How to address severe caking in NPK fertilizer production?

NPK fertilizer caking is a frequent and significant problem in both production and application.  It not only severely affects product appearance and ease of use but also reduces nutrient stability, directly impacting the company's economic benefits. The core causes of caking in NPK fertilizer production are mainly excessive moisture, improper temperature control, and crystal precipitation. Effective solutions require precise control throughout the entire production process.

Moisture and temperature control in the production process are fundamental to preventing caking. The drying process in the NPK fertilizer production line must strictly control the moisture content of the finished product.  Adjusting the hot air parameters according to the fertilizer formula ensures that the finished product's moisture content remains below 2%, preventing residual moisture from acting as a "medium" for crystal bridging. The cooling process should avoid "rapid cooling" or "incomplete cooling." A gradient cooling process should be used to reduce the particle temperature to near room temperature (temperature difference not exceeding 5°C), preventing residual heat from causing internal moisture migration and precipitation. At the same time, 0.5%-1% of anti-caking agents, such as diatomaceous earth, zeolite powder, or organic anti-caking agents, can be added to the formula to disrupt crystal adhesion.

Raw material pretreatment and process optimization can further reduce the risk of caking. High-purity, low-hygroscopic raw materials should be selected for NPK fertilizer production to avoid hygroscopic aggregation caused by impurities; the mixing stage should ensure uniform dispersion of raw materials to prevent localized high nutrient concentrations leading to crystallization imbalance. For formulas prone to caking, such as those with high nitrogen content, granulation parameters can be adjusted to produce porous particles, reducing the contact area between particles. In addition, screening equipment should be calibrated regularly to ensure uniform particle size and prevent excessive fine powder from increasing the probability of caking.

Control during storage and transportation is also crucial. Moisture-proof packaging materials should be used, ensuring the packaging bags are dry before packaging and the seals are tight; the storage environment should be ventilated and dry, with relative humidity controlled below 60%, and stacking height should not be too high to avoid excessive pressure on the bottom layer of particles. During transportation, rain and sun protection measures should be taken to reduce the impact of environmental temperature and humidity changes on the fertilizer. Furthermore, a stock rotation mechanism should be established to avoid long-term product accumulation, thus preventing caking throughout the entire supply chain. In summary, solving the problem of NPK fertilizer caking requires adhering to the principle of "prevention first and full-process control." By optimizing production processes, precisely controlling moisture and temperature, scientifically selecting additives, and standardizing storage and transportation, it is possible to reduce the probability of caking at the source, improve product quality, and enhance market competitiveness.