Carnallite as well as preparation method and application thereof

Abstract

The invention discloses carnallite as well as a preparation method and application thereof, and relates to the technical field of salt lake development. In the carnallite preparation, sulfate type brine and high-calcium chloride type brine are subjected to primary brine blending, and first brine is prepared; the first brine accords with a Na < + >, K < + >, Mg < 2 + > / / Cl-H2O quaternary water salt system; the first brine and a magnesium supplementing agent are subjected to secondary brine mixing, and second brine is prepared; the second brine also conforms to a Na < + >, K < + > and Mg < 2 + > / / Cl-H2O quaternary water salt system phase diagram, and the system point is located at a position, close to a carnallite crystallization region, of a sodium chloride or potassium chloride crystallization region; two times of brine mixing are carried out in a salt pan, no equipment is adopted, the preparation process is easy and convenient to operate, stable in operation and low in cost, the yield of potassium chloride is increased, and the preparation method is suitable for areas where two kinds of brine coexist or technologies with similar raw material brine compositions.

Description

Technical Field

[0001] The invention relates to the technical field of salt lake development, and in particular to carnallite and a preparation method and application thereof. Background Art

[0002] At present, some areas have shallow brine and deep brine due to their special geographical environment. Shallow brine is rich in Na + Mg 2+ , Cl — 、SO4 2— , K + etc., which belongs to sulfate brine; while deep brine is rich in Na + Mg 2+ , Cl — , Ca 2+ , K + etc., wherein the calcium ion content reaches 0.44%, belonging to the high calcium chloride type. They exhibit different physical and chemical properties. When the existing salt field process is used to extract potassium chloride or concentrate lithium and boron, the entrainment loss is relatively serious due to the large number of intermediate products, resulting in a low yield, and the potassium extraction yield of the intermediate product is low, resulting in an increase in the cost of extracting potassium chloride. It is now urgent to seek a method for extracting potassium chloride, concentrating boron and lithium that is simple to operate, stable in operation, low in energy consumption, low in cost and efficient.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a carnallite and a preparation method and application thereof to solve the above technical problems.

[0005] The present invention is achieved in that:

[0006] In a first aspect, an embodiment of the present invention provides a method for preparing carnallite, the preparation method comprising:

[0007] The sulfate brine and the high calcium chloride brine are mixed once to obtain the first brine; the first brine meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system;

[0008] The first brine and the magnesium supplement are mixed twice to obtain a second brine; the second brine also meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system phase diagram, the system point is located in the sodium chloride or potassium chloride crystallization area close to the carnallite crystallization area;

[0009] The second brine is concentrated and crystallized to obtain carnallite.

[0010] In a second aspect, an embodiment of the present invention provides a carnallite prepared by the preparation method as described above.

[0011] In a third aspect, an embodiment of the present invention provides bischofite, which is prepared by the above-mentioned preparation method, and bischofite is precipitated when the potassium ion content in the brine for precipitating carnallite is ≤0.12% by mass.

[0012] The present invention has the following beneficial effects:

[0013] The carnallite and its preparation method and application provided by the embodiment of the present invention are as follows: sulfate brine and high-calcium chloride brine are mixed once to obtain a first brine; the first brine and a magnesium supplement are mixed twice to obtain a second brine; the two brine mixings are both carried out in the salt field without using any equipment, the preparation process is simple to operate, runs smoothly, has low cost, low energy consumption, and improves the yield of potassium chloride. At the same time, the preparation method is also suitable for areas where two brines coexist or processes with similar raw brine compositions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 Na at 25°C + , K + Mg 2+ / / Cl — -H2O quaternary system diagram;

[0016] Figure 2 Na at 25°C + , K + Mg 2+ / / Cl — - Trend diagram of evaporation, concentration and crystallization of H2O quaternary system;

[0017] Figure 3 The following is a flow chart of the specific preparation process of carnallite;

[0018] Figure 4 Schematic diagram of the evaporation and crystallization paths of Examples 1-4;

[0019] Figure 5The graph is a graph showing the change of pH and specific gravity of the second brine in the evaporation and crystallization process of Example 1-4;

[0020] Figure 6 This is a graph showing the variation of substance content in Example 1;

[0021] Figure 7 This is a graph showing the variation of substance content in Example 2;

[0022] Figure 8 This is a graph showing the variation of substance content in Example 3;

[0023] Fig. 9 This is a graph showing the variation of substance content in Example 4;

[0024] Fig.10 This is a graph showing the changes in the water evaporation rate, salt precipitation rate and brine formation rate during the evaporation and crystallization process of the second brine in Examples 1-4. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0026] The evaporation, crystallization, salt precipitation and enrichment of sulfate brine basically conform to the Na + , K + Mg 2+ / / Cl — 、SO4 2— -H2O quinary metastable phase diagram, during the evaporation process, it goes through seven stages in sequence: precipitation stage of sodium magnesium sulfate (Ast), co-saturation precipitation stage of sodium magnesium sulfate (Ast) and epsomite (Eps), precipitation stage of epsomite (Eps), co-saturation point of epsomite (Eps) and soft potassium magnesium sulfate (Pic), co-saturation precipitation stage of epsomite (Eps) and potassium chloride, co-saturation precipitation stage of epsomite (Eps) and carnallites (Car), co-saturation point of epsomite (Eps), carnallites (Car) and bischofite (Bis), etc. (winter is different from it), among which sodium chloride is saturated and precipitated throughout the process. During the whole evaporation process, lithium ions do not precipitate, but are enriched in brine, and are lost due to entrainment of mother liquor.

[0027] The indoor evaporation crystallization law of high calcium chloride brine is different from that of Na2O3 at 25℃ in the early stage of evaporation. + , K + Mg 2+ / / Cl — —H2O phase in quaternary water-salt system Figure 10The distribution of Ca in the solution is consistent with that in the later stage of evaporation. 2+ The evaporation and crystallization law of K + Mg 2+ , Ca 2+ / / Cl — —H2O quaternary water-salt system has a relatively good phase diagram, and its crystallization order is: sodium chloride, potassium chloride, carnallite (Car), calcium metaborate hexahydrate, boric acid, calcium chloride hexahydrate (Ant), bischofite (Bis), Li + Always in a state of enrichment.

[0028] In view of the different physical and chemical properties of sulfate brine and high calcium chloride brine, when using the existing salt pan process to extract potassium chloride or concentrate lithium and boron, the entrainment loss is serious due to the large number of intermediate products, resulting in a low yield, and the yield of potassium, boron and lithium extracted from the intermediate products is low, resulting in an increase in the cost of extracting potassium, boron and lithium. In order to solve this problem, the present invention is proposed in combination with the actual situation on site.

[0029] In a first aspect, an embodiment of the present invention provides a method for preparing carnallite, the preparation method comprising:

[0030] The sulfate brine and the high calcium chloride brine are mixed once to obtain the first brine; the first brine meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system;

[0031] The first brine and the magnesium supplement are mixed twice to obtain a second brine; the second brine also meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system phase diagram, the system point is located in the sodium chloride or potassium chloride crystallization area close to the carnallite crystallization area;

[0032] The second brine is concentrated and crystallized to obtain carnallite.

[0033] It should be noted that the specific position of the second brine after the secondary brine addition in the quaternary water-salt system phase diagram, whether it is in the sodium chloride crystallization area or the potassium chloride crystallization area, is related to the specific magnesium-potassium ratio. In the embodiment of the present invention, it can be reasonably adjusted according to the actual situation.

[0034] The primary brine addition process is to mix sulfate brine and high calcium chloride brine at room temperature. The calcium ions in the brine react with sulfate to form calcium sulfate precipitation, thereby removing most of the sulfate and calcium ions. The reaction equation is as follows:

[0035] SO4 2— +Ca 2+ =CaSO4↓

[0036] The main influencing factor in the formation of calcium sulfate is the solubility product constant of the solution. When IP (ion product) = Ksp, it indicates that the solution is in a saturated state. At this time, the precipitation and dissolution in the solution reach a dynamic equilibrium, with neither precipitation nor dissolution. When IP < Ksp, it indicates that the solution is unsaturated and no precipitation will occur in the solution. If a sparingly soluble electrolyte is added, it will continue to dissolve. When IP > Ksp, it indicates that the solution is supersaturated and precipitation will occur in the solution. Therefore, the molar ratio of sulfate ions and calcium ions is controlled during the first brine mixing process. According to the literature, when the solubility product (Ksp) of sulfate ions and calcium ions in the brine is greater than 1.377×10 -3 , precipitation begins.

[0037] During the first brine mixing process, most of the sulfate ions and calcium ions are removed while preparing the first brine, simplifying the brine composition. The first brine system obtained can be regarded as a quaternary water-salt system of Na + , K + , Mg 2+ / / Cl — —H2O.

[0038] In an alternative embodiment of the present invention, the sulfate-type brine and the high-calcium chloride-type brine are subjected to the first brine mixing in a mass ratio of (10 - 60):(40 - 90). It should be noted that the selection of this mass ratio range is mainly affected by the compositions of the sulfate-type brine and the high-calcium chloride-type brine. Since most of the sulfate ions and calcium ions in the brine are removed during the first brine mixing process, in other embodiments of the present invention, the two brines can also be subjected to the first brine mixing according to a molar ratio of sulfate ions and calcium ions in the brine of 1.

[0039] Specifically, the sulfate-type brine and the high-calcium chloride-type brine are subjected to the first brine mixing according to the mass ratio, introduced into the salt field, and fully mixed to obtain the first brine and a solid-phase mixture. Among them, the first brine conforms to the quaternary water-salt system of Na + , K + , Mg 2+ / / Cl — —H2O.

[0040] In an alternative embodiment of the present invention, the sulfate-type brine is selected from the brine at any stage during the sulfate evaporation process; further, the sulfate is selected from any one of magnesium sulfite and sodium sulfite.

[0041] It should be noted that the specific type of sulfate, magnesium sulfate or sodium sulfate, is directly related to the specific local climate, sampling time, etc. In an optional embodiment of the present invention, the specific type is reasonably adjusted according to the actual situation.

[0042] Furthermore, the sulfate is magnesium sulfate, and the brine of magnesium sulfate is selected from any one of magnesium sulfate-type raw brine, white sodium magnesium vanadium precipitation stage brine and chloranil salt precipitation stage brine.

[0043] It should be noted that the sulfate-type raw brine, the brine in the stage of sodium magnesium vanadium precipitation, and the brine in the stage of chlorpyrifos salt precipitation are all brines when the sulfate-type brine evaporates to different stages. The composition of the brine is greatly affected by the outside world. The composition of the sulfate-type brine used in the embodiment of the present invention is as follows:

[0044] Li in sulfate brine + The mass concentration is 22mg / L-110mg / L. According to the mass fraction, sulfate brine also contains: Na + : 2.0%-10.5%, K + :0.30%-2.1%,Mg 2+ : 1.3%-4.8%, SO4 2— :0.5%-8.8%,Cl — : 13.5%-14.5%, HCO3 — : 0%-0.05%, Ca 2+ :0%-0.25%, B2O3: 0%-0.1%.

[0045] Specifically, the components of sulfate-type raw halides include: Li + The mass concentration is 22.82 mg / L.

[0046] By mass fraction, Na + : 9.15%, K + :0.52%,Mg 2+ : 1.39%, SO4 2— :4.48%,Cl — : 13.88%, HCO3 — :0.04%,Ca 2+ :0.01%, B2O3: 0.05%.

[0047] The components of brine in the precipitation stage of sodium magnesium vanadium include: Li + The mass concentration of Na is 81.74 mg / L. + : 6.49%, K + : 1%,Mg 2+ : 2.98%, SO4 2—:8.72%,Cl — : 12.36%, Ca 2+ :0.01%, B2O3: 0.08%.

[0048] The components of brine in the salt precipitation stage include: Li + The mass concentration of Na is 100.1 mg / L. + : 2.17%, K + : 2.06%,Mg 2+ : 4.76%, SO4 2— :8.32%,Cl — :14.49%.

[0049] Li in high calcium chloride brine + The mass concentration is 150mg / L-160mg / L. According to the mass fraction, the high calcium chloride brine also contains: Na + : 10%-10.5%, K + :0.2%-0.35%,Mg 2+ :0.05%-0.1%,Ca 2+ :0.40%-0.50%,Cl — : 15.50%-16.00%, HCO3 — :0%-0.05%, B2O3: 0.1%-0.25%.

[0050] Specifically in the embodiment of the present invention, the components of the high calcium chloride brine used include: Li + The mass concentration of Na is 155.61 mg / L. + : 10.41%, K + :0.32%,Mg 2+ :0.09%,Ca 2+ :0.44%,Cl — : 15.95%, HCO3 — :0.04%, B2O3: 0.24%.

[0051] In an optional embodiment of the present invention, the first brine is selected from brine after a single brine addition or brine at any stage of the evaporation process after a single brine addition.

[0052] It should be noted that the main difference between the brine after one-time brine addition or the brine after one-time brine addition and evaporation is the different ion concentrations.

[0053] Specifically, the composition of the brine after the first brine addition varies according to the composition of the sulfate brine at different evaporation points. The composition of the brine after the first brine addition of sulfate brine and high calcium chloride brine includes: Li + The mass concentration of Na is 128.65 mg / L. + : 10.18%, K + :0.34%,Mg 2+ : 0.37%, SO4 2— :0.54%,Cl — :15.46%,Ca 2+ : 0.21%, B2O3: 0.2%.

[0054] In an optional embodiment of the present invention, the brine at any stage of the evaporation process after the first brine addition is selected as follows: brine evaporated to a point close to the saturation point of potassium chloride after the first brine addition, and the components of the brine include: Li + The mass concentration of Na is 926.23 mg / L. + : 3.21%, K + : 2.98%, Mg 2+ : 3.07%, SO4 2— :0.03%,Cl — :17.95%,Ca 2+ :0.37%, B2O3: 1.42%.

[0055] In an optional embodiment of the present invention, the first brine and the magnesium supplement are mixed for a second time at a mass ratio of (58-100):(10-45); further, the mass ratio of the first brine and the magnesium supplement is calculated according to the magnesium-potassium ratio at the saturation point of the three phases of NaCl, KCl and Car; further, the MgCl2 / KCl at the saturation point of the three phases is ≥300.

[0056] It should be noted that the composition of the first brine basically meets the Na + , K + Mg 2+ / / Cl — -H2O system, and then add a part of magnesium supplement to make the system point close to the three-phase saturation point of carnallite, potassium chloride and sodium chloride, such as Figure 1 As shown, the brine at point a and the magnesium supplement at point b are mixed to point c. After evaporation and concentration, the system reaches the three-phase saturation point at point d, and carnallite begins to precipitate.

[0057] In an optional embodiment of the present invention, the magnesium supplement is selected from the old brine after the second brine is concentrated to precipitate carnallite. In terms of mass fraction, the MgCl2 in the old brine is ≥ 34%.

[0058] It should be noted that in the present invention, the brine after the second brine is concentrated to precipitate carnallite can also be recorded as old brine. Specifically, due to the different substance concentrations of sulfate brine in the raw materials, the substance concentrations in the brine after the second brine is concentrated to precipitate carnallite will also be different.

[0059] In other embodiments of the present invention, the magnesium supplement can also be selected from Chaerhan old brine according to actual conditions; by mass fraction, Chaerhan old brine contains Mg 2+ :8.0%-9.5%.

[0060] The ingredients of the Chaerhan old brine used in the embodiment of the present invention include: Li + The mass concentration of Na is 76.89 mg / L. + : 0.056%, K + :0.02%,Mg 2+ : 8.23%, SO4 2— :0.05%,Cl — : 25.5%, Ca 2+ :0.58%,B2O3:0.08%. It should be noted that the composition of Chaerhan old brine is greatly affected by the external environment, and the specific content of the substances in its composition is reasonably adjusted according to the actual situation.

[0061] In an optional embodiment of the present invention, when the second brine is concentrated and crystallized, sodium salt ore is precipitated first, and then carnallite ore is precipitated; further, the concentrated crystallization includes evaporative crystallization; further, the sodium salt ore includes NaCl and CaSO4, and the yield of NaCl is ≥85%.

[0062] In an optional embodiment of the present invention, the carnallite ore includes carnallite, bischofite, sodium chloride and boric acid.

[0063] When the potassium ion content in the brine after the sodium salt ore is concentrated and precipitated is 1.40%-1.80% by mass fraction, carnallite is concentrated and precipitated; further, the yield of KCl in carnallite is ≥80%; preferably 80.5%-92%; further, part of the brine from the second brine concentrated to precipitate the carnallite ore is used as a magnesium supplement for secondary brine mixing with the first brine, and part of it is used for downstream ore dissolution or ore dissolution after lithium and boron extraction.

[0064] Specifically, the Na of the first brine and the brine after the second addition of magnesium supplement at 25℃ + , K + Mg 2+ / / Cl ——H2O is located in the sodium chloride region in the quaternary water-salt system phase diagram. As evaporation, concentration and crystallization proceed, sodium chloride is precipitated first, and the system point moves along the arrow direction to the saturation point of NaCl, KCl and carnallite, and carnallite begins to precipitate; continuing evaporation, concentration and crystallization, the system point continues along the NaCl and Car saturation line to the saturation point of NaCl, Car and Bis. Evaporation direction is shown in Figure 2 The theoretical order of salt precipitation is: sodium chloride, carnallite (Car), and bischofite (Bis).

[0065] It should be noted that during the evaporation, concentration and crystallization process, sodium chloride is precipitated throughout the process, and the yield is higher in the sodium salt ore precipitation stage; Li + Always in a state of enrichment.

[0066] In a second aspect, an embodiment of the present invention provides a carnallite prepared by the preparation method as described above.

[0067] In a third aspect, an embodiment of the present invention provides bischofite, which is prepared by the above-mentioned preparation method, and bischofite is precipitated when the potassium ion content in the brine for precipitating carnallite is ≤0.12% by mass.

[0068] In an optional embodiment of the present invention, the yield of bischofite is >7%; further, the yield of bischofite is 26%-45%.

[0069] It should be noted that the preparation method of carnallite provided by the present invention also includes the recovery of lithium and boron, wherein the recovery rate of lithium is ≥95%; and the yield of boron is ≥80%.

[0070] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0071] Example 1

[0072] This embodiment provides a method for preparing carnallite, which comprises the following steps:

[0073] S1. The brine from the small salt pan after the brine is added once is used as the first brine, and the first brine composition includes: Li + The mass concentration of Na is 128.65 mg / L. + : 10.18%, K + :0.34%,Mg 2+ : 0.37%, SO4 2— :0.54%,Cl — :15.46%,Ca 2+ : 0.21%, B2O3: 0.2%. The first brine meets the requirements of Na + , K + Mg2+ / / Cl — —H2O quaternary water-salt system;

[0074] It should be noted that the raw materials for the one-time brine conversion in small salt fields are sulfate-type raw brine and high-calcium chloride-type brine; the CaSO4 content obtained from the one-time brine conversion in small salt fields is 54.21%.

[0075] S2. According to the MgCl2 / KCl of 332.18, the first brine 49.90kg and Chaerhan old brine 5.60kg were weighed for secondary brine mixing, and then the brine was naturally evaporated; the second brine obtained by secondary brine mixing had a NaCl / KCl ratio of 332.18 at 25℃. + , K + Mg 2+ / / Cl — —H2O is located in the sodium chloride region in the quaternary water-salt system phase diagram. During the evaporation and crystallization process, sodium chloride, carnallite (Car) and bischofite (Bis) are crystallized successively. During the whole process, sodium chloride is precipitated continuously. + In the enriched state. The yield of NaCl is 84.10%; when K + When the content reaches 1.76%, carnallite precipitates, and the total yield of potassium chloride is 83.08%; the yield of bischofite is 26.55%, and the yield of lithium in the old brine is 90.74%.

[0076] It should be noted that the natural evaporation process after the secondary brine addition in this embodiment is carried out indoors. Figure 3 .

[0077] Example 2

[0078] This embodiment provides a method for preparing carnallite, which differs from Embodiment 1 in that:

[0079] S1. 44.23 kg of sodium magnesium vanadium precipitation stage brine and 5.77 kg of high calcium chloride brine were added into a container in proportion, mixed, stirred thoroughly, and separated after standing for 24 hours to obtain the first brine and CaSO4, with a yield of CaSO4 of 37.10%.

[0080] S2. According to the MgCl2 / KCl of the three-phase saturation point of NaCl, KCl and Car, 47.45kg of the first brine and 6.39kg of Chaerhan old brine were mixed with brine for the second time, and then naturally evaporated; the yield of NaCl was 85.08%; when K + When the content reaches 1.45%, halite is precipitated, and the total yield of potassium chloride is 81.65%; the yield of bischofite is 33.14%, and the yield of lithium in the old brine is 80.15%.

[0081] It should be noted that the natural evaporation process after the secondary brine addition in this embodiment is carried out outdoors.

[0082] Example 3

[0083] This embodiment provides a method for preparing carnallite, which differs from Embodiment 1 in that:

[0084] S1. 43.92 kg of brine from the salt precipitation stage of the salt extracting agent and 6.08 kg of high calcium chloride brine are added into a container in proportion, mixed, and stirred sufficiently. After standing for 24 hours, the mixture is separated to obtain the first brine and CaSO4. The yield of CaSO4 is 37.10%.

[0085] S2. According to the MgCl2 / KCl of the three-phase saturation point of NaCl, KCl and Car, 46.95kg of the first brine and 8.38kg of Chaerhan old brine were measured for secondary brine mixing, and then naturally evaporated after brine mixing; the yield of NaCl was 78.76%; when K + When the content reaches 1.8%, carnallite precipitates, and the total yield of potassium chloride is 80.53%; the yield of bischofite is 40.11%, and the yield of lithium in the old brine is 77.55%.

[0086] It should be noted that the natural evaporation process after the secondary brine addition in this embodiment is carried out outdoors.

[0087] Example 4

[0088] This embodiment provides a method for preparing carnallite, which differs from Embodiment 1 in that:

[0089] S1. The brine obtained by evaporating the small salt field to a point close to the saturation point of potassium chloride is used as the first brine. The first brine includes: Li + The mass concentration of Na is 926.23 mg / L. + : 3.21%, K + : 2.98%, Mg 2+ : 3.07%, SO4 2— :0.03%,Cl — :17.95%,Ca 2+ :00.37%, B2O3: 1.42%.

[0090] S2. According to the MgCl2 / KCl of the three-phase saturation point of NaCl, KCl and Car, 19.304kg of the first brine and 13.804kg of Chaerhan old brine were measured for secondary brine mixing, and then naturally evaporated after brine mixing; the yield of NaCl was 38.45%; when K +When the content reaches 1.8%, carnallite precipitates, and the total yield of potassium chloride is 91.17%; the yield of bischofite is 7.8%, and the yield of lithium in the old brine is 85.38%.

[0091] It should be noted that the natural evaporation process after the secondary brine addition in this embodiment is carried out outdoors.

[0092] Test Example 1

[0093] This test example studies the evaporation and crystallization path of the second brine in Example 1-4, and changes the evaporation and crystallization path to Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system phase diagram is marked; in order to reduce the loss, the sampling frequency is reduced in the early sodium chloride crystallization area, and the separation sampling frequency is accelerated near the three-phase saturation point. The loss is mainly caused by separation and sampling wall loss and weighing error.

[0094] See the schematic diagram of the evaporation crystallization path for Figure 4 ,from Figure 4 It can be seen that: Examples 1-3 are magnesium sulfate subtype brine and high calcium chloride type brine evaporated to different stages, and then old brine (i.e., Chaerhan old brine, which is a magnesium supplement) is added for secondary brine mixing and evaporation. Example 4 is magnesium sulfate subtype brine and high calcium chloride type brine. After the brine is mixed once, it is evaporated to a point close to the saturation point of potassium chloride and then old brine is added for secondary brine mixing. From the comparison of the evaporation phase diagrams of the four embodiments, although the starting points after brine mixing are different, they are all on the line connecting the three-phase saturation points of sodium chloride, potassium chloride, sodium chloride, and carnallite, and the evaporation paths are similar, all of which are the same as the NaCl saturation point at 25°C. + , K + Mg 2+ / / Cl — -H2O quaternary system phase diagram is relatively consistent. After the second brine addition, the system point is located in the sodium chloride crystallization area close to the carnallite crystallization area. Sodium chloride, potassium chloride, carnallite (Car), and bischofite (Bis) are crystallized and precipitated successively. Sodium chloride is precipitated throughout the process, and lithium is in an enriched state.

[0095] Test Example 2

[0096] This test example analyzes the change rules of pH and specific gravity of the second brine in the evaporation and crystallization process in Examples 1-4. The change rules are shown in Figure 5 Specifically, the pH is measured by a Leimagnetic pH meter, and the specific gravity is measured by a hydrometer. The determination of pH and specific gravity are both for guiding the actual production in the later stage.

[0097] from Figure 5It can be seen that during the evaporation process of the brine in Example 1, as the evaporation rate increases, the specific gravity gradually increases. When it reaches 1.22 g / cm 3 When the pH value is above 5g / cm, the rising rate is accelerated. As the evaporation rate increases, the pH value gradually decreases. 3 At around 5 pm, acidification and boron removal were carried out and the pH dropped sharply.

[0098] In the evaporation process of Example 2, as the water evaporation rate increases, the specific gravity of the brine gradually increases, and the increase rate gradually accelerates in the later stage of evaporation. The pH gradually decreases with the increase of the water evaporation rate. When it reaches about 5, the pH drops sharply due to acidification and boron removal. In the later stage, the pH value increases slightly with the precipitation of boric acid.

[0099] Example 3 During the evaporation process of brine, as the water evaporation rate increases, the specific gravity gradually increases, and the increase rate gradually accelerates in the later stage of evaporation. The pH gradually decreases with the increase of the water evaporation rate. When it reaches about 4.5, acidification and boron removal are carried out, and the pH drops sharply. In the later stage, the pH value fluctuates slightly with evaporation and precipitation of boric acid.

[0100] Example 4 During the evaporation process of brine, as the evaporation rate increases, the specific gravity gradually increases, and the increase rate gradually accelerates in the later stage of evaporation. The pH gradually decreases as the evaporation rate increases.

[0101] Test Example 3

[0102] This test example analyzes the change rule of the substance content in the liquid phase of the second brine in the evaporation and crystallization process in Examples 1-4 as the evaporation rate changes. The change of substance content can be determined by whether a solid phase is generated. Among them, lithium ions are determined by ion body inductively coupled emission spectrometer (ICP-OES); sodium ions are determined by subtraction method or ion body inductively coupled emission spectrometer (ICP-OES) as needed; potassium ions are analyzed by volumetric or gravimetric method according to the sample composition, and trace amounts are determined by ion body inductively coupled emission spectrometer (ICP-OES); magnesium ions are determined by EDTA volumetric method; B2O3 is determined by mannitol acid-base titration method; chloride ions are determined by AgNO3 volumetric method; calcium ions are determined by EDTA volumetric method.

[0103] In Examples 1-4, as the water evaporation rate increases during the evaporation crystallization process, the Li + , Cl — Mg 2+ Continuously enriched, Na + The content continued to decrease.

[0104] In addition, the variation of the substance content in Example 1 is shown in Figure 6 ,from Figure 6 It can be seen that with the increase of water evaporation rate, K+ The content first increases and then decreases. + The content reaches a maximum of about 1.5%, and then decreases rapidly with the precipitation of carnallite; the B2O3 content rises by about 0.8%, and acidification and boron removal reduce the boron to about 0.4%, and then increases slightly and then decreases, indicating that after acidification and boron removal, the boron in the liquid phase reaches equilibrium again, and with evaporation and concentration, boric acid precipitates again.

[0105] Example 2: Changes in the content of substances Figure 7 ,from Figure 7 It can be seen that with the increase of water evaporation rate, K + The content first increases and then decreases. + The content reaches a maximum of about 1.45%, and then decreases rapidly with the precipitation of carnallite; during the evaporation concentration process, as the evaporation rate increases, the B2O3 content in the liquid phase increases by about 0.8% (pH value 4.66), and acidification for boron removal reduces the pH value to 0.74, but the B2O3 content in the liquid phase only reduces to about 0.7%, indicating that the effect of acidification for boron removal is not obvious.

[0106] Example 3: Changes in the content of substances Figure 8 ,from Figure 8 It can be seen that with the increase of water evaporation rate, K + The content first increases and then decreases. + The content reached a maximum of about 1.8%, and then decreased rapidly with the precipitation of carnallite; the B2O3 content increased by about 0.7% (pH 4.56), and acidification and boron removal reduced the pH to 1.88, but the liquid phase B2O3 content did not decrease significantly, indicating that the effect of acidification and boron removal was not obvious.

[0107] Example 4: Changes in the content of substances Fig. 9 ,from Fig. 9 It can be seen that with the increase of water evaporation rate, K + The content first increases and then decreases. + The content reaches a maximum value of about 1.8%, and then decreases rapidly with the precipitation of carnallite; B2O3, Ca 2+ The content continues to increase.

[0108] Test Example 4

[0109] This test example analyzes the variation of the water evaporation rate, salt precipitation rate and brine formation rate of the second brine in the evaporation and crystallization process of Examples 1-4. Fig.10 .

[0110] from Fig.10 It can be seen that as the water evaporation rate increases, the salt precipitation rate increases and the halogen formation rate decreases. The salt precipitation rate and halogen formation rate curves in Examples 2-4 are basically linearly related.

[0111] In summary, the carnallites and the preparation method thereof provided by the present invention, which prepare the carnallites by primary brine addition, secondary brine addition and evaporation crystallization, have the following characteristics:

[0112] (1) The magnesium sulfate subtype brine and high calcium chloride type brine at different evaporation stages were subjected to a first brine addition and then a second brine addition and evaporation, and the evaporation and salt precipitation rules were similar.

[0113] (2) After the first brine addition, the second brine addition is carried out immediately, and after the first brine addition, the brine is evaporated to near the saturation point of potassium chloride and then the second brine addition is carried out. The only difference is the starting point of evaporation, but the evaporation path and salt precipitation law are similar.

[0114] (3) Evaporation and crystallization law of brine after secondary brine addition and Na + , K + Mg 2+ / / Cl — The quaternary system phase diagram of -H2O is relatively consistent. The system point is located in the sodium chloride or potassium chloride crystallization area close to the carnallite crystallization area. With the evaporation and crystallization process, sodium chloride, carnallite (Car), and bischofite (Bis) are crystallized and precipitated successively. During the whole process, sodium chloride is precipitated all the time. + It is in an enriched state; it can not only increase the yield of potassium, but also increase the yield of lithium and boron.

[0115] (4) After the second brine addition, the boron in the brine begins to precipitate in the carnallite area as the concentration increases and the pH value decreases. The acidification method is used to remove the boron, but the boron removal effect is not ideal due to the low boron content.

[0116] (5) This method is suitable for areas where two types of brine coexist (such as Dalangtan and Gasikule Lake) or processes with similar raw brine compositions; it is carried out in salt fields without using any equipment, and the preparation process is simple to operate, runs smoothly, and has low cost.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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 carnallite, characterized in that: The preparation method comprises: The sulfate brine and the high calcium chloride brine are mixed once to obtain the first brine; the first brine meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system; The first brine and the magnesium supplement are mixed twice to obtain a second brine; the second brine also meets the Na + , K + Mg 2+ / / Cl — —H2O quaternary water-salt system phase diagram, the system point is located in the sodium chloride or potassium chloride crystallization area close to the carnallite crystallization area; The second brine is concentrated and crystallized to obtain the carnallite.

2. The preparation method according to claim 1, characterized in that: The magnesium supplement is selected from the old brine after the second brine is concentrated to precipitate carnallite; Calculated by mass fraction, MgCl2 in the old brine is ≥ 34%.

3. The preparation method according to claim 1, characterized in that: The sulfate brine and the high calcium chloride brine are mixed once at a mass ratio of (10-60):(40-90).

4. The preparation method according to claim 3, characterized in that: The sulfate brine is selected from brine at any stage in the sulfate evaporation process; Preferably, the sulfate is selected from any one of magnesium sulfate and sodium sulfate; Preferably, the sulfate is magnesium sulfate, and the brine of magnesium sulfate is selected from any one of magnesium sulfate-type raw brine, white sodium magnesium vanadium precipitation stage brine and epsom salt precipitation stage brine.

5. The preparation method according to claim 1, characterized in that: The first brine is selected from brine after a brine addition or brine at any stage of evaporation after a brine addition; Preferably, CaSO4 is produced at the same time as the first brine is produced by the first brine addition.

6. The preparation method according to claim 1, characterized in that: The first brine and the magnesium supplement are mixed twice in a mass ratio of (58-100): (10-45); Preferably, the mass ratio of the first brine and the magnesium supplement is calculated according to the magnesium-potassium ratio of NaCl, KCl and Car at the saturation point of the three phases; Preferably, the magnesium-potassium ratio of the three-phase saturation point is MgCl2 / KCl ≥ 300.

7. The preparation method according to claim 1, characterized in that: When the second brine is concentrated and crystallized, sodium salt ore is precipitated first, and then carnallite ore is precipitated; Preferably, the concentrated crystallization comprises evaporative crystallization; Preferably, the sodium salt ore comprises NaCl and CaSO4, and the yield of NaCl is ≥85%.

8. The preparation method according to claim 7, characterized in that: The carnallite ore comprises carnallite, bischofite, sodium chloride and boric acid; When the potassium ion content in the brine after the sodium salt ore is concentrated and precipitated is 1.40%-1.80% by mass fraction, the carnallite is concentrated and precipitated; Preferably, the yield of KCl in the carnallite is ≥80%; preferably 80.5%-92%; Preferably, part of the brine from the second brine concentrated to precipitate the carnallite ore is used as a magnesium supplement for secondary brine mixing with the first brine, and part is used for downstream ore dissolution or ore dissolution after lithium or boron extraction.

9. A carnallite, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. A bischofite, characterized in that: The bischofite is prepared by the preparation method according to any one of claims 1 to 8, wherein the bischofite is precipitated when the potassium ion content in the brine after the carnallite is precipitated is ≤0.12% by mass fraction.

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