Using polyethylene glycol to facilitate the absorption of NO₂ in sulfite solutions: Kinetics and mechanism

A new method was developed to scrub NO_x compounds in flue gases during the integrated technology of WFGD associated with ozone oxidation, among which polyethylene glycol (PEG) was utilized initially as an additive to facilitate the absorption of NO₂ by sulfite solution. Notably, absorption was significantly facilitated with adding PEG into absorbent. Compared to absorption by sulfite solution alone, NO₂ removal efficiency with PEG addition increased from 58.75% to 89.17%. Furthermore, the favorable role of PEG was considered to be ascribed to the its improvement on the rate-determining step among absorption process ── mass transfer of NO₂ into the liquid phase. A potential chemical transformation pathway between NO₂, SO₃^2- and PEG was proposed, and based on the hydrogen bonding between the various compounds. Additionally, a kinetic model was established based on various operating parameters that included adsorbent pH, ionic strength of S species, temperature, flow rate, and inlet SO₂ concentration. This model provides theoretical support for practical engineering.