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The force exerted on particles is of great significance to the flow and reaction characteristics of particles in gasifier. In this study, the unbalanced thrust, especially its magnitude, of a single char particle induced by chemical reactions during combustion process is investigated numerically, based on the random distribution of active sites.It is revealed that the nonuniform distribution of active sites directly leads to the nonuniform absorption of reactants and release of products, which accounts for the net induced thrust on particles. The effects of active site ratio, ambient gas temperature and particle diameter on the induced thrust of reacting particles were investigated. The results show that the induced thrust on particles could be equal to the magnitude of particle gravity. The induced thrust is determined by the nonuniformity of carbon distribution on char surface. The net thrust is enhanced with the increase of specific carbon consumption rate.

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This work is devoted to the numerical study of particle dispersion prediction of gas-solid coaxial jet with a larger concentration difference. In pulverized coal gasifier, the pulverized coal is very dense at the nozzle outlet, and its volume fraction can reach 0.3. Then, it is dispersed rapidly under the action of highspeed annular gas, and the particle volume fraction in the space is less than 0.002. In order to better predict the motion characteristics of a gas-solid jet with a high concentration gradient, the applicability of the three models is compared. The results show that the dense discrete phase model (DDPM) and Eulerian two-fluid model (TFM) models considering particles collision can accurately predict the dense jet flow at low annular gas velocity. The DDPM and discrete phase model (DPM) show a good simulation for the dispersion characteristics of particles at high annular velocities where the particles' collision could be ignored. Therefore, DDPM has better adaptability for coaxial jet with large concentration gradient. The DDPM was used to predict the particle velocity and concentration for different annular gas velocities and different particle mass loads. It is found that particle flow is contracted first and then dispersed gradually under the action of airflow. The particle dispersion range increases with the increase of solid loading rate, and the corresponding radial distribution of particle velocity is greater.