Study of Mercury-Removal Performance of Mechanical–Chemical-Brominated Coal-Fired Fly Ash

Abstract

The mechanical–chemical-modified fly ash (FA-MC) and mechanical–chemical-brominated fly ash (FA-MC-Br) were prepared by omnidirectional planetary ball mill, and impregnated–brominated fly ash (FA-I-Br) was also prepared using the same mass ratio of fly ash/NH4Br as a comparison. The mercury-removal efficiency of raw fly ash (FA), FA-MC, FA-MC-Br, and FA-I-Br was evaluated in a fixed-bed reactor. The physical and chemical properties of the four samples were investigated by the Brunauer–Emmet–Teller, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and mercury temperature-programmed desorption analysis. The results showed that the mercury-removal efficiency of the four samples followed the order of FA-MC-Br > FA-I-Br > FA-MC > FA, the value of which was 67, 30.98, 26.12, and 17.96%, respectively. The mercury-removal performance of the four samples was mainly reflected in the oxidation (>90%), while the adsorption only accounted for a small proportion (<10%). The mechanical–chemical activation improved the content of the surface-adsorbed oxygen and amorphous phase of FA, which promoted the oxidation efficiency of the samples. Due to the generation of Br-containing complexes and further increase in the content of surface-adsorbed oxygen on FA-MC-Br, the mechanical–chemical activation coupled with the addition of NH4Br significantly improved the mercury-oxidation and -adsorption efficiency. The mercury-adsorbed species of fresh FA-MC-Br is HgBr2, and that of used FA-MC-Br is HgBr2 and HgO. The reaction between elemental mercury and FA-MC-Br was followed Eley–Rideal reaction. As a comparison, the mercury-removal efficiency of FA-I-Br was far less than that of FA-MC-Br, demonstrating that FA-MC-Br was a cost-effective alternative material to activated carbon for potential industrial applications.

Experimental Study on the Mercury Removal of a H2S-Modified Fe2O3 Adsorbent

“…To date, activated carbon injection (ACI) is considered to be the most commercialized technology for controlling mercury emission from coal-fired flue gas. , However, its high operational cost and low utilization rate limit its wide application. , To improve it, attention has been focused on chemical modification besides the carbon-based adsorbent, in which sulfur modification, such as SO 2 , elemental sulfur, plasma-carrying sulfur, etc., reveals a promising way to improve Hg 0 removal ability. Metal oxides have many advantages over activated carbon, such as wide reaction temperature, potential regeneration, and low cost .…”

Effect of a Mechanochemical Process on the Stability of Mercury in Simulated Fly Ash. Part 1. Ball Milling

“…Our previous research showed that MC bromine-modified fly ash is an economic and efficient adsorbent for mercury removal . The main forms of mercury after adsorption saturation are HgBr 2 and HgO, which are easy to leach in the process of secondary utilization and lead to secondary release.…”

“…Because the composition of fly ash is extremely complex, eliminating the influence of various components of fly ash is beneficial for obtaining the mercury MC stabilization mechanism. Furthermore, SiO 2 is the main component of MC bromine-modified fly ash developed in previous studies, which accounts for 47.72%. , To this end, HgBr 2 was loaded into SiO 2 by the impregnation method to prepare simulated adsorption saturated MC bromine-modified fly ash (SFA). The method for preparing SFA was carried out according to the following steps: (1) due to the good solubility of mercuric bromide in ethanol, 0.5 g of mercuric bromide (99.5% purity; Sinopharm Chemical Reagent Co. Ltd.) was added to 10 mL of ethanol (95% purity) and dissolved to prepare solution#1; (2) 1 mL of solution#1 was added to 79 mL of ethanol and diluted to prepare solution#2; (3) 10 g of silicon dioxide (99% purity; Sinopharm Chemical Reagent Co. Ltd.) was added into solution#2 and then stirred for 6 h by a magnetic stirrer at room temperature; (4) the impregnated sample was put in the oven and dried at low temperature (60 °C) until the weight difference between the two measurements was less than 1%, and thus, SFA was finally obtained.…”

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

“…The abundant O ad would facilitate Hg 0 oxidation to generate HgO as the active species. The related reaction process was described by eqn (4)- (6). As the efficiencies of the raw catalyst and pure CeO 2 were no more than 38.3%, the superior performance of the CeO 2 modied commercial SCR catalyst was also primarily resulted from the synergy of V 2 O 5 and CeO 2 in the catalyst.…”

“…Hg 2+ and Hg p can be respectively captured by wet ue gas desulfurization (WFGD) and particulate matter control device (PMCD) of power plant because of their physical properties, while Hg 0 is difficult to be controlled by the single pollutant control equipment due to its volatility and water insolubility. 5,6 So the key to the control of mercury emission from coal combustion power plant is the removal of Hg 0 . Similarly with mercury, NO x is also a sort of hazardous contaminant with great harm to environment that coal burning releases, and NO occupies about 95% among NO x .…”