(602b) An Acoustic Method for the Measurement of Minimum Fluidization and Bubbling Properties of Group A Solids

Minimum
fluidization and bubbling densities and velocities are widely used in fluidized
bed design and modeling. The methods presently used for measuring these
parameters are, however, time consuming and labor intensive. Traditional
methods have often relied on visual observations to determine the minimum
bubbling point, which is likely to introduce some subjectivity in the data and,
also necessitates the use transparent columns. Such test units often will not
withstand high temperature and pressure conditions. This presentation discusses results obtained in a
new 6-in (0.15-m)-diameter test unit in which the minimum fluidization and
bubbling points were detected by the use of acoustic waves. The test materials were
FCC catalyst particles of various fines contents (% < 44 mm). Tests were conducted at low-to-moderate system pressures. Gas flowrate
was automatically adjusted at a chosen time interval using a mass flow
controller. Results showed that fines content had no significant effect on the
minimum fluidization velocity. The minimum bubbling velocity, however, increased rather sharply when the fines content
exceeded about 5% less than 44  microns. Both the minimum fluidization density and minimum bubbling density of
FCC catalyst particles were found to decrease slowly with increasing fines
content. For the pressure range used in these tests, there was no significant effect of pressure on both the minimum
fluidization velocity and the minimum bubbling velocity. Furthermore, pressure had
very small influences on both the minimum fluidization and minimum bubbling
densities.