Gas absorption in an agitated gas-liquid-liquid system

Gas-liquid-liquid systems have gained interest in the past decade and are e ncountered in several important industrial applications. In these systems a n immiscible liquid phase may affect the gas absorption rate significantly. This phenomenon, however, is not completely understood and underlying mech anisms need further study. In this work the well-known Danckwerts-plot tech nique is used to determine the liquid side mass transfer coefficient k(L) a nd the gas-liquid interfacial area a simultaneously in this type of systems . As absorption/reaction system CO2 absorption in a 0.5 M K CO2/0.5 M KHCO3 buffer solution catalysed by sodium hypochlorite was chosen. Toluene, n-do decane, n-heptane and 1-octanol were applied as dispersed liquid phases. Th e Danckwerts-plot could be well used in gas-liquid-liquid systems and from the results it appeared that two types of systems exist; systems that enhan ce mass transfer and systems that do not enhance mass transfer. Effects at low dispersed phase hold-up were observed to be very strong and are thus im portant, but were not taken into account in further analysis of the effect of dispersed phase hold-up on mass transfer. In systems where dodecane and heptane were added to the buffer solutions no enhancement of mass transfer was observed. However, the addition of toluene and 1-octanol caused an enha ncement of mass transfer that could be well described using a homogeneous m odel of the shuttle mechanism. (C) 2001 Elsevier Science Ltd. All rights re served.