Comparison of single and double inert tracer fluctuation measurements in a continuous stirred tank

Abstract

A comparison is made between two different methods using laser induced fluorescence spectroscopy for measuring local concentration fluctuations in the same stirred tank. The first method using a single inert fluorescent tracer yields a segregation index quite different from that determined by the second method, which requires two inert tracers, a fluorescent one and a fluorescence quencher. By recalling the theoretical background, it is demonstrated that the characteristic segregation indices should be equal for the experiments under consideration. According to the discussion, it is likely that the double tracer method gives more reliable results.

Investigation by laser Doppler velocimetry of the effects of liquid flow rates and feed positions on the flow patterns induced in a stirred tank by an axial-flow impeller

“…Although quite a few publications have dealt with several aspects of the operation of continuous-ow single-or multi-phase stirred vessels (see for example Greenhalgh, Johnson, & Howard, 1959;Patterson, 1975;Aubry & Villermaux, 1975;Barthole et al, 1982;Benayad, David, & Cognet, 1985;Mahouast, David, & Cognet, 1987;Gaskey, Vacus, David, Andrà e, & Villermaux, 1988;Gaskey, Vacus, David, & Villermaux, 1990;Mahouast, 1991;Mahouast, Nardin, El Rhassouli, & Rondot, 1991;David & Andrà e, 1993;Houcine, Vivier, Plasari, David, & Villermaux, 1994, 1996Magelli, Nocentini, Orlandini, Fajner, & Pinelli, 1997;Konishi, Kogasaki, & Asai, 1997;Bomben, Selva, Tundo, & Valli, 1999;Distelho & Marquis, 1999 or similar process vessels, e.g., rotating-disk contactors (Fei, Wang, & Wan, 2000), as well as with the identiÿcation of the ow patterns in batch stirred vessels for various agitators using sophisticated experimental techniques like laser Doppler velocimetry (LDV), laser-induced uorescence (LIF) and particle image velocimetry (PIV), among others (Mezaki, Mochizuki, & Ogawa, 2000; see also Mavros, Xuereb, & Bertrand (1996) and Mavros (2001) for an extensive list of related references), little work seems to have been done to investigate the low patterns in such vessels (see Kemoun et al, 1997;Mavros, Naude, Xuereb, & Bertrand, 1997;Zannoud, Guiraud Costes, & Bertrand, 1991;Mavros, Barruà e, Xuereb, FoÄ rt, & Bertrand, 2000).…”