RU2315713C2 - Method of separation of potassium chloride - Google Patents

Abstract

FIELD: separation of potassium chloride from sylvinite ores.

SUBSTANCE: proposed method includes dissolving of sylvinite, clarification of hot saturated lye, crystallization of product in presence of fluoro-reagents, thickening and filtration of suspension and treatment of non-clarified saturated lye. Clarified saturated lye is treated with hot solution saturated with potassium chloride before crystallization of product. Potassium chloride solution is obtained by dissolving off-grade floatation potassium chloride in water. Off-grade floatation potassium chloride is just cyclone dust, fine fractions of floatation product or filtered-off intermediate product used for forming sludge suspension which is clarified and is thickened after clarification and is directed for treatment of non-clarified saturated lye.

EFFECT: possibility of using off-grade floatation potassium chloride at halurgy plants without impairment of water balance in potassium chloride dissolving-crystallizing processes.

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Description

The invention relates to techniques for the isolation of potassium chloride from sylvinite ores by the method of dissolution-crystallization using substandard flotation potassium chloride in the technological cycle.

Widely known methods for the separation of potassium chloride from sylvinite ores, including its dissolution at elevated temperatures, the allocation of halite dump, clarification of the resulting saturated saturated liquor, crystallization of potassium chloride by cooling the liquor under vacuum, thickening the suspension and isolating the target product from the solution by heating the latter and feeding on dissolution (see M.E. Pozin. Technology of mineral salts, v.1., Chemistry, 1970, p.149-159, 167-168). In combined schemes, pulverized potassium chloride is added to the feedstock for dissolution, separated from the bulk of the product by sieving or air classification.

Known methods theoretically allow the use of substandard flotation finely dispersed potassium chloride in the galurgic factories, however, as we have shown when we submitted flotation dusty potassium chloride, for example, cyclone dust, intensive pricing was observed together with sylvinite ore in solvents, the foam clogged the elevator buckets and the withdrawal of halite from solvents ceased, which led to a halt of the apparatus.

A known method of extracting potassium chloride from potassium-sodium-containing raw materials, including leaching of raw materials at 100-105 about With, clarification of the suspension, evaporation of the clarified solution with separation of the separated sodium chloride from the solution, separation of the product from the solution by crystallization, separation of it from the mother liquor and returning the latter to leaching stage. In order to process the clay-salt suspension - waste flotation enrichment of sylvinite and to obtain high-quality potassium chloride, the mother liquor is treated with raw materials and heated (see AS USSR No. 806605, class CO1D 3/04, publ. 23.02.81, bul. No. 7).

The known method allows the use of flotation enrichment waste - clay-salt suspension containing potassium chloride, however, does not exclude the intensive pricing of the suspension in solvents due to the presence of flotation reagents in the suspension. In addition, the known method is complex and energy intensive, because involves the use of residue to maintain the water balance of the process.

A known method of separating potassium chloride from sylvinite, including its dissolution, clarification of the resulting saturated liquor, crystallization of the product, thickening the suspension and centrifugation in the presence of an amine with the separation of the product from the filtrate and the centrate. Before clarification, the saturated liquor is treated with a filtrate, and crystallization is carried out in the presence of a centrate (see AS USSR No. 833507, class C01D 3/08, publ. 30.05.81, bull. No. 20) - prototype.

The known method allows the allocation of potassium chloride from sylvinite by the method of dissolution-crystallization in the presence of a flotation reagent - amine, but it does not allow the use of substandard products of the flotation factory containing potassium chloride. In addition, the treatment of hot saturated liquor with the filtrate and feeding to the crystallization of a centrate having a temperature of 25-40 ° C contribute to lowering the temperature of the clarified liquor before the vacuum crystallization unit (VKU) with the release of halite.

To prevent crystallization of halite, it is necessary to introduce an excessive amount of condensate, otherwise it is impossible to obtain conditioned potassium chloride.

Entering an excess amount of condensate will lead to a violation of the water balance of the process and the loss of the target product.

The objective of the invention is to create the possibility of using substandard small-crystalline flotation potassium chloride at the galurgic enterprises without disturbing the water balance of the dissolution-crystallization processes.

The problem is solved in that, in contrast to the known method, including the dissolution of potassium chloride from sylvinite, clarification of the obtained hot saturated liquor, crystallization of the product in the presence of flotation reagents, thickening and filtering the suspension, processing of un clarified saturated liquor, according to the proposed method, processing of clarified saturated liquor before crystallization the product is a hot solution saturated with potassium chloride, obtained by dissolving in water substandard flotation chloris th potassium, which is a cyclone dust fines product or a flotation promproduky filtered to give a slurry suspension which was then clarified, and the slurry thickened slurry resulting from lightening direct handling saturated unclarified liquor.

The essence of the method is as follows.

In contrast to the known method, the treatment of hot clarified liquor before crystallization of the product is carried out with a potassium chloride-saturated solution obtained by dissolving substandard flotation potassium chloride, which is cyclone dust, small fractions of the flotation product or filtered industrial products.

Dissolution is carried out by heating to a temperature of 80-100 ° C to obtain a solution with the highest concentration in KCl and a temperature close to the temperature of the clarified liquor. Next, the solution is clarified with the addition of a flocculant, for example, polyacrylamide, to obtain a discharge that is practically free of sludge. It is possible to use additional control filtration, for example, on a filter press.

For the treatment of clarified liquor, a solution saturated with potassium chloride and unsaturated with sodium chloride is taken in an amount equivalent to the amount of water added to prevent crystallization of sodium chloride due to the formation of salt sludge (NaCl) during cooling of hot liquors of the galurgic factories, as well as to make up for water evaporating on a vacuum crystallization unit (VKU) during cooling of clarified liquor under vacuum, avoiding saturation of the liquid phase with sodium chloride.

Table 1 shows the dependence of the formation of salt sludge during cooling of hot liquors of galurgic factories using the example of Uralkali.

Table 1 The mass of salt sludge (t), salted out from 1000 tons of saturated liquor, when cooled by 1 ° C (the content of MgCl ₂ - 8 g, CaSO ₄ - 7 g per 1000 g of H ₂ O) Lye temperature, ° С The degree of saturation of the liquor phase liquor according to KC1 0.98 0.96 0.94 0.92 0.90 96 1,355 1,360 1,366 1,372 1,378 94 1,911 1,919 1,927 1,935 1,944 92 2,760 2,772 2,783 2,794 2,806 90 3.283-NaCl 0.240-KCl 3,296 3,309 3,323 3,336 88 3,787-NaCl 0,878-KCl 3,803 3,8181 3,833 3,849

The degree of saturation of the cooled solution after VKU on sodium chloride should be 0.97-0.99, which guarantees the receipt of KCl-conditioned product.

Processing clarified liquor is carried out in the receiving tank VKU, or directly in the buildings VKU.

Under these conditions, the water balance of the process is fully respected.

It is possible to enter an excess amount of a solution of potassium chloride, however, this leads to the production and discharge of excess mother liquors.

If there is a lack of substandard potassium chloride used to prepare the solution, water is introduced along with a saturated heated KCl solution at the VKU to prevent sodium chloride from contaminating the target product during vacuum crystallization.

Table 2 shows examples that characterize the expenditure rates for introducing water and a KCl solution to the VKU for the conditions of the Ural galurgic factory, calculated using the material balance equations. The above figures illustrate the proposed method, and they can vary with fluctuations in the dissolution temperature, degree of saturation according to KCl, hot saturated liquor and its sodium chloride content, sylvinite ore consumption, its chemical and particle size distribution and other parameters.

table 2 Entering water at the VKU depending on the flow rate of the cyclone dust solution for the ore flow rate of 234.5 and 250.0 t / h Cyclone dust solution consumption, t / h Water consumption at VKU, t / h Ore consumption 234.5 t / h Ore consumption 250 t / h 10 28.3 30.50 fifteen 25.88 28.07 twenty 23.45 25.65 25 21.02 23.22 thirty 18.6 20.79 35 16.17 18.37 40 13.74 15.94 45 11.32 13.51 fifty 8.89 11.09 55 6.46 8.66 60 4.04 6.23 65 1,61 3.81 70 -0.82 1.38

Note: Ore composition, mass fraction,%: 27.9 - KCl, 68.0 - NaCl, 0.14 - MgCl ₂ , 1.97 - CaSO ₄ , 1.7 - ho, 0.29 - H ₂ O.

The composition of cyclone dust, mass fraction,%: 92.17 - KCl, 5.69 - NaCl, 0.23-MgCl ₂ 1.10 - CaSO ₄ , 0.7-ho, 0.11 - H ₂ O.

Mass fraction of KCl in a solution of cyclone dust - 28%.

In contrast to the known method, the processing of saturated unclarified liquor is concentrated, for example, to W: T = 1-3, a slurry suspension obtained from substandard flotation potassium chloride by clarification of a hot saturated solution.

The processing of liquor is carried out either before filing it for clarification, or directly in the thickener. In this case, the potassium chloride contained in the slurry suspension passes into the liquid phase of the liquor without cooling it, and the insoluble compounds, clays and CaSO _4, together with the unlit liquor slurry are separated in the thickener.

Flotation reagents introduced with flotation potassium chloride do not accumulate in the technological cycle, because are sorbed by clay ore slurry and crystallizate at VKU.

As substandard flotation of potassium chloride, cyclone dust, fine fractions of the flotation product, filtered intermediate products obtained, for example, by hydroclassification of a suspension, are used. To reduce the sodium chloride content in the hot solution saturated with potassium chloride fed to the treatment, the KCl content in the substandard product is desirable to have more than 90%.

Thus, the implementation of the present invention allows to solve the problem: to use substandard small-crystalline flotation potassium chloride at the galurgic enterprises without disturbing the water balance of the dissolution-crystallization processes.

Examples of the method.

Example 1

500 parts by weight sylvinite ore containing 27.9% KCl was dissolved in 1197.7 parts by weight of a solvent solution to obtain 1328.8 wt.h. non-clarified saturated liquor composition, mass fraction,%: 19.76 - KCl, 17.32 - NaCl, 0.69 - MgCl ₂ , 0.78 - CaSO ₄ , 0.53 - ho, 60.92 - H ₂ O.

25.8 parts by weight cyclone dust containing 92.2% KCl was dissolved in 57.8 parts by weight of water at a temperature of 90 ° C and clarified on a thickener with the addition of a 0.1% solution of polyacrylamide. Received 53.6 parts by weight of clarified solution and a slurry suspension with W: T = 2, which was treated with un clarified saturated liquor. The resulting suspension was applied to a thickener with the addition of polyacrylamide and the clarified liquor was treated with a solution of potassium chloride, and then it was cooled on an ICU to a temperature of 25 ° C. The crystallizate suspension was thickened and the target product was separated on a filter, and the mother liquor was heated to 112 ° C and applied to dissolve sylvinite ore. Received 138.8 parts by weight product with a mass fraction of KCl of 98.6%.

Example 2

The method was carried out in accordance with example 1, but a flotation concentrate obtained by hydroclassification by the class of 1 mm flotation product and its filtration was taken to prepare a potassium chloride solution, and a saturated solution of flotation potassium chloride after separation of the slurry suspension from it was subjected to control filtration on a filter press before feeding a solution for processing a clarified saturated solution carried out in a thickener washing cup.

Example 3

The method was carried out in accordance with example 1, but fractions of a flotation product of less than 1 mm were used to prepare a potassium chloride solution.

Claims (1)

The method of separation of potassium chloride from sylvinite, including its dissolution, clarification of the obtained hot saturated liquor, crystallization of the product in the presence of flotation reagents, thickening and filtering the suspension, processing of un clarified saturated liquor, characterized in that the clarified saturated liquor is treated with a hot solution saturated with potassium chloride before crystallization of the product obtained by dissolving in water substandard flotation potassium chloride, which is a cyclone dust, fine fra cts of the flotation product or filtered intermediate products to obtain a slurry slurry, which is then clarified, and the condensed slurry slurry obtained by clarification is sent to the processing of unclarified saturated liquor.