Transport characteristics (impeller power, gas hold-up, volumetric mass transfer coefficient) are measured both in laboratory-(DN300) and in pilot-scale (DN600) vessels using various impeller types and sizes as well as various liquid phases. Both micromixing and macromixing is experimentally studied.
Dynamic pressure method
The volumetric mass-transfer coefficient kLa is measured as the response of the tracer gas (usually oxygen) concentration in liquid on the steep change of the tracer gas partial pressure in bubbles. If the change of the partial pressure is achieved by change of the gas entering the vessel the response is significantly affected by the residence time distribution of the original gas bubbles influencing the values of kLa measured. The dynamic pressure method developed by our research group is based on a steep change of the pressure above the bubbled vessel causing imminent change of the tracer gas (oxygen) partial pressure in all bubbles in the batch avoiding the complications mentioned above.
Linek, V.; Benes, P.; Vacek, V., 1989. Dynamic pressure method for kla measurement in large-scale bioreactors. Biotechnology and Bioengineering 33(11), 1406–1412.Linek, V.; Moucha, T.; Dousova, M.; Sinkule, J., 1994. Measurement of kLa by dynamic pressure method in pilot-plant fermentor. Biotechnology and Bioengineering 43(6), 477–482.
Mass-transfer mechanism
The mass-transfer mechanism in gas-liquid dispersions is studied enabling deeper understanding of the mass-transfer process and the development of reliable methods for prediction of kLa.
Linek, V.; Kordac, M.; Fujasova, M.; Moucha, T., 2004. Gas–liquid mass transfer coefficient in stirred tanks interpreted through models of idealized eddy structure of turbulence in the bubble vicinity. Chem. Eng. Proc.: Process Intensification 43(12). 1511-1517.Linek, V.; Moucha, T.; Kordac, M., 2005. Mechanism of mass transfer from bubbles in dispersions: Part I. Danckwerts’ plot method with sulphite solutions in the presence of viscosity and surface tension changing agents. Chem. Eng. Proc.: Process Intensification 44(3). 353-361.Linek, V.; Kordac, M.; Moucha, T., 2005. Mechanism of mass transfer from bubbles in dispersions: Part II: Mass transfer coefficients in stirred gas–liquid reactor and bubble column. Chem. Eng. Proc.: Process Intensification 44(1). 121-130.
Design and scale-up of industrial bubbled vessels
The methodology is developed for the design of industrial vessels according to individual demands, as mixing intensity (macromixing-sufficient homogenisation) or gas-liquid mass transfer intensity (micromixing, e.g., sufficient oxygen supply of biomass in fermentation broth). The experimental data are published in form of semi-empirical correlations enabling the transfer of the laboratory- ans pilot-scale characteristics into the industrial scale.
Linek, V.; Moucha, T.; Rejl, F.J.; Kordac, M.; Hovorka, F.; Opletal, M.; Haidl, J., 2012. Power and mass transfer correlations for the design of multi-impeller gas–liquid contactors for non-coalescent electrolyte solutions. Chem. Eng. J. 209. 263-272.Moucha, T.; Rejl, F.J.; Kordac, M.; Labik, L., 2012. Mass transfer characteristics of multiple-impeller fermenters for their design and scale-up. Biochem. Eng. J. 69, 17-27.Labik, L.; Moucha, T.; Petricek, R.; Rejl, F.J.; Valenz,L.; Haidl, J., 2017. Volumetric mass transfer coefficient in viscous liquid in mechanically agitated fermenters. Measurement and correlation. Chem. Eng. Sci.