Pre-concentration of ore

As ore grades deposits are reducing, increasing volumes of material have to be mined to meet market demands. This is leading to increased costs, energy and water consumption in mining, transportation and processing. We can work with you to sort the ore early in the process and minimise re-handling, mixing & transportation costs.

The future of In-Pit Operations

Pre-concentration is the rejection of gangue (barren material) from coarse ore feed. It increases the grade of the ore early in the mining process and avoids feeding the plant with material that will cost more to process than its worth. Hence, less tonne of ore are treated per tonne of product. This has a number of down-stream benefits such as: less energy in grinding low-value, larger size material, reduced tailings, and improved recovery. This ultimately reduces costs, energy and water consumption.

Pre-concentration significantly improves the value of the resource by upgrading below cut-off grade material and/or increasing production rates per tonne of material treated. There are several technologies that may be applicable for pre-concentration including:
gravity processes, magnetic separation, sensor based ore sorting (SBOS) and screening. The suitability in each case depends on the properties of the ore.

Pre-concentration improves profitability

Screening

Valuable minerals are often softer or more friable than gangue minerals and are hence concentrated in the fine size fractions after initial breakage stages. If the ore exhibits a grade by size relationship screening can be an effective method of pre-concentration. Screening is simple, has high capacity, low cost and low technical risk.

Sensor-based bulk ore sorting

Where the grade by size relationship does not allow effective separation it may be possible to achieve an upgrade using sensor based ore sorting (SBOS). SBOS relies on one or more sensors measuring the ore on a conveyor. A mechanism at the end of the conveyor diverts the ore stream to one of two directions depending on the grade of the ore, based on a cut-off value. A variety of sensors are available that measure different properties of the ore, the most common being photometric, electromagnetic, radiometric and x-ray.

To be practical in pre-concentration applications for large-scale mining operations the measurement process needs to penetrate the entire bulk of the ore and be almost instantaneous. Ore sorting benefits from the natural heterogeneity of deposits and should be implemented as early in the process as possible, where the variability is greatest, to maximise the benefits.

Gravity separation

Pre-concentration with gravity processes requires a distinct density difference between the ore and gangue minerals at fairly coarse sizes. Finely disseminated ores are generally not suitable, as the density difference only becomes apparent when the particles are finely ground. Dense or heavy medium separation (DMS or HMS) is the most efficient gravity concentration options available, suitable for a wide variety of ores at a relatively low capital and operating cost, and should be considered during the design phase for new concentrators. However, many low-grade ore bodies may not have sufficient density difference at coarse sizes for effective separation.

Improve resource utilisation

The cut-off grade in the mine may be decreased, and mineral reserves increased.

Increased feed grade

By upgrading the plant feed

Reduced costs

Lower operating and capital costs

Improved recovery

Higher feed grade improves grade-recovery performance

Increased production

More product per tonne of ore treated

#Conveying the future

 

To produce metals, minerals, aggregates and energy for today’s global needs, the mining industry must handle huge volumes of material, sometimes move entire mountains. Today, mines are being challenged to re-think how they can remain profitable and be socially and environmentally responsible moving into the future.