Mass Balances in Absorption and Stripping Units
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This Demonstration shows the implementation of mass balance in a single-stage "stripping" or "absorption" unit. Use the sliders to select correct values for the two unknowns. The unknowns are shown in green in the graphic. Then check "solution" to see the correct answers. Click "new problem" for a new set of conditions with different unknowns and/or different values for the unknowns.
Contributed by: Rachael L. Baumann (September 2018)
Additional contributions by: John L. Falconer and Neil Hendren
(University of Colorado Boulder, Department of Chemical and Biological Engineering)
Open content licensed under CC BY-NC-SA
Assuming that the impurity concentration is low so that the liquid and vapor flow rates are constant, a mass balance on a single-stage absorption or a stripping unit is given by
is the mole ratio of the impurity flow rate in the liquid feed to the total liquid flow rate (ppm),
is the mole ratio of the impurity flow rate in the vapor feed to the vapor flow rate (ppm),
is the mole ratio of the impurity flow rate in the exiting liquid stream to the liquid flow rate (ppm),
is the mole ratio of the impurity flow rate in the exiting vapor stream to the vapor flow rate (ppm),
is the liquid flow rate (Mmol/h) and
is the vapor flow rate (Mmol/h).
The exiting streams are assumed to be in equilibrium, and since the impurity concentrations are low, Henry's law is used:
where is a constant , is Henry's constant (bar) and is pressure (bar).