A gas−liquid equilibrium-operational diagram showing the relationships between the concentration of total SO2, combined SO2, and true free SO2, iso-pH, and isopartial pressure of SO2 is
presented as a useful tool for graphically presenting the absorption of SO2 in the NaOH−SO2−H2O system. The graphical presentation of the absorption of SO2 on an industrial scale is studied
on a laboratory scale using a falling film reactor by taking into account scaled-down criteria for
the spray culumns of liquid−gas contactors. An example is given where the bulk and the
interfacial compositions along the contactor during the absorption of SO2 into 0.005 M NaOH
at T = 298 K are simulated using an absorption model based on the film theory of gas absorption.
This is then graphically presented in a design diagram with the concentration of Na+ as a
parameter, which is reconstructed from the gas−liquid operational diagram for the NaOH−SO2−H2O system. The enhancement factor, the overall mass-transfer coefficient, the resistance
to the absorption of SO2 in the liquid and in the gas phase, and the fraction of the liquid resistance
along the falling film reactor are also calculated.