Correlation and prediction of solids holdups of gas-solid two-phase flow in fully developed region of CFB risers

To investigate the solids holdups in fully developed region of CFB risers, experiments were carried out in two CFB risers with the heights of 15.1 m and 10.5 m, respectively. FCC particles (Geldart A) and sand particles (Geldart B) were used in the experiments and the solids holdups were calculated by using measured pressure gradients. The experimental results obtained from 175 sets of operation conditions, under which the lengths of fully developed section are longer than 2.8 m, show that when the superficial gas velocity is between 3 m · s^-1 and 8 m · s^-1, it has a significant effect on the variations of the average solids holdups in fully developed region with the terminal solids holdups, but when it is less than 3 m · s^-1 or greater than 8 m · s^-1, the effect becomes inappreciable and the average solids holdups vary linearly with the terminal solids holdups. By taking into account the effects of superficial gas velocity, particle properties and riser geometry, a new empirical correlation for the average solids holdups in fully developed region of CFB riser were developed, which is in good agreement with the experimental data of this work and accords with the correlations reported in literatures.