Development of a Novel Optical Radiation Depolarization Technique for On-Line Measurements of Particle and Bubble Sizes

Grinding and froth flotation are the two most important processes for mineral beneficiation. The importance of grinding is well reflected in the fact that approximately 80% of beneficiation costs are for grinding, mainly due to high energy consumption. To reduce energy consumed by grinding, fines should be removed quickly from the grinding circuit. This requires a reliable online particle size analysis technique. Froth flotation is the most widely used solid-solid separation process for coal and minerals beneficiation and about 90% of mineral concentrates are produced from froth flotation. It is now recognized that air bubble size distribution plays an important role in flotation separation performance. Optimization of bubble size distribution is possible only if bubble size can be monitored on-line. Obviously, an on-line analysis technique for particle and bubble size is critical for enhanced grinding and flotation process efficiency. The proposed project is aimed at developing an optical radiation depolarization technique for on-line size analysis for grinding and flotation processes to minimize energy consumption during grinding and maximize separation efficiency of flotation. The technique is based on angular and radial profiles of reflection and transmittance of an object subjected to a collimated, polarized light beam. A hybrid Monte Carlo/Ray- Tracing method will be used to simulate the depolarization of radiation by particles or air bubbles. The size distribution will be determined by best fitting experimentally determined vertical and horizontal polarization components of both radial and angular profiles of reflection and transmission. In addition to size analysis, the proposed technique can also determine the water film thickness and the bubble separation distance distribution in foams.