Framework for Evaluation of preconcentration Strategies
The following framework has been used to quantify the economic and environmental impacts of preconcentrationMethodologies used to separate gangue from valuable material. techniques at numerous metalliferousYielding or containing metal. operations. The framework was also applied to quantify the impacts of mine to mill strategies and the adoption of new processing technologies at operations.
The framework consists of:
- Characterisation of preconcentrationMethodologies used to separate gangue from valuable material. responses;
- geometallurgy and spatial modelling;
- process designConfiguration and optimisation of equipment selection and layout. and simulation;
- Strategic mine planning; and
- Strategy evaluation.
The interactions of the framework in the quantification of the economic and environmental impacts of preconcentrationMethodologies used to separate gangue from valuable material. are presented in the figure below.
Characterisation
Characterisation of preconcentrationMethodologies used to separate gangue from valuable material. responses throughout the geometallurgical domainGeological, statistical or spatial groupings used for modelling.s of a deposit provides the foundation for technoeconomic evaluation of preconcentrationMethodologies used to separate gangue from valuable material. techniques. The process of characterising preconcentrationMethodologies used to separate gangue from valuable material. responses requires a combination of laboratory test work and grade heterogeneity modelling to quantify the strength of the drivers for each separation technique.
Characterisation of Natural Deportment
Characterisation of the natural deportment response throughout the deposit requires testwork performed at drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. and bulk scales. Intact diamond drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. or coarseSubjective term for the larger sized component of feed assay rejects are used to quantify the natural deportment response in future ore to be mined. The sampling campaign should cover the rock typeGeological classification of material into discrete groups.s, grade ranges and spatial distribution of material within, and just outside, the planned mining extents, biasing the next 5-10 years of production. Intact drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. is crushed to -3.5 mm and screened through a series of sieves with the aim to produce five to six size fractionClassified material based on specific size constraints (i.e. two specific sizes).s of similar mass for assay.
Bulk samples are used to determine the production scaleTrials run at or near the size required for an operation. natural deportment response of material. These samples may be taken from belt cuts or ROMRun of mine material and are therefore limited to the material currently exposed or in stockpiles. Bulk samples provide an indication of the scale-up factor required to convert diamond drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. responses to production scaleTrials run at or near the size required for an operation. responses. The bulk samples are screened into five to six different size fractionClassified material based on specific size constraints (i.e. two specific sizes).s of similar mass and each size fractionClassified material based on specific size constraints (i.e. two specific sizes). is assayed.
The assay results of the size fractionClassified material based on specific size constraints (i.e. two specific sizes).s, for bulk and drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. samples, can be viewed as a plot of cumulative mass (or percent passing) versus upgrade factorGrade of accept material divided by feed grade. (the grade of the undersizeMaterial below an specified size (generally used to define material that falls through a screen deck). relative to the head grade of the sample) to assess the strength of the natural deportment response. A linear relationship often exists between the natural log of the upgrade factorGrade of accept material divided by feed grade. and the negative natural log of cumulative mass. The slope of this linear relationship can be used to derive a single metric to describe the strength of the natural deportment response. This single metric can be used to quantitively rank the strength of natural deportment responses in different rock typeGeological classification of material into discrete groups.s or deposits. It can also be used to interpolate the natural deportment response throughout the resource modelDigitised model of the deposit. to assist in the optimisation of the strategic mine plan with preconcentrationMethodologies used to separate gangue from valuable material. by screening.
Characterisation of Induced Deportment
Characterisation of the Induced deportment response requires assessment of the natural deportment response, analysis of In-situContained in unbroken ground. grade heterogeneity and engineering of a bimodal blast fragmentationDistribution of rock created through the application of explosives..
In-situContained in unbroken ground. grade heterogeneity is assessed at a blast holeCylindrical hole used to load explosives into unbroken material. scale using a combination of retrospective data from blast holeCylindrical hole used to load explosives into unbroken material. assays and forward-looking geostatistical estimates from resource drillingExploration and infill drill hole data (typically diamond drill core).. blast holeCylindrical hole used to load explosives into unbroken material. assays provide a high-resolution, 2-dimensional data set that can be combined with grade controlStage at which final boundaries between ore and waste are calculated. polygons to identify specific areas where high or low-grade pockets of material were sent to the incorrect destination due to limitations in the selective mining unit (SMU). These areas can then be assessed for Induced deportment response by altering the blast design to achieve finer fragmentation in high-grade and coarseSubjective term for the larger sized component of feedr fragmentation in low-grade. Modelled blast fragmentationDistribution of rock created through the application of explosives.s, natural deportment response and screen apertureMinimum dimension at which material will be retained as oversize. size are used to derive the grade and mass of screen oversizeMaterial above a specific size (generally used to define material that is retained on a screen deck). and undersizeMaterial below an specified size (generally used to define material that falls through a screen deck). and characterise the Induced deportment response.
Forward-looking estimates of Induced deportment responses require geostatistical estimation of In-situContained in unbroken ground. grade heterogeneity at a blast holeCylindrical hole used to load explosives into unbroken material. separation scale. Uniform conditioning (UC) is used to estimate the probability of a blast holeCylindrical hole used to load explosives into unbroken material. burden and spacingTwo terms for defining the distance between blast holes. volume being above a series of cut-off grades within a panelA discrete section within a resource model (i.e. block). of material in the resource modelDigitised model of the deposit.. This estimate is combined with different cut-off grades for high and low-energy blast fragmentationDistribution of rock created through the application of explosives., screen apertureMinimum dimension at which material will be retained as oversize. sizes and the natural deportment response to estimate the Induced deportment response throughout the resource modelDigitised model of the deposit.. However, UCUniform Conditioning estimates do not provide the exact spatial location of In-situContained in unbroken ground. heterogeneity but rather an estimate of the average In-situContained in unbroken ground. heterogeneity present for the kriged grade of the panelA discrete section within a resource model (i.e. block). within the estimation domainGeological, statistical or spatial groupings used for modelling.. Therefore, the use of the estimated Induced deportment response using UCUniform Conditioning estimates of In-situContained in unbroken ground. grade heterogeneity should be restricted to long-term, Strategic mine planning decisions. These decisions are based on larger mining volumes that are more likely to reflect the average estimated response.
The aim of the bimodal blast fragmentationDistribution of rock created through the application of explosives. is to achieve the greatest difference in the particle size distribution (PSD) between coarseSubjective term for the larger sized component of feed and fine blast fragmentationDistribution of rock created through the application of explosives. to provide the highest separation potential by screening. The results are dependent on the physical rock characteristicsGeneric term for material properties. and blast design parameters including burden and spacingTwo terms for defining the distance between blast holes., hole diameter and charge. Adjustments to blast design parameters are often limited to the charging of holes, as grade heterogeneity of a blast is not confirmed until the blast holeCylindrical hole used to load explosives into unbroken material. chips are assayed. However, the greatest opportunity to create a wide differential between coarseSubjective term for the larger sized component of feed and fine blast PSDs is through burden and spacingTwo terms for defining the distance between blast holes. of blast holeCylindrical hole used to load explosives into unbroken material.s. Predictive models using the blast holeCylindrical hole used to load explosives into unbroken material. data of the benchIndividual levels within an open pit. above and infill drilling can be used to inform adjustments to burden and spacingTwo terms for defining the distance between blast holes. ahead of time. Alternatively, measure while drilling (MWD) data and real-time grade measurements using sensors on drill chips may be used to inform a change in drill pattern in real time.
Characterisation of Bulk Ore Sorting
Characterisation of the bulk ore sorting response requires estimation of the grade heterogeneity delivered to the sensor at a scale reflecting the separable parcels size of the sorting system and an estimate of sensor and mechanical separation performance. In-situContained in unbroken ground. grade heterogeneity can be estimated using UC, as described in characterisation of Induced deportment, using a separation volume approximating the separable parcel size. However, UCUniform Conditioning has been shown to have limitations in the estimation of In-situContained in unbroken ground. grade variability present at very small separation units, including truck and shovel volumes.
While the In-situContained in unbroken ground. grade heterogeneity of a separable parcel of material can be estimated using geostatistical techniques, the process of mining, loading, transporting and crushing the material prior to presentation of the material to a sensor can significantly reduce measured heterogeneity and the bulk ore sorting response. Modelling the impact of mixing in each stage of mining and material handling is a critical focus to support desktop bulk ore sorting evaluations. Currently, empirical measurements of grade heterogeneity present in separable parcels of material at the point of deployment may provide the best estimation of the delivered heterogeneity to the sensor. In the absence of empirical data, the impact of mixing on In-situContained in unbroken ground. grade heterogeneity estimates can be examined through sensitivity analysis.
Sensor and separation performance of the bulk ore sorting system can be examined using anticipated or measured accuracy and precision results for the sensor technology and modelling of mechanised sorting efficiency. The combined impact of delivered heterogeneity, sensor performance and separation performance can be modelled using discrete event simulation to estimate production scaleTrials run at or near the size required for an operation. bulk ore sorting response. This response can then be linked to either insitu grade heterogeneity estimates or material classifications within domainGeological, statistical or spatial groupings used for modelling.s to interpolate a bulk ore sorting response in the resource modelDigitised model of the deposit..
Characterisation of particle sorting
Characterisation of the particle sorting response requires measurements for the grade distribution of particles Individual rocks within discrete size fractions. present in discrete size fractionClassified material based on specific size constraints (i.e. two specific sizes).s of crushed and screened material, the performance of the sensor technology and mechanical separation and the natural deportment response. The grade distribution of particles Individual rocks within discrete size fractions. within different size ranges can be determined through laboratory assay. These assays can be used to provide a theoretical particle sorting response in the absence of particle sorting test work.
The combined sensor and mechanical separation performance of particle sorters can be examined using supplier testing services. This service uses a particle sorter to test a sample from the mine using different sensors. The particles Individual rocks within discrete size fractions. are marked to indicate which stream they reported to with each sensor then each particle is weighed and assayed. The assay results and sorting performance can then be used to determine the particle sorting response for each sensor technology.
particle sorting requires screening to prepare a specified particle size range to feedMaterial entering a predetermined system. the particle sorter. To determine and optimise the integrated particle sorting and screening response of the material, the natural deportment response is required to estimate the grade of the screen undersizeMaterial below an specified size (generally used to define material that falls through a screen deck).. The combined estimates for particle sorting response and natural deportment screening response can be used to characterise the upgrade responseOutput of accept stream grade over feed grade. of material with particle sorting.
Characterisation of Coarse Gravity_separation
Characterisation of the coarseSubjective term for the larger sized component of feed gravity response requires laboratory testwork and the natural deportment response. Laboratory and large scale testwork can be used to examine separation performance for dense media separation and inline pressure jigs. Samples from the mine are treated in different densities of media or at different inline pressure JIG settings and the float and sink streams are assayed to evaluate and optimise gravity separation performance.
coarseSubjective term for the larger sized component of feed gravity separation requires pre-treatment by crushing and screening to produce a consistentPSDParticle Size Distribution in the feedMaterial entering a predetermined system. and to remove finesSubjective term for the smaller sized component of feed. Therefore, the upgrade from coarseSubjective term for the larger sized component of feed gravity separation must also consider the natural deportment response of the finesSubjective term for the smaller sized component of feed. An example from an operation where the upgrade to finesSubjective term for the smaller sized component of feed is as significant as the upgrade from the inline pressure JIG is provide by.
Geometallurgy and Spatial Modelling
Interpolation of preconcentrationMethodologies used to separate gangue from valuable material. responses in the resource modelDigitised model of the deposit. require assessment of suitable geometallurgy domainGeological, statistical or spatial groupings used for modelling.s and selection of an appropriate geostatistical estimation method. There is often insufficient data for the development of specific preconcentrationMethodologies used to separate gangue from valuable material. domainGeological, statistical or spatial groupings used for modelling.s during early stages of preconcentrationMethodologies used to separate gangue from valuable material. evaluations. In these cases, natural deportment and laboratory measured preconcentrationMethodologies used to separate gangue from valuable material. responses may be interpolated in the resource modelDigitised model of the deposit. using the current estimation methodology for geometallurgical parameters at the operation. Estimates for In-situContained in unbroken ground. grade heterogeneity using UCUniform Conditioning modelling (as discussed in the characterisation of Induced deportment and bulk ore sorting responses) should also follow the current estimation domainGeological, statistical or spatial groupings used for modelling.s and search parameters for the operation.
Geostatistical estimation methods range in sophistication from simple inverse distance weighting methods to complex multi indicator kriging or conditional simulations. In the absence of adequate spatial dataData that has a clear position in 3d space (eg. Drill holes, GPS etc…). regarding the preconcentrationMethodologies used to separate gangue from valuable material. responses, minimal estimation techniques or domanial averages should be applied. As greater knowledge of the preconcentrationMethodologies used to separate gangue from valuable material. response develops, more sophisticated estimation methods provide greater control for the population of the preconcentrationMethodologies used to separate gangue from valuable material. response in the resource modelDigitised model of the deposit..
Process Design and Simulation
process designConfiguration and optimisation of equipment selection and layout. and simulation considers the integration and interactions of preconcentrationMethodologies used to separate gangue from valuable material. techniques with the existing infrastructure and processing facilities of the operation. process designConfiguration and optimisation of equipment selection and layout. and simulation is an iterative activity that alternates with the optimisation of preconcentrationMethodologies used to separate gangue from valuable material. strategies within the strategic mine plan.
Process Design
process designConfiguration and optimisation of equipment selection and layout. assesses the equipment requirements, plant layout and material handling strategies for given rock characteristicsGeneric term for material properties. and capacities to develop an operationally capable preconcentrationMethodologies used to separate gangue from valuable material. circuitGeneral term for a collection of comminution/flotation equipment.. During early stages of preconcentrationMethodologies used to separate gangue from valuable material. evaluations, several preconcentrationMethodologies used to separate gangue from valuable material. designs are developed at a range of preconcentrationMethodologies used to separate gangue from valuable material. capacities. These designs provide an understanding of how operational and capital costsExpected upfront costs of a given scenario or plan. change with preconcentrationMethodologies used to separate gangue from valuable material. capacity to assist optimisation of preconcentrationMethodologies used to separate gangue from valuable material. strategies in the strategic mine plan.
process designConfiguration and optimisation of equipment selection and layout.s may include fixed, semi-mobile or mobile deployment options. Fixed options have a higher capital cost and lower operating cost and are best suited to a constant production capacity over a longer period. At the other end of the spectrum, mobile options have a lower capital cost and higher operating cost and offer flexibility to increase or decrease production capacity over shorter periods. Mobile or semi-mobile preconcentrationMethodologies used to separate gangue from valuable material. plants are ideally suited to Production TrialOn-site test of Grade Engineering equipment (can be on/off line).s for preconcentrationMethodologies used to separate gangue from valuable material. techniques and initial implementation.
process designConfiguration and optimisation of equipment selection and layout. governs the operating and capital costsExpected upfront costs of a given scenario or plan. for preconcentrationMethodologies used to separate gangue from valuable material. techniques and the location of the preconcentrationMethodologies used to separate gangue from valuable material. plant can have a large influence over both costs. The largest operating cost associated with bulk preconcentrationMethodologies used to separate gangue from valuable material. techniques is the rehandling of product streams. Selecting a location that minimises product rehandle for one or more product streams can greatly reduce the operational costs of preconcentrationMethodologies used to separate gangue from valuable material.. Furthermore, integrating preconcentrationMethodologies used to separate gangue from valuable material. within existing material handling transfer or decision points can eliminate rehandle for one or more product streams, greatly reducing operating and capital costsExpected upfront costs of a given scenario or plan. for preconcentrationMethodologies used to separate gangue from valuable material.. Critical locations to consider are:
- Close to the primary crusher, to allow the upgraded product stream to tie into the coarseSubjective term for the larger sized component of feed ore stockpile conveyor;
- At wasteMaterial determined to be below a predetermined grade or economic threshold. storage facilities or deferred stockpiles, to minimise rehandle of the downgraded product stream;
- At pit exits or in the mine, to minimise deviations in haulageMovement of material from in-pit to ex-pit. or handling distances to and from the preconcentrationMethodologies used to separate gangue from valuable material. plant; and
- At the mine face, ideally between or within digging and loading activities to eliminate product rehandling.
Process simulation
Process simulation is used to assess the impact of preconcentrationMethodologies used to separate gangue from valuable material. techniques on downstream production processes. These impacts depend on the preconcentrationMethodologies used to separate gangue from valuable material. technique. preconcentrationMethodologies used to separate gangue from valuable material. by screening alter the particle size distribution in feedMaterial entering a predetermined system. to the processing plant, often resulting in increased capacity in the comminution circuitGeneral term for a collection of comminution/flotation equipment. which may be used to increase throughputMetric for overall tonnage moving through a system within a specified time. or optimise grinding conditions to improve recovery. All preconcentrationMethodologies used to separate gangue from valuable material. techniques can increase the grade of the feedMaterial entering a predetermined system. to the processing plant which can improve flotation recovery.
Process modelling and simulation is performed using the Integrated Extraction Simulator (IES). IES is a cloud-based simulation covering the comminution and beneficiation activities of the entire operation from drilling and blasting through to final concentrateProduct generally produced by metal ore mines.. IES incorporates the ability to simulate the processing performance of multiple ore types, optimise process settings to maximise plant performance within specified constraints and to perform mass simulationIES specific term for repeated simulations of a circuit. and write responses back to the resource modelDigitised model of the deposit..
Strategic Mine Planning
Optimisation of the strategic mine plan provides a holistic approach to capture all impacts of new technologies and operational strategies deployed across the mining value chain, over the entire life of the operation. The optimisation is value driven, with the primary objective to maximise net present value within specified operational and processing constraints. For these reasons, optimisation of the strategic mine plan is the preferred method to evaluate preconcentrationMethodologies used to separate gangue from valuable material. techniques.
Inputs into Strategic mine planning include the resource modelDigitised model of the deposit. and operational parameters, constraints and economic assumptionsInputs used for business case evaluations.. From these inputs, the value of each blockA spatially constrained unit within the resource model. in the resource modelDigitised model of the deposit. is calculated for each processing destination including wasteMaterial determined to be below a predetermined grade or economic threshold. storage facilities. The maximum value of the blockA spatially constrained unit within the resource model. is assigned, and the Lerchs-Grossman algorithmUsed in the surface mining industry to solve the Pit Limit Problem and to generate an approximate solution to the Extraction Sequence Problem. is applied to develop a series of nested shells by adjusting the revenue factor applied to each block. These nested shells provide guidance to the selection of the ultimate pit and design of phases to be mined. The material can then be scheduled, and cut-off optimised, for all processing destinations in the operation.
The inclusion of preconcentrationMethodologies used to separate gangue from valuable material. techniques offer flexibility and opportunity for optimisation in their application and operational settings, such as screen apertureMinimum dimension at which material will be retained as oversize. or sorting cut-off. These options can be included in the optimisation of the strategic mine plan in much the same way trade-offs between throughputMetric for overall tonnage moving through a system within a specified time. and recovery with grind sizeTarget product size post grind. have traditionally been assessed. The figure below shows the interaction of operational decisions for preconcentrationMethodologies used to separate gangue from valuable material. and process plant settings that can be optimised in the strategic mine plan.
Once an optimal schedule and cut-off grade policy is produced, the resultant material movement and cashflow provides the best estimate of economic benefits relating to the scenario modelled. In addition, the material movements can be combined with power, fuel, steel and water consumption (from process and haulageMovement of material from in-pit to ex-pit. models) to provide environmental metrics relating to planned production and quantity the wasteMaterial determined to be below a predetermined grade or economic threshold. rock and tailings generated. A comparison of the strategic mine plan with and without preconcentrationMethodologies used to separate gangue from valuable material. techniques provides a robust quantification of anticipated economic and environmental impacts due to preconcentrationMethodologies used to separate gangue from valuable material..
Complete strategic mine plan optimisations for preconcentrationMethodologies used to separate gangue from valuable material. techniques have been performed with Whittle Consulting Enterprise Optimisation, Geovia Whittle™, COMET Strategy and COMET Scheduler and Datamine NPV Scheduler. However, due to the magnitude of work involved in performing a complete mine optimisation, early opportunity assessments for preconcentrationMethodologies used to separate gangue from valuable material. techniques are performed within the operation’s existing ultimate pit and phases. These evaluations operate under the presumption that if sufficient value can be found within the existing mine design, performing a complete Strategic mine planning optimisation will only unlock greater value.
Preconcentration Impact on Operational Capacities
Optimising the strategic mine plan requires balancing constraints to the rate of production imposed by mining, processing and marketing capacities. preconcentrationMethodologies used to separate gangue from valuable material. introduces an additional capacity to optimise that increases the effective processing capacity of an operation and changes the economic value of material, increasing the quantity of ore mined. As a result, the optimal balance between mining, processing, marketing and preconcentrationMethodologies used to separate gangue from valuable material. capacities must be established and there may be a need to increase mining and marketing capacities.
The requirement for additional mining capacityMaximum potential material moveable under current constraints. with preconcentrationMethodologies used to separate gangue from valuable material. is necessary for operations that are, or become, mining constrained. Generally, this is the optimal configuration for underground metalliferousYielding or containing metal. mines where mining capacityMaximum potential material moveable under current constraints. is the most capital-intensive constraint on production. As a result, the opportunity cost of production raises the cut-off for mined material and encourages the use of highly selective mining methods. Optimal preconcentrationMethodologies used to separate gangue from valuable material. strategies will seek to relieve the pressure on mining bottlenecks by preconcentrating material prior to the constraining activity, such as the preconcentrationMethodologies used to separate gangue from valuable material. of ore prior to an underground hoist. As a result, greater capacity in downstream mining activities are required to maintain the quantity of ore processed. preconcentrationMethodologies used to separate gangue from valuable material. may also unlock greater value in mining constrained operations by enabling a transition to lower-cost, less selective mining methods, simultaneously increasing resource utilisation and the quality of ore sent to processing destinations.
Conversely, the requirement for additional mining capacityMaximum potential material moveable under current constraints. with preconcentrationMethodologies used to separate gangue from valuable material. is less prevalent in operations that are processing constrained. Generally, this is the optimal configuration for open-pit metalliferousYielding or containing metal. mines where processing capacity is the most capital-intensive constraint on production. As a result, the opportunity cost of production raises the cut-off applied to processing, generating an excess quantity of economic ore from the mine. This excess ore is often deferred to stockpiles or allocated to lower-value processing destinations, such as dump leach. The increase in effective processing capacity with preconcentrationMethodologies used to separate gangue from valuable material. allows a greater quantity of ore to be treated as it is mined, reducing the quantity of material stockpiled or processed at a lower-value destination. This accelerates both the quantity of metal and the cashflow produced by the operation, significantly increasing NPV.
Strategy Evaluation
Strategy evaluation involves sensitivity, scenario and simulation modelling to find the optimal preconcentrationMethodologies used to separate gangue from valuable material. strategy and understand the value drivers for that strategy.
Sensitivity analysis is used to flex individual assumptions regarding preconcentrationMethodologies used to separate gangue from valuable material. performance and costs to understand the impact each assumption has on the value proposition. This information is useful in early opportunity assessments to identify critical assumptions for detailed examination in the next stage of evaluation.
Scenario analysis examines the effect of multiple simultaneous changes to preconcentrationMethodologies used to separate gangue from valuable material. assumptions. Common examples of scenario analysis applied to preconcentrationMethodologies used to separate gangue from valuable material. evaluations include the assessment of:
- Different individual or combinations of preconcentrationMethodologies used to separate gangue from valuable material. techniques;
- Different deployment capacities and locations for preconcentrationMethodologies used to separate gangue from valuable material. techniques; and
- Staging of capital and scaling-up of preconcentrationMethodologies used to separate gangue from valuable material. capacity.
Simulation analysis assigns probabilistic distributions to uncertain variables and through repeat analyses determines the probabilistic range of likely outcomes. During the evaluation of preconcentrationMethodologies used to separate gangue from valuable material. techniques, simulation analysis is best suited to examine the impact of uncertainty in the modelled preconcentrationMethodologies used to separate gangue from valuable material. responses. However, due to the magnitude of work involved, simulation analysis may be applied during detailed feasibility studies for deployment options of the selected preconcentrationMethodologies used to separate gangue from valuable material. technique(s).
Project Evaluation Stages
The time, personnel and investment required to examine new technologies and strategies to deploy at an operation can be substantial. A capital investment model is used to assist in focussing a company’s limited resources on the examination of the highest value options for an operation. This model uses a stage-gate approach to progress the most promising options and strategies from conception to operation at site. CRC ORE have followed this approach to apply the framework for evaluation of preconcentrationMethodologies used to separate gangue from valuable material. strategies at varying levels of detail to the different stages of project evaluation. A description of the different project evaluation stages is provided in the following Table.
Project Stage | Description |
Broad assessment of all available options, preliminary ranking by order of magnitude valuation and identify critical assumptions that require further examination. | |
Top ranked options and critical assumptions identified in the opportunity assessment are assessed in greater detail to provide higher confidence in their ranking and valuation. | |
Production TrialOn-site test of Grade Engineering equipment (can be on/off line). | Top ranked option(s) from concept study are demonstrated at pilot scale to prove concept in production environment and confirm critical assumptions. |
pre feasibility study | Detailed assessment of successful options trialled including alternative designs and layouts, capacities and deployment strategies, detailed risk assessment and identify best strategy for feasibility study. |
feasibility study | Detailed assessment of the selected strategy including definitive designs and cost estimates, environmental and social impact assessments and permitting, licensing and supply contracts for final approval to invest and implement the strategy. |
Implementation | Commission selected strategy, optimise performance and integrate within production. |
Operation | Monitor and sustain performance within production. |
Results and Discussion
The following results represent a compilation of 32 Grade Engineering® evaluations performed across fifteen sites using the framework described in this paper. The following Table provides relevant information regarding the project, commodities, preconcentrationMethodologies used to separate gangue from valuable material. techniques examined, whether the evaluation considered the full or partial optimisation of the strategic mine plan and the change in the NPV for each preconcentrationMethodologies used to separate gangue from valuable material. option. The relative change in NPV is also displayed in the Figure below.
The evaluations are dominated by preconcentrationMethodologies used to separate gangue from valuable material. screening assessments and bulk ore sorting assessments. The results show a wide range of possible economic outcomes can be achieved with preconcentrationMethodologies used to separate gangue from valuable material. , including the fact that not all orebodies are amenable to certain preconcentrationMethodologies used to separate gangue from valuable material. techniques.
The average improvement in NPV was 12.8% across all preconcentrationMethodologies used to separate gangue from valuable material. techniques; screening techniques showed an average increase of 12.8% NPV and bulk ore sorting 17.0% NPV. Partial optimisation of the strategic mine plan yielded an average increase of 9.3% NPV, while a full optimisation returned 18.5% NPV. These results highlight the additional value from preconcentrationMethodologies used to separate gangue from valuable material. that is unlocked with a complete optimisation of the strategic mine plan.
The Figure below presents a boxplot of selected production and environmental metrics for twelve preconcentrationMethodologies used to separate gangue from valuable material. screening and bulk ore sorting options across six operations. Not all evaluations presented in the Table above have been examined for changes in environmental metrics.
The results show a wide range of outcomes in production and environmental metrics are possible. The impact that preconcentrationMethodologies used to separate gangue from valuable material. has on the quantity of ore processed and tailings and wasteMaterial determined to be below a predetermined grade or economic threshold. rock generated is often ambiguous. Significant increases in these metrics are possible with the expansion of the ultimate pit as a result of preconcentrationMethodologies used to separate gangue from valuable material.. Similarly, a reduction in wasteMaterial determined to be below a predetermined grade or economic threshold. rock is possible with increases in ore processed and tailings generated due to a significant lowering of the economic cut-off with preconcentrationMethodologies used to separate gangue from valuable material. and little opportunity to expand the ultimate pit. In all scenarios examined, preconcentrationMethodologies used to separate gangue from valuable material. increased the grade of ore treated and the total metal recovered from the orebody, indicating greater resource utilisation is achieved with preconcentrationMethodologies used to separate gangue from valuable material..
The results also show significant decreases in the energy, emission, water and steel intensity of metalliferousYielding or containing metal. production are possible with preconcentrationMethodologies used to separate gangue from valuable material.. These intensities of production represent the change in the energy, water and steel consumed, and emissions generated, relative to the production of a unit of metal output. On average, a 6% reduction in energy intensity, 8% reductions in emission and water intensities, and a 11% reduction in the steel intensity of comminution resulted from preconcentrationMethodologies used to separate gangue from valuable material.. These figures represent the inputs directly consumed by the operation and do not account for embedded energy, emissions and water in inputs consumed.
Furthermore, the results show that preconcentrationMethodologies used to separate gangue from valuable material. strategies were able to more than offset the increased energy, water, emission and steel requirements with additional metal production in scenarios where the quantity of ore processed significantly increased.
Preconcentration at Greenfield projects
Greenfields projects have greater flexibility to alter site layouts and adjust operational capacities to capture the full benefits provided by preconcentrationMethodologies used to separate gangue from valuable material.. However, there is less ability to trial and test preconcentrationMethodologies used to separate gangue from valuable material. techniques at Greenfield projects, often creating greater uncertainty whether to invest in preconcentrationMethodologies used to separate gangue from valuable material. strategies for Greenfield projects. In the results presented in Table 2, preconcentrationMethodologies used to separate gangue from valuable material. options applied to Greenfield projects returned an average increase of 16.1% NPV, while Brownfield projects returned an average increase of 11.2% NPV with preconcentrationMethodologies used to separate gangue from valuable material.. The largest increase in NPV from the 32 evaluations presented in Table 2 was also a Greenfield project (6C) and provides an excellent example of the additional benefits that can be achieved by altering site layouts and mine designs for preconcentrationMethodologies used to separate gangue from valuable material..
The project is evaluating the development of an intrusive-hosted, structurally controlled stockwork gold and silver deposit. The orebody lends itself to development as three open pits to be processed by SABC comminution, flotation, CIL and electrowinning circuitGeneral term for a collection of comminution/flotation equipment.s. The operation is processing constrained and stockpiles a significant portion of lower-value ore at a central location between the three pits. The stockpiled ore will be reclaimed and processed toward the end of the mine’s life.
Although the project is profitable, feasibility studies failed to achieve a threshold return for investment. preconcentrationMethodologies used to separate gangue from valuable material. techniques, including screening and dense media separation, were examined to improve the economics of the operation. natural deportment testwork from drill coreCylindrical "intact" rock taken for geological and metallurgical characterisation. samples across the three pits revealed a consistent, very high upgrade signature in finesSubjective term for the smaller sized component of feed throughout the orebody. Bulk samples taken from a mining adit through the main pit were screened and assayed to confirm the very high natural deportment response was present at ROMRun of mine PSD. Strategic mine planning used the natural deportment testwork to reoptimise pits, phases and site layouts with preconcentrationMethodologies used to separate gangue from valuable material. by screening. The study found:
- The optimal preconcentrationMethodologies used to separate gangue from valuable material. strategy sent high-grade ore directly to the processing plant and upgraded lower-value ore through the screening plant;
- preconcentrationMethodologies used to separate gangue from valuable material. enabled a significant expansion of the ultimate pits and increased resource utilisation;
- preconcentrationMethodologies used to separate gangue from valuable material. reduced the quantity of material processed via stockpiles and enabled the processing plant to be relocated to a central location between the three pits;
- Reducing annual material movement by 15%,
- Reducing cash costs and total costs by 10%, and
- Reducing implementation capex by 5%.
- While a reduction in process plant capacity could maintain a similar production profile with preconcentrationMethodologies used to separate gangue from valuable material., the significant increase in the quantity of economic ore mined warranted a processing plant of similar capacity, or slightly larger, to maximise NPV.
preconcentrationMethodologies used to separate gangue from valuable material. by screening improved the NPV of the project by 34% and has become the primary plan to develop the orebody.