Experimental and modelling approach to the design of chemical absorption columns with fast gas-liquid reaction: A case-study on flue-gas desulfurization with H2O2 oxidative solutions
D. Flagiello, Francesco Di Natale, Amedeo Lancia, I. Sebastiani, F. Nava, A. Milicia, Alessandro Erto
Abstract
In this work, we propose a methodology to approach the design of chemical absorption columns with fast gas-liquid reactions by an experimental and modelling study, which accounts for thermodynamic (solubility) data, mass-transfer phenomena, and the reaction kinetics contribution. As a reference case, the SO 2 absorption in aqueous solution of H 2 O 2 at different concentrations, which oxidizes SO 2 to sulfuric acid, is considered. A lab-scale fed-batch bubble column is used to evaluate SO 2 solubility dataset in absorbing solutions of distilled water containing different dosages of H 2 O 2 . A thermodynamic model is developed and validated in a Thermodynamic Flash block of ASPEN PLUS®, allowing to describe the experimental results with optimum agreement. For kinetic experiments, a lab-scale falling-film absorber is used to investigate both SO 2 mass-transfer rates and the fundamental kinetic aspects of an absorption process with chemical reaction. The physical contribution to the mass-transfer rate is evaluated through a set of dedicated experiments, which allowed determining gas-side ( k G a ) and liquid-side ( k L a ) coefficients in the falling-film absorber. Subsequently, the Enhancement factor ( E L ) of the SO 2 oxidative absorption is evaluated for the oxidizing reaction (SO 2 + H 2 O 2 → H 2 SO 4 ) under the explored experimental conditions, using the equilibrium dataset and the mass transfer coefficients previously obtained. Finally, E L is correlated to the Hatta number ( Ha ) with the Danckwerts kinetic model as a pseudo-m th -n th -order non-reversible reaction type and the model kinetic parameters are calculated. • This work provides an experimental and modelling approach to the design of reactive absorption columns. • The thermodynamic model developed in ASPEN PLUS provides a proper estimation of the SO 2 -H 2 O 2 solubility dataset. • The kinetic experiments allowed assessment of the reaction kinetic parameters in the gas absorption of SO 2 into H 2 O 2 . • The kinetic model based on the Danckwerts equation provides a proper estimation of the Enhancement factors.