AU2017235956A1

AU2017235956A1 - Method of Processing Lithium-Bearing Ores

Info

Publication number: AU2017235956A1
Application number: AU2017235956A
Authority: AU
Inventors: Michael Rodriguez
Original assignee: POSEIDON NICKEL Ltd
Current assignee: POSEIDON NICKEL Ltd
Priority date: 2016-09-29
Filing date: 2017-09-28
Publication date: 2018-04-12

Abstract

Abstract A method of processing lithium-bearing ores, the method comprising the steps of: transporting a lithium-bearing ore to an existing nickel processing facility; and crushing the lithium-bearing ore to produce a fine ore having a desired mineralogy. The method also comprises the step of passing the fine 10 ore through a flotation circuit to produce a lithium concentrate. Figure 1 u 0~ U-~r oZ0 LL-i w 0:5 0O x Cz z zz z o~~~ 00wO <J <4a 0 m 0 -0 /) F- d Lt > LU a1 0

Description

“METHOD OF PROCESSING LITHIUM-BEARING ORES”

Field of the Invention

The present invention relates to a method of processing nickel sulphide ores and other ores and relates particularly, although not exclusively, to such a method for processing lithium-bearing ores.

Background to the Invention

The market for electric vehicles as well as on-grid and off-grid electrical storage batteries is rapidly expanding, and there is also growth in non-battery applications for lithium. This is forcing lithium producers to look for new ways to meet growing demand. Because historic demand for lithium was small and easily satisfied, producers focused on mining only the most accessible, highest-grade lithium minerals and processing them using the most inexpensive (though inefficient) methods. Moving forward, however, deposits of lithium will need to be considered which are of lower grade and more difficult to identify and to mine. Processes for concentrating and extracting lithium oxide and conversion to lithium carbonate will also need to become more efficient and able to accommodate lower grade materials. A new focus on recovery rates and an awareness and understanding of detrimental elements will need to be developed.

Mineral sources of Lithium are predominantly in two forms: in silicates such as the minerals spodumene, zinnwaldite, and tourmaline; and in mica (orthosilicates) such as lepidolite. There are also rarer lithium-bearing minerals belonging to philosilicates, cyclosilicates, phosphates, fluorophosphates, and even clays such as hectorite. Lithium-bearing minerals spodumene, tourmaline and lepidolite are found in association with tantalum and niobium minerals (columbite, tantalite, niobite) in the massive Greenbushes pegmatite in the Yilgarn Craton of Western Australia.

However, most of the current production of lithium comes from evaporation ponds into which lithium-bearing brine (containing highly soluble LiCL) is pumped from underground and allowed to evaporate. The dissolved lithium salts precipitate from the brine and are collected and processed into lithium carbonate (U2CO3), the primary precursor material for many commercial uses of lithium. Conventional lithium production suffers from being landintensive, inefficient, environmentally questionable, and unable to respond quickly to the large increases in lithium demand that are being recorded and forecast for the near future. Many analysts do not anticipate that brine ponds will be capable of satisfying future forecast demand for lithium.

Mineral or non-brine sources of lithium are therefore increasingly being developed, especially as the price of lithium is able to support more inputintensive means of lithium production. The most common mineral source of lithium in Western Australia currently is spodumene, most of which is produced in one location in WA, the Talison mine in Greenbushes. Lepidolite is a secondary but increasingly important source of lithium. While it is slightly more challenging to mine and has inherently lower concentrations of lithium, innovations in this area are taking place at an increasing rate which could make lepidolite economically feasible and thereby greatly expand the world's accessible lithium resources.

Poseidon Nickel Ltd (PNL) has acquired the Lake Johnston and Black Swan nickel mines and is pursuing plans to re-open them both. Previous operators of these mines encountered significant technical obstacles as well as changing market and industry requirements in realizing value from these assets in spite of significant R&D work done at the two sites.

Lake Johnston is a nickel mine and concentrator plant located 110 km west of Norseman that has operated since 2001. Discovered in 1971, the main ore bodies at Lake Johnston operations (LJO) underground consisted of the Emily Ann massive sulphide deposit (now mined out) and the Maggie Hayes (MH) deposit, consisting of a lower grade disseminated zone that has historically been mined through sub-level caving (called the sub-level cave zone), a higher grade massive zone referred to as North Shoot that was mined only opportunistically (being too narrow for large-scale mechanized mining), and the "Suture Zone" (being situated between the two). PNL's Lake Johnston tenements are historically known to have lithiumbearing pegmatites (intrusive igneous rock comprised of various interesting minerals), and recent reconnaissance has confirmed the presence of surface and near-surface outcrops of Li-bearing minerals (spodumene, lepidolite, and muscovite) in pegmatites. What was not known at the commencement of this project is whether commercial quantities of lithium are present, and whether those lithium-bearing minerals are well-suited to extraction, concentration, and processing into viable lithium materials products.

Lithium ore concentration is typically undertaken in two parallel processes, one being a technical-grade lithium process for use in glass and ceramics which have very low tolerance for contaminants such as iron, and the other(s) being chemical grade lithium for use in the production of U2CO3 (lithium carbonate) and LiHO (lithium hydroxide), the precursor commodity used for batteries and other industrial uses of Li. A number of new hydrometallurgical processes are being developed such as SiLeach and L-Max which aim to eliminate the requirement to convert the spodumene from alpha crystal through to beta crystal and treating noncommercial lithium minerals such as lepidolite respectively. These new processes are not commercially proven and insufficient information is currently available on the technical risks associated with the relevant flowsheets.

The L-Max process developed by Lepidico Ltd is mainly intended for lithium minerals that are types of mica, for example lepidiolite. The SiLeach process, evidently an outgrowth or variation of the L-Max process, is being developed by Lithium Australia (LIT). These competing processes were too new for any expert familiar with the technology to state with any confidence how or whether they will work with any given concentrate, or more importantly to PNL, how lithium concentrate should be processed to produce a battery grade hydroxide or carbonate. PNL plan to utilise the existing Lake Johnston nickel sulphide concentrator to treat lithium minerals such as spodumene, petalite, eucryptite, zinnwaldite, and lepidolite to produce a lithium concentrate. As this is substantially different to the original design criteria for Lake Johnston significant research and experimentation must be applied including trial mining and trial processing.

The present invention was developed with a view to providing a method of processing lithium-bearing ores using one of the existing nickel concentrator circuits at LJO (Lake Johnston Operations) to produce a lithium concentrate suitable for the spodumene refiners.

The previous discussion of the background to the invention is intended to facilitate an understanding of the present invention only. The 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 this application. References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.

Summary of the Invention

According to one aspect of the present invention there is provided a method of processing lithium-bearing ores, the method comprising the steps of: transporting a lithium-bearing ore to an existing nickel processing facility; crushing the lithium-bearing ore to produce a fine ore having a desired mineralogy; and, passing the fine ore through a flotation circuit to produce a lithium concentrate.

Typically the step of crushing the lithium-bearing ore is performed by passing the ore through a crushing circuit in the existing nickel processing facility. Preferably fine ore from the step of crushing passes to FOB (Fine Ore Bin) storage. Crushed lithium-bearing ore from the FOB storage is typically subject to wet fine crushing to 100% passing 3mms in a fine crushing step. Advantageously further separation of course from fines is performed in a gravity separation step. Preferably light ore particles, including petalite, from the gravity separation step are passed to a stockpile, and heavy particles from the gravity separation step pass to a dewatering classification step.

Advantageously after the dewatering classification step the fine ore is passed through a milling circuit. The milling circuit comprises a primary ball mill, primary classifying cyclones and a flash flotation process. Preferably underflow from the primary classifying cyclones is passed through the flash flotation process. Preferably excess underflow from the primary classifying cyclones and tailings from the flash flotation, are returned to the primary ball mill. The concentrate from the flash flotation is preferably sent to a flotation circuit.

Preferably the step of crushing the lithium-bearing ore includes passing the ores through a crushing circuit comprising a plurality of crushers and screens. Typically the crushing circuit comprises three crushers and screens operating in series. Preferably crushed ore from a primary crusher passes through a secondary product screen and the undersize ore (fines) from the secondary screen passes to FOB storage. The oversize ore from the secondary screen is sent to a secondary crusher, and the crushed ore from this secondary crusher also passes through the secondary product screen. The oversize ore (middlings) from the secondary product screen is sent to a tertiary crusher, and the crushed ore from this tertiary crusher passes through a tertiary product screen. The undersize ore (fines) from the tertiary product screen also passes to FOB storage. The oversize ore from the tertiary screen is sent back to the tertiary crusher.

Preferably the flotation circuit comprises a rougher flotation tank. Preferably sinks from the rougher flotation tank are sent to a series of scavenger flotation tanks, and sinks from the scavenger flotation tanks are sent to tailings thickening. The concentrate from both the rougher flotation tanks and the scavenger flotation tanks are preferably sent to a series of cleaner flotation tanks, via secondary classifying cyclones. Preferably the underflow from the secondary classifying cyclones is passed through a regrind ball mill, and the milled output from the regrind ball mill is recycled through the secondary classifying cyclones. Overflow from the secondary cyclone classifier passes to the cleaner flotation tanks and from there to a concentrate thickener. From the thickener the concentrate is typically sent through an acid scrub before undergoing a magnetic separation step and then a concentrate filtration step. The final product from the concentrate filtration step is then preferably sent to product packaging.

Throughout the specification, 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. Likewise the word “preferably” or variations such as “preferred”, will be understood to imply that a stated integer or group of integers is desirable but not essential to the working of the invention.

Brief Description of the Drawings

The nature of the invention will be better understood from the following detailed description of preferred embodiments of the process, given by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is processing plant flow diagram illustrating a preferred embodiment of a method of processing lithium-bearing ores to produce a lithium concentrate using the LJO concentrator.

Detailed Description of Preferred Embodiments PNL has an overall company objective in defining the opportunities that exist in the lithium market. In order to move towards that goal, an essential R&D objective was to trial mine a representative sample of pegmatite (up to 20,000 t), to concentrate the bulk sample of ore at LJO, and to see the concentrate further processed into a viable U2CO3 product. To do this, a number of unknowns had to be addressed. These included gaining an understanding of the specific lithium minerals that exist at Jake Johnston, developing an understanding of how to use the LJO concentrator to produce a lithium concentrate, and understanding the alternatives for downstream processing into Li2C03. Intrinsic to these objectives is gaining an understanding of the various tramp minerals, deleterious elements, the grade of the minerals, and their responsiveness to various processing treatments. A preferred method of processing a lithium-bearing ore using the LJO processing plant 10 is illustrated in Figure 1.

The method comprises the step of transporting a lithium-bearing ore, typically comprising an LJO pegmatite ore, to a ROM (Run of Mine) Bin 11 of the processing plant 10. The method of processing the lithium-bearing ore comprises the further steps of crushing the lithium-bearing ore to produce an ore having a desired fine particle size. Typically the step of crushing the lithium-bearing ore includes passing the ore through a crushing circuit 12 comprising a plurality of crushers and screens which are part of the existing LJO nickel processing facility. Preferably the crushing circuit 12 comprises three crushers 14 and screens 16 operating in series. The crushed ore from a primary crusher 14a passes through a secondary product screen 16b, and the undersize ore (fines) from the secondary screen 16b passes to FOB (Fine Ore Bin) storage 17. The oversize ore from the secondary screen 16b is sent to a secondary crusher 14b, and the crushed ore from this secondary crusher 14b also passes through the secondary product screen 16b. The oversize ore (middlings) from the secondary product screen 16b is sent to a tertiary crusher 14c, and the crushed ore from this tertiary crusher 14c passes through a tertiary product screen 16c. The undersize ore (fines) from the tertiary product screen 16c also passes to FOB (Fine Ore Bin) storage 17. The oversize ore from the tertiary screen 16c is sent back to the tertiary crusher 14c.

In the flowsheet of Figure 1 the crushed lithium-bearing ore from FOB storage 17 is typically subject to wet fine crushing to 100% passing 3mms in a fine crushing step 19, and then further separation of course from fines in a gravity separation step 21. Light ore particles are passed to a petalite stockpile 23, and the heavy particles pass to a dewatering classifier 25. Any light ore particles from the dewatering classifier are returned to the gravity separation 21. Heavy ore particles from the dewatering classifier 25 are passed to a milling circuit 18. The milling circuit 18 comprises a primary ball mill 20, primary classifying cyclones 22 and flash flotation 24.

From the primary ball mill 20 the ore is passed through the primary classifying cyclones 22. Preferably the underflow from the primary classifying cyclones 22 is passed through a flash flotation tank 24. Excess underflow from the primary classifying cyclones 22, and tailings from the flash flotation tank 24, are returned to the primary ball mill 20. The concentrate from the flash flotation tank 24, together with the overflow from the primary classifying cyclone 22 eventually flows to a flotation circuit 40 which is also part of the existing LJO nickel processing facility. The lithium-bearing slurry is passed through the flotation circuit 40 to produce a lithium concentrate product.

The flotation circuit 40 comprises a rougher flotation tank 42. The sinks from the rougher flotation tank 42 are eventually sent to a series of scavenger flotation tanks 44, and the sinks from the scavenger flotation tanks are sent to tailings thickening 45. The concentrate from both the rougher flotation tanks 42 and the scavenger flotation tanks 46 are sent to a series of cleaner flotation tanks 48a and 48b, via secondary classifying cyclones 28. Preferably the underflow from the secondary classifying cyclones 28 is passed through a regrind ball mill (concentrate regrind) 26, and the milled output from the regrind ball mill is recycled through the secondary classifying cyclones 28. Overflow from the secondary cyclone classifier 28 passes to the cleaner flotation tanks 48a and 48b and from there to a concentrate thickener 62. From the thickener 62 the concentrate is sent through an acid scrub 66 before undergoing magnetic separation at step 68 and then filtration at step 70. The final concentrate product is then sent to product packaging 72.

As noted above, there are a number of unknowns which could not be established except by experiment. In order to address the unknowns listed above, several trial mine and concentrator runs of approximately 5,000 t are being undertaken for the Lake Johnston Operations (LJO) site. Below are detailed some of the experimental activities being conducted to establish key operating parameters of the preferred method of processing lithium-bearing ores according to the invention:

R&D Experimental Activity: LiProcOI A suitable quantity of Li-bearing ore was identified, extracted, and processed at the LJO concentrator to produce a quantity of Li20-equivalent concentrate. This required a quantity of testwork to determine the makeup of the ore and to develop a flowsheet for the modified concentrator. Once produced, a further objective was to see the concentrate processed, most likely via a hydrometallurgical process into Li2C03 or equivalent that meets all technical specifications and requirements for the lithium market. The objective of this R&D activity is to learn how to process Li-bearing ores alongside nickel ores at LJO in a parallel but dedicated circuit.

In order to determine whether a viable and technically compliant lithium material product could be produced from Lake Johnston lithium ores using components of the LJO nickel concentrator, a suitable quantity of lithiumbearing ores (e.g. pegmatites) was located at or near the surface close to LJO, minimizing extraction costs and avoiding underground operations if possible. The ore body thus identified was surveyed in order to produce representative samples for the following test work, and to accurately plan the extraction so that the overall trial mine sample would accurately reflect the test work samples. The ore was characterized for mineralogy, elemental composition, comminution properties and other chemical and mechanical characteristics. The distribution and variations of these properties was also noted. A trial concentrator flowsheet is being developed through flotation test work and related activities. One of the LJO concentrator circuits is being suitably modified to reproduce the flowsheet thus developed and adapted to handling the required quantity of material needed for the test. A bulk sample will be extracted, moved to LJO, and experimentally processed in the concentrator circuit. The concentrate will be tested and assessed to determine whether the flowsheet operated as required, and whether the material extracted was as expected. The concentrate will be further tested to determine how it might respond to one or more selected hydromet processes for U2CO3 production.

Based on the results of these tests the bulk sample concentrate will be processed using a selected process into U2CO3 or equivalent (e.g. LiOH, U2O2). The resulting product will be tested to determine whether it meets technical specifications and requirements for lithium products.

Test Results:

Preliminary test work has been undertaken to characterize some of the LJO Li ores and a sample of LJO ore has been evaluated for its compatibility with the L-Max process. Flotation test results for the LJO Li ore (Lepidolite) are shown in Table 1.

While a significant amount of test work remains to be done, early indications are mostly positive. One area of concern is the potential presence of deleterious elements, such as F and K. It is not yet known how this will affect the overall outcome.

Laboratory Flotation Test Work A number of lithium-bearing ore samples were obtained with mineralogy similar to the LJO Li ores. Table 2 is a summary of the mineralogical analysis of the samples tested.

The Li ore samples were each subject to rougher flotation and recleaner flotation to give some indication of the recovery rates for Li, under processing conditions similar to that provided in the LJO concentrator plant. Samples were floated using both tap water and saline water (obtained from the Maggie Hayes mine). In each case the sample was subject to milling to form a slurry which was then subject to rougher flotation. Table 3 is a summary of the rougher flotation test results.

In Table 3 the flotation tests PFT002 and PFT003 compare the same sample (Coarse Spodumene) under different water types (tap and Maggie Hayes [saline] respectively). Similarly for flotation tests PFT004 and PFT005 (Fine Spodumene) and flotation tests PFT006 and PFT007 (Petalite).The rougher flotation test results show that lithium can be recovered from the Li-bearing ores at a reasonable rate using the kind of flotation systems available at the LJO nickel concentrator plant. One surprising result is that recovery rates were actually improved using hyper-saline water (Maggie Hayes ground water) compared to tap water. Another surprising result is that some Li was still recovered from the Petalite, which was not expected to float. A sample of Course Spodumene was also subject to Recleaner Flotation following Rougher Flotation using Maggie Hayes water. The Li recovery rate to recleaner concentrate was about 60%, compared to the recovery to rougher concentrate of about 68%.

Now that preferred embodiments of the method of processing lithium-bearing ores has been described in detail, it will be apparent that the described embodiment provides a number of advantages over the prior art, including the following: (i) It enables a previously non-productive ore body to be turned into a productive one. (ii) It facilitates the processing of lithium-bearing ores using an existing concentrator plant built for an entirely different purpose, thus enabling significant savings in capital costs. (iii) It addresses the current limitations of brine ponds and provides a cost-effective alternative that may be capable of satisfying future forecast demand for lithium.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described and is to be determined from the appended claims.

Claims

The Claims defining the Invention are as follows:

1. A method of processing lithium-bearing ores, the method comprising the steps of: transporting a lithium-bearing ore to an existing nickel processing facility; crushing the lithium-bearing ore to produce a fine ore having a desired mineralogy; and, passing the fine ore through a flotation circuit to produce a lithium concentrate.
2. A method of processing lithium-bearing ores as defined in claim 1, wherein the step of crushing the lithium-bearing ore is performed by passing the ore through a crushing circuit in the existing nickel processing facility.
3. A method of processing lithium-bearing ores as defined in claim 1 or claim 2, wherein fine ore from the step of crushing passes to FOB (Fine Ore Bin) storage.
4. A method of processing lithium-bearing ores as defined in claim 3, wherein crushed lithium-bearing ore from the FOB storage is subject to wet fine crushing to 100% passing 3mms in a fine crushing step.
5. A method of processing lithium-bearing ores as defined in claim 4, wherein further separation of course from fines is performed in a gravity separation step.
6. A method of processing lithium-bearing ores as defined in claim 5, wherein light ore particles, including petalite, from the gravity separation step are passed to a stockpile, and heavy particles from the gravity separation step pass to a dewatering classification step.
7. A method of processing lithium-bearing ores as defined in claim 6, wherein after the dewatering classification step the fine ore is passed through a milling circuit.
8. A method of processing lithium-bearing ores as defined in claim 7, wherein the milling circuit comprises a primary ball mill, primary classifying cyclones and a flash flotation process.
9. A method of processing lithium-bearing ores as defined in claim 8, wherein underflow from the primary classifying cyclones is passed through the flash flotation process.
10. A method of processing lithium-bearing ores as defined in claim 9, wherein excess underflow from the primary classifying cyclones and tailings from the flash flotation, are returned to the primary ball mill.
11. A method of processing lithium-bearing ores as defined in claim 10, wherein the concentrate from the flash flotation is sent to a flotation circuit.
12. A method of processing lithium-bearing ores as defined in any one of claims 1 to 11, wherein the step of crushing the lithium-bearing ore includes passing the ores through a crushing circuit comprising a plurality of crushers and screens.
13. A method of processing lithium-bearing ores as defined in claim 12, wherein the crushing circuit comprises three crushers and screens operating in series.
14. A method of processing lithium-bearing ores as defined in claim 13, wherein crushed ore from a primary crusher passes through a secondary product screen and the undersize ore (fines) from the secondary screen passes to FOB storage.
15. A method of processing lithium-bearing ores as defined in claim 14, wherein the oversize ore from the secondary screen is sent to a secondary crusher, and the crushed ore from this secondary crusher also passes through the secondary product screen.
16. A method of processing lithium-bearing ores as defined in claim 15, wherein the oversize ore (middlings) from the secondary product screen is sent to a tertiary crusher, and the crushed ore from this tertiary crusher passes through a tertiary product screen.
17. A method of processing lithium-bearing ores as defined in claim 16, wherein the undersize ore (fines) from the tertiary product screen also passes to FOB storage, and the oversize ore from the tertiary screen is sent back to the tertiary crusher.
18. A method of processing lithium-bearing ores as defined in any one of claims 1 to17, wherein the flotation circuit comprises a rougher flotation tank.
19. A method of processing lithium-bearing ores as defined in claim 18, wherein sinks from the rougher flotation tank are sent to a series of scavenger flotation tanks, and sinks from the scavenger flotation tanks are sent to tailings thickening.
20. A method of processing lithium-bearing ores as defined in claim 19, wherein the concentrate from both the rougher flotation tanks and the scavenger flotation tanks are preferably sent to a series of cleaner flotation tanks, via secondary classifying cyclones.
21. A method of processing lithium-bearing ores as defined in claim 20, wherein the underflow from the secondary classifying cyclones is passed through a regrind ball mill, and the milled output from the regrind ball mill is recycled through the secondary classifying cyclones.
22. A method of processing lithium-bearing ores as defined in claim 21, wherein overflow from the secondary cyclone classifier passes to the cleaner flotation tanks and from there to a concentrate thickener.
23. A method of processing lithium-bearing ores as defined in claim 22, wherein the concentrate from the thickener is typically sent through an acid scrub before undergoing a magnetic separation step and then a concentrate filtration step.
24. A method of processing lithium-bearing ores as defined in claim 23, wherein the final product from the concentrate filtration step is sent to product packaging.