Characterization of gas fluidized beds of group C, A and B particles basedon pressure fluctuations

Pressure fluctuation data were obtained with a quick response transducer at a sampling frequency of 100 Hz for periods of 100 s (i.e. 10,000 points) i n order to characterize the gas-solid flow behaviour of fluidized beds of s ix powders. For beds of Geldart group B and group A particles, the occurren ce and movement of bubbles caused vigourous pressure fluctuations of relati vely large scale and weak dominant frequency. For beds of group C particles , on the other hand, pressure fluctuations were significantly smaller in sc ale and exhibited large dominant frequencies, with no clear formation of bu bbles. The standard deviation of pressure fluctuations was markedly higher for the group A particles than for the group C powders. Group C particles c ould be characterized by gas voids and channels which exhibit periodic beha vior, while beds of group A and B particles behaved in a less periodic mann er and were dominated by more random and intensive bubble motion. Chaotic t ime series analysis was carried out for the six different species of partic les. The Hurst exponent demonstrated differences between the three differen t powder groups. The two-phase character of gas-solids flow was more distin guishable for the group B and A powders than for the group C powders.