ECVT study of 3D flow characteristics at L-shaped exit of CFB riser

Abstract

Riser exit of the circulating fluidized bed (CFB) has a complex structure, which makes it difficult to capture the characteristics of gas-solid flow. Besides, the axial behavior of CFB exit of the riser has not been entirely understood. In this paper, electrical capacitance volume tomography (ECVT) was used to study the characteristics of gas-solid flow in the L-shaped exit of the CFB riser, and a 32-electrode ECVT data acquisition system was developed with an imaging speed of 100 frames per second. As a result, the solid concentration, the characteristics of solid frequency, the solid velocity, and the solid flux were extracted from the ECVT images. When the gas velocity Uf was adjusted from 2.29 m/s to 0.83 m/s, the particles in the L-shaped exit of the CFB riser changed from dispersed flow to aggregative flow, and the solid flux decreased. Finally, the concentration distribution of solid was simulated in the CFB according to the Eulerian-Eulerian multiphase flow model. In the exit of the CFB riser, the experimental ECVT results and the numerical simulation results demonstrated good agreement in terms of particle flow patterns.