Equipment Application of Extrusion Granulation Process in NPK Fertilizer Production Lines
Extrusion granulation is an efficient and low-energy method in NPK fertilizer production lines, suitable for producing compound fertilizers with high granule strength. The core of the process is to use mechanical pressure to extrude dry powder raw materials into shape, without the need for additional water or heating, thus reducing energy consumption. The required equipment includes raw material pretreatment machines, extruders, crushing and screening systems, and post-processing devices.
First, raw materials are refined to a particle size of 5-10 mesh using jaw crushers and roller crushers to ensure uniformity. Metering and batching equipment, such as screw scales, precisely control the N:P:K ratio, for example, a 15-15-15 formula. A double-shaft paddle mixer is used to uniformly mix the raw materials, preventing segregation.
The key extrusion equipment is the double-roll extrusion granulator, with adjustable roller gap and pressure reaching 10-20 MPa, extruding the mixed material into thin sheets or rods. The roller surface is engraved with grooves to improve the molding rate. Subsequent crushers, such as chain crushers, break the sheets into 2-5 mm granules, and vibrating screens remove fine powder and oversized particles. A recycling system is used to reuse the rejected material, improving efficiency.
The process flow is: raw material crushing → metering and mixing → extrusion molding → crushing and screening → cooling and packaging. A fluidized bed cooler is used for cooling, rapidly lowering the temperature to prevent sticking. Before packaging, anti-caking agents such as diatomaceous earth can be added to improve storage stability.
The advantages of this process include compact equipment and small footprint, making it suitable for small and medium-sized production lines with an annual capacity of 50,000-100,000 tons. Environmentally, the extrusion process produces less dust, and bag filters are used to control emissions. In a practical case, a Chinese fertilizer plant uses the extrusion process to produce high-potassium NPK fertilizer with a granule hardness of over 30N, suitable for fruit tree fertilization.
In summary, the equipment application of the extrusion granulation process makes NPK production lines more economical and efficient, supporting the needs of precision agriculture.