ÄKSY

Intelligent methods in mining environment

Keywords: mining, mineral flotation, image analysis, data mining, soft sensors, process control, process monitoring

In this project, machine vision systems are studied and applied to mineral enrichment process. Machine vision provides new information that can be used for example in: characterization of flotation froth, crushed ore particle size distribution measurements and colour/spectral measurements. With this new information, it is possible to further study the process itself which is quite complex and difficult to model. However, with proper models and sophisticated controllers, the process can be controlled better and thus economical savings can be achieved.

The main objectives of the project are: better control over flotation circuits, improved colour measurements, improved particle size distribution measurement. Better control over flotation process can be achieved by introducing new measurements, improving measurement accuracy and by better controllers. One example is the laser-based froth distance measurements. They provide new information that is used to calculate froth thickness and to compensate the errorthat is introduced to other image-based measurements due to fluctuation of the distance between the froth surface and the camera. Another way to improve measurement accuracy is to combine the machine vision information coming from different flotation cells. This information is measured simultaneously and thus gives a more coherent picture of the whole process. Improved controllers will, among other things, utilize this new information.

Colour measurements seem to be very important in mineral flotation. The current way of measuring colour is by means of a RGB-colour camera. However, standard cameras are designed to measure colour in the same wavelength range as human eye. Introduction of new spectrophotometers enables a more thorough investigation of the froth and slurry colour with respect to colour depth and to wavelength range.

Particle size distribution is measured from a conveyor belt by using a properly placed light source and a monochrome-camera. The measurement point is located in the mine, some 1400 meters below ground level. The important thing in this research area is to be able to predict what the size distribution will be when the ore reaches the surface. This takes usually 2-3 days. Recent studies have indicated that the particle size distribution present in the mine is changed toward fines during transportation. This change will be modelled and taken into account in the prediction algorithms

Publications

• Jani Kaartinen and Antti Tolonen,
  "Particle size measurement of crushed ore using 3D-profile measurement,"
  Machine Vision News, Vol. 12, p. 14, 2007.
• Olli Haavisto, Jani Kaartinen and Heikki Hyötyniemi,
  "Optical spectrum based estimation of grades in mineral flotation,"
  in International Conference on Industrial Technology - ICIT 2006, Mumbai, India: IEEE, 2006, pp. 2529-2534.
• J Kaartinen, J Hätönen, H Hyötyniemi and J Miettunen,
  "Machine-vision-based control of zinc flotation - A case study,"
  Control Engineering Practice, Vol. 14, no. 12, pp. 1455-1466, 2006.
  Electronic publication
• Jani Kaartinen, Olli Haavisto and Heikki Hyötyniemi,
  "On-line colour measurement of flotation froth,"
  in Proceedings of the Ninth IASTED International Conference on INTELLIGENT SYSTEMS AND CONTROL, August 14–16, 2006, Honolulu, Hawaii, USA, V. L Syrmos and M. H Hamza (eds.), Hawaii, USA: ACTA Press, IASTED, 2006, pp. 164-169.
• Jani Kaartinen and Heikki Hyötyniemi,
  "Combining multi-camera-data of flotation circuit with PCA and PLS,"
  in Centenary of Flotation Symposium, Brisbane, Australia, 6–9 June 2005 - Proceedings, Graeme J Jameson (ed.), Brisbane, Australia: SME, AusIMM, 2005, pp. 121-125.
• Jani Kaartinen, Jari Hätönen, Martti Larinkari, Heikki Hyötyniemi and Jorma Miettunen,
  "Image analysis based control of copper flotation,"
  in Preprints of the 16th IFAC World Congress, P Horacek, M Simandl and P Zitek (eds.), Prague, Czech Republic: IFAC, 2005, 6 pp.
• Martti Larinkari, Jani Kaartinen and Heikki Hyötyniemi,
  "Management of particle size distribution of crushed ore,"
  in Proceedings of Process Systems 05, Cape Town, South Africa: MEi, 2005, 15 pp.