Visual Investigations On Self-Organization Structure In Gas-Liquid-Solid Circulating Fluidized Beds

Self-organization, a macro space-time orderly structure formed spontaneously, is a type of general phenomenon in the nature and society, such as convective pattern of Bénard fluid, chemical oscillation and chemical waves of Belousov-Zhabotinsky, self-excited oscillation of laser. Self-organization phenomena are also usually found in fluidization system, for example, movement of fluidized solid particle groups, spiral type ascending motion of bubbles and wakes. As for the self-organization structure of Gas-Liquid-Solid Circulating Fuidized Bed(GLSCFB)system, the investigation on the particle clustering behavior and multiplex clustering behavior of bubbles and particles can deepen the fundamental understanding of the system, improve the performance of mass transfer and heat transfer, and provide theoretical basis for the development of high efficient fluidized bed reactor. Therefore, the investigations on self-organization behavior have theoretical significance and industry application value. But the investigation of self-organization phenomenon on GLSCFB was shortage in the open literature.A gas-liquid-solid circulating fluidized bed was designed and built up to systematically study the self-organization behavior of clustering particles in the riser and the downcomer of GLSCFB with the Complementary Metal Oxide Semiconductor (CMOS) image collecting and measuring system. Considering several physical quantities such as the ratio of the clustering particle number to the total particle count and the ratio of multiplex clustering bubble number to the total bubble number, the effects of operating conditions, liquid and particle properties on the clustering behavior of GLSCFB were investigated. Some results and conclusions were obtained, including that the particle clusters mainly existed as doublets and triplets, the multiplex clusters mostly existed as one bubble carrying two to four particles. The change of the average life time of particle clusters is not obvious which maintained at around 0.07 s. Whereas the average life time of multiplex cluster altered between 0.02 and 0.07 s is influenced strongly by the surrounding environment. The self-organization behavior in GLSCFB is closely associated with operating conditions, physical properties and hydrodynamics. The increases of main flow, particles diameter and particle density result in the decrease of the agglomeration. But the increases of auxiliary flow and liquid viscosity can enhance the agglomeration. The relationship between the fractal dimension and clustering behavior was also discussed. Fractal dimension can describe the self-organization behavior geometrically in GLSCFB and the enhancement of clustering behavior lead to the decrease of fractal dimension. According to fractal dimension, phase holdup and clustering behavior, knowing the changing trend of any couple factors, the other can be predicted.