Investigation of Elemental Mercury Removal from Coal-Fired Boiler Flue Gas over MIL101-Cr

Abstract

In this work, the MIL101-Cr sorbent with a large BET surface area was prepared and used to remove Hg 0 from the simulated coal-fired boiler flue gas. The chemical and physical properties of the prepared sorbent were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). A range of experiments was conducted in a fixed-bed reactor to investigate the effects of reaction temperature, Hg 0 inlet concentration, gas hourly space velocity (GHSV) and flue gas composition on the Hg 0 removal for the prepared sorbent. The mechanisms and kinetics of the Hg 0 adsorption were also studied. The results showed that the MIL101-Cr sorbent achieved the Hg 0 removal efficiency of more than 85% for 4 h at 200 o C under the condition of a relatively high Hg 0 inlet concentration (203 μg/m 3 ) and GHSV (8  10 5 h -1 ). The O2 in the flue gas was found to be beneficial to Hg 0 removal. The NO in the flue gas favoured Hg 0 removal both in the presence and absence of O2. The SO2 in the flue gas notably inhibited Hg 0 adsorption in the absence of O2, whereas a low concentration of SO2 slightly inhibited Hg 0 removal in the presence of O2.However, high concentrations of SO2 in the flue gas still significantly weakend Hg 0 removal ability even in the presence of O2 due to the competitive adsorption of SO2 with Hg 0 on the sorbent and the sulfation of the sorbent. A simultaneous presence of O2 and NO in the flue gas could overcome the adverse impact of SO2 on Hg 0 adsorption. The H2O has little influence on Hg 0 removal due to the competitive adsorption. The XPS analysis indicated that the surface Cr 3+ , oxygen species and C=O group in MIL101-Cr acted as the active adsorption/oxidation sites for Hg 0 . The Hg 0 removal by MIL101-Cr belonged to chemisorption and could be described by the pseudo-second-order model. The equilibrium adsorption capacity calculated for the sorbent amounted to 25656 μg/g at 200 o C, which indicated that MIL101-Cr could be used as a promising sorbent to removeHg 0 from the coal-fired boiler flue gas.

Study on the Preparation of Magnetic Mn–Co–Fe Spinel and Its Mercury Removal Performance

“…It is easy to see that after adding 0.04% SO 2 on the basis of pure N 2 , the Hg 0 removal efficiency at the initial stage of adsorption had a slight increase, but after reaching the highest mercury removal efficiency, it dropped quickly, and the average mercury removal efficiency decreased compared to a pure N 2 atmosphere by 9%. The reason may be as shown in reactions (3)-( 5) (O* is the surface active oxygen of the adsorbent) [11,39]. SO 2 molecules are more likely to occupy surface active sites.…”

Graphitic Carbon Nitride for Gaseous Mercury Emission Control: A Review

“…34−37 Carbonaceous materials have also been widely studied owing to their ample sources and luxuriant pore structures, such as activated carbon, 38−40 petroleum coke, 41−43 and biochar. 44−47 In addition, some novel adsorbents emerged recently, i.e., metal−organic frameworks (MOFs) 48 and MXene (metal nitride or metal carbide). 49 However, their intrinsic Hg 0 affinities for pristine MOFs and MXene are very low.…”

“…As for noncarbon adsorbents, fly ash , and natural minerals − display low intrinsic Hg 0 affinity due to their low surface areas and pore volumes. Although some zeolites have large surface areas, they still exhibit low inherent Hg 0 affinity owing to inadequate active sites. − Metal oxides possess good Hg 0 oxidation ability; however, they are very sensitive to flue gas. − Carbonaceous materials have also been widely studied owing to their ample sources and luxuriant pore structures, such as activated carbon, − petroleum coke, − and biochar. − In addition, some novel adsorbents emerged recently, i.e., metal–organic frameworks (MOFs) and MXene (metal nitride or metal carbide) . However, their intrinsic Hg 0 affinities for pristine MOFs and MXene are very low.…”

Sulfur-Decorated Hyper-Cross-Linked Coal Tar: A Microporous Organic Polymer for Efficient and Expeditious Mercury Removal

“…A litany of investigations in this decade have been focused on designing materials with high mercury uptake capacity. − Recently, the metal-coordinating organic polymers bearing sulfur binding sites have assisted to overcome these problems. − Porous sorbents such as thiol-functionalized POPs, − covalent organic frameworks (COFs), − and metal–organic frameworks (MOFs) − have been reported for Hg­(II) removal. Although these materials demonstrated excellent activity for mercury adsorption, they are prohibitively expensive.…”