How Is 15-15-6 Compound Fertilizer Produced?

In farmlands across the world, we often see a type of compound fertilizer labeled "15-15-6," which contains balanced amounts of nitrogen, phosphorus, and potassium. But have you ever wondered how these uniform little pellets are made? The journey from raw materials to finished product combines chemistry, engineering, and environmental technology. The Mainstream Process: Spray Granulation Currently, about 60% of large-scale global production uses the "spray granulation process," the preferred method for mass production. The entire process can be summarized as follows: raw materials are mixed and reacted into a slurry, which is then sprayed like a mist into a tall tower, cooling and solidifying into granules as it falls. First, high-purity raw materials (such as urea, monoammonium phosphate, and potassium chloride) are finely ground and precisely proportioned and mixed. Subsequently, they undergo a chemical reaction in a reactor vessel to form a homogeneous slurry. This slurry is pumped to the top of a granulation tower several tens of meters high and sprayed into fine droplets by high-speed centrifugal atomizers. As these droplets fall through the tower, they encounter rising cool air, rapidly cooling, drying, and solidifying into rounded pellets. Finally, after screening, anti-caking treatment, and packaging, the finished fertilizer is ready. Alternative Process Options Besides the mainstream spray granulation, several other processes cater to different needs: Agglomeration/Granulation: Lower investment, suitable for small to medium-scale production. It forms granules by tumbling moist material, but granule uniformity is slightly lower. Compaction/Extrusion: Similar to extruding noodles, this method compacts mixed powder directly into strands and cuts them, requiring no drying and thus having low energy consumption. However, the granule shape is irregular. Melting/Granulation: A high-end process that melts raw materials before granulation. It produces extremely strong granules of excellent quality, but the technical barriers and costs are also the highest.

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