2-06　Numerical simulation of polycyclic aromatic hydrocarbons and soot formations from coal volatiles in a Two-stage Entrained Flow Gasifier with detailed chemistry

Abstract

CO₂ recirculation in the oxy-fuel Integrated Coal Gasification Combined Cycle (IGCC) system is essential for continuous use of coal in the future. This study presents a detailed kinetic investigation into coal gasification under O₂-N₂ and oxy-fuel (O₂-H₂O, O₂-CO₂) gasifying agents. The effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation in the reductor of a two-stage entrained flow gasifier were simulated using CHEMKIN. The detailed chemical kinetic model includes 202 species, 1,351 gas-phase reactions, and 101 surface reactions. The numerical results showed that the oxy-fuel blown modes promoted tar reforming to complete elimination at 1,200°C (<1.5mg/Nm^₃). Because of a different tar conversion behavior, the O₂-H₂O blown mode provided a more potent tar-yield inhibition. In the case of soot formation, the amount of soot decreased under oxy-fuel blown modes. This behavior resulted from hydrogen abstraction and C₂H₂ addition (HACA) surface growth, and nucleation rate reductions. Also, the PAHs condensation had a weak effect on the soot formation rate among different gasifying agents. This study promises a better gasification process design for a two-stage entrained flow gasifier in an oxy-IGCC system.