CN111362730A - Method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite - Google Patents
Method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite Download PDFInfo
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Abstract
The invention discloses a method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite. The method comprises the following steps: first enriched in MgCl2Mixing the substances with fresh water and carrying out preheating treatment to obtain a hot solvent; then carrying out selective hot-melting treatment on the high-sodium carnallite by using the hot solvent to obtain high-temperature potassium-rich saturated solution; then carrying out stepped closed cooling crystallization on the high-temperature potassium-rich saturated liquid to prepare crude potassium chloride and low-temperature potassium saturated liquid; and finally, evaporating the low-temperature potassium saturated solution to obtain low-sodium carnallite, and then decomposing and selectively dissolving the obtained low-sodium carnallite to obtain crude potassium chloride. The invention ensures the high-efficiency and high-quality precipitation of the potassium chloride by selective hot melting and stepped closed cooling crystallization; meanwhile, the artificial sylvite is selected at low temperature onceThe potassium chloride can be prepared by selective dissolution, thus avoiding repeated circulating hot-melt crystallization treatment; the method has mild conditions and simple method, and is convenient for popularization and implementation.
Description
Technical Field
The invention belongs to the technical field of inorganic salt industry, and particularly relates to a method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite.
Background
The potash fertilizer is a basic material for the stable growth of grain production, can effectively improve the quality of agricultural products and the stress resistance of crops, and is one of the nutrients necessary for the growth of the crops. With the reduction of the cultivated land area and the continuous increase of population, the potassium resource is developed on a large scale, the yield of the potassium fertilizer is improved, and the method has important food safety significance.
The potassium fertilizer product type is mainly potassium chloride fertilizer and accounts for more than 90 percent of the total amount of the potassium fertilizer. The raw materials for preparing the potassium chloride fertilizer mainly comprise sylvite and carnallite, and along with long-time scale development, the carnallite at the present stage is mainly high-sodium carnallite which comprises 30-60 percent of NaCl, 10-20 percent of KCl and MgCl215％～30％，H215 to 30 percent of O, and the mass ratio of the sodium chloride to the potassium chloride is as high as 1.5:1 to 6.0:1, thereby providing difficulty for preparing the potassium chloride fertilizer from the carnallite.
At present, the method for preparing potassium chloride by using carnallite mainly comprises the following steps:
(1) cold decomposition-washing method: the technological process includes decomposing carnallite completely to obtain artificial sylvine, washing with water and drying to obtain potassium chloride product, and the technological process is only suitable for carnallite ore with very low NaCl content, and has water amount increased with NaCl content and KCl yield decreased gradually;
(2) cold decomposition-flotation: the technical process comprises the steps of completely decomposing carnallite in fresh water or refined potassium mother liquor to obtain artificial sylvite, then carrying out flotation by adopting a positive flotation collector (mainly an amine collector), washing a solid phase after flotation by adding water, and drying to obtain a finished product of potassium chloride, wherein the technical process can be seen in figure 1. The technique is also applicable to carnallite mixed with sylvite (patent CN 1094466C). Further, patent CN102442687B adopts a rotary decomposer to perform cold decomposition, selectively fractionally separate coarse particle NaCl, and perform flotation on the remaining pulp to obtain qualified KCl concentrate; patent CN107188200B adopts a multi-stage screening system to separate cold decomposed slurry to sequentially obtain coarse grain NaCl, coarse grain KCl and fine grain KCl slurry, and the fine grain KCl slurry is subjected to flotation separation to obtain KCl concentrate; the two technologies greatly improve the product quality of potassium chloride, although the technology saves energy sources when producing potassium chloride, the factory building investment is less, the technology is simple and easy to master, but the obtained product has fine granularity, poor physical properties and low potassium yield which is generally 50-60 percent, the physical properties of the product are poor, the granularity of more than 100 meshes in the product only accounts for 10-20 percent and is gradually difficult to adapt to the requirements of the international market, the technology has great influence on the type of carnallite, and when the content of NaCl in the carnallite is high, the grade and yield of KCl are greatly reduced;
(3) reverse flotation-cold crystallization: on the basis of the original process, patents CN104058427A and CN107572552A introduce a screening system before reverse flotation, preferentially screen out large-particle NaCl, further reduce the NaCl content in the low-sodium carnallite and ensure the stable operation of cold crystallization, although the quality of the potassium chloride product produced by the technology is high and can reach about 95 percent, the product has coarse granularity and good appearance effect, the process is complex, the operation is not easy (especially a crystallization system), the requirement on raw ores is high, and the dependence is strong;
(4) brine adding-speed controlling crystallization method: the technology mixes the mother liquor (carnallite saturation point) which is co-saturated by potassium chloride, sodium chloride and carnallite with the mother liquor (bischofite saturation point) which is co-saturated by magnesium chloride, sodium chloride and carnallite, low-sodium carnallite is separated out due to the supersaturation of potassium and magnesium, the mixture enters a crystallizer after concentration and liquid removal, and high-grade potassium chloride is obtained after adding fresh water for decomposition and crystallization, the technological process of adding the carnallite is shown in figure 3, although the technology has the obvious advantages of simple technological process, excellent product quality, less investment in basic construction, low production cost, high operation recovery rate, high resource utilization rate, no environmental pollution and the like, the technology takes decomposed mother liquor as raw material, the production scale can not be randomly expanded, only depends on large-scale flotation plants, and the yield is lower;
(5) sun-drying method: the technical process comprises the steps of dissolving carnallite ores obtained by solarizing intercrystalline brine again with fresh water, discharging the carnallite ores into a potassium salt pool, independently separating out potassium chloride in the potassium salt pool, concentrating the brine in the potassium salt pool until the sodium chloride is saturated, and carrying out solarization and cyclic utilization on the brine at the moment, wherein the brine is sylvite brine, and the technological process of the solarization method can be shown in a figure 4. Although the solarization method technology fully utilizes solar energy, no medicament is added, the product quality is good, the granularity of the precipitated potassium chloride is generally more than 0.2mm, the purity is high, the yield is low, and the influence of climate conditions is large;
(6) cold decomposition-hot melt crystallization method: according to the technical process, after carnallite is completely decomposed by fresh water to obtain artificial sylvite, according to the principle that the solubility of sodium chloride and potassium chloride is different along with the change trend of temperature, sodium chloride in the artificial sylvite is removed by hot dissolution of the fresh water, and potassium chloride is obtained by cooling and crystallizing mother liquor.
On the basis of the original process, the patent CN102583446B utilizes old brine to fully thermally dissolve low-sodium carnallite ore at high temperature to obtain a hot solution, the hot solution is cooled to separate out potassium chloride, but only aiming at the low-sodium carnallite, the solid-to-mass ratio of the hot solution is improved, all the low-sodium carnallite (including NaCl) enters a liquid phase, and therefore crude potassium obtained by cooling is still sylvite actually, and the process effect is poor. In patent CN103193252B, after carnallite is decomposed by high-temperature potassium-rich brine to obtain artificial sylvite salt, the artificial sylvite salt is treated by a hot-melt crystallization process to prepare potassium chloride, and the decomposition efficiency of carnallite is extremely low because the concentration of K ions in the hot-melt brine is very high; meanwhile, a large amount of decomposed solid phase is still in the form of fine-grain sylvine except a small amount of large-grain KCl, and the overall effect is poor.
Generally, the technical effect of preparing potassium chloride from carnallite ore at the present stage is closely related to the content of sodium chloride in the carnallite ore, the higher the content of sodium chloride is, the lower the yield and grade of potassium chloride are, and particularly for high-sodium carnallite ore, the actual effect is not ideal.
Disclosure of Invention
The invention mainly aims to provide a method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite, so as to overcome the defects of the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite, which comprises the following steps:
will be rich in MgCl2Mixing the substances with fresh water and carrying out preheating treatment to obtain a hot solvent;
carrying out selective hot-melting treatment on the high-sodium carnallite by using the hot solvent to obtain high-temperature potassium-rich saturated solution;
performing stepped closed cooling crystallization on the high-temperature potassium-rich saturated liquid to prepare crude potassium chloride and low-temperature potassium saturated liquid;
and evaporating the low-temperature potassium saturated solution to obtain low-sodium carnallite, and then decomposing and selectively dissolving the obtained low-sodium carnallite to obtain potassium chloride.
Further, the method further comprises: and washing, solid-liquid separation and drying the obtained crude potassium chloride to obtain a potassium chloride product.
In the invention, (1) the temperature of the initial hot solvent is increased by recycling heat in the cooling and crystallization process, so that high-concentration MgCl is ensured2The type thermal solvent (near saturation) has extremely strong uniformity and stability; (2) the advantage of increased solubility of potassium chloride and magnesium chloride can be fully exerted by high-temperature selective hot melting, so that the high-sodium carnallite is fully dissolved; meanwhile, the liquid-solid mass ratio of the high-sodium carnallite to the hot solvent is controlled, so that only a small amount of sodium chloride enters the saturated solution, and selective dissolution of different phases in the high-sodium carnallite is realized; (3) by controlling the concentration of the hot solvent and the liquid-solid mass ratio in the hot dissolving process, the composition of a high-temperature potassium-rich saturated liquid obtained by hot dissolving is favorable to be close to the three-phase common saturation point of carnallite, potassium chloride and sodium chloride, the composition stability of the saturated liquid is strong, and the independent separation of potassium chloride in the cooling crystallization process is favorable; (4) the temperature difference between the hot melting and the cooling crystallization is large, so that the maximum separation of potassium chloride in the high-temperature potassium-rich saturated solution is ensured; (5) the cooling crystallization process adopts a step type slow cooling in a closed space and controlsThe amount of fresh water and/or refined potassium mother liquor is supplemented, so that sodium chloride, magnesium chloride and other salts in the high-temperature potassium-rich saturated solution can be always stably remained in a liquid phase in the cooling process, and only potassium chloride is separated out; (6) the low-temperature potassium saturated solution is evaporated at high temperature to separate out sodium chloride, so that the content of the sodium chloride in the low-sodium carnallite in the subsequent stage is reduced, and the quality of the potassium chloride in the artificial sylvite is improved; (7) based on the composition of the artificial sylvite, the potassium chloride is prepared by selective dissolution at low temperature once, so that the yield of the potassium chloride at the stage can reach 75-85 percent without adopting circulating thermosol crystallization treatment; (8) the hot melting temperature is the same as the evaporation temperature, and the cooling crystallization temperature is the same as the carnallite decomposition temperature, the sylvine salt dissolution temperature and the washing temperature, thereby being beneficial to perfect conjunction of the process stage.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention utilizes the characteristics of different solubility change trends of potassium chloride, magnesium chloride and sodium chloride to cooperate with MgCl2The solvent is used for carrying out selective hot-dissolving treatment on the high-sodium carnallite, and the mass ratio of sodium chloride to potassium chloride in the obtained potassium-rich saturated solution is only 0.30: 1-0.35: 1, so that the separation of the sodium chloride and the carnallite is rapidly realized, and compared with the traditional decomposition process, the selective hot-dissolving process has the advantages of better separation effect and water resource saving;
(2) the invention ensures the stability of the composition of the high-temperature potassium-rich saturated solution in the hot melting process and the unsaturation degree of other salts such as sodium chloride, magnesium chloride and the like in the cooling crystallization process through process control, and is beneficial to the high-efficiency and high-quality precipitation of potassium chloride;
(3) based on the low-sodium characteristic of the high-temperature potassium-rich saturated solution, on the basis of further removing sodium chloride by the subsequent process, the mass ratio of sodium chloride to potassium chloride in the low-sodium carnallite obtained by evaporation is only 0.3: 1-0.4: 1, the quality of the carnallite is high, further development is facilitated, and the yield of the potassium chloride is improved;
(4) the artificial sylvite is prepared by selective dissolving at low temperature once, so that the high yield and high quality of potassium chloride are ensured, and unnecessary energy consumption and impurity accumulation in repeated circulating hot-melt crystallization treatment of the sylvite are avoided;
(5) the invention has the advantages of no strict technological conditions, no extreme high or low temperature, and no other special condition setting, and is convenient for popularization and implementation of the technology.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a technical flow diagram of a prior art intercooling decomposition-flotation process;
FIG. 2 is a technical flow diagram of a reverse flotation-cold crystallization process in the prior art;
FIG. 3 is a technical flow chart of a brine-adding controlled-rate crystallization method in the prior art;
FIG. 4 is a flow chart of a prior art solarization process;
FIG. 5 is a prior art process flow diagram of a cold decomposition-hot melt crystallization process;
FIG. 6 is a schematic flow diagram of a process for producing low sodium carnallite and potassium chloride using high sodium carnallite in accordance with one embodiment of the present invention.
Detailed Description
The core stage of the technology for preparing potassium chloride from carnallite ore is the process of decomposing to obtain artificial sylvine, and the yield and grade of potassium chloride are closely related to the content of sodium chloride in the carnallite ore. The higher the sodium chloride content, the lower the potassium chloride yield and grade.
In view of the defects of the prior art, the inventor of the present invention provides a technical scheme of the present invention through long-term research and a large amount of practice, wherein the technical scheme is mainly that high-sodium carnallite is selectively hot-dissolved to obtain low-sodium potassium-rich saturated liquid, and then the saturated liquid is cooled and crystallized to prepare a potassium chloride product; and the subsequent evaporation is carried out to obtain sodium chloride and low-sodium carnallite, so as to further prepare potassium chloride products, improve the yield of potassium chloride and realize the efficient development and utilization of potassium resources in the high-sodium carnallite. The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
One aspect of an embodiment of the present invention provides a method for preparing low-sodium carnallite and potassium chloride from high-sodium carnallite, which includes:
will be rich in MgCl2Mixing the substances with fresh water and carrying out preheating treatment to obtain a hot solvent;
carrying out selective hot-melting treatment on the high-sodium carnallite by using the hot solvent to obtain high-temperature potassium-rich saturated solution;
performing stepped closed cooling crystallization on the high-temperature potassium-rich saturated liquid to prepare crude potassium chloride and low-temperature potassium saturated liquid;
and evaporating the low-temperature potassium saturated solution to obtain low-sodium carnallite, and then decomposing and selectively dissolving the obtained low-sodium carnallite to obtain potassium chloride.
In some more specific embodiments, the method for preparing low sodium carnallite and potassium chloride by using high sodium carnallite specifically comprises the following steps:
(1) will be rich in MgCl2Mixing the substances with fresh water and preheating to 40-50 ℃ to obtain a hot solvent, wherein MgCl is contained in the hot solvent2The concentration of (A) is 25-30 wt%;
(2) contacting the hot solvent obtained in the step (1) with high-sodium carnallite, carrying out selective hot-melting treatment at 75-100 ℃, and then carrying out solid-liquid separation on the obtained mixture to obtain high-temperature potassium-rich saturated solution and solid-phase sodium chloride;
(3) step-type closed cooling crystallization is carried out on the high-temperature potassium-rich saturated liquid obtained in the step (2) while fresh water is supplemented, and then solid-liquid separation treatment is carried out to obtain crude potassium chloride and low-temperature potassium saturated liquid;
(4) evaporating the low-temperature potassium saturated liquid obtained in the step (3) at 75-100 ℃ to obtain low-sodium carnallite and old brine, and then performing fresh water decomposition and selective dissolution treatment on the obtained low-sodium carnallite while supplementing fresh water to obtain crude potassium chloride.
In some more specific embodiments, the MgCl-enriched material is MgCl2The substance (b) includes any one of old brine and bischofite, but is not limited thereto.
Further, the mass ratio of the hot solvent to the high-sodium carnallite is 2: 1-3: 1.
Further, the high-sodium carnallite comprises the following components in percentage by mass: 30-60 wt% of NaCl, 10-20 wt% of KCl, and MgCl215～30wt％、H2O 15～30wt％。
Further, the high-temperature potassium-rich saturated liquid comprises the following components in percentage by mass: 1.8-2.0 wt% of NaCl, 5.4-6.4 wt% of KCl, and MgCl228～30wt％、H2O 61～65wt％。
Furthermore, the mass ratio of NaCl to KCl in the high-temperature potassium-rich saturated solution is 0.30: 1-0.35: 1.
In some more specific embodiments, the step-wise closed cooling crystallization treatment in step (3) comprises: cooling the high-temperature potassium-rich saturated liquid to a cooling crystallization temperature at a selected cooling rate while replenishing fresh water, and performing stepped cooling and closed cooling crystallization, wherein the cooling crystallization temperature is 10-25 ℃, and the selected cooling rate is 0.3-0.5 ℃/min; preferably, the mass ratio of the fresh water to the high-temperature potassium-rich saturated liquid is 0.15: 1-0.20: 1; by controlling the addition amount of the fresh water, the method ensures that other salts such as sodium chloride, magnesium chloride and the like in the high-temperature potassium-rich saturated liquid can be stably remained in a liquid phase all the time in the cooling process, and only potassium chloride is separated out.
Further, the method further comprises: and preheating the hot solvent by using the heat released in the stepped closed cooling crystallization treatment process.
In some more specific embodiments, the crude potassium chloride in step (3) has a potassium chloride content of 80 to 85 wt%.
Further, the low temperature potassiumThe saturated liquid comprises the following components in percentage by mass: 1.5-2.0 wt% of NaCl, 2.5-3.5 wt% of KCl, and MgCl225～27wt％、H2O 69～70wt％。
In some more specific embodiments, step (4) specifically includes:
(4.1) evaporating the low-temperature potassium saturated liquid obtained in the step (3) at 75-100 ℃, and then carrying out solid-liquid separation to obtain a high-temperature carnallite saturated liquid and solid-phase sodium chloride, wherein the high-temperature carnallite saturated liquid comprises the following components in percentage by mass: 1.5-1.7 wt% of NaCl, 3.1-4.2 wt% of KCl, and MgCl230～34wt％、H2O 61～65wt％；
(4.2) continuously evaporating the obtained high-temperature carnallite saturated liquid at 75-100 ℃, and then carrying out solid-liquid separation to obtain low-sodium carnallite and aged brine, wherein the aged brine comprises the following components in percentage by mass: NaCl 0.4-0.5 wt%, KCl 0.4-0.5 wt%, MgCl239～42wt％、H2O57-60 wt%, wherein the mass ratio of sodium chloride to potassium chloride in the low-sodium carnallite is 0.3: 1-0.4: 1;
(4.3) mixing the obtained low-sodium carnallite with fresh water, decomposing at 10-25 ℃, and performing solid-liquid separation to obtain artificial sylvine and low-temperature carnallite saturated liquid, wherein the consumption of the fresh water is 1.1-1.2 times of the consumption calculated by a phase diagram, and the low-temperature carnallite saturated liquid comprises the following components in percentage by mass: 1.5-2.0 wt% of NaCl, 2.5-3.5 wt% of KCl, and MgCl225～27wt％、H2O69-70 wt%, wherein the artificial sylvite comprises the following components in percentage by mass: 20-25 wt% of NaCl and 75-80 wt% of KCl;
(4.4) mixing the obtained artificial sylvite with fresh water for selective dissolution treatment, and then carrying out solid-liquid separation to obtain crude potassium chloride and low-temperature sylvite saturated liquid, wherein the content of potassium chloride in the crude potassium chloride is 85-90 wt%, and the low-temperature sylvite saturated liquid comprises the following components in percentage by mass: 18-20 wt% of NaCl, 7-11 wt% of KCl and H2O69-75 wt%, the fresh water and artificial sylvineThe liquid-solid mass ratio is 0.7: 1-1.0: 1; preferably, the yield of potassium chloride in the crude potassium chloride prepared by the selective dissolution treatment and the solid-liquid separation is 75-85%.
Further, the method further comprises: and (3) preparing the aged brine in the step (4.2) to form the hot solvent.
Further, the method further comprises: and (4) preparing the low-temperature carnallite saturated liquid in the step (4.3) to form the thermal solvent.
Further, the method further comprises: and (5) adopting the saturated solution of the low-temperature sylvite in the step (4.4) to supplement the hot solvent.
In the invention, the hot solvent comprises any one or the combination of more than two of old brine, bischofite and low-temperature carnallite saturated solution, and the low-temperature sylvine saturated solution generated in the step (4.4) can be used for supplementing the hot solvent.
In some more specific embodiments, the method further comprises: and (4) washing, carrying out solid-liquid separation and drying treatment on the crude potassium chloride obtained in the step (3) and the step (4) to obtain a potassium chloride product.
Further, the washing liquid used in the washing process includes fresh water, and is not limited thereto.
Further, the liquid-solid mass ratio of the washing liquid to the crude potassium chloride is 0.20: 1-0.30: 1.
Further, the temperature of the washing treatment is 10-25 ℃.
Further, while the stepped closed cooling crystallization treatment is carried out, adding the refined potassium mother liquor obtained by the solid-liquid separation treatment into the system, and adding the refined potassium mother liquor into the stepped closed cooling crystallization treatment system.
Further, controlling the mass ratio of the refined potassium mother liquor to the high-temperature potassium-rich saturated liquor to be 0.15: 1-0.20: 1; by controlling the addition amount of the refined potassium mother liquor, sodium chloride, magnesium chloride and other salts in the high-temperature potassium-rich saturated liquor can be ensured to be stably remained in a liquid phase all the time in the cooling process, and only potassium chloride is separated out.
As one of more specific embodiments of the present invention, referring to fig. 6, the method for preparing potassium chloride by using high-sodium carnallite may specifically include the following steps:
(1) stage one: and (4) preparing a hot solvent. The hot solvent is MgCl-rich in aged brine, bischofite, low-temperature carnallite saturated solution or low-temperature sylvine saturated solution2The salt ore body is mixed with fresh water, wherein MgCl is contained in the hot solvent2The percentage concentration of (A) is 25-30%. And absorbing energy released by cooling the high-temperature potassium-rich saturated liquid, and preheating the hot solvent, wherein the temperature of the preheated hot solvent is 40-50 ℃.
(2) And a second stage: and (4) selectively hot-dissolving the high-sodium carnallite to obtain high-temperature potassium-rich saturated solution. And (3) selectively hot-dissolving the high-sodium carnallite by using a hot solvent, wherein the hot-dissolving temperature is 75-100 ℃, the liquid-solid mass ratio of the hot solvent to the high-sodium carnallite is controlled to be 2: 1-3: 1, and the hot solution phase composition is kept stable to serve as a sign for hot-dissolving completion. After the selective hot melting is finished, carrying out solid-liquid separation to obtain high-temperature potassium-rich saturated solution, wherein the high-temperature potassium-rich saturated solution comprises 1.8-2.0% of NaCl, 5.4-6.4% of KCl and MgCl228％～30％，H2O61-65%; the remaining solid phase is sodium chloride, and the carnallite completely enters saturated liquid.
(3) And a third stage: closing the high-temperature potassium-rich saturated liquid, cooling and crystallizing to obtain crude potassium chloride. Controlling the cooling crystallization temperature to be 10-25 ℃, the cooling rate to be 0.3-0.5 ℃/min, carrying out step-type closed cooling crystallization on the high-temperature potassium-rich saturated liquid, simultaneously supplementing a certain amount of fresh water (or refined potassium mother liquid), ensuring that a solid phase separated out by crystallization is only potassium chloride, and controlling the mass ratio of the supplemented fresh water (or refined potassium mother liquid) to the high-temperature potassium-rich saturated liquid to be 0.15: 1-0.20: 1. The solid phase obtained after solid-liquid separation is crude potassium chloride, and the content of the potassium chloride is 80-85%; the residual liquid is low-temperature saturated potassium solution comprising NaCl 1.5-2.0 wt%, KCl 2.5-3.5 wt%, and MgCl225％～27％，H2O 69％～70％。
(4) And a fourth stage: evaporating the low-temperature potassium saturated solution at high temperature to separate out sodium chloride, and taking the residual solution as the high-temperature carnallite saturated solution. And controlling the evaporation temperature to be the same as the second stage hot melting temperature, and evaporating the low-temperature potassium saturated solution. When the composition of the residual liquid is 1.5-1.7% of NaCl, 3.1-4.2% of KCl and MgCl230％～34％，H2And stopping evaporation when the content of O is between 61 and 65 percent. And (4) performing solid-liquid separation, wherein the residual liquid at the moment is the high-temperature carnallite saturated liquid, and the separated solid phase is sodium chloride.
(5) And a fifth stage: evaporating the high-temperature carnallite saturated liquid at high temperature to separate out low-sodium carnallite. And controlling the evaporation temperature to be the same as the second stage hot melting temperature, and evaporating the high-temperature carnallite saturated solution. When the composition of the residual liquid is 0.4-0.5% of NaCl, 0.4-0.5% of KCl and MgCl239％～42％，H2And stopping evaporation when the content of O is 57-60%. Solid-liquid separation, wherein the residual liquid is the aged brine; the precipitated solid phase is carnallite which comprises 7-10 percent of NaCl, 21-25 percent of KCl and MgCl230％～35％，H230-40% of O, which is low-sodium carnallite, and the mass ratio of sodium chloride to potassium chloride is only 0.3: 1-0.4: 1. And returning the aged brine to the first stage for reuse.
(6) And a sixth stage: decomposing the low-sodium carnallite at low temperature to obtain the artificial sylvite. And controlling the decomposition temperature to be the same as the cooling crystallization temperature in the third stage, decomposing the low-sodium carnallite by using the fresh water, wherein the addition amount of the fresh water is 1.1-1.2 times of the theoretical fresh water amount (the theoretical fresh water amount is obtained by calculating through a phase diagram). After solid-liquid separation, the obtained solid phase is artificial sylvine, and the components of the artificial sylvite are 20-25% of NaCl and 75-80% of KCl; the liquid phase is low-temperature carnallite saturated liquid which comprises 1.5-2.0 percent of NaCl, 2.5-3.5 percent of KCl and MgCl225％～27％，H2And O69-70 percent. And returning the low-temperature carnallite saturated liquid to the first stage for recycling.
(7) And selectively dissolving the artificial sylvite at low temperature to obtain crude potassium chloride. Adding fresh water to dissolve the artificial sylvite, wherein the liquid-solid mass ratio of the fresh water to the artificial sylvite is 0.7: 1-1.0: 1, wherein all sodium chloride and part of potassium chloride enter a liquid phase, the solid phase left after solid-liquid separation is crude potassium chloride, and the potassium chloride content is 85-90%; the liquid phase is low-temperature sylvine saturated liquid which comprises 18-20% of NaCl, 7-11% of KCl and H2And O69-75%. And returning the low-temperature sylvite saturated liquid to the first stage for recycling.
(8) Refining the crude potassium chloride to prepare a potassium chloride product. And mixing, washing and drying the crude potassium chloride obtained in the third stage and the crude potassium chloride obtained in the seventh stage to finally obtain a potassium chloride product. Wherein the liquid-solid mass ratio of the fresh water added in the washing to the crude potassium chloride is 0.20: 1-0.30: 1, and the washing temperature is the same as the crystallization temperature. And returning the washed fine potassium mother liquor to the third stage for recycling.
In the invention, the cooling crystallization temperature is the same as the washing temperature, which is favorable for perfect conjunction of the process stage.
In the present invention, MgCl is prepared by controlling the hot solvent2The concentration is 25% -30%, the solid-to-solid mass ratio of the potassium-enriched saturated liquid to the hot solution is 2: 1-3: 1, the composition of the high-temperature potassium-enriched saturated liquid obtained by hot dissolution is close to the three-phase common saturation point of carnallite, potassium chloride and sodium chloride, the composition stability of the saturated liquid is strong, and the potassium chloride can be separated out independently in the cooling crystallization process; the cooling crystallization process adopts stepped slow cooling in a closed space, and simultaneously the mass ratio of the supplemented fresh water and/or the refined potassium mother liquor to the high-temperature potassium-rich saturated liquid is controlled to be 0.15: 1-0.20: 1, so that sodium chloride, magnesium chloride and other salts in the high-temperature saturated liquid can be always stably remained in a liquid phase in the cooling process, and only potassium chloride is separated out; the low-temperature potassium saturated solution is evaporated at high temperature to separate out sodium chloride, so that the content of the sodium chloride in the low-sodium carnallite in the subsequent stage is reduced, and the quality of the potassium chloride in the artificial sylvite is improved; the yield of the potassium chloride in the stage can reach 75-85% only by adopting one-time low-temperature selective dissolution to prepare the potassium chloride from the artificial sylvite, and the circulating thermosol crystallization treatment is not needed.
The technical solutions of the present invention are further described in detail below with reference to several preferred embodiments and the accompanying drawings, which are implemented on the premise of the technical solutions of the present invention, and a detailed implementation manner and a specific operation process are provided, but the scope of the present invention is not limited to the following embodiments.
The experimental materials used in the examples used below were all available from conventional biochemical reagents companies, unless otherwise specified.
The following examples (examples 1-3) were all obtained by the following steps:
(1) and (4) preparing a hot solvent. The hot solvent is selected from old brine, bischofite, low temperature carnallite saturated solution or low temperature sylvine saturated solutionIsochoric enrichment of MgCl2Mixing the salt ore body with fresh water;
(2) selectively hot-dissolving the high-sodium carnallite to obtain high-temperature potassium-rich saturated solution;
(3) closing the high-temperature potassium-rich saturated liquid, cooling and crystallizing to obtain crude potassium chloride;
(4) evaporating the low-temperature potassium saturated solution at high temperature to separate out sodium chloride, and taking the residual solution as the high-temperature carnallite saturated solution
(5) Evaporating the high-temperature carnallite saturated liquid at high temperature to separate out low-sodium carnallite, and recycling old brine for preparing a hot solvent;
(6) decomposing low-sodium carnallite at low temperature to obtain artificial sylvine, and recovering saturated liquid of the low-temperature carnallite for preparing a hot solvent;
(7) selectively dissolving artificial sylvite at low temperature to obtain crude potassium chloride, wherein the liquid phase is low-temperature sylvite saturated liquid, and the low-temperature sylvite saturated liquid is recycled for preparing a hot solvent;
(8) and (3) refining the crude potassium chloride to prepare a potassium chloride product, mixing, washing and drying the crude potassium chloride obtained in the step (3) and the step (7) to finally obtain a potassium chloride product, and carrying out closed cooling crystallization on the washed refined potassium mother liquor used for high-temperature potassium-rich saturated liquid.
Example 1
Example 2
Example 3
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.
Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.
It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
Claims (10)
1. A method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite is characterized by comprising the following steps:
will be rich in MgCl2Mixing the substances with fresh water and carrying out preheating treatment to obtain a hot solvent;
carrying out selective hot-melting treatment on the high-sodium carnallite by using the hot solvent to obtain high-temperature potassium-rich saturated solution;
performing stepped closed cooling crystallization on the high-temperature potassium-rich saturated liquid to prepare crude potassium chloride and low-temperature potassium saturated liquid;
and evaporating the low-temperature potassium saturated solution to obtain low-sodium carnallite, and then decomposing and selectively dissolving the obtained low-sodium carnallite to obtain potassium chloride.
2. The method of claim 1 for producing low sodium carnallite and potassium chloride using high sodium carnallite, comprising:
(1) will be rich in MgCl2Mixing the substances with fresh water and preheating to 40-50 ℃ to obtain a hot solvent, wherein MgCl is contained in the hot solvent2The concentration of (A) is 25-30 wt%;
(2) contacting the hot solvent obtained in the step (1) with high-sodium carnallite, carrying out selective hot-melting treatment at 75-100 ℃, and then carrying out solid-liquid separation on the obtained mixture to obtain high-temperature potassium-rich saturated solution and solid-phase sodium chloride;
(3) step-type closed cooling crystallization is carried out on the high-temperature potassium-rich saturated liquid obtained in the step (2) while fresh water is supplemented, and then solid-liquid separation treatment is carried out to obtain crude potassium chloride and low-temperature potassium saturated liquid;
(4) evaporating the low-temperature potassium saturated liquid obtained in the step (3) at 75-100 ℃ to obtain low-sodium carnallite and old brine, and then performing fresh water decomposition and selective dissolution treatment on the obtained low-sodium carnallite while supplementing fresh water to obtain crude potassium chloride.
3. The process for preparing hypohalous and potassium chloride from high sodium carnallite according to claim 2 wherein said MgCl is enriched in step (1)2The substance(s) of (a) include old brine and/or bischofite.
4. The method for preparing low-sodium carnallite and potassium chloride by using high-sodium carnallite according to claim 2, characterized in that the mass ratio of the hot solvent to the high-sodium carnallite in the step (2) is 2: 1-3: 1;
and/or the high-sodium carnallite comprises the following components in percentage by mass: 30-60 wt% of NaCl, 78-20 wt% of KCl10, and MgCl215～30wt％、H2O 15～30wt％；
And/or the high-temperature potassium-rich saturated liquid comprises the following components in percentage by mass: 1.8-2.0 wt% of NaCl, 5.4-6.4 wt% of KCl, and MgCl228～30wt％、H261-65 wt% of O; preferably, the mass ratio of NaCl to KCl in the high-temperature potassium-rich saturated solution is 0.30: 1-0.35: 1.
5. The method for preparing low-sodium carnallite and potassium chloride from high-sodium carnallite according to claim 2, characterized in that the step-type closed cooling crystallization treatment in step (3) comprises: cooling the high-temperature potassium-rich saturated liquid to a cooling crystallization temperature at a selected cooling rate while replenishing fresh water, and performing stepped cooling and closed cooling crystallization, wherein the cooling crystallization temperature is 10-25 ℃, and the selected cooling rate is 0.3-0.5 ℃/min; preferably, the mass ratio of the fresh water to the high-temperature potassium-rich saturated liquid is 0.15: 1-0.20: 1; preferably, the method further comprises: and preheating the hot solvent by using the heat released in the stepped closed cooling crystallization treatment process.
6. The method for preparing low-sodium carnallite and potassium chloride from high-sodium carnallite according to claim 2, characterized in that the content of potassium chloride in the crude potassium chloride in step (3) is 80-85 wt%;
and/or the low-temperature potassium saturated liquid comprises the following components in percentage by mass: NaCl 1.5-2.0 wt%, KCl 2.5-3.5 wt%, MgCl225～27wt％、H2O 69～70wt％。
7. The method for preparing low-sodium carnallite and potassium chloride using high-sodium carnallite according to claim 2, characterized in that the step (4) comprises:
(4.1) evaporating the low-temperature potassium saturated liquid obtained in the step (3) at 75-100 ℃, and then carrying out solid-liquid separation to obtain a high-temperature carnallite saturated liquid and solid-phase sodium chloride, wherein the high-temperature carnallite saturated liquid comprises the following components in percentage by mass: 1.5-1.7 wt% of NaCl, 3.1-4.2 wt% of KCl, and MgCl230～34wt％、H2O 61～65wt％；
(4.2) continuously evaporating the obtained high-temperature carnallite saturated liquid at 75-100 ℃, and then carrying out solid-liquid separation to obtain low-sodium carnallite and aged brine, wherein the aged brine comprises the following components in percentage by mass: NaCl 0.4-0.5 wt%, KCl 0.4-0.5 wt%, MgCl239～42wt％、H2O57-60 wt%, wherein the mass ratio of sodium chloride to potassium chloride in the low-sodium carnallite is 0.3: 1-0.4: 1;
(4.3) mixing the obtained low-sodium carnallite with fresh water, decomposing at 10-25 ℃, and performing solid-liquid separation to obtain artificial sylvine and low-temperature carnallite saturated liquid, wherein the consumption of the fresh water is 1.1-1.2 times of the consumption calculated by a phase diagram, and the low-temperature carnallite saturated liquid comprises the following components in percentage by mass: 1.5-2.0 wt% of NaCl, 2.5-3.5 wt% of KCl, and MgCl225～27wt％、H2O69-70 wt%, wherein the artificial sylvite comprises the following components in percentage by mass: 20-25 wt% of NaCl and 75-80 wt% of KCl;
(4.4) mixing the obtained artificial sylvite with fresh water for selective dissolution treatment, and then carrying out solid-liquid separation to obtain crude potassium chloride and low-temperature sylvite saturated liquid, wherein the content of potassium chloride in the crude potassium chloride is 85-90 wt%, and the low-temperature sylvite saturated liquid comprises the following components in percentage by mass: 18-20 wt% of NaCl, 7-11 wt% of KCl and H2O69-75 wt%, wherein the liquid-solid mass ratio of the fresh water to the artificial sylvine is 0.7: 1-1.0: 1; preferably, the artificial sylvite is subjected to selective dissolution and solid-liquid separation treatmentThe yield of potassium chloride is then 75-85%.
8. The process of claim 7 for producing low sodium carnallite and potassium chloride using high sodium carnallite, further comprising: preparing the aged brine in the step (4.2) to form the hot solvent;
and/or, the method further comprises: preparing the low-temperature carnallite saturated liquid in the step (4.3) to form the thermal solvent;
and/or, the method further comprises: and (5) adopting the saturated solution of the low-temperature sylvite in the step (4.4) to supplement the hot solvent.
9. The process of claim 2 for producing low sodium carnallite and potassium chloride using high sodium carnallite, further comprising: and (4) washing, carrying out solid-liquid separation and drying treatment on the crude potassium chloride obtained in the step (3) and the step (4) to obtain a potassium chloride product.
10. The process of claim 9 for the production of low sodium carnallite and potassium chloride using high sodium carnallite, wherein: the washing liquid adopted in the washing treatment comprises fresh water; preferably, the liquid-solid mass ratio of the washing liquid to the crude potassium chloride is 0.20: 1-0.30: 1; preferably, the temperature of the washing treatment is 10-25 ℃;
and/or, the method further comprises: adding the refined potassium mother liquor obtained by the solid-liquid separation treatment into a closed cooling crystallization system while performing the stepped closed cooling crystallization treatment; preferably, the mass ratio of the refined potassium mother liquor to the high-temperature potassium-rich saturated liquor is 0.15: 1-0.20: 1.
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