Calculation of the Multiphase Equilibrium of the Reaction in Wet Flue Gas Desulfuration

A computational code, which can be used to calculate gas-liquid-solid 3-phase equilibrium line, has been developed based on the principle of free energy minimum. Then the equilibrium lines of dissolution of SO₂ and CaCO₃ in water are obtained using the code. The results satisfy the mass and charge conservation and match well with the data in the references. Finally, multiphase equilibrium lines of the reaction in WFGD are calculated in different conditions. The results show that temperature, concentration of SO₂, CO₂, have different effects on the solubility of SO₂ under initial conditions given in the paper. Temperature and concentration of SO₂ have great effects, and the concentration of CO₂ has a small effect. The solubility of SO₂ increases as the partial pressure of SO₂ increases, temperature decreases or the concentration of CO₂ decreases. These conclusions have a great guidance on designing the tower of wet flue gas desulphurization.