Using of the dynamic pressure-step method for mass transfer coefficient measurement in the internal-loop airlift reactor

The principle of the dynamic pressure-step method, consists in simultaneous measurement of both the oxygen concentration and the total pressure in the internal-loop airlift reactor (ALR). After reaching steady oxygen concentration in liquid (0.3 M-Na2SO4 Solution) at the atmospheric pressure, the pressure in the column was increased by about 15 kPa. The pressure in the column changed in about 10-15 s, therefore this method is called the non-ideal pressure-step method. Then, the instantaneous values of both the column pressure and the oxygen concentration could be used for calculation of instantaneous driving force for the oxygen mass transfer without the need of immediate pressure step. Measurements were carried out in the ALRs with a working volume of 40 dm. Pure oxygen, air, and 0.3 M-Na2SO4 aqueous solution were used as the model gas and liquid media. Measurements showed very good agreement between k(L)a values measured with air and pure oxygen, respectively in the whole range of used superficial velocities of input gas. Further experiments proved instantaneous change of oxygen concentration in the whole volume of liquid phase. Measured data were described by correlation based on superficial gas velocity of the input gas and by linear dependence on overall gas hold-up in the liquid.