Ag Gyp is mined from deposits and is marketed as a powder. It can range in purity from less that 60% to more than 90% on a dihydrate equivalent basis. Since it was ground, it will pass through screen tests ranging from 50 to 200 mesh, and each batch will contain a range of material sizes.
However Ag Gyp is not always easy to handle. It requires special handling and spreading equipment. It is dusty. It cannot be blended with other products. And, the spread can be uneven. However for those used to handling lime and other powdered products, it can be worked with.
Ag Gyp can be pelletized which makes it easier to handle and less dusty. Pelletizing allows it to be blended with other dry fertilizer products and can be spread by today’s fertilizer equipment. Pelleted gypsum is free flowing, low in dust, pH neutral and the spread or distribution is more even. It is just easier to work with, handle and ship.
Pelletization is a less expensive method of processing Ag Gyp powder. A pellet mill combines a powder with moisture. This moist material is forced through a die, forming elongated pellets which are then cut into smaller pellets by a blade. Lime, gypsum, wood, and livestock feed can be pelletized.
Fertilizer can also be manufactured as a prill, which is a more sophisticated form of pellet. Prills, like pellets, are small aggregates of a powdered material. Prills are neater, do not disintegrate as quickly as pellets, create less dust and allow you to bind together multiple products that are uniformly distributed through the prill.
Prills are formed by dropping the melted material from the top of a tall prilling tower. The droplets congeal and dry into roughly spherical shapes, 3-4mm in diameter. Fertilizers such as urea, potash, ammonia sulfate, monoammonium phosphate (MAP), diammonium phosphate (DAP) and others are manufactured as prills.
When blending together multiple products, as in the fertilizer industry, prills are preferred because they are more resistant to breaking down. If you are applying a single product, such as lime or gypsum, pelletizing is a less expensive form of processing and provides many of the same benefits as prilling. Both are easier to handle when compared to a crushed powder.