming pathways. Simulations were conducted across ER values (0.16-0.40) at 1897 K using a validated three-stage entrained flow gasifier model. Key findings demonstrate that increasing ER from 0.16 to 0.40 significantly enhances tar decomposition, with optimal performance achieved between 0.33-0.40. At ER=0.33, the model predicts peak gasification efficiency (33.4%) with maximum H₂ and CO yields. Steam reforming facilitates tar cracking through the reaction C_0.88H_1.47O_0.12 + 0.778H_2O → 0.731H₂ + 0.882CO, while controlled oxidation (ER>0.33) promotes complete tar conversion to syngas. Temperature distribution analysis reveals that higher ER values create more uniform thermal fields, enhancing overall tar decomposition efficiency. This work provides quantitative insights for optimizing gasifier operation, demonstrating that precise ER control between 0.33-0.40 maximizes syngas quality while minimizing tar formation. The validated CFD framework offers a robust tool for predicting and improving gasification performance.