WO2021038449A2

WO2021038449A2 - Sulphide concentrator plant

Info

Publication number: WO2021038449A2
Application number: PCT/IB2020/057949
Authority: WO
Inventors: Anthony Owen FILMER; Daniel John ALEXANDER (Deceased)
Original assignee: Anglo American Technical & Sustainability Services Ltd; PIENAAR, Danie
Priority date: 2019-08-26
Filing date: 2020-08-26
Publication date: 2021-03-04
Also published as: WO2021038449A3

Abstract

This invention relates to a method of treating sulphide ore in a standard design sulphide concentrator plant, the plant comprising: one or more ore crushing standard design unit/s; a primary gangue rejection section comprising: one or more bulk sorting standard design unit/s; and one or more screening standard design unit/s; one or more tertiary crushing standard design unit/s; a secondary gangue rejection section comprising: one or more modular ore classification standard design unit/s; one or more modular coarse flotation standard design unit/s; and one or more modular fine flotation standard design unit/s.

Description

SULPHIDE CONCENTRATOR PLANT

BACKGROUND TO THE INVENTION The time between discovery of an orebody and first production, even for a world class resource, is typically around 15 years. This is largely due to the bespoke nature of design of each processing facility. This bespoke design is required to take full advantage of the specific resource, but the bespoke design causes an extended iterative cycle between increasing knowledge of the mineral resource and the design of an optimised concentrator and residue management facility.

This is particularly true for sulphide concentrators, where the processing plant is usually the largest part of the project expenditure, and concentrator designs are all unique.

The bespoke design of the conventional sulphide concentrator is critical to progressing the project as it also defines the requirements for residue management, the site infrastructure such as power and water, the environmental impact and the mine plan. Hence delays with the evolving design of the concentrator delay the application for the permits required to commence construction. In manyjurisdictions, a prefeasibility level study of the bespoke design is required before permitting is considered.

Changes to any input in this iterative circle, such as additional information on the mineral resource, or specific requirements from the various stakeholders, or the need to achieve a higher financial return, all require a re-optimisation of the bespoke concentrator with consequences for all other components of the project.

The sequence of resource development illustrating the bespoke design and some of the iterative loops that arise, is shown in Figure 1 . The bespoke design process of a plant is shown by numeral 10. This involves exploration 12, followed by feasibility assessment 14, project scope changes 16 to meet community concerns, Government approval, company board approval 20 to proceed (major permits) and detailed engineering 22. This is followed by construction 24, project scope changes 26, Government permitting and community consultation 28, and commissioning and operation 30. In manufacturing industries, a quite a different design philosophy is evident. The iterative cycle associated with bespoke design is avoided by standardizing the plant design.

The manufacturing industry has the benefit of the same input materials, and hence the same equipment, same layout, and same infrastructure are used in a standardized design of plant and equipment. This standardised manufacturing design can be used in most locations. The only bespoke parts of design for manufacturing become the building in which the plant is located, and tie-ins to local infrastructure. Because the standard plant for the manufacturing industry effectively has equal functionality in any location, it can be built much faster and at a much lower cost.

However, attempts to translate this design philosophy from the manufacturing industry to the mining industry have always proved counterproductive. This is due to every new project in the mining industry having considerable variation both between different ore resources, and different mine locations. The inherent variation of input ores from different mines is quite unlike manufacturing.

Every mine, and even zones of ore accessible during the life of mine, has a different grade of the mineral of interest, and these patches exhibit different properties as they are processed. For example, copper grades in new mines under development can vary from around 0.5% to 2% Cu; the throughput capacity to optimise the specific resource can vary from say 30ktpd to 200ktpd; the mill throughput of a hard ore can be 30% less than a softer ore; whilst the flotation recovery at a given grind size can vary from 80 to 95% depending on ore mineralogy.

This ore variability has significant implications for conventional concentrator design, which seeks to optimise the throughput capacity of each unit operation over the full range of ore types during the life of the mine.

So, whilst the concept of a standard sulphide concentrator has been discussed by industry suppliers, it has never progressed to commercial reality due to the inefficiencies arising from this ore resource variation.

The physical location of the mine can also have a large effect on design. In addition to matters of regulatory conditions in the country where the project is related, in some locations water is scarce, in others the terrain is difficult for residue storage, and in others the power load is well in excess of what can be obtained from the local electricity grid. Because the size of the mine is usually large, these locational factors will affect the choices of equipment.

Hence the concept of a standard concentrator has been largely abandonned by the mining industry due to the variability in both the orebody and the different design constraints faced by each project

The usual method for the bespoke design of a sulphide concentrator is to ascertain the magnitude of the available resource, define a scale of production that suits the known constraints of the mine (e.g. resource size, available infrastructure, or available capital), then undertake a drilling campaign to characterize the resource, and testing of this resource to determine its upgrade characteristics throughout the life of mine, and then undertake an engineering feasibility study.

This study typically:

• develops a mine plan to deliver the best available grade and ore characteristics;

• then taking into account the laboratory trials, sequentially defines the throughput capacity required in each step of the concentrator flowsheet and the mass flows that require transfer within the flowsheet;

• then selects the equipment best suited for processing the particular resource at the calculated capacity,

• then optimises the material flows within the sulphide concentrator to fit the assumed ore resource.

This multi-step process iterates back and forward to determine ways that the mine can be designed to provide a suitable feed for the evolving options for concentrator design. At this stage, a cost estimate for the mine and the processing facility can be developed, which usually then leads to a new round of optimization to best utilize the resource. This in turn, often leads to a further definition of the available resource to generate and acceptable rate of return and to optimize the whole system.

The only degree of freedom available to the designer, to change the nature of the ore feed using this approach to bespoke design, is to utilize grade control procedures in the mine to balance flows between the mine and the processing facility. For particularly large and high-grade resources this sometimes provides the flexibility to stockpile lower grades of ore during the early phase of mine life. If stored appropriately this marginal ore can be utilized later in the mine life when the higher- grade ore is exhausted. But for most projects, the mine plan simply allocates the highest available grade of ore, in an acceptable digging sequence, to the best available concentrator design.

Once a reasonable view of the design of the likely mine and processing facility has been developed, the permitting of the mine can commence, usually triggering a fresh set of constraints, that start another phase of iteration around the bespoke design of the sulphide concentrator.

And finally, as more information becomes available in the iterations described above, the interactions with the local community continue to evolve. For example, the amount of water or power required for mine operation is roughly proportional to the selected throughput of the processing facility. These evolving community impacts can often lead to a reconsideration of the overall mine design, as issues around competition for local resources and the interface of the mine with the local community become more apparent.

The number of interconnected moving parts in this overall optimization, the bespoke design of each equipment, and the uncertainty around the anticipated mineral resource, result in extensive delays and engineering rework to find the optimum business case.

The result from this process is the extended timeline, and that no two mineral processing facilities are the same. Whilst it is well known that a standard design for a mine and processing plant, akin to that used by the manufacturing sector, would eliminate much of the rework in the iterative cycle, the differences in ores and location cause the alternative approach.

When optimizing the effectiveness of a whole system in a capital-intensive business, a key factor is to ensure the feed and product flows to and from the most capital- intensive part of the system do not impede its operation. The nature of mineral processing is such that comminution is much more capital intensive than the subsequent flotation. Hence the throughput rate or tempo of the processing facility is set by the ore comminution assets. Conventionally, these individual equipment units include the tertiary crushers like the SAG or HPGR mills, and ball mills. They are designed with very few units of the maximum possible size. The remainder of the equipment in a sulphide flotation flowsheet is essentially modular, where multiple units of uniform size are matched to the throughput capacity of the tertiary crusher.

Examples are cyclones, flotation machines, and filters. The scale of these units is much less critical to the overall capital investment. Hence conventional bespoke design selects the number and size of such units such that they maximise recovery without inhibiting the throughput of the comminution.

It is an object of this invention to provide a simplified and standard concentrator design and method of operation, that can be applied to most mines even when limited information is available about the orebody and the range of characteristics of the ore; without any significant downside in recovery or overspend on capital. Through the invention, the time and cost of project development can be significantly reduced.

SUMMARY OF THE INVENTION

THIS INVENTION relates to a method treating sulphide ore in a standard design sulphide concentrator plant, the plant comprising a primary gangue rejection section comprising:

• ore crushing standard design unit/s

• gangue rejection standard design unit/s wherein the number of each standard gangue rejection units is selected for early operations, with the flexibility to add further modular standard gangue rejection unit/s to the initial design to reprocess a fraction of the marginal ore that may have been rejected during these early operations.

The standard gangue rejection unit/s all have the characteristic that they can be readily adjusted to operate at different points on their grade recovery curve, to enable rejection of the waste and/or the lowest value ore, to match the design throughput capacity of the selected number of the standard gangue rejection unit/s.

In so doing, the throughput tempo of production is set by the ore tertiary crushing standard design unit/s. Providing the lowest value ore that is rejected is free draining, it can be readily stored for processing later in the mine life. Any loss of recovery or throughput caused by the initial selection of the number of gangue rejection modules can be re-captured later, either towards the end of the ore resource, or when an further standard design unit is added to accommodate the evolving nature of the ore.

The primary gangue rejection standard units located prior to the tertiary ore crushing, each of which can reject gangue across a wide range of the grade recovery curve, are:

• bulk ore sorting

• rock screening

A secondary gangue rejection section comprises modular gangue rejection standard units located subsequent to the tertiary ore crushing, for each of which the feed particle size can be controlled to balance throughput and recovery, are:

• particle size classifiers, with the option of either stockpiling or heap leaching of an ore fraction

• coarse particle flotation machines

• conventional flotation machine.

Preferably, the standard design tertiary crusher is designed to operate in closed circuit mode, such that oversize particles from downstream particle size classification can be recycled to further tertiary crushing, such as to maximise value from the standard concentrator design.

The standard design bulk sorting unit/s, rock screening unit/s, sand classification unit/s, and coarse flotation unit/s are all operated to reject gangue and / or low grade ore, to match the capacity of the tertiary crushing with the capacity of the subsequent processing steps, and maximise recovered value from the available ore.

The standard design includes a layout such that additional modular units of one or more of the gangue rejection units can be readily incorporated after the start-up of the standard plant.

If for example the mine grade were to increase during the life of mine, such that the grade and quantity rejected from any stage in the gangue rejection system justifies earlier processing of this reject, additional standard modular units can be installed downstream of the tertiary crusher. Low grade ore and/or gangue, which in the CTM configuration are of a size that is free draining, and hence may be rejected to a stockpile or stockpiles, without the need for specific containment. The reject fraction may either be as waste, or as marginal ore for reprocessing later in the mine life.

For those ores which are amenable to heap leaching, such as gold, secondary sulphide, and some nickel, primary copper, and zinc ores; the free draining reject from any one or more of the standard gangue rejection unit/s can be further processed by heap leaching, as an alternative to stockpiling and reprocessing later in the mine life.

Through using this standard concentrator design, the amount of orebody knowledge required prior to commitment to proceed is greatly reduced, accelerating the project. And the equipment selection and layout is very similar for all orebodies of a similar grade, eliminating most of the bespoke engineering design.

As the mine expands, the plant design may be replicated in parallel standard design units to match the processing capacity with the ultimate mine capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a simplified schematic of a known iterative pathway to develop a new mineral resource;

Figure 2 is a simplified schematic of a CTM operation according an embodiment of the invention;

Figure 3 is a graph showing how throughputs can be balanced by gangue rejection without major economic consequence.

DETAILED DESCRIPTION OF THE INVENTION

In recent years, several developments have occurred which allow gangue or low grade ore to be rejected earlier in the mining and processing chain. For base metal sulphides, these developments include such technologies as bulk sorting, screening and coarse particle flotation (WO 2018/234855, the content of which is incorporated herein by reference). These gangue rejection technologies, also termed concentrating the mine (CTM) technologies, enable dry storage of tailings (WO2016/170437, WO2017/195008, the content of which is incorporated herein by reference).

Application of these CTM technologies can reject a low-grade fraction of the ore, enabling higher-grade ore to be processed at subsequent steps in the processing chain. Each CTM technology has a grade vs. recovery curve which is dependent on the mineralisation in a specific ore resource.

The grade recovery curve for bulk ore sorting is dependent on the natural heterogeneity in the geological formation of the orebody. By selecting a particular grade for acceptance and reject by the bulk sorter, the throughput allocation between product proceeding directly to tertiary crushing, and reject assigned to a stockpile, can be adjusted.

The optimum setting on the grade recovery curve for bulk ore sorting can be selected to prepare the reject fraction of the ore for subsequent screening. Screening of a low-grade ore fraction can take advantage of the differential fracture that occurs during blasting and primary crushing, in which a higher proportion of the sulphides present in the ore will report to the fines. The differential deportment is dependent on the specific ore mineralogy. The proportion of the finer high-grade ore to be reincorporated in the ore stream proceeding to tertiary crushing, i.e. the location of the screening grade recovery curve, can be intermittently adjusted by selection of an alternative screen size.

For ore resources that are of a size to justify a plurality of tertiary crushers, the bulk sorter can also be configured to split the ore into separate high-grade and low-grade streams to feed the different tertiary crushers, in addition to the stream for scavenging by screening. This configuration is useful when ore separated downstream of the tertiary crusher will be stockpiled for recovery later in the mine life, such that value forgone in this stockpile is further minimised. Processing the fines fraction from screening provides additional ore which is already sized suitably for further processing and hence increases the throughput capacity of the tertiary crushing.

These two gangue rejection techniques are integrated to allow the highest value ore available from mining to be directed to tertiary crushing, to fill the maximum throughput capacity of the tertiary crusher, thus ensuring maximum value progressing to processing. Hence, the maximum value of the mined resource can be captured for processing, without specifically integrating the mine design to fit that of the comminution throughput capacity.

Consistent with industry practice, the standard tertiary crushing unit/s can for example either be high pressure grinding rolls (HPGR), or a semi-autogenous grinding mill (SAG) supplemented by pebble crushing.

Downstream of the tertiary crushing, the ore is classified using a standard classification unit/s into four size ranges suited to stockpiling/heap leaching, coarse particle flotation, and conventional flotation, with the classification oversize recycled to the tertiary crushing.

The differential minerals fracture during comminution causes the coarser sizes to be at lower grade than the finer sizes, and in particular than the fine size range allocated to conventional flotation.

The standard classification unit/s can be adjusted intermittently to change the p50 split size. For example, a screen size can be changed, or the operating settings of a cyclone can be changed. In so doing, this changes the mass split of ore between the size ranges best suited for conventional flotation, coarse flotation, free draining stockpile or heap leach, and recycle to the tertiary crushing.

The nature of the specific ore to be processed by the standard plant will dictate the optimum value generated by each of the different processing routes, and each of these processing equipment in the standard plant will have a maximum design throughput rate.

Changing the classification size allows for operation of each processing route within the maximum throughput rate of each installed equipment, whilst optimizing the value of directing ore of a particular size to one gangue rejection technique or another. Thus the processing rate is matched to the production rate of the tertiary crusher.

In the event of the selected number of modules installed in the standard design being lower than ideal for the ore, the recovery may be slightly lower than optimum, but the reject from this suboptimum recovery can be stored for later processing.

Hence, even if the initial estimate of desired number of modules for conventional flotation and coarse flotation is under-estimated, the loss of value is modest. Once the ideal configuration is evident from early operations, the number of modules of one or more of the processing routes (flotation, coarse flotation, or heap leaching) can be increased to match the evolving knowledge of the orebody.

These gangue rejection (CTM) technologies, as configured in the standard plant, are attractive because not all fractions of the ore as mined, and at each particle size generated in the ore comminution, are of equivalent value.

The cost of most unit operations is related to the wear on equipment, the labour to operate the equipment, and the consumables required to convert the tonnes of ore to concentrate product. Hence, the overall operating cost is almost proportional to the equipment throughput.

For conventional bespoke design, the costs are particularly dependent on the number of tonnes ground to a fine size to fully liberate the valuable grains of product mineral.

The revenue contributed by the throughput from each piece of equipment is related primarily to the grade of the valuable mineral contained in the tonnes of rock processed. Thus, high grade fractions within any parcel of ore are extremely value accretive in processing, whereas the low-grade fractions are of somewhat marginal value when considered in terms of incremental revenue vs. incremental processing costs, or even value destructive when processed.

The CTM technologies remove the lower-grade ore fractions with very modest contained value, thus assigning the remaining higher-grade and highly value accretive feed to fill the subsequent equipment in the processing chain. The case for removing value destructive fractions of ore using the CTM gangue rejection technologies, is readily apparent.

Removal of low-grade fractions of ore, even if they would have been slightly value accretive, represents only a marginal decrease in value from the ore. And when removed prior to the system throughput bottleneck, they open capacity for alternative higher-grade ore feeds to be processed, hence filling all the downstream processing capacity with higher-grade ore streams, which is highly value accretive.

The CTM technologies also enable the throughput of value through the downstream processing to be increased, by controlling the grade, size, recovery, relationship to maintain full utilization of downstream installed capacity. If in some cases, the recovery by a particular processing technique is not optimum, the extent of loss is minimal.

In effect, the ore has been modified to fit the throughput of the installed capacity of the standard plant, rather than the bespoke plant designed such that each equipment capacity meets the characteristics of the ore.

Even when the orebody proves to be significantly different than the initially selected number of processing modules, the stockpiled low-grade material rejected by the CTM technologies can be reclaimed for processing when additional modules are added or later in the mine life.

The present invention relates to a- Standard Design of Sulphide Concentrator using Gangue Rejection.

The normal use of CTM technologies is to optimise the waste rejected, to reduce the comminution costs in the bespoke design of a sulphide concentrator.

This invention provides an alternative approach to utilize CTM technologies to enable a standard design of sulphide concentrator that can efficiently process most sulphide ore resources and is applicable in many different mine locations.

By “standard design”, it is meant a standard set of unit operations, with a standard size of each modular equipment in a sulphide concentrator, preferably arranged in a standard layout i.e. in a similar fashion to the standard design used for manufacturing plants. A block flowsheet illustrating the principles underpinning the standard concentrator design is illustrated schematically in Figure 2. With reference to Figure 2, ore from a mine 32 is passed through a series of standard units:

• a crusher unit 34,

• a primary gangue rejection section comprising a bulk sorter unit 36 and a screen unit 37,

• a tertiary crusher unit 38,

• a classifier unit 40, and

• a secondary gangue rejection section comprising a coarse particle flotation unit 42, a regrinder 44, a conventional flotation unit 46, and filter 48.

In accordance with the method of this invention ore I crushed in the crusher unit to a size of <500mm and passed through the bulk sorter unit 36. A waste stream 50 from the bulk sorter is directed to a waste rock pile, and a sorted stream 54 is directed to the classifier 40. A stream of marginal grade ore 56 is screened 37 and a stream of the higher grade fines from screening 60 is passed to the tertiary crusher 38, and waste stream 62 is stacked and stored 64 for later life or in a heap 66 for heap leaching. The tertiary crusher crushes the ore to a size less than 5mm. A coarse fraction 68, typically with a particle size greater than 150pm and typically less than 500 pm, from the classifier 40 is sent to the coarse particle flotation unit 42, and a fine fraction 70, with a particle size typically less than 150pm, is sent to the conventional flotation unit 46. The coarsest ore with size above around 500 pm is assigned to heap leach. An intermediate concentrate 72 from the coarse particle flotation unit 42 is ground in the regrinder 44 to a particle size of 150pm, and fine concentrate 74, with a particle size of 150 pm, is passed to the conventional flotation unit 46. Concentrate 76 is sent to the filter 48, and tailings are stacked 80. The bulk sorter 36 and screen 37 select the best available feed for optimum SAG capacity by rejecting marginal ore which is stockpiled. The classifier 40 selects optimum size ranges for a particular ore to balance throughput and optimise recovery across the downstream processing units. The demand for supporting infrastructure such as “water and power” reflected in Figure 2, will be affected by the size splits, and if they form a constraint in the application of the standard plant, size selections can be adapted to minimise the initial loss of value.

The core of any conventional sulphide concentrator is the milling section, which usually comprises tertiary crushing equipment such as HPGR or SAG mills, followed by ball mills. Gangue and values are liberated for subsequent separation by flotation . The capital intensity of this milling process demands large equipment to capture the economies of scale. The capital and operating cost of milling increase substantively, the finer the selected grind size.

In the bespoke design, these milling units set the throughput constraint or bottleneck for preceding mining and primary crushing capacities and set the subsequent throughput capacities required of the flotation equipment. The number and size of the mills is selected to suit the known size of the resource; and then mine design is adapted to provide the highest available grade of ore to this comminution equipment.

Depending on the characteristics of the ore derived from test work on a variety of ore samples from the resource, the downstream design is then sized to fit the anticipated mill throughput capacity.

For the standard sulphide concentrator that is the subject of this invention , a standard tertiary crushing unit, preferably operating in recirculating mode, also forms the throughput bottleneck.

Gangue rejection to waste or a low-grade stockpile takes place prior to this tertiary crusher, which forms the design bottleneck. Mined ore is crushed, bulk sorted to eliminate gangue, and some or all of the bulk sorter reject is screened to allocate the higher-grade fines for further processing.

Rejecting these gangue rich fractions upstream of the standard tertiary crushing enables the highest value fractions of the mined ore to fill the standard tertiary crusher unit/s, and the rejected gangue to be assigned to either waste or a marginal ore stockpile. The mining rate can vary without slowing the tertiary crusher, and without storage of large quantities of RoM ore to buffer flows between mine and mill. Within the material selected by grade control processes as run of mine (RoM) ore, there are waste fractions where the revenue arising from that fraction is less than the cost of processing. Using the standard plant design, this waste material can be separated by the bulk sorter and discarded prior to the tertiary crusher. The rejection of waste adds direct value to the standard plant, as illustrated in region C in Figure 3. There are also marginal grade fractions of the RoM ore region D in Figure 3, where the revenue marginally exceeds the cost of processing. Given that the mining cost for this fraction has already been incurred, processing this fraction will generate a positive economic margin. But if this fraction uses tertiary crushing and processing asset capacity that could yield a slightly higher margin if the facility was fed with fresh higher-grade ore, despite the extra mining costs required to generate this fresh ore. Through application of CTM, the invention makes the assignment of some or most of this fraction to a marginal ore stockpile to balance the available downstream capacity in the standard plant. This is also illustrated schematically in Figure 3, in which:

A - is the revenue from processing,

B - is the processing costs,

C - is the value destructive fraction as processing costs exceed revenue (assigned to waste),

D - is the marginally value accretive ore fraction in subsequent processing (assigned to processing only if spare capacity is available, otherwise sent to low grade stockpile, and

E - is the highly value accretive ore fraction where revenue exceeds total costs (assigned to processing)

As explained previously, the classification immediately downstream from the tertiary crusher enables a balancing between installed processing capacity and values recovery for the particular ore type.

It is also evident from Figure 2, that the standard plant does not require a ball mill. The range and flexibility of particle sizes provided for by the downstream recovery options, implies that fine milling of the run-of-mine ore to fully liberate the valuable mineral grains is no longer essential. Whilst the fraction assigned between the different processing routes and recirculating to the tertiary crusher will vary by commodity and orebody, fine milling of all the run-of-mine ore is eliminated.

The fines fraction 54 arising from tertiary crushing 38 is classified into four size fractions. Due to differential fracture during tertiary crushing, the finest fraction 70 is typically of a higher grade than the remaining ore. This fine fraction 70, typically less than around 150 microns depending on available conventional flotation capacity, is classified and assigned directly to the subsequent standard flotation roughers 46. The product of the tertiary crushing is further classified to yield two slightly larger ore fractions suitable for coarse particle flotation 42 and heap leaching 66.

Coarse particle flotation 42 when utilized over a limited size range, typically 150 to around 400 microns, produces a sand residue which would be value destructive to mill further to liberate and recover any additional values. This residue is discarded as waste. The intermediate concentrate 72 from the standard CPF unit/s, typically around 20% of the feed tonnage, is reground 44 to a size suited for high flotation recoveries and grade. Volumes of this stream are modest, hence over-design of the standard re-grind mill to accommodate the possible ranges of required capacity, ultimately depending on classification settings, is not of economic concern in the initial standard design.

Coarse particle flotation 42 can also operate with different control settings at rates above design capacity, albeit with loss of recovery. In the event that less than ideal capacity of flotation capacity is installed, the coarse particle flotation feed rate can be increased significantly by increasing the cut size in classification. The coarse flotation residue is no longer suitable for direct discard; but is free draining and able to be stored. In this way, the delay of value from the initial RoM is further minimised.

During tertiary crushing 38, some of the output particle size distribution may be too coarse for high recovery in subsequent processing. For example, if the tertiary crusher is a SAG mill, pebbles will build up. Conventionally, these pebbles require removal from the SAG and supplementary pebble crushing. In this case when the value of this stream is greater than the available RoM, the pebbles require supplementary crushing prior to being recirculated to the tertiary crusher. If, however, the pebble value is low they can be stockpiled for processing later in the mine life.

The coarsest classification size is typically recycled to the tertiary crushing.

In summary the ore is adapted to fit the standard concentrator, rather than a bespoke concentrator being designed to fit the ore.

The levels of bespoke infrastructure to support the standard sulphide concentrator are also significantly reduced by gangue rejection but remain somewhat dependent on location. Total electrical power consumption of the processing facility per unit of production is reduced and set by the size of the standard milling device. The coarser size of waste allows for lower water consumption. The much lower levels of power, water and tailings all contribute to the effectiveness of a standard concentrator design, due to reduced levels of bespoke infrastructure to support the mine.

In effect, the use of CTM technologies configured in a standard plant design has enabled maximum revenue to be achieved from the available resource, by allocating the highest margin ore through the system bottleneck, without the requirement for high cost and time-consuming bespoke design of the sulphide concentrator. By putting aside different ore fractions (rock and sand) that would only have been of marginal value, the standard design allows mining and processing throughputs to be optimized for the particular ore resource, and the throughputs of each major class of equipment balanced.

Space is made available in the layout of the standard design to add pebble crushing, flotation cells, and concentrate filters, either during or after the construction and commissioning of the standard plant. In this way initial operations can be established, and if the ore warrants additional bespoke components, these can be easily integrated.

Multiplication of the Standard Design Concentrator Modules

If the resource size warrants a larger throughput than possible through a single standard design, the investment can be replicated in its standard design based around the standard tertiary crushing throughput capacity.

Thus, the one mine will feed multiple standard concentrators. And each line in turn will utilize a common set of stockpiles for waste, low margin ore, and final concentrate.

And within this standard design, the units or modules of equipment post tertiary crushing, such as coarse flotation or flotation machines, can be increased to accommodate very high-grade ores.

This approach implies that the bespoke nature of design for the mine is limited to the elements of mine design, geotechnical considerations for the plant location and foundations, and associated infrastructure such as residue disposal, water and power, and access roads.

The benefits of standard design

The first benefit of standard design is shortening the cycle time from finding a resource to full production. The contributing components of this foreshortening include: less orebody characterization, early commitment to the project, faster permitting, faster process design, improved procurement, and faster construction, commissioning and ramp up.

Orebody characterization typically requires extensive drilling to gather samples for metallurgical testing to develop mass balances under a variety of geo-metallurgical scenarios. The ability to control mass flows through use of bulk sorting and coarse flotation, means the standard sulphide concentrator can manage a much wider range of feeds. The ore characterization for standard plant is limited to ensuring the resource does not require any additional units to supplement the standard design.

Earlier commitment to the project is possible, because the resource only has to be of sufficient size to justify the first standard plant. Parallel standard plants can be added later, as the full extent of the resource is established, and the nature of the ore is better understood. Additionally, the standard plant enables a much more accurate cost estimate of the project early in the development cycle, thus avoiding the iterative cycle of seeking extra resource or high-grade ore zones to justify a project once the cost structure is known.

Permitting is faster, as the design of the plant and tailings disposal are known very early in the project, allowing authorities to focus on the impact of the mine and processing facility in the specific environment. The impact on local water and power systems is also much reduced relative to a conventional bespoke processing facility. Similarly, the ability to demonstrate an identical concentrator operating elsewhere, will assist in eliminating mis-understandings during community consultation.

The design of the concentrator is substantially foreshortened, as only the interfaces specific to the mine location need to be addressed. Procurement of equipment and material transfer within the boundary limits of the standard concentrator do not require any time-consuming retooling by the manufacturers and are ideally suited for rapid modular construction. Scheduling and procedures for construction within the boundary limits of the standard concentrator can standardised, with significant implications for construction productivity.

Similarly, commissioning and ramp up procedures can be standardised to reduce rework. And the lower breakeven grade of ore to the plant arising from the gangue rejection technologies enables early commissioning of the plant, using mined pre strip material that would conventionally be considered waste.

The second benefit of standard design is lower cost.

In addition to the benefits arising from CTM such as lower grinding costs and higher- grade ores being processed, all the contributing benefits in terms of schedule, also reduce engineering hours and avoid costly rework. Procurement of many units of standard equipment also enables cost reductions in the equipment manufacture.

The third benefit of the standard design is ongoing flexibility to manage the variation inherent in the orebody, by ensuring the profit margin through the system bottleneck is maximised, up until the replication of the standard design is warranted.

Claims

1 . A method of treating sulphide ore in a standard design sulphide concentrator plant, the plant comprising:

• one or more ore crushing standard design unit/s;

• a primary gangue rejection section comprising: o one or more bulk sorting standard design unit/s; and o one or more screening standard design unit/s;

• one or more tertiary crushing standard design unit/s;

• a secondary gangue rejection section comprising : o one or more modular ore classification standard design unit/s; o one or more modular coarse flotation standard design unit/s; and o one or more modular fine flotation standard design unit/s; wherein the standard design bulk sorting unit/s and screening unit/s in the primary gangue rejection section are operated to reject a fraction of lower grade ore, and the tertiary crushing standard design unit/s and modular ore classification unit/s is/are operated to produce suitable sizes fractions to match the throughput capacity of the subsequent modular design units in the secondary gangue rejection section.

2. The method claimed in claim 1 , wherein bulk sorting standard design unit/s are operated to accept and reject a particular grade of ore, thereby to adjust throughput allocation between ore proceeding to the tertiary crushing unit/s, and reject ore assigned to stockpile.

3. The method claimed in claim 1 , wherein the modular ore classification standard design unit/s is/are adjusted to change the mass split of ore between size ranges best suited for coarse flotation, fine flotation, stockpile and heap leach.

4. The method claimed in claim 1 , wherein a lower grade reject fraction of the ore obtained from one or more of bulk sorting, screening, coarse flotation or the modular classification is stockpiled for later processing.

5. The method claimed in claim 1 , wherein a lower grade reject fraction of the ore obtained from one or more of bulk sorting, screening, coarse flotation or the modular classification is assigned to heap leaching.

6. The method claimed in claim 1 , wherein the tertiary crushing unit/s is/are operated in closed circuit with the classification unit/s, such that total crusher throughput and mineral recovery is optimized by adjusting the classification cut size.

7. The method claimed in claim 1 , wherein more than one bulk sorting standard design units are configured to split the ore into separate high-grade and low-grade streams to feed different tertiary crushing standard design units; and a fines fraction from more than one standard screening units is sent to the secondary gangue rejection section, to allow the highest value ore available from mining to be directed to tertiary crushing to fill a maximum throughput capacity of the more than one tertiary crushing standard design units.

8. The method claimed in claim 1 , wherein the one or more modular ore classification standard design unit/s are adjusted intermittently to change a p50 split size, thereby to change the mass split of ore between the size ranges best suited for one or more of coarse flotation, fine flotation, heap leach and recycle to the one or more tertiary crushing standard design unit/s.

9. The method claimed in claim 1 , wherein a layout of the plant enables modular standard design units to be added to the plant, to optimise performance for any particular sulphide ore being processed.

10. The method claimed in claim 1 , wherein a mining rate of the ore is adjusted to fill the tertiary crushing unit/s with the highest available value ore at the throughput rate achievable by the downstream processing configuration.

11 . The method claimed in claim 1 , wherein the standard concentrator plant is replicated in standard design units to match the processing capacity with the ultimate mine capacity.

12. The method claimed in any one of the preceding claims, wherein the standard design plant reduces the time between resource discovery and stable operations.