Particle shape, density, and size effects on the distribution of phase holdups in an LSCFB riser

Electrical resistance tomography (ERT) as a non-invasive technique based on conductivity measurement of the continuous phase was employed for the study of phase holdup in a liquid-solid circulating fluidized bed (LSCFB). Local solid holdup was also measured by an optical fibre probe and pressure transducers to compare and verify the results obtained by ERT. Good agreement was observed among the three methods. Tap water was used as the continuous and conductive phase and glass beads (spherical shape) and lava rocks (irregular shape) of two different sizes were used as the solid and non-conductive phase. Radial non-uniformities of solid holdups were observed for all four types of particles under different superficial liquid velocities in different axial locations. The solid holdup was higher in regions close to the wall and low in the central region. Non-uniformity in the phase holdup decreased with increasing liquid velocity. The axial flow profile was found uniform along axial locations of the riser except at the lower location closer to the distributor zone.