Three-dimensional axial dispersion of gas-solid fluidized beds using 8-plane electrical capacitance volume tomography

Abstract

Due to the complex flow characteristics and opaqueness of gas-solid fluidized beds, the axial behavior of circulating fluidized bed (CFB) risers is not entirely understood. A 32-electrode electrical capacitance volume tomography (ECVT) system with eight planes was developed to investigate the three-dimensional axial dispersion of gas-solid flow in a CFB riser. To maximize the imaging length in the axial direction, the 32-electrode ECVT sensor was designed with eight planes, with each plane containing four electrodes. The ratio of the axial imaging length to the sensor inner diameter was 8.3. We developed a 32-channel ECVT data acquisition system with an imaging speed of 120 frames per second to record the data of the ECVT sensor. Experimental results show that this ECVT system can effectively collect the flow details in the axial direction. The flow changed from slug flow to bubble flow when the fluidizing gas velocity Uf was adjusted from 2.34 m/s to 0.56 m/s. The distribution of the solid fraction, the velocity of the slug/bubble in the axial direction and the slug length were extracted from the 8-plane ECVT images to reveal the flow characteristics of the CFB riser.