A sylvite and a method for producing the same

Abstract

The application provides a carnallite and a production method thereof. The production method comprises the following steps: S1, mixing E halite and F halite to obtain a carnallite slurry; S2, performing first concentration on the carnallite slurry to obtain a semi-finished carnallite slurry; S3, performing dehydration on the semi-finished carnallite slurry to obtain a crude carnallite and a semi-finished mother liquor; S4, performing second concentration on the semi-finished mother liquor to obtain a semi-finished concentrated mother liquor, and recycling the semi-finished concentrated mother liquor to continue mixing with the E halite and the F halite, and repeating the steps S1 to S3 at least once; and simultaneously, performing decomposition crystallization on the crude carnallite to obtain the carnallite. The application can promote the growth of fine-crystal carnallite in the semi-finished concentrated mother liquor, increase the particle size of the fine-crystal carnallite, thereby avoiding the problem that the fine-crystal carnallite is completely melted by fresh water due to small particle size when meeting fresh water for washing in a crystallizer, and further improving the recovery rate of the carnallite.

Description

Technical Field

[0001] This invention relates to the field of potassium chloride production technology, and more specifically, to a carnallite and its production method. Background Technology

[0002] In the "halogenation-cold crystallization" process for potassium chloride production, the carnallite slurry produced after halogenation is dehydrated by a semi-finished product centrifuge and then enters the crystallizer for decomposition and crystallization. The mother liquor after dehydration by the semi-finished product centrifuge is called the semi-finished product mother liquor. The semi-finished product mother liquor contains small carnallite particles. When it is washed with fresh water in the crystallizer, the small carnallite particles are easily completely dissolved by the fresh water, resulting in a decrease in the recovery rate of carnallite.

[0003] The existing process returns the semi-finished mother liquor to the thickener and allows the fine carnallite particles to continue to grow by letting it stand in the saturated mother liquor. However, this method takes too long and the effect is not obvious in a short time, so it cannot promote production and thus the carnallite recovery rate is low. Summary of the Invention

[0004] The main objective of this invention is to provide a carnallite and its production method to solve the problem of low carnallite recovery rate in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for producing carnallite is provided, the method comprising: step S1, mixing E-halogen and F-halogen to obtain carnallite slurry; step S2, first concentrating the carnallite slurry to obtain semi-finished carnallite slurry; step S3, dehydrating the semi-finished carnallite slurry to obtain crude carnallite and semi-finished mother liquor; step S4, second concentrating the semi-finished mother liquor to obtain semi-finished concentrated mother liquor, recovering the semi-finished concentrated mother liquor, and continuing to mix it with E-halogen and F-halogen, repeating steps S1 to S3 at least once; simultaneously, decomposing and crystallizing the crude carnallite to obtain carnallite.

[0006] Furthermore, the mass concentration of fine-grained carnallite in the semi-finished product concentrate is 50-70%, and fine-grained carnallite represents carnallite with a particle size ≤700μm.

[0007] Furthermore, the grain size x of fine-grained carnallite includes: 60-65% below 400 μm; 30.73-15.11% of 400 < x ≤ 500 μm; 21.68-6.57% of 500 < x ≤ 600 μm; and 8.07-1.5% of 600 < x ≤ 700 μm.

[0008] Furthermore, the ratio of E-halogen to F-halogen is 1:1 to 1:1.3.

[0009] Furthermore, the E halogen contains: 23-27.5% MgCl2, 2-3.5% KCl, and 1-2.5% NaCl; preferably, the F halogen contains: 33-37% MgCl2 and 0.1-0.45% NaCl; preferably, the semi-finished mother liquor contains: 29-35% MgCl2, 18-25% KCl, and 14-15% NaCl.

[0010] Furthermore, the addition of brine is carried out using a brine adder; preferably, the first and second concentrations are carried out using a thickener; preferably, dehydration is carried out using a centrifuge; and preferably, decomposition and crystallization are carried out using a crystallizer.

[0011] Furthermore, the stirring speed during the brine mixing process is 30-50 r / min.

[0012] Furthermore, the temperature for adding the brine is 0–25°C, and the preferred time for adding the brine is 45–60 minutes.

[0013] Furthermore, the crude carnallite has a particle size greater than 600 μm.

[0014] To achieve the above objectives, according to one aspect of the present invention, a carnallite is provided, which is produced according to the production method described above in this application.

[0015] By applying the technical solution of this invention, this application concentrates the semi-finished mother liquor and then mixes the concentrated semi-finished concentrated mother liquor with E-halogen and F-halogen, which can promote the growth of fine-grained carnallite in the semi-finished concentrated mother liquor, increase the particle size of fine-grained carnallite, thereby avoiding the problem of the particles being completely dissolved by fresh water when they are washed in the crystallizer due to their small size, and thus improving the recovery rate of carnallite. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A flowchart of the method for producing carnallite according to the present invention is shown. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] In this application, the semi-finished mother liquor refers to the mother liquor obtained after dehydration of low-sodium carnallite produced after brine dilution. Fine-grained carnallite refers to the solid phase carnallite present in the semi-finished mother liquor after dehydration. The semi-finished concentrated mother liquor refers to the mother liquor after concentrating the semi-finished mother liquor.

[0020] As analyzed in the background section, existing technologies typically return the semi-finished mother liquor to the thickener and allow the fine carnallite particles to continue growing by letting it stand in the saturated mother liquor. However, this method takes too long and its effects are not obvious in a short period of time, failing to promote production and resulting in a low carnallite recovery rate. To solve the above problems, this application provides a carnallite and a method for producing it.

[0021] In one typical embodiment of this application, a method for producing carnallite is provided, such as... Figure 1 As shown, the production method includes: step S1, mixing E brine and F brine to obtain carnallite slurry; step S2, first concentrating the carnallite slurry to obtain semi-finished carnallite slurry; step S3, dehydrating the semi-finished carnallite slurry to obtain crude carnallite and semi-finished mother liquor; step S4, second concentrating the semi-finished mother liquor to obtain semi-finished concentrated mother liquor, recovering the semi-finished concentrated mother liquor, and continuing to mix it with E brine and F brine, repeating steps S1 to S3; simultaneously, decomposing and crystallizing the crude carnallite to obtain carnallite.

[0022] This application promotes the growth of fine-grained carnallite in the semi-finished mother liquor by concentrating the semi-finished mother liquor and then mixing the concentrated semi-finished mother liquor with E-halogen and F-halogen. This increases the particle size of the fine-grained carnallite, thereby avoiding the problem of the particles being completely dissolved by fresh water when washed in the crystallizer due to their small size, and thus improving the recovery rate of carnallite.

[0023] In some embodiments, the mass concentration of fine-grained carnallite in the semi-finished concentrated mother liquor is 50-70%, where fine-grained carnallite represents carnallite with a particle size ≤700μm. If the mass concentration of fine-grained carnallite is below this range, it will overflow from the brine mixer; if the mass concentration is above this range, it will lead to space issues in the brine mixer, resulting in more fine-grained carnallite.

[0024] In some embodiments, the particle size x of fine-grained carnallite includes: 60-65% below 400 μm; 30.73-15.11% of 400 < x ≤ 500 μm; 21.68-6.57% of 500 < x ≤ 600 μm; and 8.07-1.5% of 600 < x ≤ 700 μm. Since most of the fine-grained carnallite particles in the semi-finished mother liquor are less than 600 μm, they are easily and completely dissolved by fresh water during washing in the crystallizer, thus affecting the recovery rate.

[0025] In order to precipitate carnallite as much as possible, in some embodiments, the ratio of E halide to F halide is 1:1 to 1:1.3.

[0026] This application does not impose any particular restrictions on E-halides and F-halides; commonly used E-halides and F-halides in the art can be applied to this application. The E-halide contains: 23-27.5% MgCl2, 2-3.5% KCl, and 1-2.5% NaCl; preferably, the F-halide contains: 33-37% MgCl2 and 0.1-0.45% NaCl; preferably, the semi-finished mother liquor contains: 29-35% MgCl2, 18-25% KCl, and 14-15% NaCl.

[0027] There are no particular limitations on the equipment used in this application; any commonly used devices in the art can be applied to this application. In some embodiments, brine mixing is performed using a brine mixing device; preferably, the first and second concentrations are performed using a thickener; preferably, dehydration is performed using a centrifuge; and preferably, decomposition and crystallization are performed using a crystallizer.

[0028] In crystallization theory, factors affecting crystal growth rate include:

[0029] 1. Impurities: They alter the characteristics of the retention layer at the interface between the crystal and the solution, affecting the growth of solute into the crystal, changing the shape of the crystal, and slowing down crystal growth due to the adsorption of impurities.

[0030] 2. Stirring: Accelerates crystal growth and the formation of crystal nuclei;

[0031] 3. Temperature: Promotes the rate of surface chemical reactions and increases the crystallization rate.

[0032] This application promotes the growth of fine-grained carnallite by adding the semi-finished concentrated mother liquor to the crystallization zone of the brine mixer, utilizing the mixer's stirring power and saturated area. In some embodiments, the stirring speed during the brine mixing process is 30–50 r / min. Based on the above theory, the applicant discovered through extensive experiments that within the above-mentioned stirring speed range, continuous stirring in the supersaturated solution causes the fine-grained carnallite to continuously adsorb and crystallize, gradually growing larger, resulting in a faster crystal growth rate. Simultaneously, after centrifugation by a two-stage pusher centrifuge, the fine-grained carnallite, along with the supersaturated mother liquor water, is discharged into the crystallization zone of the brine mixer, preventing it from entering the central cylinder of the mixer. This prevents the fine-grained particles from being broken by friction against the walls due to secondary collisions within the central cylinder, resulting in even smaller particles. Excessive rotation speed can cause collisions between carnallite particles, producing more fine-grained carnallite, but it can also prevent the carnallite crystal nuclei from growing.

[0033] To further improve the growth rate of fine-grained carnallite, in some embodiments, the brine mixing temperature is 0–25°C, and the mixing time is 45–60 min. The mixing temperature affects the solubility of the brine; the higher the temperature, the faster the evaporation and the higher the saturation of the brine, thus achieving a co-saturated state and improving the recovery rate. The lower the mixing temperature, the longer the required mixing time.

[0034] In some embodiments, the particle size of crude carnallite is greater than 600 μm. Particles larger than 600 μm are controlled to enter the crystallizer system using a centrifuge. At this particle size, crystallization is more efficient within the crystallizer system, preventing dissolution by contact with fresh water within the crystallizer.

[0035] In another typical embodiment of this application, a carnallite is provided, which is produced according to the above-described production method.

[0036] The carnallite prepared by the above production method has a good recovery rate.

[0037] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0038] Example 1

[0039] At a brine mixing ratio of 1:1.12, 1000 mL of brine E and 1120 mL of brine F were mixed at 15°C for 45 minutes. Then, within 3 minutes, 60 mL of the 60% semi-finished product concentration mother liquor was added to every 1000 mL of brine E. The mixture was then stirred thoroughly at 40 rpm for 10 minutes. Figure 1 The process shown yields carnallite.

[0040] Example 2

[0041] Mix 1000 mL of brine E with 1300 mL of brine F at a ratio of 1:1.3. The mixing temperature is 15℃, and the mixing time is 45 minutes. Then, add the semi-finished product concentration mother liquor within 3 minutes. Add 60 mL of 70% semi-finished product concentration mother liquor to every 1000 mL of brine E, and stir thoroughly at 50 rpm for 10 minutes. Figure 1 The process shown yields carnallite.

[0042] Example 3

[0043] Mix 1000 mL of brine E with 1120 mL of brine F at a ratio of 1:1.12. The mixing temperature is 15℃ and the mixing time is 45 min. Then, add the semi-finished product concentration mother liquor within 3 minutes. Add 60 mL of 60% semi-finished product concentration mother liquor to every 1000 mL of brine E, and stir thoroughly at 60 r / min for 10 minutes to obtain carnallite.

[0044] Example 4

[0045] Mix 1000 mL of E brine with 1120 mL of F brine at a ratio of 1:1.12. After mixing the brine at 30°C, add the semi-finished product concentration mother liquor 3 minutes later. Add 60 mL of 60% semi-finished product concentration mother liquor to every 1000 mL of E brine, and stir thoroughly at 30 r / min for 10 minutes to obtain carnallite.

[0046] Example 5

[0047] Mix 1000 mL of brine E with 1120 mL of brine F at a ratio of 1:1.12. The mixing temperature is 15℃ and the mixing time is 45 min. Then, add the semi-finished product concentration mother liquor within 3 minutes. Add 60 mL of 80% semi-finished product concentration mother liquor to every 1000 mL of brine E, and stir thoroughly at 30 r / min for 10 minutes to obtain carnallite.

[0048] Example 6

[0049] Mix 1000 mL of brine E with 1120 mL of brine F at a ratio of 1:1.12. The mixing temperature is 15℃ and the mixing time is 45 min. Then, add the semi-finished product concentration mother liquor within 3 minutes. Add 60 mL of 40% semi-finished product concentration mother liquor to every 1000 mL of brine E, and stir thoroughly at 30 r / min for 10 minutes to obtain carnallite.

[0050] Comparative Example 1

[0051] Mix 1000 mL of brine E with 1120 mL of brine F at a brine ratio of 1:1.12 and stir thoroughly for 10 minutes to obtain carnallite.

[0052] Comparative Example 2

[0053] 100g of fine-grained carnallite was placed in the mother liquor of a thickener, allowed to stand for 2 hours, then dehydrated, dried, and then subjected to particle size analysis.

[0054] Table 3 shows the particle size comparison of fine-grained carnallite before and after being added to the mother liquor.

[0055] Table 1

[0056] <![CDATA[MgCl2]]> KCl NaCl Weighing E-halogen 24.91 3.01 2.22 / F-halogen 35.03 / 0.04 / Example 1 32.97 24.16 2.72 250g Example 2 32.88 24.08 2.92 255g Example 3 33.08 23.94 2.44 248g Example 4 32.71 23.91 2.79 252g Example 5 32.83 23.84 2.68 267g Example 6 32.61 23.91 2.84 242g Comparative Example 1 33.08 24.01 2.51 200g

[0057] The carnallite obtained from the above embodiments and Comparative Example 1 was dried and its particle size was compared, as shown in Table 2.

[0058] Table 2

[0059] Particle size Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 600μm 12.4％ 4.5％ 3.1％ 4.9％ 3.8％ 6.7％ 3.6％ 500μm 19.4％ 14.3％ 12.1％ 12.5％ 13.2％ 15.6％ 13.8％ 400μm 20.4％ 14.8％ 11.9％ 14.7％ 13.1％ 17.2％ 13.7％ Below 400μm 47.7％ 66.4％ 72.9％ 67.9％ 69.9％ 60.5％ 68.8％

[0060] According to the comparison between Example 1 and Comparative Example 1, it can be seen that after the semi-finished mother liquor is concentrated, it is brought back into the saturation range and subjected to stirring power, which can improve the particle size of the carnallite obtained after the overall brine reaction, reducing the proportion of carnallite below 400μm from 68.8% to 47.7%, increasing the yield of qualified carnallite, which is beneficial to production.

[0061] Table 3

[0062] Particle size Before inserting After putting it in 800μm 0％ 0％ 710μm 1.50％ 1.53％ 600μm 6.57％ 6.64％ 500μm 15.11％ 15.32％ 400μm 15.62％ 15.93％ Below 400μm 61.20％ 60.58％

[0063] The data in each embodiment and Comparative Example 1 were measured in experiments, while Comparative Example 2 was obtained in the workshop production process. Since the conditions for their generation are different, they cannot be directly compared; only comparisons within the same group of experiments are possible. According to Comparative Example 2, the fine-grained carnallite in the semi-finished mother liquor only undergoes static growth in saturated mother liquor, but the time required is too long, and the effect is not obvious in a short period, failing to promote production.

[0064] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: By concentrating the semi-finished mother liquor and then mixing the concentrated semi-finished concentrated mother liquor with E-halogen and F-halogen, the present application can promote the growth of fine-grained carnallite in the semi-finished concentrated mother liquor, thereby increasing the particle size of the fine-grained carnallite. This avoids the problem of the particles being completely dissolved by fresh water when they are washed in the crystallizer due to their small size, and thus improves the recovery rate of carnallite.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing carnallite, characterized in that, The production method includes: Step S1: Mix E brine and F brine to obtain carnallite slurry; the stirring speed during the mixing process is 30~50 r / min. Step S2: The carnallite slurry is first concentrated to obtain a semi-finished carnallite slurry. Step S3: Dehydrate the semi-finished carnallite slurry to obtain crude carnallite and semi-finished mother liquor; Step S4: The semi-finished product mother liquor is concentrated a second time to obtain a semi-finished product concentrated mother liquor. The semi-finished product concentrated mother liquor is recovered and mixed with the E halide and the F halide. 60 mL of the semi-finished product concentrated mother liquor is added to every 1000 mL of the E halide. Steps S1 to S3 are repeated at least once. The mass concentration of fine-grained carnallite in the semi-finished product concentrated mother liquor is 50-70%, and the fine-grained carnallite represents carnallite with a particle size ≤700 μm. Simultaneously, the crude carnallite is decomposed and crystallized to obtain the carnallite.

2. The production method according to claim 1, characterized in that, The grain size x of the fine-grained carnallite includes: Below 400μm, 60-65%; 400<x≤500μm 30.73~15.11%; 500<x≤600μm 21.68~6.57%; 600<x≤700μm 8.07~1.5%.

3. The production method according to claim 1, characterized in that, The ratio of the E-halogen to the F-halogen is 1:1 to 1:1.

3.

4. The production method according to any one of claims 1 to 3, characterized in that, The E-halogen contains: MgCl2 23~27.5%, KCl 2~3.5%, and NaCl 1~2.5%.

5. The production method according to any one of claims 1 to 3, characterized in that, The F-halogen contains: 33-37% MgCl2 and 0.1-0.45% NaCl.

6. The production method according to any one of claims 1 to 3, characterized in that, The semi-finished mother liquor contains: MgCl2 29~35%, KCl 18~25%, NaCl 14~15%.

7. The production method according to any one of claims 1 to 3, characterized in that, The addition of brine is performed using a brine adder; and / or, the first concentration and the second concentration are performed using a thickener; and / or, the dehydration is performed using a centrifuge; and / or, the decomposition and crystallization are performed using a crystallizer.

8. The production method according to any one of claims 1 to 3, characterized in that, The temperature for adding the brine is 0~25℃, and / or the time for adding the brine is 45~60min.

9. The production method according to any one of claims 1 to 3, characterized in that, The crude carnallite has a particle size greater than 600 μm.

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