阅读说明：本技术 硫酸盐型光卤石制备硫酸钾镁肥、氯化钾及硫酸钾的方法 (Method for preparing potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate by using sulfate type carnallite ) 是由 王敏 时历杰 于 2020-05-06 设计创作，主要内容包括：本发明公开了一种硫酸盐型光卤石制备硫酸钾镁肥、氯化钾及硫酸钾的方法。所述方法包括：首先以阴离子型浮选剂对硫酸盐型光卤石矿进行浮选处理,获得钾硫混盐精矿和氯化物型尾矿；之后以反浮选药剂对所述氯化物型尾矿进行反浮选处理,获得氯化镁型尾矿和氯化钠；最后将所述氯化镁型尾矿进行洗涤精制、分解处理,获得氯化钾。本发明采用双浮选分离技术,为同时高效制取氯化钾和硫酸钾镁肥产品提供原料基础；同时采用“反浮选-洗涤水氯镁石-分解”技术,先后除去氯化物型尾矿中的氯化钠和氯化镁,有利于获得光卤石精矿及高效制取高品位氯化钾产品。本发明工艺流程简单,仅利用浮选技术实现不同矿物的分离,便于技术的推广和实施。(The invention discloses a method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate by using sulfate type carnallite. The method comprises the following steps: firstly, carrying out flotation treatment on sulfate type carnallite by using an anionic flotation agent to obtain potassium-sulfur mixed salt concentrate and chloride type tailings; then, carrying out reverse flotation treatment on the chloride type tailings by using a reverse flotation reagent to obtain magnesium chloride type tailings and sodium chloride; and finally, washing, refining and decomposing the magnesium chloride type tailings to obtain potassium chloride. The invention adopts the double flotation separation technology to provide a raw material foundation for simultaneously and efficiently preparing potassium chloride and potassium magnesium sulfate fertilizer products; and simultaneously, the technology of 'reverse flotation-washing bischofite-decomposition' is adopted to remove sodium chloride and magnesium chloride in chloride tailings in sequence, thereby being beneficial to obtaining carnallite concentrate and efficiently preparing high-grade potassium chloride products. The invention has simple process flow, realizes the separation of different minerals by only utilizing the flotation technology and is convenient for the popularization and the implementation of the technology.)

1. A method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate by using sulfate type carnallite is characterized by comprising the following steps:

(1) carrying out flotation treatment on sulfate type carnallite by using an anionic flotation agent to obtain potassium-sulfur mixed salt concentrate and chloride type tailings, wherein the potassium-sulfur mixed salt concentrate comprises the following components in percentage by mass: 1-3 wt% of halite, 5.0-7.5 wt% of carnallite, 57.5-72.0 wt% of kainite and 20-34 wt% of epsomite, wherein the chloride tailings comprise the following components in percentage by mass: 11-18 wt% of halite, 36.5-50.0 wt% of carnallite, 33.5-40.0 wt% of bischofite, 3-5 wt% of kainite and 0.5-2.5 wt% of epsomite;

(2) carrying out reverse flotation treatment on the chloride type tailings by using a reverse flotation reagent to obtain magnesium chloride type tailings and sodium chloride, wherein the magnesium chloride type tailings comprise the following components in percentage by mass: 2-3 wt% of halite, 42-55 wt% of carnallite, 40-52 wt% of bischofite, 2-3 wt% of kainite and 0-1 wt% of epsomite;

(3) washing, refining and decomposing the magnesium chloride type tailings to obtain potassium chloride, wherein the potassium chloride comprises the following components in percentage by mass: NaCl0.5-1.0 wt%, KCl 94-97 wt%, MgCl₂1.0～1.5wt％。

2. The method of claim 1, wherein: the anionic flotation agent in the step (1) comprises an alkyl sulfonate anionic collector and/or an alkyl sulfate anionic collector;

and/or the flotation medium used in the flotation treatment is a saturated solution of sodium chloride, schoenite, potassium chloride and epsomite.

3. The method of claim 1, wherein: the reverse flotation reagent in the step (2) comprises an alkyl morpholine collector;

and/or the flotation medium used in the reverse flotation treatment is saturated solution of sodium chloride, potassium chloride and carnallite;

and/or the magnesium chloride type tailings are extremely low-sodium magnesium chloride type minerals.

4. The method according to claim 1, wherein step (3) comprises in particular:

washing and separating the magnesium chloride type tailings obtained in the step (2) to obtain carnallite concentrate and magnesium chloride saturated liquid;

decomposing the carnallite concentrate with fresh water at 10-25 ℃ to obtain crude potassium chloride and saturated carnallite solution;

and washing, solid-liquid separating and drying the obtained crude potassium chlorideAnd obtaining the potassium chloride, wherein the carnallite concentrate comprises the following components in percentage by mass: 2-5 wt% of NaCl, 23-25 wt% of KCl, and MgCl₂32～33wt％、MgSO₄0.5-1.5 wt%, wherein the saturated magnesium chloride solution comprises the following components in percentage by mass: NaCl 0.15-0.50 wt%, KCl 0.07-0.15 wt%, MgCl₂28～33wt％、MgSO₄2-3 wt%; preferably, the purity of the carnallite concentrate is 85-93 wt%.

5. The method according to claim 4, wherein the conditions of the washing treatment of the magnesium chloride type tailings comprise: the temperature is 10-25 ℃, and the time is 10-20 min; preferably, the washing liquid used in the washing treatment comprises fresh water; preferably, the mass ratio of the washing liquid to the magnesium chloride tailings is 0.09: 1-0.13: 1;

and/or the amount of fresh water used for decomposing the carnallite concentrate is 1.10-1.15 times of the amount obtained by calculating through a phase diagram;

and/or, the method further comprises: and (3) recovering the carnallite saturated liquid to be used as the flotation medium for the reverse flotation treatment in the step (2).

6. The method according to claim 4, wherein the washing liquid used in the crude potassium chloride washing treatment comprises fresh water; preferably, the liquid-solid mass ratio of the washing liquid to the crude potassium chloride is 0.15: 1-0.20: 1; preferably, the temperature of the washing treatment is 10-15 ℃;

and/or, the method further comprises: and recovering the potassium chloride washing liquid after the coarse potassium chloride washing treatment for decomposing the carnallite concentrate.

7. The method of claim 1, further comprising:

mixing the potassium-sulfur mixed salt concentrate obtained in the step (1) with fresh water for conversion treatment, separating to obtain crude schoenite and schoenite conversion mother liquor, and refining the obtained crude schoenite to obtain the potash magnesium sulphate fertilizer, wherein the potash magnesium sulphate fertilizer is preparedThe potash magnesium sulphate fertilizer comprises the following components in percentage by mass: NaCl 0.2-0.5 wt%, K₂SO₄50～55wt％、MgSO₄23～27wt％；

And (3) reacting a mixed reaction system containing the potash magnesium sulphate fertilizer, the potassium chloride obtained in the step (3) and fresh water to obtain crude potassium sulphate, and then refining to obtain the potassium sulphate, wherein the potassium sulphate comprises the following components in percentage by mass: NaCl 0.5-1.0 wt%, KCl 0.5-1.0 wt%, and K₂SO₄92～95wt％、MgSO₄2～4wt％。

8. The method according to claim 7, wherein the fresh water used in the conversion treatment of the potassium-sulfur mixed salt concentrate is 1.15 to 1.20 times of the fresh water obtained by calculation through a phase diagram;

and/or, the method further comprises: recovering the picromerite conversion mother liquor and solarizing to form potassium mixed salt;

and/or, the method further comprises: recovering the picromerite conversion mother liquor as a flotation medium used in flotation treatment;

and/or the refining treatment of the crude schoenite comprises the following steps: washing, separating and drying the obtained crude picromerite to obtain a potash magnesium sulphate fertilizer; preferably, the washing liquid used in the washing treatment comprises fresh water; more preferably, the liquid-solid mass ratio of the washing liquid to the crude schoenite is 0.15: 1-0.25: 1; preferably, the method further comprises: and recycling the picromerite washing liquid generated by the washing treatment, mixing the picromerite washing liquid with the potassium-sulfur mixed salt concentrate, and performing conversion treatment to prepare crude picromerite.

9. The method according to claim 7, wherein the amount of the fresh water in the mixed reaction system is 1.1 to 1.2 times of the amount calculated by a phase diagram;

and/or, the method further comprises: recovering potassium sulfate conversion mother liquor reacted by the mixed reaction system, mixing the potassium sulfate conversion mother liquor with the potassium-sulfur mixed salt concentrate, and performing conversion treatment to prepare coarse schoenite;

and/or the content of potassium sulfate in the crude potassium sulfate is 85-90 wt%;

and/or the crude potassium sulfate refining treatment comprises the following steps: washing, separating and drying the crude potassium sulfate to obtain potassium sulfate; preferably, the washing liquid used in the washing treatment comprises fresh water; more preferably, the liquid-solid mass ratio of the washing liquid to the crude potassium sulfate is 0.20: 1-0.30: 1; preferably, the method further comprises: the potassium sulfate washing liquid generated by the washing treatment is recycled for preparing potassium sulfate.

10. The method of claim 7, further comprising: recovering the carnallite saturated liquor as described in claim 4 mixed with said potassic-sulfur mixed salt concentrate and subjected to a conversion treatment for the preparation of crude schoenite.

Technical Field

The invention belongs to the technical field of inorganic salt industry, and particularly relates to a method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate by using sulfate type 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% of the total amount of the potassium fertilizer; there are also various chlorine-free potassium fertilizers such as sulfate type (potassium sulfate, potash magnesium sulfate fertilizer), nitrate type (potassium nitrate), carbonate type (potassium carbonate), phosphate type (monopotassium phosphate) and the like. The raw materials for preparing the potassium chloride fertilizer mainly comprise chloride type sylvine and carnallite ore, and the potassium chloride can also be prepared by utilizing sulfate type carnallite ore. The sulfate type carnallite ore comprises halite (NaCl), carnallite (Car) and bischofite (Bis), and also contains a certain amount of epsomite (MgSO)₄·nH₂O), kainite (Kai) and other sulfate phases, and the composition ranges of the sulfate phases are 7-12% of NaCl, 25-33% of Car, 20-25% of Bis, 25-30% of Kai and MgSO₄·nH₂O 8％～15％。

The key of the technology for preparing the potassium chloride by utilizing the sulfate type carnallite ore is to avoid the influence of sulfate radicals. US20110008243a1, CN102421707B and CN103073029B adopt desulfurizing agents (calcium hydroxide, calcium chloride, ammonia evaporation waste liquid, etc.) to perform desulfurization modification, so that the desulfurizing agents are changed into chloride type, and then carnallite or potassium chloride is obtained to prepare potassium chloride products. In patent CN104477941B, potassium chloride is prepared by separating out epsomite of different crystal water by low-temperature freezing or high-temperature evaporation, and then evaporating to obtain carnallite. Patents CN100515946C and CN104891532A use saturated magnesium chloride solution to convert sulfate at high or low temperature into carnallite, and then to produce potassium chloride. Patent CN1248966C adopts halogen blending technology to obtain low-sodium carnallite, and then potassium chloride products are obtained. Patents CN106517250B, CN106430248B and CN106517251B utilize nanofiltration membrane to separate sulfate radicals at high rejection rate of divalent ions, and combine with reverse flotation or hot melt crystallization technology to prepare potassium chloride products. Under the influence of sulfate phase, the solid phase actually obtained in the direct hydrolysis reaction process of sulfate type carnallite ore is picromerite, and the sulfate type potash fertilizer is prepared by the picromerite. The patent CN100488874C adopts the technology of 'transformation + self decomposition' to obtain the potash magnesium sulphate fertilizer and the potash potassium sulphate product in turn. Patents CN1255320C, CN1810730B, CN104477943B and CN107963914A, etc. adopt the technology of "conversion + anion collector flotation" to process and obtain potash magnesium sulphate fertilizer, and continue to decompose or react with potash chloride to obtain potash sulphate product. The potash magnesium sulphate fertilizer can also be prepared by adopting the technology of 'conversion + reverse flotation' or 'reverse flotation sodium removal + conversion'. Patents CN1810729B, CN101927214B and CN104193425B adopt the positive and negative ion collecting agent succession or mixed flotation technology to obtain potassium salt concentrate, and then prepare potash magnesium sulphate fertilizer or potassium sulphate product by conversion. The process for preparing the potash magnesium sulphate fertilizer, the potassium chloride and the potassium sulphate by utilizing the sulfate type carnallite ore simultaneously has less technology. And only CN201810089886.X adopts the technology of 'conversion + anion collector flotation + tailing cation collector flotation' to float sequentially to obtain potash magnesium sulphate fertilizer and potassium chloride products. In the preparation of potassium chloride from sulfate type carnallite, other technologies (such as desulfurization, temperature change, brine blending and membrane method) are required to be introduced to separate sulfate at the present stage, so that the sulfate cannot be fully utilized. The key point of the technology for preparing the potash magnesium sulphate fertilizer is that the ratio of the sulphur to the potassium of the sulphate type carnallite ore needs to be adjusted to a potash magnesium sulphate fertilizer area in the conversion process, and other inorganic salts (such as common potassium chloride, sodium sulfate and the like) need to be added for adjustment. In the conversion process of only adding fresh water, magnesium chloride type phases such as carnallite and bischofite and sulfate type phases such as kainite and epsomite are mutually influenced, so that the yield of potassium in the conversion process is greatly reduced. Meanwhile, the introduced flotation technology has almost no flotation capacity on phases of carnallite, bischofite and the like, so that the risk that the carnallite stays in tailings and is abandoned is easily caused, and potassium resources are lost.

Disclosure of Invention

The invention mainly aims to provide a method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulphate by using sulfate type 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 a potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate by using sulfate type carnallite, which comprises the following steps:

(1) carrying out flotation treatment on sulfate type carnallite by using an anionic flotation agent to obtain potassium-sulfur mixed salt concentrate and chloride type tailings, wherein the potassium-sulfur mixed salt concentrate comprises the following components in percentage by mass: 1 to 3 wt% of halite (NaCl), 5.0 to 7.5 wt% of carnallite (Car), 57.5 to 72.0 wt% of kainite (Kai), and epsomite (MgSO)₄·nH₂O) 20-34 wt%, wherein the chloride type tailings comprise the following components in percentage by mass: 11 to 18 wt% of halite (NaCl), 36.5 to 50.0 wt% of carnallite (Car), 33.5 to 40.0 wt% of bischofite (Bis), 3 to 5 wt% of kainite (Kai), and epsomite (MgSO)₄·nH₂O)0.5～2.5wt％；

(2) Carrying out reverse flotation treatment on the chloride type tailings by using a reverse flotation reagent to obtain magnesium chloride type tailings and sodium chloride, wherein the magnesium chloride type tailings comprise the following components in percentage by mass: 2-3 wt% of halite, 42-55 wt% of carnallite, 40-52 wt% of bischofite, 2-3 wt% of kainite and 0-1 wt% of epsomite;

(3) washing, refining and decomposing the magnesium chloride type tailings to obtain potassium chloride, wherein the potassium chloride comprises the following components in percentage by mass: NaCl0.5-1.0 wt%, KCl 94-97 wt%, MgCl₂1.0～1.5wt％。

Further, the method further comprises:

mixing the potassium-sulfur mixed salt concentrate obtained in the step (1) with fresh water for conversion treatment, separating to obtain crude picromerite and picromerite conversion mother liquor, and refining the obtained crude picromerite to obtain a potash magnesium sulphate fertilizer, wherein the potash magnesium sulphate fertilizer comprises the following components in percentage by mass: NaCl 0.2-0.5 wt%, K₂SO₄50～55wt％、MgSO₄23～27wt％；

And (3) reacting a mixed reaction system containing the potash magnesium sulphate fertilizer, the potassium chloride obtained in the step (3) and fresh water to obtain crude potassium sulphate, and then refining to obtain the potassium sulphate, wherein the potassium sulphate comprises the following components in percentage by mass: NaCl 0.5-1.0 wt%, KCl 0.5-1.0 wt％、K₂SO₄92～95wt％、MgSO₄2～4wt％。

In the invention, (1) before the potassium-sulfur mixed salt concentrate is converted, an anionic flotation agent is used for flotation of sulfate type carnallite, so that sodium chloride and magnesium chloride type phases in the carnallite are separated from sulfate type phases, the mutual conversion reaction influence between the sodium chloride and magnesium chloride type phases is avoided, and a raw material basis is provided for respectively and efficiently preparing potassium chloride and potassium magnesium sulfate fertilizer products; (2) the reverse flotation technology is preferentially adopted to remove the sodium chloride in the chloride type tailings, so that the decomposition yield of the carnallite can be improved, and the impurity influence of the sodium chloride in a potassium chloride product can be reduced; (3) aiming at the characteristics of the high-grade bischofite in the magnesium chloride type tailings, before decomposing the carnallite, the bischofite and the carnallite are preferentially separated by fresh water, and then high-grade carnallite concentrate is obtained; (4) the fresh water consumption in the relevant conversion, decomposition and reaction is calculated by utilizing the phase diagram data, thereby being beneficial to the corresponding regulation of the recycling of various mother liquids and ensuring the quality of the obtained product.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts double flotation separation technology to separate the sulfate type phase and the magnesium chloride type phase in the sulfate type carnallite, and provides a raw material basis for efficiently preparing potassium chloride and potash magnesium sulphate fertilizer products at the same time;

(2) before the potassium-sulfur mixed salt concentrate is converted, an anionic flotation agent is used for separating a magnesium chloride type phase and a sulfate type phase in sulfate type carnallite in a flotation mode, so that mutual influence of the magnesium chloride type phase and the sulfate type phase in the conversion is avoided, meanwhile, the ratio of potassium to sulfur in the sulfate type phase is adjusted to a potassium sulfate magnesium fertilizer area, other inorganic salts are not needed to be added for adjustment, and the potassium sulfate magnesium fertilizer can be efficiently prepared;

(3) the invention adopts the technology of 'reverse flotation-washing bischofite-decomposition' to remove sodium chloride and magnesium chloride in chloride tailings in sequence, which is beneficial to obtaining carnallite concentrate and efficiently preparing high-grade potassium chloride products;

(4) the invention has simple process flow, realizes the separation of different minerals by only utilizing the flotation technology and is convenient for the popularization and the 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 schematic flow diagram of a process for producing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulphate from sulphate-type carnallite in accordance with one embodiment of the present invention.

Detailed Description

The interaction of the magnesium chloride type phase and the sulfate type phase in the sulfate type carnallite ore in the conversion has great influence on the type and the yield of the prepared potash fertilizer.

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 great deal of practice, and aims to separate sulfate type carnallite ore by adopting a double flotation separation technology to obtain a sulfate type phase and a magnesium chloride type phase respectively, avoid the mutual influence of the magnesium chloride type phase and the sulfate type phase in the sulfate type carnallite ore in the conversion, efficiently prepare a potash magnesium sulphate fertilizer and potassium chloride simultaneously under the condition of not adding other inorganic salts, obtain a potash sulphate product, and realize the comprehensive development and utilization of the potassium resource of the sulfate type carnallite ore. 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 the embodiments of the present invention provides a method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulphate by using sulfate type carnallite, which comprises:

(1) carrying out flotation treatment on the sulfate type carnallite ore by using an anionic flotation agent to obtainObtaining potassium-sulfur mixed salt concentrate and chloride type tailings, wherein the potassium-sulfur mixed salt concentrate comprises the following components in percentage by mass: 1 to 3 wt% of halite (NaCl), 5.0 to 7.5 wt% of carnallite (Car), 57.5 to 72.0 wt% of kainite (Kai), and epsomite (MgSO)₄·nH₂O) 20-34 wt%, wherein the chloride type tailings comprise the following components in percentage by mass: 11 to 18 wt% of halite (NaCl), 36.5 to 50.0 wt% of carnallite (Car), 33.5 to 40.0 wt% of bischofite (Bis), 3 to 5 wt% of kainite (Kai), and epsomite (MgSO)₄·nH₂O)0.5～2.5wt％；

(2) Carrying out reverse flotation treatment on the chloride type tailings by using a reverse flotation reagent to obtain magnesium chloride type tailings and sodium chloride, wherein the magnesium chloride type tailings comprise the following components in percentage by mass: 2-3 wt% of halite, 42-55 wt% of carnallite, 40-52 wt% of bischofite, 2-3 wt% of kainite and 0-1 wt% of epsomite;

(3) washing, refining and decomposing the magnesium chloride type tailings to obtain potassium chloride, wherein the potassium chloride comprises the following components in percentage by mass: NaCl0.5-1.0 wt%, KCl 94-97 wt%, MgCl₂1.0～1.5wt％。

In some more specific embodiments, the anionic flotation agent in step (1) includes any one or a combination of two of alkyl sulfonate anionic collectors and alkyl sulfate anionic collectors, and is not limited thereto.

Further, the flotation medium used in the flotation treatment is a saturated solution of sodium chloride, schoenite, potassium chloride and epsomite.

In some more specific embodiments, the reverse flotation reagent in step (2) includes an alkyl morpholine collector, and is not limited thereto.

Further, the flotation medium used in the reverse flotation treatment is saturated solution of sodium chloride, potassium chloride and carnallite.

Further, the magnesium chloride type tailings are extremely low-sodium magnesium chloride type minerals.

In some more specific embodiments, step (3) specifically includes:

washing and separating the magnesium chloride type tailings obtained in the step (2) to obtain carnallite concentrate and magnesium chloride saturated liquid;

decomposing the carnallite concentrate with fresh water at 10-25 ℃ to obtain crude potassium chloride and saturated carnallite solution;

and washing, carrying out solid-liquid separation and drying treatment on the obtained crude potassium chloride to obtain the potassium chloride, wherein the carnallite concentrate comprises the following components in percentage by mass: 2-5 wt% of NaCl, 23-25 wt% of KCl, and MgCl₂32～33wt％、MgSO₄0.5-1.5 wt%, wherein the saturated magnesium chloride solution comprises the following components in percentage by mass: NaCl 0.15-0.50 wt%, KCl 0.07-0.15 wt%, MgCl₂28～33wt％、MgSO₄2～3wt％。

Further, the purity of the carnallite concentrate is 85-93 wt%.

Further, the conditions of the washing treatment of the magnesium chloride type tailings comprise: the temperature is 10-25 ℃, and the time is 10-20 min; preferably, the washing liquid used in the washing treatment comprises fresh water; preferably, the mass ratio of the washing liquid to the magnesium chloride tailings is 0.09: 1-0.13: 1.

Furthermore, the fresh water consumption of the carnallite concentrate for decomposition treatment is 1.10-1.15 times of that obtained by calculating through a phase diagram.

Further, the method further comprises: and (3) recovering the carnallite saturated liquid to be used as the flotation medium for the reverse flotation treatment in the step (2).

Further, the washing liquid adopted in the washing treatment of the crude potassium chloride comprises fresh water; preferably, the liquid-solid mass ratio of the washing liquid to the crude potassium chloride is 0.15: 1-0.20: 1; preferably, the temperature of the washing treatment is 10-15 ℃.

Further, the method further comprises: and recovering the potassium chloride washing liquid after the coarse potassium chloride washing treatment for decomposing the carnallite concentrate.

In some more specific embodiments, the method further comprises:

mixing the potassium-sulfur mixed salt concentrate obtained in the step (1) with fresh water for conversion treatment, separating to obtain crude picromerite and picromerite conversion mother liquor, and refining the obtained crude picromerite to obtain a potash magnesium sulphate fertilizer, wherein the potash magnesium sulphate fertilizer comprises the following components in percentage by mass: NaCl 0.2-0.5 wt%, K₂SO₄50～55wt％、MgSO₄23～27wt％；

And (3) reacting a mixed reaction system containing the potash magnesium sulphate fertilizer, the potassium chloride obtained in the step (3) and fresh water to obtain crude potassium sulphate, and then refining to obtain the potassium sulphate, wherein the potassium sulphate comprises the following components in percentage by mass: NaCl 0.5-1.0 wt%, KCl 0.5-1.0 wt%, and K₂SO₄92～95wt％、MgSO₄2～4wt％。

Furthermore, the fresh water consumption of the potassium-sulfur mixed salt concentrate conversion treatment is 1.15-1.20 times of the amount obtained through phase diagram calculation.

Further, the method further comprises: recovering the picromerite conversion mother liquor and solarizing to form potassium mixed salt.

Further, the method further comprises: and recovering the picromerite conversion mother liquor as a flotation medium used in flotation treatment.

Further, the refining treatment of the crude schoenite comprises the following steps: and washing, separating and drying the obtained crude picromerite to obtain the potash magnesium sulphate fertilizer.

Furthermore, the washing liquid adopted in the washing treatment comprises fresh water; more preferably, the liquid-solid mass ratio of the washing liquid to the crude schoenite is 0.15:1 to 0.25: 1.

Still further, the method further comprises: and recycling the picromerite washing liquid generated by the washing treatment, mixing the picromerite washing liquid with the potassium-sulfur mixed salt concentrate, and performing conversion treatment to prepare crude picromerite.

Furthermore, the amount of the fresh water in the mixed reaction system is 1.1-1.2 times of the amount obtained by calculating through a phase diagram.

Further, the method further comprises: and recovering the potassium sulfate conversion mother liquor reacted by the mixed reaction system, mixing the potassium sulfate conversion mother liquor with the potassium-sulfur mixed salt concentrate, and performing conversion treatment to prepare the crude picromerite.

Further, the content of potassium sulfate in the crude potassium sulfate is 85-90 wt%.

Further, the crude potassium sulfate refining treatment comprises the following steps: washing, separating and drying the crude potassium sulfate to obtain potassium sulfate; preferably, the washing liquid used in the washing treatment comprises fresh water; more preferably, the liquid-solid mass ratio of the washing liquid to the crude potassium sulfate is 0.20: 1-0.30: 1; preferably, the method further comprises: the potassium sulfate washing liquid generated by the washing treatment is recycled for preparing potassium sulfate.

Further, the method further comprises: and recovering the carnallite saturated liquid, mixing the carnallite saturated liquid with the potassium-sulfur mixed salt concentrate, and performing conversion treatment to prepare the crude picromerite.

As one of more specific embodiments of the present invention, referring to fig. 1, a method for preparing a potash magnesium sulphate fertilizer, potassium chloride and potassium sulfate from sulfate-type carnallite may specifically include the following steps:

(1) stage one: and (3) carrying out flotation separation on the sulfate type carnallite ore to obtain potassium-sulfur mixed salt concentrate and chloride type tailings. The flotation reagent is alkyl sulfonate or sulfate and other anionic collectors, and the flotation medium is sodium chloride, picromerite, potassium chloride and epsomite saturated solution. The potassium-sulfur mixed salt concentrate obtained by flotation comprises the following components: 1 to 3 percent of halite, 5.0 to 7.5 percent of carnallite, 57.5 to 72.0 percent of kainite and 20 to 34 percent of epsomite; the chloride type tailings consist of: 11 to 18 percent of rock salt, 36.5 to 50.0 percent of carnallite, 33.5 to 40.0 percent of bischofite, 3 to 5 percent of kainite and 0.5 to 2.5 percent of epsomite.

(2) And a second stage: and (4) converting the potassium-sulfur mixed salt concentrate to obtain coarse picromerite, washing and refining to prepare a potash magnesium sulphate fertilizer product. Fresh water, the picromerite washing solution, the potassium sulfate conversion mother solution and the carnallite saturated solution are converted into potassium-sulfur mixed salt concentrate to obtain the crude picromerite. Wherein the amount of converted water is 1.15-1.20 times of the theoretical fresh water input amount (the theoretical fresh water input amount)The amount is calculated from a phase diagram); the separated picromerite conversion mother liquor is returned to the first stage to be used as a flotation medium for recycling. And continuously washing and drying the coarse picromerite to obtain the potash magnesium sulphate fertilizer product. The liquid-solid mass ratio of the fresh water added in the washing to the crude schoenite is 0.15: 1-0.25: 1, and the washing solution of the schoenite obtained by washing is returned to the potassium-sulfur mixed salt concentrate conversion stage for recycling. The obtained potash magnesium sulphate fertilizer consists of NaCl 0.2-0.5% and K₂SO₄50％～55％，MgSO₄23％～27％。

(3) And a third stage: and (4) carrying out reverse flotation separation on the chloride type tailings to obtain magnesium chloride type tailings and sodium chloride. The reverse flotation agent is alkyl morpholine collector, and the flotation medium is saturated solution of sodium chloride, potassium chloride and carnallite (containing a small amount of epsomite). The flotation magnesium chloride type tailings comprise the following components: 2 to 3 percent of halite, 42 to 55 percent of carnallite, 40 to 52 percent of bischofite, 2 to 3 percent of kainite, 0 to 1 percent of epsomite and is a very low-sodium magnesium chloride type mineral.

(4) And a fourth stage: washing and refining the magnesium chloride type tailings to obtain carnallite concentrate. Washing the magnesium chloride tailings with fresh water, wherein the washing temperature is 10-25 ℃, the mass ratio of the washing fresh water to the magnesium chloride tailings is 0.09: 1-0.13: 1, and the washing time is 10-20 min. The solid phase remained after the solid-liquid separation is carnallite concentrate which comprises 2 to 5 percent of NaCl, 23 to 25 percent of KCl and MgCl₂32％～33％，MgSO₄0.5 to 1.5 percent; the purity of the carnallite concentrate reaches 85 to 93 percent; the residual liquid is saturated magnesium chloride liquid comprising NaCl 0.15-0.50 wt%, KCl 0.07-0.15 wt% and MgCl₂28％～33％，MgSO₄2％～3％。

(5) And a fifth stage: decomposing the carnallite concentrate, and refining to prepare a potassium chloride product. And decomposing the carnallite concentrate by fresh water and a potassium chloride washing solution to obtain crude potassium chloride. Wherein the decomposition temperature is the same as the washing temperature in the fourth stage, and the fresh water addition amount is 1.10-1.15 times of the theoretical fresh water amount (the theoretical fresh water amount is obtained by phase diagram calculation); and returning the separated saturated carnallite solution to the third stage as a flotation medium or to the potassium-sulfur mixed salt concentrate conversion stage for recycling. The crude potassium chloride is continuously washed and dried to obtain chlorideAnd (4) potassium products. Wherein the liquid-solid mass ratio of the fresh water added in the washing to the crude potassium chloride is 0.15: 1-0.20: 1, the washing temperature is the same as the decomposition temperature, and the potassium chloride washing liquid obtained by washing is returned to the carnallite concentrate decomposition stage for recycling. The obtained potassium chloride comprises 0.5-1.0% of NaCl, 94-97% of KCl and MgCl₂1.0％～1.5％。

(6) And a sixth stage: the potassium chloride reacts with potassium magnesium sulfate fertilizer to obtain coarse potassium sulfate, which is washed and refined to obtain potassium sulfate product.

And adding fresh water into the potash magnesium sulphate fertilizer and the potassium chloride product obtained in the second stage and the seventh stage for mixing reaction to obtain crude potassium sulphate. Wherein the reaction water amount is 1.1-1.2 times of the theoretical fresh water input amount (the theoretical fresh water input amount is obtained by phase diagram calculation); the potassium sulfate content is 85-90%; and returning the residual potassium sulfate conversion mother liquor to the potassium-sulfur mixed salt concentrate conversion stage for recycling. And washing and drying the coarse potassium sulfate to obtain a potassium sulfate product. Wherein the liquid-solid mass ratio of the fresh water added in the washing to the crude potassium sulfate is 0.20: 1-0.30: 1, and the potassium sulfate washing liquid obtained by washing is returned to the reaction stage of the potassium magnesium sulfate fertilizer and potassium chloride for recycling. The potassium sulfate comprises 0.5-1.0% of NaCl, 0.5-1.0% of KCl and K₂SO₄92％～95％，MgSO₄2％～4％。

In the invention, (1) before the conversion, an anionic flotation agent is used for flotation of sulfate type carnallite, so that sodium chloride and magnesium chloride type phases in the carnallite are separated from sulfate type phases, the mutual conversion reaction influence between the sodium chloride and magnesium chloride type phases is avoided, and a raw material basis is provided for simultaneously and efficiently preparing potassium chloride and potassium magnesium sulfate fertilizer products; (2) the reverse flotation technology is preferentially adopted to remove the sodium chloride in the chloride type tailings, so that the decomposition yield of the carnallite can be improved, and the impurity influence of the sodium chloride in a potassium chloride product can be reduced; (3) aiming at the characteristics of the high-grade bischofite in the magnesium chloride type tailings, before decomposing the carnallite, the bischofite and the carnallite are preferentially separated by fresh water, and then high-grade carnallite concentrate is obtained.

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 (3) carrying out flotation separation on the sulfate type carnallite ore to obtain potassium-sulfur mixed salt concentrate and chloride type tailings. The flotation reagent is alkyl sulfonate or sulfate and other anionic collectors, and the flotation medium is sodium chloride, picromerite, potassium chloride and epsomite saturated solution.

(2) And (4) converting the potassium-sulfur mixed salt concentrate to obtain coarse picromerite, washing and refining to prepare a potash magnesium sulphate fertilizer product. Fresh water, the picromerite washing solution, the potassium sulfate conversion mother solution and the carnallite saturated solution are converted into potassium-sulfur mixed salt concentrate to obtain the crude picromerite. Wherein the converted water amount is 1.15-1.20 times of the theoretical fresh water input amount (the theoretical fresh water input amount is obtained by phase diagram calculation); the separated picromerite conversion mother liquor is returned to the first stage to be used as a flotation medium for recycling. And continuously washing and drying the coarse picromerite to obtain the potash magnesium sulphate fertilizer product. The liquid-solid mass ratio of the fresh water added in the washing to the crude schoenite is 0.15: 1-0.25: 1, and the washing solution of the schoenite obtained by washing is returned to the potassium-sulfur mixed salt concentrate conversion stage for recycling.

(3) And (4) carrying out reverse flotation separation on the chloride type tailings to obtain magnesium chloride type tailings and sodium chloride. The reverse flotation agent is alkyl morpholine collector, and the flotation medium is saturated solution of sodium chloride, potassium chloride and carnallite (containing a small amount of epsomite).

(4) Washing and refining the magnesium chloride type tailings to obtain carnallite concentrate.

(5) Decomposing the carnallite concentrate, and refining to prepare a potassium chloride product. And decomposing the carnallite concentrate by fresh water and a potassium chloride washing solution to obtain crude potassium chloride. And continuously washing and drying the crude potassium chloride to 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 0.15: 1-0.20: 1, the washing temperature is the same as the decomposition temperature, and the potassium chloride washing liquid obtained by washing is returned to the carnallite concentrate decomposition stage for recycling.

(6) The potassium chloride reacts with potassium magnesium sulfate fertilizer to obtain coarse potassium sulfate, which is washed and refined to obtain potassium sulfate product. And (3) adding fresh water into the potash magnesium sulphate fertilizer and the potassium chloride product obtained in the step (2) and the step (7) for mixing reaction to obtain crude potassium sulphate. Wherein the reaction water amount is 1.1-1.2 times of the theoretical fresh water input amount (the theoretical fresh water input amount is obtained by phase diagram calculation); and returning the residual potassium sulfate conversion mother liquor to the potassium-sulfur mixed salt concentrate conversion stage for recycling. And washing and drying the coarse potassium sulfate to obtain a potassium sulfate product.