Relationship between Solid Flow Rate and Pressure Drop in the Riser of a Pressurized Circulating Fluidized Bed

The relationship between the solid circulation rate and the pressure drop in the riser of a pressurized circulating fluidized bed (CFB) was investigated. The pressure drop of the riser was measured based on variations in the pressure, gas velocity, solid flux, and particle diameter using glass beads as the bed material. The pressure drop of the riser was shown to decrease as the pressure increased. Under the gas flow conditions, the momentum per unit mass of the gas used to accelerate the solid particles was shown to be finite. The time required for the gas to accelerate the solid increased linearly with the solid circulation rate under the given gas flow conditions because the gas momentum shared per unit mass of the particles decreased. Therefore, the pressure drop of the riser increased linearly with the solid circulation rate at the given gas velocity. The slope of the linear relationship is related to the ratio of the momentum flux due to gravitational and buoyancy forces on the solid to the gas momentum per unit mass of gas transferred from the gas to the solid. The transferred gas momentum per unit mass of the gas increased as the gas velocity increased or as the particle diameter or pressure decreased. The gas momentum shared per unit mass of the solids decreased as either the particle density or diameter increased. A correlation that represents the relationship between the pressure drop and the solid circulation rate in the riser of the CFB was successfully proposed.