Study on Reactivity of HgO over Activated Carbon with HCl and SO₂ in the Presence of Moisture by Temperature-Programmed Decomposition Desorption Mass Spectrometry

Abstract

Reactivities of mercury compounds over mercury sorbents with HCl and SO 2 are very important to the design of a solid sorbent for mercury vapor removal from coal-derived flue gases. However, presently available data on the reactivity of mercury oxide over mercury sorbent is insufficient. This study investigated the reactivity of mercury oxide with HCl and SO 2 using a temperature-programmed decomposition and desorption technique and a mass spectrometer (TPDD-mass) method. Mercury desorption from HgO over activated carbon (HgO/AC) was observed at the same temperature range as from HgO/ SiO 2 , but the mercury desorption peak from the HgO/AC was observed at a higher temperature than from the HgO/SiO 2 , indicating that some of the HgO was stabilized by the AC surface. When the HgO/AC was pretreated with HCl−H 2 O, the formation of HgCl 2 was suggested by the mass spectra of m/z = 272 and 270. The mercury desorption temperatures in the TPDD spectra were lower than those of nonpretreated samples. On the basis of the shape of the peak, it was conjectured that the mercury evolved from a single surface complex. The main mercury desorption peak was around 240°C when HgO/AC was pretreated with SO 2 −H 2 O and occurred at the lowest temperature of the three pretreatments. However, multiple peaks, indicating the formation of multicomplexes, were observed during the pretreatment. A mercury desorption peak (HgO) was observed at the intermediate position between the other two samples pretreated with SO 2 and HCl. The peak shape revealed that the mercury evolved from a single surface complex. It was also suggested that HCl suppressed the sulfuration of HgO by SO 2 during the pretreatment.

NH4Br-Modified Biomass Char for Mercury Removal in a Simulated Oxy-fuel Atmosphere: Mechanism Analysis by X-ray Photoelectron Spectroscopy

“…First, excessive SO 2 could consume oxygen adsorbed on the surface of RHCBr0.5, inhibiting the Hg 0 oxidation. 79,80 That also corresponds to our previous study. 81 Second, SO 2 could compete with Hg 0 on the adsorption active sites of RHCBr0.5, because their adsorption sites are similar.…”

Effects of Acidic Gases on Mercury Adsorption by Activated Carbon in Simulated Oxy-Fuel Combustion Flue Gas

“…Meanwhile, the content of HgO was apparently lower than that in the absence of SO 2 , which indicated the presence of SO 2 suppressed the generation of HgO. The possible reaction pathways are shown in eqs and . A small amount of gaseous SO 2 adsorbed on the AC surface into adsorbed states which then was oxidized to adsorbed SO 3 by oxygen atoms on the AC surface.…”

“…The possible reaction pathways are shown in eqs 3 and 4. 34 A small amount of gaseous SO 2 adsorbed on the AC surface into adsorbed states which then was oxidized to adsorbed SO 3 by oxygen atoms on the AC surface. This is in accord with the results of Saha et al 35 However, the bonding between SO 3 and the AC surface has been proven to be stronger than that between mercury and the AC surface, occupying pores and active sites of the AC surface, and then resulted in the mercury adsorption capacity decreasing with the increase of the S 6+ group of the AC surface.…”

Using the Novel Method of Nonthermal Plasma To Add Cl Active Sites on Activated Carbon for Removal of Mercury from Flue Gas

“…Wu et al have reported that HgCl 2 that formed on AC decomposed at around 300 °C. 42,43 This further proved that the mercury species on the Cl 2 nonthermal plasma-treated AC presented mainly as HgCl 2 . As C−Cl was identified as the main chlorine form on Cl 2 nonthermal plasma-treated AC, and HgCl 2 was the main mercury species after Hg 0 adsorption.…”

“…The untreated AC was mainly based on physical adsorption, while AC-C15T60 was chemically adsorbed, which usually required a quite strong energy at a higher desorption temperature. Wu et al have reported that HgCl 2 that formed on AC decomposed at around 300 °C. , This further proved that the mercury species on the Cl 2 nonthermal plasma-treated AC presented mainly as HgCl 2 .…”