Method for preparing potassium sulfate by using polyhalite

Abstract

The invention provides a method for preparing potassium sulfate by using polyhalite. The method comprises the following steps of: (1) grinding ores: grinding the polyhalite till 90wt% of the polyhalite are over 150 meshes in size; (2) washing: washing with water to remove the sodium chloride in the polyhalite; (3) roasting: roasting washed minerals at a high temperature; (4) leaching: leaching to extract potassium in the polyhalite; (5) solid-liquid separation: subjecting the ore pulp obtained through the leaching step to solid-liquid separation so as to obtain a mother liquor containing K+; (6) conversion: evaporating the mother liquor, adding potassium chloride and a potassium mixed salt, preparing potassium sulfate through the conversion method, and filtering to obtain a potassium sulfate product and the mother liquor; (7) evaporation: continuously evaporating the mother liquor, filtering to obtain a potassium mixed salt, and returning the potassium mixed salt to the conversion process. According to the method, the potassium sulfate is prepared by using the polyhalite. The process is simple, wide in source of raw materials and low in cost, wherein the sodium chloride in the polyhalite can be effectively removed. Meanwhile, the leaching rate of K+ is high and the water consumption of leaching is reduced. The concentration of K+ in the leaching mother liquor is high, and the energy consumption of the subsequent evaporation and crystallization step is reduced. Obtained potassium sulfate products are high in purity.

Description

technical field [0001] The invention relates to a process for preparing potassium sulfate with potassium-containing minerals, in particular to a process for preparing potassium sulfate with high-sodium insoluble polyhalite. Background technique [0002] Polyhalite (K 2 SO 4 · MgSO 4 2CaSO 4 2H 2 O), is a kind of insoluble potassium ore, which is light gray or dark gray, widely distributed in sulfate-type potassium ore, and its theoretical potassium content (K 2 O) reaches 15.6%, which is an important potash resource. The polyhalite resources in the world are very rich, and the geological ages of its production are mainly concentrated in the Permian, Triassic and Tertiary. In terms of geological plane distribution, they are relatively concentrated in the ring belt of 25°-50° north latitude . Our country is just located in the regular ring zone where polyhalite resources are relatively rich in the world. It has been found that Sichuan, Hubei, Jiangsu, Shandong, Shanxi, ...

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Problems solved by technology

[0003] Due to the stable structure of polyhalite and poor water solubility, it needs certain treatment to utilize the potassium ions therein. Some literatures have reported the method of preparing potassium sulfate by utilizing polyhalite, for example, the Chinese patent application whose application number is 89101455.1 , disclose the method that utilizes same ion effect to extract potassium sulfate, magnesium sulfate, calcium sulfate from gypsum, polyhalite ore with 3.5% potassium sulfate solution, but this method needs to use 3.5% potassium sulfate as solvent, K + The utilization rate is low and the cost is high; US1956930 discloses a method for preparing potassium sulfate by reacting polyhalite and limestone in a sealed reactor, but the reaction conditions are harsh, the operation is complicated, and the risk is high; CN 103930371 A discloses that polyhalite and limestone are reacted to prepare potassium sulfate After the stone is calcined, the liquid that forms potassium sulfate and magnesium sulfate is first leached, and then the potassium-containing salts such as langbeinite are dissolved in the filtrate to increase the concentration of the solution. Part of the concentrated filtrate crystallizes to obtain potassium sulfate, and the other part precipitates to form anhydrous potassium langbeinite, decompose part of the obtained langbeinite to form langbeinite and return to the previous process to increase the concentration of the solution

The process of the method is longer, and the obtained langbeinite product needs to be redissolved, which wastes energy, and the market demand and value of the langbeinite product are relatively small