Details

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

,

where

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).