Investigation of Changes in Surface Chemistries on Virgin and Brominated Activated Carbon Sorbents during Mercury Capture: Before and After Regeneration

Abstract

Pre-halogenated activated carbon (AC) sorbents are known to be effective in Hg capture when injected into the flue gas stream generated from the combustion of low-chlorine-containing sub-bituminous and lignite coals. In this study, virgin (unfunctionalized) and brominated AC powders were tested for Hg sorption in a low-HCl (4 ppm)-containing simulated Powder River Basin (PRB)-fired flue gas matrix before and after regeneration. X-ray photoelectron spectroscopy (XPS) was used to investigate changes in sorbent surface chemistries, which were then correlated to Hg breakthrough data obtained from benchscale experiments. It was observed that Hg capture tests on brominated AC powders removed the surface-bound bromine, a known Hg-binding site, to levels below XPS detection limits. Further, XPS studies also revealed an increase in the chlorine content after adsorption on the tested samples and the samples regenerated at a lower temperature (204 °C). The decrease of bromine peaks coupled with the presence/increase of Cl, N, and S on the tested and some regenerated samples strongly indicates that the HCl, SO 2 , and NO x components in the flue gas play a collaborative role during Hg breakthrough. It is also observed from the breakthrough data that Hg adsorption on regenerated samples decreases significantly to 6.5−9.6% of the initial adsorption values. This indicates that regenerating AC sorbents for further Hg capture is not an effective process.

Regenerable Sorbent with a High Capacity for Elemental Mercury Removal and Recycling from the Simulated Flue Gas at a Low Temperature

“…To date, the main technologies for mercury emission control fall into two groups: powder activated carbon (PAC) injection and co-benefit of selective catalytic reduction (SCR) and wet flue gas desulfurization (W-FGD) system (Hg 0 was catalytically oxidized into Hg 2+ on the SCR catalyst and then scavenged by W-FGD). − However, the co-benefit of SCR and W-FGD will drive mercury from the gas phase to the liquid or solid phase, which may cause the secondary pollution. , PAC displays high efficiency for mercury removal, but the regenerating activated carbon (AC) sorbents for further Hg capture is not an effective process, which limits its wide application . Meanwhile, the commercial value of the fly ash is sacrificed by the PAC injection method .…”

Kinetic mechanism on elemental mercury adsorption by brominated petroleum coke in simulated flue gas

“…1 However, the cost of injecting activated carbon is high, and replaceable low-cost adsorbents, especially bromine and sulfur modied carbon based materials, have received more and more attention. [2][3][4][5][6] Petroleum coke, produced from the exploitation of oil or the extraction of traditional oil all over the world, is considered as an industrial waste due to the high content of organic sulfur.…”

Understanding the effect of thiophene sulfur on brominated petroleum coke for elemental mercury capture from flue gases

“…Modied low-cost carbon-based sorbents, including y ash and biomass ash, were developed with the bromine-impregnated and sulfur-impregnated ones showing the best effect to eliminate Hg from the coal combustion ue gas. [4][5][6][7][8][9][10][11][12][13] Elemental sulfur was reported as a promising "so" oxidant as a catalyst. 14 Petroleum coke is formed as the nal by-product of the petroleum industry during rening of crude bitumen or heavy oil.…”