Wet granulation is a core technology in organic fertilizer production, enabling the resource utilization of organic waste and improving fertilizer quality. Using water or a binder as a medium, it forms powdered organic fertilizer into granules through physical agglomeration. It boasts advantages such as high granulation rate, rounded granules, and uniform nutrient distribution, and is widely used in the production of mid-to-high-end organic fertilizers. The entire organic fertilizer making process is interconnected, requiring precise control of parameters at each stage to produce qualified products.
Raw material pretreatment is the foundation of wet granulation. First, well-rotted organic raw materials, such as livestock and poultry manure, straw, and mushroom residue, are processed into a fine powder of 60-80 mesh using crushing equipment to remove impurities and large particles, ensuring the raw materials are uniform and fine. Then, according to the formula requirements, the fine powder raw material is mixed with an appropriate amount of binder and trace elements. Simultaneously, moisture is adjusted through atomized spraying, controlling the material moisture content to 15%-25%, laying the foundation for subsequent granulation. This step directly affects the granulation rate and strength.
The core granulation stage is the key to the process. Pre-treated materials are fed into granulation equipment, commonly including disc granulators and agitator granulators. Taking a disc granulator as an example, the tilting rotating disc generates centrifugal force and friction, causing the material to continuously roll within the disc. The moist fine powder adheres to each other, forming tiny nuclei, which then gradually agglomerate and grow. By adjusting the disc's rotation speed and tilt angle, the particle size can be controlled between 2-6 mm. Agitator granulators, on the other hand, use high-speed rotating agitators to stir and compress the material, causing it to agglomerate into spheres, achieving a granulation rate of over 90%.
The granulated particles then need to undergo drying, cooling, and screening. Freshly produced wet particles have high moisture content and low strength. They are fed into a dryer and dried at a temperature below 80°C to prevent high temperatures from damaging beneficial microorganisms and nutrients in the organic fertilizer, reducing the moisture content to below 10%. The dried particles are then cooled in a cooler to prevent further agglomeration, and then screened. Qualified particles proceed to the next stage, while oversized particles are crushed and returned to the granulator for reprocessing. Excess powder is recycled as nuclei.
Finally, there is the packaging and inspection of the finished product. Qualified granules are coated and then weighed and sealed in a fully automatic packaging scale, with product parameters labeled. Simultaneously, samples are taken to test granule strength, moisture content, nutrient indicators, etc., to ensure compliance with industry standards. The entire organic fertilizer production process requires strict control of parameters such as moisture and temperature to ensure granule quality and achieve efficient utilization of organic waste, thus contributing to the development of green agriculture.
