An overview of the Global Comminution Collaborative

  • By Professor Malcolm Powell FAusIMM, JKMRC, Sustainable Minerals Institute, the University of Queensland

A collaborative research team that brings together expertise from around the world to address industry challenges

‘As a networked group spanning the globe we can develop an outstanding capability in the field of comminution research and practical delivery well beyond our potential as individual groups.’

This vision drove the formation of a rather unique collaborative involving six applied research groups in universities across five continents.

The Global Comminution Collaborative (GCC) was established by Professor Malcolm Powell of the University of Queensland in 2012 to address the challenges of sustainable comminution in the mining industry. The GCC has connected world-leading comminution groups from Australia, Brazil, Germany, South Africa, Sweden and Turkey in a level of collaboration that has never previously been achieved within the mining industry research sector. The group conducts industry-focused research to improve the efficiency of the comminution process.

Global Comminution Collaborative members (L to R): Malcolm Powell, Arno Kwade, Magnus Evertsson, Aubrey Mainza, Marcelo Tavares, Hakan Benzer.

The processing of hard, low-grade and fine-grained orebodies is requiring the global mining industry to focus on the increasing cost of comminution. The GCC is at the forefront of addressing the technological challenges this is posing to the industry, sharing best practice and providing sustainable and environmentally sound solutions alongside world-renowned expertise.

The specialist area of comminution in aggregate and mineral processing has few dedicated researchers worldwide, due to limitations in funding and available skilled personnel. It is our contention that we cannot afford to compete, as we individually lack the resources to deliver what industry requires. To meet the research needs within existing constraints we must pool our resources, bringing together our complementary skills and experience, and enable worldwide delivery to industry. The GCC brings critical mass to comminution research and application through linking leading research groups from around the globe into a coherent collaborative that can span the full range of size reduction processes. These cover a range of required skills along the process chain and across the skills base such as crushing, high pressure grinding rolls (HPGR), dry processing, milling, mechanistic modelling, ore breakage characterisation, classification, fine grinding, circuit design, dynamic simulation and process optimisation. The group conducts industry-focused research to improve the efficiency of the comminution process while meeting the design needs mandated by large, low-grade orebodies.

As a collaborative we aim to deliver to industry:

  • knowledge to implement best practice plant performance through on-site review and research
  • accurate models of process equipment, able to respond to ore variability, for design and optimisation, including incorporation of liberation into process models
  • meaningful ore characterisation tests
  • circuit design studies – including incorporating new and novel equipment
  • minimisation of energy use through improved comminution equipment, process design, classification – especially to minimise overgrinding and, importantly, presenting product streams in suitable size ranges for staged recovery
  • targeting lower water use via dry processes and minimising overgrinding.
  • As university research groups, we offer a supportive, technically outstanding collaboration group that:
  • develops to our potential of producing top research outputs on challenging and interesting topics
  • delivers the best outputs on the wide front of comminution skills needed by the worldwide mineral processing industry
  • mentors a new generation of highly competent researchers.

Critically, the group has a trust in each other and enjoys working together. This underpins the desire and benefits of the collaboration where all parties are equal. This distributed network allows for shared research and funding to move between institutes.

Integration within the mining chain

Although focused on specific specialist areas of the mining chain, we actively strive to integrate upstream and downstream in the mining process so as to identify and utilise the best opportunities for the mineral extraction process as a whole. We are thus pushing upstream to work in the geometallurgy arena to characterise the response of the rock to a systematic series of treatment processes. We then link with mining on opportunities for early recovery and waste removal, along with reduction in comminution energy requirements. We aim to be integral to the design and operation of the concentration step in tuning the presentation of the liberated particles to downstream processes. Improved understanding to how the many components in an orebody respond to the breakage and classification processes is essential. We aspire to tailoring comminution products to minimise downstream impacts, eg excess generation of fines and acid-generating species that influence water recovery and pollution, and potentially increase the capability to extract more from the ore.

GCC conducting site reviews in different countries.

Operation

The GCC multiplies local access to international expertise via a direct conduit with a single point of contact.

Access to the entire GCC network is available via any of its members. When contacted by a company, they can be directed to the best skill source in the collaborative or the contact can assemble an appropriate team to tackle the production issue or research challenge. This greatly simplifies the sourcing of expertise and project management for a company, whilst also providing a local contact to liaise and facilitate implementation.

Playing to our strengths

The GCC is able to take a broad perspective when defining the problem or challenge in concert with the mining company. The GCC then gather a team to review the site and identify opportunities in close partnership with site personnel. Through this process, the group capability is leveraged for maximum returns on our linked capabilities. We then provide a staged approach to provide rapid feedback on the low-hanging fruit that steadily builds into more substantial and deeper benefits. An optimisation study for an operating site may include:

  • site review – to audit and identify process improvement opportunities and performance issues with a clear course of action to address them
  • measure key process flows, size distributions and data signals that can provide further insight
  • review six to 12 months of historic process data to calculate utilisation, overall equipment effectiveness (OEE), equipment efficiency, identify control bottlenecks, etc
  • complete targeted surveys of the plant to model the process and measure key responses at the required fidelity
  • provide quantitative process prediction of the impact of changes linked to an implementation plan, as well as support to implement
  • dynamic process simulation – process twinning to test process control strategies in response to ore variability.
GCC conducting site reviews in different countries.

High-return challenges – uncovering hidden opportunities in existing circuits

The linking of highly skilled and specialised applied researchers has highlighted the hidden value between equipment in circuits. The coupled interaction of units along a process chain that have quite different responses to ore feed size and competence makes process control challenging, as feed varies in the short- and long-term. Matching screens, crushers, HPGR, belt capacities and top-size feed to a mill is one such example that the GCC tackled at the Anglo American Mogalakwena North Concentrator operation in South Africa.

As published in Powell et al (2011; 2012), the plant suffered from a number of design constraints that the GCC team identified as allowing opportunities to expand production. Materials handling issues included asymmetric feed to the crushers, segregation in bin feeds leading to under-utilisation of bin and screen capacity, oversize feed to the HPGR that limited operating pressure, surging on screen feed leading to overloading of a critical conveyor, and a fixed speed HPGR that removed its capability to respond to feed changes. All of these factors limited circuit throughput and increased final product size being fed to the ball mill which, as the throughput increased, would become the next bottleneck to production. The increase in capacity hinged on key design modifications based on discrete element method (DEM) simulations along with new approaches to process control. The site achieved the predicted 20 per cent increase in throughput and is now well on its way to implementing changes to achieve the next 20 per cent increase without any additional comminution capacity.

A high-quality simulation of all the relevant equipment provides a route to confidently size the equipment for an expansion, as well as to trial a wide range of potential design and circuit layouts. Enhanced steady-state simulations using updated models allowed for crusher capacity and some aspects of the circuit dynamics to be modelled. The simulations showed that the addition of two tertiary crushers and a double deck screen (along with the required bin and conveyors) would allow the circuit to expand by 70 per cent from the original throughput. Dynamic simulation adds the capability to specify storage capacity and to trial circuit operation in terms of operating strategy. This is achieved by overlaying the control system on the dynamic simulator.

In this applied example, the opportunities lay in no individual piece of equipment, but in the linkages and interactions of the integrated process.

Industry uptake of new technology

Production-relevant technology can be developed in parallel with production improvement studies, providing a route to rapid implementation of identified opportunities while assessing and valuing more substantial upgrades through advanced modelling and process prediction. Gains from early research delivery can justify the deeper investigation of medium-term improvement opportunities, including deeper understanding, upgraded models and on-the-fly model validation. This approach of the GCC demonstrates the potential benefits of nurturing research groups to build a strong interdisciplinary technical team that can support operational needs while developing future technologies.

Digital process twinning – a future challenge

We have observed that process dynamics and materials handling are major limitations to optimal performance. These influences are exacerbated by dry processing, sorting and upgrade, and new types of equipment, all of which introduce unknowns into comminution circuit control.

Ore is naturally variable, so dealing with variability is intrinsic to the mining industry. However, plants are designed to average steady-state demand with a contingency for higher needs added to certain pieces of key capital intensive equipment. This may provide some de-risking of design, but does not unlock the circuit potential.

Different equipment that is placed sequentially in a circuit (and often in closed circuit with recirculating loads) has different residence times and process lag. Additionally, ore type can differentially affect this equipment: some responses are linear while others are non-linear, some are sensitive while others are insensitive to feed size or competence. As the process units are fixed, the output varies in response to the varying input. This response is non-linear and non-intuitive in a circuit.

GCC conducting site reviews in different countries.

The GCC has embarked on an initiative to transfer all our process modelling capability to a dynamic basis that operates in a real-time scale. This can be built into a ‘digital process twin’ to mimic the operation of the real plant to be used for process design, developing control systems and training operators. This will be applied to the following challenges:

  • designing for dynamics – positioning of buffers and excess capacity to deal with varying demands on equipment
  • control – testing control algorithms and providing training of control systems by running the full control system on the digital twin
  • maintenance – the digital twin can provide realistic responses to both planned maintenance and unplanned breakdowns to inform optimal scheduling and de-risking
  • training – operators, metallurgists and managers can receive and provide training on control response with a realistic virtual plant emulator.

The GCC approach will transcend current black box ‘dynamic’ approaches by drawing in more mechanistic models that are built upon the best steady-state knowledge with added real-time dynamics. These will use real equipment configurations (such as the wearing of mantle shape in a crusher or pebble ports in a semi-autogenous (SAG) mill), utilise breakage response based on valid ore characterisation tests, include realistic transport dynamics through the equipment and include bins and conveyors as modelled process equipment to complete circuit simulations.

The spectre of materials handling shortcomings leading to issues such as size and density segregation, uneven wear, vibration arising from uneven loading (such as crushers and HPGR), and poor utilisation of equipment (such as screens and bins) is being addressed by associated physical modelling of materials flow and handling. Through addressing the massive flows of material around a production circuit and the dynamics of mineral processing, and through live digital process twinning, the GCC aims to help raise the comminution effectiveness of our industry to the next level.

Members of the GCC

University of Queensland, SMI, JKMRC (Australia) – Professor Malcolm Powell: A world-recognised comminution expert, providing the big picture and integration tools through multi-component simulation, process modelling, flexi-circuit concepts, liberation, novel circuits, applied ore processing and energy measures.

Hacettepe University (Turkey) – Professor Hakan Benzer: Dry processing including HPGR, roller mills and classification.

Federal University of Rio de Janerio (Brazil) – Professor Luis Marcelo Tavares: Most advanced mechanistic comminution modelling and breakage testing and specialisation in iron ore processing.

Chalmers University of Technology (Sweden) – Professor Magnus Evertsson: Most advanced crusher modelling in the world, dry screening, dynamic simulation, applied crushing circuit control.

University of Cape Town (South Africa) – Professor Aubrey Mainza: Classification, run-of-mine ball/SAG mills, the world’s highest resolution positron emission particle tracking (PEPT) facility used to measure particle motion inside devices, DEM modelling, process modelling and applied process simulation.

Technical University of Braunschweig (Germany) – Professor Arne Kwade: The world leader in modelling fine particle breakage – bringing this expertise into the minerals industry.

 

References

Powell M S, Benzer H, Mainza A N, Evertsson M, Tavares L M, Potgieter M, Davis B, Plint N and Rule C, 2011. Transforming the effectiveness of a HPGR circuit at Anglo Platinum Mogalakwena, in Proceedings International autogenous and semiautogenous grinding technology 2011 (eds: Flintoff et al), (Canadian Institute of Mining, Metallurgy and Petroleum).
Powell M S, Hilden M M, Evertsson C M, Asbjörnsson G, Benzer A H, Mainza A N, Tavares L M, Davis B, Plint N and Rule C, 2012. Optimisation opportunities for HPGR circuits, in Proceedings 11th Mill Operators Conference, pp 81-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

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