Potassium chloride halvex - cold crystallization production method

Abstract

The application provides a method for producing potassium chloride by mixing halogen and cold crystallization. The method mixes raw material E halogen and raw material F halogen, and then adds circulating seeds to perform primary halogen mixing to obtain primary halogen mixing slurry. The primary halogen mixing slurry is sequentially concentrated and centrifuged to obtain semi-finished product mother liquor and carnallite. The carnallite is crystallized and dried to obtain potassium chloride. The semi-finished product mother liquor is concentrated and mixed with primary halogen completion liquid, raw material F halogen, fine crystal carnallite mother liquor and circulating seeds to perform secondary halogen mixing. The raw material F halogen, the raw material E halogen and the circulating seeds can be self-made by artificial method. The method can improve the yield of potassium chloride, increase the diversity of halogen water raw material sources, greatly reduce the cost, and the overall potassium chloride recovery rate of the process can reach more than 75%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of potassium chloride production, in particular to a halogen mixing-cold crystallization production method of potassium chloride. BACKGROUND

[0002] In the production process of potassium chloride, the halogen mixing-cold crystallization process is a relatively advanced production process, which has low production cost and good economic benefit. The process directly uses ore-forming brine, i.e. E point (saturated point of sodium chloride, potassium chloride and carnallite) brine, and mixes it with F point (saturated point of magnesium chloride, sodium chloride and carnallite) brine to produce low-sodium carnallite, and then decomposes the high-quality low-sodium carnallite to obtain high-quality potassium chloride.

[0003] The process has outstanding advantages, but also obvious shortcomings:

[0004] 1. The raw material, i.e. the original brine, has high requirements. Only when the floatation workshop discharges the production completed liquid can it be suitable for production, and it cannot be independently produced, so it is not suitable for large-scale production and has certain application limitations.

[0005] 2. The potassium recovery rate is lower than that of other potassium chloride production processes. The halogen mixing process is a process of handling a large amount of liquid, and the solid content of the slurry is low. The recovery rate of potassium chloride in the low-sodium carnallite intermediate product in the halogen mixing stage is generally only about 51.91%, and the remaining about 48% is discharged from the process system, which causes great waste.

[0006] 3. High cost. The F brine is discharged from the salt field after the ore is dried, and the concentration is increased after drying. The content of magnesium chloride in the brine is greatly increased to obtain a saturated liquid containing high-concentration magnesium chloride. In order to obtain qualified F brine, a large area of brine beach is needed for the process, and the cleaning and maintenance cost is high. SUMMARY

[0007] The main purpose of the present application is to provide a halogen mixing-cold crystallization production method of potassium chloride, so as to solve at least one of the problems of the prior art, i.e. the large raw material limitation, the low potassium recovery rate and the high production cost.

[0008] In order to achieve the above object, according to one aspect of the present application, a method for producing potassium chloride by halogen exchange-cold crystallization is provided, comprising the following steps: step S1, mixing raw material E halogen and raw material F halogen to obtain a primary halogen exchange raw material solution, then adding circulating seed crystals to perform primary halogen exchange to obtain a primary halogen exchange completion liquid and a primary halogen exchange slurry; step S2, sequentially performing thickening and semi-product centrifugation on the primary halogen exchange slurry to obtain a semi-product mother liquor and carnallite; step S3, performing crystallization and drying on the carnallite to obtain potassium chloride; performing semi-product thickening on the semi-product mother liquor to obtain fine crystal carnallite mother liquor and semi-product thickening overflow, mixing the semi-product thickening overflow with the primary halogen exchange completion liquid to obtain halogen exchange water; mixing the raw material F halogen with the halogen exchange water to obtain a secondary halogen exchange raw material solution, then adding the fine crystal carnallite mother liquor and the circulating seed crystals to perform secondary halogen exchange to obtain a secondary halogen exchange completion liquid; wherein the raw material F halogen can be artificial F halogen, which is prepared by the following method: adding water and F halogen salt pool magnesium chloride tailings to the raw material F halogen to perform dissolution to obtain the artificial F halogen; wherein the raw material E halogen can be artificial E halogen, which is prepared by the following method: using the secondary halogen exchange completion liquid to dissolve the positive flotation tailings, the reverse flotation tailings and the sodium salt pool tailings in the halogen water salt pool respectively, and then drying the positive flotation tailings dissolution raw halogen water, the reverse flotation tailings dissolution raw halogen water and the sodium salt pool tailings dissolution raw halogen water respectively to obtain the artificial E halogen; wherein the circulating seed crystals are prepared by the following method: mixing the raw material F halogen with the primary halogen exchange completion liquid to perform circulating seed crystal halogen exchange to obtain the circulating seed crystals.

[0009] Further, in step S1, the volume ratio of the raw material E halogen to the raw material F halogen is 1:(1-1.3); preferably, 30-50g of the circulating seed crystals is added to every 1000ml of the primary halogen exchange raw material solution.

[0010] Further, in step S2, the semi-product mother liquor contains fine crystal carnallite with a mass concentration of 8-15wt%.

[0011] Further, in step S3, the mass concentration of the fine crystal carnallite mother liquor is 50-70wt%.

[0012] Further, in step S3, 50-70ml of the fine crystal carnallite mother liquor is added to every 1000ml of the secondary halogen exchange raw material solution.

[0013] Further, in step S3, 30-50g of the circulating seed crystals is added to every 1000ml of the secondary halogen exchange raw material solution.

[0014] Further, in the preparation process of the artificial F halogen, the amount of water added is 10-15wt% of the raw material F halogen, and the amount of F halogen salt pool magnesium chloride tailings added is excessive relative to the raw material F halogen.

[0015] Further, in the preparation process of artificial E brine, the solid-liquid ratio of the positive flotation tailings and the secondary brine mixing completion liquid is (10-12):1; and / or the solid-liquid ratio of the reverse flotation tailings and the secondary brine mixing completion liquid is (5-7):1; and / or the solid-liquid ratio of the sodium salt pool tailings and the secondary brine mixing completion liquid is (8-10):1.

[0016] Further, in the preparation process of the circulating seed, the volume ratio of the raw material F brine and the primary brine mixing completion liquid is 1:(1-1.3).

[0017] Further, the recovery rate of potassium chloride is greater than or equal to 75%.

[0018] The present application improves the existing potassium chloride "brine mixing-cold crystallization" process, which can increase the diversity of brine raw material sources while improving the recovery rate of potassium chloride, and greatly reduces the cost. On the one hand, based on the "brine mixing-cold crystallization" process, the artificial preparation of F brine and E brine is realized, which widens the source of brine raw materials, reduces the area of brine salt field, and reduces the maintenance cost of salt field cleaning. At the same time, the recovery and utilization of various potassium-containing tailings such as magnesium chloride tailings, reverse flotation tailings, positive flotation tailings, and sodium salt pool tailings can be realized, which directly reduces the production cost and can effectively improve the economic benefit. On the other hand, the newly added fine crystal carnallite recovery method, seed adding method, seed preparation method and brine mixing completion liquid recovery method can effectively improve the process index, and the total potassium chloride recovery rate of the process can reach more than 75%. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application given below, make an explanation of the application, and do not constitute an improper limitation of the application. In the drawings:

[0020] Figure 1 A flow chart of the potassium chloride "brine mixing-cold crystallization" process in an embodiment of the present application is shown;

[0021] Figure 2 A flow chart of the artificial modulation module of F brine in the potassium chloride "brine mixing-cold crystallization" process in an embodiment of the present application is shown;

[0022] Figure 3 A flow chart of the preparation module of the circulating seed in the potassium chloride "brine mixing-cold crystallization" process in an embodiment of the present application is shown; and

[0023] Figure 4 A flow chart of the tailings utilization module in the potassium chloride "brine mixing-cold crystallization" process in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0024] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] Unless otherwise specified, the "fine carnallite crystal" in the present application refers to a carnallite crystal with a D50 of less than 400 μm.

[0026] Unless otherwise specified, the "magnesium chloride tailings" in the present application refer to solid substances deposited due to supersaturation during the solar evaporation process of old brine (F brine).

[0027] Unless otherwise specified, the "positive flotation tailings" in the present application refer to solid substances deposited at the bottom after flotation of carnallite in the production process of the positive flotation process, and then discharged to the tail salt pool and spread to dry ore.

[0028] Unless otherwise specified, the "reverse flotation tailings" in the present application refer to a process opposite to the positive flotation process, in which potassium particles are deposited and other substances are floated away with water, discharged to the tail salt pool, and spread to dry ore.

[0029] Unless otherwise specified, the "sodium salt pool tailings" in the present application refer to the deposits in the process of spreading the original brine to the mineral brine.

[0030] As described in the background art, the prior art has the problems of great raw material limitation, low potassium chloride recovery rate, and high production cost. In order to solve the above problems, in a typical embodiment of the present application, a potassium chloride production method by mixing brine and cold crystallization is provided, which comprises the following steps: step S1, mixing raw material E brine with raw material F brine to obtain a first mixed brine, then adding a circulating seed crystal to perform a first mixing brine, to obtain a first mixed brine completion liquid and a first mixed brine slurry; step S2, sequentially performing thickening and semi-product centrifugation on the first mixed brine slurry to obtain a semi-product mother liquor and carnallite; and step S3, performing crystallization and drying on the carnallite to obtain potassium chloride.

[0031] Meanwhile, the semi-finished mother liquor is concentrated to obtain fine-crystal carnallite mother liquor and semi-finished concentrated overflow, the semi-finished concentrated overflow is mixed with the first halogen replacement completion liquid to obtain halogen replacement water, the raw material F halogen is mixed with the halogen replacement water to obtain secondary halogen replacement raw material liquid, then the fine-crystal carnallite mother liquor and the circulating seed crystal are added to perform secondary halogen replacement to obtain secondary halogen replacement completion liquid; wherein the raw material F halogen can be artificial F halogen, the artificial F halogen is prepared by adding water and F halogen salt pool magnesium chloride tailings into the raw material F halogen to perform dissolution to obtain the artificial F halogen; wherein the raw material E halogen can be artificial E halogen, the artificial E halogen is prepared by using the secondary halogen replacement completion liquid to dissolve the positive flotation tailings, the reverse flotation tailings and the sodium salt pool tailings in the halogen water salt pool respectively, and then the positive flotation tailings dissolution original halogen water, the reverse flotation tailings dissolution original halogen water and the sodium salt pool tailings dissolution original halogen water are dried to obtain the artificial E halogen; wherein the circulating seed crystal can be prepared by mixing the raw material F halogen with the first halogen replacement completion liquid to perform circulating seed crystal halogen replacement to obtain the circulating seed crystal.

[0032] As shown in Figures 1 to 4 The present application first mixes the raw material E halogen with the raw material F halogen, adds the circulating seed crystal into the first halogen replacement device to perform first halogen replacement to obtain first halogen replacement completion liquid and first halogen replacement slurry. In the halogen replacement reaction process of the halogen replacement device, nucleation is easy to burst under a high supersaturation degree, which leads to a high primary nucleation rate, and finally causes the coalescence of fine crystals, or generates needle-shaped, flaky crystals, and serious ones can generate amorphous particles. Therefore, the present application adds a certain amount of circulating seed crystal in the first halogen replacement process, which can effectively act as a crystallization core to promote the rapid aggregation and growth of carnallite crystals.

[0033] The first halogen replacement completion liquid is sent into the halogen replacement device, and the first halogen replacement slurry is sent into the first thickener to perform concentration to obtain first thickener slurry, which is sent into the semi-finished centrifuge to perform centrifugation. The carnallite produced after halogen replacement is dehydrated by the semi-finished centrifuge and then enters the crystallizer to perform decomposition and crystallization to obtain finished product liquid containing KCl crystals, which is sequentially sent into the finished product thickener, the finished product centrifuge and the finished product dryer to perform concentration, centrifugation and drying to obtain finished product KCl.

[0034] The mother liquor after dehydration of the semi-finished centrifuge is called semi-finished mother liquor, which contains a small amount of fine carnallite. The existing process returns this mother liquor to the first thickener to allow the fine carnallite particles to continue to grow in the saturated solution of the first thickener. However, the inventors unexpectedly found through experimental analysis in the research process that this method is low in efficiency and long in time. Therefore, the present application sends the semi-finished mother liquor into the semi-finished thickener to perform concentration to obtain fine-crystal carnallite mother liquor and semi-finished concentrated overflow, and sends the semi-finished concentrated overflow into the halogen replacement device to mix with the first halogen replacement completion liquid sent therein to obtain halogen replacement water.

[0035] Meanwhile, in order to ensure that the potassium in the first brine-replacement completion liquid is precipitated in the form of carnallite, the present application also sends the brine containing the same and the raw material F brine into a second brine-replacement device to perform a second brine-replacement reaction, and adds seed crystals and fine-crystal carnallite mother liquor in the process of brine replacement to quickly form crystal nuclei and promote the growth of crystals. Meanwhile, the stirring power of the second brine-replacement device and the supersaturation region are used to promote the growth of fine-crystal carnallite, so as to realize rapid crystallization and sedimentation, obtain second brine-replacement slurry and second brine-replacement completion liquid, and jointly crystallize the potassium ions in the first brine-replacement completion liquid into carnallite. Meanwhile, after the obtained fine-crystal carnallite mother liquor is concentrated and thickened, it is again sent into the brine-replacement process and enters the supersaturation region, is supported by the stirring power of the brine-replacement device, and stays in the supersaturation region for a longer time, so as to improve the particle size of the carnallite obtained after the overall brine-replacement reaction, increase the process yield by using a small amount of equipment, and increase the production capacity.

[0036] The obtained second brine-replacement slurry is returned to the first thickener for subsequent steps. The potassium content in the second brine-replacement completion liquid is small, and the magnesium content is high, so the second brine-replacement completion liquid can be used for the dissolution of potassium in the tailings of direct flotation, reverse flotation and sodium salt pool in the brine salt pool. Specifically, the second brine-replacement completion liquid and water are sent into a conditioning tank for mixing, and then are respectively sent into a dissolution tank with the tailings of direct flotation, reverse flotation and sodium salt pool for dissolution. After the dissolution slurry is solid-liquid separated, the recovery liquid of the tailings of direct flotation, reverse flotation and sodium salt pool after dissolution is obtained, which can meet the demand for preparing E brine, and after being respectively dried, artificial E brine can be obtained and returned to the process for reuse. The recovery liquid of the tailings of reverse flotation and sodium salt pool after dissolution can also be transported back to the salt field for use as solar evaporation brine, which increases the diversity of raw material brine sources, increases the amount of solar evaporation brine, and also takes into account the recycling of tail salt and tailings in potassium chloride production, achieving multiple purposes at once.

[0037] In addition, the raw material F brine can be prepared by the following method: the raw material F brine and water are sent into a conditioning tank, mixed uniformly, and then sent into a dissolution tank with excess F brine magnesium chloride tailings in the salt pool for dissolution. After solid-liquid separation, artificial F brine is obtained and returned to the process for reuse. The F brine is one of the two brine raw materials in the potassium chloride brine-replacement-cold crystallization process, and specifically refers to old brine that is just saturated with Bis after the preparation of sodium-containing carnallite (saturated with NaCl, Car and Bis). In the existing process, in order to solar evaporate the collected brine to the saturation brine at the F point, a large amount of solar evaporation area and a large amount of salt field storage brine are required, resulting in huge maintenance and cleaning costs. At the same time, due to the influence of air temperature on evaporation capacity, the process yield changes greatly, the production is unstable, and the yield fluctuates seriously. The present application uses the raw material F brine to add fresh water and then dissolve with the F brine magnesium chloride tailings cleaned out of the salt field, so as to artificially prepare qualified raw material F brine for application.

[0038] The application realizes artificial preparation of F brine and E brine in raw materials, broadens the source of brine raw materials, reduces the area of brine salt field and the maintenance cost of salt field cleaning; meanwhile, the recycling of various potassium-containing tailings such as magnesium chloride tailings, reverse flotation tailings, positive flotation tailings, sodium salt pool tailings and the like can be realized, which directly reduces the production cost and effectively improves the economic benefit.

[0039] In addition, in the existing production method of brine mixing-cold crystallization, the brine mixing completion liquid is directly discharged to the carnallite pool after being precipitated in the brine mixing completion liquid pool, which is the main factor of low KCl yield for the brine mixing-cold crystallization process. Therefore, the raw material F brine and the first brine mixing completion liquid are mixed in the circulating seed brine mixing device in the application to carry out the circulating seed brine mixing, and the brine mixing slurry is sent to the circulating seed thickener. The slurry after thickening is separated into solid and liquid, and the circulating seed is obtained and returned to the process for recycling. The first brine mixing completion liquid and the raw material F brine are used for secondary brine mixing, and a kind of sodium-containing carnallite (called circulating seed) is obtained. The particles of the carnallite are fine, and the settling is slow, which is not suitable for entering the crystallizer to produce potassium chloride, but can be concentrated and then enter the brine mixing process to play the role of seed, so as to promote the formation of stable large particle carnallite crystals in the brine mixing process.

[0040] The process of the brine mixing-cold crystallization production is scientifically designed in the application, and a small amount of equipment is added to improve the process yield, reduce the area of old brine salt field, increase the diversity of raw brine sources, and also take into account the recycling of tail salt and tailings in potassium chloride production. The new fine crystal carnallite recycling method, seed adding method, seed making method and brine mixing completion liquid recycling method can effectively improve the process index. The recovery rate of potassium chloride in the low-sodium carnallite intermediate product in the brine mixing stage is increased to about 85%, and the overall process recovery rate of potassium chloride can reach more than 75%. The problems of large raw material limitation, low potassium chloride recovery rate and high production cost in the existing brine mixing-cold crystallization process can be well solved.

[0041] In a preferred embodiment, in step S1, the volume ratio of raw material E brine to raw material F brine is 1:(1-1.3); preferably, 30-50g of circulating seed is added to 1000ml of first brine mixing raw liquid, so that a large amount of carnallite can be precipitated while the amount of seed added is minimized, and the production cost is further reduced. The specific amount of seed added can be adjusted adaptively according to the production temperature. When the production temperature is low, the amount of seed added is increased, and when the production temperature is high, the amount of seed added is reduced.

[0042] Specifically, in a preferred embodiment, in step S2, the semi-finished product mother liquor contains fine crystal carnallite with a mass concentration of 8-15wt%.

[0043] In a preferred embodiment, the mass concentration of the fine-crystal carnallite mother liquor in step S3 is 50-70wt%, so that the potassium ions can be more fully precipitated and crystallized, and the internal space is provided for the better growth of the crystal nucleus to a suitable size, thereby further improving the recovery rate of potassium chloride and reducing the production cost.

[0044] For the purpose of further reducing the production cost while improving the potassium ion precipitation effect, in a preferred embodiment, 50-70ml of the fine-crystal carnallite mother liquor is added to 1000ml of the secondary halogen recharge raw material solution in step S3.

[0045] Based on similar reasons, in a preferred embodiment, 30-50g of the circulating seed crystal is added to 1000ml of the secondary halogen recharge raw material solution in step S3.

[0046] For the purpose of further improving the preparation efficiency of artificial F halogen, thereby further reducing the production cost, in a preferred embodiment, the amount of water added in the preparation process of the artificial F halogen is 10-15wt% of the raw material F halogen, and the amount of the F halogen salt pond magnesium tailings added is excessive relative to the raw material F halogen.

[0047] In a preferred embodiment, in the preparation process of the artificial E halogen, the solid-liquid ratio of the positive flotation tailings to the secondary halogen recharge completion liquid is (10-12):1; and / or the solid-liquid ratio of the reverse flotation tailings to the secondary halogen recharge completion liquid is (5-7):1; and / or the solid-liquid ratio of the sodium salt pond tailings to the secondary halogen recharge completion liquid is (8-10):1, so that the potassium chloride in the tailings can be optimally precipitated, and the utilization rate of the tailings is improved. It can be understood that the solid-liquid ratio here refers to the ratio of the tailings mass (g) to the secondary halogen recharge completion liquid volume (ml), and if the potassium content of the tailings is high in the actual production process, the secondary dissolution can also be appropriately performed as needed.

[0048] For the purpose of further improving the preparation efficiency of the circulating seed crystal, in a preferred embodiment, in the preparation process of the circulating seed crystal, the volume ratio of the raw material F halogen to the primary halogen recharge completion liquid is 1:(1-1.3).

[0049] As described above, the halogen recharge-cold crystallization process of the present application can improve the KCl recovery rate, and in a preferred embodiment, the recovery rate of potassium chloride is ≥75%.

[0050] The present application will be further described in detail below in combination with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0051] Example 1

[0052] The halogen recharge-cold crystallization process flow chart is as followsFigure 1 Figure 1 shows a flow chart of the preparation of the artificial modulation module of the E halogen; Figure 2 shows a flow chart of the preparation of the artificial modulation module of the F halogen; Figure 3 shows a flow chart of the preparation of the circulating seed; Figure 4 shows a flow chart of the utilization of the tailings; and Figure 5 shows a flow chart of the utilization of the tailings. Figure 2 Figure 1 shows a flow chart of the preparation of the artificial modulation module of the E halogen; Figure 2 shows a flow chart of the preparation of the artificial modulation module of the F halogen; Figure 3 shows a flow chart of the preparation of the circulating seed; Figure 4 shows a flow chart of the utilization of the tailings; and Figure 5 shows a flow chart of the utilization of the tailings. Figure 3 Figure 1 shows a flow chart of the preparation of the artificial modulation module of the E halogen; Figure 2 shows a flow chart of the preparation of the artificial modulation module of the F halogen; Figure 3 shows a flow chart of the preparation of the circulating seed; Figure 4 shows a flow chart of the utilization of the tailings; and Figure 5 shows a flow chart of the utilization of the tailings. Figure 4

[0053] Step S1, the raw material E halogen and the raw material F halogen are mixed, and the circulating seed is added (37 g of circulating seed is added per 1000 ml of the mixed solution of the raw material E halogen and the raw material F halogen) to a primary halogen replacement device for primary halogen replacement, to obtain a primary halogen replacement completion solution and a primary halogen replacement slurry; the primary halogen replacement completion solution is sent to a halogen recovery device; and the components of each raw material and product are shown in Table 1.

[0054] Table 1

[0055] Primary halogen conversion - component content wt% MgCl2 KCl NaCl Amount used Raw material E halogen 25.61 2.87 2.57 1000ml Raw material F halogen 34～36 / 0.1～1.1 1120ml Recycled seed 32.1 22.32 8.71 78g Primary halogen conversion completion liquid 28～31 0.5～1 0.7～1.5 / Primary halogen conversion slurry 31～34 20～25 3～12 /

[0056] Step S2, the primary halogen replacement slurry is sent to a primary thickener for thickening, to obtain a primary thickening slurry, which is sent to a semi-product centrifuge for centrifugation, to obtain a semi-product mother liquor and a carnallite, and the mass concentration of fine crystal carnallite in the semi-product mother liquor is 10 wt%.

[0057] Step S3, the carnallite is sent to a crystallizer for decomposition crystallization, to obtain a solution containing KCl crystals, which is sent to a product thickener, a product centrifuge and a product dryer in sequence for thickening, centrifugation and drying, to obtain a product KCl, with a yield of 85% and a purity of 99%.

[0058] The semi-product mother liquor is sent to a semi-product thickener for thickening, to obtain a fine crystal carnallite mother liquor with a mass concentration of 60 wt% and a semi-product thickener overflow, and the semi-product thickener overflow is sent to the halogen recovery device to be mixed with the primary halogen replacement completion solution sent thereto, to obtain a halogen recovery water; and the raw material F halogen, the halogen recovery water, the fine crystal carnallite mother liquor and the circulating seed are sent to a secondary halogen replacement device, 60 ml of the fine crystal carnallite mother liquor and 40 g of the circulating seed are added per 1000 ml of the raw material F halogen and the halogen recovery water, for secondary halogen replacement, to obtain a secondary halogen replacement slurry and a secondary halogen replacement completion solution; and the components of each raw material and product are shown in Table 2.

[0059] Table 2

[0060] Secondary halogen conversion - component content wt% MgCl2 KCl NaCl Raw material F halogen 34～36 / 0.1～1.1 Recycled seed 32.1 22.32 8.71 Secondary halogen conversion completion liquid 32.5～33.5 0.03～0.10 0.2～1.2

[0061] The secondary halogen replacement slurry is returned to the primary thickener; the secondary halogen replacement completion solution and water are mixed in a conditioning tank, and then sent to a dissolution tank together with the positive flotation tailings, the reverse flotation tailings and the sodium salt pool tailings for leaching, to obtain a recovery solution of the positive flotation tailings leaching original halogen water, a recovery solution of the reverse flotation tailings leaching original halogen water and a recovery solution of the sodium salt pool tailings leaching original halogen water, respectively, after solid-liquid separation of the leaching slurry; and after drying, an artificial E halogen is obtained, which is returned to the process as the raw material E halogen for reuse; and the components of each raw material and product are shown in Tables 3 to 4.​

[0062] Table 3

[0063]

[0064] Table 4

[0065]

[0066]

[0067] The raw material F halogen and water corresponding to 10wt% thereof are fed into an adjusting tank, mixed uniformly, and then fed into a dissolving tank with excess F halogen salt pool magnesium chloride tailings to be dissolved and extracted, and after solid-liquid separation, artificial F halogen is obtained, which is returned to the process as raw material F halogen for reuse; the compositions of each raw material and product are shown in Table 5.

[0068] Table 5

[0069] Artificial F halogen preparation - component content wt% MgCl2 KCl NaCl Raw material F halogen 34～36 / 0.1～1.1 Magnesium chloride tailings 41.53 2.89 6.35 Artificial F halogen 35.32 / 0.02

[0070] The raw material F halogen and the first halogen replacement completion liquid are mixed in a circulating seed replacement halogenator at a volume ratio of 1:1.2, and the circulating seed replacement halogenation is carried out, and the replacement halogen slurry is fed into a circulating seed thickener, and after the thickened slurry is separated, the circulating seed is obtained, which is returned to the process for reuse; the compositions of each raw material and product are shown in Table 6.

[0071] Table 6

[0072] Recycled seed preparation - component content wt% MgCl2 KCl NaCl Particle size Raw material F halogen 34～36 / 0.1～1.1 / Primary halogen conversion completion liquid 28～31 0.5～1 0.7～1.5 / Recycled seed 29.5～32.5 21～24 3～12 < 400 μm

[0073] The overall potassium chloride recovery rate of the process of Example 1 is 80%.

[0074] Example 2 Effect verification 1 of recycled seed

[0075] The difference from Example 1 is that no circulating seed is added in step S1. The amount of carnallite deposited in the first halogen replacement process is measured, and the data is shown in Table 7.

[0076] Table 7

[0077]

[0078]

[0079] As can be seen from the above, by adding the circulating seed of the present application, the formation of stable large particle crystals can be promoted, the carnallite settlement is promoted, and the KCl recovery rate is further improved.

[0080] Example 3 Effect verification 2 of recycled seed

[0081] 1st experiment: the raw material E halogen and the raw material F halogen are mixed to carry out halogen mixing, stirring for 10 minutes, to obtain No. 1 overflow and No. 1 carnallite, and the experimental data analysis results are shown in Table 8.

[0082] 2nd experiment: the once halogen mixing completion liquid and the raw material F halogen are mixed to carry out halogen mixing, stirring for 10 minutes, and adding crystal seeds in the halogen mixing process, to obtain No. 2 overflow and No. 2 carnallite, and the experimental data analysis results are shown in Table 9.

[0083] Table 8

[0084]

[0085] Table 9

[0086]

[0087] From the comparison results of the settling time, the settling speed after adding the circulating crystal seeds of the application is reduced by nearly half the time of the conventional halogen mixing, which also shows that after adding the circulating crystal seeds, the circulating crystal seeds effectively become crystal nuclei, so that the crystal grows rapidly and effectively inhibits the explosion of secondary crystal nuclei.

[0088] From the comparison results of the components, it can be seen from the No. 2 overflow that the once halogen mixing completion liquid can be halogen mixed again for recovery, and the overflow after the second recovery has only a very small potassium content, and the yield can reach more than 85%, which can completely re-enter the production system to produce potassium chloride.

[0089] In summary, the K content in the once halogen mixing completion liquid is too low, and generally cannot be used as halogen mixing raw material. However, by adding the circulating crystal seeds of the application, the rapid and large-scale settling of carnallite can be realized, and the K recovery rate can be improved, so the circulating crystal seeds of the application can play a good role in promoting the settling of carnallite.

[0090] Example 4 Effect verification of fine crystal carnallite mother liquor

[0091] 3rd experiment: the raw material E halogen and the raw material F halogen are mixed to carry out halogen mixing, stirring for 10 minutes, to obtain No. 3 carnallite, and the experimental data analysis results are shown in Table 10.

[0092] 4th experiment: the raw material E halogen and the raw material F halogen are mixed to carry out halogen mixing, 60ml of fine crystal carnallite mother liquor with a concentration of 60wt% (per 1000ml) is added 3 minutes after halogen mixing, stirring for 10 minutes, to obtain No. 4 carnallite; and the experimental data analysis results are shown in Table 11.

[0093] Table 10

[0094] Experiment 3 - component content wt% MgCl2 KCl NaCl Weighing Raw material E halogen 24.91 3.01 2.22 / Raw material F halogen 35.03 / 0.04 / Carnallite 3 33.08 24.01 2.51 200g

[0095] Table 11

[0096] Experiment 4 - component content wt% MgCl2 KCl NaCl Weighing Raw material E halogen 24.91 3.01 2.22 / Raw material F halogen 35.03 / 0.04 / Carnallite 4 32.97 24.16 2.72 250g

[0097] After drying, the particle size of No. 3 and No. 4 carnallite was compared, and the results are shown in Table 12.

[0098] Table 12

[0099]

[0100]

[0101] The above experiments show that when the fine carnallite mother liquor of the present invention is reintroduced into the brine mixing process, the particle size of the carnallite obtained after the overall brine mixing reaction can be improved, reducing the content of carnallite below 400 μm from 68.8% to 47.7%, increasing the yield of qualified carnallite with larger particle size, which is beneficial to the efficient production of KCl in the subsequent process and further improving its yield and purity.

[0102] Example 5

[0103] The difference from Example 1 is that in step S1, the volume ratio of raw material E brine to raw material F brine is 1:1, and 30g of recycled seed crystals are added to every 1000ml of brine raw material solution; in step S2, the semi-finished mother liquor contains fine-grained carnallite with a mass concentration of 8wt%; in step S3, the mass concentration of fine-grained carnallite mother liquor is 50wt%, and 70ml of fine-grained carnallite mother liquor and 50g of recycled seed crystals are added to every 1000ml of brine raw material solution for secondary brine preparation.

[0104] In the preparation of artificial F-halogen, the amount of water added is 10 wt% of the raw material F-halogen; in the preparation of artificial E-halogen, the solid-liquid ratio of the positive flotation tailings to the secondary brine finishing liquid is 10:1, the solid-liquid ratio of the reverse flotation tailings to the secondary brine finishing liquid is 5:1, and the solid-liquid ratio of the sodium salt pond tailings to the secondary brine finishing liquid is 8:1; in the preparation of recycled seed crystals, the volume ratio of the raw material F-halogen to the primary brine finishing liquid is 1:1.

[0105] In Example 5, the overall potassium chloride recovery rate of the process was 75%.

[0106] Example 6

[0107] The difference from Example 1 is that in step S1, the volume ratio of raw material E brine to raw material F brine is 1:1.3, and 50g of recycled seed crystals are added to every 1000ml of brine raw material solution; in step S2, the semi-finished mother liquor contains fine-grained carnallite with a mass concentration of 15wt%; in step S3, the mass concentration of fine-grained carnallite mother liquor is 70wt%, and 50ml of fine-grained carnallite mother liquor and 30g of recycled seed crystals are added to every 1000ml of brine raw material solution for secondary brine preparation.

[0108] In the preparation process of artificial F brine, the amount of water added is 15wt% of the raw material F brine; in the preparation process of artificial E brine, the solid-liquid ratio of the positive flotation tailings and the secondary brine completion liquid is 12:1, the solid-liquid ratio of the reverse flotation tailings and the secondary brine completion liquid is 7:1, and the solid-liquid ratio of the sodium salt pool tailings and the secondary brine completion liquid is 10:1; in the preparation process of the circulating seed crystal, the volume ratio of the raw material F brine and the primary brine completion liquid is 1:1.3.

[0109] The overall potassium chloride recovery rate of the process of example 6 is 76%.

[0110] As can be seen from the above, the present application improves the existing potassium chloride "brine - cold crystallization" process, which can increase the potassium chloride recovery rate while increasing the diversity of brine raw material sources and greatly reducing the cost. On the one hand, based on the "brine - cold crystallization" process, the artificial preparation of F brine and E brine is realized, which widens the source of brine raw materials, reduces the area of brine salt field, and reduces the maintenance cost of salt field cleaning. At the same time, it can also realize the recycling of various potassium-containing tailings such as magnesium chloride tailings, reverse flotation tailings, positive flotation tailings, sodium salt pool tailings, etc., directly reducing the production cost and effectively improving the economic benefit. On the other hand, the new fine crystal carnallite recovery method, seed crystal adding method, seed crystal making method and brine completion liquid recovery method can effectively improve the process index, and the overall potassium chloride recovery rate of the process can reach more than 75%.

[0111] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing potassium chloride by cold crystallization of brine, characterized in that, The method comprises the following steps: Step S1, mixing raw material E halogen and raw material F halogen to obtain a primary halogen replacement raw material solution, then adding circulating seed crystals, performing primary halogen replacement, and obtaining a primary halogen replacement completion solution and a primary halogen replacement slurry; the volume ratio of the raw material E halogen to the raw material F halogen is 1: (1-1.3), and 30-50 g of the circulating seed crystals is added per 1000 ml of the primary halogen replacement raw material solution; Step S2, sequentially performing thickening and semi-product centrifugation on the primary halogen replacement slurry to obtain a semi-product mother liquor and carnallite; Step S3, performing crystallization and drying on the carnallite to obtain potassium chloride; performing semi-product thickening on the semi-product mother liquor to obtain fine-crystal carnallite mother liquor and semi-product thickening overflow, mixing the semi-product thickening overflow and the primary halogen replacement completion solution to obtain back halogen water, mixing the raw material F halogen and the back halogen water to obtain a secondary halogen replacement raw material solution, then adding 50-70 ml of the fine-crystal carnallite mother liquor and 30-50 g of the circulating seed crystals per 1000 ml of the secondary halogen replacement raw material solution, performing secondary halogen replacement, and obtaining a secondary halogen replacement completion solution; wherein the raw material F halogen is artificial F halogen, and the artificial F halogen is prepared by the following method: adding water and F halogen salt pool magnesium chloride tailings into the raw material F halogen, and performing dissolution to obtain the artificial F halogen; wherein the raw material E halogen is artificial E halogen, and the artificial E halogen is prepared by the following method: respectively performing dissolution on the positive flotation tailings, the reverse flotation tailings and the sodium salt pool tailings in the halogen water salt pool by using the secondary halogen replacement completion solution, and respectively performing drying on the obtained positive flotation tailings dissolution original halogen water, the reverse flotation tailings dissolution original halogen water and the sodium salt pool tailings dissolution original halogen water to obtain the artificial E halogen; wherein the circulating seed crystals are prepared by the following method: mixing the raw material F halogen and the primary halogen replacement completion solution, performing circulating seed crystal halogen replacement, and obtaining the circulating seed crystals.

2. The production method according to claim 1, characterized by, In the step S2, the semi-product mother liquor contains fine-crystal carnallite with a mass concentration of 8-15 wt%.

3. The production method according to claim 1 or 2, characterized by, In the step S3, the mass concentration of the fine-crystal carnallite mother liquor is 50-70 wt%.

4. The production method according to claim 1 or 2, characterized by, In the preparation process of the artificial F halogen, the water is added in an amount of 10-15 wt% of the raw material F halogen, and the F halogen salt pool magnesium chloride tailings are added in an amount of excess relative to the raw material F halogen.

5. The production method according to claim 1 or 2, characterized by, In the preparation process of the artificial E halogen, the solid-liquid ratio of the positive flotation tailings to the secondary halogen replacement completion solution is (10-12):1; and / or the solid-liquid ratio of the reverse flotation tailings to the secondary halogen replacement completion solution is (5-7):1; and / or the solid-liquid ratio of the sodium salt pool tailings to the secondary halogen replacement completion solution is (8-10):

1.

6. The production method according to claim 1 or 2, characterized by, In the preparation process of the circulating seed crystals, the volume ratio of the raw material F halogen to the primary halogen replacement completion solution is 1: (1-1.3).

7. The production method according to claim 1 or 2, characterized by, The recovery rate of the potassium chloride is greater than or equal to 75%.

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