Advances in Water Treatment and Enviromental Management

MEASUREMENTS OF MASS TRANSFER IN A BUBBLE COLUMN 151The results for all measurement conditions and both grid types TO and T1 areshown for the oxygen concentration in water in Fig. 9 and 10 as a function of thevoid fraction ß and also for oxygen efficiency in air in table 2. Figure 9 shows thatthe influence of the grid types TO and Tl occurs in all water flow rates Q w . At thelowest air flow rate Q a =0.1.10- 3 m 3 /s the results of the oxygen measurements areapproximately similar for both grid conditions (k~0.01 l/min). With an increasingQ a the difference between the k-values without and with grid also increases. ForQ a >0.55·10 -3 m 3 / s the curves taken from the experimental data with the grid show anearly asymptotic behaviour.Fig. 9a: Overall Volumetric Mass-Transfer Coefficient k L· a for DifferentWater Flow Rates without and with the GridFig. 9b: Overall Volumetric Mass-Transfer Coefficient k L· a as aFunction of Air Flow Rate without and with the Grid