Absorption of SO2 in the MgO–SO2–H2O and in the Ca2+–SO2–H2O System

T. Recelj and J. Golob

Abstract
The engineering analysis of SO2 absorption is presented in two different aqueous systems, corresponding to two industrial processes; in the MgO–SO2–H2O system (SO2 absorption in the magnesium based pulp production) and in the Ca2+–SO2–H2O system (limestone spray scrubbing process for absorbing SO2 from the power plants). A thermodynamic model used for constructing the equilibrium diagram for the both systems was developed. The diagrams present the relationship between the concentration of total SO2, the concentration of combined SO2, the concentration of true free SO2 and the pH value. The overall processes in both systems were divided into three partial processes and their mass balances were graphically presented in the corresponding equilibrium diagram. Equilibrium diagrams were proven to be useful tools for quantitative analysis (including equilibrium, mass balances, process kinetics) of SO2 absorption in Mg2+ and Ca2+ based solutions. Results of the analysis of the both industrial cases are added.

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Keywords
Absorption of SO2, equilibrium diagram, Pitzer ion-interaction model, mass transfer analysis