Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Mechanical and Materials Engineering

Supervisor

Dr. Chao Zhang

2nd Supervisor

Dr. Jesse Zhu

Joint Supervisor

Abstract

Liquid-solid circulating fluidized bed (LSCFB) reactors are obtaining extensive attraction in the extraction process of functional proteins from industrial broth. A typical LSCFB is comprised of a riser, a downcomer, a liquid-solid separator, a top solids-return pipe and a bottom solids-return pipe. In light of the literature review conducted in this research, a detailed modeling of the protein extraction using an LSCFB ion-exchange system requires a microscopic study including hydrodynamic field, mass transfer and kinetics reactions.

A computational fluid dynamics (CFD) model was developed to simulate the hydrodynamics of the two phase flow in an LSCFB riser. The model is based on Eulerian–Eulerian (E-E) approach incorporating the kinetic theory of granular flow. The predicted flow characteristics agree well with our earlier experimental data. Furthermore, the model can predict the residence time of both liquid and solid phases in the riser using a pulse technique.

A numerical model was developed to predict the protein extraction process using an LSCFB ion exchange system. The model for the riser is an extension of the previous CFD hydrodynamic model for the riser incorporating the kinetics reaction. The model for the downcomer includes a one-dimensional mathematical model using the adsorption kinetics correlations. The numerical predictions were compared favorably with the experimental data from a lab-scale system. The model was used to investigate the effects of operating condition on the protein production rate and the system efficiency.

For further study on the hydrodynamics in the downcomer of an LSCFB, the CFD technique was used to simulate the counter-current two phase flow in the downcomer. The model is based on E-E approach incorporating the kinetic theory of granular flow. The predicted results agree well with our earlier experimental data. Furthermore, it is shown that the bed expansion of the particles in the downcomer is directly affected by the superficial liquid velocity in downcomer and solids circulation rate.

As results, it is demonstrated that the developed CFD model can be adapted to simulate and control the other applications of the LSCFB, such as wastewater treatment, petroleum and metallurgical industries.


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