In the production of organic fertilizers, excessively soft granules are a common quality problem. This manifests as granules that crumble easily when squeezed and are prone to powdering, which not only affects storage and transportation but also reduces the stability of nutrient release, thus hindering the product's market competitiveness. Soft granules are not caused by a single factor, but rather the result of the synergistic effect of multiple aspects of organic fertilizer production, including raw materials, equipment, and processes. Accurate identification of the causes and targeted adjustments are necessary to effectively solve this problem.
Unreasonable raw material characteristics are the fundamental cause of soft granules. Imbalanced moisture content is the most critical factor; excessive moisture leads to too much water inside the granules, preventing the formation of a compact structure, while insufficient moisture results in insufficient binding force between granules, making them easily loose and brittle. The appropriate moisture content should be controlled between 20% and 35%, adjusted according to the type of raw material. In addition, uneven particle size and insufficient cohesiveness of raw materials can also cause problems. A high proportion of coarse fiber materials or incomplete crushing, as well as insufficient addition of binders, will reduce the compactness of granule formation.
Improper equipment parameter settings are a core influencing factor. The pressure and rotation speed parameters of granulation machines such as disc and drum granulators directly determine the compactness of the granules. Insufficient pressure prevents the material from being fully compressed and formed, resulting in large pores inside the granules; excessive rotation speed leads to a short material residence time, making it difficult for the material to fully bind and compact, while too slow a speed reduces production efficiency. At the same time, wear on the granulator roller surface and die holes can lead to uneven pressure transmission, further exacerbating the problem of soft granules.
Incomplete subsequent processes can prevent the improvement of granule strength. Insufficient drying is the main problem; low drying temperature and insufficient drying time prevent the complete removal of moisture from inside the granules, leaving them in a soft state for a long time; the lack of post-maturation treatment prevents the internal components of the granules from reacting stably, also affecting hardness. In addition, an unreasonable return ratio, where unqualified fine powder is not properly recycled, can lead to a decrease in granule formation rate and insufficient strength.
Targeted solutions should follow the principles of "source control, process optimization, and subsequent strengthening," throughout the entire organic fertilizer production process. On the raw material side, strict control of moisture content is necessary, along with crushing the materials to a suitable particle size and adding appropriate binders such as bentonite. On the equipment side, precise control of granulation pressure and rotation speed is required, along with regular inspection and maintenance of equipment components. On the process side, the drying stage needs to be strengthened to ensure the moisture content of the granules meets the standards, and post-curing treatment should be added if necessary. Simultaneously monitoring the granule state in real time during production and dynamically adjusting parameters will ensure the stable production of organic fertilizer granules with satisfactory compactness, balancing both product quality and production efficiency.
