Effect of impeller blade number on KlA in mechanically agitated vessels

Abstract

Effects of impeller blade number on gas dispersion and mass transfer rate were thoroughly investigated for mechanically agitated vessels equipped with 2-, 4-, 6- and 8-straight blades disk turbine impellers. The results show that under the same rotational speed, the impeller with more blades always can disperse gas more effectively, which induces a higher value of . However, with the same total power consumption, the 4-blade impeller can obtain a higher value than the 6- and 8-blade impellers under a lower gassing rate condition (Qg values for the triple stage 6-blade impeller system (3x6) and quadruple stage 4-blade impeller system (4×4). From the experimental results, it can be found that the 4×4 system gives higher value than the 3x6 system under gas completely dispersed conditions. By correlating withn b , N and Vs, the following correlation can be given as: $$K_L a > = 0.00119n_b^{0.62} N^{1.56} V_s^{0.4} $$ or $$ = 0.0297n_b^{0.1} (Pg/V)^{0.34} V_s^{0.48} $$ These two correlations can also be used to evaluate the mass transfer coefficient of each impeller region for the multiple impeller systems and the deviation is always less than 10%.