Power and mass transfer correlations for the design of multi-impeller gas–liquid contactors for non-coalescent electrolyte solutions

Power dissipated and volumetric mass transfer coefficients were measured for single-, double- and triple-impeller configurations of Rushton turbines in the gas–liquid pilot plant vessel of diameter of 0.6 m using a fully non-coalescent (0.5 M Na2SO4) non-viscous batch. Physical relevance of the kLa data measured by the dynamic pressure (DPM) and the classical dynamic methods (CDMs) were tested experimentally and was found that the CDM seriously underestimates the data in the pilot plant vessel for kLa > 0.03 s−1. Problems of the measurement and evaluation of physically sound kLa data at high absorption rates in the non-coalescent gas–liquid dispersions are discussed and some consequences of the application of the defective kLa are shown. The DPM was used to measure kLa in the individual sections of the vessel and their mutual differences are explained in terms of exchange liquid flow between sections. Unified correlations of kLa measured in the pilot plant vessel and that measured previously in laboratory vessels (diameter of 0.19 and 0.3 m) were developed and were compared with the data in the literature. The data were most closely fitted by the correlations that include, except of the power dissipated and the gas flow-rate, the circumferential agitator speed.

► Gas–liquid mass transfer coefficients kLa are measured in multi-impeller vessels.
► Classic dynamic method seriously underestimates kLa measured in noncoalescent batch.
► Correctness of dynamic pressure method, used in the work, is verified.
► Correlations are proposed to predict kLa in up to three-impeller vessels.
► Data from vessels diameters of 0.19, 0.3 and 0.6 m were used.