Nonlinear analysis of gas-solid flow behavior in fast fluidized bed riser

A fast fluidized bed riser with 16 m height and 0.10 m ID was operated with FCC particles and in a wide range of operating conditions. The superficial gas velocity U_g ranged from 3.5 m·s^-1 to 8.1 m·s^-1, and the solids circulating rate G_s was from 50kg·m^-2·^-1 to 201 kg·m^-2·s^-1. Time series signals of solids holdup fluctuation were measured at a frequency of 900 Hz using an optical fiber located at 8 axial and 11 radial positions. The nonlinear method was used to analyze the time series and consequently Kolmogorov entropy was calculated to describe the dynamic characteristics of the gas-solid flow behavior in the annular-core section. The results showed that Kolmogorov entropy could describe the annular-core flow structure. According to three marked characteristics of Kolmogorov entropy in the radial direction, three flow regions were identified: random-particles-controlled core region, chaotic-particles-controlled transitional region, wall-controlled annulus region. The change of Kolmogorov entropy in the radial direction was also interpreted based on the influence of solids on gas turbulence structures.