Optimization of multiple-chamber fluidized beds using coarse-grained CFD-DEM simulations: Regulation of solids back-mixing

The intense solids back-mixing has been one of the major disadvantages of gas-solid fluidized bed reactors for certain applications. In this study, coarse-grained CFD-DEM simulations are carried out to regulate the solids back-mixing in multiple-chamber fluidized beds by investigating the effect of the orifice size, the orifice location, the gas velocity of each chamber, and then the effect of the pipe length connecting adjacent chambers. The results indicate that optimizing the orifice size, the orifice location, and the gas velocity of each chamber can suppress the solids back-mixing to a certain extent. However, there is still a gap between the optimized design and the ideal situation. Therefore, using a sufficiently long pipe instead of a baffle with orifice is further proposed to completely suppress the solids back-mixing between adjacent chambers, which is validated using coarsegrained CFD-DEM simulations. Present results provide a means to regulate the solids back-mixing in multiplechamber fluidized beds via proper design of bed geometry.