Squeezing granulation method is a common processing technology in fertilizer production. Compared with wet granulation method, the squeezing granulation machine does not need to add water when producing fertilizers. This dry granulation method does not require the entire production line to be equipped with large equipment such as drying machines and cooling machines, which simplifies the production process and greatly reduces equipment investment. Therefore, investing in an extrusion granulation production line is also a very suitable project when producing compound fertilizers.

1. The storage, measurement, and mixing of fertilizer raw materials such as urea, ammonium phosphate, potassium chloride, etc. are transported to the storage bin by bucket elevators and belts. The number of storage bins, the complexity of measurement and mixing techniques, and the number of components in the product formula are related. When producing compound fertilizers, intermittent mixing operations are generally used. The raw materials of each component in the formula are weighed in the weighing bin, and after meeting the formula requirements, they are all added to the intermittent mixer for mixing. Trace elements can also be added to the mixer. In order to ensure uniform particle distribution of trace elements, high-strength mixers are selected.

2. The principle of extrusion granulation is to shape the material through the squeezing of the granulator roller skin. The mixed material is forcibly fed into the gap between two opposite rotating roller shafts through a vertical screw conveyor. During the extrusion process, the pressure on the material gradually increases. When the gap between the two shafts is very small, the pressure on the material is relatively large, and then gradually decreases until 0. During the extrusion process, due to the reduction in material volume, the apparent density of the mixture can increase by 1.5-3 times. The product after extrusion is usually a flat plate covered with particles, which needs to be crushed into particles in the subsequent crushing process.

3. The plates formed in the roller extrusion granulator need to be further crushed and graded to achieve the required particle size. There are two counter rotating wolf toothed roller crushers under the granulator, where the bonded flat particles are crushed into several small particles. Thin sheets are relatively easy to transport and can be further crushed by subsequent crushers. The crushed raw materials are divided into large particles, product particles, and small particles on a multi-stage sieve. The fine particles on the screen are recycled back to the mixer and then extruded into shape. The large particles that are trapped in the upper layer of the multi-stage sieve need to be further crushed. After crushing, return to screening. In high-strength crushers, the softer parts of the flakes are crushed into high-strength and wear-resistant particles, which are not finely ground during transportation and use.

4. Under normal circumstances, the product needs to undergo one to two steps of polishing and finishing. Irregular shaped particles are rounded at edges and corners using a grinding drum. The fine powder generated during the polishing process is sieved and recycled for further granulation. When repairing, anti caking agents are usually added to facilitate the long-term storage and stacking of fertilizers.