Abstract��
The fluidization mechanism of gas solid concurrent with gravity field is disparate with that of gas solid countercurrent with gravity field. In both the downer and the riser, higher local solid concentration results in the reduction of drag coefficient. In the downer, reduction of the drag force will increase local particle and gas velocity, which in turn reduce the particla aggregation. However, in the riser, reduction of drag coefficient will decrease the local particle and gas velocity, which in turn increases the tendency of the particle aggregation. Compared with the riser, the downer have several distinct advantages such as short gas solids resident time, more uniform distribution of gas solids velocity and solids content, and reduced axial backmixing. The condition of gas solid contact in the downer is more close to plug flow.
ZHOU Ru jin, WEI Fei, JIN Yong .Analyzing on Fluidization Characters of Gas-Solid Concurrent/Countercurrent with Gravity Field[J]. Chemcial Industry and Engineering, 2001,18(3): 182-187
2001, Vol. 18 
