Development of a methodology for measuring axial and radial dispersion coefficients in multiphase apparatus using volumetric flow modulation (VOLMOD)
Motivation:
Bubble columns are widely used contact apparatuses for heterogeneous catalysis, bioprocesses, exhaust gas, wastewater treatment and many more. The influence of hydrodynamics on the mass and heat transport processes taking place in them is very large but difficult to model completely because the processes involved are nonlinear and cross-scale. In such contactors, the most widely used theoretical approach to describe the gas and fluid phases is the Axial Dispersion Model. Successful implementation of this model requires accurate knowledge of the axial dispersion coefficient of both the liquid and gas phases. Conventional approaches to determine axial dispersion coefficients are based on experimental studies with tracer substances. However, such methods are unlikely to be universally applicable, cause harmful product contamination or process failures and alter the physical properties of the system.
Objectives:
The project aims to further develop and comprehensively apply the methodology of measuring axial dispersion coefficients using volumetric flow modulation for bubble columns. The proposed methodology is completely non-invasive and does not require any tracer substance.
Methods and results:
Instead of using a tracer substance, a marginal sinusoidal modulation is superimposed to the gas inlet flow rate and used as a virtual tracer. This modulation causes a sinusoidal variation of the gas holdup in time, called gas density wave. Dispersion causes amplitude attenuation and phase shift of the gas density wave along the column. Amplitude damping and phase shift can be measured and related to the value of the axial dispersion coefficient. Sinusoidal-resolved gamma-ray densitometry is used to investigate the amplitude damping and phase shift.
Sketch of the working principle and experimental setup of the gas flow modulation
During the project, a procedure was developed for applying flow modulation to a variety of conditions, including the choice of experimental parameters and uncertainty quantification. Flow modulation was tested in a variety of operating conditions and column configurations. The carried-out studies qualified flow modulation as a reliable approach for measuring the axial gas dispersion coefficient in bubble columns.
Publications:
Journal publications
S. Marchini, M. Schubert, U. Hampel
Analysis of the effect of uncertainties in hydrodynamic parameters on the accuracy of the gas flow modulation technique for bubble columns
Chemical Engineering Journal, Vol. 434 (2022): 133478
S. Marchini, A. Bieberle, E. Schleicher, M. Schubert, U. Hampel
Sensing strategies for determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique
Industrial & Engineering Chemistry Research, Vol. 62, Issue 45 (2023): 19225-19237
S. Marchini, A. Bieberle, M. Schubert, U. Hampel
Uncertainty analysis of gamma-ray densitometry applied for gas flow modulation technique in bubble columns
Chemical Engineering Science, Vol. 282 (2023): 119214
S. Marchini, A. Bieberle, M. Schubert, U. Hampel
Guidance for Measuring the Axial Gas Dispersion Coefficient in Bubble Columns via Gas Flow Modulation
Industrial & Engineering Chemistry Research, Vol. 62, Issue 46 (2023): 19936-19950
Conference contributions
S. Marchini, A. Döß, A. Bieberle, M. Schubert, U. Hampel
Investigations on axial gas dispersion coefficients in bubble columns using gas flow modulation
European Conference of Chemical Engineering (ECCE), 20.-24.09.2021, Online conference
S. Marchini, A. Bieberle, E. Schleicher, M. Schubert, U. Hampel
Bewertung verschiedener Messverfahren zur Ermittlung des axialen Dispersionskoeffizienten der Gasphase in Blasensäulen mittels Volumenstrommodulation
Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen, Mechanische Flüssigkeitsabtrennung sowie Zerkleinern und Klassieren, 21.-22.02.2022, Online conference
S. Marchini, A. Bieberle, M. Schubert, U. Hampel
Assessment of the flow modulation technique for measuring axial liquid dispersion coefficients in trickle-bed reactors
Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, 07.-10.08.2022, Ottawa, Canada
S. Marchini, V. Caggia, A. Bieberle, M. Schubert, E. Brunazzi, U. Hampel
Analysis of sparger effects on axial gas dispersion in bubble columns
European Conference of Chemical Engineering, 17.-20.09.2023, Berlin, Germany
S. Marchini, A. Bieberle, M. Schubert, U. Hampel
Applicability of gas flow modulation technique for measuring axial gas dispersion coefficients in bubble columns
European Conference of Chemical Engineering, 17.-20.09.2023, Berlin, Germany