Electronic Material Properties - und Geowissenschaften ...

tower stripping, and therefore much lower strip-gas to water flow ratios are needed for
an effective stripping.
The removal of 12 organic contaminants from water using a HFM module was studied
under low strip gas flow to water flow ratios (up to 5:1). Removal efficiencies were found
to be strongly dependent on the Henry’s law constants indicating a substantial mass
transfer resistance on the gas side. Vacuum can be either used to increase removal
efficiencies, or to decrease the amount of strip gas that has to be treated without
sacrificing efficiency (Fig. 2).
The conventional resistance in series model was inapplicable to predict mass transfer
coefficients in our experiments as it assumes, that at least for the operation conditions
used here, the liquid side mass transfer resistance dominates the overall resistance for
all compounds (Fig. 3, left). Therefore, a new hybrid numerical and analytical modeling
approach in the finite element simulator RockFlow/GeoSys for hydraulic flow and mass
transport was developed. This approach enables the prediction of the removal
efficiencies within a few minutes, whereas a pure numerical approach would require
several hours to days due to numerical stability controls. The input parameters for the
model are defined by the geometry of the HFM and the operating conditions, no
empirical formulations are applied.
The model allows the investigation of the main factors controlling the removal
characteristics, e.g. the dependency on Henry’s law coefficient, gas side diffusional
Kcalc (m/s)
3.0e-5
2.0e-5
1.0e-5
0.0
0.0 1.0e-5 2.0e-5 3.0e-5
K exp (m/s)
C/C0 (-) m odel
0.001
0.01
0.1
1
1
0.1
0.01
C/C0 (-) experimental
Fig. 3: Left: Calculated overall mass transfer coefficients K vs. experimental K.
Calculations based on the resistance in series model. Right: Comparison of the
experimental removal efficiencies (C/C0, with C being the outflow aqueous concentration
and C0 being the inflow aqueous concentration) with the removal efficiencies calculated
by the proposed model.
resistance, and aqueous diffusion limitation, and also enables the efficient design of
further organic removal systems based on the HFM technology. The model was able to
predict removal efficiencies for all experimental conditions with reasonable accuracy
(Fig. 3 right).
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0.001