Surface modification of fly ash by non-thermal air plasma for elemental mercury removal from coal-fired flue gas

ABSTRACT

The fly ash from a coal-fired power plants was modified with non-thermal plasma in air to improve the elemental mercury (Hg⁰) removal performance. The Hg⁰ adsorption experiments were implemented via a bench-scale fixed-bed reactor system. Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), ultimate, X-ray diffraction (XRD) and XRF analysis were employed to characterize the fly ash. The effect of non-thermal plasma voltage and time on Hg⁰ removal efficiency was investigated. The results showed that fly ash had better Hg⁰ removal performance when treatment voltage was 3.0 kV and treatment time was 7 min. Furthermore, the results showed that non-thermal plasma treatment had little influence on the specific surface area. However, non-thermal plasma treatment increased the relative content of oxygen. XPS and temperature programmed desorption results indicated that Hg⁰ removal process included adsorption and oxidation of Hg⁰. Moreover, ester and carbonyl groups played extremely vital roles in the improvement of Hg⁰ removal performance, and their temperature programmed desorption peak occurred at around 250°C and 320°C, respectively.

GRAPHICAL ABSTRACT

KEYWORDS:

• Non-thermal plasma
• fly ash
• Hg⁰ removal efficiency
• ester and carbonyl groups
• temperature programmed desorption

Acknowledgement

The authors gratefully acknowledge the assistance of the Analytical and Testing Center of Huazhong University of Science and Technology for the experimental measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial support provided by the National Key Research and Development Program of China [grant number 2016YFB0600603] and the National Natural Science Foundation of China [grant numbers 51776084 and 51476066].