Spray granulation - cooling granulation
Advantages of granulate produced in Ammag fluidized bed plants
The principle
a) Spray-dry granulation
A dust-free granulate is produced from a solution or suspension. Spray-dry granulation combines the processes “spray drying” and “granulating” in one facility. In the upstream plant part the suspension and/or solution is atomized into fine droplets to achieve the large exchange surface required for drying. Following gravitation, the droplets move downward in counterflow. As soon as they are nearly dry they hit the fluidized bed consisting of granulated particles. As the droplets still have some residual humidity, they will stick to these particles, thus creating, by agglomeration, an almost dust-free granulate that is independent of the atomized primary particles. The rest of the solvent is dissipated in the fluidized bed. The properties of the granules can be varied between “highly porous” and “compact”.
b) Cooling granulation
Cooling granulation can be considered as a variant of spray-dry granulation. Instead of a solution and/or suspension a molten mass is atomized, which is cooled in the gas flow, where the almost solidified droplets hit the fluidized bed. Agglomeration is caused by the material which is still partly molten. Again, the final product is a solid granulate.
Legend:
Sprühtropfen - spray droplet
Aufziehen - absorbing
Verfestigen - solidifying
Zwiebelstruktur - bulbous structure
fertiges Granulat - finished granulate
Partikel - particle
Examples/solutions
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Agricultural chemistry - for example: pesticides
Pesticides are often available as water-dispersible granulate (WG), affording easier handling and application safety (no dust) compared with powders. Unmixing, which is frequently found in case of liquids, is not possible. Fluidized bed granulation ensures maximum drying efficiency at precise temperature control, even for thermally instable products.
(Click to enlarge image)
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Feed industry - for example: wood sugar molasses
Wood sugar molasses is a byproduct that is generated, among others, in particle board production. It serves as animal feed. However, being available as a viscous liquid and being easily perishable, it is used only infrequently.
By spray granulation in the fluidized bed it can be turned into a product suitable for storage, which can be fed to animals.
(Click to enlarge image) |
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