Measurements on the Local Solids Concentration in the Lower Part of a Circulating Fluidized Bed Riser

A study was carried out to investigate local solids concentration distribution in the lower part of a plexiglas rectangular cross-section CFB cold model, with the height of 4.9 m. Local solids concentration of two cross-sections with different geometry structures, were measured under three kinds of operating conditions, by using PC-6D reflective-type optical fiber concentration probe, with cold air as flow medium and transparent glass bead about 0. 372 mm as bed materials. Results showed that with the increase of primary air, solids concentration decreased in the lower zone, and increased in the upper transition region. Secondary air injection strengthened the disturbance in the flow field, which can improve the gas- solid mixing, then, solids concentration distribution was changed remarkably. Being conditioned by expanding cross-section of rear wall, solids concentration distribution was not centrosymmetry, concentration besides rear wall slightly lower than front wall. Solids concentration of the just secondary air injection plane became lower, with secondary air injection. Projection section in transition zone changed the movement orientation of abundant adherent downflow, and solids gathered on the step, aggravating the erosion to the wear strip. Part of the particles fell down the external face of the wear strip, come into being high concentration under it.