A method for preparing high-quality low-sodium salt

Abstract

This invention discloses a method for preparing high-quality low-sodium salt. The preparation method includes: providing a first raw material, a second raw material, and a base liquid, wherein the first raw material comprises a sodium-potassium saturated solution, the second raw material comprises magnesium chloride ore, and the base liquid comprises the following components: Na... + K + Mg 2+ C1 ‑ The process involves placing the base liquid in a DTB crystallization apparatus and simultaneously introducing the first and second raw materials at a first and a second feed rate, respectively, under a stirring speed of 500–700 rpm. After at least 80 minutes, intermittent discharge is performed, followed by solid-liquid separation to obtain high-quality low-sodium salt. The high-quality low-sodium salt prepared by this invention has a particle size greater than 150 μm in 96% of the product. Furthermore, the preparation method is simple and controllable, achieving precise particle size control in the low-sodium salt production process.

Description

Technical Field

[0001] This invention belongs to the field of inorganic salt industry technology, specifically relating to a method for preparing high-quality low-sodium salt. Background Technology

[0002] Low-sodium salt products meet the QB / T-2019-2020 standard (NaCl 65.0%-80.0%, KCl 20.0%-35.0%, particle size greater than 150 micrometers); potassium recycling rate ≥90%. China's high-sodium diet has made hypertension one of the major diseases threatening national health. According to the Fourth National Nutrition and Health Survey, those with a daily salt intake of ≥18 grams have a 27% increased risk of hypertension. The latest nutrition survey results show that the daily salt intake of Chinese residents is as high as 12 grams, exceeding the World Health Organization's recommendation of 5 grams.

[0003] Patent CN201710109056.4 discloses a method for preparing low-sodium salt products from chloride-type salt lake brine by adjusting the salt precipitation ratio during natural evaporation. Patent CN201810726693.0 utilizes sulfate-type salt lake brine and takes advantage of the winter climate conditions in the Qaidam Basin to remove sulfate ions through a freezing process, followed by natural evaporation to prepare low-sodium salt products. Meanwhile, some literature uses salt lake by-products such as old brine, carnallite, and fresh water as raw materials, obtaining crude low-sodium salt products through brine mixing at room temperature, which can then be directly obtained through filtration and drying. However, due to the complexity of salt lake brine and the significant influence of coexisting ions, the yield of low-sodium salt in this process is low. Furthermore, the brine mixing process introduces other ions into the system, and the product requires cleaning, leading to poor reproducibility and batch instability.

[0004] Currently, low-sodium salt technology is relatively new, and effective production techniques include direct mixing, seawater or brine evaporation, and halophyte extraction. Mixing methods all require food-grade additives, and chemical purification can lead to chemical pollution and is expensive, resulting in generally high costs for low-sodium salt. With varying degrees of marine pollution, seawater-based low-sodium salt production cannot guarantee food-grade quality. Halophyte extraction is limited by regional resource distribution, and the high extraction temperature and long processing time significantly increase production costs. Low-sodium salt products have a non-concentrated particle size distribution, high impurity content, and complex impurity removal processes, resulting in insufficient sodium and potassium content. Evaporation methods produce low-sodium salt with small particle sizes, and the proportion of solid products with particle sizes larger than 150μm is low. Therefore, providing a high-quality, controllable particle size, green low-sodium salt production method is an urgent problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing high-quality low-sodium salt to overcome the shortcomings of existing technologies.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a method for preparing high-quality low-sodium salt, comprising:

[0008] The system provides a first raw material, a second raw material, and a base liquid, wherein the first raw material comprises a sodium-potassium saturated solution, the second raw material comprises hydrated magnesium chloride ore, and the base liquid comprises the following components: Na + K + Mg 2+ Cl - and H2O;

[0009] Furthermore, the bottom liquid is placed in a DTB crystallization device, and the first raw material and the second raw material are simultaneously fed into the DTB crystallization device at a first feed rate and a second feed rate under the condition of a stirring rate of 500-700 rpm. After at least 80 minutes, the material is intermittently discharged, and then solid-liquid separation is performed to obtain high-quality low-sodium salt.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention produces high-quality low-sodium salt by controlling the feed rate, raw material ratio, rotation speed and discharge method of raw materials and using an intermittent discharge method. 96% of the high-quality low-sodium salt produced has a particle size greater than 150μm. At the same time, the preparation method is simple and controllable, and the problem of precise particle size control in the low-sodium salt production process is solved. In addition, the high-quality low-sodium salt obtained by the present invention has low intercalation degree of KCl and NaCl crystals, good dispersion degree, smooth surface and few surface defects. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of a DTB crystallizer used in a typical embodiment of the present invention;

[0013] Figure 2 This is a schematic diagram of the process for preparing high-quality low-sodium salt in a typical embodiment of the present invention;

[0014] Figure 3 This is a particle size distribution diagram of the low-sodium salt prepared by the present invention using existing technology;

[0015] Figure 4This is a particle size distribution diagram of the low-sodium salt prepared in Example 1 of the present invention;

[0016] Figure 5 This is a morphology diagram of the low-sodium salt prepared using existing technology according to the present invention;

[0017] Figure 6 This is a morphological diagram of the low-sodium salt prepared in Example 1 of the present invention. Detailed Implementation

[0018] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly involves adding sodium and potassium saturated solutions and magnesium chloride solids in different ways in a DTB crystallizer, and controlling the feed rate, rotation speed and discharge mode to obtain high-grade low-sodium salt.

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Specifically, as one aspect of the technical solution of this invention, a method for preparing a high-quality low-sodium salt includes:

[0021] The system provides a first raw material, a second raw material, and a base liquid, wherein the first raw material comprises a sodium-potassium saturated solution, the second raw material comprises hydrated magnesium chloride ore, and the base liquid comprises the following components: Na + K + Mg 2+ Cl - and H2O;

[0022] Furthermore, the bottom liquid is placed in a DTB crystallization device, and the first raw material and the second raw material are simultaneously fed into the DTB crystallization device at a first feed rate and a second feed rate under the condition of a stirring rate of 500-700 rpm. After at least 80 minutes, the material is intermittently discharged, and then solid-liquid separation is performed to obtain high-quality low-sodium salt.

[0023] In some preferred embodiments, the sodium chloride content in the sodium-potassium saturated solution is 15.0–16.0 wt%, and the potassium chloride content is 12.0–13.0 wt%.

[0024] In some preferred embodiments, the density of the sodium-potassium saturated solution is 1.1550 to 1.2200 g / mL.

[0025] Furthermore, the density of the sodium-potassium saturated solution is 1.1935 g / mL.

[0026] In some preferred embodiments, the Mg in the hydrated magnesium ore 2+ The content is 10.5–12.9 wt%.

[0027] In some preferred embodiments, the base liquid comprises the following components by mass percentage: Na + 0.6–0.9 wt%, K + 1.5–1.9 wt%, Mg 2+ 5.8–6.6 wt%, Cl - 21.4–22.3 wt% and H2O 68.5–69.8 wt%.

[0028] In some preferred embodiments, the amount of the base liquid added is 500-650 mL.

[0029] In some preferred embodiments, the mass ratio of the first raw material to the second raw material is 1:0.8 to 0.9.

[0030] In some preferred embodiments, the effective volume of the DTB crystallization apparatus is 3000–6000 mL.

[0031] Furthermore, the effective volume of the DTB crystallization device is 4500 mL.

[0032] In some preferred embodiments, the first feed rate of the first raw material is 10 to 15 mL / min.

[0033] In some preferred embodiments, the second feed rate of the second raw material is 10-15 mL / min.

[0034] In some preferred embodiments, the intermittent discharge includes: discharging material from the bottom of the DTB crystallization device after 80 minutes of feeding, with a discharge interval of 30 to 60 minutes.

[0035] Furthermore, the discharge interval is 40 minutes.

[0036] Furthermore, the intermittent discharge is a 5-stage intermittent discharge.

[0037] Furthermore, the mass ratio of each discharge amount to the mass of the material in the DTB crystallization device is 1:3 to 1:4.

[0038] Furthermore, the amount of material discharged intermittently each time is 1100-1300g.

[0039] In some preferred embodiments, the preparation method further includes: after the intermittent discharge is completed, adding an equal mass of base liquid to the DTB crystallization device.

[0040] In some preferred embodiments, the solution obtained from the solid-liquid separation is recycled as the base liquid.

[0041] In some preferred embodiments, the proportion of material with a particle size greater than 150 μm in the high-quality low-sodium salt is above 96 wt%.

[0042] In some preferred embodiments, the NaCl content in the high-quality low-sodium salt is 66.84–69.71 wt%.

[0043] In some more specific embodiments, the method for preparing the high-quality low-sodium salt includes the following steps:

[0044] (1) Prepare a saturated sodium-potassium chloride solution with a concentration of 15.0–16.0 wt% sodium chloride (NaCl) and 12.0–13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I (i.e., the first raw material mentioned above); Mg 2+ Magnesia-hydrate mineral (MgCl·6H2O) with a content of 10.5–12.9 wt% is referred to as Raw Material II (i.e., the aforementioned second raw material). The formulation contains Na... + 0.6-0.9 wt%, K + 1.5–1.9 wt%, Mg 2+ 5.8–6.6 wt%, Cl - A solution containing 21.4–22.3 wt% H2O and 68.5–69.8 wt% is referred to as the base solution.

[0045] Wherein: the mass ratio of raw material I to raw material II is 1:0.8 to 0.9, and the amount of bottom liquid added is 5000 to 6500 mL.

[0046] (2) The equipment used in this technology is a DTB crystallizer, the structure of which is shown in Figure 1, with an effective volume of 4500 mL.

[0047] (3) The specific process is as follows: Add the base liquid to the crystallizer and turn on the stirring device to stir at a speed of 500-700 rpm. Then, feed raw material I and raw material II into the crystallizer and control their feed rates. The feed rates are: raw material I - 10-15 mL / min and raw material II - 10-15 g / min. Timing starts when feeding begins. After feeding for 80 minutes, discharge from the bottom of the crystallizer at 40-minute intervals, with a discharge volume of 1100-1300 g. After each discharge, replenish with the corresponding amount of base liquid. See the schematic diagram of the control process. Figure 2 .

[0048] The discharge process consists of 5 stages every 80 minutes. After solid-liquid separation, the discharged liquid phase is returned to the crystallizer, while the solid phase is the low-sodium salt product. 96% of the low-sodium salt product has a particle size greater than 150μm, and the proportion of low-sodium salt particles larger than 150μm in each discharge stage exceeds 95%. The potassium chloride and sodium chloride content meet national standards.

[0049] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0050] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0051] Example 1

[0052] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 16.0 wt% sodium chloride (NaCl) and 13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ The raw material, referred to as raw material II, is a magnesium chloride ore (MgCl₂·6H₂O) with a content of 11.3 wt%. The preparation contains Na... + 0.6wt%, K + 1.5wt%, Mg 2+ 5.8wt%, Cl - A solution containing 21.4 wt% H2O and 68.5 wt% is referred to as the base solution.

[0053] The mass ratio of raw material I to raw material II is 1:0.8, and the amount of bottom liquid added is 5000mL.

[0054] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 500 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 10 mL / min and 10 g / min, respectively. Start timing when feeding.

[0055] 3. After 80 minutes, stage 1 discharge; after 120 minutes, stage 2 discharge; after 160 minutes, stage 3 discharge; after 200 minutes, stage 4 discharge; and after 240 minutes, stage 5 discharge. The material obtained from each stage is subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, and the solid phase is the low-sodium salt product. Product analysis is shown in Tables 1 and 2.

[0056] Table 1. Analysis Results of Low-Sodium Salt Products

[0057]

[0058] Table 2 Results of Low Sodium Salt Content in Products

[0059]

[0060] The particle size distribution of low-sodium salts prepared by direct mixing or brine evaporation is as follows: Figure 2 As shown, the morphology is as follows Figure 4 As shown, the particle size distribution of the low-sodium salt product prepared in Example 1 is as follows: Figure 3 As shown, the morphology is as follows Figure 5 As shown, it can be seen that the low-sodium salts prepared by the direct mixing method or brine evaporation method in the prior art have an average particle size of 50-170 μm and a morphology as shown in the figure. Figure 4 As shown, the intercalation of KCl and NaCl crystals during crystallization is a significant phenomenon. Some researchers have attempted to inhibit this intercalation by adding an organic additive to the crystallization system. However, this method is ineffective and introduces new organic components into the system, increasing the cleaning process and cost of the low-sodium salt. The low-sodium salt prepared in this embodiment has an average particle size of 150–350 μm and a morphology as shown... Figure 5 As shown, KCl and NaCl crystals exhibit low intercalation, good dispersion, smooth surfaces, and significantly fewer surface defects compared to low-sodium salt morphologies prepared using existing techniques.

[0061] Comparative Example 1:

[0062] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 16.0 wt% sodium chloride (NaCl) and 13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ The raw material, referred to as raw material II, is a magnesium chloride ore (MgCl·6H2O) with a content of 11.3 wt%. The preparation contains Na... + 0.6wt%, K + 1.5wt%, Mg 2+ 5.8wt%, Cl - A solution containing 21.4 wt% H2O and 68.5 wt% is referred to as the base solution.

[0063] The mass ratio of raw material I to raw material II is 1:0.8, and the amount of bottom liquid added is 5000mL.

[0064] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 500 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 5 mL / min and 5 g / min, respectively. Start timing when feeding.

[0065] 3. After 80 minutes, stage 1 discharge; after 120 minutes, stage 2 discharge; after 160 minutes, stage 3 discharge; after 200 minutes, stage 4 discharge; and after 240 minutes, stage 5 discharge. The material obtained from each stage is subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, and the solid phase is the low-sodium salt product. Product analysis is shown in Tables 3 and 4.

[0066] Table 3. Analysis Results of Low-Sodium Salt Products

[0067]

[0068] Table 4. Results of Low Sodium Salt Content in Products

[0069]

[0070] Comparative Example 2

[0071] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 16.0 wt% sodium chloride (NaCl) and 13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ The raw material, referred to as raw material II, is a magnesium chloride ore (MgCl·6H2O) with a content of 11.3 wt%. The preparation contains Na... + 0.6wt%, K + 1.5wt%, Mg 2+ 5.8wt%, Cl - A solution containing 21.4 wt% H2O and 68.5 wt% is referred to as the base solution.

[0072] The mass ratio of raw material I to raw material II is 1:0.8, and the amount of bottom liquid added is 5000mL.

[0073] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 500 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 20 mL / min and 20 g / min, respectively. Start timing when feeding.

[0074] 3. After 80 minutes, discharge stage 1; after 120 minutes, discharge stage 2; after 160 minutes, discharge stage 3; after 200 minutes, discharge stage 4; and after 240 minutes, discharge stage 5. The material obtained from each stage is subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, and the solid phase is the low-sodium salt product. Product analysis is shown in Tables 5 and 6.

[0075] Table 5. Analysis Results of Low-Sodium Salt Products

[0076]

[0077] Table 6. Results of Low Sodium Salt Content in Products

[0078]

[0079] Comparative Example 3

[0080] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 16.0 wt% sodium chloride (NaCl) and 13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ The raw material, referred to as raw material II, is a magnesium chloride ore (MgCl·6H2O) with a content of 11.3 wt%. The preparation contains Na... + 0.6wt%, K + 1.5wt%, Mg 2+ 5.8wt%, Cl - A solution containing 21.4 wt% H2O and 68.5 wt% is referred to as the base solution.

[0081] The mass ratio of raw material I to raw material II is 1:0.8, and the amount of bottom liquid added is 5000mL.

[0082] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 300 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 10 mL / min and 10 g / min, respectively. Start timing when feeding.

[0083] 3. Discharge stage 1 after 80 min, stage 2 after 120 min, stage 3 after 160 min, stage 4 after 200 min, and stage 5 after 240 min. The material obtained from each stage is subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, and the solid phase is the low-sodium salt product. Product analysis is shown in Tables 7 and 8.

[0084] Table 7. Analysis Results of Low-Sodium Salt Products

[0085]

[0086] Table 8. Results of Low Sodium Salt Content in Products

[0087]

[0088] Comparative Example 4

[0089] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 16.0 wt% sodium chloride (NaCl) and 13.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ The raw material, referred to as raw material II, is a magnesium chloride ore (MgCl·6H2O) with a content of 11.3 wt%. The preparation contains Na... + 0.6wt%, K + 1.5wt%, Mg 2+ 5.8wt%, Cl -A solution containing 21.4 wt% H2O and 68.5 wt% is referred to as the base solution.

[0090] The mass ratio of raw material I to raw material II is 1:0.8, and the amount of bottom liquid added is 5000mL.

[0091] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 1000 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 10 mL / min and 10 g / min, respectively. Start timing when feeding.

[0092] 3. Discharge stage 1 after 80 min, stage 2 after 120 min, stage 3 after 160 min, stage 4 after 200 min, and stage 5 after 240 min. The material obtained from each stage is subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, and the solid phase is the low-sodium salt product. Product analysis is shown in Tables 9 and 10.

[0093] Table 9. Analysis Results of Low-Sodium Salt Products

[0094]

[0095] Table 10 Results of Low Sodium Salt Content in Products

[0096]

[0097] Example 2

[0098] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 15.0 wt% sodium chloride (NaCl) and 12.0 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as Raw Material I. (Mg) 2+ Raw material II is a 10.5 wt% magnesium chloride ore (MgCl·6H2O). The preparation contains Na... + 0.9wt%, K + 1.9wt%, Mg 2+ 6.6wt%, Cl - A solution containing 22.3 wt% H2O and 69.8 wt% is referred to as the base solution.

[0099] The mass ratio of raw material I to raw material II is 1:0.9, and the amount of bottom liquid added is 6500mL.

[0100] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 600 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 15 mL / min and 15 g / min, respectively. Start timing when feeding.

[0101] 3. After 80 minutes, discharge stage 1; after 120 minutes, discharge stage 2; after 160 minutes, discharge stage 3; after 200 minutes, discharge stage 4; and after 240 minutes, discharge stage 5. The material obtained from each stage is then subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, while the solid phase is the low-sodium salt product.

[0102] Example 3

[0103] 1. Prepare a saturated sodium-potassium chloride solution with a concentration of 15.8 wt% sodium chloride (NaCl) and 13.4 wt% potassium chloride (KCl), with a density of 1.1935 g / mL. This solution is referred to as raw material I. Mg 2+ The raw material, referred to as raw material II, is a 12.9 wt% magnesium chloride ore (MgCl·6H2O). The preparation contains Na... + 0.87wt%, K + 1.87wt%, Mg 2+ 6.27wt%, Cl - A solution containing 21.7 wt% H2O and 69.0 wt% H2O is referred to as the base solution.

[0104] The mass ratio of raw material I to raw material II is 1:0.88, and the amount of bottom liquid added is 6000mL.

[0105] 2. Add the base liquid to the crystallizer, turn on the stirring device and stir at a speed of 700 rpm. The feeding rates of raw material I and raw material II into the crystallizer are 13 mL / min and 13 g / min, respectively. Start timing when feeding.

[0106] 3. After 80 minutes, discharge stage 1; after 120 minutes, discharge stage 2; after 160 minutes, discharge stage 3; after 200 minutes, discharge stage 4; and after 240 minutes, discharge stage 5. The material obtained from each stage is then subjected to solid-liquid separation. The liquid phase enters the bottom liquid storage tank, while the solid phase is the low-sodium salt product.

[0107] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0108] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing high-quality low-sodium salt, characterized in that, include: The system provides a first raw material, a second raw material, and a base liquid, wherein the first raw material comprises a sodium-potassium saturated solution, the second raw material comprises hydrated magnesium chloride ore, and the base liquid comprises the following components: Na + K + Mg 2+ Cl - and H2O; The base liquid is placed in a DTB crystallization apparatus, and the first raw material and the second raw material are simultaneously fed into the DTB crystallization apparatus at a stirring rate of 500-700 rpm at a first feed rate and a second feed rate, wherein the first feed rate of the first raw material is 10-15 mL / min; the second feed rate of the second raw material is 10-15 g / min; after at least 80 min, intermittent discharge is performed, the intermittent discharge is a 5-stage intermittent discharge, the intermittent discharge includes: after 80 min of feeding, discharge is performed from the bottom of the DTB crystallization apparatus, the discharge interval is 30-60 min; then solid-liquid separation is performed to obtain high-quality low-sodium salt; the proportion of material with a particle size greater than 150 μm in the high-quality low-sodium salt is more than 96 wt%.

2. The preparation method according to claim 1, characterized in that: The sodium chloride saturated solution contains 15.0-16.0 wt% sodium chloride and 12.0-13.0 wt% potassium chloride.

3. The preparation method according to claim 1, characterized in that: The density of the sodium-potassium saturated solution is 1.1550~1.2200 g / mL.

4. The preparation method according to claim 1, characterized in that: Mg in water-magnesium ore 2+ The content is 10.5~12.9 wt%.

5. The preparation method according to claim 1, characterized in that: The base liquid comprises the following components by mass percentage: Na + 0.6~0.9 wt%, K + 1.5~1.9 wt%, Mg 2+ 5.8~6.6 wt%, Cl - 21.4~22.3 wt% and H2O 68.5~69.8 wt%.

6. The preparation method according to claim 1, characterized in that: The amount of the base liquid added is 500~650mL.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the first raw material to the second raw material is 1:0.8~0.

9.

8. The preparation method according to claim 1, characterized in that: The effective volume of the DTB crystallization device is 3000~6000 mL.

9. The preparation method according to claim 1, characterized in that: The mass ratio of each discharge amount to the mass of the material in the DTB crystallization device is 1:3 to 1:

4.

10. The preparation method according to claim 1, characterized in that, Also includes: After the intermittent discharge is completed, an equal mass of bottom liquid is added to the DTB crystallization device.

11. The preparation method according to claim 1, characterized in that: The solution obtained from the solid-liquid separation is recycled as the base liquid.

12. The preparation method according to claim 1, characterized in that: The NaCl content in the high-quality low-sodium salt is 66.84~69.71 wt%.

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