To investigate the pressure drop due to the friction between gas-solid suspension and CFB riser wall and its effect on the measurement of average solids holdups by pressure transducers,models for predicting the pressure drop and the solids holdup were developed.Experiments were carried out by using FCC and sand particles in two CFB risers with 15.1 m and 10.5 m high,respectively.By comparing the apparent solids holdups obtained form the pressure gradients and the actual solids holdups,it was found that the friction cannot be omitted when the pressure gradients are converted to the solids holdups,since the friction causes a deviation of the apparent solids holdup from the actual one.When the superficial gas velocity is above 8 m/s,the deviation reaches up to 30%～50%.The models yield the predicted results in good agreement with the experimental data.
