GAS-SOLID FLOW BEHAVIOR IN A PRESSURIZED HIGH-FLUX CIRCULATING FLUIDIZED BED RISER

Abstract

Gas-solid flow behavior was investigated in a high-flux circulating fluidized bed (HFCFB), whose riser is 0.068 m ID and 5.2 m high. Experiments were carried out at different pressures (0.1–0.5 MPa), solids mass fluxes (122–1015 kg/m2 · s), and standard state superficial gas velocities (6–40 m/s). Geldart group B particles 137 µm in diameter and 2490 kg/m3 in density were used as bed materials. Information on pressure drop, apparent solids holdup, average slip velocity, and solid-to-air mass flow ratio were systematically tested at elevated pressures. The results showed that increase of the operating pressure led to higher total riser pressure drop and solids holdup, lower slip velocity, more homogeneous pressure drop, and longitudinal solids holdup distribution. As a result, a high-density condition with Geldart group B particles, i.e., solids holdup in the riser over 10%, could be successfully formed in the HFCFB at elevated pressure. Similar to the trend at atmosphere, the dimensionless slip velocity at pressurized condition increased with increasing solids holdup for any given superficial gas velocity, and the total riser pressure drop increased approximately linearly with solids-to-air mass flow ratio at the given operating pressure.