EP-4735384-A1 - GRAPHITE MATERIAL PURIFICATION PROCESS

EP4735384A1EP 4735384 A1EP4735384 A1EP 4735384A1EP-4735384-A1

Abstract

The present invention relates to an improved graphite material purification process, the process comprising the steps of: (i) Passing a concentrate of a graphite material to be purified to an oxidative leach stage; (ii) Passing a product of the oxidative leach stage of step (i) to a solid liquid separation stage producing a liquid product and a solid product; (iii) Passing the solid product of the solid liquid separation stage of step (ii) to a caustic leach stage; (iv) Passing a product of the caustic leach stage of step (iii) to a solid liquid separation stage producing a liquid product and a solid product; (v) Passing the solid product of the solid liquid separation stage of step (iv) to an acid leach stage; and (vi) Passing a product of the acid leach stage of step (v) to a solid liquid separation stage producing a liquid product and a solid product, wherein the solid product comprises a purified graphite material.

Inventors

TURNER, DUNCAN WILLIAM
Phillips, Martin John

Assignees

Talga Technologies Limited

Dates

Publication Date: 20260506
Application Date: 20240628

Claims (15)

1 . An improved graphite material purification process, the process comprising the steps of: (i) Passing a concentrate of a graphite material to be purified to an oxidative leach stage; (ii) Passing a product of the oxidative leach stage of step (i) to a solid liquid separation stage producing a liquid product and a solid product; (iii) Passing the solid product of the solid liquid separation stage of step (ii) to a caustic leach stage; (iv) Passing a product of the caustic leach stage of step (iii) to a solid liquid separation stage producing a liquid product and a solid product; (v) Passing the solid product of the solid liquid separation stage of step (iv) to an acid leach stage; and (vi) Passing a product of the acid leach stage of step (v) to a solid liquid separation stage producing a liquid product and a solid product, wherein the solid product comprises a purified graphite material.
2. The process of claim 1 , wherein the oxidative leach stage of step (i) comprises a first oxidative leach portion and a second oxidative leach portion.
3. The process of claim 2, wherein the first oxidative leach portion is operated under conditions in which sulphide minerals present are oxidised to sulphates.
4. The process of claim 2 or 3, wherein the first oxidative leach portion operates: (i) with a target redox potential of > about 425 mV (versus Ag/AgCI); (ii) with a pH of > 10; (iii) with a slurry density of between about 15 to 35% w/w solids, for example about 20% w/w; (iv) at a temperature of between about 30 to 60oC; and/or (v) with a residence time of between about 30 to 60 minutes.
5. The process of any of claims 2 to 4, wherein at least one of sodium hypochlorite or sodium chlorate is utilised as the oxidant in the first oxidative leach portion of the oxidative leach stage of step (i).
6. The process of any of claims 2 to 5, wherein the second oxidative leach portion is operated under conditions in which, if present, iron, magnesium and potassium minerals are leached.
7. The process of any of claims 2 to 6, wherein the second oxidative leach portion operates: (i) at a temperature of about 40 to 10OoC; (ii) over multiple leach stages; (iii) with a slurry density of between about 15 to 35% w/w solids, for example about 20% w/w; (iv) with a residence time in the range of about 2 to 6 hours; (v) with an HCI addition rate of between about 150 to 350 kg/t feed; and/or (vi) with a background HCI acidity of between about 30 to 60 g/L.
8. The process according to any of the preceding claims, wherein the caustic leach stage of step (iii) operates: (i) in a counter-current manner; (ii) under pressure; (iii) at a temperature of between about 100 to 220oC; (iv) with a starting slurry density of between about 150 to 250 g/L solids; (v) with a total residence time of between about 2 to 16 hours; and/or (vi) with a background NaOH concentration of between about 100 to 500 g/L.
9. The process according to any one of the preceding claims, wherein the caustic leach stage is operated at a pressure below 5 bar.
10. The process according to any one of claim 1 to 8, wherein the caustic leach stage is operated at a pressure between 20 and 25 bar.
11 . The process according to any of the preceding claims, wherein the lixiviant of acid leach stage (v) is selected from hydrochloric acid or sulphuric acid.
12. The process according to claim 11 , wherein the lixiviant of acid leach stage (v) is hydrochloric acid, and the acid leach stage (v) is conducted (i) in multiple stages; (ii) at a temperature of between about 60 to 100°C; (iii) with a slurry density of between about 15 to 35% w/w, for example about 20% w/w; (iv)with a total residence time of between about 2 to 6 hours; and/or (v) with a background HCI acidity of between about 30 to 60 g/L.
13. The process according to any of the preceding claims, wherein a caustic containing leachate from the caustic leach stage of step (iii) is recycled by way of a caustic regeneration step to which lime and/or hydrated/slaked lime is fed, and from which regenerated caustic is recovered and a residue of silicates and aluminium produced.
14. The process according to any of the preceding claims, wherein a reagent recovery step, including crystallisation and chlor-alkali electrolysis stages, is provided and to which a liquid product of the slurry solid liquid separation step (iv) is passed.
15. The process according to any of the preceding claims, wherein the process further comprises a first effluent treatment, or brine treatment, stage in which liquid products from the oxidative leach stage of step (i), the caustic leach stage of step (iii), and the acid leach stage of step (v) are combined.

Description

GRAPHITE MATERIAL PURIFICATION PROCESS Field of the Invention [0001] The present invention relates to an improved graphite material purification process. [0002] More particularly, the graphite material purification process of the present invention is intended to be applicable to the purification of low graphite content materials. [0003] In particular, the graphite material purification process of the present invention is intended for the production of graphite material that is of a purity suitable for use in the production of lithium-ion batteries (LiBs). Background Art [0004] Graphite that is to be utilised in the production of lithium-ion batteries (LiBs) is required to be highly pure, for example greater than or equal to about 99.95% Loss on Ignition (LOI). This requirement presents challenges to producing suitable graphite product from material with relatively low graphite content, for example 60 to 70% Cg, and in which there are relatively high levels of silicate, sulphide, titanium and base metal minerals. These challenges are heightened if the contaminant minerals are highly disseminated throughout the graphite ore and it is desired to reduce or minimise carbon losses. [0005] Presently employed methods for the purification of graphite for use in the production of LiBs employ particularly aggressive acid leaching steps, typically employing a leach step requiring high concentrations and volumes of hydrofluoric acid. This brings significant environmental and occupational health and safety concerns. These methods also have low levels of carbon recovery, for example below about 85%. Further, these methods generally also start with graphite materials with greater or equal to 90% carbon content. [0006] There would be significant advantage and benefit to providing an improved graphite material purification process that reduced carbon losses and/or reduced reliance on large volumes of highly concentrated acids and/or did not require the use of hydrofluoric acid. [0007] The graphite material purification process and product of the present invention have as one object thereof to overcome substantially one or more of the abovementioned problems associated with prior art processes, or to at least provide a useful alternative thereto. [0008] 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. [0009] 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. [0010] It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 1 micrometer (pm) to about 2 pm should be interpreted to include not only the explicitly recited limits of from about 1 pm to about 2 pm, but also to include individual values, such as about 1 .2 pm, about 1 .5 pm, about 1 .8 pm, etc., and sub-ranges, such as from about 1.1 pm to about 1 .9 pm, from about 1 .25 pm to about 1.75 pm, etc. Furthermore, when “about” and/or “substantially” are/is utilised to describe a value, they are meant to encompass minor variations (up to +/- 10%) from the stated value. [0011 ] It is further to be understood that references to the % recovery or % removal of an element or mineral, or similar, are, unless the context demands otherwise, a reference to the % of that component recovered or removed relative to the original content of the feed to the described process. Other references to % are, again as long as the context does not require otherwise, to be taken as references to weight or wt % (rather than volume or v %). Disclosure of the Invention [0012] In accordance with the present invention there is provided an improved graphite material purification process, the process comprising the steps of: (i) Passing a concentrate of a graphite material to be purified to an oxidative leach stage; (ii) Passing a product of the oxidative leach stage of step (i) to a solid liquid separation stage producing a liquid product and a solid product; (iii) Passing the solid product of the solid liquid separation stage of step (ii) to a caustic leach stage; (iv) Passing a product of the caustic leach stage of step (iii) to a solid liquid separation stage producing a liquid product and a solid product; (v) Passing the solid product of the solid liquid separation stage of step (iv) to an acid leach stage; and (vi) Passing a product of the acid leach stage of step (v) to a solid liquid separation stage producing a liquid product and a solid product, wherein the solid product comprises a purified g