Novel Method To Study the Particle Circulation in a Flat-Bottom Spout-Fluid Bed

A novel method of particle tracking combining microwave heating and infrared thermal imaging technology has been developed. The method is applied to study the particle circulation in a flat-bottom spout-fluid bed operated under ambient conditions. The spout-fluid vessel constructed with microwave-transparent Plexiglas is placed in a well-designed microwave heater. Inside the bed, a single polar tracer, sharing the same size but different densities with bed particles, is heated continuously by the microwave energy. Then its trajectory is detected by means of a top-grade infrared camera. Thus, two hydrodynamics parameters such as the cycle time distribution and residence time distribution are determined by processing the obtained thermal images. On the basis of this, the effects of tracer density and gas velocity on them are analyzed, respectively. The results show that there exist two kinds of cycles: short cycle and nonstandard cycle. The former is predominant in the case of heavy tracer, and the latter is more significant at lower gas velocities. Raising the spouting gas velocity lowers the mean cycle time and promotes high concentration of the residence time distribution in the vicinity of the wall. An increase in the fluidizing gas velocity leads to a lower mean cycle time and a more homogeneous residence time distribution in the annulus.