All too often it is possible for a metallurgist to get a good ‘feel’ for a system’s performance by simply looking at a particular stream or product, to the point where very reasonable estimates of grade can be obtained just by judging colour and lustre of a product. A good example of this is the use of ‘vanning’ shovels in the Cornish mining industry, which were successfully used for centuries to estimate copper or tin content.
However, when it comes to quantifying or monitoring these variables continuously, things quickly get very complex. A couple of all-too familiar examples include:
- Froth quality, i.e. colour of the froth as well as size and stability of the bubbles
- Banding of minerals of different specific gravities on shaking tables or in spiral separators
- Colour of magnetic or dense medium concentrates, for instance, darker products would indicate a higher coal content
At GSL we are firm believers in image analysis and are proud to offer a range of bespoke image analysis solutions (for example, determining void ratio for the rod charge in our Magotteaux Mill). To cope with the demanding computational processes involved in image analysis, we have installed a powerful workstation which runs on 2 Intel Xeon processors with 6 CPU’s per core, linked with a total of 48Gb of ECC (error-checking) RAM and a 3 terabyte hard-drive. This work station will help carry out a range of simulation work, including:
- Grinding media size and shape analysis, as well as characterisation of media breakage mechanisms
- Bootstrap modelling to determine sampling requirements more practical than those often produced by Gy’s formula
- Image analysis on process variables such as vortex height variations during stirred milling, or bubble size and froth colour during flotation tests
- Post-processing of liberation data to constrain goals such as grade, recovery, and mass yield for metallurgical testwork
- Fracture analysis in comminution products from technologies that induce micro-fracturing, such as HPGR, SelFrag and vertical shaft impactors.
In most of these cases, image analysis will not be the sole means of obtaining an answer, but it often supplements other analysis. Essentially, it is a single part of a larger puzzle where all too often a fair few pieces are missing. Over the next few weeks, each of these image analysis procedures will be the subject of a more detailed blog post. In the mean time, if you want to discuss what image analysis could do for your project, feel free to get in touch.
