The uniformity of NPK fertilizer blending directly determines the stability of its effectiveness and is a critical link in the production of high-quality compound fertilizers on NPK fertilizer production lines. Blending requires considering raw material characteristics, operating procedures, and equipment suitability to avoid nutrient stratification and excessively high local concentrations.

Raw material pretreatment. Nitrogen, phosphorus, potassium, and trace element raw materials should be crushed separately to 80-100 mesh to ensure uniform particle size and prevent sedimentation; moisture content should be controlled at 8%-12% to avoid caking or excessive dust affecting mixing. Impurities should also be removed to protect core equipment such as fertilizer mixers and ensure product purity.

Controlling mixing sequence and proportion accuracy. Follow the principle of “fine before coarse, light before heavy, and pre-mixing small amounts of auxiliary materials”: first add fine and light raw materials such as urea to the fertilizer mixer machine, then add coarse and heavy raw materials such as potassium chloride; small amounts of auxiliary materials such as trace elements should be pre-mixed and diluted with fine materials before being added to the main system to prevent local enrichment.

Equipment operation and time control. Prioritize the use of a double shaft paddle mixer, controlling the rotation speed at 25-35 r/min, and adjusting the mixing time to 5-10 minutes according to the amount of raw materials to avoid insufficient or excessive mixing (excessive mixing can easily lead to stratification). Discharge the material promptly after mixing to reduce the residence time in the equipment and prevent secondary caking.

Mixing quality verification. Sampling should be conducted using the “quartering method” to ensure that the nutrient variation coefficient is ≤5%; if the standard is not met, check the raw material pretreatment, mixing sequence, or fertilizer mixer parameters, and optimize and adjust accordingly.