Ammonium carnallite as well as preparation method and application thereof

Abstract

The invention provides ammonium carnallite as well as a preparation method and application thereof. The preparation method of the ammonium carnallite comprises the following steps: S1, carrying out vacuum evaporative crystallization on a raw material solution to obtain a first crystallized feed liquid; the raw material solution comprises the following components in percentage by weight: 35-45% of magnesium chloride hexahydrate, 4-10% of ammonium chloride and the balance of water; s2, cooling the first crystallization feed liquid to obtain second crystallization feed liquid; s3, growing the second crystallization feed liquid to obtain ammonium carnallite; wherein the vacuum degree of the vacuum evaporation crystallization is 0 to 0.09 MPa; the cooling rate is 15-30 DEG C / h. By optimizing the components of the salt solution and accurately controlling the evaporative crystallization and cooling rate, the preparation efficiency of the ammonium carnallite is remarkably improved, the energy consumption is reduced, the quality and yield of the product are improved, the environmental pollution is reduced, and greenization and high efficiency of preparation of the ammonium carnallite are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of eutectic inorganic salts, and in particular, to an ammonium carnallite, a preparation method thereof, and an application thereof. Background Art

[0002] Magnesium, as a key light non-ferrous metal, plays an important role in fields such as industry, transportation, and aerospace, and its demand continues to grow with the rapid development of the global economy.

[0003] Ammonium carnallite (MgCl2·NH4Cl·H2O) is an important intermediate for producing anhydrous magnesium chloride. Its uniqueness lies in its ability to effectively inhibit the hydrolysis of magnesium chloride, thereby improving the stability and quality of the final product. In the process of converting brine into anhydrous magnesium chloride, the efficient preparation of ammonium carnallite is particularly crucial, which can directly determine the purity and yield of the final product.

[0004] The traditional preparation process of ammonium carnallite mainly relies on the 1:1 isothermal evaporation crystallization method, that is, at a specific temperature, ammonium chloride and magnesium chloride are mixed in an equimolar ratio, and water is evaporated at a high temperature, and then the product is crystallized by cooling. However, this method faces significant limitations, including: 1. Uncontrollability of product quality: inaccurate temperature control may cause ammonium chloride or magnesium chloride to crystallize prematurely, forming impurities that are difficult to separate, seriously affecting the purity and yield of ammonium carnallite. 2. High energy consumption problem: Isothermal evaporation is carried out at a high temperature, with huge energy consumption and high production costs, which is not conducive to energy conservation, emission reduction, and green production. 3. Difficulty in regulating the evaporation rate: The isothermal evaporation under atmospheric pressure has an evaporation rate that is not easy to regulate, which in turn affects the particle size and purity of the product, and is not conducive to post-treatment and application. 4. Environmental pollution: Ammonium chloride reacts incompletely, and the residual ammonium chloride may cause secondary pollution to the environment during the treatment process, increasing the difficulty and cost of recycling and treatment.

[0005] The above problems limit the preparation efficiency of ammonium carnallite and the further utilization of magnesium resources. Summary of the Invention

[0006] The main object of the present invention is to provide an ammonium carnallite, a preparation method thereof, and an application thereof, so as to solve the problems of unstable quality, low yield, high energy consumption, and serious pollution of ammonium carnallite in the prior art.

[0007] To achieve the above object, according to one aspect of the present invention, a method for preparing carnallite-ammonium is provided, comprising the following steps: Step S1, subjecting a raw material solution to vacuum evaporation crystallization to obtain a first crystallization stock solution; by weight percentage, the raw material solution comprises 35-45% of magnesium chloride hexahydrate, 4-10% of ammonium chloride, and the balance of water; Step S2, cooling the first crystallization stock solution to obtain a second crystallization stock solution; Step S3, subjecting the second crystallization stock solution to crystal growth to obtain carnallite-ammonium; wherein, the vacuum degree of the vacuum evaporation crystallization is 0.05-0.09 MPa; the cooling rate is 15-30 °C / h.

[0008] Further, by weight percentage, the raw material solution comprises 42% of magnesium chloride, 7% of ammonium chloride, and the balance of water.

[0009] Further, by weight percentage, the raw material solution comprises 40-45% of magnesium chloride hexahydrate, 5-8% of ammonium chloride, and the balance of water.

[0010] Further, in the raw material solution, the weight ratio of magnesium chloride hexahydrate to ammonium chloride is (5-8):1.

[0011] Further, in Step S1, the vacuum degree of the vacuum evaporation crystallization is 0.07-0.09 MPa; preferably, the evaporation rate of the vacuum evaporation crystallization is 0.02-0.1 kg / h; and / or, the temperature of the vacuum evaporation crystallization is 70-85 °C; and / or, during the vacuum evaporation crystallization process, the total evaporation amount of water accounts for 30-80% of the initial water content; and / or, the solid content of the first crystallization stock solution is 7-25%, and the average particle size of the solid is 1.5-30 mm.

[0012] Further, in Step S2, the cooling rate is 15-20 °C / h; and / or, the end temperature of the cooling is 15-27 °C; and / or, the solid content of the second crystallization stock solution is 70-80%, and the average particle size of the solid is 1.5-30 mm.

[0013] Further, in Step S3, the temperature of the crystal growth is 15-27 °C, and the time is 0.5-5 h.

[0014] Further, in Step S3, it further comprises the steps of filtering and drying the carnallite-ammonium in sequence; preferably, the drying temperature is 20-50 °C, and the time is 0.5-12 h.

[0015] According to another aspect of the present invention, a carnallite-ammonium is provided, which is obtained according to the above method for preparing carnallite-ammonium.

[0016] Furthermore, the purity of carnallite ≥ 90%; and / or, the average particle size of carnallite is 1.5 - 30 mm; and / or, the yield of carnallite ≥ 80 wt%; and / or, the coefficient of variation of carnallite ≤ 50%.

[0017] According to another aspect of the present invention, there is provided the use of the above-mentioned carnallite in the production of anhydrous magnesium chloride.

[0018] Based on the phase diagram and evaporation principle, by optimizing the composition of the salt solution and precisely controlling the evaporation crystallization and cooling rate, the present invention not only significantly improves the preparation efficiency of carnallite, reduces energy consumption, but also improves the quality and yield of the product, reduces environmental pollution, realizes the greening and high efficiency of carnallite preparation, and opens up a new path for the sustainable development of the magnesium industry and ecological environment protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0020] Figure 1 It shows a scanning electron microscope image of the carnallite of Example 1 of the present invention at a magnification of 20 times; and

[0021] Figure 2 It shows a scanning electron microscope image of the carnallite of Example 1 of the present invention at a magnification of 40 times. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0023] TERM EXPLANATION:

[0024] Coefficient of variation: The coefficient of variation is a statistical index used to measure the relative variation degree of a data set. It is the ratio of the standard deviation to the mean, usually expressed in percentage form. The larger the coefficient of variation, the greater the relative variability of the data; the smaller the coefficient of variation, the more concentrated the data.

[0025] It should be noted that the "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances to describe the embodiments of the present invention.

[0026] As described in the background art of the present invention, there are problems in the prior art such as unstable quality of carnallite, low yield, high energy consumption, and serious pollution. To solve the above problems, in a typical embodiment of the present invention, a method for preparing carnallite is provided, including the following steps: Step S1, performing vacuum evaporation crystallization on the raw material solution to obtain a first crystallized stock solution; by weight percentage, the raw material solution includes 35-45% of magnesium chloride hexahydrate, 4-10% of ammonium chloride, and the balance of water; Step S2, cooling the first crystallized stock solution to obtain a second crystallized stock solution; Step S3, performing crystal cultivation on the second crystallized stock solution to obtain carnallite; wherein, the vacuum degree of the vacuum evaporation crystallization is 0.05-0.09 MPa; the cooling rate is 15-30 °C / h.

[0027] Through in-depth research on the phase diagram and thermodynamic properties, the inventors found that: during the crystallization process of carnallite, stirring is not conducive to the growth of carnallite crystals, and the reaction effect is poor when the ratio of magnesium chloride hexahydrate to ammonium chloride is 1:1. Based on this, the present application specifically limits the ratio of magnesium chloride hexahydrate and ammonium chloride in the aqueous solution, especially making magnesium chloride supersaturated to avoid the resource waste, recycling problems, and environmental burden caused by excessive ammonium chloride. Specifically, the present application precisely controls the content of magnesium chloride hexahydrate in the raw material solution to be 35-45%, and the content of ammonium chloride to be 4-10%. Combining with the evaporation curve of the carnallite ternary phase diagram, within this range, the quality and yield of the product can be effectively improved. It should be noted that if the content of magnesium chloride hexahydrate is too low, ammonium chloride single crystals will be produced, resulting in low purity of carnallite. If the content of ammonium chloride is too high, ammonium chloride single crystals will be produced. If the content of ammonium chloride is too low, a large amount of magnesium chloride will crystallize, also resulting in low purity of carnallite.

[0028] In addition, the present application specifically performs evaporation crystallization on the mixed solution system composed of water, magnesium chloride hexahydrate, and ammonium chloride under low-pressure conditions. By controlling the vacuum degree of the evaporation process within a specific range, the evaporation rate can be precisely controlled, and then the crystallization process can be strictly controlled. This can not only effectively avoid the phenomenon of burst nucleation, reduce the generation of fine crystals, significantly improve the purity of carnallite, but also significantly increase the yield based on the correlation between the saturated vapor pressure and temperature. At the same time, this method can reduce the mother liquor residue, making the entire production process efficient and environmentally friendly. However, if the vacuum degree is too high, the energy consumption will be too high and the economy will be reduced. If the vacuum degree is too low, the reaction time will be too long and the efficiency will be low. Compared with natural evaporation, the vacuum evaporation in the present application can effectively reduce the reaction time and reaction temperature.

[0029] In addition, the present application specifically defines that before reaching the evaporation limit of the aqueous solution, a specific cooling rate is adopted to slowly cool the aqueous solution to room temperature to promote the uniform growth of carnallite crystals, and to avoid problems such as inconsistent crystal morphology and too small crystal size caused by too fast cooling rate, or too large crystals caused by too slow cooling rate, so as to effectively improve the uniformity and purity of the carnallite particle distribution. If the cooling rate is too fast, it may lead to too high supersaturation, crystal burst nucleation, and the nucleation rate is greater than the growth rate, resulting in too small particle size and reduced purity of carnallite crystals. If the cooling rate is too slow, it will lead to increased energy consumption.

[0030] All in all, the preparation method of the present application can effectively control the crystal growth rate by optimizing the composition of the salt solution and precisely controlling the evaporation crystallization and cooling rate, which is beneficial to significantly improve the environmental protection, economy and product quality in the process of preparing carnallite.

[0031] In a preferred embodiment, by weight percentage, the raw material solution comprises 40-45% of magnesium chloride, 5-8% of ammonium chloride and the balance of water to further optimize the carnallite crystallization process, improve the purity of carnallite and reduce the generation of by-products.

[0032] In a preferred embodiment, in the raw material solution, the weight ratio of magnesium chloride hexahydrate to ammonium chloride is (5-8):1. Under the above conditions, the stability of the raw material solution can be more effectively improved, and the too fast or too slow crystallization caused by supersaturation can be avoided, and thus the controllability of the process and the stability of the product can be more effectively improved.

[0033] In a preferred embodiment, in step S1, the vacuum degree of vacuum evaporation crystallization is 0.07-0.09 MPa to further accelerate the evaporation process and reduce energy consumption at the same time.

[0034] In a preferred embodiment, the evaporation rate of vacuum evaporation crystallization is 0.02-0.1 kg / h; and / or, the temperature of vacuum evaporation crystallization is 70-85 °C. Under the above conditions, the crystallization process can be more effectively controlled, and the crystallization problems caused by too fast or too slow evaporation can be avoided. If the evaporation rate of vacuum evaporation crystallization is too fast, it may lead to burst nucleation. If the evaporation rate of vacuum evaporation crystallization is too slow, it may lead to increased energy consumption.

[0035] In a preferred embodiment, during the vacuum evaporation crystallization process, the total evaporation amount of water accounts for 30-80% of the initial water content. Under the above conditions, it can be ensured that the solution starts to cool and crystallize when it is close to the saturated state, which is beneficial to obtaining purer crystals. If the total evaporation amount of water is too much during the vacuum evaporation crystallization process, it may lead to the precipitation of ammonium chloride crystals. If the total evaporation amount of water is too little, it may lead to too low supersaturation, decreased yield, too small crystal size, and even the generation of fine powder.

[0036] In a preferred embodiment, the solid content of the first crystallization mother liquor is 7-25%, and the average particle size of the solid is 1.5-30 mm. Under the above conditions, it is more conducive to subsequent cooling crystallization.

[0037] In order to more effectively improve the uniformity and controllability of the crystallization process and avoid irregular crystal morphology caused by too fast crystal growth, in a preferred embodiment, in step S2, the cooling rate is 15-20 °C / h; and / or, the end temperature of cooling is 15-27 °C. In a preferred embodiment, the solid content of the second crystallization mother liquor is 70-80%, and the average particle size of the solid is 1.5-30 mm. Under the above conditions, it is more conducive to crystal growth.

[0038] In a preferred embodiment, in step S3, the crystal aging temperature is 15-27 °C and the time is 0.5-5 h. Under the above conditions, the crystals can grow more uniformly, which is more conducive to improving the particle size uniformity and purity of the product. If the crystal aging time is too long, large crystals may be produced and the crystal size is uneven. If the time is too short, the crystal growth may be insufficient and the size is too small.

[0039] In order to further effectively separate crystals and solution, reduce crystal breakage, and improve the product yield and purity, in a preferred embodiment, in step S3, it further includes the steps of sequentially filtering and drying carnallite; preferably, the drying temperature is 20-50 °C and the time is 0.5-12 h. Under the above conditions, it can more effectively avoid excessive drying and structural damage of the crystals and maintain the crystal morphology of carnallite. In addition, if the drying temperature is too low, the pressure is too small or the time is too short, the solvent removal rate may be too slow, resulting in low purity and small crystal grains of carnallite and high energy consumption.

[0040] All in all, through a large number of experimental studies, the inventors adjusted various reaction parameters and obtained preferred process conditions, providing a reliable basis for the actual production design of the pilot plant.

[0041] In another typical embodiment of the present invention, a carnallite is also provided, which is obtained according to the above preparation method of carnallite. As mentioned above, in this application, by finely adjusting the composition of the salt solution and optimizing key process parameters such as evaporation crystallization and cooling, the purity and yield of carnallite can be effectively and stably controlled, and the energy consumption and production cost are reduced, and the pollution in the preparation process is reduced.

[0042] In a preferred embodiment, the purity of carnallite ≥ 90 wt%; and / or, the average particle size of carnallite is 1.5-30 mm; and / or, the yield of carnallite ≥ 80 wt%; and / or, the coefficient of variation of carnallite ≤ 50%.

[0043] In another typical embodiment of the present invention, the above-mentioned carnallite is also provided for use in the production of anhydrous magnesium chloride. As mentioned above, the carnallite of the present application has high purity, high yield and low energy consumption. In addition, the amount of waste liquid generated in the preparation process is reduced. Using the carnallite of the present application as an intermediate raw material can significantly improve the product quality and reduce the cost, providing a solid foundation for the clean, high-quality and efficient production of anhydrous magnesium chloride and metallic magnesium.

[0044] Typically but not limited to, the vacuum degree of vacuum evaporation crystallization is 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa or a range value composed of any two of these values; the cooling rate is 15 °C / h, 16 °C / h, 17 °C / h, 18 °C / h, 19 °C / h, 20 °C / h, 25 °C / h, 30 °C / h or a range value composed of any two of these values.

[0045] Typically but not limited to, in the aqueous solution, the content of magnesium chloride hexahydrate is 35%, 37%, 39%, 40%, 41%, 42%, 43%, 44%, 45% or a range value composed of any two of these values; the content of ammonium chloride is 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range value composed of any two of these values.

[0046] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0047] Example 1

[0048] 166.51 g of magnesium chloride hexahydrate and 23.39 g of ammonium chloride were dissolved in 200 ml of water and stirred evenly to obtain an aqueous solution, in which the content of magnesium chloride hexahydrate was 42.71% and the content of ammonium chloride was 6%. The raw material solution was placed in a crystallizer and vacuum evaporation crystallization was carried out under the conditions of a temperature of 75 °C, a vacuum degree of 0.09 MPa and an evaporation rate of 0.05 kg / h. When the evaporated water reached 130 g (i.e., the total evaporation amount of water accounted for 65% of the initial water content), cooling was started, and the cooling rate was controlled at 25 °C / h until 25 °C. Subsequently, crystallization was carried out for 1 h, and filtration was carried out using filter paper. Finally, drying was carried out at a temperature of 50 °C for 1 h to obtain carnallite. The scanning electron micrograph of the carnallite is shown in Figure 1 、 Figure 2 . As can be seen from the figure, the particle size of the carnallite is large and evenly distributed.

[0049] Using the carnallite as an intermediate raw material, anhydrous magnesium chloride was prepared. The anhydrous magnesium chloride has high purity and few impurities.

[0050] Example 2

[0051] Dissolve 170.772 g of magnesium chloride hexahydrate and 38.75 g of ammonium chloride in 200 ml of water, stir evenly to obtain an aqueous solution, wherein the content of magnesium chloride hexahydrate is 41.7% and the content of ammonium chloride is 9.5%. Place the raw material solution in a crystallizer and carry out vacuum evaporation crystallization under the conditions of a temperature of 75 °C, a vacuum degree of 0.08 MPa, and an evaporation rate of 0.05 kg / h. When the evaporated water reaches 120 g (i.e., the total evaporation of water accounts for 60% of the initial water content), start cooling, control the cooling rate at 25 °C / h until 25 °C. Then carry out crystal aging for 30 min, filter with medium-speed filter paper, and finally dry at a temperature of 50 °C for 1 h to obtain carnallite.

[0052] Example 3

[0053] The difference from Example 1 is only that:

[0054] When the evaporated water reaches 140 g, start cooling, control the cooling rate at 15 °C / h until 25 °C.

[0055] Example 4

[0056] The difference from Example 1 is only that:

[0057] Place the raw material solution in a crystallizer and carry out vacuum evaporation crystallization under the conditions of a temperature of 75 °C, a vacuum degree of 0.08 MPa, and an evaporation rate of 0.05 kg / h. When the evaporated water reaches 130 g, start cooling, control the cooling rate at 20 °C / h until 25 °C.

[0058] Example 5

[0059] The difference from Example 1 is only that:

[0060] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 42% and the content of ammonium chloride is 6%, and the balance is water.

[0061] Example 6

[0062] The difference from Example 1 is only that:

[0063] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 45% and the content of ammonium chloride is 8%, and the balance is water.

[0064] Example 7

[0065] The difference from Example 1 is only that:

[0066] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 45%, the content of ammonium chloride is 6%, and the balance is water.

[0067] Example 8

[0068] The difference from Example 1 is only that:

[0069] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 45%, the content of ammonium chloride is 8%, and the balance is water.

[0070] Example 9

[0071] The difference from Example 1 is only that:

[0072] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 43%, the content of ammonium chloride is 7%, and the balance is water.

[0073] Example 10

[0074] The difference from Example 1 is only that:

[0075] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 44%, the content of ammonium chloride is 8%, and the balance is water.

[0076] Example 11

[0077] The difference from Example 1 is only that:

[0078] The vacuum degree of vacuum evaporation crystallization is 0.09 MPa, and the cooling rate is 30 °C / h.

[0079] Example 12

[0080] The difference from Example 1 is only that:

[0081] The vacuum degree of vacuum evaporation crystallization is 0.05 MPa, and the cooling rate is 15 °C / h.

[0082] Example 13

[0083] The difference from Example 1 is only that:

[0084] Under the conditions of a temperature of 85 °C, a vacuum degree of 0.09 MPa, and an evaporation rate of 0.1 kg / h, vacuum evaporation crystallization is carried out until the evaporated water volume reaches 160 g (i.e., the total evaporation volume of water accounts for 80% of the initial water content).

[0085] Example 14

[0086] The difference from Example 1 is only that:

[0087] Under the conditions of a temperature of 85 °C, a vacuum degree of 0.07 MPa, and an evaporation rate of 0.02 kg / h, vacuum evaporation crystallization is carried out until the evaporation water volume reaches 150 g (that is, the total evaporation water volume accounts for 75% of the initial water content).

[0088] Example 15

[0089] The difference from Example 1 is only that:

[0090] The cooling rate is controlled at 15 °C / h, and the final cooling temperature is 25 °C.

[0091] Example 16

[0092] The difference from Example 1 is only that:

[0093] The cooling rate is controlled at 20 °C / h, and the final cooling temperature is 15 °C.

[0094] Example 17

[0095] The difference from Example 1 is only that:

[0096] Crystal growth is carried out for 3 h, and filtration is carried out using filter paper. Finally, drying is carried out at a temperature of 40 °C for 1.5 h to obtain ammonium carnallite.

[0097] Example 18

[0098] The difference from Example 1 is only that:

[0099] Crystal growth is carried out for 4 h, and filtration is carried out using filter paper. Finally, drying is carried out at a temperature of 40 °C for 2 h to obtain ammonium carnallite.

[0100] Example 19

[0101] The difference from Example 1 is only that:

[0102] 150 g of magnesium chloride hexahydrate and 24 g of ammonium chloride are dissolved in 200 ml of water, and stirred evenly to obtain an aqueous solution. Among them, the content of magnesium chloride hexahydrate is 40.1%, and the content of ammonium chloride is 6.4%. The raw material solution is placed in a crystallizer, and vacuum evaporation crystallization is carried out under the conditions of a temperature of 75 °C, a vacuum degree of 0.09 MPa, and an evaporation rate of 0.05 kg / h. When the evaporation water volume reaches 160 g (that is, the total evaporation water volume accounts for 80% of the initial water content), cooling is started, and the cooling rate is controlled at 15 °C / h until 25 °C. Subsequently, crystal growth is carried out for 3 h, and filtration is carried out using medium-speed filter paper. Finally, drying is carried out at a temperature of 50 °C for 1 h to obtain ammonium carnallite.

[0103] Example 20

[0104] The difference from Example 1 is only that:

[0105] Dissolve 180 g of magnesium chloride hexahydrate and 24 g of ammonium chloride in 200 ml of water, stir evenly to obtain an aqueous solution, wherein the content of magnesium chloride hexahydrate is 44.55% and the content of ammonium chloride is 6%. Place the raw material solution in a crystallizer and carry out vacuum evaporation crystallization under the conditions of a temperature of 75 °C, a vacuum degree of 0.09 MPa, and an evaporation rate of 0.05 kg / h. When the evaporated water reaches 160 g (i.e., the total evaporation of water accounts for 80% of the initial water content), start cooling, control the cooling rate at 20 °C / h until 25 °C. Subsequently, carry out crystal aging for 5 h, filter using medium-speed filter paper, and finally dry at a temperature of 50 °C for 1 h to obtain carnallite.

[0106] Comparative Example 1

[0107] The difference from Example 1 is only that:

[0108] The evaporation crystallization is carried out at atmospheric pressure.

[0109] Comparative Example 2

[0110] The difference from Example 1 is only that:

[0111] The cooling rate is 10 °C / h.

[0112] Comparative Example 3

[0113] The difference from Example 1 is only that:

[0114] The cooling rate is 35 °C / h.

[0115] Comparative Example 4

[0116] The difference from Example 1 is only that:

[0117] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 30% and the content of ammonium chloride is 10%, and the balance is water.

[0118] Comparative Example 5

[0119] The difference from Example 1 is only that:

[0120] In the raw material solution, the contents of magnesium chloride and ammonium chloride are different. Specifically, in the raw material solution, the content of magnesium chloride hexahydrate is 48% and the content of ammonium chloride is 3%, and the balance is water.

[0121] The test results of the performance parameters of the carnallite prepared in the above examples and comparative examples are shown in Table 1.

[0122] Test method:

[0123] Average particle size test and coefficient of variation test: The test is carried out by the screening method. Mainly, the particle samples are separated according to the particle size, and then the instrument is used to measure the number and mass of the particles in each separated particle size range, so as to obtain the data of different particle size distributions. The calculation formula of the coefficient of variation of particle size is: CV = μ / σ × 100%, where CV is the coefficient of variation, σ is the standard deviation of particle size, and μ is the average particle size.

[0124] Yield test: Weigh the product and calculate the yield.

[0125] Table 1

[0126]

[0127]

[0128] As can be seen from the above, the process parameters provided by the present invention have a significant optimization effect on the crystallization of carnallite. Through comparative experiments, it can be seen that different process conditions and parameter settings in the examples significantly improve the efficiency and yield of the crystallization process.

[0129] Compared with the comparative examples, after optimizing the process parameters in each embodiment of the present invention, not only the crystallization size of carnallite is increased, but also the morphology and uniformity of the product are significantly improved. Experiments prove that the optimized process conditions make the crystallization process more stable, thus reducing the aggregation phenomenon of particles and improving the quality of the product.

[0130] In addition, when the preferred process parameters proposed by the present invention are adopted, it can effectively promote the growth of crystals, so that the finally obtained carnallite particles have better dispersibility and larger particle size. At the same time, the optimized production process also significantly improves the purity of the product, which is of great significance for subsequent applications and market competition. In summary, the optimization of the process parameters of the present invention has broad application prospects and significant economic value.

[0131] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing ammonium carnallite, characterized in that: The following steps are involved: Step S1, vacuum evaporating and crystallizing the raw material solution to obtain a first crystal solution; the raw material solution comprises 35-45% of magnesium chloride hexahydrate, 4-10% of ammonium chloride and the balance of water by weight percentage; Step S2, cooling the first crystallization liquid to obtain a second crystallization liquid; Step S3, growing the second crystal solution to obtain the ammonium carnallite; Wherein, the vacuum degree of the vacuum evaporation crystallization is 0.05-0.09MPa; The cooling rate is 15-30°C / h.

2. The preparation method according to claim 1, characterized in that: In terms of weight percentage, the raw material solution includes 40-45% of the magnesium chloride hexahydrate, 5-8% of the ammonium chloride and the balance of water.

3. The preparation method according to claim 1 or 2, characterized in that: In the raw material solution, the weight ratio of the magnesium chloride hexahydrate to the ammonium chloride is (5-8):

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the step S1, The vacuum degree of the vacuum evaporation crystallization is 0.07-0.09 MPa; Preferably, the evaporation rate of the vacuum evaporation crystallization is 0.02-0.1 kg / h; and / or, The temperature of the vacuum evaporation crystallization is 70-85° C.; and / or, During the vacuum evaporation crystallization process, the total evaporation amount of water accounts for 30-80% of the initial water content; and / or, The solid content of the first crystallization liquid is 7-25%, and the average solid particle size is 1.5-30 mm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step S2, The cooling rate is 15-20°C / h; and / or, The cooling end point temperature is 15-27°C; and / or, The solid content of the second crystallization liquid is 70-80%, and the average solid particle size is 1.5-30 mm.

6. The preparation method according to any one of claims 1 to 5, characterized in that In the step S3, The crystal growing process is performed at a temperature of 15 to 27° C. for 0.5 to 5 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that The step S3 further includes filtering and drying the ammonium carnallite in sequence; Preferably, the drying temperature is 20-50° C. and the drying time is 0.5-12 h.

8. An ammonium carnallite, characterized in that: Obtained according to the preparation method of ammonium carnallite according to any one of claims 1 to 7.

9. The ammonium carnallite according to claim 8, characterized in that The purity of the ammonium carnallite is ≥ 90%; and / or, The average particle size of the ammonium carnallite is 1.5 to 30 mm; and / or, The yield of the ammonium carnallite is ≥80wt%; and / or, The coefficient of variation of the ammonium carnallite is ≤50%.

10. Use of the ammonium carnallite according to claim 8 or 9 in the production of anhydrous magnesium chloride.

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