Process Control is improved using real-time analysis


Plant control is most effective when online technologies measure process streams directly and preferably in real time. Sampling coarse conveyed flows is expensive and impractical at many operations. Scantech, an Australian company specialising in on-conveyor analysers, has supplied such analysis systems to the coal and cement industry since the early 1980s. Real time analysis technologies for conveyed bulk materials have been used in the minerals industry for about 15 years. 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 monitor and control coal qualites.

Real time, non-contact, full stream, continuous analysis provides measurements used to control quality variability in processing operations without physical sampling and provide the added benefit of live data to fine tune operational performance. 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. Further, 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.

Scantech International real time analysers incorporate full conveyed depth transmission technologies which provide representative results, as compared to surface based technologies which see only the top of the conveyed material.

The COALSCAN ash and moisture monitors have been supplied to the world coal and power markets for over 30 years. GEOSCAN elemental analysers are used for cement and minerals applications especially iron ore. TBM and CM100 conductive moisture monitors are used in many industries for moisture management. All units can be integrated with plant control systems for real time process control.

An early user of the elemental analyser technology in minerals was an iron ore mining and processing operation in South Africa. The company used an overland conveyor to transfer crushed ore to the process plant. The quality of the ore was variable and a need to effectively monitor its composition in real time was identified to allow a consistent product quality to be achieved. The GEOSCAN analyser was installed in 2003. The plant was then able to respond to expected changes in ore quality before the ore arrived, and improved its performance and product quality consistency. The experience of this installation and the improvements to the design led the company to purchase a number of analysers for its new larger plant. This plant was designed to treat a larger range of ore types and included a series of jig circuits to upgrade the various ore types. To maximise throughput of the beneficiation plant only ore requiring beneficiation was diverted to it.

As an example of a typical copper-gold application, the need for plant feed analysis in real time was needed 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 less than 1 % Cu and up to 8 % 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 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 in 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.

Monitoring real-time variation of HMP feed grades has enabled 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 allows 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.

Return on investment for nearly all Scantech’s analysers have been demonstrated to be in the order of a few months. Scantech provides high specification systems to maximise measurement accuracy and develops customised software for each application.



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