(109d) Development of a Standardized Method for Mass Transfer Measurements in Absorption and Desorption

Development of
a standardized method for mass transfer measurements in absorption and
desorption

A. Kunze¹, P. Lutze¹, M. Kopatschek², S.
Müller², M. Grünewald², A. Górak¹

¹ TU Dortmund University, Laboratory
of Fluid Separations

Emil-Figge-Strasse
70, D-44227 Dortmund, Germany

Phone: +49 (0) 231 755-3034, E-Mail:
anna-katharina.kunze@bci.tu-dortmund.de

² University of Bochum, Chair of Fluid Separations

Universitaetsstrasse 150,
D-44780 Bochum, Germany

Due to the rising use of rigorous
models for designing absorption and desorption processes a coherent method for
mass transfer parameter determination must be developed. Currently, a
comparability of mass transfer parameters investigated experimentally at
different sights or different columns is not existent. Additionally, there is
hardly one method to evaluate mass transfer parameters determined in the past,
because often important information about the measurements and calculation is
missing. That leads to the effort of a standardized experimental and calculation
method for determination of mass transfer parameters in absorption and
desorption. The main focus is to increase transparency and comparability for
mass transfer parameters on gas and liquid side β_G und β_L
and the effective interfacial area a_efffrom different authors^[1,2].
This will lead to a decrease in necessary safety factors resulting in a cost
and resource optimized column design.

A consortium of 14 industrial
partners, including manufacturers and users of packings,
as well as two academic partners are working on this standard method in Europe.
The first step of the standard method is to figure out an experimental method
to achieve coherent results on pilot plant scale. Therefore, concentration measurements on different plants are carried out to
calculate the volumetric mass transfer parameters (β_G^.a_eff) and (β_L^.a_eff).
The method is developed for structured and random packings.
During the development of an experimental method the main focus is on the configuration
of the setup. Detailed investigations concerning the influence of e.g. gas and
liquid distributors, packing height, and taking samples is carried out. The
experiments for the experimental method are carried out in two columns with a
diameter of 288 mm, which have exactly the same configuration. The experimental
method will then be adapted additionally to a column with a higher diameter to
carry out further experiments.

In addition a mathematical tool
is necessary, which guarantees a consistent calculation of mass transfer
parameters for rigorous modeling. The stepwise data processing from the
experimental data to gain parameters for rigorous modeling is described in Figure
1.

Figure 1: Pathway for the
determination of model parameters of rigorous absorption models.

Based on the experimental data
the first step is to define the volumetric mass transfer parameters (β_G^.a_eff)
and (β_L^.a_eff).
To take temperature and concentration dependence of the chemical system data
into account, a detailed analysis of possible calculation methods is carried
out. To define the temperature and concentration dependence of the phase equilibrium,
at least seven basic system data (such as vapor pressure as well as density,
viscosity and diffusion coefficients in gas and liquid phase) have to be
calculated. To minimize the calculation effort, a global sensitivity analysis
is carried out. For the most sensitive parameters, different calculation
methods are compared. In addition, also the experimental data are implemented
in the sensitivity analysis to determine the influence of deviations in each
measured value.

A combination of three chemical
systems is necessary to determine β_L,
β_Gand a_eff, one of the following
properties has to be fulfilled by one of the systems:

-      
mass transfer resistance on liquid side for β_L

-      
mass transfer resistance on gas side for β_G

-      
fast reaction pseudo first order for interfacial area
a_eff

Via correlation of interfacial
area between the three different chemical systems the phase specific mass
transfer parameters can be determined.

Within this presentation, the
detailed results of the analysis of equipment parameters, the method in general
as well as the mathematical tool will be shown.

This work is part of GVT
funded project ?Standardization of mass transfer measurements in absorption and
desorption?.

Literature

[1]    A. Hoffmann et al., ?Standardization
of mass transfer measurements: A basis for the description of absorption processes?,
Chemical Engineering Research and Design 2007,
85 (1), 40-49.

[2]   J.F. Rejl
et al., ?Methods standardization in the measurement of mass-transfer
characteristics in packed absorption columns?, Chemical Engineering Research
and Design 2009, 87 (5), 695-704.