Axial solid distribution in gas‐solid fluidized beds

Abstract

Γ‐ray attenuation method was applied to determine the axial fluidizing bulk density profile for an air‐solid aggregative fluidized bed. Except for beds fluidized at very high air velocities two distinct density zones were noted. The density of the bed in the lower portion of the column was relatively constant for a particular set of operating conditions and did not vary with bed height. The density in the top portion of the bed fell rapidly with bed height. The average density of the lower zone was correlated as a function of the operating variables. The density in the top zone was represented by a one‐tail normal distribution curve. A somewhat better correlation was obtained by a two‐parameter equation at high air velocities. The effects of operational variables, such as air velocity, static bed height, particle size, and particle‐size distribution on these correlations were investigated. Friction‐factor correlations based on two different definitions of bed height were also obtained.

Pressure fluctuations in a fluidized bed

“…amplitude's tendency to increase and then decrease with the distance above the distributor indicates that the bed density plays an important role in determining t h e amplitude of the pressure fluctuations in a fluidized bed. The position where the bed density begins to decrease descended the column with an increase in the air flow rate (Fan et al, 1962), and thus the position where the maximum amplitude occurred also descended the column, as can be observed in Table 3. Tables 2 and 3 also show that the diameter of the holes in the distributor had little effect on the major frequency; however, the use of the distributor with a smaller hole diameter resulted in smaller fluctuating amplitudes in both the plenum and the bed.…”

Application of γ-ray Attenuation for Measurement of Gas Holdups and Flow Regime Transitions in Bubble Columns

“…These reactors typically operate at high temperatures and pressures, and extrapolation of results obtained at ambient conditions is often not warranted. Attenuation (absorption) of γ-ray and/or X-ray radiation has been used to measure hydrodynamic parameters in a variety of two-phase systems, such as fluidized beds (Bartholomew and Casagrande, 1957;Baumgarten and Pigford, 1960;Fan et al, 1962;Orcutt and Carpenter, 1971;Gidaspow et al, 1983;Weimer et al, 1985), horizontal and vertical tubes and ducts (Pike et al, 1965;Jones and Zuber, 1975;Heywood and Richardson, 1979;Lipsett et al, 1986), and bubble columns (Gibson et al, 1957;Calderbank et al, 1961).…”

Moving‐bed solids flow in an inclined pipe leading into a fluidized bed: Part I. Gas leakage and pressure drop

“…If the assumption of a constant bulk solids density is not valid, the solids density distribution along the height of the fluidized bed must be employed in Equation (1). The axial solids density distribution in gas-solids fluidized beds was studied by Bakker and Heertjes (1960) and by Fan et al (1962). According to their works, the density profile may be divided into a lower-density zone and a falling-density zone.…”

“…According to their works, the density profile may be divided into a lower-density zone and a falling-density zone. Fan et al (1962) have established the following equation for the density profile in the falling-density zone:…”