Gas-solid flow in a ring-baffled CFB riser: Numerical and experimental analysis

Abstract Circulating fluidized beds (CFBs) are used in a variety of industrial applications in which the homogeneous distribution of the solid phase is desirable. The core-annulus concentration profile is a characteristic of the flow profile in these devices and it leads to solids concentration near the wall. The use of airfoil-shaped ring-type baffles is an alternative to improve the solids distribution in the cross section of CFB risers. In this study, the solids velocity and volume fraction profiles were obtained by PDA measurements and used to validate a computational fluid dynamics (CFD) model. Improvements in the solids distribution are evaluated using a statistical coefficient of variation. The results demonstrate that the ring baffles increase the solids velocity near the wall and redirect the particles to the riser center. The more homogeneous distribution of the particles in the radial direction, shown by both the experimental and numerical solids volume fraction coefficients of variation, improves the gas-solids contact and consequently could increase the yield and selectivity of products of the chemical reactions. In addition, it was found that the insertion of the ring baffles caused a pressure drop reduction in the riser flow. This study enables the investigation of the solids distribution in CFB risers in large scale.