Lower-than-expected output is a common efficiency bottleneck in fertilizer production, and raw material moisture and particle size are often the two most easily overlooked culprits. These two parameters, seemingly simple, directly determine the pelleting rate, particle strength, and the operational stability of the entire production line.
Moisture: Too High or Too Low, Both Cause Trouble
Material moisture is the most sensitive control variable in the granulation process. When moisture is too low, the material lacks viscosity, particles cannot effectively agglomerate, resulting in a low pelleting rate, more return material, and consequently, lower output. When moisture is too high, the material easily adheres to the inner wall of the equipment, forming clumps that clog the discharge port, and in severe cases, even causing equipment overload and shutdown.
Recommended control range varies depending on the process and raw materials. For rotary drum granulators producing organic fertilizer, the recommended raw material moisture content is between 25% and 35%, with the “golden range” for most materials being 28%–32%. Compound fertilizer granulation typically requires a moisture content of 8%–12%. For roller extrusion granulation, the particle size distribution should be controlled at 15%–20%, ideally forming a clump when squeezed but crumbling easily when released. This needs slight adjustment depending on the raw material—highly viscous materials like chicken and pig manure can have a lower distribution (approximately 25%), while fibrous materials like straw and mushroom residue require a higher distribution (30%–35%).
Particle Size: A Balance of Fine and Coarse Particles is Key
Particle size directly affects granulation efficiency. Ideally, the granulated material should have a balanced particle size distribution—fine powder (particle size <0.1mm) acts as the “binding core,” while coarse particles (particle size 0.1–1mm) form the “skeleton.” If the material is too fine, it easily forms “overly wet clumps”; if it is too coarse, the contact area between particles is small, resulting in insufficient agglomeration.
Roller extrusion granulation requires the material to pass through an 80–120 mesh standard sieve (particle size 0.125–0.18mm), with a sieve residue percentage ≤5%. When the fineness is below 80 mesh, the particles are loose and lack strength; if the fineness is too fine (>120 mesh), it easily absorbs moisture, clumps, and clogs the die holes, potentially causing a sharp drop in output of over 30%. In disc granulation, the core particle size is controlled at 1.0–2.0 mm, and the finished particle size can reach 2.5–3.5 mm.
Parameter Optimization Path
It is recommended to systematically check and adjust in the following order: First, measure the moisture content—use a rapid moisture analyzer for accurate detection; if it exceeds the standard, adjust by adding dry material or spray humidification; second, check the particle size—sample and sieve to confirm that the fineness meets the standard; coarse materials need to be crushed twice, and excessively fine materials need to have the crusher screen adjusted; finally, calibrate the equipment—check the gap between the pressure roller and the die (0.2–0.5 mm) and clean any clogged die holes.
Through systematic parameter optimization, the pelleting rate can be stabilized at over 90%, the particle strength reaches ≥20 N/particle, and the hourly output is expected to increase by 15%.
Optimizing moisture and particle size is not a one-time fix but an ongoing discipline that directly determines the profitability of every bio organic fertilizer production line. For dry compaction routes, a roller press granulator production line demands strict control of fineness (80–120 mesh) and low moisture to prevent die clogging and output losses exceeding 30%. In wet granulation, the disc granulator machine and organic fertilizer disc granulator require a moisture window of 28–32% and a balanced core particle size of 1.0–2.0 mm to achieve a stable pelleting rate above 90% and particle strength ≥20 N. By systematically checking moisture, screening fineness, and calibrating roller gaps, producers can raise hourly output by 15%, reduce return material, and ensure consistent, high-quality granules — turning parameter control into a competitive advantage.
