Granular materials: The primary concerns during mixing are breakage and segregation. Bulk-blended fertilizer production involves finished granules such as urea, ammonium phosphate, and potassium chloride. Since these granules are already finished products, the mixing task is simply to achieve accurate proportioning and uniform blending without altering the granule shape. The NPK blending machine utilizes a dual-shaft paddle structure where the shafts rotate in opposite directions, creating a three-dimensional tumbling motion within the chamber; this results in a mixing time of 2–5 minutes, a coefficient of variation (CV) for uniformity of ≤5%, and a granule breakage rate controlled to within 0.5%. The core of the entire NPK blending production line lies not in the mixer itself, but in batching accuracy and anti-segregation design—raw material particle size differences must be kept within ±0.5 mm, and drop heights during conveying minimized; otherwise, even a perfectly mixed batch may still undergo segregation after packaging.

Powder and wet materials: The primary concerns during mixing are clumping and shaft wrapping. Organic fertilizer raw materials often have moisture content levels of 30%–50%, high fiber content, and high viscosity; standard mixers struggle with such materials, as they tend to wrap around the main shaft and clog the discharge outlet. The organic fertilizer double-shaft mixer employs two symmetrical spiral shafts rotating synchronously to create three-dimensional convection within the chamber, achieving a mixing uniformity of over 95%. It is equipped with a water-spraying humidification system that evenly applies water or binders during mixing, adjusting the material's moisture content for subsequent granulation. The loading factor is recommended to be kept between 60% and 70%, and residual material must be cleaned out after each shift to prevent caking from affecting the next mixing cycle. Materials containing microorganisms are highly sensitive to heat during the drying process. The survival rate of the functional bacteria in bio-organic fertilizers plummets when temperatures exceed 60°C. Consequently, bio-organic fertilizer dryers must employ a low-temperature, high-airflow strategy, utilizing an inlet air temperature of 60–80°C while ensuring the discharge temperature does not exceed 45°C. Although trading temperature for higher airflow increases fan energy consumption, it preserves the viability of the bacterial strains. If hot air temperatures are raised to save electricity, massive bacterial die-off occurs, downgrading the product to ordinary organic fertilizer; the resulting loss in sales value far outweighs the savings on electricity costs.