Wavelet Analysis of Electrical Capacitance Tomography Measurement Data from High Density Circulating Fluidized Bed

G. Lu, L. Peng, B. Zhang

Department of Automation, Tsinghua University, Beijing, China, Email: lugeng99@mails.tsinghua.edu.cn

ABSTRACT

Circulating fluidized beds (CFB) has been applied in chemical engineering for more than 70 years. In recent years, high-density circulating fluidized beds (HDCFB) have become popular for their high particle density, high reaction efficiency, as well as good heat transfer performance. However, the mechanism and characterization of the HDCFB are not yet well developed for the complexity of particle distribution and the velocity inside the HDCFB. This article introduces the application of an Electrical Capacitance Tomography (ECT) system to research on HDCFB.

An 8-electrode ECT system is used for imaging the different parts of a HDCFB riser, which has the diameter and height of 90mm and 5700mm respectively. The particles inside are glass beads with a 70 micron diameter. The superficial circulating wind speed ranges from 5m/s to 15m/s, and particle circulation ranges from 380kg/m2.s to 850kg/m2.s.

The average vibrating factors on different areas of the cross section of the riser are calculated by using the wavelet decomposition method, with energy computing in different frequency bands, which is corresponding to the particle velocity. Both average particle densities and vibration factors are compared at different radii in the round cross section, which shows the characteristics of both particle distribution and movement in the different position of the HDCFB riser. The related result will help in understanding the asymmetrical flow system in the riser and giving up the intuition-based expression of particle action.

Keywords Electrical Capacitance Tomography, Circulating Fluidized Bed, Wavelet Analyzer.