Influence of acoustic waves on the solids dispersion in a gas-solid CFB riser: Numerical analysis

Abstract Ultrasonic waves were applied to improve the gas-solid flow homogeneity in CFB risers. The aim of this study is to verify if applying ultrasound in the radial direction of a lab-scale CFB riser improves the solids distribution along its cross-section. The best geometrical configuration of an ultrasonic device with a frequency of 40 kHz applied to a lab-scale CFB riser was defined with a design of experiments. Seven variables were manipulated: the number of transducer rows, transducers per row, transducer diameter, the axial position of the device in the riser, sound pressure level, gas velocity, and solids mass flux. Numerical simulations were performed using the URANS-k-epsilon-KTGF model. Ultrasonic waves propagation were described using a jet flow approximation. The best solids distribution was found with 20 transducers of 120 dB and 16 mm diameter, which reduced the solids dispersion coefficient in 50% and reduced the pressure drop and the solids inventory.