What causes granule adhesion during the drying stage of a bio-organic fertilizer production line?
In the drying section of a bio-organic fertilizer production line, issues such as granules clumping together and adhering to the drum walls or lifting flights stem from four primary categories: inherent raw material properties, the state of the granulated semi-finished product, drying process parameters, and structural equipment defects; the compounding of these factors significantly increases the rate of substandard products.
- Excessively high initial moisture content in wet granules is the primary trigger. If the moisture content of granules discharged from disc or extrusion granulators exceeds 30%, the excess free moisture on the surface creates high stickiness, causing them to clump upon contact inside the dryer. Incomplete pulverization of coarse fibers or uneven particle size distribution results in loose granules that retain moisture; the surface remains wet, and exposure to hot air creates a soft, paste-like layer, leading to adhesion under pressure. High proportions of fresh manure in the formula—along with high salt, organic matter, and colloidal content—further exacerbate this stickiness.
- Imbalance between drying temperature and airflow velocity. If the hot air temperature at the feed end is too high, the granule surface instantly forms a soft, sticky paste layer; internal moisture cannot escape, causing the sticky surfaces to bond together. Conversely, if airflow is insufficient and the dryer drum rotates too fast, granules lack adequate residence time; surface moisture isn’t dried before they continue to tumble and pile up, forming large, sticky clumps. If the hot air temperature is too low, drying is incomplete, and the material remains damp throughout; this leads to extensive material buildup on lifting flights and drum walls, causing new granules to stick to these deposits and form agglomerated masses.
III. Issues with bio-organic fertilizer equipment operation and material distribution. Uneven material distribution at the feed end causes localized material piles to become too thick, leading to adhesion caused by the pressure on the bottom layer of granules. Dryer lifting flights lacking anti-stick coatings allow organic powder to adhere to the iron surfaces; this buildup thickens over time, continuously trapping new granules. A large drop height at the feed inlet causes wet granules to impact and pile up at high speeds, leading to deformation and adhesion due to compression. Delays in the cooling process prevent the timely removal of surface moisture; residual heat causes moisture to migrate back to the surface after the granules exit the drum, leading to secondary clumping before screening.
- Deficiencies in auxiliary materials and operation/maintenance management. Excessive binder addition during the granulation stage results in granules with excessive plasticity, compounded by a lack of separating agents such as talc or calcium powder. Failure to regularly clean accumulated material from the drum walls and lifters allows dried fertilizer layers to soften upon moisture absorption, leading to persistent adhesion. Additionally, raw materials absorb moisture during rainy weather, causing localized moisture fluctuations in the semi-finished product; this results in widespread granule clumping during drying, while the recirculation of high-humidity exhaust gas into the drum further exacerbates surface re-wetting and adhesion.
