Effects of gas-solid drag model on Eulerian-Eulerian CFD simulation of coal combustion in a circulating fluidized bed

Abstract

The Eulerian-Eulerian two fluid model (TFM) has been widely used to simulate the fluidized bed combustion/gasification process, where the dense gas-solid flow, heat and mass transfer, and various chemical reactions are coupled. Significance of the drag coefficient in determining the gas-solid flow characteristics is well known. However, effects of the drag coefficient on the overall performance of the fluidized bed combustion/gasification are not emphasized. In the present work, two widely used drag models, namely the EMMS model and the Gidaspow model, are applied to simulate the coal combustion in a circulating fluidized bed combustor. Performance of the hydrodynamics, temperature, and species distribution by the two models is compared in details. It is found that the EMMS result has a better agreement with the experimental data compared to the Gidaspow result in this work. This work indicates that reliability of the gas-solid drag coefficient lays a solid foundation for the comprehensive simulation of the fluidized bed combustion process, not only for the gas-solid flow characteristics.