Mixing Efficiency of Shaking Vessel with Various Motions

Abstract

The flow pattern, the mixing process, the power consumption, the particle suspension and the mass transfer coefficient were measured in rotary, the reciprocal and the figure-eight shaking vessels. For the figure-eight shaking, the fluid flow changed at the transition frequencies of the flow, N_tr1, N_tr2 and N_tr3. The flow in the shaking vessel was a progressive wave type between N_tr1 and N_tr2. The steady rotational flow was generated between N_tr2 and N_tr3. Finally, the rotational flow disappeared when the frequency was larger than N_tr3. Similar results were obtained in the reciprocal shaking. These flow transition frequencies N_tr1, N_tr2 and N_tr3 were correlated with Re(=Nd²/ν) and Fr(=N²D/g). The region of the optimum operating condition of the figure-eight shaking was larger than that of the reciprocal shaking. The mixing process of the figure-eight shaking was similar to that of the reciprocal shaking between N_tr2 and N_tr3. The effect of shaking frequency on power consumption P of the reciprocal and the figure-eight shaking was very complicated. However the power consumption of the rotary shaking increased monotonously frequency with increasing. The shaking frequency for complete suspension of particles N_JS was larger than N_tr2. Because most particles did not suspend from the vessel bottom when the shaking frequency was larger than N_tr3, the solid-liquid mass transfer coefficient k_L decreased. The gas-liquid mass transfer coefficient K_La of the reciprocal shaking did not increase with increasing the shaking frequency, while K_La of the rotary shaking increased with the increase in the rotational frequency, because the power consumption did not increase. It was found that the rotary shaking was the best for the stable operation, because the rotary shaking can produce the steady rotational flow, which was necessary for liquid mixing. However, when the rotary shaking was not suited for the gas absorption or the sensitive mixing, the reciprocal shaking was better than the rotary shaking.