High shear granulators consists of a cylindrical or conical mixing bowl, a three-bladed impeller, a chopper, an auxiliary chopper, a motor to drive the blades and a discharge pot. By either circulating hot or cool liquid or steam through the jacket, the mixing bowl is jacketed for heating or cooling the contents of the bowl as the case may be.
The high-shear wet granulation process using high-shear granulator can be divided into 5 stages and they included;
•Binder addition or addition of granulating liquid.
•Wetting of powder and nucleation
•Growth of granules and densification of the powder.
•Granule attrition and breakage.
The impeller which is employed in mixing of the dry powder and spreading of the granulating fluid in high-shear granulator normally rotates at a speed ranging from 100rpm to 500rpm. The chopper forms part of high-shear granulator and is used to break down the wet lump to produce granules. The chopper rotates at a speed of 1000 to 3000rpm. Powder densification and/or agglomeration are by the in cooperation of a granulation fluid into the powder with high-power-per-unit mass, through rotating high-shear forces. #permix
High shear granulators can be subclassified into vertical high shear granulator and horizontal high-shear granulator. These sub-classes are primarily distinguished by the geometric positioning and orientation of the primary impellers.
A vertical high shear granulators are where the impeller shaft rotates in the vertical plane and the impellers are bladelike. The vertical high shear granulators could be either a top-driven (example Colleter-Gral granulator) or a bottom-driven unit (example Diosna or Powrex granulators).
In the horizontal high shear granulators, the impeller shaft rotates in the horizontal plane (or is said to be side driven).
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