Plant control is most effective when technologies measure process streams directly and preferably in real time. Measuring sampling streams that are not representative of the primary flow will result in incorrect plant control decisions.

Sampling coarse conveyed flows is expensive and impractical at many operations, however, this does not mean those flows cannot be measured.

Real time analysis technologies for conveyed bulk materials have been used in the coal and cement industry since the early 1980s. For the last 15 years, Scantech, an Australian company specialising in on-conveyor analysers, has supplied such analysis systems to the minerals industry, including copper, manganese, zinc-lead, bauxite and iron ores.

For example, phosphate plants in northern Africa use on-line elemental analysers for phosphate rock quality control, iron ore mines in South Africa use analysers to measure and manage ore and product quality, copper mines in central Africa use moisture monitors for process control, cement plants in western Africa use analysers for stockpile control, while coal mines and power stations in southern Africa use analysers to improve plant efficiencies.

Sampling methods have been developed and refined to enable collection of a “more representative” sample. Nevertheless, sample preparation and analysis methods by their nature are time consuming.

Real time, on-line analysis systems have been designed to also overcome the need to take routine samples for process control. The analysis of the whole stream continuously eliminates the major source of error – sampling error.

The application of the real time, non-contact (patented system), full stream continuous analysis methods to measure, and ultimately control quality variability in processing operations without physical sampling for process control and provides the added benefit of live data to fine tune operational performance by for example, reducing variability.

That is, although reducing variability of ore or product quality can be expensive and time consuming, operators know that consistency in quality is desirable in products used in further processing. In bulk mining operations (such as coal, iron ore, bauxite, limestone, phosphate) direct shipping quality material can by-pass a beneficiation process to reduce treatment costs. The ability to measure stockpile composition and blend to a specification during stacking has also proven beneficial.

Scantech International Pty Ltd real time analyser technologies are applied in a range of applications for the bulk materials industries. The COALSCAN ash and moisture monitors, CIFA (Carbon-In-Fly Ash) analyser and the COALSCAN 9500X elemental (PGNAA) analysers have been supplied to the world coal and power markets for over 30 years.

Note that these are transmission technologies, whereby all of the material is measured, compared to surface based technologies which are biased as only the top of the material is measured.

In more recent times, the GEOSCAN elemental analyser is used for cement and minerals applications especially iron ore. TBM 200 series and CM100 conductive moisture monitors are used in many industries for moisture management. Plants across Africa are using these moisture analysers in a variety of applications. For example, at the copper smelter, the analysers are used to measure the moisture content of the concentrate, and at the mine, the moisture content of the ROM is being measured for metal accounting. All units can be integrated with plant control systems for real time process control.

As an example of a typical application, copper-gold operation identified the need for plant feed analysis in real time to improve control of copper metal units entering its processing plant due to a limited leach circuit capacity for dissolved copper metal. The mining operations recovered ore from several open pits where ore grade varied between <1 percent Cu and >8 percent Cu. Mine planning information was used to determine the expected average copper grade for each blast which was then hauled to the designated run of mine (ROM) stockpile and then blended with ore from other stockpiles into a crusher and conveyed to a mill.  A GEOSCAN analyser was installed on the crushed ore conveyor with the main element of interest being Cu. The Cu content in the feed is controlled by adjusting the blend from the run of mine stockpiles approximately every 30 minutes as needed.

In a manganese application, GEOSCAN elemental analysers are used underground, for pre-sorting or the ore before it is conveyed to the surface. At the surface, the same analysers are used to ensure each delivery is produced to the end-users exact specification.

In some applications, the difference in Mn content from one customer to the next can be 2%, which means that it is important to have precise real-time product control over the ore quality.

Before the GEOSCAN was installed the is a Zinc-Lead Concentrator Heavy Medium Plant (HMP), the feed was monitored via two-hourly samples collected from the HMP feed hammer autosampler and assayed on site by laboratory XRF.

These samples had analysis turnaround times of up to eight hours. As a result of the high turnaround time, the resulting HMP feed grade
data could not be used for real-time HMP process control.

The data analysis comparing Geoscan and laboratory XRF grades has demonstrated that the technology has acceptable accuracy to be incorporated into HMP process control purposes.. Proactive control of HMP medium density setpoint will improve consistency in control of reject rate without heavy losses of lead and zinc metal to HMP rejects.

When real-time HMP metal recoveries are above the target range operations personnel will increase medium density setpoint to maximise HMP reject rate and minimise the content of non-value gangue in pre-concentrate conveyed to milling and flotation.

Monitoring real-time variation of HMP feed grades will enable operations personnel to make adjustments to the medium density setpoint to maintain consistent mill feed grades. Maintaining consistent mill feed grades allows stabilisation of mill operation, reducing mill power costs and mill grind size.

Finally, the monitoring of real-time variations in HMP feed grade will allow operations and metallurgy personnel to provide feedback to mining on the effectiveness of ore blending strategies and dilution control.

The Geoscan outputs have also been used to support HMP feed hammer sampler XRF results to report grades of individual orebodies and mine sources during campaigns of specific mine sources and ore types fed to HMP.

As can be appreciated, Scantech’s process control technology also has applications in a wide variety of ores and concentrates, such as copper, zinc, nickel, bauxite, and uranium, in addition to Scantech’s traditional applications in coal, coke and cement.

Contact Scantech on +61 7 3710 8406 for further information or e-mail sales@scantech.com.au  or visit www.scantech.com.au for local representative details.