NPK compound fertilizer granulation is a crucial step in mixing and agglomerating nitrogen, phosphorus, potassium, and auxiliary materials into uniform granules. Its quality directly determines the fertilizer's application effect, storage stability, and market competitiveness. However, in actual NPK fertilizer production, various problems can easily arise during the granulation process due to multiple factors such as raw material characteristics, equipment parameters, and operating procedures. This not only reduces production efficiency and increases raw material loss but also affects the quality of the finished product, requiring close attention and timely control.

Improper raw material matching is the most basic and common problem in the granulation process. NPK fertilizer raw materials are complex, and imbalances in moisture content, viscosity, and proportions can all lead to problems. Excessive moisture content easily causes materials to stick to the equipment, forming large clumps, and the granules are prone to cracking and loosening after drying. Insufficient moisture content results in raw materials lacking binding properties, making it difficult to agglomerate into granules, resulting in a powdery finished product and a significantly reduced forming rate. Furthermore, insufficient raw material viscosity and an excessive proportion of fine powder or coarse particles will result in loose and brittle granules, making it difficult to meet standard forming rates. Imbalanced raw material ratios will also affect granule density, creating a risk of clumping during storage.
Improper equipment parameter control directly impacts granulation results. Whether using a disc granulator or a rotary drum granulator, deviations in parameters such as inclination angle and rotation speed will lead to poor granule formation. An excessively large inclination angle results in insufficient material residence time, leading to incomplete agglomeration and uneven granule size; an excessively small inclination angle causes excessive material accumulation and insufficient tumbling, easily forming fine powder or loose granules. Excessively high rotation speed will cause excessive centrifugal force, resulting in material breakage; too low a speed results in insufficient centrifugal force, hindering effective agglomeration. Additionally, issues such as wear on the inner walls of the equipment and insufficient edge height will exacerbate granule formation defects.
Improper operating procedures are a significant contributing factor to unstable granulation quality. Fluctuations in the feeding rate can cause material volume fluctuations within the equipment, resulting in uneven tumbling intensity and significant differences in particle size. Improper water or slurry spraying methods can lead to uneven moisture distribution, with some areas being excessively wet and clumping, while others are too dry and loose. An imbalance in the return material ratio also affects granulation; insufficient return material results in a lack of "seed particles," making it difficult to form stable aggregates; excessive return material leads to overly coarse particles with insufficient density, making them prone to breakage after drying. Furthermore, incomplete subsequent drying and cooling can cause excessive moisture content in the particles, making them susceptible to moisture absorption and clumping during storage.
These problems are interconnected and mutually influential, increasing screening and rework costs, reducing fertilizer utilization, and impacting the user experience for farmers. Therefore, NPK fertilizer production lines must strictly control raw material pretreatment, precisely adjust equipment parameters, standardize operating procedures, establish a routine monitoring mechanism, and promptly identify and resolve various potential problems during the granulation process to improve granulation quality and ensure the competitiveness of NPK fertilizer products.