Chemical and Petroleum Engineering Department, Sharif University of Technology, P.O. Box 11365-11155 Tehran, I.R. IRAN
Experimental work was carried out to investigate the influence of impeller speed, granulation time, binder mass and their interactions on granule size distribution, mean size and binder content distribution in a conical high shear granulator. It was observed that the response of high shear granulation to changes in process parameters varies significantly from one operating condition to another. For all quantities of binder, the granule mean size increased with time at lower impeller speeds, while the opposite trend was observed at higher impeller velocities. For long mixing times, increasing impeller speed decreased the granule average size constantly; whereas for other durations, an increase in the mean size followed by a decrease was observed across ascending impeller speeds. It was also found out that variations of the span of granule size distribution can be utilized to indicate the dominant rate process. Coalescence which was prevailing at lower impeller speeds, was limited by attrition, breakage or shattering at higher impeller velocities. Binder-solid ratio of granules showed a continuous increase across size at lower impeller speeds and a maximum at middle size range for higher impeller velocities. Binder content distribution showed different trends with time at different operating conditions. Furthermore, increasing impeller speed limited the domain of binder content variations and made the granule binder-solid ratio to be much closer to theoretical value.
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