Wavelet Enhanced Visualization of Solids Distribution in the Top of Circulating Fluidized Beds

X. Xiong1, Z. Zhang1, S. Liu2 and J. Lei3

1National Natural Science Foundation of China, 83 Shuangqing Road, Haidian Dist. Beijing 100085, China

2School of Energy and Power Engineering, North China Electrical Power University, Email: s.liu@mail.etp.ac.cn

3Institute of Engineering Thermophysics, Chinese Academy of Sciences

ABSTRACT

Electrical capacitance tomography (ECT) technique is used for measuring the solids distributions in the exit zone of a circulating fluidized bed (CFB). Wavelet method is applied in de-noising and image enhancement and its effects are found in two aspects: (1) the influence of noise in the raw data can be reduced in the reconstructed ECT images and, (2) the edges of the images can be significantly smoothed by wavelet functions, which is valuable for edge shape improvement of the images reconstructed under coarse pixel divisions. Experimental measurements were carried out and wavelet method was applied. The data revealed the important features about the exit zone of CFBs, i.e. the core-annulus flow pattern, the high concentration in the corners of the CFB riser and most importantly, the high solids concentration near the exit of the CFB.

Keywords Wavelet, ECT image reconstruction, flow visualization