In the existing wet flue gas desulfurization processes which have problems of low SO₂ removal efficiency, formation of scale and low limestone utilization, the adding additives to the reactants help enhance SO₂ removal. This is quite attractive since no process changes or large capital expenditure are needed. The organic acid additives enhance the rate of mass transfer. In this work, the properties of additives were studied to improve the reliability and to increase SO₂ removal efficiency. SO₂ absorption into organic solutions were modeled by approximate surface removal theory and equilibrium reaction equations and a solution algorithm for numerical solution was developed. Also the criteria of selection of additives were suggested. The mass transfer enhancement by mixed organic acid, which was a byproduct of a company, was tested theoretically as an inexpensive alternative additive.