Coal Gasification in a Two-Stage Entrained Flow Gasifier under O₂/CO₂ Conditions

Coal gasification in industrial gasifiers faces challenges related to tar and soot formation, which affect performance and emissions. This study proposes a new numerical approach for simulating coal gasification in a two-stage entrained flow gasifier under different O2/CO2 ratios-blown conditions. The modeling framework incorporates a static simulation for the combustor and couples a multistep coal devolatilization model with an expanded gas-phase reaction model in the reductor. Model validation against experimental data showed prediction accuracies ranging from 4 to 20% for the devolatilization model and from 3 to 25% for the gas-phase reaction model across various species. The validated framework was employed to investigate the effect of varying O2/CO2 ratios in gasifying agents on the gasification performance. Results showed that increasing the O2/CO2 ratio from 30% to 50% increased H2 production from 3.69% to 13.03% and CO from 34.40% to 55.04% while reducing CO2 from 48.27% to 19.96%. Higher O2/CO2 ratios inhibited soot formation but increased the tar yield, although the final tar concentration remained well below 1 mg/Nm3. This study highlights the potential of using oxy-fuel gasification with CO2 recirculation for optimizing syngas quality and advancing CO2 capture, offering valuable insights for industrial gasifier design and operation within oxy-fuel IGCC systems.