Comprehensive Numerical Simulation Of Char Combustion And Gasification Process

Oxy-fuel combustion is a technology that can achieve zero CO₂emission for coal-firedpower plant, having the advantage of engineering feasibility, non-technical barrier,pollutant coordination removing and so on. With the growing greenhouse effect, oxy-fuelcombustion has becomes research focus at home and abroad. Combustion char acteristics ofcoal char under oxygen-rich condition is a compulsory basic study of oxy-fuel combustion,which can be studied by means of experimentation and model simulation. With thedevelopment of computer technology, numerical simulation is increasingly becoming animportant means to study the combustion process.In this paper, a simple mathematical model for char combustion and gasificationprocess under air condition is developed first, and it has been validated by using theexperiment data. The model takes into account heterogeneous and homogeneous chemicalreactions, multicomponent convection and diffusion inside the particle pores, as well as inthe boundary layer. It also takes into account the physical properties of the gas mixture.Verification results show that the simulation results can agree with experimental resultswell. Then, the established model for char combustion and gasification process is used for acomprehensive simulation studies. The distributions of the main char acteristics during charcombustion and gasification process are analyzed. And the effects of parameters such astemperature, particle size, pressure on the combustion and gasification process of char arealso studied. Simulation results show that the model predictions for the distributions of themain char acteristics and the effects of the parameters are both in line with the general lawsof physics. Finally, a kinetic model of char for oxy-fuel combustion is developed, and thesimulation analysis for the coal char combustion under oxy-fuel condition is carried on.Simulation results show that during the char combustion under oxy-fuel condition, thecontribution of CO₂and H₂O gasification reactions to the consumption of carbon can’t beignored, and the rate of gasification reactions can affect the distributions of temperature andspecies mole fraction significantly.The comprehensive numerical simulation for the combustion and gsification process of char in the paper is meaningful for understanding combustion and gasification processesand revealing their essence.