Method for purifying high-grade potassium chloride from high-magnesium soluble solid potassium salt mine by removing impurities

Abstract

The present application relates to the technical field of impurity removal and purification of soluble solid potassium salt mine, and discloses a method for removing impurities and purifying high-grade potassium chloride from high-magnesium soluble solid potassium salt mine, which comprises two-stage decomposition-crystallization-screening steps, wherein after the first-stage decomposition-crystallization, primary screening, second-stage decomposition-crystallization and secondary screening, fine-particle material is combined to obtain flotation feed slurry; a flotation impurity removal step, wherein KCl positive flotation collector is added for positive flotation to obtain a crude potassium product; a hot-solubilization-cooling crystallization purification step, wherein the crude potassium product is mixed with hot fresh water above 80 DEG C for hot solubilization, and after the insoluble substances are separated, the product is cooled and recrystallized to obtain fine potassium crystals and KCl unsaturated liquid; an evaporation crystallization step, wherein the KCl unsaturated liquid is heated and evaporated, and recrystallized after cooling to obtain recrystallized substances; and a product combining and drying step, wherein the fine potassium crystals and the recrystallized substances are combined, and after drying, high-grade potassium chloride products with KCl content of 98% or more are obtained. The present application effectively removes fine mud and residual sodium chloride, and significantly improves the product grade and yield.

Description

Technical Field

[0001] This invention relates to the field of potassium chloride purification technology for soluble solid potassium salt ore, and particularly to a method for purifying high-grade potassium chloride from high-magnesium soluble solid potassium salt ore. Background Technology

[0002] Carnallite is an important hydrous potassium-magnesium chloride double salt mineral with the chemical formula KCl·MgCl2·6H2O. It is a product of the late-stage evaporation of arid inland salt lakes and is often associated with halite, potassium halite, and hydrated magnesium chloride. It is a major raw material for the production of potassium chloride.

[0003] The main processes for processing carnallite into potassium chloride both domestically and internationally include: direct flotation, reverse flotation-cold crystallization, and hot melt crystallization.

[0004] Direct flotation (especially cold decomposition crystallization-direct flotation) is widely used in the production of potassium chloride from carnallite: at room temperature, carnallite ore is decomposed and recrystallized in a decomposition crystallizer with fresh water to obtain artificial potassium salt ore. Then, taking advantage of the difference in floatability between potassium chloride and sodium chloride, a potassium chloride collector is added to separate potassium chloride and sodium chloride. This process is simple, reliable, and adaptable to raw materials, but the quality of the potassium chloride product is not high (mostly producing agricultural potassium chloride products with a KCl content of 90%), and the process recovery rate is also low (≤65%).

[0005] The reverse flotation-cold crystallization method (such as the method disclosed in CN202410431314A) involves adding sodium chloride flotation reagent to the ore pulp, causing the sodium chloride to float to the surface with the froth and be scraped off, while carnallite remains in the pulp. Potassium chloride is then obtained through dehalogenation, cold decomposition crystallization, screening, and flotation. This method can remove some large-particle sodium chloride, achieving a potassium chloride yield of over 65% and a product grade of approximately 95%. However, this method is still a reverse flotation process, and for primary carnallite ores with complex compositions, it is difficult to achieve the high-grade requirement of over 98% for the product.

[0006] The hot-melt crystallization method utilizes the different solubilities of sodium chloride and potassium chloride at different temperatures, achieving separation through high-temperature dissolution and cooling crystallization. This method can produce high-purity potassium chloride, but it has drawbacks such as high energy consumption, high cost, and severe equipment corrosion.

[0007] Existing two-stage crystallization processes (such as the method disclosed in CN116161680A) employ a cold decomposition-crystallization and direct flotation process using two crystallizers connected in series. By connecting the first and second crystallizers in series, the decomposition efficiency of carnallite and the process recovery rate of potassium are improved (≥72%), and the product grade can reach over 95%. However, this process still ends with direct washing and drying after direct flotation. For primary carnallite ore containing fine mud and residual sodium chloride, conventional washing cannot further purify it, and the product grade is difficult to break through the high-grade threshold of 98%.

[0008] In particular, the complex mineral composition of primary carnallite deposits in Mengye, Yunnan Province, and Southeast Asia makes it difficult to enrich potassium using conventional processing techniques. Even with the addition of large amounts of fresh water during the re-washing stage, the potassium chloride content in the refined potassium only meets the qualified standard (approximately 90% KCl content) for industrial and agricultural potassium chloride (GB6549-2011), failing to meet the superior grade requirement of 98%. Furthermore, potassium chloride products produced from primary carnallite deposits using conventional processing methods are gray in color and lack whiteness.

[0009] Therefore, the existing technology has the following problems: Conventional positive flotation methods produce products with lower grades (≤90%) and yields (≤65%).

[0010] Although the reverse flotation method (CN202410431314A) has made some improvements, it is still difficult to obtain high-grade (≥98%) potassium chloride for primary carnallite ores with complex compositions.

[0011] The hot melt crystallization method is energy-intensive and costly.

[0012] Although the existing two-stage crystallization process (CN116161680A) has improved the yield (≥72%), the product purity is still around 95%, which cannot meet the production demand for high-grade (≥98%) potassium chloride.

[0013] For specific mineral types (such as primary carnallite mines in Yunnan and Southeast Asia), existing processes are completely unable to achieve the 98% superior grade standard, and the whiteness of the products is poor.

[0014] In summary, there is an urgent need to develop a processing method that can effectively remove fine mud and residual sodium chloride from primary carnallite ore, improve product whiteness, and obtain high-grade potassium chloride. Summary of the Invention

[0015] The technical problem this invention aims to solve is that, in existing technologies, conventional methods such as direct flotation, reverse flotation-cold crystallization, and two-stage crystallization are insufficient to effectively remove fine mud and residual sodium chloride from high-magnesium primary carnallite ores with complex mineral compositions (especially underground primary carnallite ores from Mengye, Yunnan, China, and Southeast Asia). This results in potassium chloride products failing to exceed the 98% high-grade threshold, exhibiting poor whiteness and low yield. This invention aims to provide a processing method for primary carnallite ores that can efficiently remove impurities and significantly improve the grade, yield, and whiteness of potassium chloride products.

[0016] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for removing impurities and purifying high-magnesium soluble solid potassium salt ore to obtain high-grade potassium chloride includes the following steps: S1. Two-stage decomposition-crystallization-screening: The crushed high-magnesium solid potassium salt ore undergoes a first-stage decomposition-crystallization to obtain a mixed slurry; the mixed slurry undergoes a first-stage screening to obtain coarse-grained material and fine-grained material; the coarse-grained material undergoes a second-stage decomposition-crystallization, and the material after the second-stage decomposition-crystallization undergoes a second-stage screening; the fine-grained material obtained from the two screenings is combined to obtain a flotation feed slurry. S2. Flotation to remove impurities: KCl positive flotation collector is added to the flotation feed slurry to perform positive flotation and obtain crude potassium product; S3. Hot dissolution-cooling crystallization purification: The crude potassium product is mixed with hot fresh water at above 80°C for hot dissolution, and the insoluble matter is separated; the resulting saturated liquid is cooled and recrystallized to separate refined potassium crystals and KCl-containing unsaturated liquid. S4. Evaporation and crystallization: The KCl-containing unsaturated liquid is heated and evaporated to form a supersaturated solution, which is then cooled and recrystallized to obtain a recrystallized product. S5. Product merging and drying: The refined potassium crystals and the recrystallized body are merged, and after dehydration and drying, potassium chloride product with KCl content ≥98% is obtained.

[0017] As a preferred technical solution, in step S1, both the primary and secondary screening are performed using a 0.7-0.8 mm standard sieve.

[0018] As a preferred technical solution, in step S1, the temperature of the first stage of decomposition-crystallization is 15℃±5℃, the stirring intensity is 80-100rpm, and the decomposition-crystallization time is 60 minutes.

[0019] As a preferred technical solution, in step S2, the KCl positive flotation collector is potash ore collector YTH-26-1, the dosage is 70g / t of raw ore, the flotation concentration is 25% (mass percentage), and the flotation pH value is 4-5.

[0020] As a preferred technical solution, in step S3, the slurry after hot melting is allowed to stand for 30 to 60 minutes, and the bottom potassium is separated using a separatory funnel, the middle layer contains fine mud potassium salt, and the upper layer is saturated clear liquid.

[0021] As a preferred technical solution, in step S4, the evaporation and crystallization are carried out under normal pressure and the heating temperature is 100-105℃.

[0022] As a preferred technical solution, in step S4, the water vapor emitted by the heating and evaporation is recovered by countercurrent condensation of room temperature water and reused in production.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly improve product quality Through a two-stage decomposition-crystallization-sieving process, coarse-grained halite is effectively removed; KCl and NaCl, as well as high-magnesium mother liquor, are further separated by positive flotation; and residual NaCl and fine mud in the crude potassium are further removed by hot dissolution-cooling crystallization, taking advantage of the significant difference in solubility of KCl and NaCl at high temperatures. This significantly increases the KCl grade from 90-95% in conventional processes to over 98%, meeting the superior grade standard for industrial and agricultural potassium chloride (GB6549-2011).

[0024] (2) Improve the comprehensive recovery rate of potassium resources Through a two-stage decomposition-crystallization-sieving process, carnallite in coarse-grained materials is fully recovered; KCl in the hot-melt-cooled crystallization mother liquor is recovered through an evaporation crystallization step, ensuring a high overall yield (up to 65% or more).

[0025] (3) Improve product appearance and particle size By employing a hot-melt-cooling crystallization step, impurities such as fine mud in the flotation crude potassium carbonate are effectively separated, solving the problems of grayish color and low whiteness in primary carnallite ore products processed by conventional processes, and significantly improving product whiteness. Testing shows that the product of this invention has a whiteness of up to 79.9 and an average particle size of 164.8 μm (D50 of 88.20 μm). Compared with conventional direct flotation processes (where product whiteness is typically less than 70, average particle size is about 100 μm, and fine powder content is high), the product's appearance quality and particle size distribution are significantly improved, better meeting the needs of high-value-added industrial applications.

[0026] (4) Reduce energy consumption and costs This invention performs decomposition-crystallization at room temperature, requiring heating only in the hot-melt-cooling crystallization and evaporation crystallization steps, significantly reducing energy consumption compared to the full-process hot-melt crystallization method. Furthermore, the freshwater recovery design during the evaporation crystallization process reduces freshwater consumption, aligning with green chemical engineering principles.

[0027] (5) Strong process adaptability This invention designs a specialized process for high-magnesium primary carnallite ores with complex mineral compositions (such as those from Yunnan and Southeast Asia), solving the technical difficulties that conventional processes struggle to handle such ores, and has wide applicability.

[0028] (6) The process is simple and easy to industrialize. This invention organically combines conventional unit operations such as decomposition-crystallization-screening, flotation, hot melting-cooling crystallization, and evaporation crystallization to form a complete purification chain. The equipment is mature and reliable, and it is easy to realize large-scale industrial production. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0031] Example 1

[0032] A method for removing impurities and purifying high-magnesium soluble solid potassium salt ore to obtain high-grade potassium chloride includes the following steps: (1) Two-stage decomposition-crystallization-sieving: (1a) Crushing: The primary carnallite ore mined underground is crushed to a particle size of less than 10 mm. The chemical composition of the carnallite ore used in this embodiment is: K + Content 10.04%, Na + Content 6.02%, Mg 2+ Content 10.29%, Cl - Content 43.29%.

[0033] (1b) Decomposition and crystallization of high-magnesium carnallite: using K + Na + Mg 2+ / / Cl - The -H2O isothermal quaternary hydro-salt phase diagram yielded a theoretical decomposition water content of 41%. Carnallite ore was added to 38% fresh water, and under conditions of 15℃ and a stirring intensity of 80–100 rpm, the decomposition-crystallization time was controlled at 60 minutes to obtain a mixed slurry containing NaCl (halite), KCl (potassium halite), MgCl2·6H2O (magnesium chloride), and KCl·MgCl2·6H2O (carnallite). The solid phase K... + The recovery rate was 86.47%, and the Mg in the liquid phase was... 2+ The decomposition rate was 95.88%.

[0034] (1c) Primary screening and classification: The mixed slurry obtained in step (1b) is classified using a 0.8mm standard sieve to obtain coarse-grained material (mainly a mixture of halite and a small amount of carnallite) and fine-grained material (mainly potassium halite, a small amount of halite, and high-magnesium ion saturated mother liquor). Among these, the -0.8mm fine-grained material contains K... + The content is 30.64%, Mg 2+ The content is 1.58%, Na + The content is 14.26%, Cl - The content is 41.15%, K + Recovery rate was 84.52%; +0.8mm coarse-grained medium K + The content is 1.32%, Mg 2+ The content is 0.71%, Na + The content is 35.13%, Cl- The content is 57.20%, K + The recovery rate was 3.03%.

[0035] (1d) Secondary carnallite decomposition-crystallization: Add 1.2% fresh water (based on the amount of raw ore) to the coarse-grained material obtained in step (1c) to further decompose carnallite and obtain a mixed slurry of NaCl (halite), KCl (potassium halite), MgCl2・6H2O (magnesium chloride), and KCl・MgCl2・6H2O (carnallite).

[0036] (1e) Secondary sieving and classification: The mixed slurry obtained in step (1d) is further classified using a 0.8mm standard sieve to obtain coarse-grained material (as NaCl tailings, to remove impurity sodium) and fine-grained material. Among them, the -0.8mm fine-grained material contains K... + The content is 25.8%, Mg 2+ The content is 0.94%, Na + The content is 15.8%, Cl - The content was 50.47%, the yield was 1.80%, and K + Recovery rate was 4.38%; K in the +0.8mm coarse-grained fraction + The content is 0.16%, Mg 2+ The content is 0.52%, Na + The content is 38.46%, Cl - The content was 58.04%, the yield was 20.38%, and K + The recovery rate was 0.31% (i.e., potassium loss rate was 0.31%). The +0.8mm coarse-grained grade can be used as tailings filler or further developed into other products.

[0037] The fine-grained materials obtained in steps (1c) and (1e) are combined and used as flotation feed slurry, K + The recovery rate was 88.9%.

[0038] (2) Flotation for impurity removal: Add potassium salt collector YTH-26-1 to the above flotation feed slurry at a dosage of 70 g / t of raw ore, with a flotation concentration of 25% and a flotation pH of 4-5. After slurry conditioning, aeration, and a single positive flotation roughing operation, K is obtained. + The content is 45.24%, Mg 2+ The content is 0.88%, Na + The content is 1.93%, Cl - The content was 47.21%, the yield was 20.47%, and K + The crude potassium product had a recovery rate of 86.14% and a KCl content of 88.28%.

[0039] (3) Hot dissolution-cooling crystallization purification: The above crude potassium product is mixed with hot fresh water at 80℃ at a weight ratio of 1:1 for hot dissolution. After standing for 30-60 minutes, the insoluble matter is separated and impurities such as fine mud are removed. The resulting saturated liquid is cooled and recrystallized and aged to separate refined potassium crystals and KCl-containing unsaturated liquid.

[0040] (4) Evaporation and crystallization: The above-mentioned unsaturated liquid containing KCl is heated to 100-105℃ under normal pressure to evaporate the water until it is supersaturated. After cooling, it is recrystallized to obtain the recrystallized body. The water vapor volatilized is recovered by countercurrent condensation of room temperature water and reused in production.

[0041] (5) Product merging and drying: The high-grade potassium product obtained in step (3) is merged with the recrystallized product obtained in step (4), and after dehydration and drying, K is obtained. + High-grade potassium chloride product with a content of 51.47% (KCl content of 98.15% and K2O content of 62.02%).

[0042] Product performance testing: Physical performance tests were conducted on the above products, and the results are as follows: Particle size data: The volume average particle size (D[4,3]) was 164.8 μm, the median particle size (D50) was 88.20 μm, the proportion of particles with a diameter less than 150 μm was 69.6%, and the proportion of particles with a diameter less than 75 μm was 43.4%.

[0043] Whiteness data: The whiteness of the product is 79.9, measured using a whiteness meter (according to GB / T 23774-2009).

[0044] Example 2

[0045] A method for removing impurities and purifying high-magnesium soluble solid potassium salt ore to obtain high-grade potassium chloride includes the following steps: (1) Two-stage decomposition-crystallization-sieving: (1a) Crushing: The primary carnallite ore mined underground is crushed to a particle size of less than 10 mm. The chemical composition of the carnallite ore used in this embodiment is: K + Content 10.77%, Na + Content 5.43%, Mg 2+ Content 12.95%, Cl - Content 45.53%.

[0046] (1b) Decomposition and crystallization of high-magnesium carnallite: using K + Na + Mg 2+ / / Cl -The -H2O isothermal quaternary aqueous phase diagram was used to calculate the theoretical decomposition water content as 41%. Carnallite ore was added to 39% fresh water, and under conditions of 15℃ and a stirring intensity of 80-100 rpm, the decomposition-crystallization time was controlled to be 60 minutes to obtain a mixed slurry. Among these, the solid phase K... + The recovery rate was 87.64%, and the Mg in the liquid phase was... 2+ The decomposition rate was 95.96%.

[0047] (1c) Primary sieving and classification: The mixed slurry obtained in step (1b) is classified using a 0.8mm standard sieve to obtain K-grade fine particles of -0.8mm. + The content is 36.44%, Mg 2+ Content is 0.9%, Na + The content is 5.86%, Cl - The content is 45.58%, K + Recovery rate was 82.43%; K in the +0.8mm coarse-grained fraction + The content is 1.79%, Mg 2+ The content is 1.03%, Na + The content is 35.22%, Cl - The content is 56.65%, K + The recovery rate was 3.55%.

[0048] (1d) Secondary carnallite decomposition-crystallization: The coarse-grained material obtained in step (1c) is further decomposed by adding 3.84% fresh water (based on the amount of raw ore).

[0049] (1e) Secondary sieving and classification: The mixed slurry obtained in step (1d) is classified using a 0.8mm standard sieve to obtain K-grade fine particles of -0.8mm. + The content is 18.33%, Mg 2+ The content is 0.48%, Na + The content is 23.87%, Cl - The content was 54.56%, the yield was 1.43%, and K + Recovery rate was 4.38%; K in the +0.8mm coarse-grained fraction + The content is 0.13%, Mg 2+ The content is 0.46%, Na + The content is 38.79%, Cl - The content was 57.54%, the yield was 20.13%, and K + The recovery rate was 0.24% (i.e., potassium loss rate was 0.24%). The +0.8mm coarse-grained grade was used as tailings filler or further developed into other products.

[0050] The fine-grained materials obtained in steps (1c) and (1e) are combined and used as flotation feed slurry, K + The recovery rate was 86.81%.

[0051] (2) Flotation for impurity removal: Add potassium salt collector YTH-26-1 to the above flotation feed slurry at a dosage of 70 g / t of raw ore, with a flotation concentration of 25% and a flotation pH of 4-5. After slurry conditioning, aeration, and a single positive flotation roughing operation, K is obtained. + The content is 45.11%, Mg 2+ The content is 0.89%, Na + The content is 2.24%, Cl - The content was 46.44%, the yield was 20.05%, and K + The crude potassium product had a recovery rate of 85.86% and a KCl content of 86.02%.

[0052] (3) Hot dissolution-cooling crystallization purification: The above crude potassium product is mixed with hot fresh water at 80℃ at a weight ratio of 1:1 for hot dissolution. After standing, the insoluble matter is separated and impurities such as fine mud are removed. The resulting saturated liquid is cooled and recrystallized and aged to separate refined potassium crystals and KCl-containing unsaturated liquid.

[0053] (4) Evaporation and crystallization: The above-mentioned unsaturated liquid containing KCl is heated to 100-105℃ under normal pressure to evaporate the water until it is supersaturated. After cooling, it is recrystallized to obtain the recrystallized body. The water vapor volatilized is recovered by countercurrent condensation of room temperature water and reused in production.

[0054] (5) Product merging and drying: The high-grade potassium product obtained in step (3) is merged with the recrystallized product obtained in step (4), and after dehydration and drying, K is obtained. + High-grade potassium chloride product with a content of 51.5% (KCl content of 98.21% and K2O content of 62.06%).

[0055] Product performance test: The particle size and whiteness performance of the product in this embodiment are similar to those in Example 1, with similar physical indicators (average particle size of about 165 μm and whiteness of about 79.9).

[0056] Example 3

[0057] A method for removing impurities and purifying high-magnesium soluble solid potassium salt ore to obtain high-grade potassium chloride includes the following steps: (1) Two-stage decomposition-crystallization-sieving: (1a) Crushing: The primary carnallite ore mined underground is crushed to a particle size of less than 10 mm. The chemical composition of the carnallite ore used in this embodiment is: K + Content 10.04%, Na +Content 6.02%, Mg 2+ Content 10.29%, Cl - Content 43.29%.

[0058] (1b) Decomposition and crystallization of high-magnesium carnallite: using K + Na + Mg 2+ / / Cl - The -H2O isothermal quaternary aqueous salt phase diagram was used to calculate the theoretical decomposition water content as 41%. Carnallite ore was added to 40% fresh water, and under conditions of 15℃ and a stirring intensity of 80-100 rpm, the decomposition-crystallization time was controlled to be 60 minutes to obtain a mixed slurry. Among these, the solid phase K... + The recovery rate was 85.0%, and the Mg in the liquid phase was... 2+ The decomposition rate was 95.82%.

[0059] (1c) Primary sieving and classification: The mixed slurry obtained in step (1b) is classified using a 0.8mm standard sieve to obtain K-grade fine particles of -0.8mm. + The content is 37.02%, Mg 2+ The content is 0.68%, Na + The content is 6.1%, Cl - The content is 45.41%, K + Recovery rate was 82.86%; +0.8mm coarse-grained medium K + The content is 1.44%, Mg 2+ The content is 0.93%, Na + The content is 34.45%, Cl - The content is 55.98%, K + The recovery rate was 2.94%.

[0060] (1d) Secondary carnallite decomposition-crystallization: The coarse-grained material obtained in step (1c) is further decomposed by adding 5.12% fresh water (based on the amount of raw ore).

[0061] (1e) Secondary sieving and classification: The mixed slurry obtained in step (1d) is classified using a 0.8mm standard sieve to obtain K-grade fine particles of -0.8mm. + The content is 20.63%, Mg 2+ The content is 0.49%, Na + The content is 22.06%, Cl - The content was 52.46%, the yield was 1.87%, and K + Recovery rate was 3.37%; K in the +0.8mm coarse-grained fraction + The content is 0.09%, Mg 2+ Content is 0.4%, Na+ The content is 39.88%, Cl - The content was 58.42%, the yield was 19.13%, and K + The recovery rate is 0.15% (i.e., potassium loss rate is 0.15%). The +0.8mm coarse-grained grade can be used as tailings filler or further developed into other products.

[0062] The fine-grained materials obtained in steps (1c) and (1e) are combined and used as flotation feed slurry, K + The recovery rate was 88.9%.

[0063] (2) Flotation for impurity removal: Add potassium salt collector YTH-26-1 to the above flotation feed slurry at a dosage of 70 g / t of raw ore, with a flotation concentration of 25% and a flotation pH of 4-5. After slurry conditioning, aeration, and a single positive flotation roughing operation, K is obtained. + The content is 44.5%, Mg 2+ The content is 1.02%, Na + The content is 1.83%, Cl - The content was 46.59%, the yield was 21.18%, and K + The crude potassium product had a recovery rate of 86.34% and a KCl content of 84.85%.

[0064] (3) Hot dissolution-cooling crystallization purification: The above crude potassium product is mixed with hot fresh water at 80℃ at a weight ratio of 1:1 for hot dissolution. After standing, the insoluble matter is separated and impurities such as fine mud are removed. The resulting saturated liquid is cooled and recrystallized and aged to separate refined potassium crystals and KCl-containing unsaturated liquid.

[0065] (4) Evaporation and crystallization: The above-mentioned unsaturated liquid containing KCl is heated to 100-105℃ under normal pressure to evaporate the water until it is supersaturated. After cooling, it is recrystallized to obtain the recrystallized body. The water vapor volatilized is recovered by countercurrent condensation of room temperature water and reused in production.

[0066] (5) Product merging and drying: The high-grade potassium product obtained in step (3) is merged with the recrystallized product obtained in step (4), and after dehydration and drying, K is obtained. + High-grade potassium chloride product with a content of 51.48% (KCl content of 98.17% and K2O content of 62.03%).

[0067] Product performance test: The particle size and whiteness performance of the product in this embodiment are similar to those in Example 1, with similar physical indicators (average particle size of about 165 μm and whiteness of about 79.9).

[0068] Explanation of product specifications In the above embodiments of this application, the KCl content is based on K +The content was calculated; particle size was determined using a laser particle size analyzer, and whiteness was determined using a whiteness meter according to GB / T 23774-2009 standard. All data are actual test results of the product. The conversion formula for KCl content is: KCl content = K + Content / 0.5244; The conversion formula for K2O content is: K2O content = K + Content × 1.205. Product grade classification is based on GB6549-2011 (potassium chloride for industrial and agricultural use).

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for purifying high grade potassium chloride by removing impurities from a high-magnesium soluble solid potash salt mine, characterized by, Includes the following steps: S1. Two-stage decomposition-crystallization-screening: The crushed high-magnesium solid potassium salt ore undergoes a first-stage decomposition-crystallization to obtain a mixed slurry; the mixed slurry undergoes a first-stage screening to obtain coarse-grained material and fine-grained material; the coarse-grained material undergoes a second-stage decomposition-crystallization, and the material after the second-stage decomposition-crystallization undergoes a second-stage screening; the fine-grained material obtained from the two screenings is combined to obtain a flotation feed slurry. S2. Flotation to remove impurities: KCl positive flotation collector is added to the flotation feed slurry to perform positive flotation and obtain crude potassium product; S3. Hot dissolution-cooling crystallization purification: The crude potassium product is mixed with hot fresh water at above 80°C for hot dissolution, and the insoluble matter is separated; the resulting saturated liquid is cooled and recrystallized to separate refined potassium crystals and KCl-containing unsaturated liquid. S4. Evaporation and crystallization: The KCl-containing unsaturated liquid is heated and evaporated to form a supersaturated solution, which is then cooled and recrystallized to obtain a recrystallized product. S5. Product merging and drying: The refined potassium crystals and the recrystallized body are merged, and after dehydration and drying, potassium chloride product with KCl content ≥98% is obtained.

2. The method of claim 1, wherein: In step S1, both primary and secondary screening are performed using a 0.7-0.8 mm standard sieve.

3. The method according to claim 1, characterized in that: In step S1, the temperature of the first stage of decomposition-crystallization is 15℃±5℃, the stirring intensity is 80~100rpm, and the decomposition-crystallization time is 60 minutes.

4. The method according to claim 1, characterized in that: In step S2, the KCl positive flotation collector is potash ore collector YTH-26-1, the dosage is 70 g / t of raw ore, the flotation concentration is 25%, and the flotation pH value is 4-5.

5. The method according to claim 1, characterized in that: In step S3, the slurry after hot melting is allowed to stand for 30 to 60 minutes, and the bottom potassium is separated using a separatory funnel. The middle layer contains fine mud potassium salts, and the upper layer is saturated clear liquid.

6. The method according to claim 1, characterized in that: In step S4, evaporation and crystallization are carried out under normal pressure and the heating temperature is 100-105°C.

7. The method according to claim 1, characterized in that: In step S4, the water vapor generated by heating and evaporation is recovered by countercurrent condensation with room temperature water and reused in production.

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