Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Jesse Zhu

Abstract

In this work the hydrodynamic behavior of an inverse liquid-solid circulating fluidized bed (ILSCFB) system was studied. In addition, the hydrodynamic characteristic of the inverse liquid-solid fluidization under the conventional fluidization regime was also studied. The system consists of a downer with an inner column diameter of 7.6 cm and a height of 5.4 meters, an upcomer (riser) with an inner column diameter of 20 cm, a separator, and feeding and returning pipes which connect the downer and the upcomer. Based on the axial hydrodynamic behavior of the ILSCFB, it was found that the axial solids holdup in the downer is uniform. Similar to the heavy-particle LSCFB, the circulating fluidization regime in the downer was separated into the two zones including the initial circulating fluidization zone and the fully developed circulating fluidized zone as a function of the total liquid velocity in the downer. The effects of the solids inventory and the counter current flow in the upcomer on the hydrodynamics of the downer were also studied. Afterwards, the radial distribution of particles was studied in the downer of the ILSCFB. Interestingly, the radial structure of the two-phase flow was completely different from the case of the heavy-particle LSCFB. It was found that the solids holdup was greater in the center than near the wall of the downer. Finally, the conventional (non-circulating) inverse liquid-solid fluidization was studied in a column with a large diameter for the first time. The minimum fluidization velocity was obtained experimentally and compared with the Richardson and Zaki model. It was concluded that the Richardson and Zaki model can predict the bed expansion in the case of the inverse liquid-solid fluidization when the terminal velocity was calculated by the model of free rising light particles.

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