Numerical Simulation of Gas-Solid Flow in a Multi-Stage Fluidized Bed
1.State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China; 2.University of Chinese Academy of Sciences, Beijing 100049, China
Abstract Flow behavior of a multi-stage fluidized bed (MFB) which couples a bubbling fluidized bed and a fast fluidized bed (FFB) was simulated using Eulerian two-fluid model. The simulations show that there are multiple flow regimes existing in the MFB, and the flow field is not the simple superposition of the two flow patterns. Solid concentration profile is a typical “C” shape below the entrance of circulation region, while it is an exponential shape along the upper FFB; that agrees with the cold-model experiments very well. Meanwhile the influence of gas velocity and solid circulation rate on the solid distribution was also studied. The results show that the solid concentration near the wall regions fluctuates more severely, and it is more sensitive to the change of operating condition in the upper FFB. A biased flow near the entrance of circulating solid region and a particle splash in the reduced pipe region were predicted; both phenomena were observed in the experiments. The simulation results can be used to guide the design and optimization of MFB.
