Commercial Ore Sorting > Ore Sorting Overview
Ore sorting solutions APPLICATIONS Ore sorting is a process for upgrading mineral bearing rock at large particle sizes, typically between 250mm and 10mm and involves evaluating the mineral content of individual rocks as they pass through a sensor then separating them into Accept and Reject fractions, based on pre-determined selection criteria. Ore Sorting requires a property specific to an ore to be sensed and then optimised for each application. Depending on the particle size range of the material being treated ore sorting machines can operate at throughput rates up to 200 tonnes per hour per machine It is possible to adjust machine sensitivity and the cut-off grade for the accept / reject split. This fine tuning gives flexibility to operating requirements e.g. high upgrade ratios or maximum recoveries. The crushed rock or gravel is screened into size ranges. Sorting devices work most efficiently when the size of the largest particles is no greater than two or three times the size of the smallest particle and there may be number of ore sorters in the process plant treating different size fractions.
METHODOLOGY Typically, automated sorting systems comprise:1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Material feed bin Vibratory feeder Free fall or mechanical acceleration Sensor Data processing Air compressor Air pressure valves - pneumatic nozzles Accept stream Reject stream Network interface for central control
Following screening, the material is spread evenly on a conveyor or inclined chute and passed t hrough a zone where properties of the rock, either natural or induced, are sensed. These properties most often involve low-level radioactivity or some property of light, such as reflectance or fluorescence, and other characteristics. For example; diamonds fluoresce when bombarded by x-rays, common salt reflects much light, uranium ores give off gamma rays, and x-ray absorption is directly proportional to atomic density. If a rock particle shows a high enough level of the sensed property, it is physically separated from the moving stream of rock usually by means of a powerful air blast, or an air operated flap. These “identify-and-flick” processes all happen in milliseconds and computers are essential to automated sorting. Typical sorting systems process material at rates of 500 to 1000 particles each second. Automated sorting is highly ore-specific, with different treatments needed for different minerals, and not all ores can be sorted with today's technology. The system illustrated below senses some property of each rock as it passes through the sorter sensors and uses highspeed digital processing to determine the amount of the desired mineral, then according to a pre-determined parameter accepts or rejects the particle.
INDUCTION SORTING Diagram of a STEINERT ISS Sorting System - increases the range of possibilities for sorting mixed materials
Amenability to pre-concentration For any form of pre-concentration to work, liberation of valuable minerals from the waste or gangue must occur easily during the crushing process. If the valuable mineral is finely disseminated throughout the ore, sorting o r other methods of pre–concentration may not be possible as it is necessary to reduce the ore to a size outside the range of coarse pre-concentration devices to liberate the valuable mineral from the gangue.
Fig 1 Coarse composite minerals
Here are examples of coarse mineral composites (Fig 1), and a finely disseminated ore (Fig 2) which illustrate this.
Fig 2 Finely disseminated minerals
X-RAY The STEINERT XSS X-Ray Sorting System - “Dual Energy” system to determine material density while overcoming the effects of thickness and shape
INDUCTION The STEINERT ISS Sorting System separates mineral ores from gangue to recover valuable metals
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