Vibration time series analysis of bubbling and turbulent fluidization--颗粒学报PARTICUOLOGY

Azizpour, H., Sotudeh-Gharebagh, R., Zarghami, R., & Mostoufi, N. (2012). Vibration time series analysis of bubbling and turbulent fluidization. Particuology, 10(3), 292–297. https://doi.org/10.1016/j.partic.2011.11.006

Vibration time series analysis of bubbling and turbulent fluidization

Hedayat Azizpour, Rahmat Sotudeh-Gharebagh, Reza Zarghami^*, Navid Mostoufi

Multiphase Systems Department, Oil and Gas Processing Centre of Excellence, School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box 11155/4563, Tehran, Iran

10.1016/j.partic.2011.11.006

Volume 10, Issue 3, June 2012, Pages 292-297

Received 17 July 2011, Revised 23 September 2011, Accepted 2 November 2011, Available online 25 February 2012.

E-mail: rzarghami@ut.ac.ir

Highlights

► Hydrodynamics of a gas–solid fluidized bed was studied via analyzing vibration signals measured by an accelerometer.

► The maximum value of Hurst exponent of macro structure occurred at the onset of regime transition from bubbling to turbulent.

► The results showed the methods are capable of detecting the regime transition from bubbling to turbulent fluidization using vibration signals.

Abstract

A non-intrusive vibration monitoring technique was used to study the hydrodynamics of a gas–solid fluidized bed. Experiments were carried out in a 15 cm diameter fluidized bed using 226, 470 and 700 μm sand particles at various gas velocities, covering both bubbling and turbulent regimes. Auto correlation function, mutual information function, Hurst exponent analysis and power spectral density function were used to analyze the fluidized bed hydrodynamics near the transition point from bubbling to turbulent fluidization regimes. The first pass of the autocorrelation function from one half and the time delay at which it becomes zero, and also the first minimum of the mutual information, occur at a higher time delay in comparison to stochastic systems, and the values of time delays were maximum at the bubbling to turbulent transition gas velocity. The maximum value of Hurst exponent of macro structure occurred at the onset of regime transition from bubbling to turbulent. Further increase in gas velocity after that regime transition velocity causes a decrease in the Hurst exponent of macro structure because of breakage of large bubbles to small ones. The results showed these methods are capable of detecting the regime transition from bubbling to turbulent fluidization conditions using vibration signals.

Graphical abstract

Keywords

Fluidization; Auto correlation function; Mutual information function; Hurst exponent; Vibration signal

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