The characterization of flotation by colour information and selecting the proper equipment

Summary form only given. Flotation is the most common industrial method by which valuable minerals are separated from waste rock, after crushing and grinding the ore. For process control, flotation plants and devices are equipped with conventional and specialized sensors. However certain variables are left to the visual observation of the operator, such as the colour of the froth and the size of the bubbles in the froth. The ChaCo-project (European Union-project 24931) started in November 1997. A measuring station was built at Pyhasalmi flotation plant. The system includes RGB-camera and spectral colour measurement instrument for flotation colour inspection. Visible spectral range measurements were also made for comparing the comments of operators for colour of the froth related to sphalerite concentration and process balance. Different dried mineral (sphalerite) ratios were also studied with iron pyrite to find out the minerals typical spectral features. Sphalerite spectral reflectance over different wavelengths, correlated to the sphalerate concentrations, is used for selecting a proper camera system with filters or for comparing the results with colour information from RGB-camera. Different candidate machine vision techniques are discussed for this application and the pre-processed information of dried mineral colours is used and adapted to the on-line measuring station. Moving bubbles of the froth produce total reflections disturbing the colour information. Polarization filters are used and results are reported. Reflectance outside visible light is also studied and reported.