Method for obtaining potassium chloride from calcium chloride-type brines

Abstract

The present invention relates to the field of chemical technology for recovering potassium, sodium, magnesium and calcium compounds from natural mineral brines, and more particularly to a method for obtaining potassium chloride from a calcium chloride-type natural brine feedstock that is also rich in sodium and magnesium. The proposed method for recovering potassium chloride does not require the use of additional reagents and enables maximal recovery of potassium from brines, while also making it possible to obtain additional by-products in the form of sodium chloride, magnesium chloride and calcium chloride. The method allows the efficient use of a new source of potassium salts, specifically calcium chloride-type brines, and makes it possible to reduce costs related to the evaporation and cooling of the brines during the potassium chloride recovery process, as well as to obtain a target product having a mass fraction of KCl of more than 95%.

Description

[0001] METHOD OF OBTAINING POTASSIUM CHLORIDE FROM CALCIUM-CHLORIDE BRINES

[0002] Field of technology.

[0003] The invention relates to the field of chemical technology for extracting potassium, sodium, magnesium, and calcium compounds from natural mineralized brines and can be used to obtain potassium chloride, which is used in agriculture as an independent potassium fertilizer, for the production of complex and mixed fertilizers, in the production of leather substitutes, synthetic rubbers, and in the food and pharmaceutical industries.

[0004] State of the art.

[0005] In world practice, a method for separating potassium chloride and sodium chloride from a heated solution of these salts is known according to patent RU2448046C2 "Method for separating potassium chloride and sodium chloride", which contains the stages of obtaining a heated solution containing potassium chloride and sodium chloride, passing the solution through a waterproofing membrane and removing water from the solution, thereby increasing the concentration of sodium chloride in the solution to a level exceeding the solubility of the salt at the temperature of the solution, and precipitating sodium chloride from the solution, separating the precipitated sodium chloride from the solution, cooling the solution and thereby reducing the solubility of potassium chloride to a level below the concentration of potassium chloride in the solution, precipitating potassium chloride from the solution, and separating potassium chloride from the solution ensuring the extraction of at least 50-60% of potassium chloride.

[0006] The disadvantage of this method is the use of membrane distillation to concentrate the brine, which negatively affects productivity, the lack of washing of the product crystals, and insufficiently complete extraction of KCl from the brine.

[0007] A method for producing potassium chloride is known in world practice according to patent US3642454A "Production of potassium chloride from carnallite salts", in this method potassium chloride is obtained from carnallite salts consisting mainly of carnallite (KCl-MgCE ^HiO) and halite (NaCl), which are isolated as a result of evaporation of brines in the sun, the brines contain sodium, potassium, magnesium ions, chlorine and sulfate as main components, while the ratio of KCl to NaCl in carnallite salt is from about 1 part by weight of KCl to about 1.5 to 2 parts by weight of sodium chloride. Carnallite salt is brought into contact with water and a solution rich in magnesium is obtained, while mainly sodium chloride and potassium chloride remain as a solid phase, the solid phase is separated (first solid phase). The magnesium-rich solution is evaporated to produce carnallite salt.The first solid phase is dissolved in water and then the solution is evaporated with precipitation of potassium chloride and obtaining a liquid phase rich in sodium chloride (second liquid phase). The precipitated potassium chloride is separated from said second liquid phase. The second liquid phase is evaporated with obtaining a salt solution and precipitation of a solid mixture of potassium and sodium chlorides; said brine is separated from said solid mixture; said salt solution is evaporated with obtaining a carnallite salt consisting mainly of carnallite and halite.

[0008] The disadvantage of this method is the use of solar energy to evaporate brines, repeated use of evaporation, which negatively affects productivity, and incomplete extraction of KC1 from the brine.

[0009] A method for obtaining potassium chloride from brine solutions is known according to patent CA1103894A "Production of potassium chloride by pond crystallization method", in which potassium chloride is obtained from brine solutions containing potassium chloride, sodium chloride and an insignificant amount of salts of other metals, in which said solution is extracted from an underground cavity in a potash ore deposit and sent to an oil refinery, where potassium chloride crystals are obtained from the extracted brine by introducing a brine solution containing potassium chloride, sodium chloride and an insignificant amount of other metal salts into a crystallizer pool and co-precipitating crystals of said salts in it, then heating the suspension of salt crystals and brine using solar energy to dissolve the potassium chloride crystals present in said suspension, obtaining a brine enriched with potassium chloride, separating the crystals of sodium chloride and other metal salts from the brine,enriched with potassium chloride, the precipitation of potassium chloride crystals is carried out from a brine enriched with potassium chloride.

[0010] The disadvantage of this method is the use of solar energy for evaporation of brines, which negatively affects productivity, large areas of the crystallizer pool, lack of washing of product crystals, and insufficiently complete extraction of KC1 from the brine.

[0011] A method is known according to patent US3528767A "Production of potassium chloride, potassium sulfate and sodium sulfate from brines and the like containing potassium, chloride and sulfate", which includes obtaining at least one salt selected from the group consisting of potassium chloride, potassium sulfate and sodium sulfate, from raw salts obtained from brines containing sodium, potassium, magnesium, chloride and sulfate ions, which includes initially removing the main content of sodium chloride from said brine by evaporation and crystallization, then further evaporating the remaining brine to crystallize from it a crude mixture of salts containing at least 20% by weight of carnallite and kainite, as well as other salts, including hydrates of sodium chloride and magnesium sulfate, then reacting said crude salt mixture to obtain from it at least one of potassium chloride, potassium sulfate and sodium sulfate.

[0012] The disadvantage of this method is the multi-stage process, the use of solar energy for evaporation of brines, which negatively affects productivity, the lack of washing of product crystals, and insufficiently complete extraction of potassium compounds from the brine.

[0013] A method for extracting potassium chloride from brine is known according to patent US1432796A "Method for extracting potassium chloride from brine", in which potassium chloride is extracted from a brine containing chlorides of potassium, sodium and magnesium, in a first step an unrefined crystalline material is obtained by solar evaporation, richer in potassium than the brine, then said unrefined crystalline material is washed with a solution of potassium chloride at a temperature close to atmospheric temperature in order to thereby dissolve the magnesium chloride in the crystals and displace from the solvent solution a portion of the potassium chloride contained therein by replacing the potassium chloride in the solution with magnesium chloride in the solid state, the obtained washed crystalline material is separated from the liquid, the potassium chloride contained in said crystalline material is dissolved with a hot solvent to form a hot saturated solution of potassium chloride containing such a small proportion of magnesium chloride,that upon cooling, potassium chloride precipitates without precipitation of sodium chloride, separating said potassium-saturated solution from undissolved solids while hot, cooling said potassium-saturated solution and precipitating potassium chloride, separating potassium chloride from the cooled mother liquor. This patent was selected as a prototype.

[0014] The disadvantage of this method is that it cannot be used to extract potassium chloride from calcium chloride brines, and the use of solar energy to evaporate brines has a negative impact on productivity.

[0015] The essence of the invention.

[0016] The aim of the present invention is to maximize the extraction of potassium chloride from natural mineralized brines containing calcium, obtaining a target product with a mass fraction of KCl greater than 95%.

[0017] The proposed method of potassium chloride extraction allows for the efficient use of a new source of potassium salts - chloride-calcium brines. Such brines are widely distributed within the Siberian platform. Hydromineral raw materials of the chloride-calcium type are also enriched with sodium and magnesium. The proposed method of potassium chloride extraction does not require the introduction of additional reagents, promotes maximum extraction of potassium from brines, and also allows for the additional production of by-products in the form of sodium chloride, magnesium chloride, and calcium chloride.

[0018] The technical result of implementing the method is an increase in the yield of the target product, the use of calcium chloride brines as the starting material, a reduction in costs associated with evaporation and cooling, an increase in the purity of the final product, and the isolation of by-products for their subsequent use.

[0019] The technical result is achieved in that the proposed method involves extracting potassium chloride from a brine containing chlorides of potassium, sodium, magnesium, and calcium, which involves obtaining an unrefined crystalline material, washing the said unrefined crystalline material to dissolve magnesium chloride, separating the washed crystalline material from the liquid, dissolving the potassium chloride contained in the said crystalline material using a hot solvent to form a hot saturated solution of potassium chloride, separating the said potassium-saturated solution from solids while hot, cooling the said potassium-saturated solution, and separating the potassium chloride from the cooled mother liquor, wherein: 1) the unrefined crystalline material is obtained by concentrating the initial brine to a concentration of KCl in the range of 1.6-5.0 wt.%, NaCl in the range of 1.3-18.5 wt.%, MgCb in the range of 5.1-7.0 wt.%., CaCl in the range of 24.5-47.2% by weight, the concentrated brine is cooled to a temperature of 20-35 °C with the precipitation of crystalline material in the form of carnallite, calcium chloride, sodium chloride and potassium chloride, the crystalline material is separated from the mother liquor;

[0020] 2) before washing the crystalline material with the dissolution of magnesium chloride, wash the crystalline material from calcium chloride by displacement on a belt vacuum filter or centrifuge with a ratio of L:S = 0.3-0.7:1;

[0021] 3) washing of the crystalline material from magnesium chloride is carried out by diluting the crystalline material in a reactor with a solvent at a temperature of 10-25 °C;

[0022] 4) separation of the crystalline material from the liquid after washing from magnesium chloride is carried out by unloading the pulp from the reactor and filtering it;

[0023] 5) dissolution of potassium chloride contained in the said crystalline material is carried out in a hot solvent at a temperature of 90-110 °C;

[0024] 6) cooling of the potassium-saturated solution is carried out to a temperature of 20-35 °C with evaporation of some of the water;

[0025] 7) the potassium chloride crystals separated from the cooled mother liquor are washed with fresh water and filtered;

[0026] 8) water or a solution of potassium chloride or sodium chloride can be used as a solvent;

[0027] 9) washing of the crystalline material from magnesium chloride can be carried out for 1-20 minutes;

[0028] 10) the solution obtained after washing the crystalline material from magnesium chloride can be used to obtain carnallite, bischofite, or magnesium oxide, or magnesium by electrolysis.

[0029] 11) the filtrate obtained after washing from magnesium chloride can be sent to the stage of evaporation of the original brine.

[0030] 12) The mother liquor obtained after crystallization of potassium chloride from a potassium-saturated solution can be sent to the stage of hot dissolution of potassium chloride as a solvent. 13) The solution obtained after the final washing and filtration of potassium chloride crystals can be sent to the stage of washing the crystalline material from magnesium chloride.

[0031] 14) The filtrate obtained at the stage of washing the crystalline material from calcium chloride can be used as raw material for anti-icing additives or plugging solutions.

[0032] The technical result is achieved in that the concentration of the initial brine to the specified concentrations and cooling of the concentrate to a temperature of 20-35 °C ensures the most complete extraction of potassium chloride when using calcium chloride brine as the initial raw material with minimal costs for heating the brine during evaporation and cooling the concentrate, i.e. such a mode is optimal for the purposes of the invention.

[0033] The technical result is achieved by the fact that preliminary washing of the crystalline material from calcium chloride by the displacement method on a belt vacuum filter or a centrifuge with a ratio of L:S = 0.3-0.7:1 ensures a sufficient degree of calcium chloride removal to ensure the purity of the final product with minimal losses of potassium chloride during washing.

[0034] The technical result is achieved by the fact that washing the crystalline material from magnesium chloride by diluting the crystalline material in a reactor with a solvent at a temperature of 10-25 °C ensures the removal of magnesium chloride and calcium chloride residues with minimal losses of potassium chloride during washing. In this case, washing for a period of time from 1 to 20 minutes is preferable.

[0035] The technical result is achieved by the fact that dissolution of potassium chloride contained in the said crystalline material with a hot solvent at a temperature of 90-110 °C ensures the most complete dissolution, which has a positive effect on the degree of product extraction.

[0036] The technical result is achieved by the fact that cooling a solution saturated with potassium to a temperature of 20-35 °C with evaporation of part of the water ensures the most complete precipitation of potassium chloride crystals with insignificant precipitation of impurities.

[0037] The technical result is achieved by the fact that washing the potassium chloride crystals separated from the cooled mother liquor with fresh water and subsequent filtration ensures an increase in the purity of the final product.

[0038] The wash solution obtained after washing the crystalline material from magnesium chloride can be used to obtain carnallite, bischofite, or magnesium oxide, or magnesium by electrolysis, which allows obtaining by-products of production.

[0039] Carnallite obtained by evaporating the wash solution after washing the crystalline material from magnesium chloride can be sent back to the stage of washing the crystalline material from magnesium chloride in order to reduce the loss of potassium chloride.

[0040] The filtrate obtained after washing off magnesium chloride can be sent to the stage of evaporation of the original brine, which increases the yield of the by-product in the form of carnallite and reduces the loss of potassium chloride.

[0041] The mother liquor obtained after crystallization of potassium chloride from a potassium-saturated solution can be sent to the stage of hot dissolution of potassium chloride as a solvent, which allows saving resources for water treatment and reduces the loss of potassium chloride.

[0042] The mother liquor obtained after the final washing and filtration of potassium chloride crystals can be sent to the stage of washing the crystalline material from magnesium chloride, which reduces the loss of potassium chloride, returning it to the working cycle.

[0043] Below are examples of implementation of the method according to the present invention.

[0044] Example 1.

[0045] The raw material for obtaining potassium chloride was calcium chloride brine, which was evaporated to a concentration of KCl 1.6% by weight, NaCl 1.3% by weight, MgCh 5.1% by weight, CaCh 24.5% by weight. Then the concentrate was cooled to a temperature of 20 °C to isolate a crystalline product (primary crystallizate) in the form of a mixture of carnallite (KCl MgC12-6H2O), calcium chloride, sodium chloride and potassium chloride. The yield of the primary crystallizate was 7.81%. To remove calcium chloride, the resulting crystalline suspension was sent to the stage of primary washing with water by displacement on a belt vacuum filter with a ratio of L:S = 0.3: 1. The yield of the crystallizate after the primary washing was 75.3%. The residual content of calcium chloride in the crystallizate did not exceed 3.9%. After the primary washing stage, the crystallizate was sent to the cold decomposition stage, where it was washed for 1 minute by dilution in a reactor from magnesium chloride and calcium chloride with water at a temperature of 10°C.The resulting suspension was separated on a filter. The wet precipitate after filtration was sent to the hot dissolution stage, where it was treated with hot water at a temperature of 100°C, the precipitate remaining after dissolution of potassium chloride was separated from the solution saturated with potassium chloride on a vacuum filter), the potassium chloride solution saturated at 100°C was cooled to 20°C to obtain a secondary crystalline product with a KCl concentration of at least 95%. The resulting crystalline product KCl was washed with fresh water in an amount of 10% of the mass of the wet product, obtaining a crystallizate with a KCl concentration of > 98%.

[0046] Example 2.

[0047] The process of potassium chloride extraction was carried out similarly to example No. 1, with the difference that the initial brine was evaporated to obtain a concentrate to a concentration of KCl 3.3% by weight, NaCl 10.2% by weight, MgCh 6.1% by weight, CaCl 31.2% by weight. Then the concentrate was cooled to a temperature of 30 °C with the isolation of a crystalline product (primary crystallisate). The yield of the primary crystallisate was 9.69%. The yield of the crystallisate after the primary washing was 69.9%. The residual content of calcium chloride in the crystallisate did not exceed 3.5%. After the primary washing stage, the crystallisate was sent to the cold decomposition stage, where it was washed for 10 minutes by the dilution method at a ratio of L:S = 0.5:1 in a reactor from magnesium chloride and calcium chloride with a solution of potassium chloride at a temperature of 20 °C. The resulting suspension was separated on a filter. Wet sediment after filtration with the content of KCl - 35.07% by weight, NaCl - 55.94% by weight.and a yield of 44.3% was sent to the hot dissolution stage, where at a temperature of 90°C it was treated with a hot mother liquor in a mother liquor:crystallize ratio of 2.1:1 until saturated with potassium chloride. The halite waste remaining after leaching of potassium chloride in an amount of 59.1% of the washed sediment weight was separated from the solution saturated with potassium chloride on a vacuum filter. The potassium chloride solution saturated at 90°C was cooled to 30°C with evaporation of 8.5% of the water by weight of the solution and obtaining a secondary crystalline product with a KCl concentration of at least 95% and a yield of 37% of the washed crystallizate weight. The mother liquor with an insignificant KCl content from the crystallization stage was sent to the hot dissolution stage for leaching of potassium chloride from the primary crystallizate. The obtained crystalline product KC1 was washed with distilled water in an amount of 5% of the mass of the wet product, obtaining a crystallizate with a concentration of KC1> 98%.The weak solution of potassium chloride from the washing stage was sent to the cold decomposition stage, where the potassium chloride from the solution passed back into the crystalline phase.

[0048] Example 3.

[0049] The process of potassium chloride extraction was carried out similarly to example No. 1, with the difference that the brine was evaporated to obtain a concentrate to a concentration of KS1 4.3% by weight, NaCl 15.1% by weight, MgCh 6.5% by weight, CaCl 41.4% by weight. The yield of the primary crystallizate was 11.95%. After carrying out the remaining operations, a secondary crystalline product with a concentration of KS1 of at least 95% was obtained. After washing, a crystallizate with a concentration of KS1> 98% was obtained.

[0050] Example 4.

[0051] The process of potassium chloride extraction was carried out similarly to example No. 1, with the difference that the brine was evaporated to obtain a concentrate to a concentration of KCl of 5.0% by weight, NaCl 18.5% by weight, MgCb 7.0% by weight, CaCh 47.2% by weight. The yield of the primary crystallizate was 12.1%. After carrying out the remaining operations, a secondary crystalline product with a KCl concentration of at least 95% was obtained. After washing, a crystallizate with a KCl concentration of > 98% was obtained.

[0052] Example 5.

[0053] The process of extracting potassium chloride was carried out similarly to example No. 2, with the difference that hot dissolution was carried out at a temperature of 110°C.

[0054] Example 6.

[0055] The process of potassium chloride extraction was carried out similarly to Example No. 1, with the difference that the concentrate was cooled to a temperature of 35°C with the separation of the crystalline product (primary crystallizate). The yield of the primary crystallizate was 9.45%. To remove calcium chloride, the resulting crystalline suspension was sent to the stage of primary washing with water on a belt vacuum filter with a ratio of L:S = 0.7:1. The yield of the crystallizate after the primary washing was 68.12%. The residual content of calcium chloride in the crystallizate did not exceed 2.8%. After the primary washing stage, the crystallizate was sent to the cold decomposition stage, where it was washed for 20 minutes by dilution in a reactor from magnesium chloride and calcium chloride with water at a temperature of 25°C. The resulting suspension was separated on the filter. A solution of potassium chloride saturated at 100°C was cooled to 35°C to obtain a secondary crystalline product with a KCl concentration of at least 95%. After washing, a crystallisate with a KCl concentration of > 98% was obtained.

[0056] Example 7.

[0057] The process of potassium chloride extraction was carried out similarly to example No. 1, with the difference that at the cold decomposition stage a solution of potassium chloride was used as a solvent. After carrying out the remaining operations, a secondary crystalline product with a concentration of KCl of at least 95% was obtained. After washing, a crystallisate with a concentration of KCl> 98% was obtained.

[0058] Example 8.

[0059] The process of potassium chloride extraction was carried out similarly to example No. 1, with the difference that at the stage of cold decomposition and hot dissolution, a sodium chloride solution was used as a solvent. After carrying out the remaining operations, a secondary crystalline product with a KCl concentration of at least 95% was obtained. After washing, a crystallisate with a KCl concentration of > 98% was obtained.

[0060] Example 9.

[0061] The process of extracting potassium chloride was carried out similarly to example No. 1, with the difference that the solution obtained after washing the crystalline material from magnesium chloride was sent to obtain carnallite, bischofite, magnesium oxide, or magnesium by electrolysis.

[0062] Example 10.

[0063] The process of extracting potassium chloride was carried out similarly to example No. 1, with the difference that the filtrate obtained after washing off magnesium chloride was sent to the stage of evaporation of the original brine.

[0064] Example 11.

[0065] The process of extracting potassium chloride was carried out similarly to example No. 1, with the difference that the filtrate obtained at the stage of washing the crystalline material from calcium chloride was used as raw material for an anti-icing additive and plugging solutions.

[0066] Example 12.

[0067] The process of extracting potassium chloride was carried out similarly to example No. 1, with the difference that a centrifuge was used to wash the crystalline material from calcium chloride.

[0068] Sources of information used:

[0069] 1. Russian Federation Patent No. 2448046. SOJ 3 / 08, BOID 9 / 02, BOID 61 / 00. Method for separating potassium chloride and sodium chloride / Shaw Raymond Walter, Batterham Robin John. Cl. 06.03.2008, published 20.04.2011.

[0070] 2. US Patent US3642454A. C01D3 / 08. Production of potassium chloride from carnallite salts / Alfred F. Nylander. Cl. 27.06.1968, published 15.02.1972.

[0071] 3. Canadian Patent CA1103894A. C01D3 / 06. Production of Potassium Chloride by Pond Crystallization / Donald H. Gesen. Cl. 26.11.1979, publ. 30.06.1981.

[0072] 4. US Patent US3528767A. C01D3 / 06. Production of potassium chloride, potassium sulfate and sodium sulfate from brines, etc., containing potassium, chloride and sulfate / Donald E. Garrett. Claimed 16.03.1966, published 15.09.1970.

[0073] 5. US Patent US1432796A. C01D3 / 06. Method for extracting potassium chloride from brine / Joseph L. Silsbee. Claimed 12.04.1920, published 24.10.1922.

Claims

CLAUSES OF THE INVENTION 1. A method for extracting potassium chloride from a brine containing chlorides of potassium, sodium, magnesium and calcium, characterized in that it includes obtaining a crude crystalline material, washing said crude crystalline material to dissolve magnesium chloride, separating the washed crystalline material from a liquid, dissolving potassium chloride contained in said crystalline material using a hot solvent to form a hot saturated solution of potassium chloride, separating said potassium-saturated solution from undissolved solids while hot, cooling said potassium-saturated solution and separating potassium chloride from the cooled mother liquor, wherein obtaining the crude crystalline material is carried out by concentrating the original brine to a concentration of KCl in the range of 1.6-5.0% by weight, NaCl in the range of 1.3-18.5% by weight, MgCE in the range of 5.1-7.0% by weight, CaCE in the range 24.5-47.2% May,the concentrated brine is cooled to a temperature of 20-35 °C with the precipitation of crystalline material in the form of carnallite, calcium chloride, sodium chloride and potassium chloride, the crystalline material is separated from the mother liquor; before washing the crystalline material with the dissolution of magnesium chloride, the crystalline material is washed from calcium chloride by displacement on a belt vacuum filter or a centrifuge with a ratio of L:S = 0.3-0.7:1; washing the crystalline material from magnesium chloride is carried out by diluting the crystalline material in a reactor with a solvent at a temperature of 10-25 °C, the separation of the crystalline material from the liquid after washing from magnesium chloride is carried out by unloading the pulp from the reactor and filtering it, dissolving potassium chloride is carried out in a hot solvent at a temperature of 90-110 °C,Cooling of the potassium-saturated solution with evaporation of part of the water is carried out to a temperature of 20-35 °C, followed by precipitation and filtration of potassium chloride crystals; the potassium chloride crystals separated from the cooled mother liquor are washed with fresh water and filtered.

2. The method according to paragraph 1, characterized in that water or a solution of potassium chloride or sodium chloride is used as a solvent; 3. The method according to paragraph 1, characterized in that the washing of the crystalline material from magnesium chloride is carried out for 1-20 minutes.

4. The method according to paragraph 1, characterized in that the solution obtained after washing the crystalline material from magnesium chloride is sent to obtain carnallite, bischofite, or magnesium oxide, or magnesium by electrolysis.

5. The method according to paragraph 1, characterized in that the filtrate obtained after washing from magnesium chloride is sent to the stage of evaporation of the original brine.

6. The method according to claim 1, characterized in that the mother liquor obtained after crystallization of potassium chloride from a solution saturated with potassium is sent to the stage of hot dissolution of potassium chloride as a solvent.

7. The method according to paragraph 1, characterized in that the solution obtained after the final washing and filtration of potassium chloride crystals is sent to the stage of washing the crystalline material from magnesium chloride.

8. The method according to paragraph 1, characterized in that the filtrate obtained at the stage of washing the crystalline material from calcium chloride is used as raw material for an anti-icing additive or cement slurries.