Investigation the Strong Swirling Gas-Solids Flow in Cyclone Separators Based in a Circulating Fluidized Bed Based on Process Tomography and CFD Simulation

Cyclone separator plays an important role on the separating of fine ash from flue gas in a circulating fluidized bed (CFB) system. The gas-solids flow is strong swirling turbulent and the flow characteristics, i.e. flow velocity profiles both for tangential and axial velocity vector, will affect the fine particle separating efficiency. Especial, with the scaling up of a CFB system from small scale to industrial scale, the cyclone diameter increases and the separating efficiency decreases. In addition, with the increase of thermal capacitive, the number of cyclone also increases and the mal-distribution of solids flux among different cyclones becomes serious. This mal-distribution of solids flux will affect the heat and mass transfer balance inside the CFB riser and lead to low combustion efficiency. Therefore, it is necessary to investigate the flows in cyclones and to understand the flow characteristics change with the increase of cyclone dimensions and cyclone number in CFB system. In this research, details computation fluid dynamics (CFD) based on different turbulent models, i.e. standard k-eps two equations models, RNG k-eps model and Reynold Stress Turbulent model, will be given to investigate the swirling flow fields in cyclones. To account for the effect of the stochastic characteristic of the instantaneous gas velocity on the particles, the improved Lagrangian stochastic model based on the Reynolds stress model for gas phase was adopted, which attributed to the successful prediction of the turbulence anisotropy and particle crossing-trajectories effects. Meanwhile, electrical capacitance tomography (ECT) will be applied and conical shape ECT sensors will be designed. Solids concentration will be given based on ECT measurement results. Different arrangement of cyclones in a CFB system are investigated and details CFD simulation results will be given to reveal the dimensions effect on the gas-solids flow characteristics. Optimized design based on CFD simulation and ECT measurement will be given in the end of this research.