Analysis of SO_2 and NO_x Emissions Using Two-Fluid Method Coupled with Eddy Dissipation Concept Reaction Submodel in Circulating Fluidized Bed Combustors

摘要

Large eddy simulation (LES) of the gas-second order moment (SOM) of particles model based on the two-fluid method coupled with the subgrid-scale (SGS) reaction submodel is applied to investigate SO_2 and NO_x emissions in circulating fluidized bed (CFB) combustors. The SGS reaction submodel based on the eddy dissipation concept (EDC) model is developed considering the effect of particles to calculate the SGS reaction rates. The predicted results by the model are in good agreement with the experimental data. The flow characteristics including concentration and SOM of particles are analyzed. The simulation results show the particles including coal particles and desulfurizer particles are mixed sufficiently. The velocity fluctuation of particles is enhanced for the combustion process, and the velocity fluctuation in the axial direction is about 2 times higher than that in the radial direction. The reaction characteristics including the molar fraction of species and the distribution of chemical reaction rates with concentrations are also obtained. It can be found that the SGS reaction rates not only improve the homogeneous reactions of gas but also influence the heterogeneous reactions.