Experimental tracking of particle-size distribution in a fluidized bed

Abstract Particle-size distribution is a fundamental parameter in fluidization. It affects fluidization behavior, transport and kinetic properties in the bed, and process considerations for operation. Many factors affect particle-size distribution, including solids feed, solids discharge, elutriation, particle growth and particle shrinkage. We have developed a method to track this important parameter via an on-line process computer. The on-line particle-size distribution measurements, made automatically and with little time-delay after sampling, are obtained every 60 s in the experimental demonstrations. Such a frequency is high enough to properly track particle-size distribution even during extreme distribution dynamics. Particle sampling is continuous in our method, and the sample system is closed-loop so that all sampled particles are returned to the fluidized bed. The experimental demonstrations were performed on a large-particle, sand-air fluidized bed. In this paper we detail the experimental equipment and procedures used. The experimental results presented include the tracking of particle-size distribution during two different particle-size distribution transients. Validity of the on-line measurements were verified via sieve analysis of grab samples. The on-line measurements are shown to be representative of actual conditions in the bed. They are somewhat noisy (corrupted with random error), however, with the measurement noise increasing as a function of particle size.