Method for obtaining lithium sulfate monohydrate ore with low chlorine and magnesium impurity content
Through grinding and flotation treatment of potassium halide, combined with flotation technology of amine collector and foaming agent, the problems of low extraction efficiency of lithium sulfate and high impurity content in high sulfate salt water are solved, and high purity lithium sulfate is achieved The concentration of monohydrate improves the production efficiency and economicality of lithium.
Patent Information
- Application Number
- CN202280095686.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-02
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art is difficult to effectively and economically extract high-purity lithium sulfate from high sulfate brine, and there is a problem of high impurity content of chlorine and magnesium, which affects the production efficiency and economicality of lithium.
Potassium halide is treated through the two main stages of grinding and flotation, and lithium sulfate is released and concentrated. Flotation is performed using amine collectors and foaming agents. It is divided into two stages: crude selection and selection, combined with filtration and recycling treatment , gradually improve the purity and recovery rate of lithium sulfate, and reduce the impurity content.
The lithium sulfate monohydrate ore with low chlorine and magnesium impurity content was efficiently concentrated from high sulfate brine, which improved the production efficiency and economy of lithium and reached a lithium sulfate grade higher than 90%.
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Abstract
Description
[0001] Overview
[0002] The present patent application relates to a method for obtaining lithium sulfate monohydrate ore with low chlorine and magnesium impurity content. Specifically, the method comprises: concentrating lithium sulfate present in a stockpile of potassium carnallite (KCl*MgCl2*6H2O) with high content of lithium sulfate (Li2SO4*H2O) and sodium chloride (NaCl) through grinding, flotation, leaching and filtration stages. Prior art
[0003] For many years, high sulfate brines were only producers of potassium, with the lithium component being returned to the salt pans via reinjection. This meant that not all brine extracted produced lithium, even if it also contained this important ionic component. Currently, nearly all brine extracted from salt pans produces potassium.
[0004] Lithium production in a lithium field considers 2 deposits, one where the main anion is chloride and the other where there is a large amount of sulfate. This difference is very important because the production and / or refining process will change depending on the raw material.
[0005] In view of the above, the existing methods in the prior art are mainly focused on the production of lithium carbonate (Li2CO3) and a small amount of lithium hydroxide (LiOH·H2O) from the first deposit; this is based on chlorine and uses very little sulfate. However, to date, there is no technically and economically feasible alternative method for treating high-sulfate brines.
[0006] In the prior art, various information on obtaining lithium salts can be found. However, all of these information are significantly different from the method of the present invention.
[0007] Chinese patent publication CN102921553 (A) describes a method for flotation of lithium potassium sulfate in a sodium chloride mixture. The product of the flotation in this application is lithium sulfate, which is a mineral different from lithium potassium sulfate. In addition, in this application, the lithium sulfate is initially mixed with a variety of minerals other than sodium chloride, such as carnallite (hydrated potassium magnesium chloride), bischofite (hydrated magnesium chloride), and other contaminants present, making the method more complicated.
[0008] Chinese patent publication CN101318670 (A) describes a production method for extracting lithium chloride salt from a salt mixture containing lithium chloride salt and bischofite (hydrated magnesium chloride), the salt mixture being produced by evaporating brine in an evaporation pond. Although in both methods, the salt mixture before flotation is obtained by evaporating brine in an evaporation pond, the salt to be floated is different, because in the case of the present application, the salt is lithium sulfate, while the salt of patent CN101318670 is lithium chloride; and the salt present in the mixture is also different, because in the present application, in addition to bischofite, sodium chloride, carnallite (potassium chloride and hydrated magnesium chloride) and other contaminants are also present.
[0009] Chinese patent publication CN109174438 (A) describes a classification process for spodumene beneficiation, which belongs to the field of multi-metal beneficiation technology. Although spodumene flotation may be part of a process that produces lithium sulfate as an intermediate product, spodumene is a lithium aluminum silicate from a rock mixture rather than brine, which makes the raw material to be floated completely different from the raw material used in this application.
[0010] Therefore, it can be affirmed that the present invention solves a previously unsolved problem because it seeks to concentrate lithium sulfate monohydrate having low chlorine and magnesium impurity contents from brine which is not economical for the purpose of utilizing it for lithium production. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 : A schematic diagram of the overall concentration method of lithium sulfate monohydrate of the present invention is described.
[0012] DETAILED DESCRIPTION
[0013] A method for obtaining lithium sulfate monohydrate (Li2SO4·H2O) ore low in chlorine and magnesium impurities comprises two main stages: grinding and flotation.
[0014] The process consists of feeding potassium carnallite salts with a high SO4 concentration to a comminution stage, in particular a grinding stage. The purpose of this is to reduce the size of the potassium carnallite salts and to release the lithium sulfate present in the mineral. This material enters a rougher flotation stage, the purpose of which is to recover as much of the target material as possible, taking into account the recovery rate rather than the ore grade. The concentrate produced enters a concentrator flotation stage, the purpose of which is to increase the grade until the required purity is reached, in order to feed the subsequent stages. This selective stage favors the grade of the target mineral rather than the recovery rate. The tailings produced are recycled to the rougher flotation to recover the material that was not floated in the circuit. The rougher tailings produced enter a second recovery stage, which consists of a scavenger flotation, the purpose of which is to increase the total recovery of the flotation circuit, recovering the minerals that were not floated in the previous stage, obtaining a discharged tailing with a lithium sulfate grade of 0.2% Li. The concentrate obtained is characterized by a low grade, so it can be recycled to the rougher flotation.
[0015] The validated lithium sulfate feed ranges are: 4% to 30% lithium sulfate monohydrate, 50% to 70% potassium carnallite, 8% to 17% sodium chloride; in some cases, bischofite (MgCl2*6H2O) can range from 4% to 20%, with the remainder being mainly impurities related to boron (1% to 2%) and calcium (0.1% to 0.2%).
[0016] The grinding of the material is carried out in a folding crusher and a cage mill in order to release the lithium sulfate crystals present in the potassium carnallite matrix and prepare them for flotation. To avoid overstressing the mill, a pre-saturated equilibrium brine is added to the mill housing to remove solids that may be embedded therein.
[0017] After the grinding stage, the salt is contacted with a brine pre-saturated with the same salt to produce a slurry with a high solids percentage (40% to 50%), to which 50% of a flotation agent (amine collector) is added to prepare the material for the flotation stage, and then the slurry is pumped into the rougher flotation cell.
[0018] The recycled stream of the beneficiated tailings and the scavenged concentrate is fed to the rougher flotation cell; these streams have a low percentage of solids. As a result, a slurry of about 30% to 35% solids is produced as feed to the rougher flotation, with the remaining 30% being added to the cell with collectors and frothers.
[0019] The rougher flotation is run in a recycling mode to obtain a concentrate of more than 50% lithium sulfate monohydrate. The rougher flotation tailings have a low content of lithium sulfate monohydrate and are subjected to classification and regrinding stages in a cage crusher.
[0020] The classified regrind and undersize materials are pooled together and together with the remaining percentage of collectors and frothers become the feed to the scavenger flotation stage, the aim of which is to produce an industrial tailings with the lowest level of lithium sulphate with the cells operating in a recovery mode.
[0021] On the other hand, the obtained rough concentrate is sent to the beneficiation stage (beneficiation), where it must be concentrated to a lithium sulphate level of 85%, optionally using tanks to increase the height of the cushion. Given that this is a selective flotation, the tailings of this stage are recycled to the above-mentioned rougher flotation stage to avoid losses.
[0022] The concentrate is sent to the filtering stage where a stockpile with a high lithium sulfate content of <85% is obtained, where the stockpile is washed with hot water using spray heads, the purpose of which is to dissolve the chlorine related impurities and improve the grade of the product, thereby obtaining a grade greater than 90%.
[0023] Example
[0024] Industrial tests were conducted according to the method of obtaining lithium sulfate monohydrate by flotation, and the following results were obtained.
[0025] Table 1. Lithium sulfate content in primary fluid
[0026]
[0027] Table 2. Chemical composition of primary fluids
[0028] fluid K[％] Na[%] Mg[%] Ca[%] <![CDATA[SO4[%]]]> Li[%] Cl[％] <![CDATA[H3BO3[%]]]> margin[%] Feed 7.73 4.17 6.30 0.03 14.37 2.06 32.17 0.66 0.05 product 1.20 0.20 1.17 0.04 69.19 9.84 4.08 1.16 0.35
[0029] Additionally, tests were conducted at a laboratory scale using a 5-liter Denver flotation cell to validate and use a method for concentrating lithium sulfate by flotation.
[0030] The lithium sulfate feed range that has been verified on a laboratory scale is: 5% to 30% lithium sulfate monohydrate, 50% to 70% potassium carnallite, 8% to 17% sodium chloride; in some cases, bischofite (MgCl2*6H2O) ranges from 5% to 2%, and the rest is mainly impurities related to boron (1% to 2%) and calcium (0.1% to 0.2%). After grinding, the crushed material is evenly loaded according to the capacity of the tank.
[0031] It is emphasized that because the present application deals with salts, it is necessary to generate a brine that is saturated and in equilibrium with such salts to avoid undesirable dissolution and / or precipitation of the salts.
[0032] For the rougher flotation, a 50% solids slurry was formed and conditioned by shaking it in a flotation cell containing flotation agents (amine collector and frother) for 10 minutes. Once the treatment time was complete, the remaining brine was added to achieve the desired solids percentage for this stage. In this case, the process was run at 31% solids, air was released and parameters were adjusted as described above.
[0033] When the first drop of concentrate falls on the tray, the flotation time starts. For rougher flotation, this time is set to 7 minutes. The concentrate is padded every 15 seconds to reposition the brine to maintain the tank position by a peristaltic pump.
[0034] Once the flotation time is over, the air valve is closed and the shaking is stopped, the resulting stream is kneaded and filtered to obtain a solid product and tailings, which must be done to produce a new slurry to feed the concentrate flotation.
[0035] In the concentrate flotation, the same 5-liter tank is used and the process is repeated, adding collector and frother, and processing for 10 minutes at 50% solids. Once the processing is completed, the tank is filled again until 20% solids are fed and the air is released. As in the rougher flotation, the flotation time starts as soon as the first drop of concentrate drips over the tank wall. This flotation time is set to 10 minutes. The concentrate material is then filtered and processed for subsequent stages.
[0036] Given below are the main results obtained at the various stages constituting the process for obtaining lithium sulfate monohydrate on a laboratory scale.
[0037] Table 3. Lithium sulfate chemical composition of rougher feed and concentrator concentrate at laboratory scale
[0038] fluid K[％] Na[%] Mg[%] Ca[%] <![CDATA[SO4[%]]]> Li[%] Cl[％] <![CDATA[H3BO3[%]]]> Rough feed 9.00 4.64 6.13 0.01 14.01 2.08 34.56 0.14 Concentrate 0.73 1.44 1.36 0.04 66.81 9.54 6.82 3.43
[0039] Table 4. Lithium sulfate content of rougher feed and concentrator concentrate at laboratory scale
[0040]
Claims
1. A method for obtaining lithium sulfate monohydrate ore with low chlorine and magnesium impurity contents from uneconomical brine to utilize said brine for lithium production, characterized in that: Feeding potassium carnallite salt with a high concentration of SO4 to a comminution stage, in particular a grinding stage, to reduce the size of the potassium carnallite salt and release the lithium sulfate present in the ore; The ground material is subjected to a roughing flotation stage, the purpose of which is to recover as much of the target material as possible, which is more favorable to the recovery rate than the grade of the mineral; The concentrate produced in the rougher flotation stage enters the finer flotation stage or the concentrator stage, the purpose of which is to increase the grade until the required purity is reached to feed the subsequent stages; recycling tailings produced by the clean flotation to said rougher flotation to recover material not floated in the route; The tailings produced by the roughing flotation are introduced into the second recovery stage, which consists of scavenging flotation, the purpose of which is to increase the total recovery rate of the flotation route, recover materials that were not floated in the previous stage, and obtain discharged tailings with a lithium sulfate grade of 0.2% Li.
2. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 1, characterized in that: Grinding of the material is carried out in a folding crusher and a cage mill with the aim of releasing the lithium sulfate crystals present in the potassium carnallite matrix and preparing the potassium carnallite matrix for the rougher flotation.
3. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 2, characterized in that: The pre-saturated, balanced brine is added to the mill housing of the cage mill to remove solids that may be embedded in the pre-saturated, balanced brine.
4. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 1, characterized in that: After the grinding stage, the salt is contacted with a brine pre-saturated with the same salt to produce a slurry with a high solids percentage (40% to 50%); 50% of a flotation agent (amine collector) was added to the slurry to condition the resulting material.
5. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 1, characterized in that: The recycled tailings from the cleaning flotation stage and the concentrate from the scavenging flotation are added to the roughing flotation to produce a slurry of about 30% to 35% solids fed to the roughing flotation; in addition, the remaining 30% of collector and frother are added to the tank for the roughing flotation.
6. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 1, characterized in that: The rougher flotation is operated in a recovery mode to obtain more than 50% lithium sulfate monohydrate; The rougher flotation tailings with low sulfate monohydrate content are subjected to classification and regrinding stages in a cage mill.
7. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 6, characterized in that: The regrind and undersize materials extracted from the fractionation are pooled together and together with the remaining percentage of collectors and frothers become the feed to the scavenger flotation stage where the industrial tailings produced have the lowest levels of lithium sulphate.
8. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 1, characterized in that: The rough concentrate obtained from the clean flotation stage is concentrated to a lithium sulphate level of 85%.
9. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 8, characterized in that: The material obtained from the concentration flotation stage is subjected to a filtration stage to obtain a stockpile with a high lithium sulfate content of less than 85%.
10. The method for obtaining lithium sulfate monohydrate ore with low impurity content according to claim 9, characterized in that: The stockpile is washed with hot water using a sprayer to dissolve chlorine impurities and improve the grade of the product to obtain a grade higher than 90%.