In organic fertilizer production lines, granulation is a key step in addressing the problems of organic fertilizer clumping and nutrient loss. Unlike traditional chemical fertilizers, organic fertilizer raw materials are primarily composed of organic matter such as straw, livestock and poultry manure, and mushroom residue. A targeted process is required to convert these loose raw materials into granular products. This not only preserves the activity of the organic matter, but also improves transportation and application convenience, thereby contributing to the development of ecological agriculture.
The first step in the process is specialized pretreatment of the organic raw materials. First, the livestock and poultry manure, straw, and other raw materials are composted and fermented. A compost turning machine controls the fermentation temperature at 55-65°C for 15-20 days, killing insect eggs and pathogens while converting difficult-to-decompose organic matter into easily absorbed nutrients. After fermentation, the raw materials are processed through a pulverizer to a 60-80 mesh size (lower than chemical fertilizer fineness to avoid damaging the organic matter structure). Auxiliary materials (such as humic acid and wood ash) are then mixed in proportion, and a small amount of water is added to adjust the moisture content to 25%-30% (higher than chemical fertilizer pretreatment moisture due to the higher water absorption of organic matter) to form a loose mixture.
The second step is the core granulation process adapted for organic fertilizers. The main methods used are disc granulation and flat die extrusion granulation. Disc granulator involves feeding the pretreated material onto a rotating disc tilted at 30-45 degrees, rotating at 20-30 rpm. Friction and centrifugal force within the disc gradually agglomerate the material into round granules with a diameter of 3-5 mm. A small amount of water is sprayed during the process to enhance the granule's stickiness. Flat die extrusion granulation is targeted at organic fertilizers with high fiber content. The flat die granulator's rollers squeeze the material through the die holes to form cylindrical granules. This process requires no binders, maximizes the activity of the organic matter, and is suitable for bio-organic fertilizer production.
Finally, the granules undergo post-processing. The formed granules first enter a drum fertilizer dryer (controlled at 60-80°C to prevent high temperatures from damaging beneficial microorganisms) to reduce the moisture content to below 15%. After drying, they are cooled to room temperature in a cooler before passing through a sieving machine to separate unqualified granules. Fine particles are returned to the fermentation stage, while larger particles are crushed and re-granulated. The final qualified particles are coated by a coating machine and then directly packaged and stored using a packaging machine to ensure the ecological characteristics and application effect of the organic fertilizer.
