Method for preparing low-sodium carnallite and potassium chloride from calcium chloride type brine

Abstract

The invention discloses a method for preparing low-sodium carnallite and potassium chloride from calcium chloride type brine. The method comprises the following steps: naturally evaporating calcium chloride type brine to obtain sodium salt and potassium saturated brine; mixing a marinating agent with the potassium saturated brine for marinating to obtain marinated mixed brine; naturally evaporating the mixed brine to obtain sodium salt and carnallite saturated brine; naturally evaporating the carnallite saturated brine to obtain low-sodium carnallite ore and old brine; and the low-sodium carnallite ore is subjected to cold decomposition, flotation, washing and drying, and a high-grade potassium chloride product is obtained. According to the invention, calcium chloride type brine with equivalent calcium and magnesium contents is used as a raw material, a brine mixing process technology is introduced, and only low-sodium carnallite ore is separated out through regulation, control and evaporation and is used for preparing high-grade potassium chloride.

Description

Technical Field

[0001] This invention belongs to the field of salt lake brine utilization technology, and relates to a method for preparing low-sodium carnallite and potassium chloride from calcium chloride brine, and more particularly to a method for preparing low-sodium carnallite and potassium chloride from calcium chloride brine with equivalent calcium and magnesium content. Background Technology

[0002] Potash fertilizer is an essential element for ensuring increased crop yields. my country faces a large-scale potassium deficiency in its arable land, relying heavily on imports for potash fertilizer. Potash has long been listed as a critically scarce mineral resource in China. Over 98% of my country's potash resources are brine deposits, primarily magnesium chloride and sulfate types, and large-scale mining has already been achieved. In addition, the development and utilization of potassium resources in calcium chloride-type deep brines (including water from oil and gas fields) is also an important measure to ensure my country's long-term potash fertilizer supply.

[0003] Conventional development technology for potassium resources in calcium chloride-type brine still involves natural evaporation to first precipitate sodium salts, yielding potassium-saturated brine. Further evaporation of the potassium-saturated brine then precipitates halite and carnallite. Due to the influence of mineral properties, the production processes for potassium chloride fertilizer from halite and carnallite differ. Halite is produced using flotation or hot-melt crystallization, while carnallite is produced using cold decomposition-flotation or reverse flotation-cold crystallization. This technology diverts potassium resources from calcium chloride-type brine, and the differences in processing technology and equipment further increase production costs. Patents CN202210187766.X and CN202410067962.2 disclose technologies with high sodium content. The patent CN202210187766.X describes a potassium extraction process using calcium chloride-type potassium-containing brine characterized by high calcium and low magnesium. This involves natural evaporation to obtain a potassium mixed salt ore primarily composed of potassium halite and calcium-saturated brine. The calcium-saturated brine is then mixed with a magnesium chloride-saturated solution for further evaporation to precipitate carnallite. The patent CN202410067962.2 describes a process where the calcium-saturated brine after potassium halite precipitation is mixed with a magnesium chloride-saturated solution or cold decomposition mother liquor at high temperature before evaporation to obtain carnallite. While both technologies avoid the co-precipitation of calcium chloride during carnallite precipitation, they do not eliminate the drawback of potassium salt evaporation separating potassium halite and carnallite. Furthermore, the introduction of the brine mixing process only alters the brine evaporation trajectory without fundamentally affecting the sodium-potassium mass ratio in the precipitated carnallite. In reality, the sodium-potassium mass ratio in the solid phase remains high after cold decomposition of the carnallite, impacting the product grade and process yield of potassium chloride. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing low-sodium carnallite and potassium chloride from calcium chloride brine, so as to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a method for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine, comprising:

[0007] The calcium chloride brine is naturally evaporated to obtain sodium salt and potassium saturated brine; wherein the calcium-magnesium mass ratio (Ca / Mg, calculated as the mass ratio of Ca to Mg elements) in the calcium chloride brine is 0.5:1-1.5:1, and the potassium-magnesium mass ratio (K / Mg, calculated as the mass ratio of K to Mg elements) is 0.2:1-1:1; the sodium-potassium mass ratio (NaCl / KCl, calculated as the mass ratio of NaCl to KCl) in the potassium saturated brine is 0.5:1-1.5:1.

[0008] The brine diluent is mixed with the potassium-saturated brine to obtain a mixed brine. The brine diluent is a mixture of old brine after natural evaporation and precipitation of carnallite ore and a magnesium chloride solution with a concentration of 390-470 g / L. The brine diluent contains sodium ions at a concentration of 1-5 g / L, potassium ions at a concentration of 0.5-2 g / L, magnesium ions at a concentration of 90-95 g / L, and calcium ions at a concentration of 60-75 g / L. The sodium-potassium mass ratio in the mixed brine is 0.5:1-1.5: 1；

[0009] The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine; wherein the sodium-potassium mass ratio in the carnallite saturated brine is 0.5:1-0.55:1;

[0010] The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine; wherein the sodium-potassium mass ratio in the low-sodium carnallite ore is 0.2:1-0.5:1; the old brine is used to prepare a brine-mixing agent;

[0011] Furthermore, the low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] (1) This invention uses the phase diagram of the five-element water-salt system Na, K, Ca, Mg / Cl-H2O to perform theoretical calculations on brine evaporation, brine mixing, and cold decomposition, ensuring that each stage of the process is optimized and improving process efficiency.

[0014] (2) Due to the properties of calcium chloride, the brine additive of this invention is neither a separate evaporation of old brine nor a separate saturated magnesium chloride solution. Instead, it must be prepared by mixing old brine and magnesium chloride solution at the same time to ensure the stability and efficiency of the brine additive effect, while significantly reducing the amount of pure magnesium chloride input and reducing the impact on subsequent extraction processes of other resources.

[0015] (3) Unlike magnesium chloride brine, which directly supersaturates and precipitates low-sodium carnallite after being added to calcium chloride brine, the brine is not supersaturated after being added to calcium chloride brine. Continued evaporation will result in a secondary sodium precipitation stage, which further reduces the sodium-potassium mass ratio of the saturated brine for carnallite, so that the sodium-potassium mass ratio of carnallite ore is always kept at a low level, providing a raw material basis for the preparation of high-quality potassium chloride products.

[0016] (4) The method of the present invention can be widely used in the development and utilization of potassium resources in calcium chloride brine. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of a typical embodiment of the present invention for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine with equivalent calcium and magnesium content. Detailed Implementation

[0019] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have been able to propose the technical solution of this invention. This invention uses calcium chloride brine with equivalent calcium and magnesium content as raw material, introduces brine mixing technology, and through adjustment and control, evaporates only low-sodium carnallite ore for the preparation of high-grade potassium chloride.

[0020] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In this invention, the sodium-potassium mass ratio is calculated as the mass ratio of NaCl to KCl, the calcium-magnesium mass ratio is calculated as the mass ratio of Ca to Mg, and the potassium-magnesium mass ratio is calculated as the mass ratio of K to Mg.

[0022] Specifically, as one aspect of the technical solution of this invention, a method for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine includes:

[0023] The calcium chloride brine is naturally evaporated to obtain sodium salt and potassium saturated brine; wherein the calcium-magnesium mass ratio (Ca / Mg) in the calcium chloride brine is 0.5:1-1.5:1, and the potassium-magnesium mass ratio (K / Mg) is 0.2:1-1:1; the sodium-potassium mass ratio (NaCl / KCl) in the potassium saturated brine is 0.5:1-1.5:1.

[0024] The brine diluent is mixed with the potassium-saturated brine to obtain a mixed brine. The brine diluent is a mixture of old brine after natural evaporation and precipitation of carnallite ore and a magnesium chloride solution with a concentration of 390-470 g / L. The brine diluent contains sodium ions at a concentration of 1-5 g / L, potassium ions at a concentration of 0.5-2 g / L, magnesium ions at a concentration of 90-95 g / L, and calcium ions at a concentration of 60-75 g / L. The sodium-potassium mass ratio (NaCl / KCl) in the mixed brine is 0.5:1-1.5: 1；

[0025] The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine; wherein the sodium-potassium mass ratio (NaCl / KCl) in the carnallite saturated brine is 0.5:1-0.55:1;

[0026] The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine; wherein the sodium-potassium mass ratio (NaCl / KCl) in the low-sodium carnallite ore is 0.2:1-0.5:1; the old brine is used to prepare brine-mixing agents;

[0027] Furthermore, the low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product.

[0028] In some preferred embodiments, the composition point of the calcium chloride brine is located in the potassium chloride crystallization region of the Na, K, Ca, Mg / C1-H2O pentahydrate phase diagram.

[0029] In some preferred embodiments, the potassium ion concentration in the potassium-saturated brine is 15-40 g / L, the calcium-magnesium mass ratio (Ca / Mg) is 0.5:1-1.5:1, and the potassium-magnesium mass ratio (K / Mg) is 0.2:1-1:1.

[0030] In some preferred embodiments, the magnesium chloride solution includes any one or more combinations of carnallite cold decomposition mother liquor, magnesia hydrate, or other magnesium chloride saturated solutions prepared with magnesium chloride solid phase, and is not limited thereto.

[0031] In some preferred embodiments, the mass ratio of the potassium-saturated brine to the brine additive is 1:1 to 10:1.

[0032] In some preferred embodiments, the concentration of sodium ions in the brine mixture is 7-25 g / L, the concentration of potassium ions is 14-22 g / L, the concentration of magnesium ions is 50-78 g / L, the concentration of calcium ions is 35-70 g / L, the calcium-magnesium mass ratio (Ca / Mg) is 0.51:1-1.37:1, and the potassium-magnesium mass ratio (K / Mg) is 0.29:1-0.37:1.

[0033] In some preferred embodiments, the sodium ion concentration in the carnallite saturated brine is 7-9 g / L, the potassium ion concentration is 15-23 g / L, the magnesium ion concentration is 50-84 g / L, the calcium ion concentration is 35-70 g / L, the calcium-magnesium mass ratio (Ca / Mg) is 0.51:1-1.37:1, and the potassium-magnesium mass ratio (K / Mg) is 0.29:1-0.37:1.

[0034] In some preferred embodiments, the low-sodium carnallite contains 2-4 wt% sodium ions, 10-12 wt% potassium ions, 7-8 wt% magnesium ions, and 0.1-0.7 wt% calcium ions.

[0035] In some preferred embodiments, the concentration of sodium ions in the old brine is 2-6 g / L, the concentration of potassium ions is 0.7-1.5 g / L, the concentration of magnesium ions is 52-91 g / L, and the concentration of calcium ions is 60-155 g / L.

[0036] In some preferred embodiments, the decomposition mother liquor produced by the cold decomposition of the low-sodium carnallite ore is used to prepare the brine mixing agent.

[0037] In some more specific embodiments, the method for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine with equivalent calcium and magnesium content includes the following steps:

[0038] (1) Sodium salt and potassium saturated brine are precipitated by natural evaporation of calcium chloride brine. The calcium-magnesium mass ratio (Ca / Mg) of the calcium chloride brine is 0.5:1-1.5:1, and the potassium-magnesium mass ratio (K / Mg) is 0.2:1-1:1. The composition point of the calcium chloride brine is located in the potassium chloride crystallization region of the Na, K, Ca, Mg / Cl-H2O pentahydrate salt system phase diagram. The endpoint of the sodium salt segment can be calculated by the Na, K, Ca, Mg / Cl-H2O pentahydrate salt system phase diagram. The potassium ion concentration of the potassium saturated brine is 15-40 g / L, the calcium-magnesium mass ratio (Ca / Mg) is 0.5:1-1.5:1, the potassium-magnesium mass ratio (K / Mg) is 0.2:1-1:1, and the sodium-potassium mass ratio (NaCl / KCl) is 0.5:1-1.5:1.

[0039] (2) A brine diluent is added in a certain proportion and mixed with potassium-saturated brine to obtain a mixed brine. The brine diluent is a mixture of old brine after natural evaporation and precipitation of carnallite and a magnesium chloride solution with a concentration of 390-470 g / L. The magnesium chloride solution includes the mother liquor from the cold decomposition of carnallite, magnesium chloride solution prepared from other magnesium chloride-containing liquid solid phases, etc. The concentration of sodium ions in the brine diluent is 1-5 g / L, the concentration of potassium ions is 0.5-2 g / L, the concentration of magnesium ions is 90-95 g / L, and the concentration of calcium ions is 60-75 g / L. The brine diluent ratio can be calculated using the Na, K, Ca, Mg / Cl-H2O pentaceous water-salt system phase diagram to ensure that the mixed brine enters the carnallite phase region and maximizes the carnallite precipitation rate; the mass ratio of potassium-saturated brine to brine diluent is controlled within the range of 1:1-10:1. The concentration of sodium ions in the mixed brine is 7-25 g / L, potassium ions are 14-22 g / L, magnesium ions are 50-78 g / L, calcium ions are 35-70 g / L, the calcium-magnesium mass ratio (Ca / Mg) is 0.51:1-1.37:1, the potassium-magnesium mass ratio (K / Mg) is 0.29:1-0.37:1, and the sodium-potassium mass ratio (NaCl / KCl) is 0.5:1-1.5:1.

[0040] (3) The mixed brine is allowed to evaporate naturally, and pure sodium salt continues to precipitate, resulting in carnallite saturated brine. Calculations using the water-salt system phase diagram show that the natural evaporation of the mixed brine still results in a separate pure sodium salt precipitation stage, which can further reduce the sodium-potassium mass ratio of the brine. The resulting carnallite saturated brine has a sodium ion concentration of 7-9 g / L, a potassium ion concentration of 15-23 g / L, a magnesium ion concentration of 50-84 g / L, a calcium ion concentration of 35-70 g / L, a calcium-magnesium mass ratio (Ca / Mg) of 0.51:1-1.37:1, a potassium-magnesium mass ratio (K / Mg) of 0.29:1-0.37:1, and a sodium-potassium mass ratio (NaCl / KCl) of 0.5:1-0.55:1.

[0041] (4) The saturated carnallite brine is further evaporated naturally to obtain carnallite ore and old brine. The carnallite ore has a sodium ion content of 2%-4%, a potassium ion content of 10%-12%, a magnesium ion content of 7%-8%, and a calcium ion content of 0.1%-0.7%. The sodium-potassium mass ratio (NaCl / KCl) is 0.2:1-0.5:1, making it a low-sodium carnallite ore. The old brine has a sodium ion concentration of 2-6 g / L, a potassium ion concentration of 0.7-1.5 g / L, a magnesium ion concentration of 52-91 g / L, and a calcium ion concentration of 60-155 g / L.

[0042] (5) Low-sodium carnallite ore undergoes cold decomposition-flotation, washing, and drying processes to obtain high-grade potassium chloride products. The mother liquor produced in the cold decomposition process is used to prepare brine additives, thereby improving utilization.

[0043] The process flow diagram of the method for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine with equivalent calcium and magnesium content in this invention is as follows: Figure 1 As shown.

[0044] Based on the patented technology of this invention, potassium resources from calcium chloride brine with equivalent calcium and magnesium content are extracted only in the form of carnallite, and the processing procedures are standardized. At the same time, through the secondary sodium precipitation stage after brine mixing, the sodium-potassium mass ratio of the saturated brine for carnallite is further reduced, thereby obtaining high-grade, low-sodium carnallite ore, improving the cold decomposition efficiency of carnallite and product quality, with obvious technological and economic advantages.

[0045] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0046] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0047] Example 1

[0048] Raw brine composition: Na ion concentration 89.70 g / L, K ion concentration 3.08 g / L, Ca ion concentration 5.07 g / L, Mg ion concentration 7.92 g / L. Calcium-magnesium mass ratio (Ca / Mg) is 0.64:1, and potassium-magnesium mass ratio (K / Mg) is 0.39:1.

[0049] Sodium salt stage: The raw brine is naturally evaporated to obtain sodium and potassium saturated brine;

[0050] The potassium-saturated brine composition was as follows: Na ion concentration 15.00 g / L, K ion concentration 24.20 g / L, Ca ion concentration 32.24 g / L, and Mg ion concentration 60.64 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.53:1, the potassium-magnesium mass ratio (K / Mg) was 0.40:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.83:1.

[0051] Brine mixing section: The brine mixing agent is mixed with potassium-saturated brine to obtain mixed brine;

[0052] The halogenating agent has the following composition and content: Na ion concentration 1.72 g / L, K ion concentration 0.80 g / L, Ca ion concentration 69.12 g / L, and Mg ion concentration 91.12 g / L.

[0053] The mass ratio of potassium-saturated brine to brine additive is 5:1.

[0054] The mixed brine composition was as follows: Na ion concentration 13.32 g / L, K ion concentration 21.20 g / L, Ca ion concentration 37.00 g / L, and Mg ion concentration 60.16 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.62:1, the potassium-magnesium mass ratio (K / Mg) was 0.35:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.84:1.

[0055] Secondary sodium salt stage: The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine;

[0056] The saturated brine from carnallite contained the following ion concentrations: Na ion concentration 8.24 g / L, K ion concentration 21.96 g / L, Ca ion concentration 37.52 g / L, and Mg ion concentration 61.24 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.61:1, the potassium-magnesium mass ratio (K / Mg) was 0.36:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.50:1.

[0057] Carnallite section: The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine;

[0058] The carnallite mineral composition is as follows: Na ion content 3.73%, K ion content 10.06%, Ca ion content 0.45%, and Mg ion content 7.50%. The sodium-potassium mass ratio (NaCl / KCl) is 0.49:1.

[0059] The composition of the old brine is as follows: Na ion concentration 2.72 g / L, K ion concentration 1.24 g / L, Ca ion concentration 69.36 g / L, and Mg ion concentration 87.76 g / L.

[0060] Carnallite processing section: The low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product; the potassium chloride product has a KCl content of 95.34%.

[0061] Comparative Example 1

[0062] The potassium-saturated brine after the sodium salt stage of the raw brine in Example 1 was subjected to natural evaporation without dilution, successively passing through the potassium halite stage and the carnallite stage, to obtain potassium halite ore and carnallite ore respectively. Potassium was diverted during the evaporation process.

[0063] The potash ore composition consisted of 24.26% Na ions, 14.15% K ions, 0.25% Ca ions, and 0.45% Mg ions. The potassium precipitation rate in this stage was 19.82%.

[0064] The carnallite ore composition is as follows: Na ion content 3.89%, K ion content 11.87%, Ca ion content 0.42%, and Mg ion content 8.27%. The potassium precipitation rate in this stage is 78.23%.

[0065] Comparative Example 2

[0066] The mixed brine from Example 1 was subjected to natural evaporation without a secondary sodium salt stage, directly yielding carnallite. The carnallite composition was 6.13% Na ions, 10.39% K ions, 0.40% Ca ions, and 7.41% Mg ions. The sodium-potassium mass ratio (NaCl / KCl) of the carnallite was 0.79:1, significantly higher than that of the carnallite in Example 1.

[0067] Example 2

[0068] Raw brine composition: Na ion concentration 78.67 g / L, K ion concentration 8.24 g / L, Ca ion concentration 11.95 g / L, Mg ion concentration 7.96 g / L. Calcium-magnesium mass ratio (Ca / Mg) is 1.50:1, and potassium-magnesium mass ratio (K / Mg) is 1.00:1.

[0069] Sodium salt stage: The raw brine is naturally evaporated to obtain sodium and potassium saturated brine;

[0070] The potassium-saturated brine composition was as follows: Na ion concentration 32.89 g / L, K ion concentration 35.34 g / L, Ca ion concentration 51.23 g / L, and Mg ion concentration 34.15 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 1.50:1, the potassium-magnesium mass ratio (K / Mg) was 1.00:1, and the sodium-potassium mass ratio (NaCl / KCl) was 1.24:1.

[0071] Brine mixing section: The brine mixing agent is mixed with potassium-saturated brine to obtain mixed brine;

[0072] The halogenating agent has the following composition and content: Na ion concentration 1.00 g / L, K ion concentration 0.50 g / L, Ca ion concentration 60.00 g / L, and Mg ion concentration 95.00 g / L.

[0073] The mass ratio of potassium-saturated brine to brine additive is 1.37:1.

[0074] The mixed brine composition was as follows: Na ion concentration 19.88 g / L, K ion concentration 21.14 g / L, Ca ion concentration 54.15 g / L, and Mg ion concentration 57.92 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.93:1, the potassium-magnesium mass ratio (K / Mg) was 0.36:1, and the sodium-potassium mass ratio (NaCl / KCl) was 1.25:1.

[0075] Secondary sodium salt stage: The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine;

[0076] The saturated brine from carnallite contained the following ion concentrations: Na ion concentration 8.50 g / L, K ion concentration 21.23 g / L, Ca ion concentration 54.40 g / L, and Mg ion concentration 58.19 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.93:1, the potassium-magnesium mass ratio (K / Mg) was 0.36:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.53:1.

[0077] Carnallite section: The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine;

[0078] The carnallite mineral composition is as follows: Na ion content 3.28%, K ion content 12.00%, Ca ion content 0.40%, and Mg ion content 8.00%. The sodium-potassium mass ratio (NaCl / KCl) is 0.36:1.

[0079] The composition of the old brine is as follows: Na ion concentration 5.40 g / L, K ion concentration 0.99 g / L, Ca ion concentration 90.53 g / L, and Mg ion concentration 75.48 g / L.

[0080] Carnallite processing section: The low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product; the potassium chloride product has a KCl content of 98.15%.

[0081] Comparative Example 3

[0082] In Example 2, the potassium-saturated brine after the sodium salt stage of the raw brine was first diluted with brine using the diluent, which was the old brine (C0) obtained by natural evaporation of the raw brine. The diluted brine was then naturally evaporated, undergoing two sodium salt stages and a carnallite stage, yielding sodium salt, carnallite ore, and old brine (C1). The diluent for the second dilution was C1. After natural evaporation, the diluted brine yielded old brine (C2), which was used for the next dilution. This cycle was repeated. As the number of cycles increased, the concentrations of K and Ca ions in the old brine gradually increased, while the concentration of Mg ions gradually decreased. To achieve the optimal dilution effect, the mass ratio of potassium-saturated brine to old brine gradually decreased. Simultaneously, when the composition of the old brine crossed the cosaturation point of carnallite, chalcanthite, and calcium chloride hexahydrate, the concentration of K ions in the old brine rapidly increased, significantly reducing the K precipitation rate of the carnallite ore. When the composition of the old brine is Na ion concentration of 4.01 g / L, K ion concentration of 5.89 g / L, Ca ion concentration of 215.52 g / L, and Mg ion concentration of 18.45 g / L, and it is mixed with the potassium-saturated brine of Example 2, the mass ratio of the mixed brine decreases to 0.92:1, which increases the demand for old brine and the difficulty of supplying it. At the same time, the K ion concentration of the old brine obtained by natural evaporation increases to 4.70 g / L, and the K precipitation rate of carnallite decreases. The actual technical effect is inferior to that of Example 2.

[0083] Example 3

[0084] Raw brine composition: Na ion concentration 78.67 g / L, K ion concentration 2.82 g / L, Ca ion concentration 7.04 g / L, Mg ion concentration 14.08 g / L. Calcium-magnesium mass ratio (Ca / Mg) is 0.50:1, and potassium-magnesium mass ratio (K / Mg) is 0.20:1.

[0085] Sodium salt stage: The raw brine is naturally evaporated to obtain sodium and potassium saturated brine;

[0086] The potassium-saturated brine composition was as follows: Na ion concentration 8.20 g / L, K ion concentration 15.15 g / L, Ca ion concentration 37.85 g / L, and Mg ion concentration 75.72 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.50:1, the potassium-magnesium mass ratio (K / Mg) was 0.20:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.72:1.

[0087] Brine mixing section: The brine mixing agent is mixed with potassium-saturated brine to obtain mixed brine;

[0088] The halogenating agent has the following composition and content: Na ion concentration 5.00 g / L, K ion concentration 2.00 g / L, Ca ion concentration 75.00 g / L, and Mg ion concentration 90.00 g / L.

[0089] The mass ratio of potassium-saturated brine to brine additive is 9.92:1.

[0090] The mixed brine composition was as follows: Na ion concentration 7.94 g / L, K ion concentration 14.04 g / L, Ca ion concentration 41.22 g / L, and Mg ion concentration 77.20 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.53:1, the potassium-magnesium mass ratio (K / Mg) was 0.18:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.75:1.

[0091] Secondary sodium salt stage: The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine;

[0092] The saturated brine from carnallite contained the following ion concentrations: Na ion concentration 7.04 g / L, K ion concentration 15.14 g / L, Ca ion concentration 44.45 g / L, and Mg ion concentration 83.25 g / L. The calcium-magnesium mass ratio (Ca / Mg) was 0.53:1, the potassium-magnesium mass ratio (K / Mg) was 0.18:1, and the sodium-potassium mass ratio (NaCl / KCl) was 0.62:1.

[0093] Carnallite section: The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine;

[0094] The carnallite mineral composition is as follows: Na ion content 3.78%, K ion content 12.72%, Ca ion content 0.35%, and Mg ion content 7.90%. The sodium-potassium mass ratio (NaCl / KCl) is 0.40:1.

[0095] The composition of the old brine is as follows: Na ion concentration 5.40 g / L, K ion concentration 0.72 g / L, Ca ion concentration 60.00 g / L, and Mg ion concentration 91.00 g / L.

[0096] Carnallite processing section: The low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product; the potassium chloride product has a KCl content of 97.25%.

[0097] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0098] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing low-sodium carnallite and potassium chloride from calcium chloride-type brine, characterized in that, include: The calcium chloride brine is naturally evaporated to obtain sodium salt and potassium saturated brine; wherein the calcium-magnesium mass ratio in the calcium chloride brine is 0.5:1-1.5:1, and the potassium-magnesium mass ratio is 0.2:1-1:1; the sodium-potassium mass ratio in the potassium saturated brine is 0.5:1-1.5:

1. The brine diluent is mixed with the potassium-saturated brine to obtain a mixed brine. The brine diluent is a mixture of old brine after natural evaporation and precipitation of carnallite ore and a magnesium chloride solution with a concentration of 390-470 g / L. The brine diluent contains sodium ions at a concentration of 1-5 g / L, potassium ions at a concentration of 0.5-2 g / L, magnesium ions at a concentration of 90-95 g / L, and calcium ions at a concentration of 60-75 g / L. The sodium-potassium mass ratio in the mixed brine is 0.5:1-1.5: 1； The mixed brine is naturally evaporated to obtain sodium salt and carnallite saturated brine; wherein the sodium-potassium mass ratio in the carnallite saturated brine is 0.5:1-0.55:1; The saturated carnallite brine is naturally evaporated to obtain low-sodium carnallite ore and old brine; wherein the sodium-potassium mass ratio in the low-sodium carnallite ore is 0.2:1-0.5:1; the old brine is used to prepare a brine-mixing agent; Furthermore, the low-sodium carnallite ore is subjected to cold decomposition, flotation, washing, and drying to obtain a high-grade potassium chloride product.

2. The method according to claim 1, characterized in that: The composition of the calcium chloride brine is located in the potassium chloride crystallization region of the Na, K, Ca, Mg / Cl-H2O pentahydrate phase diagram.

3. The method according to claim 1, characterized in that: The potassium ion concentration in the potassium-saturated brine is 15-40 g / L, the calcium-magnesium mass ratio is 0.5:1-1.5:1, and the potassium-magnesium mass ratio is 0.2:1-1:

1.

4. The method according to claim 1, characterized in that: The magnesium chloride solution includes any one or more combinations of mother liquor from the cold decomposition of carnallite, magnesium chloride water, or other magnesium chloride saturated solutions prepared with magnesium chloride solid phase.

5. The method according to claim 1, characterized in that: The mass ratio of potassium-saturated brine to brine additive is 1:1 to 10:

1.

6. The method according to claim 1, characterized in that: The concentration of sodium ions in the mixed brine is 7-25 g / L, the concentration of potassium ions is 14-22 g / L, the concentration of magnesium ions is 50-78 g / L, the concentration of calcium ions is 35-70 g / L, the mass ratio of calcium to magnesium is 0.51:1-1.37:1, and the mass ratio of potassium to magnesium is 0.29:1-0.37:

1.

7. The method according to claim 1, characterized in that: The sodium ion concentration in the saturated carnallite brine is 7-9 g / L, the potassium ion concentration is 15-23 g / L, the magnesium ion concentration is 50-84 g / L, the calcium ion concentration is 35-70 g / L, the calcium-magnesium mass ratio is 0.51:1-1.37:1, and the potassium-magnesium mass ratio is 0.29:1-0.37:

1.

8. The method according to claim 1, characterized in that: The low-sodium carnallite ore contains 2-4 wt% sodium ions, 10-12 wt% potassium ions, 7-8 wt% magnesium ions, and 0.1-0.7 wt% calcium ions.

9. The method according to claim 1, characterized in that: The concentration of sodium ions in the old brine is 2-6 g / L, the concentration of potassium ions is 0.7-1.5 g / L, the concentration of magnesium ions is 52-91 g / L, and the concentration of calcium ions is 60-155 g / L.

10. The method according to claim 1, characterized in that: The decomposition mother liquor produced by the cold decomposition of the low-sodium carnallite ore is used to prepare the brine mixing agent.

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