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Elemental Analyzers (4 replies)

Marshal Meru
9 months ago
Marshal Meru 9 months ago

Would it be beneficial to be able to analyze the elemental grades of material in real time on the conveyor belt of an operational process?

9 months ago
Oberfuhrer 9 months ago

The answer is yes! I understand there are some devices that currently work for ash in coal but I've not encountered anything that works at the required precision for commercial transitions in things like iron ore, bauxite, gold etc. I would be interested if you have some examples.

Sugar Watkins
9 months ago
Sugar Watkins 9 months ago

There is a huge potential for on-line analysis applications. Gamma is one of them. It is important to keep in mind that most technologies are more sensitive than accurate. They will identify immediately variations of a continuous flow composition, but may provide unpredictable results on a heterogeneous flow. They will not replace lab analyses for accurate absolute results, but may provide sensible results once properly calibrated on your specific matrix. Calibration for specific flows may be easier done by an expert at the beginning.

Maya Rothman
9 months ago
Maya Rothman 9 months ago

On belt analysis is worthy is you use the information for process control and you need to produce a statistically significant figure in time periods synchronized with the process latency and control loops response. Typically you use aggregates of 10, 20, 50 0r hundreds measurements to compensate variability of in process materials , of course it will help and be preferred to sample the material on belt and assemble a measurement station where you can configure the best geometric and dynamic configuration to optimize measurement.

Marshal Meru
9 months ago
Marshal Meru 9 months ago

We do have analysers in coal applications that are used for contracted payments (tariff terms). The issue when comparing analyser performance to lab performance in any commodity is that the sample mass being analysed in the case of the lab sample is usually a very small sub sample which represents in most cases less than 0.0005% of the raw material mass. Usually as a periodic grab sample; sampled once every 5 to 30 minutes. Whereas when an on belt analyser is being used, you are analysing over 90% of the bulk material stream by transmission through the ore bed in real time, giving continuous analysis.

Sometimes repeatability is confused with representivity when comparing lab results to analyser results. Our experience is that the errors associated with sample representivity with respect to the dynamic material stream are not included in conventional laboratory errors, which tend to relate to repeatability (if you re-test, do you get the same result?), rather than representivity (is that teaspoon of material the same composition as the balance of material from the sample period?); in fact in many cases the lab sample is assumed to be 100% representative, when in reality it cannot possibly be, as the other 99.0095% of the material was not sampled at all.

This means that (across commodities) a well calibrated on belt analyser will be both more representative and more accurate than the "representative" grab sample that is processed through the laboratory.

The most common uses for these technologies are met accounting, waste rejection, feed material blending, real time process control, product grade optimisation, quality monitoring and real time monitoring applications that would show grade / quality issues that are not represented in physical periodic grab sampling processes.

Thanks for your comments, you may be pleased to know that in relation to the gamma spectrum, we do not see the matrix interference effects that are common in XRF applications when dealing with elemental ratio shifts, and so calibration of the Geoscan is much simpler in this regard.

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