Hg0 Removal Performance Research Articles

Enhancement of CeO2 modified commercial SCR catalyst for synergistic mercury removal from coal combustion flue gas.

CeO2 modified commercial SCR (selective catalytic reduction) catalysts with different CeO2 content were prepared and researched for synergistic mercury removal from coal combustion flue gas in this study. The characterization analyses on the catalysts indicated that the introduction of CeO2 increased the surface area, the dispersity of the metal oxides on the TiO2 support and the redox behavior of the catalyst, which was beneficial to the catalytic activity. The experimental results confirmed that the CeO2 loading improved the catalytic efficiencies over the commercial SCR catalyst. The catalyst with a CeO2 content of 4% displayed the optimal performance for NO and synergistic Hg0 removal, of which the NO conversion and Hg0 removal efficiency reached 90.5% and 78.2%, respectively, at 300 °C in simulated coal-fired flue gas. The Hg0 removal activity, the independence of Hg0 removal from HCl concentration and the effects of SO2, NO and NH3 on Hg0 removal efficiency all became positive over the modified catalyst compared to over the raw one, which was mainly due to the sufficient chemisorbed oxygen derived from the synergy of V2O5 and CeO2 and the redox transformation between Ce3+ and Ce4+ on the catalyst surface. The CeO2 modification generated a significant enhancement on the catalytic performance and made the commercial SCR catalyst more suitable to be employed for NO and synergistic mercury removal in a coal combustion power plant.

Photocatalytic oxidation removal of elemental mercury from flue gas. A review

Air pollution caused by mercury emissions from combustion and pyrolysis of fossil fuels, biomass, and solid wastes is a major health issue. Elemental mercury (Hg0), the dominant species in flue gas, is poorly captured by actual control equipments because Hg0 has a high volatility and is insoluble in water. Alternatively, photocatalytic processes can oxidize Hg0 into Hg compounds that are easier to remove. Here we review the recent research on oxidative removal of Hg0 by photocatalysts, with focus on titanium dioxide, bismuthides, silver compounds and hybrid photocatalysts. We discuss the Hg0 removal performances and mechanisms of catalytic oxidation. The TiO2 photocatalyst often suffers from low absorption of solar energy and easy recombination of photoinduced electron–hole couples. BiOIO3 appears as a promising photocatalyst due to its high Hg0 oxidation activity under visible light irradiation. Silver carbonates and silver halides are newly developed visible-light-responsive photocatalysts for Hg0 removal. Fast separation and transformation of photogenerated electrons and holes control the performance of Hg0 removal by photocatalysts.

Efficient Removal of Elemental Mercury from Coal-Fired Flue Gas over Sulfur-Containing Sorbent at Low Temperatures.

In the work, sulfur-containing sorbents were employed to remove elemental mercury (Hg0) from coal-fired flue gas. The work used the thermogravimetric analysis, Brunauer–Emmett–Teller method, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy to characterize the physicochemical properties of the sorbents. The Hg0 removal performance of these used sorbents from the simulated coal-fired flue gas was evaluated by a bench-scale fixed-bed reactor. The results indicated that a generous amount of elemental sulfur covered the surface and pore structure of the used sorbent. With the rise of H2S selective oxidation temperature, both the sulfur content and specific surface area decreased rapidly. Used-Fe/SC120 could achieve the mercury removal efficiency of above 90% at 90 °C. The high temperature was not conducive to the mercury capture due to the release of surface elemental sulfur. The presence of O2 and SO2 inhibited Hg0 removal in different degrees because of the decreased active sulfur sites and competitive adsorption. Meanwhile, NO promoted the Hg0 removal efficiency by enhancing the Hg0 oxidation. The further analysis showed that the surface elemental sulfur was vital to capture the Hg0 from coal-fired flue gas, which reacted with Hg0 to form HgS.

SO2 promoted ultrafine nano-sulfur dispersion for efficient and stable removal of gaseous elemental mercury

Development of a low-cost, stable and high-efficiency method is a vital challenge for elemental mercury (Hg0) decontamination from nonferrous smelting flue gas. The ultrafine size (<10 nm) and homodisperse nanometer sulfur (Nano-sulfur) was synthesized from alkali desulfurization solution by using a facile method. The as-synthesized Nano-sulfur exhibited excellent Hg0 removal performance over the bulk sulfur and commercial sublimed sulfur. Sulfur dioxide was surprisingly proved as a promoter for Nano-sulfur to enhance the Hg0 removal in this study. Nano-sulfur dispersion showed higher than 92% removal efficiency for 119 h under high-concentration SO2 atmosphere. The Hg0 adsorption capacity and rate of Nano-sulfur reached 242.1 mg/g and 24.6 μg/(g·min) respectively, which were both higher than other traditional adsorbents like sulfur-containing activated carbon and metal sulfides. Snew was proved as the main active substance to remove Hg0, which could be continuously generated from Nano-sulfur by the reversible reaction under effect of SO2. The gaseous Hg0 was largely transformed to colloidal phase (87.47%) and precipitated phase (10.53%) in the HgS form after wet scrubbing. This work offers a new path towards the design of nonferrous smelting flue gas Hg0 purification method by adding Nano-sulfur dispersion into the wet scrubber of existing air pollution control devices, i.e., flue gas scrubber and wet flue gas desulfurization.

Insights into Efficient Removal of Gaseous Hg0 using AgIO3-Modified BiOI/CoFe2O4 Composites through Photocatalytic Oxidation

A series of AgIO3 modified BiOI/CoFe2O4 heterojunction photocatalysts synthesized by a solvothermal and subsequent deposition–precipitation method were utilized to remove gaseous Hg0 from simulated flue gas under fluorescent light irradiation. The effects of AgIO3 content, photocatalyst dosage, solution temperature, fluorescent lamp irradiation, pH value, inorganic anions, and SO2 and NO on Hg0 removal performances were investigated in detail. Moreover, the ternary AgIO3–BiOI/CoFe2O4 composites were characterized by XRD, magnetic hysteresis, N2 adsorption–desorption, SEM, TEM, XPS, DRS, ESR, and photocurrent analyses. The results indicated that the AgIO3–BiOI/CoFe2O4 materials possessed enhanced visible-light-driven photocatalytic activities for Hg0 removal, which were much higher than those for AgIO3 and BiOI, and the Hg0 removal efficiency by optimum AgIO3(7%)/BC can reach as high as 99%. The AgIO3 content, solution temperature, FSL irradiation, and SO2 all exhibited significant effects on Hg0 removal. ...

Mercury removal from flue gas by magnetic iron-copper oxide modified porous char derived from biomass materials

In this work, a magnetic iron-copper oxide modified porous char derived from biomass materials was prepared by microwave activation and ultrasonic-assisted impregnation method to remove Hg0 from flue gas. The effects of operating parameters and flue gas components on Hg0 removal performance as well as physicochemical properties of samples were studied. The reaction mechanism and the regeneration performance of samples were also investigated. The experimental results display that the biomass-based porous char derived from microwave and steam activation exhibits a larger pore volume, higher surface area and well-developed pore structure. The ultrasonic treatment promotes the dispersion of active components on the surface of samples. The CuFe0.3/WSWU10(500) sample exhibits good Hg0 removal performance, and about 90.58% of Hg0 is captured from flue gas at 130 °C. Increasing SO2 concentration inhibits Hg0 removal. The presence of O2 and NO promotes the removal of Hg0. Low concentration of water vapor (>4%) improves Hg0 removal performance, while excessive water vapor plays an opposite role. The presence of copper/iron active components, chemisorbed oxygen and lattice oxygen over the surface of adsorbent is conducive to the removal of Hg0. The modified sample exhibits a good regeneration performance.

Turning fulvic acid into silver loaded carbon nanosheet as a regenerable sorbent for complete Hg0 removal in H2S containing natural gas

The migration and agglomeration of Ag nanoparticles during high temperature regeneration processes were generally considered the key contributor for the decreasing of Hg0 removal performance over Ag-based sorbents. In this work, a complexation pathway was developed for controllable synthesis of Ag loaded carbon nanosheet (Ag/Fvs) using fulvic acid as template and carbon source. The elemental Ag nanoparticles were highly dispersed and embedded in the carbon nanosheet with an average diameter of 7.12 nm and formed a special core-shell structure. The synthesized sorbent achieved a complete Hg0 removal in H2S containing natural gas at ambient temperature. At 1% breakthrough, the Hg0 capture capacity of Ag/Fvs was as high as 1.36 mg·g−1, which is much higher than the sample prepared by traditional impregnation method (I-Ag/Fvs, 0.98 mg·g−1) and other existing commercial sorbents. More importantly, the spent Ag/Fvs could be easily regenerated by thermal treating process, its Hg0 capture capacity only slightly decreased by 5.8% after 4 cycles. We considered the carbon layer prevented Ag nanoparticles from poisoning by H2S, and more active sulfur sites for Hg0 capture could be formed on porous carbon nanosheets by chemical adsorption of H2S, which is beneficial for the strong tolerance to H2S. The excellent regeneration performance of Ag/Fvs mainly attributed to the nanoconfinement of carbon layer, which is conducive to prevent the agglomeration of Ag nanoparticles during high temperature regeneration processes. This work represented a practical and efficient pathway to utilize the cheap fulvic acid for applications of Hg0 removal in H2S containing natural gas.

Surface modification of fly ash by non-thermal air plasma for elemental mercury removal from coal-fired flue gas

ABSTRACT The fly ash from a coal-fired power plants was modified with non-thermal plasma in air to improve the elemental mercury (Hg0) removal performance. The Hg0 adsorption experiments were implemented via a bench-scale fixed-bed reactor system. Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), ultimate, X-ray diffraction (XRD) and XRF analysis were employed to characterize the fly ash. The effect of non-thermal plasma voltage and time on Hg0 removal efficiency was investigated. The results showed that fly ash had better Hg0 removal performance when treatment voltage was 3.0 kV and treatment time was 7 min. Furthermore, the results showed that non-thermal plasma treatment had little influence on the specific surface area. However, non-thermal plasma treatment increased the relative content of oxygen. XPS and temperature programmed desorption results indicated that Hg0 removal process included adsorption and oxidation of Hg0. Moreover, ester and carbonyl groups played extremely vital roles in the improvement of Hg0 removal performance, and their temperature programmed desorption peak occurred at around 250°C and 320°C, respectively.

Immobilization of elemental mercury in non-ferrous metal smelting gas using ZnSe1−xSx nanoparticles

Gaseous elemental mercury (Hg0) in non-ferrous smelting gas is generally accompanied by a high concentration of SO2. Traditional sorbents for Hg0 removal often suffer from SO2 poisoning. To develop a sorbent that has high mercury removal efficiency and excellent sulfur resistance, Zn-Se-S composites were selected. The experimental results indicated that the ZnSe0.7S0.3 composite had the best Hg0 removal performance, achieving an Hg0 removal efficiency higher than 99% after 120 min of reaction at 150 °C. A “hump” was observed in the adsorption breakthrough curve. This phenomenon is due to the activation of surface Se0, with reduction in surface oxidation state (from Se2+ to Se0) by Hg0 or SO2. This composite has multiple adsorption sites (Se0 and active S) for mercury uptake from smelting gas. Moreover, this specific Zn-Se-S composite had excellent SO2 resistance. Even high concentrations (1000 or 2000 ppm) of SO2 barely influenced Hg0 removal performances. The Zn-Se-S composite exhibited potential for Hg0 removal from non-ferrous smelting gas.

Using H2S plasma to modify activated carbon for elemental mercury removal

Non-thermal plasma was applied to modify activated carbons (ACs) in the presence of H2S for improving the elemental mercury (Hg0) removal performance. The physical and chemical properties of raw and modified ACs were characterized by scanning electron microscopy with energy disperse X-ray spectroscopy, Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy. The Hg0 removal performance of modified AC was tested by a bench-scale fixed bed. The results indicated that H2S plasma treatment enhanced S content of raw AC. Moreover, S content and Hg0 removal efficiency of modified AC increased with the increase of H2S concentration. The reason was that higher concentration H2S resulted in more S active sites on modified AC and S active site played a significant role during the Hg0 removal process. Besides, non-thermal plasma treatment in the presence of H2S had a weak impact on BET surface area. By further analysis, it could be inferred that the improvement of Hg0 removal performance was ascribed to the chemisorption rather than physisorption. Combined the results of temperature programmed desorption and XPS analysis, the mechanism of Hg0 removal was that elemental S on the surface of modified AC reacted with Hg0 to form HgS.

Removal of elemental mercury from simulated flue gas by ZSM-5 modified with Mn-Fe mixed oxides

Zeolite (ZSM-5), as a kind of carbon-free sorbent or catalyst, has been widely applied in many fields due to its big surface area, good chemical and thermal stability, and excellent adsorption performance. In this study, Mn-Fe modified ZSM-5 are synthesized via sol-gel approach and employed for elemental mercury (Hg0) removal from simulated flue gas at low temperature. The results show that pure ZSM-5 shows poor mercury capture ability with Hg0 removal efficiency of ~8.5–18.8% at 100–300 °C. Mn or Fe modification can both efficiently enhance the Hg0 removal efficiency of the ZSM-5. The sorbent with Mn/Fe molar ratio of 1:2 exhibits the optimal mercury capture ability with the highest Hg0 removal efficiency near 100% at temperatures of 200 and 250 °C due to the significant synergy effect between Mn2O3 and Fe2O3. The presence of NO has a negligible effect on the Hg0 removal performance of Mn/ZSM-5 and Mn1Fe2/ZSM-5, while the existence of SO2 considerably degrades the Hg0 capture performance of Mn/ZSM-5 owing to competing adsorption and side reactions. Fe addition can protect Mn active sites from SO2 poisoning and thereby enhancing the SO2 resistance of Mn/ZSM-5 to some extent.

MoO3-adjusted δ-MnO2 nanosheet for catalytic oxidation of Hg0 to Hg2+

The challenge of Hg0 emission control has necessitated the development of catalytic oxidation technology. Herein, a combination of experimental and computational approach to explore the potential over Mo-Mn catalysts was conducted. Series of catalysts were synthesized and characterized with varying Mn and Mo loading (1–10%). Among the various compositions, 1.25Mo2 Mn catalyst exhibited the best Hg0 removal performance with Hg0 removal efficiency > 98% (oxidation ratio > 50%, and better stability over 10 h period at 250 °C). Most importantly, the synergistic interaction between MoO3 and defective δ-MnO2 nanosheet was promoted by the adjusted activation energy, bond strength, Brønsted acidic sites and defects, which facilitated the catalytic oxidation of Hg0 to Hg2+. Furthermore, DFT calculations suggested that the role of Mo enabled the reduction in the energy barrier for the desorption step, which was defined as the rate-determining step for catalytic oxidation of Hg0 on Mn-based catalyst.

Development of reusable mercury sorbents for an oxy-fuel IGCC power generation system

Gaseous elemental mercury (Hg0) removal tests, using copper-based sorbents (CBS) developed in-house, were performed in a laboratory scale fixed-bed reactor. The aim was to find potential candidate sorbents to use in a dry syngas purification process plant. The dry purification process is under development for oxy-fuel integrated gasification combined cycle (IGCC) power generation with an efficient carbon dioxide separation function. The performance of CBS was evaluated as a function of two major characteristics. First, Hg0 removal performance of the CBS is improved by pre-sulfidation. Second, Hg0 removal performance of the spent CBS is recovered through moderate heating under diluted O2 conditions. A honeycomb type sorbent was prepared by impregnating raw material of the CBS onto the honeycomb-shaped support. Since copper sulfide will effectively capture Hg0 in a reducing gas atmosphere, the CBS honeycomb was initially pre-sulfurized by H2S diluted with N2 at 120 °C in a fixed-bed reactor until complete breakthrough of H2S. The simulated syngas from the oxy-fuel IGCC was fed into the reactor with conditions set at 140 °C and 0.98 MPa, where the Hg0 in the syngas was reduced to below 1.0 µg/m3N by the CBS honeycomb. The spent CBS honeycomb was regenerated by introducing 1 vol-% of O2 diluted with N2 at 280 °C. The sequential operation of pre-sulfidation, mercury removal, and regeneration steps was performed cyclically three times, during which the CBS honeycomb maintained a satisfying Hg0 removal performance. These results revealed that the A-CBS honeycomb is a potential candidate for the dry mercury removal process in the Oxy-fuel IGCC power generation plant.

Efficient removal of Hg0 from simulated flue gas by novel magnetic Ag2WO4/BiOI/CoFe2O4 photocatalysts

A series of novel ternary Ag2WO4/BiOI/CoFe2O4 hybrids synthesized by a facile modified deposition-precipitation method were utilized to explore their activities for toxic elemental mercury (Hg0) removal under fluorescent light (FSL) irradiation. The as-prepared materials were characterized by various methods and the experimental parameters such as Ag2WO4 content, fluorescent light irradiation, and inorganic anions were investigated in detail. The characterizations revealed that Ag2WO4 and CoFe2O4 were successfully dispersed on the surface of BiOI and heterogeneous hybrid was generated. The separation of electrons and holes (h+) could be efficiently promoted due to the combination of Ag2WO4, BiOI and CoFe2O4 with suitable match of band gaps under FSL irradiation. The experimental results manifested that Ag2WO4 content, fluorescent light irradiation, inorganic carbonate ions and SO2 gas all possessed conspicuous effects on Hg0 removal. Among the heterogeneous photocatalysts, Ag2WO4(0.1)BiOI/CoFe2O4 demonstrated the optimal activity for Hg0 removal and superior stable performance, which also could be easily recovered from the reaction solution by an extra magnet. Superoxide radicals (O2−) and holes (h+) were confirmed to be the main reactive substances for higher Hg0 removal.

Study on removal of elemental mercury over MoO3-CeO2/cylindrical activated coke in the presence of SO2 by Hg-temperature-programmed desorption

MoO3-CeO2/cylindrical activated coke samples (MoCeY/AC) synthesized by an impregnation method were employed to investigate elemental mercury (Hg0) removal at 60–210 °C from simulated flue gas without HCl. MoCe0.5/AC with an optimal Mo/Ce molar ratio of 0.5 exhibited an excellent Hg0 removal efficiency (94.74%) at 120 °C, as well as good stability and prominent resistance to SO2 and H2O. The physicochemical property of the samples and the Hg0 removal mechanism were discussed by ICP-AES, SEM, EDX, BET, XRD, H2-TPR, XPS and Hg-TPD. The results of characterizations showed that MoCe0.5/AC possessed the special petal-like outer microstructure, large BET surface area, well-dispersed metal oxides and high reducibility, which was conducive for Hg0 removal. Furthermore, the synergistic effect between Mo6+ and Ce3+ was favorable to the high Hg0 removal performance by providing high valence Ce. According to the Hg-TPD tests, the chemisorption of Hg0 was a major approach for Hg0 removal, while physisorption and catalytic oxidation were just accounted for a tiny fraction. Moreover, the chemisorbed mercury could be validly distinguished into weakly-HgO, strongly-HgO, Oα-HgO and HgSO4 (when SO2 was added). Compared with raw AC, MoCe0.5/AC could enhance the Hg0 oxidation performance and produce Oα-HgO during the Hg0 removal process. In addition, the possible reason for the high SO2 tolerance of MoCe0.5/AC was examined: (i) the preferential combination between sulfate and MoO3 could protect CeO2 for Hg0 removal; (ii) SO2 could contribute to the formations of weakly-HgO and HgSO4. Finally, the regenerability of MoCe0.5/AC was also discussed.

ZnS/AC sorbent derived from the high sulfur petroleum coke for mercury removal

Porous carbon-based sorbents are considered as one of the most promising materials for solving atmospheric mercury pollution. In this study, a novel porous carbon-based sorbents ZnS/AC were prepared from high sulfur petroleum coke (HSPC) and zinc nitrate by in-situ method. The as-prepared ZnS/AC sorbents were characterized by BET, XRD, ICP-OES and XPS analyses, and the element mercury removal performance of these sorbents from the simulated coal derived fuel gas were evaluated using a bench-scale fixed-bed reactor. The effects of atmospheres and temperatures on the Hg0 removal performance of ZnS/AC sorbents were also studied. The mercury removal efficiency could maintain above 84% within 4 h at ≤120 °C under N2 + H2 + H2S atmospheres. The higher temperature was not conducive to mercury removal. The average mercury removal efficiency was only 30% within 2 h at 180 °C. Hydrogen sulfide (H2S) significantly improved the mercury removal performance of the ZnS/AC sorbent, while the concentration of H2S hardly affected the mercury removal efficiency. The mercury removal efficiency of the regenerated ZnS/AC sorbents after mercury capture still maintained above 85% within 6 h at 120 °C after three cycles of capture-regeneration, it can be concluded that ZnS/AC sorbent is a promising and efficient sorbent for removing elemental mercury from fuel gases.

Elemental mercury removal over a novel starch-modified MnOx/bentonite composite

To improve the activity of elemental mercury (Hg0) removal over the bentonite supported MnOx material (MnOx/bentonite), a novel starch-modified MnOx/bentonite composite (MnOx/starch-bentonite) was synthesized for Hg0 capture. The Hg0 removal activity tested under the atmosphere of pure N2 and in the presence of O2 showed that the MnOx/starch-bentonite exhibited better activity and stability than MnOx/bentonite. It was evident that the Hg0 removal efficiency over the novel catalytic sorbent (BS10M2) only declined by 16.9%, while that over MnOx/bentonite fell by 68.7% after a 5 h test under the atmosphere of N2 + 6%O2 at 120 °C. The starch modification decreased the surface area but enhanced the surface activity of bentonite, and more activate sites were generated on the surface of bentonite after being impregnated with potassium permanganate (KMnO4) solution. The improved Hg0 removal performance was probably due to the generation of more Mn4+ and the newly introduced ester groups formed by the partial oxidation reaction between starch and KMnO4 on the support, which played essential roles in mercury catalytic oxidation and adsorption. The MnOx were generated in two ways: KMnO4 decomposition in a neutral solution condition and KMnO4 reduction by the starch with hydroxyl groups.

High-efficient adsorption and removal of elemental mercury from smelting flue gas by cobalt sulfide.

Nonferrous metal smelting produces a large amount of Hg0 in flue gas, which has caused serious damage to the environment and human health. In this work, amorphous cobalt sulfide was synthesized by a liquid-phase precipitation method and was used for capturing gaseous Hg0 from simulated smelting flue gas at low temperatures (50~150°C). In the adsorption process, Hg0 can be transformed into the stable mercury compound, which is confirmed to be HgS by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of Hg (Hg-TPD) analysis. Meanwhile, XPS results also demonstrate that S22- species on the surface of cobalt sulfide play an important role in Hg0 transformation. At the temperature of 50°C (inlet Hg0 concentration of 214μg·m-3), the Hg0 adsorption capacity of cobalt sulfide (penetration rate of 25%) is as high as 2.07mg·g-1, which is much higher than that of popular adsorbents such as activated carbons and metal oxides. In addition, it was found that the Hg0 removal efficiency by cobalt sulfide in the flue gas with high concentration of SO2 (5%) remained more than 94%. The good adsorption and Hg0 removal performance guarantee cobalt sulfide the great superiority and application potential in the treatment of Hg0 in smelting flue gas with high concentration of SO2.

Nanoconfinement of Ag nanoparticles inside mesoporous channels of MCM-41 molecule sieve as a regenerable and H2O resistance sorbent for Hg0 removal in natural gas

A facile passivation treatment and amino functionalized method was developed for controllable synthesis of effective and water-resistant Ag/MCM-41 composite sorbent for Hg0 removal in natural gas. The Ag nanoparticles were successively confined inside the mesoporous channels of MCM-41 molecule sieve with an average diameter of 3 nm. The synthesized sorbent was found to achieve a complete removal of Hg0 at high space velocity of 50,000 h−1 in ambient temperature. At 5% breakthrough, the Hg0 capture capacity of 1% (wt%) silver loaded Ag/MCM-41 was as high as 6.64 mg·g−1, which is much higher than the sample of Ag loaded outside of the pore channels (S-Ag/MCM-41) and other existing commercial sorbents. The H2O has negligible inhibitory effect on Hg0 removal performance of Ag/MCM-41. In addition, the spent Ag/MCM-41 could be easily regenerated without significant performance degradation over five cycles. We considered the high Hg0 capture efficiency, large adsorption capacity and excellent regeneration performance of Ag/MCM-41 are contributed to the nanoconfinement effect of mesoporous channels of MCM-41 molecule sieve which effectively prevented the growth and agglomeration of Ag nanoparticles. The good hydrophobicity of Ag/MCM-41 is beneficial for the high resistance to H2O. This work represents a giant step toward the preparation of effective sorbent for practical applications of Hg0 removal in natural gas.

Synergistic effect between H2O and SO2 on mercury removal by activated carbon in O2/CO2 conditions

AbstractBACKGROUNDThis work evaluated the mechanism of H2O on mercury oxidation and adsorption by activated carbon in simulated flue gas in a fixed‐bed reactor. The effect of the addition of SO2 on the mercury removal was also discussed. Mercury desorption tests were conducted in a setup for classifying mercury forms adsorbed on activated carbon by the temperature‐programmed desorption (TPD) method.RESULTSThe results indicated that H2O could inhibit Hg0 removal through blocking the microporous channels of activated carbon. Additionally, the enriched H2O could provide the electrons to inhibit Hg0 oxidation. While medium H2O concentrations around 15% could dominate the competitive adsorption in O2/CO2, high and low H2O concentrations of 23% and 8%, respectivly, could not dominate the competition.CONCLUSIONWith the addition of SO2 in O2/CO2, Hg0 removal efficiency decreased with H2O increased from 8% to 23%. Furthermore, Hg0 adsorption proportion were all larger than 87% with the addition of SO2 with H2O in O2/CO2, which indicated that Hg0 adsorption was the main contributor to Hg0 removal performance. These results are useful for the control of mercury in O2/CO2 combustion technology. © 2018 Society of Chemical Industry