Multiscale characterization of nanoparticles in a magnetically assisted fluidized bed--颗粒学报PARTICUOLOGY

Karimi, F., Haghshenasfard, M., Sotudeh-Gharebagh, R., Zarghami, R., & Mostoufi, N. (2020). Multiscale characterization of nanoparticles in a magnetically assisted fluidized bed. Particuology, 51, 64-71. https://doi.org/10.1016/j.partic.2019.09.003

Multiscale characterization of nanoparticles in a magnetically assisted fluidized bed

F. Karimi ^a, M. Haghshenasfard ^a *, R. Sotudeh-Gharebagh ^b *, R. Zarghami ^b, N. Mostoufi ^b

a Department of Chemical Engineering, Isfahan University of Technology, P.O. Box 8415683111, Isfahan, Iran
b School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box 11155/4563, Tehran, Iran

10.1016/j.partic.2019.09.003

Volume 51, August 2020, Pages 64-71

Received 10 September 2018, Revised 23 May 2019, Accepted 17 September 2019, Available online 3 December 2019, Version of Record 11 April 2020.

E-mail: haghshenas@cc.iut.ac.ir; sotudeh@ut.ac.ir

Highlights

• Fluidization quality can be improved by applying a magnetic field.

• Decreasing DET by applying a magnetic field results in diminution of agglomerate size.

• Applying an external field increase the share of meso-structures in the bed.

Abstract

Pressure fluctuations of a fluidized bed of nanoparticles were measured during the fluidization of nanoparticles with and without a magnetic field at a frequency of 50 Hz. Recurrence quantification analysis (RQA) and wavelet transform were used to determine the frequency range of various flow structures in the bed at three scales. The frequency ranges of the macro-, meso-, and micro-structures were determined to be 0–49 Hz, 49–781 Hz, and 781+ Hz, respectively. Comparison of the determinisms of the sub-signals with and without the external field revealed that in the presence the field, breakage of larger agglomerates occurs faster than re-agglomeration of small agglomerates into larger ones. The power spectral density function of the pressure fluctuations indicated that with an external magnetic field, the power and the frequency range of the pressure signal of macro-structures do not change noticeably. However, the power of the meso-structure signal increases and its frequency range is widened toward higher frequencies, confirming that the number of small bubbles and agglomerates increase in the bed. In addition, the energy of signal analysis indicated that the external field significantly increases the share of meso-structures in the bed, confirming the RQA results.

Graphical abstract

Keywords

Nanoparticles; Fluidized bed; Magnetic field; Pressure fluctuations; Recurrence quantification analysis; Wavelet transform

文章导读