Regeneration Characteristics of Elemental Sulfur-Modified Activated Carbon for Mercury Removal

• Published in: Energy & fuels 2021-06, Vol.35 (11), p.9497-9508
• Main Authors: Chen, Cong, Duan, Yufeng, Huang, Tianfang, Zhu, Mingqing, Liu, Xiaoshuo, Wei, Hongqi
• Format: Article
• Language: English
• Subjects: Environmental and Carbon Dioxide Issues
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.1c00559

Although activated carbon doped with sulfur is considered to be effective for capturing elemental mercury from coal-fired flue gas, sorbent regeneration is more important for application in cycles. In this study, thermal elemental sulfur-loading methods were used both to modify activated carbon and to renew the used sorbent to remove mercury. The effects of sulfur-loading dosage, adsorbent inactivation, and regeneration on mercury removal performance were investigated, and the optimal conditions for preparing the regenerative adsorbent were determined. Various analytical techniques including Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the physicochemical properties of the samples for exploring the mechanisms of mercury adsorption. The results showed that adsorbents under optimal preparation conditions reached the most outstanding performance of the Hg0 breakthrough rate of lower than 8.58% at 150 °C. By comparing the samples before and after adsorption, changes on the sorbent surface of morphology and elemental composition were observed. The decrease in oxygen and sulfur contents of the deactivated adsorbent was the main reason for its deactivation. From the desorption curve of the saturated samples of the adsorbent, the optimal regeneration method of the adsorbent was determined. The cyclic mercury removal rates of the recovered adsorbents were 80.22, 81.75, 79.43, and 72.96% during regeneration cycles. The elemental sulfur-modified activated carbon with thermally renewable sulfur-loading exhibited not only an efficient mercury removal rate but also excellent regeneration characteristics.