How Bulk Ore Sorting Can Reduce Water and Energy Consumption in Mining

I was reading over a paper that was introduced at the SAG Conference last year. (Where are the Opportunities in Comminution for Improved Energy and Water Efficiency? Lane, Hille, Pease, & Pyle). The SAG Conference event brings together all those engaged in the field of autogenous, semi-autogenous and HPGR grinding in the industrial and metalliferous mineral industries.

The paper addressed how community attitude, the cost of energy, and the cost and availability of water have combined to motivate mining houses to consider ways of improving energy and water efficiency. According to the paper, there have been some recent significant shifts in the inputs that are used to select the most appropriate comminution circuit, where the ore is broken down into smaller fragments. The authors wrote:

“Both energy and water efficiency are potentially vastly improved by the application to the minerals industry of the emerging sensing and sorting technologies. First prize is to reduce the waste reporting to the first level of comminution through bulk sorting prior to or just after primary crushing, through shovel and bulk belt sensors.“

In a related publication, Wills’ Mineral Processing Technology [8th Edition, by Barry A. Wills, James Finch], the author notes that “Comminution consumes the largest part of the energy used in mining operations, from 30 to 70% (Radziszewski, 2013b; Nadolski et al., 2014). This has consequently drawn most of the sustainability initiatives designed to reduce energy consumption in mining, including for example, the establishment of CEEC (Coalition for Eco-efficient Comminution,) and GMSG (Global Mining Standards Guidelines Group).”

Bulk ore sorting can have a positive impact on these areas of concern. Ore sorting is a very broad concept that includes sorting by grade, particle size and mineralogy across many different mineral processes. Installing an online elemental analyzer enables early and accurate measurement of the grade of material being sent to the process plant and enables a decision to sort material that is below target grade and divert it to a low grade or waste stockpile. This enables a plant to divert or bypass material that is detrimental or not economically viable to the process and in doing so reduces the usage or water, power and reagents.

In a conventional flotation plant, up to 700L/t of water is needed for processing. Processing less waste and low-grade materials results in a reduction in the use of water, which can reduce water supply costs or operating costs of a desalination plant and the filtering of water at the end of the process. It also reduces the amount of water that ends up in a tailings dam.
Grinding and crushing of ore is energy intensive and accounts for approximately 3-5 % of the world’s power usage. Every ton of waste that is not processed reduces comminution costs and the associated wear and maintenance costs of the equipment.
Early waste rejection can reduce the processing plant and tailings dam footprint and capital.

In addition, ore sorting enables a plant to increase the average grade of ore being processed to maximize metal recovery. Declining grades can lead to revenue reduction if throughput is at a maximum. Traditionally, the solution has been to increase capacity to offset this through adding to the plant infrastructure by large capital investment. Bulk ore sorting has the potential to either delay or eliminate this capital spend, while delivering higher grade material to the mill. The increased recovery and profitability results in an extension of the mine life, increases the return on investment in the mine and delays costly site rehabilitation. So the potential benefits are far greater than the reduction in energy and water consumption alone.

For more information about how to develop a bulk ore sorting system using an online elemental analyzer or about PGNAA and PFTNA: