Thermodynamic study of SO2 reactive absorption into H2SO4/H2O2 aqueous solutions for Intensified Tail-Gas Scrubbing in Sulfuric Acid Plants

This study investigates the thermodynamics of SO2 absorption in aqueous H2SO4 solutions (30 and 60 % w/w) doped with H2O2 up to 1.8 g/L, aiming to enable a reactive oxidative scrubbing process for flue gas treatment. Absorption tests were carried out at 20 and 50 °C in a lab-scale fed-batch bubble column, over a range of SO2 concentrations from 100 to 3000 ppmv. The results show that H2O2 significantly increases SO2 solubility via fast gas-liquid reaction forming H2SO4. Despite the expected decrease in physical solubility with increasing temperature, oxidative absorption remains efficient due to reaction enhancement. Equilibrium data were used to validate a thermodynamic model in ASPEN PLUS® V.14, which accounts for gas-liquid and chemical equilibria using the Elec-NRTL method. The model provides the thermodynamic foundation required for the design of continuous oxidative scrubbers for tail-gas treatment in sulfuric acid plants. When coupled with appropriate mass-transfer and reaction-kinetic models, the developed equilibrium framework enables the estimation of column size, liquid and reagent consumption and overall process performance, supporting compliance with increasingly stringent EU SO2 emission standards while minimizing CAPEX and layout modifications, particularly in retrofit applications compared to alternative technologies.