Semester

Spring

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Richard Turton

Abstract

The purpose of this study was to investigate the variables that affect the mass coating variability (CV) in a pan coating process. A novel video-imaging technique was used to record the movement of tablets inside the pan. The effects of pan loading, pan speed and particle shape were studied. The response variables were circulation time, surface time, projected surface area, dynamic angle of repose, cascading velocity (2 directions), and dispersion coefficient. Experiments were conducted at 3 different pan speeds, 6, 9 and 12 rpm, and two pan loadings. The circulation time ranged from 2.8-10.8 s, 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 non-normal. The average velocity of tablets in the cascading layer was found to be significantly higher than spheres. A linear model (R2>0.98) best described the variation of velocity as a function of pan speed. The video-imaging technique was also successfully used to quantify the effect of baffles on the mixing inside the pan.;The video-imaging data were used as an input to a mechanistic model to predict CV from measurements using Monte Carlo simulations. The effects of pan speed, coating time, tablet size, pan loading, spray flux distribution inside the spray zone, spray shape, and spray area were investigated. Coating experiments were conducted to verify the predictions from the Monte Carlo simulations, and the trends predicted from the model were found to be in good agreement to the experiments when the exact experimental conditions were taken into consideration for the simulations.;Results of DEM (discrete element modeling) simulations were compared with those obtained from video-imaging experiments and the trends obtained from DEM and experiments were found to be good agreement. Velocity profiles along the entire top cascading layer of particles were also estimated. The particles in the cascading layer were found to reach their maximum velocity at positions close to the mid-point of the cascading surface. Comparison of simulated velocity profiles showed good agreement with published scaling laws for rotating drums, and an improved correlation for scaling with respect to the pan loading was proposed.;This information will be useful to any coating process and will be of importance when devising ways to reduce the CV in coating operations. It can also be used effectively to develop scale-up models, test the effects of parametric changes on CV, and subsequently reduce the time required to get products to market.

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