Saturday, 24 July 2010

What is the future for electronic sorting?

Optical and other forms of electronic sorting have always been processes with potential, but have mostly been mineral processing techniques with limited use, apart from important applications on some specific ores, such as diamonds.

However, Oliver Peters, of Metpro Management, Canada, feels that optical sorting (including XRF analysis) is becoming increasingly popular. He writes in LinkedIn "I am  currently working on a project that  relies pretty much on the separation of three ore types prior to grinding in order to be an economic project. Big advancements have been made in optical sorting over the past few years and they are starting to be a real practical process option. The throughput is still somewhat limited in that each machine can process the equivalent of t/hr based on feed size in mm i.e. at a feed size of 20 mm, a sorting machine can process approximately 20 t/hr. To my knowledge there are now 7 different type of sensors that are being used in sorting applications. Some details will be available in the new Ullman publication, which is scheduled to be released later this year."

Ron Fickling, of Metanga Mineral Processors, South Africa, comments "Optical Sorting (using cameras) can be limited by the requirement to have consistent light source and surface moisture content. In some tests, about 5 years ago, using the same ore sample the mass split between concentrate and discard varied by up to 30% on different days.  I think that sensors such as XRF, XRT, EM etc will produce more consistent results unless there is a significant colour difference."

Let's have your views on this interesting area, which will form part of the scope of next year's Physical Separation '11 conference in Falmouth, UK.

8 comments:

  1. Great subject, Barry! May I suggest to call this new site:"What is the future for machine sorting?". Sorting by light, or X-rays, or microwaves, or even magnetics may use electronics for processing, but not for sensing. The essence here is the contrast with hand sorting.
    Gus Van Weert, University of British Columbia, Canada

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  2. I believe that sensor-based sorting will eventually become another established technology in the toolbox of a mineral processing engineer. While a limited number of sensors and computing power placed severe restrictions on the throughput of these machines in the past, modern sorters can now process up to 40,000 particles a second. Further, more than half a dozen sensors are now available. As with other pre-concentration technologies, it won't work on every deposit and it will have to be evaluated on a project by project basis. I'm presently working on a project in Europe that has a very challenging metallurgy and based on my experience with a similar material this project will likely not be economic without some form of pre-sorting.
    Oliver Peters, Metpro Management, Canada

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  3. what about the size limits of the material to be sensor for preconcentrate the mineral?. I am thinking on tin mineral (1.7% Sn)
    jorge lema patino, Bolivia

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  4. The lower practical limit for mechanical sorting is around 12mm and the maximum size is ~250mm. While the minimum theoretic size is 1-2 mm, the throughput would be too low (plus the rejection rate would suffer due to the need to remove the fines in preparation for the sorting). In that case, gravity separation may be a more suitable approach.
    Oliver Peters, Metpro Management, Canada

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  5. Indeed, 1-2mm in high value ores such a diamonds or a metal laden slag makes sense. Up to 250mm possibly separating interburden from coal is another application. It is typical that separations at 6cm to 8cm approach an "optimal" separation size for many vein and stockwork type ores. If there is any true problem it is in the need for multiple machines if attempting to sort for large mining projects, i.e., more than 10ktpd+++.

    R. W. Jolk, P.E., Commodas Sorters US

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  6. I'm not a mineral processing specialist, just a humble geo, but have just returned from the Russian far east, where one of the sites I visited was Tokur. Owned by Petropavlovsk plc, it is a dump reprocessing operation. Uses X-ray sorting to produce gold concentrates from gravel sized dump material. They have been doing this successfully for over a year. Very impressive and low-cost operation. Apart from the X-ray detector itself, basically a simple low-tech system. Selection is essentially on detection of sulphides in the surface layers.

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  7. The future is truly bright with recent reported in-roads into Zambia (Dual energy x-ray technology). Like Olivio suggested soon sensor-based sorting will have a firm place in ore processing..

    O. Udoudo CSM, Uk

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  8. Thanks Mr. Udoudo. I hope you will be at Physical Separation '11 in Falmouth in June (www.min-eng.com/physicalseparation11). I see you are at CSM, so only a few miles away.

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