VELOCITY-MEASUREMENT OF PNEUMATICALLY CONVEYED SOLIDS USING ELECTRODYNAMIC SENSORS

Theoretical and experimental studies of cross correlation techniques a pplied to non-restrictive velocity measurement of pneumatically convey ed solids using ring-shaped electrodynamic flow sensors are presented. In-depth studies of the electrodynamic sensing mechanism, and also of the spatial sensitivity and spatial filtering properties of the senso r are included, together with their relationships to measurement accur acy and the effects of solids' velocity profiles. The experimental eva luation of a 53 mm bore sensing head is described, including trials us ing a calibrated pneumatic conveyor circulating pulverized fuel and ce ment. Comparisons of test results with the mathematical models of the sensor are used to identify important aspects of the instrument design . Off-line test results obtained using gravity-fed solids flow show th at the system repeatability is within +/-0.5% over the velocity range of 2-4 m s(-1) for volumetric concentrations of solids no greater than 0.2%. Results obtained in the pilot-plant trials demonstrate that the system is capable of achieving repeatability better than +/-2% and li nearity within +/-2% over the velocity range 20-40 m s(-1) for volumet ric concentrations of solids in the range 0.01-0.44%.