(36f) Spinning Wheel Powder Feeding Device - Fundamentals and Applications

Feeding a dispersed cloud of particles into a transport tube reactor, particularly on a laboratory scale, is difficult. A major difficulty is dispersing the particles with minimal gas flow so as not to reduce residence time in the reactor. The powder being fed to the reactor is a fine dust, which tends to form loose aggregates and to agglomerate in the feeding system. Aggregated particles increase heat transfer resistances which rapidly become the dominant mechanism limiting the reaction. In addition, aggregates can become sintered in the reaction process, forming undesirable hard agglomerates. Hence, the particle aggregates being fed need to be sheared to reduce particle size of feed powder entering the reactor.

A new particle feeder is proposed to disperse aggregates of particles into particle dust clouds. This feeder uses a vibrating tube to deliver the powder feed to a spinning wheel that mechanically shears the particles. The objective is to feed a powder at the smallest particle size possible rather than some aggregate size generated by and upstream screw or vibratory feeding device and to achieve such dispersion using minimized gas flow. Statistical results show that the spinning wheel alone is able to reduce the Particle Size Distribution (PSD) and when a minimal amount of gas is added to the system the PSD is reduced further. In addition, a fundamental model employing a discrete particle breakage equation combined with Monte Carlo has shown that the spinning wheel feeding system is able to consistently reduce particle size.