Potassium chloride purification production process

Abstract

The invention relates to the technical field of chlor-alkali industry, and discloses a potassium chloride purification production process, which comprises: dissolving industrial grade potassium chloride in water to form a uniform potassium chloride solution; carrying out segmented acid adjustment treatment on the obtained potassium chloride solution so as to remove soluble impurity ions contained in the solution; adding a nucleation regulator into the potassium chloride solution subjected to acid regulation and purification, and inducing crystallization under a control condition to generate crystal mush; evaporating and concentrating the crystal mush; carrying out centrifugal separation on the concentrated crystal mush to obtain potassium chloride crystals and mother liquor; drying the obtained potassium chloride crystal to remove residual water on the surface and in the potassium chloride crystal; and screening and grading the dried potassium chloride crystals, and sealing and packaging to obtain the potassium chloride product meeting the medicinal grade standard. The preparation of high-purity, uniform-particle and low-impurity medicinal potassium chloride is realized through synergistic impurity precipitation, concentration crystal control and nucleation adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of chlor-alkali industry, and particularly to a production process for purifying potassium chloride. Background Art

[0002] As a basic inorganic salt, potassium chloride is not only widely used in agricultural production, but also an important raw material for pharmaceutical preparations such as clinical injection solutions and electrolyte supplements. There are more stringent quality control standards for the finished product purity, impurity content, and crystal morphology of pharmaceutical-grade potassium chloride. In current industrial production, potassium chloride is mostly extracted from brine or a preliminarily purified solution by the cooling crystallization method, and impurities are removed by combining operations such as acid adjustment, neutralization, and centrifugation to obtain a solid finished product. However, under this process, common impurities such as calcium and magnesium in the raw materials are easily formed into a co-solution system in the solution due to their similar physical and chemical properties to potassium chloride. If only a single organic acid is used for acid adjustment and impurity precipitation, the precipitation path is often limited, the complexation efficiency is low, and the impurities are difficult to completely precipitate, and finally enter the crystallization system, affecting the purity, whiteness, and stability of pharmaceutical-grade potassium chloride.

[0003] In addition, the conventional production process mostly uses atmospheric cooling for direct crystallization without effectively pre-treating the solution after acid adjustment. During the crystallization process, problems such as local supersaturation of the solution, uneven crystallization rate, and disordered particle size distribution often occur, resulting in irregular crystal morphology, serious agglomeration, and being loose and fragile, which is not conducive to obtaining a pharmaceutical-grade crystal product with a dense structure and uniform particles. Although some technologies alleviate the crystallization abnormality by changing the cooling rate or stirring conditions, none of them control the stability of the solution system itself, and it is difficult to achieve the reproducibility and controllability of the process, affecting the consistency between batches.

[0004] At the same time, the control effect of the nucleation stage on crystal quality is generally ignored in current crystallization. The lack of a nucleation regulation mechanism results in a wide grain size distribution and a loose structure. The crystals are easily adsorbed to each other and even show a "skeleton"-type flocculent crystal form, which not only affects the product appearance but also increases the inclusion risk, reducing the final purification effect and consistency. Such crystals have a loose structure and a strong ability to adhere to impurities, and are extremely easy to absorb moisture and agglomerate during the subsequent drying, storage, and transportation processes, further exacerbating the instability of product performance and seriously affecting the compliance rate of pharmaceutical-grade standards.

[0005] Therefore, the present invention proposes a production process for purifying potassium chloride to solve the deficiencies of the prior art. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a production process for purifying potassium chloride, which solves the problems in the prior art that the impurity sedimentation is not thorough, the crystallization process is uncontrollable, the crystal structure is unstable, and it is difficult to meet the purity and quality requirements of pharmaceutical-grade potassium chloride.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: A potassium chloride purification production process, comprising the following steps:

[0008] Dissolve industrial-grade potassium chloride in water to form a uniform potassium chloride solution;

[0009] Perform segmented acid adjustment on the obtained potassium chloride solution to remove soluble impurity ions contained in the solution;

[0010] Add a nucleation regulator to the acid-adjusted and purified potassium chloride solution, and induce crystallization under controlled conditions to generate crystal slurry;

[0011] Evaporate and concentrate the crystal slurry;

[0012] Centrifuge the concentrated crystal slurry to obtain potassium chloride crystals and mother liquor;

[0013] Dry the obtained potassium chloride crystals to remove residual moisture on the surface and inside;

[0014] Screen and classify the dried potassium chloride crystals and perform sealed packaging to obtain potassium chloride products meeting the pharmaceutical grade standard.

[0015] Preferably, the step of dissolving industrial-grade potassium chloride in water to form a uniform potassium chloride solution includes:

[0016] Add industrial-grade potassium chloride and water to the reaction vessel at a mass ratio of 1:2.5 - 1:4;

[0017] Stir at a temperature of 60 - 80 °C, and the stirring rate is 200 - 400 rpm;

[0018] Stir for 30 - 60 minutes until the potassium chloride is completely dissolved to form a uniform potassium chloride solution.

[0019] Preferably, the step of performing segmented acid adjustment on the obtained potassium chloride solution includes:

[0020] First-stage acid adjustment, add citric acid to the potassium chloride solution, and the addition amount is 0.1% - 0.3% of the mass of the potassium chloride solution, and adjust the pH value to 4.2 - 4.8;

[0021] Second-stage acid adjustment, add tartaric acid or malic acid to the potassium chloride solution, and the addition amount is 0.05% - 0.15% of the mass of the potassium chloride solution, and adjust the pH value to 6.2 - 6.8;

[0022] After completing the acid adjustment, remove the generated precipitate by vacuum filtration.

[0023] Preferably, during the first-stage acid adjustment and the second-stage acid adjustment, the temperature is controlled at 45 - 55°C, the stirring rate is 250 - 350 rpm, and the reaction time is 30 - 45 minutes.

[0024] Preferably, the step of adding a nucleation regulator to the potassium chloride solution after acid adjustment and purification and inducing crystallization to form a crystal slurry under controlled conditions includes:

[0025] Adding a nucleation regulator to the potassium chloride solution after acid adjustment and purification, and the nucleation regulator is selected from polyvinyl alcohol or sodium polyacrylate;

[0026] Controlling the solution temperature at 35 - 45°C, the stirring rate at 100 - 200 rpm, carrying out the crystallization reaction, and the reaction time is 4 - 6 hours;

[0027] After the crystallization reaction ends, a crystal slurry is obtained.

[0028] Preferably, the molecular weight of the nucleation regulator is 10,000 - 30,000 Daltons, and the addition amount is 0.01% - 0.05% of the mass of the potassium chloride solution.

[0029] Preferably, the step of evaporating and concentrating the crystal slurry includes:

[0030] Feeding the crystal slurry into a vacuum evaporation device, controlling the evaporation temperature at 40 - 60°C, and the vacuum degree at 0.06 - 0.09 MPa;

[0031] During the evaporation process, the conductivity and potassium chloride concentration of the solution are monitored in real time to adjust the evaporation temperature and vacuum degree;

[0032] The evaporation time is 1.5 - 3 hours until the solution is concentrated to the required concentration to form a concentrated crystal slurry.

[0033] Preferably, the step of centrifugally separating the concentrated crystal slurry to obtain potassium chloride crystals and mother liquor includes:

[0034] Feeding the concentrated crystal slurry into a centrifugal device, with the centrifugal speed at 3000 - 4500 rpm and the centrifugal time at 5 - 10 minutes;

[0035] During centrifugation, potassium chloride crystals and mother liquor are separated;

[0036] Collect the potassium chloride crystals, analyze the mother liquor according to the impurity ion concentration, return part of the mother liquor to the dissolution stage, and part enters the waste liquid treatment system.

[0037] Preferably, the step of drying the obtained potassium chloride crystals includes:

[0038] Feed the potassium chloride crystals after centrifugal separation into a hot air drying equipment, with a drying temperature of 80 - 95 °C and a drying time of 30 - 50 minutes;

[0039] During the drying process, maintain a constant air flow rate to uniformly remove the moisture on the crystal surface and inside;

[0040] After drying, check the moisture content of the crystals.

[0041] Preferably, the steps of screening, grading and sealing the dried potassium chloride crystals include:

[0042] Feed the dried potassium chloride crystals into a screening equipment with a mesh number of 80, and separate the crystals that meet the particle size requirements after screening;

[0043] Seal and package the qualified potassium chloride crystals after screening.

[0044] The present invention provides a production process for potassium chloride purification. It has the following beneficial effects:

[0045] 1. In the acid - adjustment stage of the present invention, a two - stage organic acid combination impurity - precipitation strategy is adopted. By utilizing the complexation property differences of different acid species, the precipitation ability for calcium and magnesium impurities is significantly enhanced. Compared with the problem of high impurity residue rate in the single - acid acid - adjustment of the traditional process, this method can more effectively remove the impurity sources, keep the product purity and whiteness stable for a long time, and improve the consistency and compliance rate of the pharmaceutical grade.

[0046] 2. The present invention introduces a vacuum concentration link before crystallization to regulate the saturation state and solution volume of the system, and improve the crystal nucleation environment from the source. The present invention avoids the phenomena of uneven crystal grain size and frequent agglomeration in the traditional cooling crystallization process, making the finished product particles evenly distributed and the structure compact, providing a stable basis for subsequent drying and packaging.

[0047] 3. The present invention uses a nucleation regulator to guide the orderly growth of crystals, effectively compressing the particle size distribution range and improving the particle density. Different from the uncontrolled state of "free nucleation" in the conventional technologies on the market, the present invention realizes the controllability of crystal particle size and morphology. The crystals show good appearance quality and fluidity, which better meet the standardized requirements of pharmaceutical products.

[0048] 4. In the overall process design of the present invention, the whole - process overall coupling design of impurity - precipitation, concentration and crystallization is carried out. Multiple links cooperate synergistically, significantly improving the overall stability of the process, breaking through the limitation of "one index improvement leading to the decline of other indexes" in the existing technologies, and realizing the synchronous improvement of multiple indexes such as purity, whiteness and crystal form, which is applicable to the continuous and stable production of industrial pharmaceutical potassium chloride. Description of the Drawings

[0049] Figure 1This is the process flow chart of the present invention. Detailed implementation manners

[0050] Next, in combination with the accompanying drawings of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] In order to better understand the present invention, the above content will be described in detail below in combination with specific embodiments.

[0052] Please refer to the appendix Figure 1 , the present invention provides a potassium chloride purification production process, including the following steps:

[0053] S1. Dissolve industrial-grade potassium chloride in water to form a uniform potassium chloride solution;

[0054] S2. Perform segmented acid adjustment treatment on the obtained potassium chloride solution to remove soluble impurity ions contained in the solution;

[0055] S3. Add a nucleation regulator to the acid-adjusted and purified potassium chloride solution, and induce crystallization to generate crystal slurry under controlled conditions;

[0056] S4. Evaporate and concentrate the crystal slurry;

[0057] S5. Centrifuge the concentrated crystal slurry to obtain potassium chloride crystals and mother liquor;

[0058] S6. Dry the obtained potassium chloride crystals to remove residual moisture on the surface and inside;

[0059] S7. Screen and classify the dried potassium chloride crystals and perform sealed packaging to obtain potassium chloride products meeting the pharmaceutical grade standards.

[0060] For S1, add industrial-grade potassium chloride and water to the reaction vessel at a mass ratio of 1:2.5 - 1:4, control the reaction temperature between 60 - 80 °C, set the stirring rate at 200 - 400 rpm, and continuously stir for 30 - 60 minutes until the potassium chloride is completely dissolved to form a transparent and uniform solution.

[0061] This step mainly accelerates the dissolution rate of potassium chloride by increasing the temperature, and at the same time uses stirring to promote full contact between the solid and the liquid. Appropriately controlling the feed liquid ratio can avoid uneven reactions or precipitation residues caused by being too dilute or too concentrated, and lay a homogeneous foundation for subsequent acid adjustment and impurity removal. Uniform dissolution also helps impurities to be fully released, making subsequent reactions more thorough and avoiding the formation of unstable intermediate products.

[0062] For S2, it specifically includes two stages of acid adjustment: in the first stage, citric acid is added to the solution, and the addition amount is 0.1%-0.3% of the mass of the potassium chloride solution, and the pH value is controlled between 4.2 and 4.8; in the second stage, tartaric acid or malic acid is added, and the addition amount is 0.05%-0.15%, and the pH is further adjusted to 6.2-6.8. During the two-stage acid adjustment process, the temperature is controlled at 45-55 °C, the stirring rate is 250-350 rpm, and the reaction time is 30-45 minutes. After the acid adjustment is completed, vacuum filtration operation is carried out to separate the precipitate.

[0063] By adopting the method of segmented acid adjustment, the complexing and precipitation ability of different organic acids on metal impurities can be fully utilized. Citric acid can effectively chelate cations such as calcium and magnesium, and the subsequent tartaric acid or malic acid promotes the conversion of remaining impurities into insoluble salts and precipitates at a higher pH, improving the breadth and depth of impurity removal. Through the vacuum filtration operation, the precipitate can be quickly removed to prevent the impurities from redissolving into the solution, thus greatly improving the purity in the crystallization stage.

[0064] For S3, a nucleation regulator is added to the purified potassium chloride solution. The nucleation regulator is polyvinyl alcohol or sodium polyacrylate, with a molecular weight of 10,000-30,000 Daltons, and the addition amount is 0.01%-0.05% of the solution mass. The crystallization conditions are controlled within the temperature range of 35-45 °C, the stirring rate is 100-200 rpm, and the reaction time is set to 4-6 hours, and finally a crystal slurry system containing a large amount of crystals is obtained.

[0065] This step forms a "template" for controlling the nucleation point density in the solution by introducing a specific polymer nucleation regulator, thereby precisely regulating the initial nucleation rate and growth direction of the crystals. The regulator can affect the uniformity of the crystal structure and the particle size distribution at the microscopic level, making the crystallization process more controllable, and finally obtaining a crystal morphology with a concentrated particle size distribution and regular structure. The reasonable setting of the temperature and stirring rate can effectively prevent crystal agglomeration or irregular growth.

[0066] For S4, the above crystal slurry is sent into a vacuum evaporation device for concentration treatment. The evaporation temperature is controlled at 40-60 °C, and the vacuum degree is maintained at 0.06-0.09 MPa. During the concentration process, the KCl concentration and conductivity are monitored in real time, and the evaporation rate is adjusted. The whole process lasts for 1.5-3 hours, and finally a concentrated crystal slurry with the target concentration is obtained.

[0067] Adopting low-temperature vacuum evaporation can effectively improve the concentration efficiency while avoiding the risk of high-temperature thermal degradation. The KCl concentration of the solution is closely related to the conductivity, and as an on-line monitoring index, it can reflect the crystal precipitation potential in real time. By dynamically regulating the evaporation parameters, it is ensured that the system is in the best supersaturated state, which is beneficial to the further growth of crystals and at the same time controls the risk of impurity enrichment.

[0068] For S5, the concentrated crystal slurry is fed into a centrifugal separation device. The centrifugal speed is set at 3000 - 4500 rpm and it runs for 5 - 10 minutes to achieve efficient separation of crystals and mother liquor. The crystals are collected for subsequent processing, and the mother liquor, based on its impurity ion concentration, is partially recycled to the dissolution step and partially discharged into the waste liquid treatment system.

[0069] Through the strong centrifugal force field generated by high-speed centrifugation, the crystals and mother liquor are quickly separated, preventing the crystals from redissolving in the mother liquor or adsorbing impurities. The fine control of operating parameters during the centrifugal separation process ensures the integrity of the crystals and the separation effect. The design of mother liquor recycling further improves the material utilization rate, reducing the waste liquid discharge and operating costs of the overall process.

[0070] For S6, the centrifuged crystals are conveyed into a hot air drying device. The drying temperature is controlled at 80 - 95 °C, and the drying time is set at 30 - 50 minutes. A stable air flow rate is maintained during the process to ensure uniform drying. After drying, the moisture content of the crystals is detected to ensure it meets the quality standard requirements.

[0071] The drying stage is a crucial step in ensuring the purity and fluidity of the crystals. Medium-temperature drying ensures efficiency while avoiding sintering on the crystal surface or collapse of the internal structure. The introduction of continuous air flow prevents excessive local temperature rise and accelerates the outward diffusion of internal moisture, improving drying consistency and meeting the requirements of the medicinal standard for crystal stability.

[0072] For S7, the dried crystals are fed into an 80-mesh screening device to remove particles that do not meet the particle size requirements, and the products with qualified particle sizes are retained and sealed and packaged through an automated packaging system.

[0073] Screening can effectively control the particle size distribution of the product, improve the uniformity and solubility during the medicinal preparation process, and avoid dose fluctuations caused by particle differences. The sealed packaging design can significantly reduce problems such as moisture absorption and denaturation, secondary contamination, etc., enhancing the stability and applicability of the finished product during transportation and storage.

[0074] Example 1:

[0075] Raw material ratio (parts by mass): industrial potassium chloride: 100 parts, deionized water: 340 parts, citric acid: 0.3 parts, tartaric acid: 0.12 parts, polyvinyl alcohol (Mw ≈ 20000): 0.03 parts.

[0076] The specific steps are as follows:

[0077] Put 100 parts of potassium chloride into a liquid preparation reaction kettle, add 340 parts of deionized water, heat to 70 °C, adjust the stirring rate to 300 rpm, and maintain for 45 minutes until completely dissolved to obtain a clear potassium chloride solution.

[0078] Transfer to an acid - adjusting reactor with on - line pH monitoring, slowly drop - add citric acid, control the pH of the solution at 4.5, after reacting for 30 minutes, continue to drop - add tartaric acid, adjust to 6.5, and continue to react for 40 minutes. Introduce the flocculent precipitate into a vacuum filtration system with a pre - heating device through a side - mounted drain port, and the impurities are completely separated.

[0079] Transfer the filtrate into a crystallization reaction tank, add polyvinyl alcohol, lower the temperature to 40 °C, and lower the stirring rate to 150 rpm. React for 6 hours, and crystals slowly precipitate to form a uniformly suspended crystal slurry.

[0080] Feed the crystal slurry into a vacuum evaporator through a rotor pump, set the temperature at 55 °C, maintain the system vacuum at 0.09 MPa, continuously evaporate and concentrate for 2 hours, and both the solution viscosity and the crystallization density are significantly increased.

[0081] Feed the concentrated crystal slurry directly into a horizontal scroll centrifuge, set the rotational speed at 4200 rpm, and run for 8 minutes. The solid - liquid separation efficiency is high, and the crystal particles are plump.

[0082] Feed the centrifuged wet crystals into a hot - air circulation dryer, at a temperature of 90 °C, control the time at 50 minutes, and the hot air is evenly blown from the bottom to prevent caking.

[0083] After drying, enter a vibrating screen machine. The screen mesh size is between 80 and 100 meshes. After screening out the middle - section products, they are sealed by an automatic sealing and packaging machine.

[0084] Example 2:

[0085] Raw material ratio (parts by mass): industrial potassium chloride: 100 parts, purified water: 280 parts, citric acid: 0.22 parts, malic acid: 0.10 parts, sodium polyacrylate (Mw≈18000): 0.04.

[0086] Specific steps:

[0087] Add potassium chloride and 280 parts of purified water into a liquid - preparation reaction kettle, set the temperature at 68 °C, set the stirring rate at 320 rpm, and react for 30 minutes to form a uniform solution without impurity suspension.

[0088] Transfer the solution to a double - layer acid - adjusting kettle with temperature control. First, add citric acid until the pH is 4.3, react for 25 minutes, then drop - add malic acid, adjust the pH to 6.3, and react for 35 minutes. The impurity precipitation is obvious. The filtration uses a multi - stage vacuum rotary vane pump suction filtration system, and the filtrate is clear.

[0089] Transport the purified liquid to a seed - induced crystallization tank, and add sodium polyacrylate as a nucleating agent. Control the temperature at 39 °C, stir at 180 rpm, and carry out the crystallization reaction for 5 hours. The crystals grow slowly and the particle size is concentrated.

[0090] After crystallization is completed, the crystal slurry is transferred to a vacuum circulation evaporator, where the temperature is set at 50°C and the vacuum is 0.08 MPa. The concentration time is 2 hours, and the target concentration is reached.

[0091] Solid-liquid separation is carried out by a plate centrifuge. The running time is 6 minutes and the rotation speed is 4000 rpm, with low crystal moisture.

[0092] It is sent to a box-type hot air drying equipment. The drying temperature is 85°C for 45 minutes. The automatic temperature control air duct system ensures that the internal temperature difference does not exceed ±2°C.

[0093] A three-layer vibrating screen system is used to screen products with a particle size of 70-110 mesh and sent to a moisture-proof aluminum-plastic composite packaging line for automatic packaging.

[0094] Example 3:

[0095] Raw material ratio (parts by mass): industrial potassium chloride: 100 parts, water: 310 parts, citric acid: 0.2 parts, malic acid: 0.08 parts, polyvinyl alcohol (Mw≈25000): 0.02.

[0096] Specific steps:

[0097] After potassium chloride is mixed with water, it is heated to 75°C in an enamel heating reaction kettle. The stirring rate is set at 350 rpm, and the reaction is maintained for 35 minutes until it is completely dissolved.

[0098] Citric acid and malic acid are added in a pH automatic regulation system, and the pH is adjusted to 4.4 and 6.4 in sequence, with each reaction lasting for 30 minutes to form a brownish-gray precipitate. The precipitate is removed by a barrel-type pressure filter.

[0099] The solution is transferred to a temperature-controlled crystallization tank, and polyvinyl alcohol is added. The reaction temperature is kept constant at 40°C, and the stirring speed is 100 rpm. After 5.5 hours, a large amount of white fine crystals can be seen.

[0100] The crystal slurry is concentrated using a vacuum falling film evaporator at a temperature of 50°C and a vacuum of 0.08 MPa for 1.8 hours.

[0101] It is transferred to a cylinder-cone centrifuge, the rotation speed is set at 3900 rpm, and the running time is 8 minutes, with complete crystal output.

[0102] Drying is carried out using a hot air circulation box with a mid-infrared auxiliary module at a drying temperature of 88°C for 45 minutes.

[0103] The dried crystals are screened to 80-100 mesh by a pneumatic screening device and packaged using a quantitative packaging system, meeting the export standard.

[0104] Example 4:

[0105] Raw material ratio (parts by mass): industrial potassium chloride: 100 parts, water: 300 parts, citric acid: 0.15 part, tartaric acid: 0.06 part, sodium polyacrylate (Mw≈16000): 0.02 part.

[0106] Specific steps:

[0107] Potassium chloride and water enter the shell-and-tube dissolution reactor through a continuous feed pump, the temperature is controlled at 65 °C, and the propeller agitator maintains a flow rate of about 280 rpm for online mixing and rapid dissolution.

[0108] The acid adjustment unit module sequentially adds citric acid and tartaric acid, and online adjusts the pH to 4.2 and 6.3. The reaction times are 20 and 25 minutes respectively, and the precipitate is filtered online and then discharged by shunting.

[0109] The purified liquid enters the double-effect crystallization tank system, sodium polyacrylate is added, the temperature of the crystallization zone is set at 38 °C, and crystals are formed under stirring and slow cooling conditions for 6 hours.

[0110] The crystal slurry is pumped into the double-effect evaporator, the vacuum degree is maintained at 0.07 MPa, the temperature is 54 °C, and the concentration ratio is controlled within 1.5 times.

[0111] Use continuous belt centrifugation equipment, the separation speed is 3800 rpm, and it runs for 9 minutes to recover the mother liquor.

[0112] Drying is carried out using a vibrating fluidized bed dryer, the temperature transitions from 95 °C in the front section to 85 °C in the rear section, and the total drying time is 50 minutes.

[0113] The product is screened to 90 mesh by air flow and enters the aseptic packaging machine to complete the post-treatment.

[0114] Example Five:

[0115] Raw material ratio (parts by mass): industrial potassium chloride: 100 parts, deionized water: 320 parts, citric acid: 0.28 part, malic acid: 0.11 part, polyvinyl alcohol (Mw≈30000): 0.03 part.

[0116] Specific steps:

[0117] Industrial potassium chloride is added to 320 parts of deionized water, and the dissolution process is completed in a glass-lined reaction kettle. The temperature is set at 72 °C, the stirring speed is 300 rpm, and the reaction time is 40 minutes;

[0118] Citric acid and malic acid are added sequentially, and the pH is controlled at 4.5 and 6.2 respectively. The two-stage filtration system quickly separates the precipitate from the liquid phase to avoid redissolution;

[0119] The purified solution is put into the crystallization reaction tank, polyvinyl alcohol is added, the reaction temperature is 39 °C, and it is gently stirred. After 6 hours, a crystal slurry with uniform particles is formed;

[0120] The crystal slurry is fed into a negative pressure evaporator with a vacuum degree set at 0.085 MPa, an evaporation temperature controlled at 48 °C, and a time of 2 hours;

[0121] A continuous belt centrifuge is used with a separation speed of 3800 rpm for 9 minutes, and the mother liquor is recovered.

[0122] Vibrating fluidized bed dryer is used for drying, with the temperature transitioning from 95 °C in the front section to 85 °C in the rear section, and the total drying time is 50 minutes.

[0123] The product is screened to 90 meshes by air flow and then enters the aseptic packaging machine to complete the post-treatment.

[0124] Comparative Example 1:

[0125] Compared with Example 1, tartaric acid is not added, and the other components, ratios, and preparation processes remain unchanged.

[0126] Comparative Example 2.

[0127] Compared with Example 2, vacuum concentration is not carried out, and it is directly fed into the centrifuge, while the other components, ratios, and preparation processes remain unchanged.

[0128] Comparative Example 3.

[0129] Compared with Example 3, the nucleation regulator (polyvinyl alcohol) is not added, and the other components, ratios, and preparation processes remain unchanged.

[0130] Experiment 1:

[0131] Experimental procedures:

[0132] Sample preparation:

[0133] The industrial potassium chloride for the test is selected from the same batch, and 6 samples (100 g each) are taken and numbered S1 - S6.

[0134] Solution preparation and acid adjustment treatment:

[0135] Samples numbered S1 - S3 are prepared according to the production process of Example 1;

[0136] Samples numbered S4 - S5 are prepared according to the production process of Comparative Example 1;

[0137] Testing methods and number of detections:

[0138] Purity detection of potassium chloride: Volumetric analysis (chemical titration) is used, and the chloride ion content is titrated with a standard silver nitrate solution to calculate the corresponding potassium chloride content; each sample is tested 3 times and the average value is taken;

[0139] Observation of impurity deposition: Spread the dried finished product on a white porcelain plate and visually observe with the naked eye under natural light for the presence of gray spots, color difference, and crystal agglomeration;

[0140] Visual color comparison: Under the same light environment, place the samples on a white background template simultaneously and observe their crystal colors and uniformity, and conduct subjective comparison scoring.

[0141] The experimental results are shown in Table 1:

[0142] Table 1: Comparison results of potassium chloride products between Example 1 and Comparative Example 1

[0143]

[0144] In the comparative example sample, yellowish-gray deposits often appeared on the crystal surface, the particles were loose, and there were obvious impurities attached, indicating that the impurities were not fully removed and the crystallization environment was impure. This is also consistent with its titration purity value, which was always lower than 98.1%.

[0145] The product of the example has good whiteness, concentrated particle distribution, and the titration purity is stable at about 99.3%, indicating that the acid adjustment process is more sufficient, the impurity precipitation is more complete, and the subsequent crystallization environment is cleaner.

[0146] The addition of tartaric acid changed the operation path of the impurity precipitation system. After the action of citric acid, some calcium and magnesium impurities were not completely precipitated. At this time, tartaric acid was introduced to form a stable complex through carboxyl groups, promoting its precipitation to move downward and avoiding entering the finished product system. This supplementary precipitation effect cannot be replaced by non-homogeneous single acids.

[0147] Experiment 2:

[0148] Experimental steps:

[0149] Sample preparation:

[0150] The industrial potassium chloride used in the experiment was selected from the same batch, and 6 samples (100 g each) were taken and numbered A1 - A6.

[0151] Solution preparation and acid adjustment treatment:

[0152] Prepare the samples numbered A1 - A3 according to the production process of Example 2;

[0153] Prepare the samples numbered A4 - A6 according to the production process of Comparative Example 2;

[0154] Testing methods and number of detections:

[0155] Detection of potassium chloride purity: Adopt volumetric analysis (chemical titration), titrate with a standard silver nitrate solution to determine the chloride ion content, and calculate the potassium chloride purity; each sample is detected 3 times and the average value is taken;

[0156] Observation of crystal particles: Spread the dried sample flat on a white porcelain plate and observe with the naked eye whether the crystal particles are uniform, whether there is caking, inclusion, etc.;

[0157] Comparison of appearance color: Subjectively visually compare under natural light, and observe whether the color of the sample is pure under the same background, and record the intuitive impression.

[0158] The experimental results are shown in Table 2:

[0159] Table 2: Comparison results of potassium chloride products between Example 2 and Comparative Example 2

[0160]

[0161]

[0162] The sample in the comparative example was not subjected to vacuum concentration treatment, resulting in a relatively high water content in the solution. During the subsequent cooling crystallization process, the crystallization rate was unstable, causing the crystals to be loose, the morphology to be uneven, caking and inclusion phenomena to occur frequently, and the purity of the final product to drop to about 98%.

[0163] The product of the example reduces the volume of the mother liquor in advance through concentration, increases the supersaturation, makes the crystallization process more sufficient and controllable, the crystal structure is regular, the particle distribution is concentrated, the visual observation is transparent and white, and the titration purity is stable above 99.4%.

[0164] The core value of vacuum concentration lies not in water removal, but in constructing a highly efficient crystallization environment. After concentration, the viscosity of the solution increases, the nucleation conditions tend to be consistent, impurities are easily precipitated and separated in advance, thus avoiding being involved in the crystals later. For this reason, the finished product of the example is stable in state and purity, while there are more residual impurities retained in the crystals of the comparative example, and the appearance and indicators are significantly deteriorated.

[0165] Experiment 3:

[0166] Experimental steps:

[0167] Sample preparation:

[0168] The industrial potassium chloride for the test is selected from the same batch, and 6 samples (100 g each) are taken and numbered B1 - B6.

[0169] Solution preparation and acid adjustment treatment:

[0170] Prepare the samples numbered B1 - B3 according to the production process of Example 3;

[0171] Prepare the samples numbered B4 - B6 according to the production process of Comparative Example 3;

[0172] Test methods and number of detections:

[0173] Potassium chloride purity detection: Using volumetric analysis (chemical titration), the chloride ion content is determined by titrating with a standard silver nitrate solution, and the potassium chloride purity is calculated; each sample is tested 3 times and the average value is taken;

[0174] Observation of crystal grains: Spread the dried sample flat on a white porcelain plate and observe the crystal state with the naked eye under natural light, and record whether there are phenomena such as caking, uneven particle size, and flocculent deposition;

[0175] Visual comparison of appearance color and luster: Place 6 prepared samples on a white bottom plate and observe their crystal colors, lusters, and evenness side by side for subjective evaluation and comparison.

[0176] The experimental results are shown in Table 3:

[0177] Table 3: Comparison results of potassium chloride products in Example 3 and Comparative Example 3

[0178]

[0179]

[0180] The samples in Comparative Example 3 were crystallized under the condition of not adding a nucleation regulator. The crystal grains were of different sizes, some samples caked into groups, and the fluidity was poor. The edges of the particles were blurred, the transparency of the crystals decreased, impurities were easily adsorbed, and the purity was generally lower than 98.3%. The visual color and luster were dull, and flocculent deposition appeared in some samples.

[0181] However, after adding polyvinyl alcohol in Example 3, the finished product particles were clear, closely distributed, the particle size was concentrated, the whiteness was improved, and the hand feeling was loose and dry, indicating that the crystal structure was more complete, the crystallization process was more controllable, and the titration purity was above 99.3%, with an obvious improvement effect.

[0182] The nucleation regulator does not change the reaction path, but stabilizes the crystal formation process at the microscopic level. The molecular chain structure of polyvinyl alcohol provides a crystal nucleus template, reduces disordered aggregation, induces uniform nucleation, enables the crystal to grow stably under supersaturated conditions, and forms a regular and dense structure. Without it, the crystallization process is prone to "spontaneous exposure growth", the crystals adsorb and agglomerate with each other, resulting in structural defects and impurity encapsulation. As a result, the appearance is irregular, the purity is not high, and it is difficult to further purify. Structure determines the result, and regulation precisely determines the structure.

[0183] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A potassium chloride purification production process, characterized in that, It includes the following steps: Dissolve industrial-grade potassium chloride in water to form a uniform potassium chloride solution; Perform segmented acid adjustment on the obtained potassium chloride solution to remove soluble impurity ions contained in the solution; Add a nucleation regulator to the potassium chloride solution after acid adjustment and purification, and induce crystallization under controlled conditions to generate a crystal slurry; Evaporate and concentrate the crystal slurry; Centrifugally separate the concentrated crystal slurry to obtain potassium chloride crystals and mother liquor; Dry the obtained potassium chloride crystals to remove residual moisture on the surface and inside; Screen and classify the dried potassium chloride crystals and perform sealed packaging to obtain a potassium chloride product meeting the pharmaceutical-grade standard.

2. A potassium chloride purification production process according to claim 1, characterized in that The step of dissolving industrial-grade potassium chloride in water to form a uniform potassium chloride solution includes: Add industrial-grade potassium chloride and water to the reaction vessel at a mass ratio of 1:2.5 - 1:4; Stir at a temperature of 60 - 80 °C, and the stirring rate is 200 - 400 rpm; Stir for 30 - 60 minutes until the potassium chloride is completely dissolved to form a uniform potassium chloride solution.

3. The potassium chloride purification production process according to claim 1, characterized in that, The step of performing segmented acid adjustment on the obtained potassium chloride solution includes: The first-stage acid adjustment: Add citric acid to the potassium chloride solution, and the addition amount is 0.1% - 0.3% of the mass of the potassium chloride solution, and adjust the pH value to 4.2 - 4.8; The second-stage acid adjustment: Add tartaric acid or malic acid to the potassium chloride solution, and the addition amount is 0.05% - 0.15% of the mass of the potassium chloride solution, and adjust the pH value to 6.2 - 6.8; After completing the acid adjustment, remove the generated precipitate by vacuum filtration.

4. The potassium chloride purification production process according to claim 3, characterized in that, During the first-stage acid adjustment and the second-stage acid adjustment, control the temperature at 45 - 55 °C, the stirring rate at 250 - 350 rpm, and the reaction time at 30 - 45 minutes.

5. A potassium chloride purification production process according to claim 1, wherein The step of adding a nucleation regulator to the potassium chloride solution after acid adjustment and purification and inducing crystallization under controlled conditions to generate a crystal slurry includes: Add a nucleation regulator to the potassium chloride solution after acid adjustment and purification, and the nucleation regulator is selected from polyvinyl alcohol or sodium polyacrylate; Control the solution temperature at 35 - 45 °C, the stirring rate at 100 - 200 rpm, and carry out the crystallization reaction, and the reaction time is 4 - 6 hours; After the crystallization reaction ends, obtain a crystal slurry.

6. The potassium chloride purification production process according to claim 5, characterized in that, The molecular weight of the nucleation regulator is 10,000 - 30,000 Daltons, and the addition amount is 0.01% - 0.05% of the mass of the potassium chloride solution.

7. A potassium chloride purification production process according to claim 1, characterized in that, The step of evaporating and concentrating the crystal slurry includes: Feed the crystal slurry into a vacuum evaporation device, control the evaporation temperature at 40 - 60 °C, and the vacuum degree at 0.06 - 0.09 MPa; During the evaporation process, monitor the solution conductivity and potassium chloride concentration in real time to adjust the evaporation temperature and vacuum degree; The evaporation time is 1.5 - 3 hours until the solution is concentrated to the required concentration to form a concentrated crystal slurry.

8. A potassium chloride purification production process according to claim 1, characterized in that, The step of centrifugally separating the concentrated crystal slurry to obtain potassium chloride crystals and mother liquor includes: Feed the concentrated crystal slurry into a centrifugal device, the centrifugal speed is 3000 - 4500 rpm, and the centrifugal time is 5 - 10 minutes; During centrifugation, separate the potassium chloride crystals and the mother liquor; Collect the potassium chloride crystals, analyze the mother liquor according to the impurity ion concentration, return part of the mother liquor to the dissolution stage, and part enters the waste liquid treatment system.

9. A potassium chloride purification production process according to claim 1, characterized in that The step of drying the obtained potassium chloride crystals includes: Send the potassium chloride crystals after centrifugal separation into a hot air drying device, with a drying temperature of 80 - 95 °C and a drying time of 30 - 50 minutes; During the drying process, maintain a constant air flow rate to evenly remove the moisture on the surface and inside of the crystals; After drying, check the moisture content of the crystals.

10. The potassium chloride purification production process according to claim 1, characterized in that, The step of screening, grading and hermetically packaging the dried potassium chloride crystals includes: Send the dried potassium chloride crystals into a screening device with a screen mesh size of 80 mesh, and separate the crystals that meet the particle size requirements after screening; Hermetically package the qualified potassium chloride crystals after screening.

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