Gas‐phase properties in stirred tank bioreactors

Abstract

Bubble properties in stirred tank bioreactors equipped with standard radial flow Rushton turbines have been investigated. Bubble velocity patterns within a stirred tank reactor were derived from measured local bubble velocity distributions. Local information on specific interfacial areas, bubble number densities and bubble diameters together with local gas hold-ups, measured in a model medium at gas flow rates which are employed in practice, is presented. All measurements were performed with two new ultrasound pulse techniques which can be used in model media as well as during real cultivation processes.

Analysis of Gas-Liquid Flow in an Aerated Reactor Equipped with a Coaxial Mixer through Tomography and CFD

“…The mentioned limitations regarding the invasive techniques can be overcome by adopting non-intrusive approaches. With respect to non-intrusive characteristics, several methods have been reported such as ultrasonic (Supardan et al, 2004;Utomo et al, 2001;Chaouki et al, 1997;Fischer et al, 1992), electrical capacitance tomography (Warsito and Fan 2001;Chaouki et al, 1997;Halow, 1995), electrical resistance tomography (ERT) (Kazemzadeh et al, 2017;Wang et al, 2000;Chaouki et al, 1997) ,and X ray and  ray (Ford et al, 2008;Khopkar et al, 2005;Thatte et al, 2004). By comparing the suggested invasive and noninvasive measuring techniques and also by considering their limitations and drawbacks, the noninvasive electrical resistance tomography (ERT) has been found to be a superior technique to perform the flow visualization and to obtain the local gas holdup values due to its low cost and simplicity (Scott and McCann, 2005) and also in contrast to the radiation based tomography methods; it is safe for the experimenter (Mann et al, 1997a(Mann et al, , 1997b.…”

Measuring Techniques in Gas—Liquid and Gas—Liquid—Solid Reactors

“…• frequency analysis of the reected wave (Doppler eect): US Doppler anemometry is based on the dierence in frequency between an emitted US pulse and the corresponding received US pulse that has been reected by a moving bubble. This well-known method leads to the local bubble velocity distribution (Br oring et al, 1991;Yao et al, 1991;Fischer, Br oring, & L ubbert, 1992;R uer, Br oring, & Sch ugerl, 1995). Its principle is shown on Fig.…”

Measurement of Gas Hold-up Profiles in Stirred Tank Reactors by Gamma Ray Attenuation Technique

“…The presence of cavities behind the stirrer blades leads to an increase in the local gas hold-up in that region. Fischer et al 9 also measured the bubble size distribution and interfacial area in an aerated stirred tank reactor with a standard Rushton turbine with ultrasound pulsed Doppler technique. Their results support the earlier observations of having high gas fraction near the impeller tip.…”

“…With this information, the local rates of heat and mass transfer can be estimated, the local bubble size can be predicted, and in turn the overall performance can be estimated. Local fractional gas hold-up in two/three phase stirred tank reactors has not been reported by many authors, but there have been many attempts to measure the bubble size distribution, interfacial area and overall average holdup [5][6][7][8][9] . There have been very few attempts to model the local gas hold-up pro les mathematically.…”