Numerical Simulation of Gas-solid Flow Behaviours in Desulfurization Tower Based on Monte Carlo

The optimization of gas-solid flow behaviors in circulating fluidized bed for flue gas desulfurization(CFB-FGD) was simulated.The particles trajectories were calculated by the direct simulation Monte Carlo(DSMC) method,and the gas motion was modeled by the improved k-e two-equation turbulent model.All equations were solved numerically on the unstructured meshes.Interactions of particle-fluid,particle-particle and particle-wall were considered rigorously based on the four-way coupling method.An effective model for searching the local unstructured mesh in which the individual particle lay was proposed to achieve ‘one-to-one’ interaction between phases.Gas-solid flow patterns before and after adjustment were obtained,as well as the distributions of the particle concentration and the gas/particle axial velocity.Further,critical factors that strongly influenced the residence time and collision frequency of particles were analyzed.Final results highly confirm the feasibility and effectiveness of the scheme chosen to optimize the gas-solid flow behaviors within the tower.After adjustment,the gas-solid flow field appears symmetrical ideally,and the interior space of the tower is utilized in full.Residence time of the particles with the same radius comes to be in chorus relatively.The particle residence time is related closely to the continuum flow field and the particle physical properties.Particle collision frequency decreases distinctly compared with that before adjustment.