Friction between co-current upward gas-solid flow and column wall

Friction between co-current upflow gas–solid flow and column wall was investigated by measuring apparent solids concentrations and actual ones in two circulating fluidized bed (CFB) risers with fluid catalytic cracking (FCC) and sand particles, respectively. A new model to predict frictional-pressure drops between the gas–solid flow in the fully developed zone and the column wall was developed. The results show that the friction between the gas–solid flow and the riser wall causes a significant deviation of the apparent solids concentration from the actual ones, especially under those operating conditions with higher superficial gas velocities and solids-circulation rates. When superficial gas velocities are greater than 8 m/s, the apparent solids concentrations in the fully developed zone of the risers can be greater than 60% of the actual ones. Particle diameters have different influences on the frictional-pressure loss under different superficial gas velocities. After the frictional-pressure drops predicted by the proposed model are deducted from the measured total pressure drops, the predicted actual solids concentrations agree well with the measured actual ones. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.