What are the methods for NPK fertilizer granulation?

NPK compound fertilizers, which provide a balanced supply of nitrogen, phosphorus, and potassium nutrients, are a core fertilizer in agricultural production. Granulation is a critical step in the NPK fertilizer production line, directly affecting the fertilizer's application effect, storage stability, and nutrient release efficiency. Currently, the main NPK fertilizer granulation methods include extrusion granulation, rotary drum granulation, and disc granulation. Each method relies on different technical principles and is adapted to different production needs.

Extrusion granulation is a dry granulation technology that achieves molding through mechanical pressure. The process involves feeding uniformly mixed NPK dry powder raw materials into an extruder, forming thin sheets through roller extrusion, and then obtaining uniform granules through crushing and screening. This method does not require the addition of water, has low energy consumption, and produces granules with precise nutrient content. It is suitable for producing high-concentration, low-moisture NPK compound fertilizers.  However, the granules have high hardness, requiring supporting crushing and screening equipment, and the method has strict requirements on the particle size of the raw materials.

Rotary drum granulation is one of the most widely used wet granulation technologies. Raw materials are placed in a tilted rotating drum, and through spraying atomized water or a binder, the materials gradually agglomerate into granules using rolling friction. This method has high production efficiency, produces round granules, and is highly adaptable, capable of handling various raw material ratios. It is suitable for large-scale industrial production. However, it requires supporting drying equipment to remove moisture, resulting in relatively high energy consumption, and the uniformity of nutrient distribution in the granules is easily affected by the degree of raw material mixing.

Disc granulation is similar in principle to rotary drum granulation, both being wet agglomeration granulation methods. The core equipment is a tilted rotating disc. The material in the disc is subjected to the combined action of centrifugal force, gravity, and friction, and gradually forms granules after the binder is sprayed in. Its advantages include a simple equipment structure, small footprint, and low investment cost, making it suitable for small and medium-sized production enterprises. However, its production capacity is limited, and the uniformity of particle size is slightly inferior to rotary drum granulation.

In summary, different granulation methods have their own advantages and disadvantages. Production enterprises need to choose the appropriate granulation technology based on product positioning, production scale, raw material characteristics, and cost budget to achieve a balance between product quality and production efficiency.