Pressure fluctuations as a diagnostic tool for fluidized beds. Technical progress report, July 1, 1995--September 30, 1995

Abstract

Comprehensive experimentation has been conducted to determine whether circulating fluidized bed (CFB) pressure fluctuations can be used to verify that similitude conditions in circulating fluidized beds have been achieved. Using two geometrically similar CFB models, pressure fluctuations were recorded while the full set of similitude parameters were matched under a broad range of operating conditions. The method of data acquisition and analysis is shown to be very important in order to observe the significant frequency phenomena. Under relatively dilute conditions similar power spectral density and Bode plot profiles are observed in the two geometrically similar beds. The dominant frequency under these dilute conditions is inversely proportional to the characteristic CFB dimension. Under conditions of higher solids loading, an additional lower bed frequency phenomena is observed in the spectrum which may be a function of the depth of the lower dense bed in the CFB. It is evident from the results that under some operating conditions, a single dimensionless frequency is not sufficient to validate the achievement of similitude using pressure fluctuations. The results also suggest that the use of similitude parameters as they are currently defined is limited to dilute operating conditions, prior to the formation of a lower dense CFB.