RU2551508C1 - Method for producing potassium chloride from sylvinite ore - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: producing potassium chloride is ensured by dissolving sylvinite ore in a mother solution and recovering halite refuse ore. Salt-based waste is recovered in thickening agents and hydrocyclones from solvent discharge. The solvent discharge is clarified from clay-salt waste. That is followed by crystallising potassium chloride in vacuum from the clarified solution, condensing a suspension of crystallise and filtering it. Spent liquor is heated and supplied back for dissolving. The condensed salt-based waste is mixed after the thickening agents with the heated spent liquor to L:S=2-4. The prepared suspension is divided on hydrocyclones in a near-mesh grain of 0.1-0.2 mm. The hydrocyclone discharge is directed to dissolve sylvinite ore. Hydrocyclone "sands" with L:S=0.6-1.5 are partially added to the condensed suspension of potassium chloride before filtering in an amount required to correct the KCl content in a dry product to meet the specifications. The residual "sands" are directed to the filter together with halite waste.

EFFECT: invention enables producing the end product with a lower KCl limit complying with the specifications.

2 tbl, 1 ex

Description

The invention relates to techniques for producing potassium chloride from sylvinite ores by the method of dissolution-crystallization.

Known methods for producing potassium chloride from sylvinite ores, including their dissolution in a heated working solution, clarification of the discharge of solvents - a hot solution saturated with potassium chloride and sodium chloride, from clay-salt sludge, crystallization of the target product from a clarified solution in vacuum crystallization plants (VKU ), separating the crystallizate from the mother liquor, heating the mother liquor and returning it to dissolve sylvinite ores - see, for example, M.E. Pozin, Technology of Mineral Salts, Part 1, Ed. “Chemistry”, L.O., 1970, p. 154-159; A.B. Zdanovsky, Galurgia, Publ. "Chemistry", L.O., 1972, S. 466-469; O.D. Kashkarov, I.D. Sokolov, Technology of potash fertilizers, Ed. “Chemistry”, L.O., 1978, p. 38-43.

In all known methods, the target product is obtained with a basic substance content of 96-99% KCl by normalizing the addition of water to a clarified saturated solution to prevent crystallization of sodium chloride together with crystallization of potassium chloride. The operation of potash plants showed that managing only the water balance of the crystallization process of potassium chloride does not allow to obtain the target product with a lower limit of KCl content in it: at the request of regulatory documentation - not less than 95%. Practically instead of 95% potassium chloride, 97.0-97.7% of the product is shipped, since in order to prevent the formation of defective products, the crystallization process is carried out when the degree of saturation of the solution in the VKU buildings with sodium chloride is less than 1 due to the introduction of excess water. This entails large economic losses for the producers of the target product due to the shipment instead of 95% KCl of the product with the content of 97.0-97.7% KCl, since there is no price premium per ton percent for potassium chloride.

Known methods for producing potassium chloride by changing the input stream of water depending on the change in the flow rate of the clarified saturated solution entering the crystallization, the content of potassium chloride, sodium chloride, magnesium chloride and the temperature of the solution in it - see RF patents No. 2406695, cl. C01D 3/04, G05D 27/00, publ. 12/20/2010, Bull. No. 35 and No. 2399587, class C01D 3/04, G05D 27/00, publ. 06/10/2010, Bull. No. 26.

Known methods allow you to control the water balance of the process of crystallization of potassium chloride at the VKU by ensuring the degree of saturation of the NaCl solution in the enclosures at a level of 1.0 when receiving 96% of the product and 0.9 when receiving 98% of the product. The introduction of known methods has allowed to reduce the water consumption at VKU, however, in order to avoid the formation of “marriage” of products, the content of potassium chloride in the crystallizate is maintained at the level of 96.5-97.0% KCl, since during the crystallization process the occlusion is observed in NaCl-saturated solutions - capture by crystals of the mother liquor, as a result of which, regardless of the degree of dilution with water of the solution cooled by the VKU, the NaCl content in the crystallizate ranges from 0.7-1.5%. This process depends on a number of difficultly controlled factors - the intensity of the solution boiling in the housings, W: T suspension, crystal topography, intergrowth sizes, etc.

A known method of producing potassium chloride from sylvinite ores, including their dissolution in a heated working mother liquor, the allocation of halite dump, the allocation of salt sludge from the solvent drain in thickeners and hydrocyclones, the clarification of the thickeners from clay-salt sludge, crystallization of potassium chloride under vacuum from a clarified solution , thickening the crystallizate suspension and filtering it to isolate a product with a content of 97-98.5% KCl, calculated on the dry matter, heating the working solution and returning it to the solution Vorenus - prototype - see Mining Journal, №8, 2007, ISS 0017-2278, www.rudmet.ru, Technology halurgy potash production in Russia and Belarus, with the.. 25-30.

The known method also does not allow to obtain the target product with a lower limit of the content of KCl in it in accordance with the regulatory documentation, which entails economic losses in production.

The objective of the invention is to create the possibility of reducing economic losses due to shipment instead of 95% potassium chloride product of high quality.

This goal is achieved in that, in contrast to the known method for producing potassium chloride from sylvinite ores, including their dissolution in a heated circulating mother liquor, the separation of halite dump, the separation of salt sludge from solvents in thickeners and hydrocyclones, clarification of the discharge of thickeners from clay-salt sludge, crystallization of potassium chloride under vacuum from a clarified solution, thickening the suspension of crystallizate and filtering it with the selection of the product, heating the circulating solution and returning it to and the dissolution, according to the proposed method, the condensed salt sludge after thickeners is mixed with a heated circulating mother liquor to W: T = 2-4, the resulting suspension is separated on hydrocyclones along the boundary grain of 0.1 ÷ 0.2 mm, the discharge of hydrocyclones is directed to the dissolution of sylvinite ores and the "sands" of hydrocyclones with W: T = 0.6-1.5 are partially added to the thickened suspension of potassium chloride before it is filtered in the amount necessary to adjust the KCl content in the dry product to the requirements of regulatory documentation, and the rest of the "sand"apravlyayut filtration together with the halite blade.

The essence of the method as a technical solution is as follows: in contrast to the known method for producing potassium chloride from sylvinite ores, including their dissolution in a heated reverse mother liquor, the allocation of halite dump, the allocation of salt sludge from solvents in thickeners and hydrocyclones, clarification of the discharge of thickeners from clay -salt sludge, crystallization of potassium chloride under vacuum from the clarified solution, thickening the suspension of crystallizate and filtering it with the release of the product, heating solution and return it to dissolution, according to the proposed method, the thickened saline sludge after thickeners is mixed with a heated circulating mother liquor to W: T = 2-4, the resulting suspension is separated on hydrocyclones along the boundary grain of 0.1 ÷ 0.2 mm, discharge of hydrocyclones sent to the dissolution of sylvinite ores, and the "sands" of hydrocyclones with W: T = 0.6-1.5 are partially added to the thickened suspension of potassium chloride before it is filtered in the amount necessary to adjust the KCl content in the dry product to the requirements of regulatory documentation, the remainder of the "sand" is sent to filtration together with the halite blade.

The experience of potash enterprises shows that it is possible to correct the content of potassium chloride in the target product by adding sodium chloride to it in two ways:

- by increasing the content of the mother liquor in the filtered crystallizate;

- adding crystalline sodium chloride to the finished product.

These two directions turned out to be ineffective and did not receive practical implementation for the following reasons: with an increase in the content of the mother liquor in the filtered crystallizate during drying of the product, sodium chloride formed on the surface of potassium chloride crystals is rubbed and blown out of the target product in the form of cyclone dust. When cyclone dust is returned to the finished product, crystal segregation by fractions is observed during storage and transportation of the product, as a result of which its chemical composition changes. In addition, the physicochemical properties of the product are deteriorating - its caking, dustiness, and energy consumption increases during drying of a wetter crystallizate.

The second direction requires the importation of an additional reagent - sodium chloride, its grinding to the size of the target product, the creation of a storage system and dosage of sodium chloride.

An analysis of the work of potash enterprises shows that salt of the halurgical production resulting from the dissolution of sylvinite ore can be used as such a reagent. Salt sludge is formed from small classes of sylvinite ore and when salting out sodium chloride from a heated circulating mother liquor when dissolving potassium chloride of sylvinite ore in it. In accordance with the prototype, salt sludge is classified in Brandes thickeners at an upward flow rate of 5-10 m / h, preferably 7 m / h. At such speeds, in a suspension thickened to L: T = 0.6-1.0, particles of sodium chloride are deposited mainly 0.06-0.7 mm in size, and fractions less than 0.06 mm in size, represented mainly by clay compounds, in Brandes plum to further clarify Dora's thickener. Thus, in accordance with the prototype, when the salt sludge is thickened, it is enriched in sodium chloride due to the removal of the main part of insoluble impurities from it.

According to the proposed method, in contrast to the known, thickened salt sludge is mixed with a heated working solution to W: T = 2-4. Due to the fact that the solution is unsaturated with sodium chloride and potassium chloride, when mixed with the solid phase, the smallest particles of sodium chloride and potassium chloride dissolve in it, and the ratio of liquid to solid in the suspension obtained by mixing to values of W: T = 2 -4 is optimal for hydroclassification of a suspension on cyclones. When mixing and hydroclassification, insoluble impurities (N.O.), represented by anhydrite (CaSO ₄ ) and clay compounds, are rubbed off from sodium chloride crystals. Such an operation makes it possible to transfer practically all small fractions of sodium chloride into the drain of hydrocyclones and to obtain a solid phase identical in particle size distribution to crystallization of potassium chloride after VCU by hydroclassification by the boundary grain of 0.1-0.2 mm in the “sands” of cyclones.

Depending on the chemical and granulometric composition of sylvinite ore supplied to dissolution, the amount of salt sludge and its composition can vary within wide limits. So, for example, when dissolving an ore having fractions of less than 1 mm no more than 50%, with an insoluble 4.9% and potassium chloride content of 31.2%, the proportion of insoluble in saline sludge reaches 6%, however, when hydroclassing in the “sands” of its cyclones the content is reduced by 2-3 times, that is, there is an enrichment of sodium chloride.

Table 1 shows the results of mixing the suspension with W: T = 0.6-1.0, obtained in the Brandes thickener, with the stock mother liquor heated to 100 ° C to W: T = 1.5-4.0, followed by hydroclassification of the mixture on a hydrocyclone along the boundary grain of 0.15 mm at a pressure at the inlet of the hydrocyclone of 1.2 kgf / cm ² .

Table 1 №№ pp Hydrocyclone Power "Sands" of hydrocyclones W: T Fractional composition of the solid phase,% W: T Fractional composition of the solid phase,% The chemical composition of the solid phase,% +0.7 mm -0.7 + 0.2 mm 0.2 mm +0.7 mm -0.7 + 0.2 mm 0.2 mm Kcl NaCl H.O. one 1,5 0.20 59.40 40,4 0.6 0.6 89.1 10,2 5.92 89.88 4.20 2 2.0 0.15 60.65 39.2 0.9 0.9 93.0 6.1 3.95 92.88 3.17 3 3.0 0.10 65.50 34,4 1,0 1,0 93.7 5.3 2.68 94.19 3.13 four 4.0 0.08 67.12 32.8 1,5 1,1 94.1 4.8 1.78 95.12 3.10

The table shows that as a result of mixing salt slurry, condensed to W: T = 0.6-1.0, with a hot working solution and hydroclassification of the mixture on cyclones in the “sands” of hydrocyclones, a solid phase is formed, which is mainly represented by sodium chloride, which has particle size distribution identical to the potassium chloride crystallisate after VKU before its filtration in centrifuges.

According to the proposed method, the discharge of hydrocyclones is directed to dissolution, and the "sands" of hydroclassification with W: T = 0.6-1.5 are partially added to the thickened suspension of potassium chloride before it is filtered in the amount necessary to adjust the KCl content in the dry product to the regulatory requirements documentation, and the rest of the “sand” is sent to the filtration together with the halite dump.

It is undesirable to increase the W: T of the “sands” of the hydrocyclone, since when working together the halite dump and salt slurry with a high content of hot liquid phase, the performance of vacuum filters worsen, and a decrease in W: T in the “sands” of less than 0.6 makes it difficult to work cyclones and leads to an increase in the content of insoluble in the solid phase.

According to regulatory documentation - see, for example, GOST 4568-95 - the content of potassium chloride in the finished product must be at least 95%. Table 2 shows the amount of solid phase in the “sands” of the hydrocyclone, which must be added to the crystallizate, depending on its composition in terms of dry matter, which is determined automatically.

table 2 №№ pp The content of potassium chloride in the product,% The consumption of the solid phase "sand" of hydrocyclones, t / t KCl one 96.0 0.010 2 96.5 0.016 3 97.0 0,021 four 97.5 0,026 5 98.0 0,032

A suspension of sodium chloride is fed into a thickened suspension of potassium chloride, depending on the consumption of potassium chloride and the content of the main substance in it. The solid content in the “sand” and the flow rate of the suspension is determined automatically, for example by a mass flow meter. The liquid phase, represented by a salt-saturated solution in the “sands” of the hydrocyclone, does not affect the composition of the finished product, since it is removed together with the filtrate obtained by separation of the crystallizate.

Table 2 does not take into account the content of potassium chloride in sodium chloride, since the increase in the content of KCl in the target product is insignificant and is within the accuracy of the measurements. The presence of insoluble compounds in the sodium chloride added is insignificant and does not lead to a deterioration in the quality of the products obtained.

Thus, the task is solved - the opportunity is created to reduce economic losses due to the shipment instead of 95% potassium chloride of a product of high quality by implementing the proposed technical solutions.

The method was carried out as follows: sylvinite ore was dissolved in a heated circulating mother liquor. The halite dump was separated by filtration on a vacuum filter, and the solvent discharge was sent to Brandes thickeners, where the solid phase was thickened to W: T = 0.6-1.0. The discharge of Brandes thickeners was clarified on clay Dorr thickeners from clay-saline sludge, the clarified solution was cooled in vacuo, the resulting suspension was concentrated and filtered by centrifuges. Condensed to W: T = 0.6-1.0, salt slurry was mixed with a heated circulating mother liquor to W: T = 2-4, the resulting suspension was separated on hydrocyclones along a boundary grain of 0.1-0.2 mm, the discharge of hydrocyclones was directed for the dissolution of sylvinite ore, and the “sands” of hydrocyclones with W: T = 0.6-1.5% were partially added to the thickened suspension of potassium chloride before it was filtered in the amount necessary to adjust the KCl content in the dry product to the requirements of regulatory documentation, and the rest of the “sand” was sent for filtration together with halite dump. Received the finished product with a potassium chloride content of 95.0-95.4%.

Examples of the method

Example 1

Sylvinite ore with a KCl content of 31.2% and 4.9% of insoluble compounds was dissolved in a heated reverse mother liquor. The halite dump was separated by filtration on a vacuum filter, and the solvent discharge was sent to Brandes thickeners, where the solid phase was thickened to W: T = 0.8. The discharge of Brandes thickeners was clarified on clay Dorr thickeners from clay-saline sludge, the clarified solution was cooled in vacuo, the resulting suspension was concentrated and filtered by centrifuges. Condensed to W: T = 0.8, salt slurry was mixed with a heated circulating mother liquor to W: T = 3, the resulting suspension was separated on hydrocyclones along a boundary grain of 0.2 mm, the discharge of hydrocyclones was sent to dissolve sylvinite ore, and the “sands” of hydrocyclones with W: T = 1 was partially added to the thickened suspension of potassium chloride before it was filtered in the amount necessary to adjust the KCl content in the dry product to the requirements of regulatory documentation, and the rest of the “sands” were sent for filtration together with a halite dump. At a current content of 97.5% KCl in the crystallizate, 0.026 t / t KCl of the solid phase of the “sand” of hydrocyclones or 0.052 t / t KCl of a suspension with W: T = 1 was added.

Got a finished product with a content of 95.1% KCl, which meets the requirements of GOST 4568-95 for this product.

Claims (1)

A method of producing potassium chloride from sylvinite ores, including their dissolution in a heated reverse mother liquor, separation of a halite dump, separation of salt sludge from solvent drains in thickeners and hydrocyclones, clarification of thickeners from clay-sludge sludge, crystallization of potassium chloride under vacuum from a clarified solution, thickening the crystallizate suspension and filtering it, heating the circulating solution and returning it to dissolution, characterized in that the thickened saline sludge after thickeners is mixed with a heated circulating mother liquor up to W: T = 2-4, the suspension obtained is separated on hydrocyclones by a boundary grain of 0.1 ÷ 0.2 mm, the discharge of hydrocyclones is sent to dissolve sylvinite ores, and the “sands” of hydrocyclones with W: T = 0 , 6-1.5 is partially added to the thickened suspension of potassium chloride before it is filtered in the amount necessary to adjust the KCl content in the dry product to the requirements of regulatory documentation, and the rest of the “sand” is sent for filtration together with a halite dump.