On-line non-intrusive particle size measurement of pulverised fuel through digital imaging

This paper presents the basic principles of particle size measurement and latest industrial results recorded using an innovative optical instrumentation system designed to measure the size distribution of particles in a pneumatic suspension. The system is non-intrusive and cost-effective. A low-cost CCD camera is used to capture images of the particulate flow field, which is illuminated by a low-cost pulsed laser sheet generator. The particle size distribution is then determined by processing the particle images through the use of novel processing algorithms. Experimental results obtained in the past on a small scale particle flow test rig have demonstrated that the system is capable of measuring the size distribution of pneumatically conveyed particles with an accuracy of a few percent. For the present paper results obtained when testing the system at a 4 MW industrial test facility are presented. Comparisons are made with both off-line reference data achieved through sieving and on-line laser diffraction data recorded using an intrusive, extractive, Malvern Instruments system. In general there is good agreement between results when considering the characteristics and limitations of the individual methodologies. The novel imaging system shows itself to be rugged, practical and useful under genuine industrial conditions.