(653g) Particle Phase Behavior Experimental Analysis on a Pilot Scale CFB Riser Using Phase Doppler Anemometry

The particle phase concentration and diameter distributions are quite important data of gas-solid multiphase flows to modeling validation. Measurements of the relationship between them and solids velocity can be useful to the fluid dynamics understanding and analysis of the relevant phenomena impacting on particles flow. Mainly in circulating fluidized beds (CFBs) applications, where commonly a very large number of particles are present, an appropriate definition of the mathematical modeling is imperative. In this way, experiments were carried out in three axial locations of the Pilot Unit of Riser and Cyclones: near the solids inlet, in the middle riser section, and near the top riser section. Phase Doppler Anemometry, a high accuracy, minimally intrusive technique, was used to measure the solids axial velocity, particles concentration and particle diameter, in 17 points of each cross section. 5,000 measurements were acquired in triplicate at each point, under turbulent flow conditions and dilute particles loadings (Gs=4 – 12kg/m²s) since the study of typical riser phenomena under these conditions is one of the objectives. Results show the relationship between particles velocity and concentration, as well as particles diameter. An asymptotic behavior is found relating solids velocity and concentration: low concentration allows for high velocity, although very high concentrations with low particles velocity are found along the riser. Negative particles velocities were found mainly at the bottom region regardless of particle diameter. The particles diameter and velocity variations are presented by means probability density distributions that show a prominent occurrence of inertial particles near the wall while smaller particles are more present in the center of the riser. An unexpected axial segregation of particles diameter was also found.

Keywords: Circulating Fluidized Bed. Phase Doppler Anemometry. Particles concentration.