In our last article, we highlighted several accessible technologies and techniques that could be integrated into mine-to-mill practices to gain additional value in both the short- and long-term. We are now concluding our mine-to-mill technical series by focusing on grade control as a critical strategy that should be considered as part of future mine-to-mill practices, and suggest a solution to tackle ore loss and ore dilution induced by blasting.
The challenge of ore loss and dilution induced by blasting
Rock mass displacement caused by blasting alters the coordinates of grade boundaries, resulting in ore loss and ore dilution.
Ore loss occurs when valuable material is misclassified as waste and sent to the waste dumps, diminishing the value of the mine over its lifespan. Ore dilution occurs when waste material is misdirected to the processing plant, where it degrades feed quality, lessens recovery, and wastes comminution energy by causing the process plant to grind uneconomical fractions of feed ores.
Key requirements for minimizing risk of blast-induced ore loss and dilution
Ensuring that the processes that define grade control are efficient and repeatable is critical to driving profitability.
Grade-control capabilities are an integral part of GEOVIA’s Surpac™, which means we can help you implement new and improved grade control procedures at any stage in the lifecycle of a mine, and develop strategies for dealing with ore loss and dilution induced by blasting.
In the blasting realm, a sustainable grade-control strategy requires well-developed pre-blast and post-blast strategies, including measurement, modelling, optimisation, and value quantification.
The extent to which a design would be capable of delivering desired outputs in different geological domains depends on how well the heterogeneous nature of ore domains is captured by a model. To efficiently address a complex problem such as ore loss and dilution, a solution should be sophisticated enough to allow engineers and specialists to continuously improve their understanding and their designs based on measurements produced in a timely and integrated manner.
Strategic assessment and control of ore loss, dilution and recovery is an engineering solution specifically developed for continuous improvement and long-term gains. The solution includes three key stages of mapping data and 3D visualisation through block- and grade-control models, mass simulation and optimisation, and strategic value quantification.
Stage 1: Measure & Visualise
Stage 1 deals with resource modelling and field measurements – i.e. blasthole assays, bench-scale grade control model, material classification, Measure While Drilling (MWD) and Blast Movement Monitor (BMM) data, as well as blast-design parameters.
Any type of data collected can be integrated and used for 3D visualisation, design improvement, and analysis. The input data can express drilling penetration rate, grade, geo-mechanical indices (UCS, Young Modulus, Joint Density, etc.) or geo-metallurgical including grade, mineralogy, ore hardness (BWi), ore competence (SPI or Axb).
- This allows blast engineers to visualise pre-blast grade boundaries within the block and their post-blast coordinates after movement, and to evaluate heaving performance.
Stage 2: Simulate & Optimise
Stage 2 produces constraint-based scenarios through a massive simulation of combinations of variables in light of grade-control model and field information. Analysis of these scenarios identifies optimal blast-design alternatives for different geological domains while respecting design and operational limits.
- This stage allows specialists to establish expert-based strategies by comparing pros and cons of best design alternatives in a reasonable timeframe (~1000 scenario per minute).
Stage 3: Quantify Value & Maintain
Stage 3 is the strategic assessment of potential gains and losses from grade-control strategies adopted in the upstream.
- This stage allows specialists to quantify the effect of simulated strategies expressed in terms of Net Present Value (NPV).
The ‘strategic scenario-based analysis’ below implies how ore dilution and ore loss could potentially diminish or improve NPV of a copper mine.
As it is shown, the metal yield and recovery significantly impacts NPV. The result highlights the importance of being able to evaluate the impact of grade control strategies at upstream and downstream stages at a strategic level and monitor their impact on the overall value over LOM.
Conclusion
The solution developed at Dassault Systèmes uses globally-trusted, multi-functional software packages that are also capable of dealing with blast-induced ore loss/dilution problems. The workflow below illustrates key steps critical for mitigating risks associated with poor blasting – i.e. ore loss/dilution.
The step-by-step workflow summarises the solution and details how such technologies help address ore loss and dilution problems pragmatically for sustainable gains.
Should you have a project to optimize your mine to mill approach or you are interested in learning more about the potential outcomes in your context, get in touch with our Services team to discuss about your project: GEOVIA.Info@3ds.com
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About the expert
Farhad FARAMARZI is a Senior Mining Industry Consultant at GEOVIA Dassault Systemes with over 10 year experience in Research, Consulting and Industry. Farhad holds BEng, MEng in Mining, and is specialised in Drill & Blast optimisation. He has worked in Drill & Blast specialist and superintendent positions - designed, led and surveyed over 100 full-scale production blasts at some large iron and copper open-pit mines. Farhad’s main area of expertise was built during his PhD in the Mineral Processing field at the Julius Kruttschnitt Mineral Research Centre (JKMRC) where he broadened his skillset and specialised in ore breakage characterisation, performance improvement, value-chain optimisation, modelling and simulation with several accomplished projects for Anglo American & BHP in this space.
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