Absorption of nitrogen oxides in aqueous solutions in a structured packing pilot column

This study deals with the absorption of dilute nitrogen oxides (NOx) into aqueous solutions of hydrogen peroxide (0.05 M) and of sodium hydroxide (2 M), at the atmospheric pressure. A pilot column filled with structured the metallic packing Optiflow™ was employed. The feed gas was air containing NOx at concentrations between 121 and 1336 Pa and the oxidation degrees were 0.5 and 1. NOx absorption efficiencies ranging 12–63% were obtained. The models used were based on equilibrium and considered the chemical reactions and the mass transfers in the gas and liquid phases. The results of the mathematical simulations using the models presented removal efficiencies fairly agreed with experimental data. The NOx absorption is primarily affected by the oxidation degree, which determines the HNO2 formation in gas phase. The role of HNO2 is very important: in the presence of hydrogen peroxide the HNO2 absorption is ruled by the reaction in the liquid phase and in the presence of sodium hydroxide is ruled by diffusion and reaction in gas phase.