Granulation is the core step in NPK compound fertilizer production, directly determining the particle shape, strength, and nutrient uniformity of the product. Depending on production scale, fertilizer concentration, and process requirements, the commonly used granulators in the industry mainly include rotary drum granulators, extrusion granulators, disc granulators, and high-tower granulators. Each type of equipment has its advantages and is suitable for different production scenarios.

The rotary drum granulator is currently the most widely used model in NPK compound fertilizer production and is considered the industry's "mainstay." Its core is a rotating drum tilted at 3-5°. During operation, the uniformly mixed nitrogen, phosphorus, and potassium raw material powder is fed into the drum, while steam or water is sprayed in. The tumbling force generated by the drum's rotation agglomerates the raw material into granules, with a particle size controllable at 2-4mm. This model is suitable for the production of medium- and low-concentration compound fertilizers, offering high capacity, strong raw material adaptability, and flexible formula adjustments based on crop needs. A single unit can achieve a daily output of 50-100 tons and is widely used in large-scale fertilizer production enterprises.
Extrusion granulators are primarily used for high-concentration, binder-free production. Their core component is a pair of counter-rotating extrusion rollers. The mixed dry powder raw materials are extruded under 15-20 MPa high pressure, eliminating the need for subsequent drying and effectively preventing binders from affecting fertilizer purity. The produced granules have high strength and uniform nutrient distribution, but their production capacity is relatively low, making them more suitable for small to medium-sized production lines.
Disc granulators are known for their simple structure and low cost, making them suitable for small-scale production plants or pilot production. They use a 15-25° inclined rotating disc, utilizing centrifugal force and friction to agglomerate the raw materials into granules. Workers can control the granule size by adjusting the disc's rotation speed and tilt angle. This model is easy to operate but requires manual monitoring, with a daily output of only 5-10 tons. Granulation uniformity is relatively poor, making it suitable for applications where high precision is not required.
High-tower granulators are the preferred equipment for high-end, high-concentration compound fertilizers. Molten urea is mixed with phosphate and potassium fertilizers, then sprayed down from the top of a tower, where it cools and solidifies to form smooth granules. Its products exhibit good solubility and strong moisture resistance, but require high equipment investment and raw materials compatible with high temperatures, making it suitable for large-scale, high-end compound fertilizer production.
Choosing the right granulator is crucial for improving the quality and production efficiency of NPK compound fertilizer. Enterprises need to consider their own production capacity, product positioning, and cost budget to rationally select the appropriate model, achieving a dual improvement in production efficiency and product quality.