PROCESSING OF LATERITE ORES

Abstract

This invention relates to a method for processing nickel laterite ore, including the steps of obtaining a mined laterite ore from a mining operation 42; and feeding the ore through a bulk sorter 44 comprising a sensor arrangement and a diverting mechanism that separates the ore into a beneficiated stream of nickel laterite ore 28 wherein the grade of nickel is higher than the grade of the ore fed into the bulk sorter for further processing 52 by leaching or smelting; one or more low grade fractions of ore 50 with a lower nickel grade than the beneficiated stream; and a waste fraction 46. This configuration efficiently separates lower grade patches in the run of mine ore, to either a low-grade stockpile or waste, and efficiently blends the selected high-grade ore to meet the specifications of the subsequent processing.

Claims

1. A method for processing nickel laterite ore, including the steps of: obtaining a mined laterite ore from a mining operation; and feeding the ore through a bulk sorter comprising a sensor arrangement and a diverting mechanism that separates the ore into: a beneficiated stream of nickel laterite ore wherein the grade of nickel is higher than the grade of the ore fed into the bulk sorter for further processing by leaching or smelting; one or more low grade fractions of ore with a lower nickel grade than the beneficiated stream; and a waste fraction.

2. The method claimed in claim 1, wherein the sensor arrangement and diverting mechanism are configured to increase the grade of nickel in the beneficiated stream by more than 5% relative to the ore fed into the bulk sorter.

3. The method claimed in claim 2, wherein the grade of nickel in the beneficiated stream is increased by more than 10% relative to the ore fed into the bulk sorter.

4. The method claimed in claim 3, wherein the grade of nickel in the beneficiated stream is increased by more than 15% relative to the ore fed into the bulk sorter.

5. The method claimed in claim 2, wherein the beneficiated stream comprises at least 50% by mass of the ore fed into the bulk sorter.

6. The method claimed in claim 2, wherein the beneficiated stream of nickel laterite ore is suited for smelting an comprises more than 1.8% and up to 2.6% Ni by mass relative to the ore.

7. The method claimed in claim 6, wherein the beneficiated stream of nickel laterite ore is suited for smelting and comprises more than 2% and up to 2.6% Ni by mass relative to the ore.

8. The method claimed in claim 7, wherein the beneficiated stream of nickel laterite ore is suited for smelting and comprises more than 2.2% and up to 2.6% Ni by mass relative to the ore.

9. The method claimed in claim 2, wherein the beneficiated stream of nickel laterite ore is suited for leaching and comprises more than 1% and up to 1.6% Ni by mass relative to the ore.

10. The method claimed in claim 9, wherein the beneficiated stream of nickel laterite ore is suited for leaching and comprises more than 1.3% and up to 1.6% Ni by mass relative to the ore.

11. The method claimed in claim 10, wherein the beneficiated stream of nickel laterite ore is suited for leaching and comprises more than 1.45% and up to 1.6% Ni by mass relative to the ore.

12. The method claimed in claim 1, wherein the low-grade ore fractions are deposited into multiple low-grade stockpiles.

13. The method claimed in claim 12, in which the sensor arrangement is configured to simultaneously measure and records the nickel and the gangue and impurity elements such as SiO.sub.2, MgO, Co and Fe in the beneficiated stream/s and the low grade stockpiles.

14. The method claimed in claim 13, wherein the gangue and impurity elements include SiO.sub.2, MgO, Co and Fe.

15. The method claimed in claim 13, wherein, in the further processing of the beneficiated stream by leaching or smelting, material from the low-grade stockpile/s is blended with the beneficiated stream and the recorded measurements of nickel and gangue and impurity elements in the beneficiated stream and low grade stockpiles is used to determine the amount of material from the low-grade stockpile/s blended with the beneficiated stream to meet processing specifications of the further processing of the beneficiated stream, by leaching or smelting.

16. The method as claimed in claim 1, wherein the mining operation comprises grade control drilling, wherein drill hole spacing is at least 15 m.

17. The method as claimed in claim 16, wherein the mining operation comprises grade control drilling, wherein drill hole spacing is greater than 15 m.

18. The method as claimed in claim 1, in which the bulk sorter is configured to reject the waste that occurs due to inaccurate loading from the mine face.

19. The method as claimed in claim 1, in which the bulk sorter is configured to sort material below cut-off-grade to recover high grade patches of ore within the grade control block in the mining operation.

20. The method as claimed in claim 1, where the bulk sorter is incorporated into a mobile or relocatable system that is progressively relocated and maintained within 500 m of the active mining face in the mining operation.

21. The method as claimed in claim 20, where the bulk sorter is incorporated into a mobile or relocatable system that is progressively relocated and maintained within 200 m of the active mining face in the mining operation.

22. The method as claimed in claim 21, where the bulk sorter is incorporated into a mobile or relocatable system that is progressively relocated and maintained within 100 m of the active mining face in the mining operation.

23. The method as claimed in claim 20, in which more than 70% of the waste fraction is redeposited directly into an area disturbed by the mining operation.

24. The method as claimed in 23, in which more than 80% of the waste fraction is redeposited directly into an area disturbed by the mining operation.

25. The method as claimed in claim 24, in which more than 90% of the waste fraction is redeposited directly into an area disturbed by the mining operation.

26. The method as claimed in claim 1, in which more than 70% of the low-grade fractions is deposited directly in the area previously disturbed by the mining operation, for temporary storage.

27. The method as claimed in claim 1, in which more than 80% of the low-grade fractions is deposited directly in the area previously disturbed by the mining operation, for temporary storage.

28. The method as claimed in claim 1, in which more than 90% of the low-grade fractions is deposited directly in the area previously disturbed by the mining operation, for temporary storage.

29. The method as claimed in claim 13, in which the recorded sensor information is used to reduce double handling of beneficiated ore, such that less than 30% of beneficiated ore is stored in a blending stockpile prior to delivery to the processing facility.

30. The method as claimed in claim 29, in which the recorded sensor information is used to reduce double handling of beneficiated ore, such that less than 20% of beneficiated ore is stored in a blending stockpile prior to delivery to the processing facility.

31. The method as claimed in claim 30, in which the recorded sensor information is used to reduce double handling of beneficiated ore, such that less than 10% of beneficiated ore is stored in a blending stockpile prior to delivery to the processing facility.

32. The method as claimed in claim 13, in which the recorded sensor information is used for stockpile management to enhance the control the gangue and impurity elements fed to processing, to preferably within 10% of the desired daily feed ratios.

33. The method as claimed in claim 32, in which the recorded sensor information is used for stockpile management to enhance the control the gangue and impurity elements fed to processing, to preferably within 5% of the desired daily feed ratios.

34. The method as claimed in claim 1, in which multiple bulk sorters are located at different mining faces in the mining operation, and each sorter produces a beneficiated stream to feed a central processing facility.

35. The method as claimed in claim 1, in which bulk sorting is used to beneficiate the ore prior to transportation to a remote processing facility.

36. The method as claimed in claim 1, in which the bulk sorter is used to identify and separate ore that is particularly suited to further upgrade by screening.

37. The method as claimed in claim 13, in which the nickel grade from sorting is adjusted periodically to reflect the grade of the remaining resource and/or the nickel price of the product.

38. The method as claimed in claim 13, wherein the method is configured to transform a low-grade resource into a nickel orebody that warrants processing.

39. The method claimed in claim 1, wherein heterogeneity is maintained by avoiding homogenisation of the ore during mining, loading and haulage of the ore, to maintain the spatial integrity of the natural ore body.

40. The method claimed in claim 39, wherein, the ore is not mixed, for example by stockpiling prior to bulk sorting.

41. A method of optimising the mining and processing of nickel laterite ore includes: i) carrying out grade control procedures in mining of the laterite ore; ii) feeding mined ore to a bulk sorter comprising a sensor arrangement and a diverting mechanism that separates the ore into: a beneficiated stream of nickel laterite ore wherein the grade of nickel is higher than the grade of the ore fed into the bulk sorter, for further processing by leaching or smelting; one or more low grade fractions of ore with a lower nickel grade than the beneficiated stream; and a waste fraction; wherein: the sensor in the bulk sorter simultaneously measures and records the nickel and gangue impurity elements in the beneficiated stream/s and the low grade stockpiles; and the recorded measurements of nickel and gangue and impurity elements are used: in blending of the low grade stockpile/s with a beneficiated stream, to meet processing specifications of the further processing of the beneficiated stream, by leaching or smelting; and in the mining grade control procedures procedures in mining of the laterite ore to optimise the overall mining process.

42. The method claimed in claim 41, wherein the grade control procedures in the mining of the laterite ore include drill hole spacing.

43. The method claimed in claim 41, wherein the gangue impurity elements include SiO.sub.2, MgO, Co and Fe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] FIG. 1 is a block diagram showing the heterogeneity in nickel laterites relative to a typical mining industry;

[0079] FIG. 2 is a graph showing the estimated grade tonnage curve for a Brasilian laterite ore;

[0080] FIG. 3 is a graph showing the impact of sorting on gangue concentrations in the sorted blocks;

[0081] FIG. 4 is a block diagram showing material flows arising from using bulk sorting in a laterite mine; and

[0082] FIG. 5 is a block diagram showing the impact of bulk sorting on material flows and stockpiling.

DETAILED DESCRIPTION OF THE INVENTION

[0083] The current invention is a configuration of the mining and materials handling processes for nickel laterite ores, that efficiently separate lower grade patches in the run of mine ore, to either a low-grade stockpile or waste, and efficiently blends the selected high-grade ore to meet the specifications of the subsequent processing.

[0084] This configuration allows significantly increased production at lower unit cost, than that used in existing grade control processes, by utilising the spatial heterogeneity of the ore, to separate the patches of the ore into different streams.

[0085] The spatial heterogeneity of the nickel content of the ore, can be expressed in the form of a grade tonnage curve. In the FIG. 2, the grade tonnage curve of a Brasilian nickel laterite orebody is illustrated in terms of the grade and tonnage relationship for 50 tonne discrete packages of ore, using a cut-off-grade of 0.9% nickel.

[0086] Below 0.9% the remaining nickel bearing materials in the mining area are considered as waste, as they are uneconomic to process through the processing facilities, despite having patches of ore within the grade control block that are of adequate grade.

[0087] Often, this waste must be mined, and transported to a waste pile, simply to access the adjacent higher-grade ore.

[0088] A similar shape of grade tonnage curve exists for acidic fraction of the laterite orebody.

[0089] It is evident from FIG. 2 that if for example, it was possible to selectively mine individual 50 tonne packages of ore from within the overall orebody grading 1.8%, that the grades of these best packages would contain well above 4% nickel.

[0090] However, such mining processes are impractical, because of the spread of the high-grade patches across all dimensions of the orebody. Thus, mining occurs sequentially, and a composite of the ore from the area being mined is allocated to the processing plant. Only limited opportunity exists for use of grade control techniques to demarcate those areas where the estimated grade is below that ideally suited to processing immediately, but not below the ultimate cut-off-grade. Where these areas of ore prevent access the higher-grade ore, they are typically mined and stockpiled for subsequent reclamation late in the mine life.

[0091] The level of heterogeneity evident in the shape of the curve in FIG. 2, indicates that bulk sorting has potential for beneficiating nickel laterites, as distinct from the more normal application of sorting of waste from ore, or the separation of ore suited to smelting from the ore suited for leaching.

[0092] However, to use bulk sorting to beneficiate the ore purely on nickel grade, could inadvertently cause significant issues in the blending required to achieve gangue elements within specification for processing. For example, if the magnesium content were strongly correlated with the nickel content, such beneficiation would render the ore un-processable.

[0093] The wider system for beneficiating nickel using bulk sorting, must also accommodate grade of gangue elements. This distribution is illustrated for the same 50 t packages of ore in FIG. 3.

[0094] The gangue content is relatively independent of nickel grade in that package at the 50-tonne package level. The data implies that if the nickel laterite ore were bulk sorted to beneficiate the nickel grade, there would be only modest implications for balancing the gangue minerals in the overall deposit.

[0095] Again, similar results to those in FIG. 3, were also evident for acidic ores. Using the bulk sorting technology that has been developed to sense and divert laterite ores into ore and waste streams (references 3,4,5), the grade tonnage relationships indicate that nickel laterite ores can be beneficiated into a desired grade, leaving a lower grade fraction as waste or for stockpiling and use later in the mine life.

[0096] Whilst measuring nickel content, the appropriately selected sensor can concurrently deliver a multielement analysis of the ore, probably at an accuracy better than conventional grade control processes. This source of data can then be used to increase the precision and efficiency of blending gangue materials.

[0097] In any area being sequentially mined, the bulk sorting system that is the subject of this invention can select the best patches of grade for processing now, and separate the remaining ore into both a waste stream and multiple low-grade stockpiles. Concurrently, the measurement of the gangue content (as illustrated schematically in FIG. 4) can be used to provide more precise inputs to the subsequent activities of blending and processing.

[0098] With reference to FIG. 4, an embodiment of the invention comprises the following stages: drill and analysing stage 20; planning stage 22; mine analyse and beneficiate and haul stage 24; stockpile blend and reclaim stage 26; and process to saleable product stage 28. In the drilling stage 20, drilling spacing does not need to provide accurate estimate, just to mine good zones first, and overall balanced Si/Mg. Drilling and analysis cost is lower. In the planning stage 22, mine planning must balance inputs for blending and feed highest grade blocks. In stage 24, mining feeds analyser selects the best ore and puts the low grade aside (waste or long term stockpile). Higher grade ore can be selected and the blend controlled. Mining rate is increased to keep smelter full. Mining equipment can be larger (as the exact digging of the material is no longer so critical). At stage 26, there is a low direct feed to processing. Double handling necessary for blending to produce an acceptable processing feed. Working capital can be lower with more direct feed. At stage 28, higher nickel grade eimplies greater production at lower cost/profit. Nickel production costs are lower and production can be increased.

[0099] This enhanced information provides an opportunity to streamline the stockpiling activity (as illustrated schematically in FIG. 5). Precise knowledge of the gangue compositions can be gathered from multiple ore sources hauled to a single sorter, or from multiple sorters located close to the different mining faces across the orebody.

[0100] With reference to FIG. 5, current operations comprise grade control 30 and mining 32. From the mining, there is a waste stream 34 and multiple blending stockpiles 36 are required to compensate for imprecise grade control estimation, which are used for further processing 38. Direct ore delivery is less than 20% to enable blending of nickel feed to processing. According to an embodiment of the process of the present invention, less precise grade control 40 is required. After mining 42 ore is sent to a bulk sorter 46. The bulk sorter sorts a waste stream 44, a beneficiated faction 48 for further processing, and low grade factions 50 which can be used as trimming stockpiles in further processing 52. Direct ore delivery is less than 50% to enable blending and the highest grade nickel feed to processing.

[0101] The sensors have been developed.

[0102] The bulk sorter 46 comprises a sensor arrangement for analysis of ores, typically by irradiation of the ore on conveyors running at normal speed, and measuring the resultant signal consistent with the characteristics of the ore integrated with a diverterting mechanism to separate different fractions of the ore (References 3-6, incorporated herein by reference). For example, the GEOSCAN utilises the technique known as Prompt Gamma Neutron Activation Analysis (PGNAA). The GEOSCAN incorporates high efficiency detectors and state-of-the-art digital spectrometer, which overcomes the limitations of conventional, low efficiency detection systems. Whilst these sensors have predominantly in the past been used for blending of products to meet market specifications, accoring to the present inventionm they can be used to measure and reject waste present in the incoming ore. Used in this mode, the sensing and separation is termed bulk sorting. Another example is the Sodern CNA-Nickel online elemental analyzer, based on the PFTNA (Pulsed Fast and Thermal Neutron Activation) technology.

[0103] A few commercial bulk sorting operations have been proposed or commissioned, mainly in the iron ore and copper applications, to separate ore for subsequent processing from waste for disposal. The waste may be naturally occurring, or a consequence of dilution that occurs during mining. In these cases, the bulk sorter is used to reject waste prior to the processing facility, not as an integrated part of the overall materials flow from mining to processing.

[0104] This information can enable a higher proportion of beneficiated ore to be delivered direct to a final blending stockpile prior to processing, rather than via multiple intermediate blending stockpiles.

[0105] In any mining sequence, there will be times when the gangue elements from the different mine faces are not balanced. In these circumstances, and depending on nickel grade and gangue composition, the more extreme gangue compositions can be assigned by the bulk sorter to a trimming stockpile or to waste.

[0106] The trimming stockpile can then be reclaimed when required for balancing the feed in the other direction.

[0107] In the case of smelting requiring the blending of acidic and basic ores to achieve an appropriate silica to magnesia ratio, this approach enables efficient mining and stockpiling, but also enables the disposal to waste of the least attractive materials for a given orebody.

[0108] The invention of the bulk sorting system for nickel laterites, in its full embodiment, consists of [0109] Grade control procedures and mining of the laterite ore, are adapted to the spacing and equipment size to optimise the overall mining process [0110] Mining locations and sequences are selected to contain acceptable nickel grades and produce the approximate mix of ore required to meet processing specifications [0111] The scale of mining equipment and the mining procedures are adapted to utilise the lower impact of dilution, which is managed by the sorter [0112] Ore is fed directly from mining to the bulk sorter without an intervening stockpile. [0113] Loading of the bulk sorter can be by truck, or directly from the loader to a mobile sorter. [0114] If the sensor is in the loader rather than on a conveyor, diversion is achieved through a truck allocation technology. [0115] The sensor determines the average grade of a package of ore, and the diverter directs the packages into multiple different destinations, depending on their composition. [0116] The lower grade patches of nickel ores, or those with unacceptable ratios of gangue, are separated and allocated to one of the following streams [0117] discarded if they are uneconomic to process using the installed processing assets [0118] temporary storage in trimming stockpiles if they are a high nickel grade but outside of the preferred grade for direct feed to processing. [0119] long term storage stockpiles, if the ore package contains an economic nickel grade, but not the highest grade available to process now. [0120] to screening or separate stockpiles if the ore type contains a nickel grade and mineral assemblage that is amenable to further beneficiating by screening [0121] The beneficiated stream of nickel laterite ore, that is within or close to the specification required for further processing, is directed to the processing feed. [0122] The trimming of gangue compositions occurs by reclaiming of ore of known composition from one of the trimming stockpiles

[0123] For different nickel laterite operations, all or part thereof of this full embodiment will be required.

[0124] Critical elements to effectively managing the nickel grade enhancement and materials handling in this invention are: [0125] Avoiding homogenisation as much as possible during the mining, loading and haulage of ore, to maintain the spatial integrity of the natural orebody as it is presented to the bulk sorter [0126] Adjusting the mining rate, to generate a high grade of beneficiated nickel laterite at the production rate demanded by the available processing capacity [0127] Adjusting the mine plan to balance the gangue elements, to avoid the need for multiple, large scale blending stockpiles after bulk sorting and prior to processing [0128] Utilising the accumulated sensor data to control the reclaim from trimming stockpiles to balance the gangue components of the direct feed.

[0129] Through integrating the mining, sorting and blending process in the current invention it is possible to increase the grade of the laterite ores sent to production, whilst reducing double handling, and improving the precision of blending.

[0130] As evident in the grade tonnage curves (FIGS. 2 and 3), it is possible to generate a very high-grade feed with a relatively low tonnage yield, or a slightly increased nickel grade but with a high tonnage yield.

[0131] By changing the grade selected in bulk sorting, it becomes possible to adjust the processing feed to an economic optimum value for the specific orebody being mined. And to progressively alter these grades through the remaining life of mine.

[0132] The invention also increases the available flexibility in the design and operation of the nickel laterite mining activity, particularly where the bulk sorters are located close to or in the mining areas.

[0133] For example, [0134] Spacing between grade control drill-holes can be increased [0135] Waste can be stacked within the mining zone [0136] Dilution can be less stringently managed during mining [0137] Resource recovery can be enhanced by separating the high-grade ore patches from grade control blocks just under the current mining cut-off-grade [0138] The scale of mining and haulage equipment can be increased, subject to limiting homogenisation [0139] The amount of material re-handling in the mine can be reduced

[0140] For an embodiment of the invention where the sorting is undertaken in a mobile or relocatable system, the bulk sorter can be moved to remain in or close to the mining pit. This enables a very short haul distance for the medium grade ore, prior to beneficiation. It also enables the waste to be redeposited in the mined-out area, with minimal cost of haulage and mine restoration.

[0141] The material for the low-grade stockpile material can also be placed in a mined-out zone, minimising the land disturbance.

[0142] Only beneficiated ore from bulk sorting is hauled a significant distance to the processing facility, thus reducing overall haulage costs per tonne of nickel produced.

[0143] In another embodiment to the invention, bulk sorting is combined with screening.

[0144] Beneficiation by screening (based on differential nickel grade at different particle sizes) is based on a different principle from the beneficiation by bulk sorting (spatial heterogeneity). Thus, screening and bulk sorting are complementary and can be utilised in sequence on a laterite ore. If an ore domain is such that screening delivers an economic upgrade, the bulk sorter can sense and separate that ore domain, thus segregating the fraction well suited to screening. This enhances the nickel upgrade and reduces the capital and operating costs of the screening plant.

[0145] If, as for some nickel laterites, screening is only realistic with partially dried ore, bulk sorting enables on the appropriate ore to be segregated and stockpiled awaiting subsequent screening in the dry season.

[0146] In yet another embodiment of the invention, the location of mining can be balanced to provide the approximate blend in the feed to processing. The bulk sorter is adjusted to deliver a precise gangue composition to processing, at high nickel grade.

[0147] The modest fractions of the ore that meet the selected nickel grade but cannot be fitted into the gangue specifications at a specific time, can be stockpiled, as trimming stockpiles.

[0148] The resultant increase in direct feed reduces the working capital and cost of materials re-handling. Direct deliveries can be enhanced from less than 10% to well above 50% and depending on the balance in mining, approaching 100%.

[0149] In yet another embodiment of the invention, the nickel content of the feed can be adjusted using bulk sorting, to respond to changes in the nickel price, or the grade and tonnage of the resource that is still available to mine. Thus, the value of the resource can be optimised over time. And in yet another configuration of the invention, a bulk sorter can be used to beneficiate the nickel laterite, thus generating an ore that justifies transportation to a remote processing facility.

[0150] The following documents are incorporated herein by reference:

Reference 1

[0151] ATTEMPTS AT THE BENEFICIATION OF LATERITIC NICKEL ORE. Onodera, Jiroh (1); Inoue, Toshio (1); Imaizumi, Tsunemasa (1) Source: International Journal of Mineral Processing, v 19, n 1-4, p 25-42, May 1985; ISSN: 03017516; DOI: 10.1016/0301-7516(87)90030-5; Conference: Proc of the Int Symp on Laterite, Oct. 14, 1985-Oct. 17, 1985

Reference 2

[0152] Physical separations as potential techniques for preconcentration of nickel laterites Keith Quast (Future Industries Institute, University of South Australia) Jonas Addai-Mensah (Future Industries Institute, University of South Australia) William Skinner (Future Industries Institute, University of South Australia) 2016 Chemeca Conference 2016 (Adelaide, Australia 25-28 Sep. 2016)

Reference 3

[0153] US20130201481A1

Reference 4

[0154] MetPlant2015 Metallurgical Plant Design and Operating StrategiesWorld's Best Practice Perth, Australia 7-8 Sep. 2015 ISBN: 978-1-5108-2145-3 Optimising Plant Feed Quality and Process Performance Using Geoscan Elemental Analysis H Kurth 373

Reference 5

[0155] https://www.scantech.com.au/solution/nickel/

Reference 6

[0156] Malvern Panalytical Sodern CAN-Nickel brochure [0157] https://www.malvernpanalyrical.com/en/products/product-range/cna-range/cna-nickel