Mixing of Particles in Gas−Liquid−Solid Fluidized Beds Containing a Binary Mixture of Particles

Abstract

The present study focuses on the axial-mixing characteristics and flow behavior of fluidized particles, which so far have received scant attention compared to the bubbling and flow behavior of fluidizing fluids. On the basis of the axial dispersion model, the mixing coefficients in a gas−liquid−solid fluidized bed with an i.d. of 0.152 m have been estimated from the composition of a binary-particle mixture in the mixing region of the bed. The complex mixing behavior has been interpreted by means of the fractal analysis of pressure fluctuations generated in the bed. It has been found that the axial-mixing coefficient increases with an increase in the gas flow rate or the particle size and that it exhibits a local maximum with respect to the variation of the liquid flow rate. The Hurst exponent recovered from the Pox diagram of pressure fluctuations decreases with increasing gas flow rate, but it displays a local maximum with variation of the liquid flow rate in the bed containing a binary mixture of particles. The axial-mixing coefficient has been correlated in terms of the operating variables. Moreover, a correlation has been obtained, which includes the Peclect number containing the mixing coefficient and the dimensionless groups derived from the isotropic turbulence theory.

Effects of Chaotic Temperature Fluctuations on the Heat Transfer Coefficient in Liquid-Liquid-Solid Fluidized Beds

“…In other words, the flow regime of solid particles changes from circulation to turbulent random motion at this intermediate U c or bed porosity condition. It has already been reported that the particle flow behavior is most regular and periodic at intermediate U c or bed porosity in liquid-solid and gas-liquid-solid fluidized beds [3,7,16,17].…”

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

“…of 0.152 m were interpreted by means of the fractal analysis of pressure fluctuations generated in the bed. The Hurst exponent recovered from the Pox diagram of pressure fluctuations decreases with increasing gas flow rate, but it displays a local maximum with variation of the liquid flow rate in the bed containing a binary mixture of particles . Hydrodynamic studies were conducted in gas–liquid–solid systems of 3.0 mm glass beads and of 2.1 mm polypropylene low-density particles.…”

“…The Hurst exponent recovered from the Pox diagram of pressure fluctuations decreases with increasing gas flow rate, but it displays a local maximum with variation of the liquid flow rate in the bed containing a binary mixture of particles. 29 Hydrodynamic studies were conducted in gas−liquid−solid systems of 3.0 mm glass beads and of 2.1 mm polypropylene low-density particles. Simultaneous measurement of differential pressure and bubble conductivity probe signals enabled the investigation of the change in flow structure in relation to the flow regime transitions.…”