Granulation is one of the core processes of NPK fertilizer production line, which determines the quality and performance of fertilizer particles.
When the evenly mixed raw materials enter the fertilizer granulator, the granulation process officially begins. There are various common methods for NPK fertilizer granulation, among which rotary drum granulation is widely used. In the rotary drum granulator, the raw materials continuously roll in the rotating drum. At the same time, an appropriate amount of adhesive is sprayed into the drum through the nozzle, which acts as a bridge to gradually aggregate the loose raw materials into particles.
Disc granulation is also a common method. The disc granulator rotates at a certain speed, and the raw materials are added from above. Under the centrifugal and frictional forces of the disc, they roll along the inner wall of the disc. As the rolling process progresses, the raw material continuously adsorbs surrounding materials and gradually grows into particles. This method produces particles with regular shapes and high roundness.
Squeezing granulation is the use of a roller squeezing granulator. The mixed material is fed between two relatively rotating rollers, and under strong extrusion pressure, the material is squeezed into thin sheets. Then, through subsequent processes such as crushing and screening, the desired particle size is formed. The particle density and strength produced by extrusion granulation are relatively high.
During the granulation process, parameters such as temperature, humidity, and rotational speed have a significant impact on particle quality. For example, an appropriate temperature helps the adhesive to function better and promote particle formation; If the humidity is too high, particles are prone to adhere, while if the humidity is too low, it is not conducive to aggregation. Both too fast and too slow rotation speed can affect the size and uniformity of particles.
After granulation is completed, the newly formed particles are still relatively fragile and require a certain amount of time for solidification. The solidification process can enhance the internal bonding force of particles and improve their strength. After solidification, the particles are ready to enter the subsequent drying, screening and other processes, and move towards the final qualified NPK fertilizer product.