Fractal Structure in Gas–Liquid–Solid Circulating Fluidized Beds with Low Solid Holdups of Macroporous Resin Particles

Abstract

The fractal structures of flow images of gas–liquid–solid circulating fluidized beds (GLSCFBs) with low solid holdups of macroporous resin particles at different operating conditions and liquid physical properties were investigated by the fractal analysis method. The images were obtained with the high-speed image acquisition and treatment system of complementary metal oxide semiconductor (CMOS). The results show that the structure of the gas–liquid–solid circulating flow exhibits certain fractal behavior and the fractal dimension D can be used to describe the multiphase self-organization flow structure from the point of view of geometry. The fractal dimension changes with the phase holdup and the agglomeration degree of bubbles or/and particles. Generally, higher solid or gas holdup leads to larger fractal dimension and more extensive aggregation or self-organization degree results in lower entropy and thus lower fractal dimension. In order to avoid the appearance of the aggregation in the GLSCFB riser, higher superficial velocity of primary liquid flow, lower superficial velocity of auxiliary liquid flow, and lower liquid surface tension may be exerted.