Use of a numerical model to evaluate SO₂ absorption efficiency by sodium sulfite in packed and spray columns

Numerical modeling has been used extensively to simulate gas-liquid transfer of sulfur dioxide, assessing how operational parameters affect absorption efficiency in packed or spray columns. Despite individual studies on these contactors, comparative analyses on the same flue gas have been rare. This study uses a numerical model for both packed and spray columns to examine how parameters influence SO₂ absorption by sodium sulfite, describing packed and spray columns, is used to investigate the influence of operational parameters on SO₂ absorption by sodium sulfite. The model's predictions are validated against experimental data from an industrial pilot plant. Across varying conditions (L/G ratio, temperature, initial SO₂ content or initial S(IV) concentration), the packed column achieves higher absorption efficiencies compared to the spray column, with lower assumed energy costs due to a reduced L/G ratio. Temperature proves to be a significant factor, decreasing absorption efficiency by approximately 40% between 40 and 70 °C. SO₂ absorption efficiency declines with increasing concentrations of bisulfite and sulfite ions in the absorption solution, dropping to 50% at an S(IV) concentration of 2 kmol m^-3 in the liquid phase. Considering the objective of producing a concentrated bisulfite solution and a clean gas, a two-column system is recommended: one for bisulfite solution concentration at acidic pH and the other for gas purification enhancement at basic pH.