Electronic Thesis and Dissertation Repository


Master of Engineering Science


Chemical and Biochemical Engineering


Jesse Zhu


Liquid solids circulating fluidized beds have great potential to be utilized in many chemical processes for their tremendous advantages. There are many studies about the riser but there is not any information on the downer as yet. This research is devoted to study the axial solids mixing in the downer. A new methodology was developed based on the concept of ion-exchanging ability of resins and the residence time distribution measurement. Resin particles were loaded with calcium ion as the tracer and Peclet number and the axial dispersion coefficient were determined for each set of operating conditions. Different designs of baffles were implemented in order to examine their effects on the axial solids dispersion. The results show that the baffles reduce the mixing substantially and their suppression effects increase with liquid velocity, except at very low liquid velocity where the presence of the baffle increases the mixing. Among the three designs – louver, mesh, and vertical plane, the louver has the most influence as it reduces the mixing coefficient by 60% when Ul = 3.86Umf. Under the same conditions, the mesh and vertical plane reduce the mixing coefficient by 46% and 32% respectively.