【FAQ】Why are the "hardness" and "dissolution rate" of granular fertilizers always at odds?

Raw material pretreatment: Fineness and moisture content determine the granule's "foundation." Fermented organic materials typically have a moisture content of 30%–50%, high viscosity, and high fiber content. The half-wet material crusher uses a dual-stage rotor to break down wet material to a fineness exceeding 60 mesh; its screenless design prevents clogging. Uniform powder fineness ensures a consistent internal granule structure and reliable strength. However, the uniformity of fermentation depends on the turning depth and oxygenation efficiency of the double-screw compost turner—if turning is incomplete, decomposition is uneven, resulting in granules with inconsistent internal layers (varying hardness) that crumble easily under pressure.

Wet granulation: Porous structure, fast dissolution, but low strength. The new-type organic fertilizer granulator and the new-type two-in-one organic fertilizer granulator utilize wet agglomeration, where material rolls into spheres on an inclined pan using its own moisture. The granules retain numerous micropores, allowing for rapid water penetration, quick disintegration, and swift nutrient release—making them ideal for top-dressing. However, this porous structure typically results in a compressive strength of only 10–15 N, posing a high risk of pulverization during long-distance transport. The new two-in-one model integrates mixing and granulation into a single unit, eliminating intermediate conveying steps; it handles high-moisture materials (25%–45% moisture content) effectively and maintains a granulation rate of over 90%. Dry granulation involves high-pressure compaction; while it yields high-strength granules, the dissolution rate is relatively slow. Double-roller press granulators utilize a pair of counter-rotating rollers to compress powdered material into dense sheets under high pressure, which are subsequently crushed and screened. The core principle of this technology is the use of high pressure to increase granule density—achieving a crushing strength exceeding 30N—making the product suitable for long-distance transport and mechanical spreading. However, the dense structure hinders rapid moisture penetration, resulting in a slower dissolution rate, which makes it more suitable for use as a base fertilizer. Dry granulators for organic fertilizer follow the same dry-processing route; they require no added water or drying stages, resulting in significantly lower energy consumption compared to wet granulation processes.

Production line configuration determines final product quality. The screening and material recycling stage within the roller press granulation line is critical: an excessively high recycle ratio leads to repeated compression of fine powder and inconsistent granule strength, while an excessively low ratio allows oversized granules to mix into the final product, causing uneven strength. The recycle ratio is typically maintained between 30% and 50%. Furthermore, the rollers must be replaced when the wear depth on the roller surface exceeds two-thirds of the original pattern depth; failure to do so results in loose compacted sheets and a sharp drop in granule strength.

There is no absolute "better" or "worse" regarding hardness and dissolution speed; it depends entirely on the product's market positioning. Choose wet pan granulation for rapid-acting fertilizers; opt for double-roller extrusion for high strength and slow-release properties; and select BB fertilizer (bulk blending) for formulation flexibility. Before selecting a production line, clearly define your target market and the intended method of application.