Research on the Mechanism of Elemental Mercury Removal over Mn-Based SCR Catalysts by a Developed Hg-TPD Method

Abstract

Using SCR catalyst to oxidize and remove elemental mercury (Hg 0) synergistically is a promising method for mercury emission control in coal combustion power plants and is currently attracting widespread interest. In this study, a developed mercury thermal desorption (Hg-TPD) approach, combined with other associated methods, was employed for identification of the mercury species in the Mn-based SCR catalysts that have been used for synergistic Hg 0 removal. The analysis results demonstrated the Hg 0 adsorption on the catalysts was a necessary process for the Hg 0 removal, though the SCR catalysts removed Hg 0 mainly through catalytic oxidation and the amount of the adsorbed mercury contributed only a little to the Hg 0 removal efficiency. And the essential adsorption process was mainly in the way of chemisorption. HgO was the prime species that was identified to form in the catalysts, and a little amount of adsorbed HgCl2, Hg(NO3)2 and Hg-OM was detected as well in the samples spent in the simulated coal-fired flue gases. O2, HCl, NO and high concentration of CO2 in the flue gas all promoted the adsorption capacity and the generation of related Hg compounds so that they were conductive to Hg 0 removal efficiency, while similar phenomenon was not emerged in the presence of SO2, NH3 and H2O and meanwhile the amount of adsorbed HgO was decreased so that the efficiency was inhibited. The mobility testing by sequential extraction procedure indicated most of the retained Hg belonged to the mobile fraction, which was in accordance with the identification results of the Hg-TPD analysis. The consequences of this research would create a better understanding of the Hg 0 removal mechanism over the Mn-based SCR catalysts and provide additional information on the disposal of the retired catalysts in the environment.

Removal of Elemental Mercury from Flue Gas Using Cobalt-Containing Biomaterial Carbon Prepared from Contaminated Iris sibirica Biomass

“…The content of the three components is relatively low compared with the abovementioned O 2 , SO 2 , and NO, but it might also have certain impacts on the removal of Hg 0 . Many researchers considered that SO 3 , NO 2 , and HCl could enhance the Hg 0 removal, − and this will be examined in future work.…”

Enhancement of CeO2modified commercial SCR catalyst for synergistic mercury removal from coal combustion flue gas

“…So the catalyst showed remarkable activity for simultaneous NO and Hg 0 removal. The prominent performance for synergistic Hg 0 removal was mainly owed to the sufficient chemisorbed oxygen (O ad ) of 4% CeO 2 -SCR led by the existence of Ce 3+ /Ce 4+ ion pair and the oxygen transfer between them in the catalyst, 38,49 which would be conrmed by the subsequent XPS analysis. The abundant O ad would facilitate Hg 0 oxidation to generate HgO as the active species.…”

A new analytical method based on Co-Mo nanoparticles supported by carbon nanotubes for removal of mercury vapor from the air by the amalgamation of solid-phase air removal

“…In these methods, sample preparation depends on the applied nitric acid and hydrochloric acid which can be hazardous to the environment and human health [9,10]. Emissions from different sources, mercury release in different forms, including elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ), and particulate bond mercury (Hg p ) [11,12]. Among of various states of mercury, Hg 0 is difficult to remove due to its stability, long persistence time, high volatility and insolubility in water [13,14].…”