论文信息 - Gas/solids flow patterns in a 30.5-cm-diameter circulating fluidized bed

Gas/solids flow patterns in a 30.5-cm-diameter circulating fluidized bed

ABSTRACT Tests were conducted in a 30.5-cm-diameter riser with 76 μm FCC catalyst to determine the degree of gas/solid contacting in the “fast-fluid bed” regime. Data were obtained at superficial gas velocities of 3.7 to 6.1 m/s and solid fluxes of 98 to 195 kg/s-m 2 . The conveying gas was air at ambient temperature and 103 kPa. Data were obtained on axial pressure profiles, particle velocity and mass flux as a function of radial and axial position, radial and axial gas dispersion, and solids residence time distributions. Density and voidage profiles were calculated from these data. Radial and axial gas dispersion coefficients were determined from steady-state helium tracer tests. The radial gas dispersion coefficient was found to be in the range of 25.8 to 64.5 cm 2 /s with an average value of 38.7 cm 2 /s. The axial gas dispersion was so small, 2 /s as to be negligible compared to convective gas flow. Solids residence time distributions obtained from pulse injections of NaCl tracer showed considerable backmixing of solids.

[1] Y. Yousfi,et al. Aerodynamique de l'ecoulement vertical de suspensions concentrees gaz-solides—I. Regimes d'ecoulement et stabilite aerodynamique , 1974 .

[2] K. Nakamura,et al. Vertical pneumatic conveying: An experimental study with particles in the intermediate and turbulent flow regimes , 1973 .

[3] Octave Levenspiel,et al. Fluid dispersion-generalization and comparison of mathematical models—I generalization of models , 1962 .

[4] J. J. van Deemter. Mixing Patterns in Large-Scale Fluidized Beds , 1980 .

[5] Mooson Kwauk,et al. The Dynamics of Fast Fluidization , 1980 .

[6] R. N. Bartholomew,et al. Measuring Solids Concentration in Fluidized Systems by Gamma-Ray Absorption , 1957 .

[7] D. Geldart,et al. THE HYDRODYNAMICS OF RE-CIRCULATING FLUIDIZED BEDS , 1986 .

[8] Joachim Werther,et al. ANALYSIS OF THE LOCAL STRUCTURE OF THE TWO PHASE FLOW IN A FAST FLUIDIZED BED , 1986 .

[9] H. A. Lauwerier,et al. Diffusion in a Fluid Moving at Uniform Velocity in a Tube , 1953 .

[10] H. Weinstein,et al. RADIAL VARIATION IN SOLID DENSITY IN HIGH VELOCITY FLUIDIZATION , 1986 .

[11] J. F. Large,et al. OVERALL AND LOCAL CHARACTERISATION OF FLOW REGIMES IN A CIRCULATING FLUIDIZED BED , 1986 .