AU2016204951A1

AU2016204951A1 - Method of Co-processing Nickel Sulphide Ores

Info

Publication number: AU2016204951A1
Application number: AU2016204951A
Authority: AU
Inventors: Michael Rodriguez
Original assignee: POSEIDON NICKEL Ltd
Current assignee: POSEIDON NICKEL Ltd
Priority date: 2015-07-29
Filing date: 2016-07-14
Publication date: 2017-02-16

Abstract

Abstract 5 A method of co-processing of nickel sulphide ores, the method comprising the steps of: transporting a first nickel sulphide ore comprising a disseminated sulphide ore and talc-carbonate ore to a co-processing facility 10; and transporting a second nickel sulphide ore comprising a disseminated sulphide ore to the co-processing facility 10. The method further comprises 10 the steps of crushing and blending the first and second nickel sulphide ores to produce a blended ore having a desired mineralogy, and passing the blended ore through a flotation circuit 40 to produce a nickel sulphide concentrate comprising at least 5% nickel. 15 Drawing to accompany Abstract: Figure 1 LJO Processing Plant Flow Diagram ---------------------------- I------------ Mine Output Crushing Circuit 14b mb 14 e 16c O eCsheri Crusher 2 ze Crusner 3 Ov Passing passing Pass trg -I ----- - Millng Circuit Tash Screens Classifier oversie - toTails Overflow PrlmaryN Cruhed Ball Mill Sto pilepassing Underffow Concentrate Fash LJO Processing Plant F low Diagra Flotation C e ConditioningTank Sinks Cl ss ir2 i ~Regrind BaR M iOero Underflow -Fiatation Circui6 Conc Rougher Flotation. Sinks Middling Conc Scavenger Conc Flotation (3) Flotation (3) Sinks Sinks To Tails Sinks 0 Coc Cleaner cleaning Conc Flotation 2 scavenger(S) V.ks5 k To Tails] Thickener Feed Tank 66 Thkckener 6 6 Jf Filter ie ed Fin cete rt

Description

2016204951 14 Μ 2016

ORIGINAL

AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION

Invention title: “METHOD OF CO-PROCESSING NICKEL SULPHIDE ORES”

Applicant:

POSEIDON NICKEL LIMITED

Associated Provisional Application No.: 2015903019

The following statement is a full description of the invention, including the best method of performing it known to me: 2 2016204951 14 Μ 2016 “METHOD OF CO-PROCESSING NICKEL SULPHIDE ORES”

Field of the Invention

The present invention relates to a method of co-processing nickel sulphide ores and relates particularly, although not exclusively, to such a method for 5 co-processing a blend of talc-bearing ores and serpentinite ores.

Background to the Invention

Poseidon Nickel Ltd has recently acquired the Lake Johnston and Black Swan nickel mines and is pursuing plans to re-open them both. Previous 10 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.

Black Swan is a nickel deposit 50km north-east of Kalgoorlie consisting of several individual ore bodies. The main Black Swan ore body consists of 15 disseminated sulphide ore and talc-carbonate ore that has been developed as an open-pit mine. The close-by Silver Swan underground mine accessed an aggregated ore body. Mining and concentrator plant operations were suspended in 2009 when the main body of aggregate ore became depleted and the owner at the time was unable to find a way of increasing the low 20 recovery rate of the remaining serpentenite and talc-carbonate ore types.

Even prior to depletion of the developed areas of Silver Swan, Black Swan experienced difficulties meeting the metallurgical requirements of a marketable concentrate product. A typical daily met sheet recorded Fe:MgO ratios of 1.8 and 3.49 where a target of 5 was required. It also showed that 25 recovery struggled to meet modest targets and arsenic content was high. Efforts to address the problems were not greatly successful, as apparent in another note from 2006 citing "poor performance" which was attributed to "insufficient liberation" and also blamed on the use of an aged sample. For those particular tests (varying xanthate dosage rates at various stages) the 30 best, optimized recovery was 41 % with a 2.6% nickel grade. 3 2016204951 14M2016

Once there was no more massive Silver Swan ore with which to blend the Black Swan disseminated ore, within a month or so operations at Black Swan were terminated, leaving a quantity of unsaleable concentrate at the site

Lake Johnston is a nickel mine and concentrator plant located 110 km west 5 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 10 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). Its customer was Norilsk Nickel’s smelting refinery at the Haryavalta Nickel Plant in Finland to which concentrate was being shipped through the Port of 15 Esperance until around 2006 - 2007.

At that time LJO experienced difficulty with its product when the concentrate was unable to meet technical specifications and industry requirements relating to odour and dust suppression. Additionally, there arose questions about moisture content and self-heating which were unable to be 20 satisfactorily addressed. Later, its operators undertook extensive testwork on LJO ores in an attempt to improve the product quality. In 2011 and 2012, more than 30 flotation tests were made with various combinations and concentrations of guar, xanthates, DMDC, CMC, S8474, SIBX, CuS04 etc. at various pH levels. Recovery rates showed some improvement for certain 25 combinations but on the whole remained fairly unremarkable, and the operation continued to struggle with MgO levels and low recovery rates at around 65%. With the depletion of Emily Ann massive sulphides, production of smeltable grade concentrate could no longer be maintained and operations were halted. 30 The present applicant has no interest in re-starting previous operations with all their various problems and shortfalls, nor in attempting to produce a 2016204951 14 Μ 2016 4 concentrate product from these ore bodies for the same market. Instead, the aim is to assess the remaining nickel resources within these ore bodies with the aim of producing an entirely different non-smeltable nickel concentrate product for a uniquely different application. 5 The method of the invention is aimed at addressing the current limitations of the nickel-pig-iron (NPI) industry and their inability to produce stainless steels in the premium range of alloys, particularly those with higher than 12% nickel content. Blending or spiking NPI with a medium-grade nickel sulphide concentrate in a unique process may enable NPI producers to significantly 10 extend the range of steel products they can produce, provided that a suitable nickel sulphide product with consistent known characteristics can be designed using existing resources.

The present invention was developed with a view to providing a method of co-processing talc-bearing ores and serpentinite ores using a blend of Black 15 Swan and Lake Johnston ores to produce a nickel concentrate that meets its customer's specific metallurgical requirements for a foreseeable period of time. However it will be appreciated that the process may also applicable to other types of ore blends and is not necessarily limited to a blend of Black Swan and Lake Johnston ores. 20

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 25 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. 5 2016204951 14 Jul2016

Summary of the Invention

According to one aspect of the present invention there is provided a method of co-processing of nickel sulphide ores, the method comprising the steps of: transporting a first nickel sulphide ore comprising a disseminated sulphide 5 ore and talc-carbonate ore to a co-processing facility; transporting a second nickel sulphide ore comprising a disseminated sulphide ore to the co-processing facility; crushing and blending the first and second nickel sulphide ores to produce a blended ore having a desired mineralogy; and, 10 passing the blended ore through a flotation circuit to produce a nickel sulphide concentrate comprising at least 5% nickel.

Typically the second nickel sulphide ore comprises a disseminated sulphide ore blended with a specific amount of massive ores.

Typically the step of blending the first and second nickel sulphide ores is 15 performed by passing crushed ore through a milling circuit.

Preferably the method comprises the further step of conditioning the blended ore by passing it through a conditioning tank prior to the step of passing it through the flotation circuit.

Advantageously after the blending step and prior to the conditioning step the 20 blended ore is passed through a first cyclone classifier. Preferably the underflow from the first cyclone classifier is passed through a flash flotation process, and the concentrate from the flash flotation is sent to a thickener feed tank. Preferably the sinks from the flash flotation is passed through a regrind ball mill, and the milled output is sent to a second cyclone classifier. 25 The overflow from the second cyclone classifier is combined with the overflow from the first cyclone classifier and preferably passes through a series of trash screens before entering the conditioning tank. 2016204951 14 Μ 2016 6

Preferably the step of crushing the first and second nickel sulphide ores 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 the undersize ore from a first 5 crusher passes through a first screen to the milling circuit. Preferably the oversize ore from the first screen is sent to a second crusher, and the undersize ore from this second crusher passes through a second screen to the milling circuit. Preferably the oversize ore from the second screen is sent to a third crusher, and the undersize ore from this third crusher passes 10 through a third screen to the milling circuit, and the oversize ore from the third screen is sent back to the third crusher.

Typically the crushed ore from the crushing circuit is stockpiled and then passed through a primary ball mill in the milling circuit to produce the blended ore. In the described embodiment the co-processing facility is located at the 15 Lake Johnston operation (LJO), and the second nickel sulphide ore is a Lake Johnston disseminated ore. Preferably the second nickel sulphide ore comprises a Lake Johnston disseminated sulphide ore blended with a specific amount of massive ores from the LJO. 20

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 25 “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. 2016204951 14 Jul2016 7

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: 5 Figure 1 is processing plant flow diagram illustrating a preferred embodiment of the method of co-processing nickel sulphide ores according to the present invention.

Detailed Description of Preferred Embodiments 10 The ability to fine-tune ore feedstock through blending has previously been shown to have economic benefits both by influencing the product quality and by raising the overall recovery rate of nickel from extracted material. However, the ability to do so in the case of a blend of Black Swan and Lake Johnston ores was by no means assured, as evidenced by previous 15 operators' inability to do so, and by the main body of the nickel industry's focus on aggregate (massive) nickel sulphides for high-value nickel products or on low-value nickel laterites for other less-demanding applications.

The main purpose of the method of co-processing is to improve the quality and recovery from both the Lake Johnston operation (LJO) ores and the 20 Black Swan (BS) talc-carbonate ores. The method of the invention aims to achieve this through 1) blending ores from the two different sites, and 2) creating a customized concentrator flowsheet based on the constraints of existing facilities at LJO and BS. This also entails extending the areas accessed at LJO and altering the mining methods, which will have an as yet 25 undetermined effect on the flotation performance and characteristics of its output. Whether this could be done was by no means certain, as neither of these ores have been used for this purpose, and the application for the new concentrate is relatively new. 8 2016204951 14M2016

In order to develop the process it was necessary to characterize the ores fully, test blends of these ores to find out what grades and recovery rates were achievable, and to search for optimal flotation concentration process parameters that produce a marketable product. Ore sorting techniques will 5 also need to be evaluated to determine whether they are necessary or effective in meeting the product's technical requirements.

Many of the unknowns relating to the Black Swan ores, including ore types, mineralization, composition, and comminution properties have been addressed in previous R&D (see e.g. BSWAN - RD Plan Summary Rev 10 0.3.docx). The remaining Lake Johnston ores, on the other hand, remained relatively unknown and significant R&D work was required to understand these characteristics in order to prove the existence of BS-LJ ore blends that could meet specific requirements, and then to experimentally test these hypotheses in a mining trial. 15 The opportunity to produce a non-smeltable nickel concentrate that is not limited by Ni grade or by Fe:MgO ratio opens up the possibility that by maximizing the recovery rate at the expense of these unconstrained parameters, one may be able to turn a non-productive ore body into a productive one. In order to determine whether this can be done, the following 20 research and development program is being implemented: • Assay the remaining ores at the two sites to ascertain precisely what is there, with an emphasis not just on composition but on mineralogical structure as well, looking particularly at how these disseminated, often serpentinitic, talc-carbonate ores might behave in 25 flotation concentration treatment. • Pay particular attention to ores at LJO that may not have had much previous scrutiny, or sections of ore bodies that have only been newly opened or identified, since these could have an unknown effect on flotation characteristics. 30 · Consider how ore sorting technologies might be implemented to achieve the technical objectives. 9 2016204951 14 Jul2016 5 10 15 20 25 30 • Consider how measures to control iron reducing bacteria at LJO may have deleterious effects on the concentrator flowsheet and the end product, and what alternative measures may be devised. • Consider how changes to the ores removed at different times in the life of mine will affect the end product, particularly when blended from two different mines. In particular, the 1st year of operation may need to be considered separately from the years 2-4 output. • Consider how stockpiled ores may affect the process and final product, since these may in all likelihood be aged or oxidized differentially to freshly mined ores. • Propose an optimal blend, optimal flowsheet parameters, and an optimal treatment regime, and test these with appropriate samples. • Identify collector and frother agents and pH control that will have a selective influence on the nickel-bearing minerals of interest while rejecting non-nickel-bearing minerals such as talc which may have a flotation response. This is made more difficult by the need to blend ores from two distinct sources. • Determine how the iron chemistry in the slurry is influenced by and influences flotation chemistry, and how this interaction impacts rate of scale formation in flotation cells. • Based on the above, produce a laboratory-scale ore blend and flowsheet that shows potential for producing a suitable concentrate meeting the specified requirements. • Conduct a mini-plant-scale limited trial of approximately 3 - 4 weeks duration in order to test the proposed blend and flowsheet, and address remaining unknowns regarding ore dilution, grade, variability etc. that are dependent upon extraction technique, which must of course be adaptive to conditions as they occur. Such a limited trial should provide an adequate understanding of those factors, as well as be sufficient to definitively state the product's achievable specifications. 10 2016204951 14 M2016

Obtaining this new knowledge required ore sampling from a range of carefully chosen locations at both Black Swan and LJO, extensive laboratory testwork on the samples to test the variables listed above, leading up to a limited plant-scale trial to test the blend hypotheses formed during labwork. 5 Historic data from Black Swan showed that, on its own, the disseminated ore produced a poor grade of concentrate while leaving significant amounts of resource in the tailings. With the depletion of the Silver Swan massive or aggregated ore, the disseminated ore on its own is no longer a usable resource for the purpose of traditional smelting. 10 Whereas the old product required a high nickel content and a specific Fe:MgO ratio dictated by the metallurgical requirements of smelting, the new requirement is for a product with only moderate nickel content, but with specific proportions of Fe and S, as given below:

Ni >5% Fe 35% - 37% S 21% - 23% As 25 ppm TML 8%-10% 15 This is a relatively low grade concentrate which is suited to the mineralogy and composition of the Black Swan and Lake Johnston source ores. It is assumed that Sulfur will be a minimum value, and that more is better. There is no requirement set for the ratio of Fe:MgO. Also unknown (since the process is still brand-new) is whether As at higher levels will be problematic, 20 or whether the proposed threshold will be forced lower.

It is possible that the BS and LJO disseminated ores blended with a specific amount of massive ores from LJO may be able to meet these requirements while meeting the other technical requirements that are prerequisite for mining the ores, e.g. recovery rate and flotation performance. 11 2016204951 14 Jul2016

Communications with experts in mineralogy and ore processing make it clear that there are unknowns which cannot be established except by experiment. For example, the optimal composition of Black Swan and Lake Johnston blends could not be initially agreed because there was no basis upon which 5 to do so. Also, the amount of dilution from mining (and by extension the product grade and composition) would not be known until a full experimental mining trial could be conducted.

The previous operator of LJO experimented extensively with reagent selection for processing the SLC disseminated ore. The data show that MH 10 ores respond best to certain reagents and not to others. While this information is useful, it will have to be built upon and extended to apply to the new blends that can be anticipated from LJO, and of course the new requirements.

Most flotation processes are optimized to favour Ni grade while maintaining a 15 specific Fe:MgO ratio. This new concentrate product by contrast does not have a Fe:MgO requirement, nor is a higher Ni grade necessarily better. This means that much of what is known and understood about flotation processes for making standard concentrate is not relevant, and the parameters of this new process can at best only be inferred. 20 In addition, one can infer from the application that the new product may actually benefit from higher sulfur content. But this presents a potential problem, the magnitude of which is unknown. A concentrate high in sulfur may have a higher self-heating propensity that could influence how the product is prepared for transport, particularly the moisture level (TML), with 25 unknown follow-on effects on product performance. This too will need to be investigated as an unknown.

Finally, because the application for which the new concentrate product is intended is also new, it is unknown whether elements considered "deleterious" in traditional concentrate (such as arsenic) will also be found 30 deleterious to the new process. The customer also does not yet know this, and only experimentation will tell whether proposed As levels in the 12 2016204951 14 Jul2016 concentrate are acceptable, or whether the new flotation process will require additional modifications to produce a different As level. A preferred embodiment of the method of co-processing of nickel sulphide ores in accordance with the invention is illustrated in the flow diagram of 5 Figure 1 for a co-processing plant 10. The method typically comprises the step of transporting a first nickel sulphide ore comprising a disseminated sulphide ore and talc-carbonate ore to the co-processing plant 10. In the described embodiment the first nickel sulphide ore is a Black Swan disseminated ore. The method also comprises the step of transporting a 10 second nickel sulphide ore comprising a disseminated sulphide ore to the same co-processing plant 10. In the described embodiment the processing plant is located at the Lake Johnston operation (LJO), and the second nickel sulphide ore is a Lake Johnston disseminated ore. Typically the second nickel sulphide ore comprises a Lake Johnston disseminated sulphide ore 15 blended with a specific amount of massive ores from the LJO.

The method of co-processing comprises the further steps of crushing and blending the first and second nickel sulphide ores to produce a blended ore having a desired mineralogy. Typically the step of crushing the first and second nickel sulphide ores includes passing the ores through a crushing 20 circuit 12 comprising a plurality of crushers and screens. Preferably the crushing circuit 12 comprises three crushers 14 and screens 16 operating in series. The undersize ore from a first crusher 14a passes through a first screen 16a to a milling circuit 18. The oversize ore from the first screen 16a is sent to a second crusher 14b, and the undersize ore from this second 25 crusher 14b passes through a second screen 16b to the milling circuit 18. The oversize ore from the second screen 16b is sent to a third crusher 14c, and the undersize ore from this third crusher 14c passes through a third screen 16c to the milling circuit 18. The oversize ore from the third screen 16c is sent back to the third crusher 14c. 30 Typically the step of blending the first and second nickel sulphide ores is performed by passing the crushed ores through the milling circuit 18. The 13 2016204951 14 Jul2016 crushed ore from the crushing circuit 12 is stockpiled and then passed through a primary ball mill 20 in the milling circuit 18 to produce the blended ore. From the primary ball mill 20 the blended ore is passed through a first cyclone classifier 22. Preferably the underflow from the first cyclone classifier 5 22 is passed through a flash flotation tank 24, and the concentrate from the flash flotation tank 24 is sent to a thickener feed tank 60. Preferably the sinks from the flash flotation 24 is passed through a regrind ball mill 26, and the milled output from the regrind ball mill is sent to a second cyclone classifier 28. The overflow from the second cyclone classifier 28 is combined with the 10 overflow from the first cyclone classifier 22, and preferably passes through a series of trash screens 30 before entering a conditioning tank 32 for conditioning. The overflow from the trash screens 30 is sent to tailings.

Finally, the conditioned blended ore slurry, from the conditioning tank 32, passes to a flotation circuit 40. The blended ore is passed through the 15 flotation circuit 40 to produce a nickel sulphide concentrate comprising at least 5% nickel.

The flotation circuit 40 comprises a rougher flotation tank 42. The sinks from the rougher flotation tank 42 is sent to a series of three middling flotation tanks 44. The sinks from the middling flotation tanks 44 are sent to a series 20 of three scavenger flotation tanks 44, and the sinks from the scavenger flotation tanks are sent to tailings. The concentrate from both the middling flotation tanks 44 and the scavenger flotation tanks 46 are sent to a series of two cleaning flotation tanks 48a and 48b. The sinks from the first cleaner flotation tank 48a are sent to the second cleaner flotation tank 48b, and the 25 sinks from the second cleaner flotation tank 48b are sent to a series of three cleaning scavenger tanks 50. The concentrate from both the cleaning flotation tanks 48 is sent to the thickener feed tank 60. The concentrate from the cleaning scavenger tanks 50 is sent back to the rougher flotation tank 42. The sinks from the cleaning scavenger tanks 50 are sent to tailings. 30 From the thickener feed tank 60 the concentrate is sent to thickener 62, and then passed to a filter feed tank 64 before being filtered through filter 66. The 14 2016204951 14 Μ 2016 overflow from the filter 66 is returned to the thickener 62, and the underflow is sent to a concentrate stockpile.

The concentrate is typically a non-smeltable concentrate that allows the nickel recovery to be increased by over 10%. The non-smeltable concentrate 5 will be roasted to drive off the sulphur, and generate sulphuric acid that can then be used to pickle steel billets, generate electrical energy and produce a calcine that is blended with NPI to make high grade stainless steels. In this way, the process for recovery may be optimised as opposed to producing a high grade nickel concentrate with a high Fe to MgO ratio, and also for As 10 tolerance as the roaster drives off the As to produce a non-smeltable concentrate specifically for manufacture of lower-cost high-grade stainless steels from NPI.

As noted above, there were a number of unknowns which could not be established except by experiment. Below are detailed some of the 15 experiments conducted to establish key operating parameters of the preferred method of co-processing according to the invention:

Experiment: LJBS01

The objective of this experiment was to propose and test a hypothetical LJ-BS blend and a flowsheet theoretically capable of producing the new 20 concentrate, and to test the ore blend in laboratory flotation tests. To do this experiment, it was necessary to first determine grade, recovery rate and other metallurgical metrics of LJO ore concentrates under laboratory conditions with the following variables: • Ore origin 25 30 o SZvSLCvNS; o blended composites based on the above; o 1 st year ore versus years 2-4; o amount of dilution as influenced by mining technique and/or any ore sorting technique; • Reagent selection (PAX, SEX, SIBX or others) • Slurry pH (controlled via lime addition) • kinetics 15 2016204951 14 Jul2016

Once this was established and a LJ-BS blend proposed, flotation testwork on the blend was conducted to attempt to meet the product specifications.

It was anticipated that the unique proposed concentrate properties could be produced using a modified flotation process that focuses on recovery rate 5 rather than Ni grade or Fe:MgO ratio.

Method (Core R&D Activity):

Adequate samples from the specified ore zones were manually collected, diluted with simulated waste collected from the hangingwall or footwall as required, and a baseline flotation test and head assay was conducted. 10 Thereafter, samples were tested in batch and locked-cycle flotation under variable conditions of pH, reagent choice etc to test the response of grade, recovery, and technical metrics. Concentrates were assayed for grade, and tailings assayed for recovery rate. As variables (reagent choice and addition rates) were changed to maximize recovery, properties of the concentrate 15 were measured to determine its suitability as a non-smeltable product.

Similar test work on BSD ore was also undertaken, and the combined results used to propose a promising blend and flowsheet. Blended ores were then submitted for flotation tests using proposed flowsheet parameters.

This test work work was to determine whether the available ores and the 20 process plant might be able to produce the proposed product while providing the benefit of a maximized recovery rate. From this work it was hoped that a suitable ore blend could be proposed which will be tested and used in the next experiment to determine the optimal flowsheet parameters, reagents, kinetics etc. for maximum recovery. Thereafter, lab flotation tests on the 25 blends should validate the choice of blends and indicate whether plant-scale experiments would be useful.

Proposed ore blends:

The complex relationships between the various ores in the proposed blends based on origin and mineralogy is summarised below: 16 2016204951 14 Μ 2016

Black Swan composite • Black Swan blend is the original 70:30 blend combined with an extra BS Serpentine sample to reduce the amount to talc carbonate down to about 13%. The grade is estimated around 0.70% Ni so marginally 5 higher than the average stockpile blend. • Recipe = 20.0 kg (i.e. 2 kg of reserve from previous testing unless already blended) the ‘Black Swan Serp/Talc (70:30)’ + 12.7 kg of the ‘BS Serpentine (0535-003-SP6-DS1)’ 10 North Shoot • The LoM grade for the North Shoot is 1.255% Ni but the sample is 3.94% Ni. The MgO in the waste versus the ore is very similar, although the Fe is very different because of the mineralisation as there is no sulphide in the waste either. So for the North shoot it was 15 possible to justify blending all the waste into most of the ore sample to try and get a grade closer to the LoM. • Recipe = 20 kg of the ‘North Massive’ + all 10.5 kg of the ‘North Hanging Wall’ + 17.4 kg of the ‘North Foot Wall’. • This leaves 6.9 kg of the ‘North Massive’ for separate testing 20

Sub Level Cave • Based on the ratio of massive to disseminated in the resources, blend 25 5 parts disseminated to one part massive (called Sub Level Ore), then dilute by 25% with the waste. The nickel grade of 1.93% was still too high compared to the LoM of 1.07%, but the MgO is really high in the waste so don’t want to dilute it too much just to achieve the right grade. 30 · Recipe = all 14.9 kg of the‘Sub Level Disseminated’+ 3 kg of the‘Sub

Level Ore’ which is the massives + 4.5 kg of the ‘Sub Level Waste’. 17 2016204951 14 Μ 2016 • There will also be extra Sub Level Cave Massives (18.5 kg) left over to test separately

Suture Zone 5 · Can either blend it in the right ratio of mining dilution to reflect mining but this only gets 2.39% Ni. The MgO are similar, at the Fe:S ratio they are close enough and it is mineralised because of the 0.67% Ni in the ‘Waste’. So the best option is to blend the two together which will still end up with a grade of 1.86% Ni. This is a little high compared to 10 the LoM of 1.224% for the Suture Zone but the best achievable with the samples available. • Recipe = all 10.2 kg of the ‘Suture Ore’ + all 8.2 kg of the ‘Suture Waste’ 15 Maggie Hays Year 1-3 Composite • The main Maggie Hays Year 1 - 3 composite is a LoM comp 30% Suture Zone, 30% SLC and 40% North Shoot. Enough of the three components need to be left so that testing on those samples only can be done. 20

Maggie Hays Year 1 - 3 + Black Swan Composite • The LoM ratio is 65% Maggie Hays Year 1 - 3 composite and 35% Black Swan Composite. 25 The presence of a significant amount of non-sulphur nickel (NSNi) in some of the BS ores was a complication, and so will be left out initially, to be brought back into the equation later. The proposed blends were designed so that they can be processed together without deleterious effects on the product and while maximizing the recovery rate. 30

Findings of Experiment: 18 2016204951 14 Μ 2016

The results of flotation tests on the blends were somewhat surprising, since they produced rather higher Ni concentration than is required while achieving quite a respectable recovery rate of 92% of sulphide nickel. Even the Fe:MgO ratio exceeded the normal expectations for smeltable concentrate 5 with a value of around 9:1. Based on these preliminary results, it may be possible for these two previously non-productive ore bodies to be productive, not only in terms of the new non-smeltable concentrates but also for traditional smeltable concentrate. 10 Experiment: LJBS02

The objective of this experiment was to determine whether blended ores that are bulk mined and processed at plant-scale can produce concentrate that meets technical and mineralogical requirements for either non-smeltable concentrate or for traditional smeltable concentrate. This tests the 15 hypotheses formed through the lab work conducted in the previous experiment as well as addressing new unknowns related to scaling up.

Sampling techniques for labwork have known shortcomings that often do not reflect reality of bulk-mined minerals. Also, processes that work in bench-scale lab tests are not guaranteed to work on a plant-scale. The foregoing 20 lab work allows hypotheses to be formed about what blends and what flotation concentration processes may work, but it was not possible to say with confidence that these results are predictive of what will actually happen.

The possibility of producing a non-smeltable concentrate requires that a reasonable amount of concentrate be produced to demonstrate that 25 maximizing the recovery rate while relaxing other constraints has the expected effect. In so doing, a reasonable amount of non-smeltable product is made available for testing in the new steel-making process under development.

At the present time there are no plans to continue production after the 30 conclusion of the plant trial. 19 2016204951 14 Μ 2016

Plant-Scale Unknowns to be determined: • What is the rate of dilution with waste rock when bulk-mined, especially when bulk-mined using the novel application of air-legging being considered; 5 · What is the true mineral content of the dilution (may be different from the hand-picked simulated dilution of the previous experiment); • What effect does this actual dilution have on grade, recovery rate, and metallurgical specifications of the product? • What is the actual head composition and mineralization of bulk ore 10 and bulk blends compared to hand-picked samples of ores and ore blends used for the lab work? • Will the site water chemistry (estimated/simulated for lab tests) perform as predicted, or will it have an unanticipated effect on the product or process? 15 · Will the differences between the lab process and the plant process or limitations of the plant design create unanticipated effects on the product? • Will the plant process output consistency and reagent consumption be as seen in laboratory testing, or will unexpected technical issues affect 20 the product output?

It was anticipated that relaxing constraints on smeltable concentrate and maximizing recovery at a plant scale will produce a concentrate suitable for use as a non-smeltable product.

Method (Core R&D Activity):

25 The LJO concentrator plant will be set up specifically for this pilot run, with any necessary minor modifications needed to reproduce the laboratory flowsheet as closely as practical. Material will be removed from the LJO mine using mechanized methods wherever possible. BS material will be initially removed from the stockpile, and when depleted, mined from the BS 30 pit, and transported to LJO. 20 2016204951 14 Jul2016

The concentrator plant will be started first on a commissioning run to verify operation, and then on a continuous run producing about 4000 to 20,000 tonnes of concentrate in total. The concentrate is periodically assayed to determine Ni, S, Fe, As content and total moisture, and the results compared 5 to flowsheet parameters and to input material assays.

The purpose of this activity is to determine the remaining unknowns relating to using this ore blend in a non-smeltable product primarily, but may potentially also result in a smeltable product. This limited plant scale trial is not intended to transition into a production run. Instead, the plant will be shut 10 down after the amount of concentrate is produced that is required for customers' testing.

Now that a preferred embodiment of the method of co-processing 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: 15 (i) It enables a previously non-productive ore body to be turned into a productive one. (ii) It facilitates the processing of an entirely different non-smeltable nickel concentrate product for a uniquely different application. (iii) It addresses the current limitations of the nickel-pig-iron (NPI) industry 20 and their inability to produce stainless steels in the premium range of alloys, particularly those with higher than 12% nickel content.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing 25 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 co-processing of nickel sulphide ores, the method comprising the steps of: transporting a first nickel sulphide ore comprising a disseminated sulphide ore and talc-carbonate ore to a co-processing facility; transporting a second nickel sulphide ore comprising a disseminated sulphide ore to the co-processing facility; crushing and blending the first and second nickel sulphide ores to produce a blended ore having a desired mineralogy; and, passing the blended ore through a flotation circuit to produce a nickel sulphide concentrate comprising at least 5% nickel.
2. A method of co-processing of nickel sulphide ores as defined in claim 1, wherein the second nickel sulphide ore comprises a disseminated sulphide ore blended with a specific amount of massive ores.
3. A method of co-processing of nickel sulphide ores as defined in claim 1, wherein the step of blending the first and second nickel sulphide ores is performed by passing crushed ore through a milling circuit.
4. A method of co-processing of nickel sulphide ores as defined in claim 1, further comprising the step of conditioning the blended ore by passing it through a conditioning tank prior to the step of passing it through the flotation circuit.
5. A method of co-processing of nickel sulphide ores as defined in claim 1, wherein after the blending step and prior to the conditioning step the blended ore is passed through a first cyclone classifier.
6. A method of co-processing of nickel sulphide ores as defined in claim 5, wherein the underflow from the first cyclone classifier is passed through a flash flotation process, and the concentrate from the flash flotation is sent to a thickener feed tank.
7. A method of co-processing of nickel sulphide ores as defined in claim 6, wherein the sinks from the flash flotation is passed through a regrind ball mill, and the milled output is sent to a second cyclone classifier.
8. A method of co-processing of nickel sulphide ores as defined in claim 7, wherein the overflow from the second cyclone classifier is combined with the overflow from the first cyclone classifier and passes through a series of trash screens before entering the conditioning tank.
9. A method of co-processing of nickel sulphide ores as defined in claim 3, wherein the step of crushing the first and second nickel sulphide ores includes passing the ores through a crushing circuit comprising a plurality of crushers and screens.
10. A method of co-processing of nickel sulphide ores as defined in claim 9, wherein the crushing circuit comprises three crushers and screens operating in series.
11. A method of co-processing of nickel sulphide ores as defined in claim 10, wherein the undersize ore from a first crusher passes through a first screen to the milling circuit.
12. A method of co-processing of nickel sulphide ores as defined in claim 11, wherein the oversize ore from the first screen is sent to a second crusher, and the undersize ore from this second crusher passes through a second screen to the milling circuit.
13. A method of co-processing of nickel sulphide ores as defined in claim 12, wherein the oversize ore from the second screen is sent to a third crusher, and the undersize ore from this third crusher passes through a third screen to the milling circuit, and the oversize ore from the third screen is sent back to the third crusher.
14. A method of co-processing of nickel sulphide ores as defined in claim 9, wherein the crushed ore from the crushing circuit is stockpiled and then passed through a primary ball mill in the milling circuit to produce the blended ore.
15. A method of co-processing of nickel sulphide ores as defined in claim 1, wherein the co-processing facility is located at the Lake Johnston operation (LJO), and the second nickel sulphide ore is a Lake Johnston disseminated ore.
16. A method of co-processing of nickel sulphide ores as defined in claim 15, wherein the second nickel sulphide ore comprises a Lake Johnston disseminated sulphide ore blended with a specific amount of massive ores from the LJO.