Numerical Simulation Of Gas-Solid Flow In Cyclone Separator Of CFB Boiler

The cyclone separator is one of the most important components in CFB boilers. Its efficiency is vital for the proper operation of the boiler. In order to make the equipment serve the industry better, the gas-phase flow filed in the cyclone separator was numerical studied by using the commercial software FLUENT. The simulation results based on the Reynolds stress model are in good agreement with the measured results. The results show that the gas flow filed is asymmetric due to the asymmetry of the inlet structure and the unstable characteristics of the swirl flow, and the vortex center of the gas flow is deviated from the geometrical center of the cyclone; the high gas swirling intensity and shear flow characteristics of the axial velocity in the vortex finder are contributed to the energy loss. Besides, the effects of the structural parameters and operating conditions on the gas phase flow were studied to provide references for the design and operation of cyclone separator, including the area ratio of cyclone cross-section to inlet section (KA), the diameter ratio of the vortex finder to the cyclone ( d~r ), the diameter ratio of the dust discharge to the cyclone ( d~c ), inlet velocity ( Vi ) and temperature (T). Finally, on the basis of the gas flow field, solid particle trajectories were simulated by using the two-way coupling lagrangian scheme. The results show that particle motion is very complex and has a great randomness. For the fine particles, the main factors influencing the efficiency are the air entrainment in the inner vortex region, short-circuit flow near the vortex head and re-entrainment at the bottom of discharge cone. For the larger particles, the main influencing factors are"upper dust ring"near the top plate and short-circuit flow near the vortex head. The above results have a certain reference value for the research on the separation mechanism of cyclone separator.