Detecting regime transitions in gas-solid fluidized beds from low frequency accelerometry signals

Abstract

a b s t r a c tLow frequency accelerometry signals have been applied for detecting regime transitions in a gas solid fluidized bed. Three solids have been fluidized to promote bubbling, churn and slugging regime. The Kolmogorov entropy and the power spectral density have been used to determine the regime transitions as well as to analyze the dynamical features characterizing the different regimes. Pressure and external acceleration measurements have been taken simultaneously. The accelerometry signal was sampled at 10 kHz; then, the envelope was extracted and resampled at 400 Hz. Pressure signal was sampled at 10 kHz and resampled at 400 Hz. Two problems were found during the work: the colored noise present in the envelope and the lack of low frequency information for one of the tested solids. FIR, wavelet and EMD filter strategies have been applied to remove the noise present in the envelope. It is concluded that the envelope of the accelerometry signal might be used to detect regime transition in the same way as the pressure fluctuation signals. Both Kolmogorov and spectral analysis exhibit common features to those obtained from pressure signal analysis, supporting the hypothesis of using low frequency accelerometry instead of conventional pressure measurements for monitoring fluidized beds.

Characterization of flow-induced vibrations in gas–solid fluidized beds: Elements of the theory

“…In addition, this approach disregards two important factors, such as the compression waves (van der Schaaf et al, 1998) and the structural vessel dynamics, which might affect the measurement of flow-induced vibration resulting from the fluidized bed dynamics, as discussed below. Consequently, the use of a theory based solely on "elastic waves" as the single source of "Acoustic Emissions ( AE)" cannot be easily extended to other FB systems and does not explain the most recent research results in the field (Abbasi et al, 2009;Cody et al, 1996;Cody et al, 2000;de Martin et al, 2010;de Martin et al, 2011;Li et al, 2011).…”

Characterization on hydrodynamic behavior in liquid‐containing gas‐solid fluidized bed reactor

“…Compared to other techniques, pressure measurement develops rapidly and can clearly reflect gas bubble behavior in fluidized beds, which has been regarded as a popular and mature measurement technique . Besides, as a promising technique, AE measurement has received extensive attention in recent years and enjoys a bright future in particle characterization as well as bubble behavior . The study of He shows that pressure measurement is suitable for reflecting gas bubble behavior while AE technique is more suitable for characterization of particles and agglomerates motion.…”

Non-intrusive characterisation of particle cluster behaviours in a riser through electrostatic and vibration sensing

“…In addition, accelerometers are desirable non-intrusive tools that enable the measurement of flow-induced vibrations experienced by fluidised beds and hence the characterisation of flow structure behaviours [4]. Accelerometers have been used for monitoring the bed fluidity [20], detecting the agglomerate occurrence [20], and characterising the particle motion [21] and the bulk and bubble dynamics [22][23][24][25]. As bubbles and particle clusters are both classified as mesoscale flow structures [22,26], accelerometers should also be applicable to cluster behaviour characterisation.…”