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Process control systems

Real time analysis helps operations manage and control material variability,  On-line analysers can be effectively utilised to improve the consistency of feed and product quality through bulk sorting and blending control, many existing users of these technologies have gained competitive advantages through their ability to supply a more consistent quality product to the market.

Sampling and laboratory analysis have been traditionally used in the resources sector to estimate the quality of conveyed raw materials. Sampling methods have been developed and refined to enable collection of more representative samples. Sample preparation and analysis methods by their nature are time consuming. Advances in sampling and analysis have led to advances in process control. Every orebody and mining process is unique in some way – variability occurs between mines and also within them. This means real-time monitoring and control of variability is increasingly considered at most sites. Reducing variability of ore or product quality can be expensive and time consuming. Consistency in quality is desirable not only in the grade of any feed material entering a plant, but also in the plant products.

The main requirements to monitor conveyed materials include tonnage and moisture measurement, and an estimate of quality represented as elemental or mineralogical composition. Moisture content is a key measure as moisture rarely contains valuable components, can affect material handling and can com prise a significant component of the cost of transport and treatment. Grade and quality of material mined will impact on its treatment and final value. Real time process control is essential to optimise treatment where material quality is variable, and increasingly real-time elemental analysis of bulk conveyed materials is adding significant value to operations.

Real time analysis technologies for conveyed bulk materials have been used in the coal industry since the early 1980s. In recent years, on-conveyor analysers, have been introduced in the minerals industry. Moisture and elemental monitors are widely used in iron ore installations in South Africa and Australia. There have also been many successful installations of elemental analysers measuring the grade of copper, manganese and iron ores.

Over the past five years, segments of the minerals industry in Australia and other countries have supported the development of a real time analyser to improve process control in many mining, processing the bulk handling applications. Benefits derived from these technologies have provided significant improvements plant efficiencies in applications across commodities. The ability t o monitor feed quality and its variability has been utilised to optimise processing operations. Real time onconveyor analysers have also greatly improved process control in the cement industry which has previously relied heavily on sampling and delayed laboratory analysis results.

In bulk mining operations (such as coal, iron ore, bauxite, limestone, phosphate) direct shipping quality material can by-pass a treatment plant and reduce processing costs. The ability to measure stockpile composition and blend to a specification during stacking has also proven beneficial. The ability to measure the quality of a shipment (train, ship, etc.) during loading by analysing the whole flow continuously allows not only the average quality to be measured but also the variability on a minute by minute basis. It is clear that analysis of conveyed bulk streams is becoming more common as operations strive to process their materials in ways that improve stability, efficiency and productivity.

By Don Cook www.scantech.com.au

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