Pressure fluctuations as a diagnostic tool for fluidized beds. Technical progress report, July 1, 1996--September 30, 1996 [report]

R.C. Brown, E. Brue
1996 unpublished
By studying pressure fluctuations using a system idenmcation approach, it is hypothesized that CFB pressure fluctuations are indicative of CFB hydrodynamics,m two ways. First, the frequency phenomenon that is observed m the lower regions of the CFB under conditions of high solids loading is the result of lower dense bed voidage oscillations. Our results suggest that a Surface wave phenomena inversely proportional to the square root of the bed diameter is also be observed in CFB pressure
more » ... ions under most conditions. By matching revised similitude parameters between two CFBs a number of conclusions can be drawn. First, spectral analysis of pressure ftuctuations, ifproperly applied, can be used to verify that similitude has been achieved. To do this, not only must the Bode plot characteristics important for hydrodynamics be identified, but the pressure fluctuation structure at all elevations of the CFB must be similar. The set of similitude parameters dehed by Glicksman is not suf€icient to establish hydrodynamic similitude. The solids fhm as typically measured in the downcomer does not contain inforplation on the solids hold-up m the risir, or the amount of solids that progress downwards in the annulus rather than exit the riser. It is better to use the total mass contained in the riser as the important "solids" parameter for the establishment of similitude, rather than the solids flux. This measurement can be made more accurately, monitored continuously, and is a much simpler measurement to perform in most CFB systems. Even with this new set of dimensionless parameters, the differences in the coefficient of restitution of particlehed collisions may make a Signiscant difference in the CFB hydrodynamics. The effects of particle collisions with the riser top-plate must be considered in similitude studies.
doi:10.2172/418270 fatcat:pyscm6o5qbeqjaa4pplyv6i4wu