A kind of method utilizing potassium mixed salt to prepare potassium chloride

Abstract

The invention discloses a method for preparing potassium chloride from potassium mixed salt. The method comprises the steps that the potassium mixed salt is dissolved in water, solid-liquid separation is carried out, and a potassium mixed salt solution is obtained; a first-section nanofiltration step is carried out, wherein a nanofiltration membrane system is adopted for carrying out first-section nanofiltration treatment on the potassium mixed salt solution, first-section concentrated water and first-section produced water are obtained, the nanofiltration system comprises a first nanofiltration membrane assembly, a first concentrated water box and a first produced water box, and the first concentrated water box and the first produced water box are connected to the first nanofiltration membrane assembly; the first-section concentrated water is stored in the first concentrated water box, and the first-section produced water is stored in the first produced water box; the first-section produced water is subjected to evaporative crystallization, and sylvinite ore is obtained; the sylvinite ore is subjected to flash melting crystallization, and potassium chloride is obtained. The novel method is used for producing potassium chloride from the potassium mixed salt and has the advantages of being simple in process, high in product purity, large in particle and high in yield.

Description

technical field [0001] The invention belongs to the technical field of inorganic salt preparation, and in particular relates to a method for preparing potassium chloride by using potassium mixed salt. Background technique [0002] Potassium is one of the three major nutritional elements (nitrogen, phosphorus, potassium) necessary for the growth of crops, among which potassium chloride is the most important type of potassium fertilizer, accounting for more than 90% of the total amount of potassium fertilizer. my country is a country with serious soil potassium deficiency. With the continuous increase of crop yield and nitrogen and phosphorus fertilizer application, the amount of potassium removed by crops from the soil is gradually increasing. The amount of potassium returned to the soil cannot make up for the removal of crops from the soil. The depletion of potassium in the soil is becoming more and more serious, and the area of ​​potassium deficiency is gradually expanding, ...

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Problems solved by technology

[0011] But there are following shortcoming in above-mentioned two kinds of existing schemes: (1) when adopting direct flotation method, in the flotation process of potassium mixed salt, except potassium chloride, other potassium-containing minerals such as sylvite still use potassium salt The existence form of langbeinite enters the concentrate foam, and the separation of potassium chloride and magnesium sulfate cannot be realized, while langbeinite still stays in the tailings, thereby reducing the flotation yield of stearylamine; (2) old brine The conversion can realize the preparation of potassium chloride products from potassium mixed salt, but because it must be carried out under high temperature conditions, the conditions are harsh, the energy consumption is high, and the operation risk is high, and the addition ratio of potassium mixed salt ore and old brine must be controlled. Due to the high content of sodium chloride and magnesium sulfate impurities, they are easily mixed into crystalline carnallite, which affects the grade of potassium chloride; although the old brine can also undergo conversion reaction with potassium mixed salt ore under normal temperature conditions, the conversion efficiency is very low, and not feasible

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