An enhanced monitoring method, based on pressure fluctuation measurements,
for observing nonstationarities in fluidized-bed hydrodynamics is presented
. Experiments show that it can detect small changes in the particle-size di
stribution. Such a monitoring method is useful to give an early warning of
the onset of agglomeration in a fluidized bed. In contrast to earlier metho
ds, this method is insensitive to small changes in superficial gas velocity
and can handle multiple signals, making it relevant to industrial applicat
ion. By carefully choosing the measurement position, the method becomes als
o insensitive to small bed mass variations. rt uses the attractor reconstru
cted from a measured pressure signal, which is a "fingerprint" of the hydro
dynamics of the fluidized bed for a certain set of conditions. Using this m
ethod statistically the reconstructed attractor of a reference time series
of pressure fluctuations (representing the desired fluidization behavior) i
s compared with that of successive time series measured during the bed oper
ation.