Determination of the gas-liquid reaction kinetic for sulfur dioxide absorption in sodium chlorite aqueous solutions

Abstract

This study is part of the research activities devoted to the development of new gas-cleaning technologies required to minimize the emissions factors of sulfur compounds in chemical industries and power plants. Among flue gas desulfurization (FGD) processes, wet scrubbing with oxidizing chemicals, e.g. sodium chlorite (NaClO₂) has appeared as a viable option for different applications. The present work aims to study the absorption kinetics of the gas-liquid reaction between sulfur dioxide (SO₂) and NaClO₂, in a lab-scale falling-film absorber, investigating the effects of the main process parameters: liquid and gas flow rates, SO₂ gas-phase concentration, NaClO₂ liquid-phase concentration, solution pH and process temperature. The experimental activity aims to determine the Enhancement Factor (E_L) to develop a kinetic model for reactive absorption. To this end, kinetic parameters are calculated from experiments using the Danckwerts equation for a pseudo-second-order reaction kinetic, determining a maximum prediction error of ±20 % compared to the experimental data. Experimental data available in the literature on pilot-scale oxidative FGD scrubbers using chlorite are used to test the validity and robustness of the kinetic model. The kinetic model is able to predict the data with good accuracy within a prediction error range of ±30 %.