Method for efficiently recovering lithium resource from magnesium sulfate subtype salt lake

Abstract

The invention discloses a method for efficiently recovering lithium resources from a magnesium sulfate subtype salt lake, and belongs to the technical field of salt lake lithium resource recovery. The method comprises the following steps: performing sodium removal and potassium removal on original brine of a salt lake, and sequentially performing concentration gradient enrichment in a plurality of enrichment salt pans to obtain old brine; ditching and halogen control are carried out on the enriched salt field after concentration gradient enrichment; the brine obtained after brine control is guided into an enrichment salt pan with the corresponding enrichment concentration to continue concentration gradient enrichment. The method provided by the invention has the advantages of high comprehensive recovery rate of lithium and maximum utilization of the salt pan, can effectively reduce the yield loss of lithium in the whole salt pan system, can realize recycling of lithium extraction waste water, and has the characteristics of resource conservation and ecological environment friendliness.

Description

Technical Field

[0001] The invention relates to the technical field of lithium resource recovery in salt lakes, and in particular to a method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes. Background Art

[0002] Magnesium sulfate subtype salt lake is a common type of salt lake. Most magnesium sulfate subtype salt lakes use the characteristics of brine and the phase diagram as a guide to carry out salt pan drying to remove sodium, potassium and magnesium to achieve the purpose of enriching boron and lithium. Taking Xitaijinaier Lake as a typical magnesium sulfate subtype salt lake as an example, after the lithium concentration of brine is separated from sodium and potassium from 250-300mg / L, it is enriched to about 1g / L, and then enriched to a higher concentration. As evaporation continues, the lithium concentration continues to increase. After the magnesium ions reach saturation, they are precipitated at the bottom of the salt pan in the form of magnesium chloride hexahydrate (MgCl2·6H2O), forming a large amount of hydrochlorobenzene (MgCl2·6H2O) minerals. In terms of enrichment, if a salt pan is used to directly enrich the lithium concentration to the corresponding point, it takes a lot of time and the efficiency is low, so a highly efficient way of enriching and recovering lithium resources in salt pans is needed.

[0003] The lithium in the brine exists in the form of ions in the solution. The continuous generation of hydrochlorite solids will entrain a large amount of lithium between the solid crystals, and the amount will continue to increase with the increase of hydrochlorite. As a result, the recovery rate of lithium in the salt field stage will decrease, resulting in a large loss of lithium resources, which greatly affects the production capacity and output of lithium carbonate in the brine. The continuous increase of hydrochlorite in the salt field system can be alleviated by raising the dam body, so that lithium can continue to be enriched to meet the standards. However, the continuous raising of the salt field dam body may cause ecological damage by taking a large amount of soil, and on the other hand, it still fails to solve the problem of lithium resource yield loss. Therefore, the use of efficient enrichment methods and the collection of lithium entrained between crystals from hydrochlorite have been raised to a very important development level, involving a new level of comprehensive utilization of salt lake resources. The problem of how to collect lithium to improve lithium recovery needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, so as to solve the problems of low efficiency in the brine enrichment process and loss of lithium resource recovery rate caused by intercrystalline entrainment of bischofite in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The technical solution of the present invention is a method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, comprising the following steps: after the original brine of the salt lake is de-sodiumized and de-potassiumized, it is sequentially enriched by concentration gradient in multiple enriched salt fields to obtain old brine;

[0007] Digging ditches and controlling brine in the salt pans after concentration gradient enrichment;

[0008] The brine obtained by brine control is introduced into the enrichment salt field with corresponding enrichment concentration to continue concentration gradient enrichment.

[0009] The method of the present invention uses a concentration gradient enrichment method to enrich the brine. Compared with directly enriching the brine to a set lithium concentration by natural evaporation in a salt pan, the concentration gradient enrichment method of the present invention can evaporate the brine by a dilution method, which can save a lot of time and improve the effect of lithium recovery. In addition, the magnesium sulfate subtype salt lake has a high magnesium-lithium ratio. During the enrichment process, a large amount of bischofite will be generated and deposited at the bottom of the salt pan with evaporation and concentration. The bischofite contains about 10-20% of the total volume of the ore layer. Free brine will cause a large amount of lithium resources to be wasted in the salt pan stage, which is not conducive to the comprehensive development and utilization of salt lake resources. After the concentration gradient enrichment, the present invention ditches and controls the brine in the salt pan used for enrichment, which can control most of the free brine entrained between the bischofite crystals, and carry out concentration gradient enrichment to achieve recovery. The method of the present invention effectively improves the efficiency of brine enrichment and the recovery rate of lithium resources.

[0010] Furthermore, the lithium concentration of the brine obtained after de-sodiumization and de-potassiumization is 0.8-1.1 g / L.

[0011] Furthermore, the lithium concentration of the old brine is 4.5 g / L. The old brine is transported to an impermeable storage tank for continuous use in lithium carbonate production.

[0012] Furthermore, the sequentially performing concentration gradient enrichment in multiple enriched salt pans includes: sequentially enriching the brine obtained after desodiumization and depotassiumization in five enriched salt pans to lithium concentrations of 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.8 g / L, and 4.5 g / L.

[0013] Furthermore, the enrichment adopts the dilution method, specifically, the height of the liquid level from the bischofite layer generated during the enrichment process (the bischofite generated during the enrichment process with evaporation and concentration is precipitated at the bottom of the salt pan to form the bischofite layer) is 15-30 cm. The liquid level height and the white bischofite reflective layer work together to achieve the best evaporation enrichment efficiency.

[0014] Furthermore, the method further includes the steps of dissolving and / or cleaning the enriched salt pan after brine control, specifically including: dissolving one or more of the enriched salt pans with enrichment concentrations of 2.0 g / L, 2.5 g / L, 3.8 g / L and 4.5 g / L, and / or cleaning the enriched salt pan with an enrichment concentration of 1.5 g / L;

[0015] Among them, the brine obtained from ore dissolution is introduced into the enriched salt pan with corresponding enrichment concentration to continue concentration gradient enrichment, and the enriched salt pan after ore dissolution and / or ore cleaning is continued to be used for concentration gradient enrichment of brine (forming a salt pan lithium resource recovery and circulation system).

[0016] Brine control cannot completely recover the lithium entrained between the crystals of bischofite. After the free brine is controlled by trenching, the bischofite still contains some lithium resources. After the brine is controlled, the bischofite is subjected to ore dissolution treatment, and the brine obtained after the ore dissolution is further subjected to concentration gradient enrichment, so as to realize the comprehensive and efficient recovery of the free brine entrained between the crystals of bischofite.

[0017] Further, the dissolving of one or more of the enriched salt pans with enrichment concentrations of 2.0g / L, 2.5g / L, 3.8g / L and 4.5g / L, and / or the clearing of the enriched salt pan with an enrichment concentration of 1.5g / L specifically refers to: digging ditches and controlling brine for one or more of the enriched salt pans with enrichment concentrations of 2.0g / L, 2.5g / L, 3.8g / L and 4.5g / L after concentration gradient enrichment, and dissolving the ore after brine control, and / or, digging ditches and controlling brine for the enriched salt pans with an enrichment concentration of 1.5g / L after concentration gradient enrichment, and clearing the ore after brine control.

[0018] Furthermore, the ore dissolving comprises: firstly adding low lithium concentration brine to the height of the bischofite ore layer in the enriched salt pan to replace the free intercrystalline brine in the bischofite ore layer, and then repeatedly adding ore dissolving water to the height of the bischofite ore layer to dissolve the ore until the magnesium concentration is 70-80 g / L;

[0019] The brine displaced by adding low lithium concentration brine and the brine obtained by adding molten ore each time are introduced into the enrichment salt field with corresponding enrichment concentration to continue gradient enrichment.

[0020] Furthermore, the low-lithium-concentration brine specifically refers to brine with a lithium concentration two levels lower than the enrichment concentration of the ditched enriched salt pan. For example, the enrichment concentration of the ditched enriched salt pan is 4.5g / L, and the lithium concentration of the low-lithium-concentration brine used is 2.5g / L; the enrichment concentration of the ditched enriched salt pan is 3.8g / L, and the lithium concentration of the low-lithium-concentration brine used is 2.0g / L; the enrichment concentration of the ditched enriched salt pan is 2.5g / L, and the lithium concentration of the low-lithium-concentration brine used is 1.5g / L; the enrichment concentration of the ditched enriched salt pan is 2.0g / L, and the lithium concentration of the low-lithium-concentration brine used is 0.8-1.1g / L (brine obtained after de-sodium and de-potassium).

[0021] Furthermore, the total amount of the molten mineral water added is 1-1.2 times the volume of the bischofite ore layer.

[0022] Furthermore, the molten mineral water is secondary nanofiltration water discharged from a lithium extraction membrane separation method from a salt lake, and the magnesium concentration of the secondary nanofiltration water is 16-20 g / L.

[0023] Furthermore, the ore cleaning specifically involves digging out and discarding the bischofite ore layer after brine control.

[0024] In the entire concentration gradient enrichment system, the original brine is de-sodiumized and de-potassiumized in the salt field to enrich the old brine for production and generate bischofite. The bischofite ore layer is dissolved by secondary nanofiltration water containing magnesium and then returned to the enriched salt field for concentration gradient enrichment. As the brine containing a large amount of magnesium is continuously transported to the salt field enrichment system, magnesium will become more and more in the entire salt field enrichment system, gradually producing adverse effects. Relative to enriched salt fields with other enrichment concentrations, the present invention digs out and discards the bischofite produced by the enriched salt field with an enrichment concentration of 1.5g / L after ditching and controlling the brine, and cleans out the salt field enrichment system. The cleaned bischofite has a low lithium content and a low ore dissolving value. Compared with the adverse effects caused by more and more bischofite, the adverse effects of cleaning the low-lithium bischofite causing waste of lithium resources are much lower than the former.

[0025] Further, the trenching comprises:

[0026] A fore pond was excavated in one corner of the enriched salt pan;

[0027] Find out the thickness of the bischofite layer in different directions;

[0028] With reference to the thickness of the bischofite ore layer, the main trench is first opened along the four sides of the enriched salt field, and then the main trench is opened in the middle along the east-west direction and / or the north-south direction, or the main trench is opened along the diagonal direction to divide the enriched salt field equally; then the secondary trench is opened in the area divided by the main trench.

[0029] Furthermore, the depths of the main ditch and the auxiliary ditch are 30-50 cm less than the thickness of the bischofite ore layer (i.e. 30-50 cm away from the silt, in order to ensure a higher cleanliness of the brine and reduce brine leakage); the width of the main ditch is 6 m, and the width of the auxiliary ditch is 4 m; the spacing between the auxiliary ditches is 6 m.

[0030] Furthermore, the depth of the fore pond is dug to the bottom silt, the area of ​​the fore pond is 15m×15m, and a pump is provided in the fore pond for collecting and transporting brine.

[0031] Furthermore, the exploration pit is dug to the bottom silt.

[0032] Furthermore, the specific operation of finding out the thickness of the hydrochlorite ore layer in different directions is: digging exploration pits at intervals of 15-20m in the horizontal and vertical directions (north and east, or south and west) of the enriched salt field to find out the thickness of the hydrochlorite ore layer in different directions.

[0033] Furthermore, the method of opening a secondary groove in the area evenly divided by the main groove includes: opening the secondary groove on the principle of even division or regularity to form a secondary groove in the shape of a "well", a "chuan" fence or a "three" fence, so as to fully control the free brine entrained between crystals.

[0034] Furthermore, the main ditch is opened around the enriched salt pan, including: the distance between the main ditch and the dam body is not less than 15m, and the excavated bischofite ore layer is protected to the slope of the dam body.

[0035] Furthermore, the equal division principle is applicable to the situation where the main ditch is first opened along the four sides of the enriched salt field, and then the main ditch is opened in the middle of the east-west direction and the north-south direction to divide the enriched salt field into four equal parts. Specifically, a secondary ditch is opened in the middle of the east-west direction and the north-south direction in the four equal parts divided by the main ditch, and the area divided by the main ditch is further divided into four equal parts. Then, secondary ditches are continued to be opened in the middle of the east-west direction and the north-south direction in one-fourth of the equal parts to divide it into four equal parts. The above process is repeated until the trenching of the entire enriched salt field is completed.

[0036] Furthermore, the rule principle specifically refers to opening auxiliary grooves in sequence at equal intervals in the opposite direction of the front pool, and it can only be done in one direction.

[0037] Furthermore, each main ditch and each auxiliary ditch are excavated in the opposite direction of the forebay and can only be excavated in one direction.

[0038] Furthermore, after the brine in the enriched salt pan is introduced into the enriched salt pan of the next enrichment concentration, trenching, brine control and ore dissolution, or trenching, brine control and ore cleaning can be started on the enriched salt pan.

[0039] The present invention discloses the following technical effects:

[0040] The present invention provides a method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes. The method adopts concentration gradient enrichment, ditching to control brine, ore dissolution, brine reuse after ore dissolution and other methods to efficiently recover lithium resources. The method has the advantages of high comprehensive lithium recovery rate and maximum salt field utilization, can effectively reduce the yield loss of lithium in the entire salt field system, can realize the recovery and utilization of lithium extraction waste water, and has the characteristics of resource conservation and ecological environment friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a schematic diagram of the operation process of efficiently recovering lithium resources from magnesium sulfate subtype salt lakes of the present invention;

[0043] Figure 2 This is a schematic diagram of a scheme for digging trenches for enriching salt pans in Example 1 of the present invention;

[0044] Figure 3 This is a schematic diagram of a scheme for digging trenches for enriching salt pans in Example 2 of the present invention;

[0045] Figure 4 This is a schematic diagram of the scheme for digging trenches for enriching salt fields in Example 3 of the present invention. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] As one aspect of the present invention, the present invention provides a method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, comprising the following steps (schematic diagram as shown in FIG. Figure 1 shown):

[0052] After the original brine of the salt lake is de-sodiumized and de-potassiumized, it is successively enriched by concentration gradient in multiple enriched salt fields to obtain old brine;

[0053] Digging ditches and controlling brine in the salt pans after concentration gradient enrichment;

[0054] The brine obtained by brine control is introduced into the enrichment salt field with corresponding enrichment concentration to continue concentration gradient enrichment.

[0055] As a preferred embodiment of the present invention, the sequential concentration gradient enrichment in multiple enriched salt pans includes: sequentially enriching the brine obtained after desodium and depotassium to lithium concentrations of 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.8 g / L, and 4.5 g / L in 5 enriched salt pans.

[0056] As a preferred embodiment of the present invention, the method further includes dissolving and / or cleaning the enriched salt pan after brine control, specifically comprising: dissolving one or more of the enriched salt pans with enrichment concentrations of 2.0 g / L, 2.5 g / L, 3.8 g / L and 4.5 g / L, and / or cleaning the enriched salt pan with an enrichment concentration of 1.5 g / L;

[0057] Among them, the brine obtained from ore dissolution is introduced into the enrichment salt pan with corresponding enrichment concentration to continue concentration gradient enrichment, and the enrichment salt pan after ore dissolution and / or ore cleaning is completed is continuously used for concentration gradient enrichment of brine.

[0058] As a preferred embodiment of the present invention, the method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes comprises the following specific steps:

[0059] Step 1: The raw brine from the salt lake is pre-treated in a salt pan to remove sodium and potassium to obtain brine with a lithium concentration of 0.8-1.1 g / L, which is then introduced into an enrichment salt pan for preliminary enrichment, and the bischofite generated by evaporation and concentration is precipitated at the bottom of the enrichment salt pan for retention;

[0060] Step 2: After the brine is enriched to a certain lithium concentration, it is transferred to the next enriched salt pan with a higher lithium concentration for concentration gradient enrichment. Finally, the old brine reaching a certain concentration is transported to the impermeable storage tank for continuous use in lithium carbonate production. During the enrichment process, the bischofite generated by evaporation and concentration is precipitated at the bottom of each enriched salt pan and retained. The concentration gradient enrichment specifically refers to the concentration gradient enrichment of lithium concentration from low to high in the form of lithium concentration of 1.0-1.5-2.0-2.5-3.8-4.5 g / L.

[0061] Step 3, after the enrichment is completed, the enriched salt pan with a large amount of bischofite is ditched in a specific manner (one or more of the enriched salt pans are ditched), and the free brine entrained between the crystals is controlled and transferred to the enriched salt pan of the corresponding enrichment concentration to continue concentration gradient enrichment, or first introduced into the anti-seepage storage tank, and then introduced into the enriched salt pan of the corresponding enrichment concentration for concentration gradient enrichment in the next stage of concentration gradient enrichment;

[0062] Step 4, dissolving ore (dissolving bischofite) in one or more of the enriched salt pans with enrichment concentrations of 2.0 g / L, 2.5 g / L, 3.8 g / L and 4.5 g / L after brine control in a batch-by-step and concentration-controlled manner, transferring the brine reaching the corresponding lithium concentration range to the enriched salt pans with the corresponding enrichment concentrations to continue concentration gradient enrichment or first introduce into an impermeable storage tank; or clearing the ore of the enriched salt pan with an enrichment concentration of 1.5 g / L after brine control (digging out the bischofite ore layer and discarding it);

[0063] Step 5: After the bischofite dissolution procedure is completed, or after the bischofite ore cleaning is completed, the salt pan is used as an enrichment salt pan for the next stage of brine concentration gradient enrichment, and continues to be used for brine concentration gradient enrichment, thereby forming a salt pan lithium resource recovery system.

[0064] As a preferred embodiment of the present invention, the enrichment process is carried out by rapid evaporation concentration by dilution method, and the specific dilution method is that the height of the liquid surface from the bischofite is 15-30 cm. The liquid level height and the white bischofite reflective layer work together to achieve the best evaporation enrichment efficiency.

[0065] As a preferred embodiment of the present invention, the batch-by-step and concentration control described in step 4 is specifically that only the first dissolution of the bischofite ore is added with low lithium concentration brine to replace the free intercrystalline brine that is difficult to collect at the bottom, and the second and subsequent dissolutions are carried out using ore dissolving water, and the salt pan is added with ore dissolving water to the height of the bischofite ore layer. After the magnesium concentration in the solution reaches 70-80 g / L, the dissolved lithium-containing ore dissolving brine is transferred to the enriched salt pan with the corresponding enrichment concentration for further enrichment, and the ore dissolution is carried out step by step for multiple times until the amount of water added is 1-1.2 times the total calculated volume of the bischofite, and then the dissolution of the bischofite ore is stopped.

[0066] As a preferred embodiment of the present invention, the ore dissolving water is secondary nanofiltration water discharged from a lithium extraction membrane separation method from a salt lake, and its magnesium concentration is 16-20 g / L.

[0067] As a preferred embodiment of the present invention, the trenching comprises:

[0068] A fore pond was excavated in one corner of the enriched salt pan;

[0069] Find out the thickness of the bischofite layer in different directions;

[0070] With reference to the thickness of the bischofite ore layer, the main trench is first opened around the enriched salt field, and then the main trench is opened in the middle of the east-west direction and / or the north-south direction or along the diagonal direction to divide the enriched salt field equally; then the secondary trench is opened in the area divided by the main trench.

[0071] As a preferred embodiment of the present invention, the ditching more specifically comprises the following steps:

[0072] S1. Before the salt pan is dug, a fore pond is set up, which is dug to the bottom mud and has an area of ​​15m×15m, which is conducive to the collection of brine after excavation and the transportation of brine by pump group pipeline;

[0073] S2. Exploration pits are dug at intervals of 15-20m on the north and east (or south and west) sides of the salt pan, and the next interval exploration pit is dug to the bottom mud to find out the thickness of the hydrochlorite ore layer in different directions;

[0074] S3. First, dig the main ditch around the salt pan (excavate 30-50cm higher than the silt), then dig the main ditch in the middle along the east-west direction and / or north-south direction, or dig the main ditch in the diagonal direction to divide the salt pan equally;

[0075] S4. Open auxiliary trenches in the area divided by the main trench on the principle of equal or regular division to form auxiliary trenches in the shape of a "well", a "chuan" fence or a "three" fence, so as to fully control the free brine entrained between crystals.

[0076] As a preferred embodiment of the present invention, the depths of the main trench and the auxiliary trench are 30-50 cm less than the thickness of the bischofite ore layer; the width of the main trench is 6 m, the width of the auxiliary trench is 4 m; and the spacing between the auxiliary trenches is 6 m.

[0077] As a preferred embodiment of the present invention, the main ditch is opened around the enriched salt field, including: the distance between the main ditch and the dam body is not less than 15m, and the excavated bischofite ore layer is protected to the slope of the dam body.

[0078] As a preferred embodiment of the present invention, the equal division principle is applicable to the situation where the main trench is first opened along the four sides of the enriched salt field, and then the main trench is opened in the middle of the east-west direction and the north-south direction to divide the enriched salt field into four equal parts. Specifically, a secondary trench is opened in the middle of the east-west direction and the north-south direction in the four equal parts divided by the main trench, and the area divided by the main trench is further divided into four equal parts. Then, secondary trenches are continued to be opened in the middle of the east-west direction and the north-south direction in one-fourth of the equal parts to divide it into four equal parts. The above process is repeated until the trenching of the entire enriched salt field is completed.

[0079] As a preferred embodiment of the present invention, the rule principle specifically refers to opening auxiliary grooves in sequence at equal intervals in the opposite direction of the front pool, and it can only be done in one direction.

[0080] As a preferred embodiment of the present invention, each main ditch and each auxiliary ditch are excavated in the opposite direction of the forebay and can only be excavated in one direction.

[0081] Because there is a pumping station in the front pool, the brine controlled by ditching in the opposite direction of the front pool can flow along the ditch direction to the pumping station and be pumped away in time. If the direction is wrong, the brine cannot be pumped away in time, which will affect the subsequent ditching.

[0082] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0083] The following examples were carried out using Xitaijinaier Lake as the experimental salt lake.

[0084] Example 1

[0085] A method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, comprising the following steps:

[0086] Step 1: De-sodium and de-potassiumize the salt lake brine in the pre-treated salt pan by spreading and drying the salt pan, and obtain 3.8893 million m3 of de-sodium and de-potassiumized brine with an average lithium concentration of 1.06 g / L. 3 ;

[0087] Step 2: The brine after de-sodiumization and de-potassiumization is introduced into the primary enrichment salt pan for preliminary enrichment. After enrichment to a lithium concentration of 1.5 g / L, all the brine is transferred to the secondary enrichment salt pan for enrichment with a higher lithium concentration. After enrichment to a lithium concentration of 2.0 g / L, all the brine is transferred to the tertiary enrichment salt pan for enrichment with a higher lithium concentration. After enrichment to a lithium concentration of 2.5 g / L, all the brine is transferred to the fourth enrichment salt pan for enrichment with a higher lithium concentration. After enrichment to a lithium concentration of 3.8 g / L, all the brine is transferred to the fifth enrichment salt pan for enrichment with a higher lithium concentration. After enrichment to a lithium concentration of 4.5 g / L, the gradient enrichment of the brine is completed to obtain old brine. 641,300 m of old brine enriched to a lithium concentration of 4.5 g / L in the fifth enrichment salt pan is collected. 3 Transport to the impermeable storage tank for continuous use in lithium carbonate production;

[0088] The dilution method is used in the enrichment process for rapid evaporation and concentration. The bischofite generated by evaporation and concentration is precipitated at the bottom of the salt pan to form a bischofite ore layer. When diluting, the height of the liquid surface from the bischofite ore layer is 30 cm.

[0089] Step 3: After the old brine obtained from the five-level enrichment salt pan is transferred to the anti-seepage storage tank, the five-level enrichment salt pan (enrichment concentration is 4.5g / L, area is 112,500 m 2 )according to Figure 2 The free brine carried between the crystals of the chlormagnesite ore layer was digged in a controlled manner and transferred to the corresponding enriched salt pan for gradient enrichment. The free brine carried between the crystals was measured to be 37,100 m 3, the concentration of lithium ions in the free brine is 4.37 g / L, accounting for 20.45% of the total volume of the hydrochlorobenzene ore layer;

[0090] Step 4, ore dissolution: First, introduce low lithium concentration brine with a lithium concentration of 2.5g / L into the fifth-level enriched salt field after ditching and brine control. The amount added is equal to the height of the hydrochlorite ore layer (a total of 73,200 m 3 ), displacing the free intercrystalline high-lithium brine that is difficult to collect at the bottom of the hydrochlorite ore layer, and the amount of brine displaced is 73,500 m 3 , the lithium concentration is 3.44g / L, and it is introduced into the fourth-level enrichment salt pan for gradient enrichment; then, the second-level nanofiltration water is added to the fifth-level enrichment salt pan after the trench is opened to dissolve the ore, and the water addition depth is the height of the hydrochlorite ore layer. After the magnesium concentration of the dissolved ore brine reaches 80g / L, the dissolved ore brine is exported to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment (if the lithium concentration of the dissolved ore brine is less than 1.5g / L, it is introduced into the first-level enrichment salt pan, if the lithium concentration of the dissolved ore brine is ≥1.5g / L and less than 2g / L, it is introduced into the second-level enrichment salt pan, if the lithium concentration of the dissolved ore brine is ≥2g / L and less than 2.5g / L, it is introduced into the third-level enrichment salt pan, and this rule is followed). After adding the second-level nanofiltration water to dissolve the ore, it is transferred to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment, and the total amount of the second-level nanofiltration water added is recorded until the total amount of the second-level nanofiltration water added and the volume of the hydrochlorite ore layer (181,400 m 3 ) were the same, and then the ore dissolution was stopped. The average lithium concentration of the brine obtained after adding the secondary nanofiltration water to dissolve the ore was 2.16 g / L, and the total amount was consistent with the total amount of the secondary nanofiltration water added;

[0091] Step 5: After the ore dissolution operation is completed, the enriched salt pan continues to be used as the enriched salt pan for the next stage of brine gradient enrichment and continues to be used for the gradient enrichment of brine.

[0092] Among them, according to Figure 2 The specific steps for digging ditches are as follows:

[0093] S1, at 112,500m 2 A fore pond was dug in the northeast corner of the salt pan, with a depth of 15m×15m to the silt, and two 90KW high-power pumps were installed to transport brine;

[0094] S2. The exploration pits were dug 15m away from the dam body on the north and east sides of the salt pan, with an interval of 20m. The next interval exploration pit was dug to the bottom mud. It was found that the actual thickness of the chlorite layer in the salt pan was 1.61m. The trench was raised by 31cm and the actual trench depth was 1.30m to ensure that the brine did not adhere to the mud and reduce the cleanliness and brine leakage;

[0095] S3. First, dig a main ditch 6m (width) 15m away from the dam body slope along the east and north sides, then dig a main ditch 6m (width) 15m away from the dam body slope along the south and west sides, and then dig a main ditch 6m (width) in the middle of the east-west and north-south directions to divide the salt pan into four equal parts. The excavated bischofite ore layer is protected to the dam body slope to protect the dam body; each main ditch is excavated in the opposite direction of the fore pond;

[0096] S4. Dig a 4m secondary ditch in the middle of the east-west and north-south directions to further divide the area divided by the main ditch into four equal parts. Then, continue to dig a 4m secondary ditch in the middle of the east-west and north-south directions in one fourth of the equal parts and divide it into four equal parts again. Repeat the above process until the trenching of the entire salt field is completed. The spacing between the secondary ditches is 6m, and a "well"-shaped secondary ditch is obtained; each secondary ditch is excavated in the opposite direction of the front pool.

[0097] From the data of this example, it can be seen that the lithium recovery rate achieved by only performing the concentration gradient enrichment to step 2 is: (4.5g / L×641,300m 3 ) / (1.06g / L×3889300m 3 )×100%=70.0%;

[0098] The total lithium recovery rate achieved after ditching, brine control and ore dissolution is: (4.5g / L×641,300m 3 +4.37g / L×37100m 3 +3.44g / L×73,500m 3 +2.16g / L×181,400m 3 -2.5g / L×73,200m 3 ) / (1.06g / L×3889300m 3 )×100%=85.13%, which effectively improves the lithium recovery rate.

[0099] Example 2

[0100] A method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, comprising the following steps:

[0101] Step 1 and step 2 are the same as in Example 1;

[0102] Step 3: After the brine in the fourth-level enrichment salt pan is transferred to the fifth-level enrichment salt pan, the fourth-level enrichment salt pan (enrichment concentration is 3.8g / L, area is 123,800 m 2 )according to Figure 3 The free brine carried by the intercrystalline of the chlormagnesite ore layer was digged in a controlled manner and transferred to the corresponding enriched salt field for gradient enrichment. The free brine carried by the intercrystalline was measured to be 41,500 m 3, the concentration of lithium ions in the free brine is 3.52 g / L, accounting for 17.64% of the total volume of the hydrochlorobenzene ore layer;

[0103] Step 4, ore dissolution: First, introduce low lithium concentration brine with a lithium concentration of 2.0g / L into the fourth-level enriched salt field after ditching and brine control. The amount added is equal to the height of the hydrochlorobisite ore layer (a total of 63,200 m 3 ), displacing the free intercrystalline high-lithium brine that is difficult to collect at the bottom of the hydrochlorite ore layer, and the amount of brine displaced is 64,400 m 3 , the lithium concentration is 2.61g / L, and it is introduced into the fourth-level enrichment salt pan for gradient enrichment (a new salt pan can be selected as the fourth-level salt pan, or the brine can be stored in an impermeable storage tank first, and then introduced into the fourth-level salt pan in the next round of brine gradient enrichment); then, secondary nanofiltration water is added to the fourth-level enrichment salt pan after ditching for ore dissolution, and the water addition depth is the height of the hydrochlorite ore layer. After the magnesium concentration of the dissolved brine reaches 80g / L, the dissolved brine is exported to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment, and the secondary nanofiltration water is continued to be added for ore dissolution and then transferred to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment. The total amount of secondary nanofiltration water added is recorded until the total amount of secondary nanofiltration water added and the volume of the hydrochlorite ore layer (235,200 m 3 ) were the same, and then the ore dissolution was stopped. The average lithium concentration of the brine obtained after adding the secondary nanofiltration water to dissolve the ore was 1.83 g / L, and the total amount was consistent with the total amount of the secondary nanofiltration water added;

[0104] Step 5: After the ore dissolution operation is completed, the enriched salt pan continues to be used as the enriched salt pan for the next stage of brine gradient enrichment and continues to be used for the gradient enrichment of brine.

[0105] Among them, according to Figure 3 The specific steps for digging ditches are as follows:

[0106] S1, at 123,800m 2 A fore pond was dug in the northwest corner of the salt pan, with a depth of 15m×15m to the silt, and two 90KW high-power pumps were installed to transport brine;

[0107] S2. Multiple exploration pits were dug 15m away from the dam on the north and west sides of the salt pan, with an interval of 15m. The pits were dug to the bottom mud and the actual thickness of the bischofite layer in the salt pan was found to be 1.90m. The trench was raised 50cm for excavation and the actual trench depth was 1.40m.

[0108] S3. First, dig the main ditch 6m away from the dam body slope 15m away along the north and west sides, then dig the main ditch 6m away from the dam body slope 15m away along the east and south sides, and then dig the main ditch 6m in a straight line from the northwest corner to the southeast corner; each main ditch is excavated in the opposite direction of the fore pond;

[0109] S4. Based on the main ditch from the northwest corner to the southeast corner, secondary ditches perpendicular to the main ditch are opened in the opposite direction of the front pool (from the northwest corner to the southeast corner) at intervals of 6m. The width of the secondary ditch is 4m.

[0110] From the data of this example, it can be seen that the lithium recovery rate achieved by the concentration gradient enrichment in step 2 is: (4.5g / L×641,300m 3 ) / (1.06g / L×3889300m 3 )×100%=70.0%;

[0111] The total lithium recovery rate achieved after ditching, brine control and ore dissolution is: (4.5g / L×641,300m 3 +3.52g / L×41,500m 3 +2.61g / L×64,400m 3 +1.83g / L×235,300m 3 -2g / L×63,200m 3 ) / (1.06g / L×3889300m 3 )×100%=85.0%, which effectively improves the lithium recovery rate.

[0112] Example 3

[0113] A method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, comprising the following steps:

[0114] Step 1 and step 2 are the same as in Example 1;

[0115] Step 3: After the brine in the third-level enrichment salt pan is transferred to the fourth-level enrichment salt pan, the third-level enrichment salt pan (enrichment concentration is 2.5g / L, area is 111,300 m 2 )according to Figure 4 The free brine carried between the crystals of the chlormagnesite ore layer was digged in a controlled manner and transferred to the corresponding enriched salt pan for gradient enrichment. The free brine carried between the crystals was measured to be 29,600 m 3 , the concentration of lithium ions in the free brine is 2.26 g / L, accounting for 14.83% of the total volume of the hydrochlorobenzene ore layer;

[0116] Step 4, ore dissolution: First, introduce low lithium concentration brine with a lithium concentration of 1.5g / L into the third-level enriched salt field after ditching and brine control. The amount added is equal to the height of the hydrochlorite ore layer (a total of 52,600 m 3 ), displacing the free intercrystalline high-lithium brine that is difficult to collect at the bottom of the hydrochlorite ore layer, and the amount of brine displaced is 52,900 m 3, the lithium concentration was 1.82 g / L, and it was introduced into the secondary enrichment salt pan for gradient enrichment. Then, the secondary nanofiltration water was added to the tertiary enrichment salt pan after the trench was opened to dissolve the ore. The water adding depth was the height of the hydrochlorite ore layer. After the magnesium concentration of the dissolved ore brine reached 80 g / L, the dissolved ore brine was led out to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment. After adding the secondary nanofiltration water to dissolve the ore, it was transferred to the corresponding enrichment salt pan for gradient enrichment to continue gradient enrichment. The total amount of the secondary nanofiltration water added was recorded until the total amount of the secondary nanofiltration water added and the volume of the hydrochlorite ore layer (200,300 m 3 ) were the same, and then the ore dissolution was stopped. The average lithium concentration of the brine obtained after adding the secondary nanofiltration water to dissolve the ore was 0.86 g / L, and the total amount was consistent with the total amount of the secondary nanofiltration water added;

[0117] Step 5: After the ore dissolution operation is completed, the enriched salt pan continues to be used as the enriched salt pan for the next stage of brine gradient enrichment and continues to be used for the gradient enrichment of brine.

[0118] Among them, according to Figure 4 The specific steps for digging ditches are as follows:

[0119] S1, at 220,000 m 2 A fore pond was dug in the northeast corner of the salt pan, with a depth of 15m×15m to the silt, and two 90KW high-power pumps were installed to transport brine;

[0120] S2. Multiple exploration pits were dug 15m away from the dam on the north and east sides of the salt pan, with an interval of 20m. The pits were dug to the bottom mud and the actual depth of the bischofite layer in the salt pan was found to be 1.80m. The trench was raised 40cm and the actual trench depth was 1.40m.

[0121] S3, first dig the main ditch 6m away from the dam body slope 15m away along the north and east sides, then dig the main ditch 6m away from the dam body slope 15m away along the west and south sides, and then dig the main ditch 6m in the middle of the north-south direction; when digging each main ditch, proceed in the opposite direction of the fore pond;

[0122] S4. Dig auxiliary ditches in the opposite direction of the front pool (from north to south) at intervals of 6m. The width of the auxiliary ditch is 4m. Each auxiliary ditch is dug from east to west to form a "three" fence-shaped auxiliary ditch.

[0123] From the data of this example, it can be seen that the lithium recovery rate achieved by the concentration gradient enrichment in step 2 is: (4.5g / L×641,300m 3 ) / (1.06g / L×3889300m 3 )×100%=70.0%;

[0124] The total lithium recovery rate achieved after ditching, brine control and ore dissolution is: (4.5g / L×641,300m3 +2.26g / L×29,600m 3 +1.82g / L×52900m 3 +0.86g / L×200,300m 3 -1.5g / L×52600m 3 ) / (1.06g / L×3889300m 3 )×100%=76.22%, which effectively improves the lithium recovery rate.

[0125] In Example 1 to Example 3, the enrichment concentration of the trenched salt pan decreases successively, and the number of trenched meters of the relative area using the corresponding trenching method also decreases. The higher the lithium concentration of the enriched salt pan, the more lithium resources are entrained between the bischofite crystals, and the higher the recovery value. Therefore, the present invention adopts trenching methods of different complexities according to the different lithium enrichment concentrations of the salt pan to achieve efficient brine control and ore dissolution, which fully reflects the matching of efficiency and economy.

[0126] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes, characterized in that: The following steps are involved: After the original brine of the salt lake is de-sodiumized and de-potassiumized, it is successively enriched by concentration gradient in multiple enriched salt fields to obtain old brine; Digging ditches and controlling brine in the salt pans after concentration gradient enrichment; The brine obtained by brine control is introduced into the enrichment salt field with corresponding enrichment concentration to continue concentration gradient enrichment.

2. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 1, characterized in that: The lithium concentration of the brine obtained after de-sodiumization and de-potassiumization is 0.8-1.1 g / L.

3. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 2, characterized in that: The sequentially performing concentration gradient enrichment in multiple enriched salt pans includes: sequentially enriching the brine obtained after de-sodium and de-potassium in five enriched salt pans to lithium concentrations of 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.8 g / L, and 4.5 g / L.

4. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 3, characterized in that: The enrichment is carried out by dilution method, specifically, the height of the liquid surface from the bischofite ore layer produced in the enrichment process during dilution is 15-30 cm.

5. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 3, characterized in that: The method further includes dissolving and / or cleaning the enriched salt pan after brine control, specifically comprising: dissolving one or more of the enriched salt pans with enrichment concentrations of 2.0 g / L, 2.5 g / L, 3.8 g / L and 4.5 g / L, and / or cleaning the enriched salt pan with an enrichment concentration of 1.5 g / L; Among them, the brine obtained from ore dissolution is introduced into the enrichment salt pan with corresponding enrichment concentration to continue concentration gradient enrichment, and the enrichment salt pan after ore dissolution and / or ore cleaning is completed is continuously used for concentration gradient enrichment of brine.

6. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 5, characterized in that: The ore dissolving comprises: firstly adding low lithium concentration brine to the height of the bischofite ore layer in the enriched salt field to replace the free intercrystalline brine in the bischofite ore layer, and then repeatedly adding ore dissolving water to the height of the bischofite ore layer to dissolve the ore until the magnesium concentration is 70-80 g / L; The brine displaced by adding low lithium concentration brine and the brine obtained by adding molten ore each time are introduced into the enrichment salt field with corresponding enrichment concentration to continue gradient enrichment.

7. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 5, characterized in that: The total amount of the molten mineral water added is 1-1.2 times the volume of the bischofite ore layer.

8. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes as claimed in claim 5, characterized in that: The ore dissolving water is secondary nanofiltration water discharged from a lithium extraction membrane separation method in a salt lake, and the magnesium concentration of the secondary nanofiltration water is 16-20 g / L.

9. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes according to claim 1, characterized in that: The trenching comprises: A fore pond was excavated in one corner of the enriched salt pan; Find out the thickness of the bischofite layer in different directions; With reference to the thickness of the bischofite ore layer, the main trench is first opened around the enriched salt field, and then the main trench is opened in the middle of the east-west direction and / or the north-south direction or along the diagonal direction to divide the enriched salt field equally; then the secondary trench is opened in the area divided by the main trench.

10. The method for efficiently recovering lithium resources from magnesium sulfate subtype salt lakes according to claim 9, characterized in that: The depths of the main trench and the auxiliary trench are 30-50 cm less than the thickness of the bischofite ore layer; the width of the main trench is 6 m, the width of the auxiliary trench is 4 m; and the spacing between the auxiliary trenches is 6 m.

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