Benefits of Online Particle Size Measurement in Mineral Processing

Automated online particle size measurement is being embraced more and more by the mineral processing industry because of the distinct advantages it offers over manual offline measurement and the cost efficiencies it is able to deliver.

Measuring particle size after milling, prior to further processing, is essential for reducing operating costs and extracting the maximum value from the ore being processed.

This measurement task has traditionally been carried out manually offline in a laboratory, occupying an operator’s full attention around the clock.

Not only is this costly from a manpower perspective, but because the testing is done periodically (only once every half hour or so), by the time a problem is detected or it is realised that a change is required (such as unblocking a separator, or adjusting material feed rate), valuable time and ore has been wasted.

By contrast, automated online particle size measurement provides a continuous stream of data, which allows for smaller changes to be made more often, thereby reducing wastage during reaction time, allowing problems to be rectified before they can escalate further and optimising operational flow. Where the ore being extracted is of particularly high value (such as gold), these cost efficiencies can be significant.

One of the earliest types of automated online particle measurement employed in the mineral processing industry involved the use of ultrasonics, but there were a number of clear limitations to this technology, and today, laser diffraction is the leading technology delivering the best results.

Laser diffraction particle size analysers are analytical instruments that determine particle size by the patterns produced when light interacts with them. Covering a particle size range from 0.1 to 2500 microns, they are ideal for the measurement of ore particles and can be used on both wet and dry flows.

The sample preparation rquired for laser diffraction analysis will vary depending on the process.  For wet minerals processing sample dilution is typically required and in some cases demagnetising or applying ultrasound to break up any agglomerates (clusters or accumulations of particles).

The samples are then analysed. Larger particles scatter the laser light narrowly at high intensity, while smaller particles produce a much weaker signal at wider angles.

Scientific instruments such as the laser diffraction particle size analyser are proving valuable tools, not just for the mineral processing industry, but across all kinds of manufacturing industries where automation of analysis is desired. Such instruments can deliver:

• A marked saving through reduced manpower costs
• Much greater control of particle size
• The ability to immediately detect and resolve potential problems
• Much faster optimisation of plant operation
• A lot less energy consumption
• A reduction in waste

By adopting these measurement techniques, those involved in the mineral processing industry are able to achieve a more favourable balance between the cost of liberation and the value of the mineral being processed. This translates into a higher return on their investment, with payback time from installation typically being six months to a year.