CN111519042A

CN111519042A - Process for treating lithium-containing materials

Info

Publication number: CN111519042A
Application number: CN202010274898.7A
Authority: CN
Inventors: 亚特达·沙玛
Original assignee: Ryder Advanced Materials Co ltd
Current assignee: Ryder Advanced Materials Co ltd; Reed Advanced Materials Pty Ltd
Priority date: 2012-08-13
Filing date: 2013-08-01
Publication date: 2020-08-11
Also published as: JP6275138B2; WO2014026217A1; AU2013201833B2; CL2014001656A1; KR20150041661A; CA2851786C; CN104271781A; KR101857458B1; CA2851786A1; MY163075A; US20150152523A1; JP2015531826A; AU2013201833A1

Abstract

A process (10) for the treatment of lithium-containing materials, the process comprising the steps of: (1) preparing a process liquid from the lithium-containing material (12); (2) passing the process liquor produced in step (1) to a series of impurity removal steps (36) to produce a substantially purified lithium chloride solution; and (3) subjecting the purified lithium chloride solution produced in step (2) to an electrolysis step (70) to produce a lithium hydroxide solution.

Description

Process for treating lithium-containing materials

Technical Field

The present invention relates to the processing of lithium-containing materials.

More particularly, the invention relates to processes for the treatment of lithium-containing materials and the production of lithium hydroxide and lithium carbonate. The process electrolyzes a lithium chloride solution obtained from spodumene ore or concentrate, or brine. In general, the process of the present invention is directed to providing a high purity or battery grade lithium hydroxide and lithium carbonate product.

The process of the present invention may further provide a hydrochloric acid product. Further, in general, the process of the present invention employs a noble metal-containing Mixed Metal Oxide (MMO) electrode, thereby increasing the efficiency of the electrochemical link of the process.

Background

Existing processes for producing lithium carbonate from lithium-containing ores or concentrates generally subject the alpha-spodumene ore or concentrate to a heat treatment. This heat treatment may be referred to as a decrepitation process and may convert alpha-spodumene to beta-spodumene, which in turn is capable of being dissolved by acid solutions. The step of dissolving the β -spodumene in an acid solution is performed in a kiln and produces a soluble lithium salt. The lithium salt is delivered to one or more vessels where it is purified. The leached crude lithium salt is then subjected to a step of adjusting the pH of the slurry so that specific impurities, including iron and magnesium, will be precipitated out. Thus, the purified lithium salt may be treated with sodium carbonate to produce lithium carbonate. The lithium carbonate may then be treated with slaked lime to form lithium hydroxide.

The process for producing lithium carbonate and lithium hydroxide from brines generally involves the use of an evaporation pond to increase the concentration of the salts it contains, followed by a series of steps to reduce the impurity levels.

The above processes of the prior art are relatively inefficient in removing impurities present in the leachate which results in the production of lithium hydroxide and lithium carbonate products of lower purity.

It is therefore an object of the process of the present invention to overcome one or more of the problems of the prior art described above, or at least to provide a useful alternative thereto.

The background description provided above is for the purpose of facilitating understanding of the invention only. The above description is not intended to be an indication or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application.

In the description and claims of this application, the word "comprising" is to be understood as meaning the inclusion of a stated item or group of items but not the exclusion of any other item or group of items, except where the word "comprising" requires otherwise, depending on the context.

The term "cell grade lithium carbonate" refers to a product having a purity of about 99.5% or greater. Similarly, the term "battery grade lithium hydroxide" refers to a product having a purity of about 99% or greater.

Disclosure of Invention

According to the present invention there is provided a process for the treatment of lithium-containing materials, the process comprising the steps of:

(1) preparing a process solution from the lithium-containing material;

(2) subjecting the process liquor produced in step (1) to a series of impurity removal steps, thereby producing a substantially purified lithium chloride solution;

(3) subjecting the purified lithium chloride solution produced in step (2) to an electrolysis step, thereby producing a lithium hydroxide solution; and

(4) carbonizing the lithium hydroxide solution generated in step (3) by passing compressed carbon dioxide into the solution, thereby generating a lithium carbonate precipitate;

wherein the lithium-containing material is an alpha-spodumene ore or concentrate, and the process further comprises: a step of first calcining said alpha-spodumene ore or concentrate to produce beta-spodumene.

As an embodiment of the present invention, the process liquid of step (1) is prepared in the form of a leachate. Preferably, the leachate is formed by subjecting the lithium-containing material to a leaching step in which the material is leached by hydrochloric acid.

Preferably, the impurity removal step as the step (2) further comprises a concentration step of concentrating the leachate to a level at which lithium chloride is nearly saturated.

The lithium hydroxide solution produced in step (3) may be thickened by evaporation of water to produce lithium hydroxide monohydrate crystals.

As another aspect of the present invention, a part of the lithium hydroxide solution generated in step (3) is thickened by evaporation/crystallization to generate lithium hydroxide monohydrate crystals, and another part thereof is carbonized by passing compressed carbon dioxide into the solution to generate lithium carbonate precipitate.

Preferably, the impurity removal step of step (2) comprises one or more high temperature hydrolysis of Al and Fe chlorides, increasing the pH to precipitate hydroxides of Al, Fe, Mg and Mn, precipitating lithium carbonate to remove Ca, and fractional crystallization to remove Na and K.

Further preferably, said fractional crystallization to remove Na and K is performed immediately after said concentration step.

The impurity removal step preferably further comprises an ion exchange step. Preferably, the ion exchange step removes substantially all of the calcium, magnesium and other multivalent cations present in the leachate. Further preferably, the multivalent cations are removed to a level of less than about 10 ppm.

It is further preferred that the water evaporated from the solution in the evaporation/crystallization is recompressed, mixed with make-up steam and used for evaporation/crystallization. The evaporation/crystallization step preferably employs a vacuum evaporative crystallizer.

Preferably, the β -spodumene is cooled and ground prior to the leaching step preferably the β -spodumene is ground to below about 300 μm further preferably the β -spodumene is ground to about 75 μm particle size P₈₀。

Preferably, the leaching step is carried out at elevated temperature.

Preferably, the hydrochloric acid solution used in the leaching step is about 20% HCl w/w.

Further preferably, said elevated temperature of the leaching step is about the boiling point of the hydrochloric acid solution employed in the leaching step.

The leaching step is preferably carried out at atmospheric pressure.

In one version of the invention, the leaching step is carried out with a residence time of about 6 to 10 hours in a chlorination kiln at about 108 ℃. Preferably, the residence time is about 8 hours.

Drawings

For exemplary purposes, the process of the present invention will be described below with reference to one embodiment and the accompanying drawings, wherein

Fig. 1 is a schematic flow diagram illustrating a process for treating a lithium-containing material according to an embodiment of the present invention, wherein the lithium-containing material is an α -spodumene concentrate.

Detailed Description

Fig. 1 shows a process 10 for the treatment of lithium-containing material according to one embodiment of the present invention, in this embodiment the lithium-containing material is provided in the form of an alpha-spodumene concentrate.

All process elements present in the process 10 are performed with full process instrumentation and control.

α -spodumene concentrate 12 enters a calcination step in which the concentrate 12 is calcined in a calciner 14 at a temperature between about 1050 ℃ and 1100 ℃ to convert α -spodumene to β -spodumene for leaching the off-gases from the calciner are directed through a cyclone (not shown) and an electrostatic precipitator (not shown) to bring it into compliance with well-known environmental emission standards, the hot calcine obtained enters a cooler 16 and is directly cooled to about 80 ℃ and then dry-milled (dry-milled) in a mill, for example in a closed-circuit ball mill 18, to less than 300 μm, for example to a particle size P of about 75 μm₈₀。

After being stored in a surge bin (not shown), the ground beta-spodumene is mixed in a pulping step with 20% hydrochloric acid w/w 20 with a stoichiometric excess (stoichiometric ex) of at least 40-300%. The pulping step feeds a leaching step, such as a leaching circuit 22, which includes a first leaching stage 24 and a second leaching stage 26.

The leaching step is carried out in successive leaching tanks at about 108 c for a period of about 6 to 12 hours, for example about 8 hours, the temperature being the boiling point of the hydrochloric acid leachate added in the pulping step. About 40% pulp concentration is used in the leach circuit 22 to maximize leach concentration and ensure that the solid solubility of lithium carbonate is not exceeded during leaching. The flue gas may be cleaned in a wet scrubber (not shown). The leaching step 22 produces a slurry and a process liquor, such as a leach liquor. The lithium and aluminosilicate in the beta-spodumene leach into solution with other impurities, thereby forming a sub-saturated concentration of lithium carbonate in the leach solution.

Leachate from the leach circuit 22 is passed into a thickening circuit 28, which preferably includes two

stages

28a and 28b, in abutment with the two

stages

24 and 26 of the leach circuit 22. The overflow from the thickening circuit 28 is routed to a pyrohydrolysis step 30, which is performed at about 300 ℃, and in which the chlorides of Al and Fe present in the leachate are converted into their respective insoluble oxides 32. All remaining HCl is also re-separated in the HCl removal step 34.

In addition to re-separating the Al and Fe using the pyrohydrolysis step 30 as described in the previous paragraph, a substantial portion of the remaining soluble iron, aluminum and magnesium will be removed from the leachate by a series of impurity removal steps, collectively referred to in fig. 1 as impurity removal step 36. The impurity removal step 36 further includes a pH adjustment step 38 that increases the pH to 9 by adding LiOH 40. The product of step 38 enters a belt filter 42 through which the precipitate containing Al, Fe, Mn and Mg is re-separated. The impurity removal step 36 further includes a calcium precipitation step 44 in which sodium carbonate (i.e., soda ash) or lithium carbonate 46 is added to form a calcium-containing precipitate 48 in another belt filter 50.

The thicker underflow product 52 from the second stage thickening step 28b is passed to a drying step 54 before being used as a waste 56 and then disposed of 58.

The liquid product of the belt filter 50, which is mainly a LiCl solution, goes to a concentration step 60 and further to a fractional crystallisation step 62. In the concentration step 60, the LiCl solution is concentrated to near the saturation point, e.g. 35-40% LiClw/w, and cooled to below zero. In a subsequent fractional crystallisation step 62, a majority of the Na and K containing impurities 64 are removed by fractional steps, for example NaCl and KCl crystals, respectively.

As noted above, after substantially all of the impurities have been removed, the lithium chloride solution is passed to an ion exchange step 66 which includes substantially all of the residual calcium, magnesium and other multivalent cations being removed to a level below about 10ppm, for example 1ppm, by an ion exchange (IX) column 68.

The further purified lithium chloride solution is then heated to 90 ℃ and pumped to an electrolysis step 70, which employs several cells, for example 6 to 20 cells, in which lithium hydroxide, chlorine and hydrogen are produced by consuming lithium chloride and water.

After passing through the electrolytic cell, the dilute or depleted lithium chloride solution contains dissolved chlorine gas. The dissolved chlorine gas will be removed in two stages before the dilute lithium chloride solution is recycled to the pulping step in the previous stage of the leaching circuit 22. In the first stage, hydrochloric acid is added to the lithium chloride solution to lower the pH to <5, which forces part of the chlorine out of solution. The remaining dissolved chlorine is then removed by blowing off the solution (not shown).

Chlorine and hydrogen as by-products are mixed to produce hydrochloric acid HCl which can be used in the pulping step and the leach circuit 22.

The lithium hydroxide solution obtained by the electrolysis step 70 is first passed into an incubator 72 where, as is clearly shown in fig. 1, the lithium hydroxide may be either (1) evaporated and crystallized to form lithium hydroxide monohydrate crystals, or (2) sent to a carbonization step for conversion to lithium carbonate.

In a first of the above options, the lithium hydroxide in solution is crystallized in a vacuum crystallization evaporator 80 (Oslo type), for example, operating at about 80 ℃ and a pressure of about 45kpa (a). The residence time was about 60 minutes in order to obtain a crude crystalline product. The generated water vapor is recompressed, mixed with make-up steam and used as a heat carrier for the crystallizer 80.

The lithium hydroxide crystals were washed with cold water (not shown) to obtain a washing efficiency of 99%. As indicated above, the resulting washThe wash liquor is returned to the leach circuit 22 by recirculation. The solids from the centrifuge are fed to an indirect firing kiln or dryer 82 operating at about 120 ℃ to dry the crystals. The obtained crystal product is battery-grade LiOH.H₂O, which is pneumatically conveyed to the product bin 84 and cooled to 50 ℃ within the shell screw conveyor 86 as it is finally conveyed to a bagging station (not shown).

In a second of the above options, lithium carbonate is generated by carbonizing a lithium hydroxide solution by passing compressed carbon dioxide gas 88 into the lithium hydroxide solution in a carbonization vessel 90 to precipitate lithium carbonate. The resulting slurry is fed through a filter 94 to a washer/centrifuge 92, after which the wash liquor and any residual lithium hydroxide solution or mother liquor is recycled to the electrolysis step 70. The wet lithium carbonate crystals are fed to a dryer 96 where the crystals are dried with hot air. The hot air is heated with air at an intermediate pressure. After drying, the battery grade lithium carbonate is micronized to the particle size desired by the consumer before being transferred to a storage bin and subsequently packaged (not shown).

In the whole process, make-up water formed by condensation is used as water for heat treatment, water for cold treatment and cooling water. Since the process does not return condensate, there is an overall positive water balance and process water of about 1/10 is exchanged to a sewage system (not shown).

It is contemplated that tantalum and aluminum may also be decomposed using the process of the present invention. The filter residue from the thickening step may be exchanged to a tantalum recovery process (not shown). The effluent from the lithium recovery process may be fed to a belt filter to remove moisture, which is returned to the tantalum recovery process. Filtration without washing and with 19m²The filtration zone of (1). The filter residue from the belt filter is dried in a direct kiln. The dried aluminium silicate is cooled to 50 ℃ in a shell screw conveyor and then transferred pneumatically to a storage bin, and then dispensed.

According to another embodiment of the invention, the lithium-containing material is provided in the form of a lithium-containing brine. The brine does not need to be subjected to the calcination, cooling, grinding and leaching steps described in the previous example of the invention, while the remaining steps of the process are essentially the same as described in the previous example.

In summary, the present invention provides a process for obtaining high purity or cell grade lithium hydroxide and lithium carbonate products from alpha-spodumene ore or concentrate, or from lithium-containing brines, while also producing a hydrochloric acid gas product.

Modifications and substitutions that may be readily apparent to those skilled in the art are intended to be included within the scope of the present invention. For example, the leaching circuit 22 may comprise only one leaching stage/process without departing from the scope of the invention.

Claims

1. A process for the treatment of lithium-containing materials, the process comprising the steps of:

(1) subjecting the lithium-containing material to a leaching step in which the lithium-containing material is leached by hydrochloric acid at an elevated temperature around the boiling point of hydrochloric acid to produce a leachate, the leaching step comprising a first leaching step and a second leaching step;

(2) passing the leachate into a thickening circuit comprising a first thickening step interfacing with the first leaching step and a second thickening step interfacing with the second leaching step; the overflow from the first and second thickening steps is then subjected to pyrohydrolysis, whereby the aluminium and iron chlorides therein are converted into their respective insoluble oxides, the insoluble oxides are removed, and all remaining HCl is separated in an HCl removal step; the underflow of the first thickening step, interfacing with the first leaching step, enters the second leaching step, and a second thickening step, interfacing with the second leaching step; the underflow of the second thickening step opposite the second leaching step becomes waste;

(3) subjecting the leachate produced in step (2) to a series of impurity removal steps, thereby producing a substantially purified lithium chloride solution; and

(4) passing the purified lithium chloride solution produced in step (3) to an electrolysis step in which only the lithium chloride and additional water are consumed, thereby producing only lithium hydroxide solution, chlorine gas and hydrogen gas;

(5) mixing the chlorine gas and hydrogen gas produced in step (4) to produce hydrochloric acid and passing the hydrochloric acid to the leaching step of step (1); and

(6) carbonizing the lithium hydroxide solution generated in step (4) by passing compressed carbon dioxide into the solution, thereby generating a lithium carbonate precipitate;

2. The process according to any one of the preceding claims, wherein the impurity removal step as step (3) further comprises a concentration step of concentrating the leachate to a point where lithium chloride is nearly saturated.

3. The process according to any one of the preceding claims, wherein the lithium hydroxide solution formed in step (4) is thickened by evaporation of water to form lithium hydroxide monohydrate crystals.

4. A process according to any one of the preceding claims, wherein a portion of the lithium hydroxide solution produced in step (4) is thickened by evaporation/crystallization to produce lithium hydroxide monohydrate crystals, and another portion thereof is carbonized by passing compressed carbon dioxide into the solution to produce a lithium carbonate precipitate.

5. The process according to any one of the preceding claims, wherein the impurity removal step of step (3) comprises increasing the pH to precipitate hydroxides of Al, Fe, Mg and Mn, precipitating lithium carbonate to remove Ca, and fractional crystallization to remove Na and K.

6. The process according to claim 4, wherein the fractional crystallization to remove Na and K is performed immediately after the concentration step.

7. The process according to claim 5 or 6, wherein the step of removing impurities preferably further comprises a step of ion exchange.

8. A process according to claim 7, wherein the ion exchange step removes substantially all of the calcium, magnesium and other multivalent cations present in the leachate.

9. The process of claim 8, wherein the multivalent cations are removed to a level of less than about 10 ppm.

10. The process according to claim 8 or 9, wherein the multivalent cations are removed to a level of about 1 ppm.

11. A process according to any one of claims 4 to 10, wherein water evaporated from the solution in the evaporation/crystallisation is recompressed, mixed with make-up steam and used for the evaporation/crystallisation.

12. The process according to any one of claims 4 to 11, wherein the evaporation/crystallization step preferably employs a vacuum evaporation crystallizer.

13. The process according to any one of the preceding claims, wherein the beta-spodumene is cooled and ground prior to the leaching step.

14. The process of claim 13, wherein the beta-spodumene is milled to below about 300 μ ι η.

15. The process of claim 13 or 14, wherein the β -spodumene is ground to a particle size P of about 75 μ ι η₈₀。

16. The process according to any one of the preceding claims, wherein the hydrochloric acid solution used in the leaching step is about 20% HCl w/w.

17. The process according to any one of the preceding claims, wherein the leaching step is preferably carried out at atmospheric pressure.

18. The process according to any one of the preceding claims, wherein the leaching step is carried out with a residence time of about 6 to 10 hours in a chlorination kiln at about 108 ℃.

19. The process of claim 18, wherein the leaching step is performed over a residence time of about 8 hours.