Movement of different-shaped particles in a pan-coating device using novel video-imaging techniques |
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Authors: | Pandey Preetanshu Turton Richard |
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Institution: | (1) Department of Chemical Engineering, West Virginia University, PO Box 6102, 26506 Morgantown, MV |
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Abstract: | The purpose of this study was to investigate the effects of particle shape on the movement of particles in a pan-coating device
using novel video-imaging techniques. An area scan CCD camera was installed inside a 24-in pan coater at the same location
as that of a spray nozzle, and the movement of particle was tracked using machine vision. A white tracer particle was introduced
inside a bed of black-coated particles. The effects of pan loading, pan speed, and particle shape on the movement of particles
was studied. The response variables were circulation time, surface time, projected area of particle per pass, dynamic angle
of repose, cascading velocity, and dispersion coefficient. Experiments were conducted at 3 different pan speeds, 6, 9, and
12 rpm, and 2 fill levels (ratio of bed depth to pan diameter), one eighth and one quarter, and data were collected over a
30-minute time period. The differences in circulation times of spheres and tablets, with similar volume equivalent diameter
as that of the sphere, were found to be insignificant at the 95% confidence interval. The circulation time ranged from 2.8
to 10.8 seconds depending on the operating condition and increased with increasing pan load and decreasing pan speed. The
distributions of circulation time, surface time, and projected surface area were found to be nonnormal. The dynamic angle
of repose for tablets was higher than for spheres. Also, the bed surface for spheres was much flatter in comparison with tablets
where the bed shape attained a “wave-like” form. The average velocity of tablets in the cascading layer was found to be significantly
higher than spheres. A linear model (R
2>0.98) best described the variation of velocity as a function of pan speed for all of the operating conditions.
Published: October 6, 2005 |
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Keywords: | pan coater tablet movement circulation time particle shape tablet velocity |
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