Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Jesse Zhu

Abstract

A new type of liquid-solid fluidized bed, named circulating conventional fluidized bed (CCFB) which operates below particle terminal velocity was proposed and experimentally studied. The hydrodynamic behavior was systematically studied in a liquid-solid CCFB of 0.032 m I.D. and 4.5 m in height with five different types of particles. Liquid-solid fluidization with external particle circulation was experimentally realized below the particle terminal velocity. The axial distribution of local solids holdup was obtained and found to be fairly uniform in a wide range of liquid velocities and solids circulation rates. The average solids holdup is found to be significantly increased compared with conventional fluidization at similar conditions. The effect of particle properties and operating conditions on bed behavior was investigated as well. Results show that particles with higher terminal velocity have higher average solids holdup.

Summary for Lay Audience

Liquid-solids fluidization system has great potential in applications of food processing, petrochemical, biochemical, and wastewater treatment processes due to its great heat and mass transfer and reaction performance. A new type of liquid-solid fluidized bed (LSFB) called circulating conventional fluidized bed (CCFB), which operates below particle terminal velocity but with external solids circulation was proposed.

Circulating conventional fluidized bed (CCFB) was proposed to overcome the respective short-comes of conventional LSFB and circulating LSFB and combine their advantages as well. Conventional fluidized bed operating at low liquid velocity reduces the energy consumption since the required liquid velocity is lower than the particle terminal velocity. On the other hand, circulating fluidized bed (CFB) provides higher liquid-solids contact efficiency comparing to conventional fluidization. Thus, CCFB is believed to have additional advantages over existing liquid-solid fluidized beds (conventional and circulating), such as allowing continuous operation with regenerated solid particles, achieving higher solids holdup, and providing a better control of the average solids holdup.

This study focuses on the hydrodynamic behaviors of CCFB operating at ambient temperature and pressure with five types of particles made of two different materials (glass and plastic). In CCFB, the axial solids holdup distribution is uniform, and the average solids holdup increases with increasing solids circulation rate. Overall, CCFB is believed to have great potentials in replacing the CFB operations in some industrial processes.

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