Council for Mineral Technology

Developments in Ore Sorting Technologies

5 June 2009

Carl BergmannSpecialist: Research

• Current status and description of electronic sorting• Modern sensor types• Latest developments and improvements• X- ray transmission : Commodas Ultrasort• X-ray fluorescence : Rados

Contents

• Both conductivity and photometric sorters 1970’s• Remnants of old radiometric sorters at some

Witwatersrand gold mines• Optical sorters with line scan cameras – since

1990’s

• Estimated ±300* sorters in ore and minerals sorting worldwide (excluding diamond fluorescence sorters)

* Source: Commodas/Ultrasort and Rados

Some history

Base Metals PreciousMetals

IndustrialMinerals Fuel

IronManganeseCopperZincNickelTungstenSlag

CalciteFeldspar Dolomite TalcQuartz Magnesite Salt

Diamonds Tanzanite Emeralds

Diamonds& Gems

UraniumCoal

GoldPlatinum

Sensor based sorting applications

5

1 Material feed

2 Vibratory feeder

3 Free fall acceleration

4 Sensor - Line scan camera(s)

5 Data processing

6 Air pressure valves

7 Accept stream

Reject stream

8 Network interface for central control

Sensor based sorting principles

Range of sensors

»

Available Sensors within the Electro Magnetic Spectrum

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

101

102

103

104

Ultraviolett (UV)

Visible light (VIS)

Near Infrared (NIR)

Microwaves

X-ray

Gamma-

radiation

Alternating current(AC)

Radio waves

[m]

Infrared (IR)

Sensor/Technology

Material Property Mineral Application

RM (Radiometric) Natural Gamma Radiation Uranium, Precious Metals

XRT (X-ray transmission)

Atomic Density Base/Precious MetalsCoal, Diamonds

XRF Visible Fluorescence under X-rays

Diamonds

COL (CCD Color Camera)

Reflection, Brightness,Transparency

Base/Precious MetalsInd. Minerals, Diamonds

PM (Photometric) Monochromatic Reflection/Absorption

Ind. Minerals, Diamonds

NIR (Near InfraredSpectrometry)*

Reflection, Absorption Base metalsIndustrial Minerals

IR (Infrared cam)* Heat conductivity, heat dissipation

Base MetalsIndustrial Minerals

MW-IR (heating in conjunction with IR)*

Sulfides & Metals heat faster than other minerals

Base/Precious Metals

EM (Electro-Magnetic sensor)

Conductivity Base Metals

* Under development

Rock type ROM distribution Crusher A Crusher B

Chromitite 42.89 38.39 37.58Pyroxenite 1.08 0.89 0.99Pegmatoid 5.37 5.08 4.55Anorthosite 1.9 1.76 1.78Light Contacts 6.97 5.14 0.76Dark Contacts 4.4 2.79 0.96<20mm fines 37.39 45.95 53.38

Interparticlecrushing may give better liberation leading to a lower percentage of composite stones

Lessons learnt - General

Feed Preparation!

• Defined size class ranges

• Clean surfaces

• Monolayer of particles

• Predictable trajectory

Lessons learnt – Optical SortingWide range of ambient temperatures in South Africa:

• affects the illuminating light colour

• which changes the way the particles are seen

so:

Fluorescent lights Water cooled fluorescent LED lights

Also:

• Clean, dry, oil-free, rust free air compressed air for the valves

• Needs relevant skills level to operate and maintain

• Developing technology– Faster computer speed– More robust construction

(Commodas/Ultrasort merger)

Some improvements – General

Run of Mine (ROM) Series

Industrial Processing (PRO) Series

Gem Stone (GEM) Series

Old

len

ses

New

len

ses

(20

09

)Image improvement – new lenses

11

Old

len

ses

New

len

ses

(20

09

)

Blue Shadow

Better texture recognition

Image improvement – new lenses

Slow motion video – Optical Sorting

Latest Pro Series Sorter at Mintek

13

• Throughput 16 – 40 tph• Size Range -40mm +10mm• Compressed air 55 kW ;pressure 8 bar

XRT Sorter at Mintek

14

Medium-Grade Sulfide ore

Low-Grade Sulfide Ore

Massive -Sulfide ore

XRT Images

• Developed in Russia• Direct XRF assay of particle surfaces• Mechanical ejectors – no compressed air• Extremely robust• Modular units

Rados Introduction

RADOS clip

Rados Sorter – Internal view

Ore Feed Chutes

XRF Sensors

Mechanical Actuators

Rados XRF SortingRADOS Model Particle Size Range Throughput

(tph)

SRF4-050M –60mm +10mm 3 – 5

SRF4-150M -150mm +30mm 10 – 20

SRF3-300M -300mm +150mm 25 – 35

• 49 plants in Russia and neighbouring countries • 2-5 elements measured simultaneously per particle• Sorting rules are easily set, product and waste grades are measured• Due to be installed at Mintek later this year

Bank of 6 Rados Sorters

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Conclusions

• Sensor Based Sorting is still a developing technology that is rapidly evolving. Improvements are continually being made in terms of sorter robustness and measurement sensitivity.

• A very wide range of sensors are now available and in development and is predominantly represented by Commodas Ultrasort

• X-Ray transmission sorting has particular promise in the field of dry coal sorting. For other silicate minerals, the current top size that the X-rays can pass through is around 40mm

• The Rados X-Ray fluorescence sorting technology, developed and operated in Russia, will soon be available for local testing.

www.mintek.co.za

Thank you