Simulation and comparing of the effect of oxidizing gas and different devolatilization models in an entrained-flow coal gasifier

Gasification technology is an important part of the clean coal technology. For further development of this technology, the processes inside the gasifier and the interactions of injected gas and solid fuel particles need to be understood. In the current study, a numerical simulation of an entrained flow coal gasifier is investigated using experimental operating conditions. The reactions and kinetic parameters of the gasification process are fitted using coal gasification data obtained from similar published papers. Comparison of the simulation results, experimental data and two other similar studies confirm the accuracy of the developed model. The focus of this study is on the accuracy of the models presented for the devolatilization process and the effect of the oxidizer change from oxygen to air on the gasifier performance. Four devolatilization models are investigated including chemical percolation devolatilization, single rate, Kobayashi and constant rate models. The predicted trends of species changes are similar in different devolatilization models but the amount of produced syngas is somewhat different depending on the accuracy of each model. The Kobayashi and constant rate models predicted the devolatilization rate lower than the other two models. The results obtained from the chemical percolation devolatilization model are more consistent with experimental data compared to other models, but require higher computational times. The use of air oxidizing agents rather than oxygen reduces the species mole concentration of produced syngas and hence reduces the gasifier efficiency.