Comminution

The future mine leverages advances in ore pre-sorting and comminution technology to substantially reduce the energy footprint. Comminution accounts for a significant portion of energy use in a typical mining operation. A study published by the Coalition for Energy Efficient Comminution indicated 25 percent of total energy consumption for a typical mine is consumed by this circuit. Hence, improvements in comminution technology can have significant impacts on energy use and emissions.

Novel Comminution technologies

Various comminution technologies are available and in different stages of development, some of which promise significant energy savings.

Current focus:

• Mine-to-mill (bulk ore sorting systems)
• High pressure grinding rolls (HPGR) and stirred milling
• Blast fragmentation

Short term focus:

• Flexible circuit (HPGR, stirred mill)
• VRM (vertical roller mill)

Long-term focus:

• Dry grinding mills (EDS, VeRo, etc.)
• Underground processing

Our team is experienced in the assessment and fundamental understanding of novel comminution technologies, with a history of pilot and lab scale modular circuit operation and optimisation. We can leverage technology and simulation software to create models and simulations of novel equipment and their integration into circuits. Our mine-to-mill simulations optimise for NPV and minimised emissions.

We can provide:

• Mine-to-mill and mine process value chain simulations, including preconcentration options
• Option life-cycle impact comparisons
• Comminution circuit simulation and optimisation.

In addition, our minerals processing experts can design test work to support definition of optimum grind-size to minimise power consumption whilst maximising recovery, and minimising tailings water entrainment.

Reduced comminution through alternate processing options

Alternate processing circuits can be considered based on ore characteristics to significantly reduce grinding and associated energy requirements. Options can include:

Leaching involves dissolving the acid soluble portion of the target mineral out of the ore to extract the value. This approach can be applied to run-of-mine (ROM) stockpiles (dump leach) or crushed and agglomerated ore stacked in multi-lift heaps. In select cases the dissolving of target mineral into solution can take place in-situ by pumping weak acid or other lixiviants into the group though injection wells and collecting the enriched solution for processing, without mining the ore. Benefits include:

• Sustainable use of resources, through reduced energy use (not reliant on comminution), lower water consumption (compared to milling) and minimal greenhouse gas emissions
• Reduced carbon emissions footprint and costs from not shipping concentrate (containing ~10 percent water).
  

Ore sorting can support improved project economics where the run of mine ore contains dilution, or where there is a cost benefit of rejecting low grade ore prior to processing. Ore preconcentration can be investigated for both greenfield and brownfield projects to maximise asset value and NPV. For more detail on our experience, see Separation, Sorting and Recovery. 

Coarse particle flotation targets a reduction in upfront grinding power by rejecting waste minerals in the first flotation stage. This needs to be done with consideration of minimising process complexity and mass recovery to the coarse particle flotation concentrate, and the need to achieve an equivalent level of cleaner stage mineral liberation as a conventional flotation circuit. Often these critical aspects are overlooked in consideration of practical implementation of coarse particle flotation:

1. Benefits in upfront grinding power are certainty possible but to achieve an overall benefit requires sound testing and trials and robust flowsheet design
2. Coarse particle flotation usually means that lower-grade composite particles are being floated which leads to higher mass recovery 
3. Failure to achieve sufficient mineral liberation at the cleaner flotation stage is expected to effect concentrate quality and possibly marketability of the product
4. Coarse particle flotation may have a stronger case for application as an alternative ore pre-concentration stage.

Emerging comminution technologies are making their way into the minerals industry. Significant grinding energy is wasted by current comminution equipment in breaking rocks to finer particle sizes than the target grind size. Emerging technologies are focused on reducing the number of finer particles generated and quantity of oversized rock bypassing comminution by targeting breakage energy to rocks that are considered oversize.