Backflow is a common problem in organic fertilizer granulation, causing not only raw material waste and increased energy consumption, but also reduced production efficiency and affecting the quality of finished granules, becoming a key bottleneck restricting large-scale organic fertilizer production. Backflow mainly manifests as the return of unqualified powder or fragments after granulation. If not handled properly, it can create a vicious cycle, exacerbating production costs. Based on industry experience, this problem can be systematically solved from three core dimensions: raw materials, equipment, and processes.
Optimizing raw material pretreatment to solidify the granulation foundation is a prerequisite for reducing backflow. Imbalanced raw material moisture content is the primary cause of backflow. The moisture content must be strictly controlled between 20% and 22%. If too dry, water or a binder can be added via atomized spraying; if too wet, dry materials such as straw powder or sawdust can be added to adjust. Simultaneously, the problem of insufficient raw material viscosity needs to be addressed. 2%-5% of binders such as bentonite or humic acid can be added, or highly viscous raw materials such as livestock manure can be mixed in to enhance agglomeration. In addition, raw materials need to be crushed to below 3mm in advance, and the particle size distribution needs to be adjusted to avoid excessive fine powder or coarse particles leading to increased return material.
Precisely controlling equipment parameters and optimizing hardware operation are key to solving the return material problem. The tilt angle and speed of the disc or rotary drum granulator must be adapted to the characteristics of the raw material. For organic fertilizer granulation, the tilt angle should be controlled at 18°-22° and the speed at 12-15 r/min to ensure sufficient tumbling and agglomeration of the material. Wearing liners and scrapers should be replaced promptly, and heightening baffles should be installed to prevent material overflow or excessive sliding, thus improving the granulation rate. Simultaneously, the die compression ratio and feed knife position should be checked and adjusted or replaced as needed to reduce return material caused by equipment deviations.
Standardized operating procedures and strengthened process control are guarantees against return material. Controlling the feeding speed ensures it matches the equipment's processing capacity and avoids insufficient material accumulation and tumbling. Using a ring-shaped spray device to spray water evenly in small amounts multiple times prevents uneven moisture distribution. By reasonably controlling the return material ratio to 15%-25%, and crushing the unqualified particles after screening and recycling them as "seed particles," waste can be reduced while improving the pelleting effect.
In summary, solving the problem of return material in organic fertilizer granulation requires synergistic optimization of raw materials, equipment, and processes. Standardized pretreatment, precise equipment control, and standardized operating procedures can effectively reduce the return material rate, increase the pelleting rate, and achieve cost reduction, efficiency improvement, and quality upgrades in organic fertilizer production.
