Date of Graduation

2004

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Hisashi O. Kono

Committee Member

John R. Loth

Committee Member

Peter G. Stansberry

Committee Member

Alfred H. Stiller

Committee Member

Charter D. Stinespring

Abstract

The attrition of fluidized particles and the erosion of in-bed tubes (IBT) cause serious practical problems in operating fluidized bed reactors, particularly in fluidized bed combustion systems (FBC-systems). In order to provide a basic understanding and an effective control of the attrition and erosion phenomena, a novel approach has been developed in this study. The proposed approach differs in three ways from the conventional one. First, the peaks of transient particles' forces prevailing in a fluidized bed (responsible for erosion of in-bed tubes and attrition of fluidized particles) were measured, and represented by fracture critical values (FCV) of sensitive tracer stresses. This application of special sensitive tracers in place of conventional piezo-electric sensors is one of the key technical points. Secondly, the FCV stresses were correlated with the transient gas pressure fluctuation under various design and operating conditions. Thirdly, a good correlation was obtained between FCV stresses and the transient gas pressure fluctuation, yielding the dimensionless number K* (solid-gas transient stress ratio). Using these relationships, FCV stresses could be indirectly predicted by measuring the FCVs corresponding to the transient gas pressure fluctuation with an appropriate data-processing technique, regardless of the reactor's scale and geometry. Through the proposed approach, a new method was developed to predict the attrition rates of fluidized particles and the erosion rates of IBT, based on the FCVs of tracer stresses in fluidized reactors. It was demonstrated that these experimentally measured quantities are in good agreement with the predicted results.

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