Polycyclic aromatic hydrocarbons (PAHs) and soot formations under different gasifying agents: Detailed chemical kinetic analysis of a two-stage entrained flow coal gasifier

Abstract

The injection of CO2 with coal into coal gasifier is a promising approach to achieve CO2 recirculation. Predicting the formation and evolution of polycyclic aromatic hydrocarbons (PAHs) and soot during coal gasification is particularly important as their presence poses challenges to the gasifier operation and environment. However, the effect of CO2 injection on their formation must be elucidated in more detail to optimize the gasifier design. This work investigates PAHs and soot formations in gas-phase reactions under different gasifying agents (Air, O2/CO2, O2/H2O) in a two-stage entrained flow coal gasifier using a detailed chemical kinetic model (DCKM). Under the O2/CO2– and O2/H2O-blown conditions, aromatics reforming was progressed whereas the yields of tar and soot were effectively suppressed. The benzene was observed as the most abundant PAHs species, followed by naphthalene and acenaphthalene. Regarding the relative oxygen concentration, the conversion behavior of aromatics was significantly influenced in the O2/CO2-blown condition, while the somewhat effect was found in the O2/H2O-blown condition. Tar yield peaked at 50% relative oxygen concentration in the O2/CO2-blown condition. The present finding may have practical significance in the O2/CO2-blown gasifier to facilitate CO2 recirculation for the oxy-fuel IGCC system.