Date of Award

Spring 1985

Project Type

Dissertation

Program or Major

Chemical Engineering

Degree Name

Doctor of Philosophy

Abstract

A Loop Fluidized Bed (LFB) based on the fast fluidization concept is a novel method for effective solid-gas contact and can play an important role in coal combustion. It can be operated under pressure making it eminently suited for the production of high temperature gas from coal for operating gas turbines for power generation. The LFB can operate over a wide range of gas flow rates and coal can be introduced at various points without excessive pressure drops. Further, it is possible to capture higher amounts of sulfur dioxide due to the use of fine dolomite or limestone particles. This process can also be used for the smelting of mineral ores. However, the LFB concept is relatively new and data in the literature are scarce.

In this study a bench scale loop fluidized bed has been designed, fabricated and installed. The unit has been operated using sand, limestone, and gypsum particles. The latter two solids are chosen because of their presence in the coal combustion process for sulfur removal. Data have been collected to study the effect of particle size, particle density, air flux, and solid flux on fluidizing characteristics of the three solids.

Extensive data have been obtained to study the effect of particle size, particle density, air flux, and solids flux on fluidizing characteristics of sand, limestone, and gypsum. It is found that solids flow behavior was sensitive to nozzle positions and air flow rates. Three dimensional plots have been prepared for predicting good operating regions for the LFB with respect to nozzle combination, air flow rate and riser solids fraction. Pressure drop data have been correlated with solids velocity and solids fraction to obtain a better solids friction factor equation than available in the literature. A computer program has been developed to predict the static pressure of every point in the LFB. The computer program predictions and the static pressure data show good agreement. Coal combustion and sulfur removal models for the LFB coal combustor have been developed. The predictions from these models agree with commercial data. A conceptual LFB coal combustor has been designed and the results have been compared with commercial coal combustion data. The LFB coal combustion process is found to provide better coal combustion and sulfur removal effectiveness than bubbling bed coal combustion and pulverized coal combustion with limestone injection processes.

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