AU2013201833B2

AU2013201833B2 - Processing of Lithium Containing Ore

Info

Publication number: AU2013201833B2
Application number: AU2013201833A
Authority: AU
Inventors: Yatendra Sharma
Original assignee: Reed Advanced Materials Pty Ltd
Current assignee: Reed Advanced Materials Pty Ltd
Priority date: 2012-08-13
Filing date: 2013-03-22
Publication date: 2014-07-17
Anticipated expiration: 2033-03-22
Also published as: CN111519042A; KR101857458B1; MY163075A; CN104271781A; CA2851786C; WO2014026217A1; KR20150041661A; US20150152523A1; CA2851786A1; JP2015531826A; JP6275138B2; AU2013201833A1; CL2014001656A1

Abstract

A process for the treatment of lithium containing ore, the process comprising the steps of: (i) Calcining an alpha-spodumene ore or ore concentrate to produce betaspodumene; (ii) Passing the beta-spodumene of step (i) to a leach step in which the beta-spodumene is leached with hydrochloric acid to produce a pregnant leach solution; (iii) Passing the pregnant leach solution from step (ii) to a series of impurity removal steps in which impurities including iron, calcium and sodium are substantially removed; and (iv) Passing the purified lithium chloride product of step (iii) to an electrolysis step thereby producing a lithium hydroxide solution. CL, t A

Description

- 1 "Processing of Lithium Containing Ore" Field of the Invention [0001] The present invention relates to the treatment of lithium containing ore. [0002] More particularly, the present invention relates to a process for the treatment of lithium containing ore and the production of lithium hydroxide and lithium carbonate. The process utilising the electrolysis of a lithium chloride solution obtained from a spodumene ore. In one form, the process of the present invention is intended to provide a high purity or battery grade lithium hydroxide and lithium carbonate product. [0003] The process of the present invention may further provide a hydrochloric acid product. Still further, the process of the present invention, in one form, utilises precious metal containing mixed metal oxide (MMO) electrodes to heighten the efficiency of an electrochemical portion of the process. Background Art [0004] Known processes for the production of lithium carbonate from lithium containing ores or concentrates typically utilise the thermal treatment of an alpha spodumene ore or concentrate. This thermal treatment can be referred as decrepitation and transforms the alpha-spodumene to beta-spodumene which is in turn able to be solubilised by acid. The step in which the beta-spodumene is solubilised in acid takes place in a kiln and produces soluble lithium salt. The lithium salt is passed to one or more tanks in which the lithium salt is purified. Leached crude lithium salt is subsequently adjusted the pH of the slurry, whereby certain impurities, including iron and magnesium are intended to be precipitated. Thus purified lithium salt is treated with soda ash to produce lithium carbonate. This lithium carbonate can be further treated with hydrated lime to produce lithium hydroxide. [0005] The above described process of the prior art is relatively inefficient in the removal of impurities remaining in the pregnant leach solution, which results in a -2 relatively impure lithium hydroxide and lithium carbonate product. This is particularly problematic when attempting to produce high quality or battery grade lithium hydroxide and lithium carbonate products. [0006] The process of the present invention has as one object thereof to overcome substantially one or more of the above mentioned problems associated with prior art processes, or to at least provide a useful alternative thereto. [0007] The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. This discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application. [0008] Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. [0009] The term "battery grade lithium carbonate" refers to a product having a purity of about 99.5% or higher. Similarly, the term "battery grade lithium hydroxide" refers to a product having a purity of about 99% or higher. Disclosure of the Invention [0010] In accordance with the present invention there is provided a process for the treatment of lithium containing ore, the process comprising the steps of: (i) Calcining an alpha-spodumene ore or ore concentrate to produce beta-spodumene; (ii) Passing the beta-spodumene of step (i) to a leach step in which the beta-spodumene is leached with hydrochloric acid to produce a pregnant leach solution; -3 (iii) Passing the pregnant leach solution from step (ii) to a series of impurity removal steps in which impurities including iron, calcium and sodium are substantially removed; and (iv) Passing the purified lithium chloride product of step (iii) to an electrolysis step thereby producing a lithium hydroxide solution. [00111 The lithium hydroxide solution produced in step (iv) may be thickened by evaporation of water to provide lithium hydroxide monohydrate crystals. [0012] Further, the lithium hydroxide solution produced in step (iv) may be carbonated by passing compressed carbon dioxide through the solution, thereby producing a lithium carbonate precipitate. [0013] In one form of the present invention a first portion of the lithium hydroxide solution produced in step (iv) is thickened by evaporation/crystallisation to provide lithium hydroxide monohydrate crystals and a second portion thereof is carbonated by passing compressed carbon dioxide through the solution, thereby producing a lithium carbonate precipitate. [0014] Preferably, one of the impurity removal steps comprises passing the pregnant leach solution through a solvent extraction circuit in which it is treated with a lithium chloride soluble solvent. The solvent may comprise a higher aliphatic alcohol, for example hexanol or ethylhexanol. The solvent extraction circuit is proposed to provide a substantially pure lithium chloride whilst separating ionic impurities that may include, for example, sodium and calcium. [0015] Preferably, the solvent is recovered by evaporation. The solvent thus recovered is preferably recycled for re-use in the solvent extraction circuit. [0016] The impurity removal steps preferably further comprises an ion exchange step. Preferably, the ion exchange step removes substantially all calcium, magnesium and other multivalent cations remaining in the pregnant leach solution. Still preferably, such multivalent cations are removed to a level of less than about 10 ppm.

-4 [0017] Preferably, the lithium carbonate precipitate is in turn filtered or centrifuged, then dried. [0018] Still preferably, water evaporated from the solution in evaporation/crystallisation is recompressed, combined with make-up steam and utilised in evaporation/crystallisation. The evaporation/crystallisation step preferably utilises a vacuum evaporative crystalliser. [0019] Preferably, the impurity removal steps of step (iii) comprise, in turn, the addition of lime and an oxidising agent such as hydrogen peroxide to oxidise ferrous to ferric. After the addition of the hydrogen peroxide the solution is preferably thickened, the underflow of the thickening step then being filtered and dried to provide an alumina silicate product. [0020] Still preferably, the beta-spodumene of step (i) is cooled and milled prior to the leach of step (ii). The beta-spodumene is preferably milled to less than about 300 pm. [0021] Preferably, the leach of step (ii) is conducted at elevated temperature. [0022] Still preferably, the leach of step (ii) is conducted in a chlorination kiln at about 90 0 C over a residence time of about 30 minutes. Brief Description of the Drawings [0023] The process of the present invention will now be described, by way of example only, with reference to one embodiment thereof and the accompanying drawings, in which: Figure 1 is a schematic flow-sheet depicting a process for the treatment of lithium containing ore in accordance with the present invention. Best Mode(s) for Carrying Out the Invention [0024] In Figure 1 there is shown a process 10 for the treatment of lithium containing ore, in accordance with one embodiment of the present invention.

-5 [0025]AII of the unit operations embodied in the process 10 are intended to operate continuously with full process instrumentation and control being provided for. [0026] An alpha-spodumene concentrate 12 is passed to a calcining step in which the concentrate 12 is calcined in a calcining furnace 14 at about 1050 0 C to 1100 0 C to convert the alpha-spodumene to leachable beta-spodumene. Off gases from the calciner are directed through a cyclone (not shown) and an electrostatic precipitator (not shown) specified to comply with known environmental emissions limits. The hot calcine is passed to a cooler 16 and indirectly cooled to about 80 0 C. It is then dry-milled to less than 300 pm, for example 75 pm, in a mill, for example a closed circuit ball mill 18. [0027] After storage in a surge bin (not shown), the milled beta-spodumene is mixed with at least a 120% stoichiometric excess of (30% w/w acid) hydrochloric acid in a slurrying step 20, for example about 26% to 30% w/w HCI. The slurrying step 20 feeds a leach step, for example a leach circuit 22. [0028] The leach step 22 is conducted at about 95 0 C for a period of about 60 to 90 minutes in continuous leach tanks. A pulp density of about 40% is used in the leach step 22 to maximise the leach concentration and to ensure that the solubility limit of lithium chloride during leaching is not exceeded. Off-gases are cleaned in a wet scrubber (not shown). The leach step 22 produces a residue slurry and a pregnant leach liquor. The lithium and the aluminosilicate in the beta-spodumene leaches into solution with other impurities to give a sub-saturated concentration of lithium chloride in the pregnant leach liquor. [0029] Soluble iron, aluminium and magnesium are removed in large part from the leach liquor through a series of impurity removal steps 24. The impurity removal steps include a pH modification step 26 through the addition of hydrated lime to raise the pH to about 9, and the addition of an oxidising agent, such as hydrogen peroxide (to ensure iron is present in the ferric form). Calcium is then removed in a calcium precipitation step 28 with the addition of either sodium carbonate (soda ash) or lithium carbonate. The combined leached solids and precipitated impurities are thickened in a first thickening step 30, prior to the addition of the -6 sodium carbonate/lithium carbonate to the thickener overflow to remove calcium, after which again the combined leach solution and precipitated solids are passed to a second thickening step 32. [0030] The thickener underflow product of the iron, magnesium and calcium precipitation steps are passed to a filtration step comprising a belt filter (not shown) which has a filtration area of about 156 m 2 and three counter-current washes. From here the product is passed to a drying step 34 before passing to waste 36 and subsequent disposal 38. [0031 ]The pregnant leach solution of lithium chloride obtained as overflow from the thickener 32 is passed to a solvent extraction circuit 40 in which it is treated with a lithium chloride soluble solvent, such as higher aliphatic alcohols, for example hexanol or ethylhexanol, to separate substantially pure lithium chloride from other ionic impurities, such as NaCl, traces of CaC1 2 etc. Purified lithium chloride is then recovered from the organic solvent by evaporating the solvent. The solvent thus recovered is recycled for another solvent extraction (SX) use. [0032] After the removal of substantially all impurities as described above, the lithium chloride solution is passed through an ion exchange step 42, comprising an Ion Exchange (IX) column by which substantially all of any residual calcium, magnesium and other multivalent cations are removed to a level of less than about 10ppm. [0033] The further purified lithium chloride solution is then heated to 90'C and pumped to an electrolysis step 44 comprising a number of electrolysers in which lithium chloride and water are consumed to produce lithium hydroxide, chlorine and hydrogen. After passing through the electrolysers, the weak or depleted lithium chloride solution contains dissolved chlorine gas. Before this weak lithium chloride solution is recycled to the chlorination 20 and leaching 22 steps, the dissolved chlorine is removed in two stages. In a first stage 46, hydrochloric acid is added to the lithium chloride solution to reduce the pH to <5 which forces some of the chlorine gas out of solution. The remaining dissolved chlorine gas is then removed by air stripping the solution (not shown).

-7 [0034] Chlorine and hydrogen produced as by-products are combined to produce HCI acid which is used in the leaching step 22. [0035] The lithium hydroxide solution obtained from the electrolysis step 44 can either be (i) evaporated and crystallised to produce lithium hydroxide monohydrate crystals, or (ii) sent to carbonation step to convert into lithium carbonate, as clearly shown in Figure 1. [0036] In the first of these options, the lithium hydroxide in solution is crystallised in, for example, a vacuum evaporative crystalliser 48 (Oslo type) operating at a temperature of about 80 0 C and pressure of about 45 kPa(a). The residence time is about 60 minutes so as to achieve a coarse crystal product. The resulting water vapour is recompressed, combined with make-up steam and used as the heating medium for the crystalliser 48. [0037] Lithium hydroxide crystals are washed by cold water (not shown) achieving a wash efficiency of 99%. The resulting wash solution is recycled back to the leach circuit as noted above. Solids from the centrifuge are fed to an indirect-fired kiln or dryer 50, operating at about 120 0 C, which dries the crystals. The crystal product is pneumatically conveyed to product bins, and cooled to 50 0 C in a jacketed screw conveyer 52 as it is conveyed from the bins to bagging stations 54. [0038] In the second option noted above, lithium carbonate may be produced by carbonation of lithium hydroxide solution by passing compressed carbon dioxide gas 56 though the solution of lithium hydroxide in a carbonation vessel 58 in which lithium carbonate is precipitated. This slurry is fed to a washer/centrifuge 60 by way of a filter 62, after which wash water is recycled with any remaining lithium hydroxide solution or mother liquor to electrolysis 44. Wet lithium carbonate crystals are fed to a dryer 64 in which hot air is used to dry the crystals. Medium pressure air is used to heat the air. After drying the lithium carbonate may be micronized to a particle size requested by a customer prior to bagging 66. [0039] Condensate throughout the process is used as make-up water for hot process water, cold process water and cooling water. As the process does not -8 return condensate there is an overall positive water balance and about 1

/

1 0 1h of the process water is discharged to a sewerage system (not shown). [0040] It is envisaged that tantalite and alumina may also be recovered using the process of the present invention. The filter cake from the thickening step may be discharged to a tantalite recovery plant (not shown). Discharge from the tantalite recovery plant may be fed onto a belt filter to remove water, which is returned to the tantalite recovery plant. The filter does not use washing and has a filtration are of 19 M 2 . The filter cake from the belt filter is dried in a direct-fired kiln. The dry alumina silicate is cooled to 50 0 C in a jacketed screw conveyor and then pneumatically conveyed to a storage bin prior to dispatch. [0041]As can be seen from the above, the process of the present invention provides a process by which a high purity or battery grade lithium hydroxide and lithium carbonate products may be obtained from an alpha-spodumene ore or concentrate, whilst also allowing the production of a hydrogen chloride gas product. [0042] Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.

Claims

1. A process for the treatment of lithium containing ore, the process comprising the steps of: (i) Calcining an alpha-spodumene ore or ore concentrate to produce beta spodumene; (ii) Passing the beta-spodumene of step (i) to a leach step in which the beta-spodumene is leached with hydrochloric acid to produce a pregnant leach solution; (iii) Passing the pregnant leach solution from step (ii) to a series of impurity removal steps in which impurities including iron, calcium and sodium are substantially removed; and (iv) Passing the purified lithium chloride product of step (iii) to an electrolysis step thereby producing a lithium hydroxide solution.

2. A process according to claim 1, wherein the lithium hydroxide solution produced in step (iv) is thickened by evaporation of water to provide lithium hydroxide monohydrate crystals.

3. A process according to claim 1 or 2, wherein the lithium hydroxide solution produced in step (iv) is carbonated by passing compressed carbon dioxide through the solution, thereby producing a lithium carbonate precipitate.

4. A process according to any one of the preceding claims, wherein a first portion of the lithium hydroxide solution produced in step (iv) is thickened in an evaporation/crystallisation step to provide lithium hydroxide monohydrate crystals and a second portion thereof is carbonated by passing compressed carbon dioxide through the solution, thereby producing a lithium carbonate precipitate. -10

5. A process according to any one of the preceding claims, wherein one of the impurity removal steps comprises passing the pregnant leach solution through a solvent extraction circuit in which it is treated with a lithium chloride soluble solvent.

6. A process according to claim 5, wherein the solvent comprises a higher aliphatic alcohol.

7. A process according to claim 6, wherein the higher aliphatic alcohol is either hexanol or ethylhexanol.

8. The process according to any one of claim 5 to 7, wherein the solvent extraction circuit provides a substantially pure lithium chloride whilst separating ionic impurities.

9. A process according to claim 8, wherein the ionic impurities include sodium and calcium.

10. A process according to any one of claims 5 to 9, wherein the solvent is recovered by evaporation.

11. A process according to claim 10, wherein the solvent recovered is recycled for re-use in the solvent extraction circuit.

12. A process according to any one of the preceding claims, wherein the impurity removal steps further comprise an ion exchange step.

13. A process according to claim 12, wherein the ion exchange step removes substantially all calcium, magnesium and other multivalent cations remaining in the pregnant leach solution.

14. A process according to claim 13, wherein such multivalent cations are removed to a level of less than about 10 ppm.

15. A process according to any one of claims 3 to 14, wherein the lithium carbonate precipitate is in turn filtered or centrifuged, then dried. - 11

16. A process according to any one of claims 2 to 15, wherein water evaporated from the solution in evaporation/crystallisation is recompressed, combined with make-up steam and utilised in evaporation/crystallisation.

17. A process according to claim any one of claims 2 to 16, wherein evaporation/crystallisation utilises a vacuum evaporative crystalliser.

18. A process according to the impurity removal steps of step (iii) comprise, in turn, the addition of lime and an oxidising agent such as hydrogen peroxide to oxidise ferrous to ferric.

19. A process according to claim 18, wherein the oxidising agent is hydrogen peroxide.

20. A process according to claim 19, wherein after the addition of the hydrogen peroxide the solution is thickened, the underflow of the thickening step then being filtered and dried to provide an alumina silicate product.

21. A process according to any one of the preceding claims, wherein the beta spodumene of step (i) is cooled and milled prior to the leach of step (ii).

22. A process according to claim 21, wherein the beta-spodumene is milled to less than about 300 pm.

23. A process according to any one of the preceding claims, wherein the leach of step (ii) is conducted at elevated temperature.

24. A process according to any one of the preceding claims, wherein the leach of step (ii) is conducted in a chlorination kiln at about 90'C over a residence time of about 30 minutes.

25. A process for the treatment of lithium containing ore substantially as hereinbefore described with reference to Figure 1.