As fertilizer transitions from raw powder to a finished product, the state of its surface is constantly evolving: the powder is rough, the granulated particles are porous, the rounded granules are smooth, and the coated granules are hydrophobic. Each stage reshapes the granule’s “outer shell”—a feature that directly dictates whether the material will flow seamlessly through subsequent processing steps or encounter persistent obstacles.
half wet material crushing: The rougher the surface of the powder, the more effectively it absorbs moisture for granulation. When fermented organic matter is processed through a half wet material crusher, the surface is torn to reveal numerous fresh, exposed areas, significantly increasing the specific surface area. This roughness allows the material to be more easily wetted by moisture and coated by binders during granulation, accelerating the formation of granules. Conversely, if the material is not crushed finely enough, the resulting coarse particles will have smooth, angular surfaces; this leads to poor adhesion, causing “sandwich” defects (internal structural weaknesses) and resulting in low overall granule strength.
Disc granulators and new type organic fertilizer granulators: Porous surfaces facilitate rapid moisture absorption and quick disintegration. new type organic fertilizer granulators (including “two-in-one” models) utilize a wet-agglomeration process, where material adheres layer-by-layer using its own moisture content, leaving a network of micropores on the granule surface. This porosity allows the granules to break down rapidly upon contact with water, ensuring a quick release of nutrients—making them ideal for use as top-dressing fertilizers. However, this same porosity can also absorb atmospheric moisture; if the packaging lacks sufficient moisture resistance, the granules may absorb humidity and clump together during storage. new type “two-in-one” granulators integrate mixing and granulation into a single unit; because the material spends less time inside the machine, the surface porosity is more uniform than that produced by traditional disc granulators, leading to more consistent moisture-absorption characteristics.
Ball Shaping Machine: Transforming a “burred, rough surface” into a “smooth outer shell.” Granules exiting a granulator often feature burrs and sharp edges. During transport, these protrusions rub against one another, generating fine dust; during packaging, they can interlock, impairing flowability. An organic fertilizer spheronizer (Ball Shaping Machine) utilizes friction and rolling between the granules to smooth out sharp edges and polish the surfaces, thereby increasing sphericity while reducing surface roughness. A smoother surface results in a lower coefficient of friction, improved flowability, and more uniform coating. However, spheronization must not be excessive; if the surface becomes too smooth, the granule’s hydrophilicity decreases, slowing down its disintegration rate and compromising its immediate effectiveness.
Coating machine: This applies a “functional coat” to the granules. The machine sprays a coating agent onto the granule surface, creating a hydrophobic film. The quality of this film depends on the state of the granule surface: on smooth, dense surfaces, the coating agent is distributed evenly, ensuring a stable slow-release effect. Conversely, on rough, porous surfaces, the agent may seep into the micropores, leading to uneven thickness—too thick in some areas and too thin in others—which causes the slow-release profile to become unpredictable. Therefore, spheronization and screening prior to coating are essential steps: spheronization provides a smooth substrate, while screening removes granules with surface defects.
BB (Bulk Blend) fertilizer mixer: This process does not alter the granule surface but rather aims to preserve it. BB fertilizer production follows a distinct approach: since components like urea, ammonium phosphate, and potassium chloride are already finished granules, the production line focuses solely on physical blending. The core of the BB fertilizer mixing process is “shape-preserving blending,” which employs low-speed, gentle tumbling to achieve a mixing uniformity (coefficient of variation, CV) of ≤5%, while keeping granule breakage to within 1%–2%. If the mixing duration is too long or the rotational speed too high, the granule surfaces may wear down, exposing their internal porous structure; this increases hygroscopicity and exacerbates the segregation of ingredients. While BB fertilizer production does not involve reshaping the granule surface, it must strictly maintain the original surface integrity.
The granule surface serves as an invisible thread running through the entire production line: pulverization creates a rough surface; granulation forms a porous surface; spheronization polishes it into a smooth surface; coating adds a functional layer; and BB fertilizer mixing ensures the preservation of the original surface. The surface condition at each stage determines whether the subsequent step can be navigated successfully. When selecting a production line, do not focus solely on the roundness of the particles; instead, examine the origin and the intended destination of their surface characteristics.