RU2196734C2 - Method of production of potassium chloride - Google Patents

Abstract

FIELD: inorganic chemistry, chemical technology. SUBSTANCE: method involves dissolving potassium chloride from potassium-containing raw in leaching solution, crystallization of end product from hot cleared solution saturated by potassium chloride in device with controlled vacuum-crystallization, isolation of crystallizer, its drying, heating and recovery of mother liquid for potassium chloride leaching. Moist concentrate with content of KCl > 92% is used as potassium-containing raw. Potassium chloride is dissolved in leaching solution obtained by addition of water to mother liquid up to content of sodium chloride in its 3-6%. Excessive mother liquid is used in preparing concentrate in device with controlled vacuum-crystallization and as washing out waters in isolation of moist concentrate. Invention ensures to obtain product with content of potassium chloride up to 98.8% and sodium chloride >1%. Invention is used for preparing potassium chloride with decreased sodium chloride and other impurities content from potassium-containing raw. EFFECT: improved method of production. 2 cl, 1 tbl

Description

 The invention relates to techniques for producing potassium chloride with a reduced content of sodium chloride from potassium-containing raw materials.

 A known method of purification of crystalline potassium chloride with a basic substance content of ≥97.5% of sodium chloride by treating the crystals with an aqueous leaching solution that contains a mixture of potassium and sodium chlorides, the solution must be saturated with KCl and unsaturated with NaCl - see application Great Britain 2009724 , cl. C 01 D 3/18, US priority 08.12.77-20.06.79, French application 2411158, cl. C 01 D 3/24, publ. 08/10/79 32, the application of Germany 2852925, cl. C 01 D 3/14, publ. 08/28/80 35.

 Our studies showed that when processing 98% of crystalline potassium chloride with a leach solution by known methods, it was possible to increase the content of the main substance in the target product only by 1.0-1.1%, and the final content of sodium chloride in the product practically did not decrease after 30- minute stirring the suspension. In the case of using 96% KCl as the potassium-containing raw material, the content of potassium chloride in the target product did not exceed 98.5%.

 A known method of producing potassium chloride from potassium-containing raw materials (sylvinites) with a sodium chloride content of> 1% is a prototype. See RF patent 2143999, cl. C 01 D 3/08, publ. 01/10/2000 1.

 The method includes dissolving potassium chloride from potassium-containing raw materials in a heated mother liquor, crystallizing the target product from a hot clarified salt-saturated solution in a controlled vacuum crystallization unit (RVCU) with crystallisate being separated off, dried, heated and the mother liquor returned to dissolution.

 The method allows to obtain a product with a potassium chloride content of up to 98.8% and sodium chloride> 1%. Depending on the water consumption at RVKU, at the request of consumers, a low-quality product can be obtained, for example, containing 96% potassium chloride.

 The known method does not allow to obtain the target product with a potassium chloride content> 99%.

 The objective of the invention is to obtain potassium chloride with a low content of sodium chloride and other impurities from potassium-containing raw materials.

 A positive effect is achieved by the fact that, in contrast to the known method, which includes dissolving potassium chloride from potassium-containing raw materials in a leach solution, crystallization of the target product from a hot clarified potassium chloride-saturated solution at RVCU with the crystallization precipitated and dried, heated and the mother liquor returned to leaching potassium chloride, according to the proposed method, as a potassium-containing raw material, a moist concentrate with a KCl content of> 92% is used, the dissolution of potassium chloride is carried out in leach present a solution prepared by adding water to the mother liquor until it contained 3.6% sodium chloride, and the excess mother liquor is used instead of water in the preparation of the concentrate.

 Excess mother liquor is used in RVKU and as wash water in the production of wet concentrate.

 The essence of the method is as follows: in contrast to the known method according to the proposed method, as a potassium-containing raw material, a wet concentrate with a content of KCl≥92% is used. The use of a concentrate instead of sylvinite ores in the process reduces the level of sodium chloride in the leach solution to 3-6%, eliminates the operations of separating clay-saline sludge and filtering halite and reduces the flow of circulating solutions.

 According to the proposed method, the dissolution of potassium chloride is carried out in a leach solution obtained by adding water to the mother liquor to the content of sodium chloride 3-6%.

 The level of sodium chloride in the leach solution is determined by the requirements of consumers to the content of potassium chloride in the marketable product. The table shows the dependence of the composition of the crystallizate in a controlled vacuum crystallization unit (in terms of dry matter) on the content of sodium chloride in the leach solution.

 From the above data it is seen that to meet the requirements of the main consumers (production of caustic potassium, potassium nitrate, etc.), where the KCl content should be 99.5%, it is necessary to maintain the level of sodium chloride in the leach solution at 4.5%, and for production potassium sulfate by the sulfuric acid method, where> 99% KCl is required, the NaCl content in the solution should be 6%. Moreover, the proposed method does not impose stringent requirements for the content of KCl (≥97.5%, as in analogues) in the concentrate, and 92% KCl can be used in the process.

 High quality crystallizate is achieved not only by the content in a given range of sodium chloride in the leach solution, but also by using at least a double-shell controlled crystallization unit with the content as in the prototype G: T in the bodies at the level of 4-9.

 According to the proposed method, the excess mother liquor is used instead of water in the preparation of KCl concentrate in the main production.

 The mother liquor contains less than 6% NaCl and is saturated with potassium chloride and unsaturated with NaCl.

 In this regard, such a solution is used instead of water at RVKU, as well as for washing concentrate in centrifuges and filters, on stuffing box seals of pumps and solvent shafts, etc. .

 The method is as follows.

A wet potassium chloride concentrate with a KCl content of ≥92% is dissolved in a leach solution at a temperature of 95-105 ^o C, obtained in the subsequent stages of the technological process. The solution is clarified from impurities and cooled in a controlled vacuum crystallization unit to a temperature of 30-45 ^o C. The resulting crystallizate suspension is separated by thickening and filtration. The solid phase is dried to obtain the target product, and the liquid phase, the mother liquor, is divided into two streams. Water is added to the main stream of the mother liquor to the content of sodium chloride in it to a level of 3-6%, after which it is heated and used as a leaching solution. Excess mother liquor is used instead of water when isolating the concentrate, for example, in a controlled vacuum crystallization unit, as a discharge in the filtration of the concentrate, and also as a locking liquid on stuffing box seals of pumps, mixer shafts, etc.

 As a result of the implementation of the method, a product is obtained with a KCl content of 99.1-99.8 in accordance with the current requirements of consumers.

Examples of the method
Example 1

1000 hours potassium chloride concentrate composition: KCl 92.16%, NaCl 3.75%, H ₂ O 4.00%, CaSO ₄ 0.03%, MgCl ₂ 0.06% was dissolved in 4446.3 parts by weight leaching solution composition: KCl - 18.67%, NaCl - 3.23%, MgCl ₂ - 0.05%, CaSO ₄ - 0.03%, the rest of the water at a temperature of 100 ^o C for 15 min, after which it is hot clarified the potassium chloride-saturated solution was cooled in a controlled crystallization unit at W: T in apparatuses ~ 9 to a temperature of 35 ^o C, the resulting crystallizate suspension was concentrated on a hydrocyclone, filtered by centrifuge and dried to obtain the product composition in terms of dry substance: KCl 99.75 , NaCl 0.24%, MgCl ₂ + CaSO ₄ 0.01% in an amount of 642.7 parts by weight In the mother liquor 3425.1 v.h. 1021.2 vol. water, heated and served as a leaching solution for the dissolution of potassium chloride. In the starting period, water is used as a leach solution; 746.8 including excess mother liquor composition: KCl 24.23%, NaCl 4.19%, MgCl ₂ 0.07%, CaSO ₄ 0.03%, was used instead of water in a controlled crystallization unit in the production of concentrate from sylvinite ores.

 Example 2

 To obtain the target product composition: KCl 99.8%, the NaCl content in the leach solution was maintained at 3%, and the potassium chloride crystallizate was washed in a centrifuge with water to displace the mother liquor in an amount of 6% by weight of the wet target product.

Claims (2)

 1. A method of producing potassium chloride, comprising dissolving potassium chloride from potassium-containing raw materials in a leach solution, crystallization of the target product from a hot clarified potassium chloride-saturated solution in a controlled vacuum crystallization unit with the release of crystallizate and drying, heating and returning the mother liquor to chloride leaching potassium, characterized in that as the potassium-containing raw materials use a moist concentrate with a KCl content> 92%, the dissolution of potassium chloride is carried out in a leach a solution obtained by adding water to the mother liquor to a sodium chloride content of 3-6%, and the excess mother liquor is used to obtain the concentrate.  2. The method according to p. 1, characterized in that the excess mother liquor is used in a controlled vacuum crystallization unit and as wash water for the separation of wet concentrate.

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