The potash ores are the main raw material used to produce potash and compound fertilizers and other chemicals. The potash ore generally consists of sylvite (KCl), halite (NaCl – the rock forming mineral) containing the inclusions of carnalite, anhydrite and silicate and carbonate (insoluble residue).
The processing of potash ores by hot leaching with further crystallization of potash salt from saturated salt brines (halurgical method) began in XIX century in Strasburg.
The primary methods of potash ore processing are flotation (mechanical method) and hot leaching (chemical method). JSC Belaruskali uses both methods: Productions Units 1, 2 and 3 process the potash ore by flotation and Production Unit 4 uses the hot leaching method.
Flotation:
The processing of ore by flotation is based on the different capacity of sylvite and halite surface to be moistened with water through the addition of specifically acting chemicals – surfactants – and further formation of the froth containing the valuable component.
The production process includes the following stages:
• Ore crushing and pre-screening;
• Ore milling and pre-sizing;
• Mechanical and flotation desliming of ore;
• Sylvite flotation;
• NaCl leaching from the floatation concentrate;
• Hydro-thickening and dehydration of tailings;
• Hydro-sizing and dehydration of concentrate;
• Concentrate drying;
• Preparation of chemicals;
• Granulation of potassium chloride;
• Granules refining;
• Finished product loading;
• Waste stockpiling.
The floatation method of ore processing is used to manufacture the reddish-pink standard and granular potassium chloride. The KCl mass fraction in the product is 95-96%. The recovery of the valuable component when using the flotation method is 85.5-87.2%.
Hot leaching method:
The hot leaching method of ore processing is based on the physicochemical properties of NaCl-KCl-H2O system. The main principle of this method is the different temperature-depending degree of solubility of the mineral components – sylvite and halite: the high solubility of potassium chloride from ore by cycling solution at 115°C and the further crystallization of the valuable component on cooling.
The production process includes the following stages:
• Ore crushing and prescreening;
• Leach heating;
• Ore dissolution;
• Filtration of halite tailings;
• Clarification of saturated leach;
• Crystallization of potassium chloride;
• Thickening and centrifugation of potassium chloride slurry;
• Potassium chloride drying;
• Granulation of potassium chloride;
• Stockpiling, storage and loading;
• Recycled water cooling;
• Preparation of chemicals;
• Waste stockpiling.
The hot leaching method is used to produce the white fine-crystalline and granular potassium chloride. The coarse crystalline product (if necessary) can be painted reddish-pink. The KCl mass fraction in the product is 96-99%. The recovery of the valuable component of fertilizers produced when using the hot leaching method is 88-89%.