2026/07/03
Extrusion granulation of potash fertilizer (potassium chloride/potassium sulfate) is a significant technical challenge in fertilizer production. Unlike urea and ammonium phosphate, which have good plasticity, potash fertilizer is a brittle material, lacking viscosity and plasticity. It is easily broken and decomposed during extrusion, leading to low pelleting rate, insufficient particle strength, and agglomeration/pulverization. Currently, granular potassium chloride required for blended fertilizers (BB fertilizers) is primarily produced using the roller pressing method. This article analyzes the technical challenges and solutions in potash fertilizer extrusion granulation from three dimensions: material brittleness treatment, roller pressure setting, and yield improvement.
I. Material Brittleness Treatment: Overcoming the "Non-granulation" Dilemma
Both potassium chloride and potassium sulfate are sandy raw materials with no viscosity and no plasticity, making granulation using conventional methods extremely difficult. When brittle materials are extruded, some particles are crushed, with fine powder filling the gaps between particles; potassium sulfate has even worse plasticity, resulting in a far less effective extrusion than potassium chloride.
The solution lies in a multi-pronged approach. First, controlling the fineness of the raw materials is crucial—potassium chloride achieves optimal pelleting when the fineness is controlled at 0.3–0.4 mm. Second, adding binders is an effective method. Urea, potassium chloride themselves, and a small amount of water all act as binders; fillers such as bentonite and attapulgite can also be added (the addition amount can reach more than 20%) to improve the pelleting rate and particle strength. Furthermore, moisture control is paramount—when the moisture content of the mixture is controlled at 1.4%–1.6%, the pelleting rate of a single extruder can reach 75%–85%. Excessive moisture will reduce the material's fluidity, while insufficient moisture will make it difficult to form pellets.
II. Roller Pressure Setting: Finding the Balance Point of "Dense but Not Crumbleable"
The extrusion pressure of the roller press granulator is the core parameter determining the pelleting effect. The pressure directly affects the density and yield of the pellets.
Insufficient pressure results in too many voids between the particles, making it impossible to form a dense filter cake, leading to insufficient particle strength. Excessive pressure can easily trigger "re-aggregation" between material particles, making the filter cake difficult to break and grade, and also exacerbating wear on the roller surface and bearings. Domestic extrusion granulation pressure is generally low, resulting in correspondingly lower product compressive strength; while advanced foreign equipment uses extrusion pressures 2-3 times higher than domestic equipment, producing superior product performance.
Regarding adjustment methods, a comprehensive judgment needs to be made based on the main motor operating current, material particle size, grindability, and filter cake looseness. When the material particle size is large and grindability is poor, the pressure can be appropriately increased. A simple criterion is that if the filter cake can be easily broken by hand, the pressure is insufficient; if it is difficult to break, the pressure is too high. Temperature control is also crucial—particle friction during extrusion raises the temperature, which should generally be controlled between 70-80℃, adjustable via internal roller cooling water circulation.
III. Improving Yield: From "Low Yield" to "High Efficiency" Process Optimization The yield of potash fertilizer extrusion granulation is constrained by multiple factors and requires systematic optimization.
Regarding raw material pretreatment, the potash fertilizer needs to be dried and pulverized before feeding to ensure suitable moisture content and particle size. Equipment precision directly impacts yield—processing errors such as roller hole depth, spacing, and shape are magnified several times under high pressure, directly leading to low particle strength and low yield. Screening and return material control are equally crucial—the hourly output is most stable when the system return material rate is controlled at 12–16 t/h. Particle breakage rates at each stage (approximately 10% in primary screening, 20% in drying, and 5% in cooling) are the main factors limiting output. Optimizing the lifting plate structure and material conveying method in the drying and cooling stages is expected to increase output by 15%.
Furthermore, post-processing polishing is necessary—irregular particles are rounded using a grinding roller, and an anti-caking agent is added to further improve product quality.
In summary, the difficulty in potash fertilizer extrusion granulation essentially lies in controlling the behavior of brittle materials under high pressure. Precise raw material pretreatment, reasonable pressure setting, and system process optimization are all indispensable. Mastering these three breakthroughs is essential to transform potash fertilizer from "difficult to granulate" to "highly efficient" high-quality granular products.
Mastering the extrusion granulation of potassium fertilizers is not merely a material‑handling challenge—it is a critical competency that directly impacts the quality and cost‑effectiveness of downstream NPK production. The three core breakthroughs—brittleness control through precise moisture and binder addition, optimum roller pressure balancing density and crushability, and systematic yield optimization via pretreatment and screening—are essential for transforming potash from a “difficult‑to‑granulate” raw material into high‑strength, free‑flowing granules. These principles are equally valuable when applied to broader npk fertilizer formula processing, where potassium salts are combined with urea and phosphates to meet specific crop nutrient ratios. The same double roller press granulator technology used for potash can be integrated into a complete npk fertilizer manufacturing process, where npk fertilizer raw materials processing—drying, grinding, and premixing—sets the stage for consistent granulation. Advanced npk granulation machine technology now offers real‑time pressure monitoring and automatic roller‑gap adjustment, enabling stable operation even with challenging potash feedstocks. By incorporating these solutions, the npk fertilizer granulator becomes a versatile unit capable of handling urea, ammonium phosphate, and potassium salts with minimal changeover, ensuring uniform granule strength and nutrient distribution. Ultimately, overcoming the challenges of potash extrusion granulation unlocks the full potential of blended fertilizers, delivering products that resist caking, flow smoothly in application equipment, and provide consistent nutrient delivery—a cornerstone of modern, precision agriculture.