What kinds of materials are suitable for granulating with a roller extrusion granulator?
Basically all granular dry processes can be granulated with a roller extrusion granulator. In particular, the size of the raw material powder is less than 2 mm, preferably less than 1 mm, which is very suitable for extrusion granulation. Crushed stone, powder, crystalline, granular and pellet raw materials are suitable. For potassium chloride, lower cost standard grades and by-products or “wastes” (too fine to blend) are suitable for extrusion. Although pelletized urea is available, powdered or crystallized urea of very small size is more suitable.
In some cases, the particle size of the feedstock varies too much, where the larger particles should be broken up first, resulting in a more uniform nutrient distribution in the product.
The smaller the particle size of the raw material, the less separation of the components in the extruded bulk during the pulverization process. The purpose of granulation by the roller extrusion granulator is to obtain fertilizer granules with highly uniform nutrient elements.
There are two methods of breaking:
1: Fertilizer raw materials are broken before compounding, which may bring the problem that during the forming process, due to the poor fluidity of the broken raw materials, it will cause bridging phenomenon and reduce the accuracy of measurement.
2: Before adding the return material (the particle size of the return material is generally lower than the requirement), pulverize the composite mixture in a pulverizer, so that the raw material mixture has a uniform particle size and distribution before extrusion granulation. A possible problem with this method is that, due to the presence of air in the feedstock mixture, higher specific forming pressures are required to produce high-density sheets. Especially when urea is one of the raw materials of compound fertilizer, the heat will soften the raw material with low melting point, which will make the material flow difficult.
Although the above two methods have their own shortcomings, they also have their own advantages under specific conditions, so they should be selected according to the actual situation on site and different process conditions.