Efficient Inhibition of S(IV) Oxidation in a Novel Basic Aluminum Sulfate Regenerative Flue Gas Desulfurization Process by Ethylene Glycol: Kinetics and Reaction Mechanism

Abstract

For the regenerative flue gas desulfurization method based on basic aluminum sulfate (BAS), efficiently inhibiting the oxidation of desulfurization by-products is extremely critical to reuse the absorbents and recover SO2. In this paper, the macrokinetics of S­(IV) antioxidation procedure was systematically investigated by varying inhibitors, aluminum content, pH, S­(IV) concentration, ethylene glycol (EG) concentration, temperature, oxygen partial pressure, and air flow in a bubbling reactor with magnetic stirring. EG was environmentally considered to be an ideal inhibitor by screening. Furthermore, the S­(IV) oxidization speed inhibited by EG was significantly accelerated when the aluminum content rose and was correlated to 10–0.6pH with a coefficient of 0.98. The general oxidization speed of S­(IV) was determined to be 1.1, −2.4, and 0.96 order in oxygen partial pressure, EG content, and total S­(IV) level, respectively. The apparent activity energy of S­(IV) oxidation process was obtained to be 52.0 kJ/mol. On the basis of a two-step model, kinetic analysis proved that the general S­(IV) oxidation rate in the BAS desulfurization liquid was decided by the intrinsic oxidation reaction. Meanwhile, the mechanism of S­(IV) oxidation reaction with EG was demonstrated and the products in reaction solution were detected by gas chromatography–mass spectrometry. The experimental findings will contribute to industrial design and procedure optimization related to the BAS regenerative desulfurization process.

Evaluation of FeIIEDTA‐NO reduction by thiourea dioxide in NO removal with FeIIEDTA

“…We find that the TD was oxidized to sulfite and urea along with Fe III EDTA reduction. 24 Therefore, involving reducing Fe II EDTA-NO by TD, SO 3 2− , and (NH 2 ) 2 CO is also considered as the main products of TD conversion. In order to prove this issue, the variations of sulfite and urea concentration were investigated.…”

“…1 It is generally considered that nitrogen oxide (NO x ) and sulfur dioxide (SO 2 ) are the priority pollutants from fuel gases. 3 It is difficult to remove NO (accounting for 95% in NO x ) with wet process because of poor solvability of NO in water. So far, SO 2 can be readily caught by wet process because of its higher solvability in solution.…”

“…So far, SO 2 can be readily caught by wet process because of its higher solvability in solution. 3 It is difficult to remove NO (accounting for 95% in NO x ) with wet process because of poor solvability of NO in water. For this reason, several approaches have been refined to improve NO absorption; one of which is selective catalytic reduction (SCR).…”

Simultaneous removal of NO and SO2 from flue gas by FeIIEDTA/sodium dithionite solutions

“…The large-scale utilization of fossil energy has led to a series of severe environmental problems including acidification, photochemical smog, eutrophication and ozone depletion. 1,2 Nitrogen oxide (NO x , of which NO accounts for 95%) and sulfur dioxide (SO 2 ) generally are considered to be the priority pollutants from fuel gases. 3 Therefore, the emissions of NO x and SO 2 have been rigorously controlled and regulated by environment protection departments around the world.…”

“…8 Fe II EDTA can rapidly catch NO to produce the ferrous-nitrosyl complex Fe II EDTA-NO [Eqn (1)], for which the equilibrium constant is generally 10 7 mol −1 . 9 However, a notable shortcoming of Fe II EDTA is that it can be readily oxidized by O 2 to produce inanimate Fe III EDTA [Eqn (2)], which limits its further popularization and application in industry. 10,11 Fe II…”