Effect of riser geometry structure on local flow pattern in a rectangular circulating fluidized bed

Abstract

By using a high-speed video camera and particle image velocimetry (PIV) technique, the local flow properties of the solid-gas two phases flow were studied in a plexiglass rectangular CFB cold model with the a riser of 1.5×0.864×4.9m3. Measurements were carried out with transparent spherical glass bead between 0.1-0.425mm as bed materials and cold air as flow medium. The experimental results showed that the secondary air has an important influence on the particle velocity distribution. Because of the secondary air penetrating effect, the particle lateral movement was acute. In the dilute region, the outlet and the corner effect induced the defluxion of the particles movement and the core-annular distribution was broken. The closer to the outlet, the stronger the lateral velocity is. The obstruct of hanging screen reduced the furnace outlet effects between the hanging screen and the front wall, where the particle movement in the area was controlled by the gas flow and the constrain of the wall. High particle concentration areas were formed in the junction between the screen and the front wall and in the corner between the left wall and the front wall.