On-line particle sizing of pulverized and granular fuels using digital imaging techniques

Abstract

On-line particle sizing is desirable in many industries, particularly in the power generation industry. This paper presents the principle and design of a prototype, digital imaging based, instrumentation system that can measure size distribution of particles that are largely opaque. The system, which is intended as an industrial rather than a laboratory solution, operates on-line and is non-intrusive. The image processing sequence is discussed in some detail. Experimental results obtained using two common types of particulate material demonstrate the viability of the system. The use of static images has allowed the instrumentation system to be calibrated. The linearity and repeatability of the system are quantified in addition to direct comparisons between the measurements made and those from proven, off-line, industrial solutions. The effects of the illumination sub-system on the spatial sensitivity of the viewing field are discussed along with the turndown ratio. The discrepancies between reference and static measurements are also identified and discussed. The results indicate that the system has good linearity and excellent repeatability and that practical on-line measurement of particle size distribution can be achieved using this technique. As presented the system can be used with particles in the range 150µm–25 mm.