Several thought-provoking new papers have been published recently, including:
- ‘Value driven methodology to assess risk and operating robustness for Grade Engineering® strategies by means of stochastic optimisation’.
- ‘Managing uncertainty in a Grade Engineering® industrial pilot trial’.
- ‘Application of Enterprise Optimisation Considering Grade Engineering® Strategies’.
Read on to find out more about these papers or to access a copy. We’ve also included the abstract of a thesis submitted for assessment by PhD student, Cristián Carrasco.
Assessing risk and operating robustness for Grade Engineering® strategies
October 2016: The introduction of new value-adding technology onto a mine site, brings with it an additional layer of complexity. A new paper published in Minerals Engineering demonstrates how the complexities associated with size based Grade Engineering® are being managed for effective operational deployment.
The paper is based on a case study of the introduction of two size based Grade Engineering® levers on a large open cut copper porphyry deposit. It looks at management strategies deployed during implementation and demonstrates that size-based Grade Engineering® is a robust operating option that can effectively deliver significant improvements in unit metal productivity.
The paper was authored by CRC ORE’s Process Engineer, Cristián Carrasco, and General Manager – Implementation, Dr Luke Keeney, Dr Michael Scott, Project Evaluation Specialist, together with Prof Timothy Napier-Munn of Julius Kruttschnitt Mineral Research Centre (JKMRC).
Managing uncertainty in a Grade Engineering® pilot trial
October 2016: A new paper on the concept of managing uncertainty has been published, presenting a methodology to identify, quantify and assess the different sources of uncertainty within a Grade Engineering® (GE) trial.
Published in the Minerals Engineering Journal, the paper presents a novel approach to aid the optimisation and development of coarse separation control strategies through the understanding of the extent, variability and uncertainty of metal deportment inputs.
The paper was authored by CRC ORE’s Process Engineer, Cristián Carrasco, and General Manager – Implementation, Dr Luke Keeney, together with Prof Timothy Napier-Munn of Julius Kruttschnitt Mineral Research Centre (JKMRC) and Dr Dominique François-Bongarçon of AGORATEK International Consultants Inc, Canada.
Enterprise Optimisation Considering Grade Engineering® Strategies
5 September 2016: CRC ORE and Whittle Consulting have published a study on enterprise optimisation using Grade Engineering® strategies, which is now available for download.
The synergy between Grade Engineering® principles and Enterprise Optimisation was assessed through a case study that examined potential Grade Engineering® techniques using advanced modelling across the entire value chain, in a hypothetical, but realistic, mining operation.
With the publishing of this study, the collaborators demonstrate the ability of Enterprise Optimisation approaches to evaluate and fully value the principles of Grade Engineering® coarse-separation techniques. The case study examines potential responses for three coarse separation techniques across different domains in a hypothetical, but realistic, mineralised deposit underpinned by CRC ORE’s historical work with actual operations. The results from this work provides a basis for understanding the value of collaborations in Grade Engineering®, strategic mine planning and operational optimisation, with the support of mining operations and projects.
A copy of the paper can be downloaded here.
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|CRC ORE PhD student Cristián Carrasco has submitted his thesis to the Julius Kruttschnitt Mineral Research Centre (JKMRC) for assessment.
Cristián Carrasco submits PhD thesis
September 2016: CRC ORE PhD student, Cristián Carrasco, recently submitted his thesis for assessment. His paper concentrates on mining engineering and process/production control and simulation. The abstract of his thesis is below.
Abstract: Integrated Assessment to Quantify Size Based Grade Engineering Operating Strategies and Economic Impacts, Cristian Carrasco.
The global mining industry is focused on improving unit metal productivity and energy efficiency to fulfil increasing demand for natural resources. These are currently being impacted by the dramatic decrease in average grade of mine ore bodies. Lower head grades require greater comminution and grinding energy intensity to achieve the liberation target required for downstream processes. Size based Grade Engineering® aims to increase feed grades by removing low grade uneconomic material through screening prior to energy intensive grinding. Two size based strategies are assessed in an open cut Cu-porphyry deposit in the current study: preferential grade by size deportment and differential blasting for grade. The former refers to a natural based rock phenomena whereby a significant metal proportion preferentially deports into specific size fractions after breakage. Differential blasting aims to change blast product fragmentation to induce grade by size deportment through the exploitation of spatial grade heterogeneity. This characteristic relates the presence of high and low grade areas within a certain production volume originally assigned to a single processing destination based on its average grade. These size based separation drivers are subsequently exploited through a Grade Engineering® circuit. This comprises a set of screens and crushers, with a configuration and operating settings defined a Grade Engineering® recipe.
While assessments at a strategic level indicate that application of size based Grade Engineering® strategies are able to add significant value over the life of mine, the effective deployment of these techniques at production level present significant challenges to the standard operating philosophy. The additional operating flexibility driven by the ability of dynamically exploiting size based levers through the appropriate Grade Engineering recipe need to be properly managed. This ensures that size based Grade Engineering® benefits can be achieved at the production environment. An integrated value driven methodology has been developed to manage complexity incurred by the dynamic approach by incorporation in process models coupled with stochastic optimisation. This allows the optimum Grade Engineering® recipe to be determined maximising the value per unit of time that can be drawn from a production volume. This framework addressed two fundamental characteristics pertaining to production scale evaluations. Firstly the non-linear interaction between rock based attributes and operating parameters through the integration of JKMRC performance models within the Grade Engineering® circuit. Secondly, the presence of inherent process uncertainty and its impact in process optimisation. The introduction of uncertainty in the stochastic optimisation problem enables the assessment of risk and operating robustness, both essential in robust decision-making processes.
This was achieved by integrating multiple and diverse methodologies developed in this thesis, encompassing:
- The development and application of a mathematical model to describe preferential grade by size deportment through a response ranking (RR). This parameter has been extensively employed to characterise the aforementioned phenomenon across different geological style deposits (i.e. stock work vein hosted, Cu breccia porphyry and Cu volcanic porphyry) and sample size scales (i.e. drill core and ROM samples) described in this work.
- First order assessment of operating impact associated with exploitation of preferential grade by size deportment through a novel visualisation method. This clearly reveals that size based separation opportunity is not merely a function of RR magnitude but also relies on head grade, proportion of material upgraded in the undersize (i.e. referred as mass pull) and defined material processing destination.
- The development of a coarse liberation model to integrate RR into equipment performance models, essential in process optimisation. This allows to take into account the interaction between particle size distribution and RR. This approach comprised extensive ROM sample characterisation through a novel preferential grade by size characterisation test and sophisticated data analysis techniques.
- The derived attributes pertaining to preferential grade by size validation at industrial scale were employed to characterise the likely production uncertainties associated with an eventual Grade Engineering® application. A linkage between RR values and inherent geological variability can be determined. Information gathered during the trial also provided inputs in the further stochastic optimisation assessment.
- The assessment of the impact of modified mill feed particle size distribution due to application of Grade Engineering® strategy through simulation. This was achieved by employing a factorial design approach coupled with mass simulation capabilities embedded within the Integrated Extraction Simulator (IES), a new cloud based process simulator.
- A stochastic optimisation methodology encompassing application of the simple average approximation technique coupled with a customised genetic algorithm. This enables the appraisement of impact from changes in available mill capacity upon value drawn from optimised Grade Engineering® recipe. An operating robustness factor was developed to mimic relationship between maximised value and confidence level of achieving a defined operating constraint.
Interactions between the two distinctive size based strategies as well as synergies with throughput based approaches (i.e. Mine to mill) can be simultaneously assessed from value, risk and operating robustness perspective.
New paper on coarse liberation released
12 December 2015: A new paper on the concept of ‘Coarse Liberation’ has been published, highlighting a novel test work and data analysis approach to develop a statistically robust coarse liberation model by using grade by size information across different geological deposit styles.
The thought leading paper was the result of extensive analysis, including bulk samples from three different geological style deposits, which has provided useful insights into developing an optimum coarse separation circuit flowsheet design for pre-concentration prior to energy intensive and inefficient grinding.