In our last post, the advantages and risks of performing high-energy blasts were reviewed and strategies to mitigate those risks were suggested. In this article, we review some of the techniques and technologies that can help harmonize upstream and downstream activities and take the mine-to-mill approach to the next level.
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Making the best use of ore reserves over life-of-mine (LOM) is becoming more important as mines today come to grips with a multitude of challenges that were not even on the horizon a decade or so ago. These include, but are certainly not limited to, coping with more complex orebodies at lower grades, adapting to changing environmental and social regulations and responsibilities, and meeting rising global demand for commodities within a volatile market. Fortunately, there are a number of novel techniques and new technologies that also were not on the horizon a decade or so ago that can help improve short- and long-term mining and processing performance.
Measurement while drilling (MWD)
Rock mass properties significantly impact the efficiency of drill and blast operations. Compared to laboratory-based characterisation techniques, Measurement While Drilling (MWD) technology, takes less time and is relatively less expensive, while allowing mines to obtain and measure real-time data on the rock mass in the process of blasthole drilling.
As a system, MWD monitors a range of parameters that reveal rock mass characteristics, including air pressure, feed pressure, percussion pressure, rotation speed, drilling rate, drilling depth, and torque. With this real-time data in hand, drill and blast engineers can respond quickly to changes in the rock mass and improve the reliability of their blast designs by tailoring blast energy for each individual blasthole.
Blast movement measurement and ore loss reduction
Rock mass displacement caused by blasting alters the coordinates of grade boundaries, resulting in ore loss and dilution, both of which impose significant financial losses.
Ore loss occurs when valuable material is misclassified as waste and sent to the waste dumps, which significantly reduces orebody utilisation and hence diminishes the overall value over mine lifespan. Ore dilution occurs when waste material is misdirected to the processing plant, where it degrades feed quality, lessens recovery, and results in huge losses in comminution energy by causing the process plant to grind uneconomical fractions of feed ores. Therefore, it can potentially impact operational and economical aspects of the whole value chain.
Blast Movement Monitor (BMM) is a technology developed and patented by the JKMRC, University of Queensland, used for measuring displacement directions. It consists of electronic transmitters placed within the blast volume before blasting which are then located after the blast with a special receiver. BMM technology provides 3D movement vectors in a reasonable time before start of loading.
Ore competence variability measurement
Despite the fact that breakage characteristics of ores vary, most of the current ore testing methods are average-based and therefore do not capture the variability with the sample. This can lead to unpredicted variation in process performance, which can cause unstable performance of grinding circuits, inconsistent fineness of grind, operation and optimisation difficulties, reduction in recovery, and reduction in classification efficiency.
Considering the impact of ore variability on process performance, it would be beneficial if mine-to-mill practices convert into ore characterisation techniques which are specifically capable of measuring and describing the extent of ore competence variability.
This potentially can enable minerals industry to better assess risks associated with equipment selection, process design, and optimisation strategies (Read More HERE).
Ore pre-concentration
Pre-concentration in mining attempts to improve ore-feed quality by removing low-value gangue material prior to the comminution process, which can potentially strategy reduce the energy input per unit of the final product.
Pre-concentration requires a suite of well-established techniques and technologies being utilized to exploit differences in physical and chemical properties of an ore to separate valuable minerals from gangue. Thus, depending on ore characteristics, a technique based on size, gravity, conductivity, competence, magnetic susceptibility, thermal reactivity etc., can assist with feed upgrade prior to energy-intensive size reduction stages. With recent advancements in the pre-concentration area, the approach should be considered in any mine-to-mill practice as a lever to improve or ‘unlock’ additional value (Read More HERE).
Scenario-based simulation
In today’s computer-aided product development and manufacturing environment, designers and engineers are using a wide range of software tools to design and simulate their products. In mining, constraints-based simulation can improve understanding of the interaction between key stages across the value chain in a quantitative manner, while at the same time accounting for operational constraints and bottlenecks. This helps mines make informed-decisions and develop optimal strategies for improving long- and short-term mining and processing performance, thereby mitigating risks associated with CAPEX and OPEX.
For example, mine-to-mill practice requires optimising blast fragmentation in favour of milling, which may require testing a combination of several input variables (blasthole diameter, burden, spacing, explosives properties, etc.), each of which may vary within a range. Technologies such as Dassault Systemes’ SIMULIA can reliably optimise blast design for a specific outcome e.g. degree of fragmentation, in a reasonable time (e.g. ~ 1000 scenarios per minute) by combining cross-disciplinary models and applications together in a simulation process flow, automating their execution, and identifying the optimal design parameters subject to required constraints (Read More HERE).
Conclusion
Minerals industry can now access a variety of techniques and technologies to improve short- and long-term mining and processing performance. In turn, these techniques and technologies can help mines harmonise their upstream and downstream activities and make the mine-to-mill approach even more successful.
In our next article, we focus on grade control as a critical strategy that should be considered as part of future mine-to-mill practices, and specifically discuss how the issues of ore loss and ore dilution induced by blasting can be addressed using a GEOVIA solution.
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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