The denitrification characteristics of Na₂S₂O₈ solution in a falling film reactor

ABSTRACT

Wet scrubbing technology is an effective emission control technology for marine diesel engines. Nitric oxide (NO) is one of the main component of ship emissions, the sodium persulfate (Na₂S₂O₈) can facilitate the NO mass transfer process to a rapid reaction. Falling film reactors are widely used in rapid gas–liquid reactions, however, the reaction characteristics of denitrification using Na₂S₂O₈ solution in a falling film reactor are not clear, which were investigated in this paper. The factors of NO mass transfer flux were tested with the liquid–gas ratio of 15 L/m³. The effects of solution properties and temperatures on the reaction driving force were studied by calculating the chemical reaction equilibrium constants and Gibbs free energy changes. The results showed that the NO mass transfer flux increased with the increase of temperature, Na₂S₂O₈ concentration, O₂ concentration and NO concentration. NO mass transfer flux increased by 41.00% and then decreased by 2.12% as the pH value increased from 7 to 10 and then rising to 12. The Gibbs free energy changes of alkaline solutions were 114.22%−130.99% lower than those of acidic solution at 303–343 K, and the chemical reaction equilibrium constants were higher. Na₂S₂O₈/seawater system has great application potential in marine exhaust gas purification.

GRAPHICAL ABSTRACT

KEYWORDS:

• Falling film reactor
• mass transfer flux
• wet denitrification
• sodium persulfate
• gibbs free energy changes

Disclosure statement

No potential conflict of interest was reported by the author(s).

CRediT authorship contribution statement

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Jing Liu, Jingxuan Jiang, Xiangwen Xing, Hao Zhang, Juan Chen and Yong Dong. The first draft of the manuscript was written by Jing Liu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (No. U1906232) and the Shandong Province Key R&D Program of China (2022CXPT034).