Simulation of Gas-Solid Flow Characteristics in Multi-Stage Fluidized Bed and Downcomer
CHEN Cheng 1, YANG Yao 1, HUANG Zhengliang 1, SUN Jingyuan 1, WANG Jingdai 1, YANG Yongrong 1, LI Jinan 2
1. State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China;
2. Chenzhou Sinochem Fuyuanxincailiao Company, Chenzhou 424202, China
Abstract：By using the porous media model to simulate the gas distributer, a method was established to simulate the typical structural unit of the multi-stage fluidized bed via computational fluid dynamics (CFD). Based on it, the effect of operating gas velocity on the fluidization state in adjacent bed layers and particle flow behaviors in the downcomer was studied. The results showed that the particle bed in the downcomer had a buffering effect which made the particles quickly dispersed after entering the lower bed and ensured the homogeneity of solid phase in the lower bed. With the increase of operating gas velocity, the gas short-circuited into the downcomer from the lower bed increased, resulting in two effects on particle overflow. Firstly, in the downcomer, the solid concentration of dense phase zone decreased, the concentration gradient, the length of dense phase zone and the length of transition zone increased, then bubbles and gas embolism started to appear in the dense phase zone. Secondly, due to the enhanced blocking effect of the ascending airflow in the downcomer, the intermittent solid flow from the upper bed to the downcomer became more difficult, and the particle accumulation occurred above the downcomer. The change of particle flow state and the increasing difficulty of intermittent particle flow from the upper bed to the downcomer may be the possible reasons for the instability of particle overflow.
CHEN Cheng 1,YANG Yao 1,HUANG Zhengliang 1 et al. Simulation of Gas-Solid Flow Characteristics in Multi-Stage Fluidized Bed and Downcomer[J]. Chemical Reaction Engineering and Technology, 2021, 37(5): 446-456.
