In recent years, with the practice of potassium salt production, the Chemical Industry Design and Research Institute of the Ministry of Chemical Industry has newly developed two new processes:
(1) The sodium bicarbonate of the K ⁺ , Na ⁺ , Mg ²⁺ /Cl ^- , H ₂ O quaternary system is pumped into the salt field by the sodium-halide sodium-controlled rate decomposition method, and the potassium-containing mineral light halide is crystallized. Before the stone, the brine with a greatly increased concentration (corresponding to the composition of the E-point of the phase diagram of the phase diagram) is sent to the processing plant and the old halogen (corresponding to the composition of the F-point of the phase diagram), and the NaCl is in the instant of halogenation. The brine is crystallized with very fine particles, and the potassium in the brine crystallizes out of the brine in the form of carnallite crystals, but the particles are coarser. Fine-grained sodium chloride is easily removed from the overflow, and the remainder is carnallite (low-sodium carnallite) containing a small amount of sodium chloride. To hyponatremia carnallite with water, the control carnallite decomposition rate, so that most of the magnesium chloride is dissolved in the water off, to obtain a final product of potassium chloride (KCl content up to 98%). If you need to improve the purity, you can clean it with fresh water.
In 1995, two 10,000-ton production units were built. Potassium chloride to produce quality products, intermediate products hyponatremia carnallite electrolyzed have been used as a raw material of magnesium metal. The process not only can obtain high-quality potassium chloride products, but also saves the salt field area, eliminates the recovery process of carnallite, shortens the production cycle, and the equipment can be fully localized.
(2) Dissolving and recrystallizing the salted carnallite to prepare potassium chloride: pumping the raw halogen into the sodium salt pool, and concentrating it to the carnallite by evaporation, then pumping it into the halogen pool, pumping the old halogen to the halogen, and halogenating After precipitation of carnallite, when a certain thickness is reached (30~50 cm), the halogenation is stopped, the brine in the pool is drained, and fresh brine is added to dissolve the carnallite. When it is close to saturation, it is pumped into the potassium salt pool for evaporation and concentration to precipitate KCl. The KCl is dehydrated and dried to obtain a potassium salt product; when the potassium salt pool brine reaches saturation, it is discharged back to the sodium salt pool for recycling production. The brine after the precipitation of the carnallite into the halogen pool is discharged into the second-stage carnallite pool, and the second-stage carnallite is concentrated by evaporation, a part of the terminal brine is discharged, and the other part is discharged into the old brine to adjust the brine and adjust the sodium salt pool brine. The carnallite precipitated in the second-stage carnallite pool, after draining the surface water, is added with fresh water for dissolution, and the dissolved solution is discharged back to the sodium salt pool for recycling production.
The process is an intermediate test scale and has been in operation for several years. The advantage is that it completely uses the salt field to complete the whole process of potassium chloride production, which saves the equipment of the beneficiation workshop; the disadvantage is that the water quality and production process of the brine are all carried out in the open air and are greatly affected by the climate.
3. Production process of Sichuan Quxian Nongle polyhalite mine The ore powder is added to the roaster and heated by roasting with flue gas. The dust is collected and collected by a first-stage cyclone separator, and then recycled by the water washing tower to vent the exhaust gas. The calcined clinker is added to the solution tank in which the circulating liquid has been discharged, and after 30 minutes, the slurry enters the compacting machine for filtration and washing, and the gypsum residue after washing and drying is sampled, and then washed with water, and the gypsum residue is naturally discharged. After dehydration, it is sent to the brick making workshop for brick making or discharging. The filtrate is pumped into the double-effect vacuum evaporator by vacuum filtration. After the specific gravity reaches the process requirements, it is placed in a crystallizing tank to cool the crystal. The product is packaged by centrifugation and then packaged. After crystallization, the mother liquor is driven into the double-effect evaporator. The new supplemental filtrate continues to evaporate and concentrate.
The process is a pilot research and development project of 2 000 t/a of high-concentration potassium and magnesium fertilizer made of polyhalite. Using a polyhalite having a K2O content of about 5%, the K ₂ O dissolution rate is over 90%.

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