Potassium Fertilizer Production: From Minerals to Food Security

Soluble Potash Ore: Mainstream Production Process Over 90% of the world\'s potassium fertilizer comes from soluble potash ores, such as sylvinite and carnallite. These ores are typically obtained through open-pit mining or underground solution mining. The mined ore needs to be crushed and screened to process the raw material to a particle size below 10 millimeters for subsequent dissolution and separation. In dissolution tanks, the ore is mixed with water or recycled mother liquor to form a mixed solution containing potassium chloride, sodium chloride, and other components. Flotation separation is a key technological step in potash fertilizer production. By adding special flotation agents, the difference in surface properties between potassium chloride and sodium chloride is utilized to cause potassium chloride particles to adhere to air bubbles and float to the liquid surface, thus achieving effective separation. This process can yield crude potash concentrate with a purity of 85%–90%. Subsequently, recrystallization further removes residual impurities such as sodium chloride and magnesium sulfate, increasing the product purity to over 95%. Conversion and Utilization of Insoluble Potassium Ores For insoluble potassium ores like potassium feldspar, or industrial by-products such as seawater and salt lake bittern, more complex extraction processes are required. Potassium feldspar usually needs to be crushed to a fineness of 200 mesh or above, and iron, titanium, and other impurities are removed through magnetic separation. The high-temperature roasting method is a commonly used conversion technique, where potassium feldspar is reacted with limestone and gypsum at 1100-1300°C to convert insoluble potassium into soluble potassium salts. Potassium extraction from seawater employs advanced solvent extraction technology, using special extractants like crown ethers to selectively extract potassium ions from seawater. These innovative technologies significantly expand the raw material sources for potassium fertilizer production, providing new possibilities for the sustainable development of the potassium fertilizer industry. Refining and Finished Product Preparation Regardless of the raw material route, subsequent drying and forming processes are crucial. Crystallized potassium chloride needs to undergo centrifugal dewatering and drying to control moisture below 2%. Depending on the application, the product can be processed into powder or granular form. Granular potassium fertilizer is prepared through extrusion granulation or disc granulation technology, with granule strength required to be no less than 20N to ensure integrity during transportation and application.