Measurement of mass transfer coefficient in an airlift reactor with internal loop using coalescent and non‐coalescent liquid media

Abstract

In this work the sulfite oxidation (SOM), dynamic pressure-step (DPM) and gassing-out (GOM) methods were compared for volumetric mass transfer coefficient measurement in an airlift reactor with internal loop. As a liquid phase both, non-coalescent and coalescent media were used. Among the methods discussed here, the mass transfer coefficient (k L a) values obtained by the DPM appear as the most reliable as they were found to be independent of oxygen concentration in the inlet gas, which confirmed the physical correctness of this method. The difference between data measured using air and oxygen was not higher than 10%, which was comparable to the scatter of experimental data. It has been found that the sulfite oxidation method yielded k L a values only a little higher than those obtained by the DPM and the difference did not exceed 10%. Up to an inlet gas velocity (U GC ) of ∼ =0.03 m s −1 the GOM using oxygen as a gas medium gave k L a values in fact identical with those obtained by the DPM. At higher flows of the inlet gas, the GOM yielded k L a values as much as 15% lower. The enhancement in oxygen mass transfer rate determined in non-coalescent media was estimated to be up to +15%, when compared with a coalescent batch. The experimental dependence of k L a vs the overall gas hold-up was described by an empirical correlation.

Measurement of Volumetric Mass Transfer Coefficient in Bubble Columns

“…The correlations were obtained by fitting all the gas holdup and kLa data determined using ideal, non-ideal pressure step, air and pure oxygen absorption. Similar results, concerning the agreement between data obtained with pure O 2 absorption and air absorption both in coalescent and non-coalescent batches, were observed also by other authors [22,26,29,30]. Linek and co-workers compared results obtained in laboratory (0.29 m in diameter in [22]) and pilot-scale stirred tank reactors (0.6 m in diameter in [26]) and in both cases, the DPM provided physically correct k L a data within a reasonable data scatter.…”

“…Linek and co-workers compared results obtained in laboratory (0.29 m in diameter in [22]) and pilot-scale stirred tank reactors (0.6 m in diameter in [26]) and in both cases, the DPM provided physically correct k L a data within a reasonable data scatter. The same conclusion was presented by Blazej and co-workers for internal loop air-lift reactor [29,30].…”

“…During pure oxygen absorption, there is no problem with driving force description in the model, thus the resulting k L a should be physically correct. On the contrary, the modeling of air absorption is more complicated and neglecting the nitrogen transport can cause significant underestimation of k L a data especially in non-coalescent batch at high gas flow rates [21,22,25,26,30].…”

“…The DPM was successfully validated for stirred tank reactors [22,23,26] and for internal loop air-lift reactors [29][30][31]. In bubble columns, the DPM was applied by Letzel et al, 1999 [12].…”

Determination of the average shear rate in a stirred and aerated tank bioreactor

“…The volumetric oxygen transfer coefficient (k L a) was determined by the dynamic pressure-step method (DPM) [3]. In this experimental method, the pressure in the vessel is changed abruptly by approximately ±15 kPa, and an increase in the dissolved oxygen concentration (Ce) from Ce to Ce 0 in the bulk liquid phase occurs regardless of the gas flow pattern.…”