Semester

Fall

Date of Graduation

2002

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Richard Turton.

Abstract

This study focuses on the application evaluation of a prototype backscatter imaging LDV system (BILS). This non-intrusive instrument has the ability to record particle images and two-dimensional velocity data simultaneously. A series of validation tests were conducted to verify the operation of the system. These included comparing the velocity of a wire, attached to a rotating disc, with known angular frequency (measured by digistrobe), with that measured by the instrument. The results were found to be in good agreement. The imaging part of BILS was calibrated using a target with known dimensions.;The terminal velocities and particle sizes of near-spherical, Nu-pareil sugar particles were investigated using BILS for five different size cuts. The results were in good agreement with the drag curve proposed by Haider and Levenspiel, 1988. The images of the particles obtained were used to estimate the sphericity (phi), which was found to be very close to 1 (0.98 < phi < 0.99). A qualitative study on the effect of particle loading and drop height on the particle velocity was also carried out. In the course of this study, it was observed that the velocity of free falling particles was affected by the solids loading in the particle stream.;After successful validation of both the imaging and the velocity part of the system, it was used to record real-time particle velocity data, near the wall region of a 15 m high riser section of a cold-flow circulating fluidized bed (CFCFB) located at NETL, Morgantown. The effects of superficial gas velocity and solids circulation rate on the particle velocity were studied for nine different operating conditions. The particle velocity near the wall was found to increase in the upward direction with increasing superficial gas velocity and in the downward direction with increasing solids circulation rate.;The phenomenon of 'clustering' of particles near the wall region was also studied for different operating conditions. A criterion was proposed to define a cluster. Although a more rigorous analysis is recommended for future work, the preliminary results show that the mean velocity of the clusters was between 0.2-1 m/s in the downward direction, for most of the operating conditions studied. The average cluster length was found to be about 2 to 4 cm. In addition, it was found that the operating parameters, such as solids circulation rate and superficial gas velocity, effect the distribution of the cluster velocity and cluster length.

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