Effects Of Flue Gas Components Research Articles

CaO hydrated with ethanol solution for flue gas HCl immobilization. Part II: Influences of gas components

The injection of alkaline adsorbent into flue gas for HCl removal technology is greatly impacted by the complex flue gas components. The newly developed ethanol-modified Ca-based adsorbent was demonstrated a superior dechlorination performance. In this work, the effect of flue gas components on the dechlorination was comprehensively studied by experiments, micro-insight characterization and mechanism analyses. The results showed that the high initial HCl concentration boosts the reaction rate but lowers the Ca/Cl mole ratio. O2 promotes the HCl adsorption efficiency by impelling the reaction between HCl and adsorbent to generate Ca(ClO)2 that enhances the chlorination and converting CaClOH to CaO. The presence of SO2 and CO2 hinders the removal of HCl in both physical and chemical aspects. The product layers of CaSO3 and CaCO3 may cover the adsorbent active sites that deteriorates the pore structure and seriously inhibits the adsorption of HCl on the adsorbent surface and prevents mass diffusion into the inner pores. It was discovered that HCl, SO2 and CO2 have an affinity to the Ca site, so there exists nonnegligible competitive adsorption between them that reduces the number of basic sites to which HCl can adhere. The HCl removal efficiency falls from 72.33% to 41.34% as SO2 concentration rises from 0 ppm to 1600 ppm. While it decreases from 72.33% to 51.17% as CO2 concentration changes from 0% to 20%.

Microscopic insights on the effects of flue gas components on CH4–CO2 replacement in natural gas hydrate

Microscopic insights on the effects of flue gas components on CH4–CO2 replacement in natural gas hydrate

Effect of flue gas components on the removal of cadmium pollutants by transition metal-modified activated carbon: Density functional theory and thermodynamic study

Removal of cadmium (Cd) pollutants from waste incineration (MSW) flue gas by modified activated carbon (AC) is of great potential, yet the influence of flue gas composition on their interaction mechanism is still unclear. Thus, density functional theory and thermodynamic analyses were combined to explore the effects of typical flue gas compositions (O2, HCl, NO, SO2, CO2, and H2O) on Cd species capture over the Fe/AC and Mn/AC surfaces. All flue gas compositions inhibit the adsorption of Cd species, wherein their inhibitory effects are mainly divided into two categories, i.e., one with moderate inhibition (HCl, CO2, and H2O), and the other with significant inhibition (O2, NO, and SO2). For the first category, HCl forms new active sites after adsorption on the surface, while CO2 and H2O have weak competitiveness with Cd species, resulting in mild inhibitory effects. Nevertheless, O atoms of O2/SO2 and N atoms of NO are highly effortless to bond with Fe/Mn atoms, and strongly exclude the Cd adsorption on the active sites, greatly weakening their binding strength. According to thermodynamic analysis, the fixation of Cd species by Fe/AC and Mn/AC spontaneously proceeds with the interference of flue gas components, while the selectivity to Cd species decreases with the increased temperature. In summary, it is instrumental to adjust the operating parameters and AC injection location to attenuate the negative effects of O2, SO2, NO, and high temperature on Cd capture by Fe/AC and Mn/AC.

Influence of flue gas components on the mercury adsorption/oxidation by mechanochemical S2Cl2-modified sawdust coke

The effects of flue gas components (O2, CO2, SO2 and NO) on the Hg0 removal of mechanochemical S2Cl2-modified BC (S2Cl2-MC) were explored based on the Hg0 removal efficiency/amount, Hg0 adsorption amount and Hg2+ escape amount/ratio. The BET, FTIR, XPS, and Hg-TPD were used to obtain relevant physicochemical properties. It shows O2 and CO2 promote the Hg2+ escape but inhibit Hg0 adsorption. O2 slightly affects Hg0 removal, while CO2 promotes it. 400 ∼ 800 ppm SO2 slightly affect Hg0 removal, while 1200 ppm SO2 facilitates Hg2+ escape and Hg0 adsorption. SO2 affects Hg2+ escape ratio little. As NO concentration increases, the Hg2+ escape is promoted while Hg0 adsorption is inhibited. O2 and CO2 do not change the mercury forms. SO2 and NO promote the production of HgSO4 and Hg(NO3)2, respectively. The Hg0 adsorption might mainly depend on the physical properties of adsorbents.

Effects of flue gas components on CrOOH adsorption by γ-Al2O3 during municipal solid waste incineration based on DFT analysis

Cr pollutants released during the incineration of municipal solid waste (MSW) are volatile, biotoxic and pose carcinogenic risks under long-term exposure. In this study, density functional theory (DFT) was used to examine the impacts of flue gas components (FGCs) on CrOOH adsorption by γ-Al2O3. The investigated FGCs included O2, HCl, SO2, H2O, and CO2.The impacts of FGCs on the average adsorption energy of CrOOH by γ-Al2O3 were ranked as: O2 > SO2 > H2O > HCl > CO2. The effects of FGCs on CrOOH adsorption were manifested by oxidation, electron transfer and competitive adsorption. O2 promoted the adsorption of CrOOH on γ-Al2O3 due to oxidation effect and electron transfer effect. SO2 and H2O presented an electron transfer effect and weak oxidation effect, which limited their ability to promote CrOOH adsorption by γ-Al2O3. The competitive adsorption effects of HCl and CO2 were dominant and inhibited CrOOH adsorption by γ- Al2O3. The simulation results explained the role of FGCs on CrOOH capture by γ-Al2O3 and provided guidance for chromium control.

Effect of flue gas components on the NO removal and element mercury oxidation performance of Mn-modified low-temperature catalyst

Abstract The development of a low-temperature water and sulfur-resistant catalyst with high efficiency of NO removal and element mercury Hg(0) oxidation performance is one of the main directions for the synergistic removal of multiple pollutants from flue gas. The transition metal Mn is used to modify the V-W/Ti catalyst to prepare a modified Mn-SCR catalyst. The effects of Mn loading and complex flue gas components (SO2, H2O and HCl) on the modified catalysts activity were investigated on a small fixed-bed experimental bench, respectively. As the Mn loading increases, the acid sites on the catalyst surface are significantly enhanced, the window of NO removal temperature is significantly widened, and the Hg(0) oxidation performance is nearly 100%. The optimal loading amount of Mn is 0.2(Mn/Ti, mol). When the Mn loading exceeds 0.2, the particles on the catalyst surface sinter, and the specific surface area decreases. However, little difference is observed in catalyst activity. When SO2 and H2O are present in the flue gas, dual-action catalyst activity can be significantly suppressed, but the effect of H2O on catalyst activity is greater than that of SO2. With the increase of the HCl concentration from 0 ppm to 50 ppm, the oxidation efficiency of Hg(0) and the removal efficiency of NO increased slightly.

The redistribution of arsenic during the interaction between high-temperature flue gas and ash

Transformation of As in the post-combustion zone has a significant effect on its emission characteristics. In this study, redistribution of As that occurs during the interaction between flue gas and ash has been elucidated using a double-layer fixed-bed reactor at 800–1000 °C. Herein, flue gas and ash samples with different As contents and inorganic components were produced by two varieties of coals. The As content in the ash with high Ca and Al contents increased after interacting with the flue gas with a high As content, indicating gaseous As adsorption. However, the As content in the ash decreased by up to 67% for other cases. The blank experiments showed that the As occurrences in ash were thermally stable, suggesting that the decrease was caused by the action of flue gas. Accordingly, the effect of flue gas components on the release of As from the ash was investigated. It was found that a significant amount of As release was primarily caused by the reaction of gaseous Na in the flue gas with the residual As in ash. A bi-directional interaction was observed between the high-temperature flue gas and ash, which led to the redistribution of As.

Effect of flue gas components on Hg0 oxidation and adsorption by modified walnut shell coke in O2/CO2 atmosphere

AbstractWalnut shell was pyrolyzed and then impregnated with NH4Br to make sorbent for Hg0 removal. The effect of flue gas components on Hg0 removal performance was studied in O2/CO2 atmosphere, and the results were compared with those in O2/N2 atmosphere. The mercury valence distribution during adsorption was obtained. NH4Br‐modified walnut shell coke promoted Hg0 removal, the Br‐containing chemisorption site was a crucial factor. Although addition of CO2 did not introduce new oxygen‐containing functional groups or change the mercury species, Hg0 removal efficiency increased significantly. This may be because CO2 can increase the active sites on the carbon surface. In O2/N2 atmosphere, O2 promoted formation of active center on the sorbent surface, which made Hg0 more easily adsorbed and then reacted with Br‐functional group to form more HgBr2. In O2/CO2 atmosphere, O2 promoted formation of some reactive carbon–oxygen complexes which acted as catalyst to facilitate Hg0 oxidation and formation of HgO. NO improved removal of Hg0, because the C─O functional group on the sorbent surface could catalyze the conversion of NO to NO2 in the adsorbed state and then formed Hg2(NO3)2. SO2 consumed oxygen on the sorbent surface and inhibited the Hg0 removal.

Co3O4 Nanorods with a Great Amount of Oxygen Vacancies for Highly Efficient Hg0 Oxidation from Coal Combustion Flue Gas

Oxidizing elemental mercury (Hg0) to Hg2+ is an effective way to remove Hg0 from flue gas. Surface-active oxygen species are considered to be important active sites in Hg0 oxidation process. The concentration enhancement of surface-active oxygen species is a primary challenge for this technology. Oxygen vacancies can easily capture and activate gaseous oxygen, forming more surface-active oxygen species, which may lead to a better Hg0 oxidation efficiency. Co3+ in Co3O4 can generate oxygen vacancies through the reduction of Co3+ to Co2+, and the oxygen vacancies formation process is controlled by Co2+/Co3+ ratio. Inspired by this, Co3O4 nanorods exposing (220) facet with a high Co3+/Co2+ ratio were successfully synthesized. Raman and X-ray photoelectron spectroscopy (XPS) results show that the high concentration of Co3+ leads to more oxygen vacancies. It results in a better catalytic performance for Co3O4 nanorods whose Hg0 oxidation efficiency remains above 90% at 180 000 h– in the temperature range of 100–300 °C. After 2880 min reaction, the Hg0 oxidation efficiency of Co3O4 nanorods reduces to about 72%, and it recovers to the original level after in situ thermal treatment at 550 °C, suggesting a great renewable property. Furthermore, XPS results of Co3O4 nanorods before and after the reaction show that the concentrations of Co3+ and surface-active oxygen decrease after the reaction. The reaction mechanism was revealed based on these results. Hg0 reacts with surface-active oxygen forming HgO, and the consumed oxygen is replenished by gaseous O2. Co3+/Co2+ redox couple can improve the electron-transfer activity to enhance the Hg0 oxidation efficiency in the presence of O2. The effects of flue gas components on the Hg0 oxidation efficiency are also investigated. O2 and NO have positive effects, while H2O and SO2 have negative effects on the Hg0 removal process. However, Co3O4 nanorods still have an efficiency of 75% even in the presence of 8% H2O and 200 ppm SO2.

High efficiency of Mn–Ce‐modified TiO2 catalysts for the low‐temperature oxidation of Hg0 under a reducing atmosphere

Manganese‐ and cerium oxide‐modified titania catalysts were prepared by the deposition precipitation for the removal of elemental mercury (Hg0) from simulated yellow phosphorus off‐gas at low temperature. In addition, these catalysts were characterized by X‐ray diffraction, Brunauer–Emmett–Teller measurements, X‐ray photoelectron spectroscopy and field‐emission scanning electron microscope to determine the surface morphology of the obtained compounds and explore their formation mechanism. The results revealed that a Mn–Ce loading and reaction temperature of 10% and 150 °C, respectively, as well as a Mn/Ce molar ratio of 2:1, led to an optimal efficiency for the oxidation of elemental mercury. Furthermore, the effects of flue gas components were investigated. The presence of O2 clearly promoted the oxidation of Hg0. A CO atmosphere did not affect the Hg0 oxidation, when compared with N2, whereas the presence of H2S and water vapor inhibited the oxidation process. Furthermore, the X‐ray photoelectron spectroscopy spectra of Hg 4f revealed that the elemental mercury adsorbed by the catalyst is present as HgO. Finally, the Hg0 catalytic oxidation mechanism was discussed on the basis of the experimental results and characterization analysis.

Role of flue gas components in Hg0 oxidation over La0.8Ce0.2MnO3 perovskite catalyst in coal combustion flue gas

La0.8Ce0.2MnO3 perovskite catalyst was employed for elemental mercury (Hg0) oxidation in coal combustion flue gas. The effects of flue gas components, including O2, NO, SO2, HCl, H2O as well as the selective catalytic reduction (SCR) reductant (NH3), on Hg0 oxidation were investigated systematically. Above 90% Hg0 oxidation was obtained at 200 °C under simulated flue gas (SFG) and SCR atmosphere with a gas hourly space velocity of 60,000 h−1. Gaseous O2 regenerated and replenished surface oxygen, hence promoting the oxidation of Hg0. NO promoted the Hg0 oxidation because of the formation of active surface species like NO2. HCl facilitated the Hg0 oxidation, and 98.8% Hg0 oxidation was obtained under the atmosphere containing 10 ppm HCl in the co-presence of O2. SO2 inhibited Hg0 oxidation because of the irreversible damage on catalytic activity by reacting with the active species on the catalyst·H2O also inhibited Hg0 oxidation due to the change of catalyst surface chemistry as well as the consumption of active surface chlorine species (Cl∗). NH3 competed active sites with Hg0 and induced oxidized mercury reduction, hence limiting the Hg0 conversion. However, the inhibitive effect of NH3 could be partly offset by the promotional effect of NO. This work clarified the effects of flue gas compositions on Hg0 oxidation over a novel La0.8Ce0.2MnO3 perovskite catalyst, which is essential for further improving the catalyst activity.

Simultaneous NO Removal and Hg0 Oxidation over CuO Doped V2O5-WO3/TiO2 Catalysts in Simulated Coal-Fired Flue Gas

A series of CuO doped V2O5-WO3/TiO2 based commercial selective catalytic reduction (SCR) catalysts were synthesized via the improved impregnation method for simultaneous NO removal and Hg0 oxidation under simulated coal-fired flue gas at a temperature range of 150–400 °C. Several characterization techniques, including Brunauer–Emmett–Teller analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction of H2 (H2-TPR), were used to characterize the catalysts. The results indicated that Cu3-SCR catalyst exhibited the superior catalytic activity and a wide active temperature window for simultaneous NO removal and Hg0 oxidation. The effects of flue gas components on the catalytic activity were also investigated. The results indicated that Cu3-SCR catalyst showed good performances on SO2 tolerance and H2O resistance. The effect of Hg0 on NO removal was almost negligible. However, the copresence of NO and NH3 obviously inhibited the Hg0 oxidation activity. Furthe...

Comparison of Elemental Mercury Oxidation Across Vanadium and Cerium Based Catalysts in Coal Combustion Flue Gas: Catalytic Performances and Particulate Matter Effects.

This paper discussed the field test results of mercury oxidation activities over vanadium and cerium based catalysts in both coal-fired circulating fluidized bed boiler (CFBB) and chain grate boiler (CGB) flue gases. The characterizations of the catalysts and effects of flue gas components, specifically the particulate matter (PM) species, were also discussed. The catalytic performance results indicated that both catalysts exhibited mercury oxidation preference in CGB flue gas rather than in CFBB flue gas. Flue gas component studies before and after dust removal equipment implied that the mercury oxidation was well related to PM, together with gaseous components such as NO, SO2, and NH3. Further investigations demonstrated a negative PM concentration-induced effect on the mercury oxidation activity in the flue gases before the dust removal, which was attributed to the surface coverage by the large amount of PM. In addition, the PM concentrations in the flue gases after the dust removal failed in determining the mercury oxidation efficiency, wherein the presence of different chemical species in PM, such as elemental carbon (EC), organic carbon (OC) and alkali (earth) metals (Na, Mg, K, and Ca) in the flue gases dominated the catalytic oxidation of mercury.

The enhancement of CuO modified V2O5-WO3/TiO2 based SCR catalyst for Hg° oxidation in simulated flue gas

CuO modified V2O5-WO3/TiO2 based SCR catalysts prepared by improved impregnation method were investigated to evaluate the catalytic activity for elemental mercury (Hg°) oxidation in simulated flue gas at 150–400 °C. Nitrogen adsorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. It was found that V0.8WTi-Cu3 catalyst exhibited the superior Hg° oxidation activity and wide operating temperature window at the gas hourly space velocity (GHSV) of 3 × 105 h−1. The BET and XRD results showed that CuO was well loaded and highly dispersed on the catalysts surface. The XPS results suggested that the addition of CuO generated abundant chemisorbed oxygen, which was due to the synergistic effect between CuO and V2O5. The existence of the redox cycle of V4+ + Cu2+ ↔ V5+ + Cu+ in V0.8WTi-Cu3 catalyst enhanced Hg° oxidation activity. The effects of flue gas components (O2, NO, SO2 and H2O) on Hg° oxidation over V0.8WTi-Cu3 catalyst were also explored. Moreover, the co-presence of NO and NH3 remarkably inhibited Hg° oxidation, which was due to the competitive adsorption and reduction effect of NH3 at SCR condition. Fortunately, this inhibiting effect was gradually scavenged with the decrease of GHSV. The mechanism of Hg° oxidation was also investigated.

Effect of flue gas components on the adsorption of sulfur oxides on CaO(1 0 0)

Due to the prevalence of coal combustion technologies utilizing calcium-based materials, it is important to understand the varied reactions between the flue gas species and these calcium-based materials. Of particular importance is the reaction between sulfur oxides (SO2 or SO3) and calcium oxide (CaO), which plays an important role in sulfur retention on fly ash during oxy-coal combustion or carbon capture with calcium looping. To better understand these reactions, density functional theory (DFT) calculations were performed investigating SOx binding to CaO surfaces functionalized by other flue gas components. Analyses of the energetic, geometric and electronic nature of the modeled systems were conducted. Generally, the most stable conformation on the surface is in the form of either a sulfite- or sulfate-like structure. Water can have an effect on sulfur binding by introducing other favorable intermediate conformations, while carbon dioxide could negatively impact adsorption by weakening sulfur-surface bonds.

Effects of flue gas components on removal of elemental mercury over Ce–MnOx/Ti-PILCs

The adsorption and oxidation of elemental mercury (Hg0) under various flue gas components were investigated over a series of Ce–MnOx/Ti-PILC catalysts, which were synthesized by an impregnation method. To discuss the mechanism, the catalysts were characterized by various techniques such as N2 adsorption–desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) analysis and X-ray photoelectron spectroscopy (XPS). The results indicated that the presence of 500ppm SO2 in the flue gas significantly restrained the Hg0 adsorption and oxidation over 6%Ce–6%MnOx/Ti-PILC due to the formation of SO42− species. Hg0 could be oxidized to HgCl2 in the presence of HCl, because the Deacon process occurred. NO would react with active oxygen to form NO2-containing species, which facilitated Hg0 oxidation. While the presence of NO limited the Hg0 adsorption on 6%Ce–6%MnOx/Ti-PILC due to the competitive adsorption of NO with Hg0. The addition of NH3 in the flue gas significantly restrained Hg0 adsorption and oxidation, because the formed NH4+ species covered the active adsorption sites on the surfaces, and further limited Hg0 oxidation. However, when NO and NH3 were simultaneously added into the flue gas, the Hg0 oxidation efficiency of 6%Ce–6%MnOx/Ti-PILC exhibited a relatively high value (72%) at 250°C, which indicated the practicability to use Ce–MnOx/Ti-PILC for Hg0 removal under SCR conditions.

Effect of SO2 on CO2 Absorption in Flue Gas by Ionic Liquid 1-Ethyl-3-methylimidazolium Acetate

Significant efforts are being made to develop several novel solvents or materials for postcombustion CO2 capture technology. Traditional amine solvents suffer from mass loses due to its volatility and poisoning by flue gas impurities. Ionic liquids (ILs) are considered to be promising alternatives for CO2 capture due to their unique features, such as negligible vapor pressure. Despite the extensive research on CO2 capture by ILs, few studies have investigated the effect of flue gas components on CO2 absorption performance. Because of the large differences between CO2 and SO2 in the absorption capacity and partial pressure in flue gas, it is essential to study the role of SO2 in CO2 capture using ILs. This work focused on studying the effect of SO2 with low concentration on postcombustion CO2 capture by 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] and explaining the microscopic mechanism through quantum chemical calculation. Results showed that the CO2 absorption capacity was largely decreased by 25% i...

Effects of flue gas components on the oxidation of gaseous Hg0 by dielectric barrier discharge plasma

This study investigated the effects of gas components on the oxidation of Hg0 by dielectric barrier discharge (DBD) non-thermal plasma (NTP) technology. The findings indicated that reactive species such as O and Cl generated by ionization of O2 and HCl played dominant roles during oxidation processes. The presence of 50ppm of HCl in N2/O2 atmosphere enhanced the Hg0 oxidation, the complete oxidation of Hg0 was observed by 6kV of applied voltage. The presence of NO in the reactor decreased the Hg0 oxidation efficiency due to the interference by NO reaction with O and O3. The addition of 310ppm of NO into the flue gas remained in 55% of Hg0 oxidation efficiency. Water vapor inhibited Hg0 oxidation, which was attributed to the consumption of reactive species and decomposition of HgOH. SO2 had a slight promoting effect on Hg0 oxidation, compared with the absence of SO2, the oxidation efficiency increased by 2–8% with the addition of 100–200ppm of SO2. This study leads to starting the development of a novel promising environmental technology for Hg removal in the flue gas.

The enhance effect of atomic Cl in CuCl2/TiO2 catalyst for Hg0 catalytic oxidation

The effect of flue gas components on the Hg-0 oxidation efficiency of CuO/TiO2 and CuCl2/TiO2 catalysts was investigated. The results indicated that HCl and O-2 in the atmosphere positively affect Hg-0 oxidation, and HCl is more effective than O-2. Meanwhile, atomic Cl and O in the catalyst also play crucial roles in the Hg-0 oxidation process. Thermogravimetry (TG), X-ray Diffractograms (XRD), Brunauer-Emmet-Teller (BET) and X-ray photoelectron spectroscopy (XPS) technologies were adopted to characterize the raw CuCl2/Tio(2) catalyst. The Hg-0 oxidation mechanisms over CuO/TiO2 and CuCl2/TiO2 catalysts were discussed. Both HCl and O-2 gases were found to be necessary to revert to CuO or CuCl2 via an intermediate step. The CuCl2/TiO2 catalyst has a potential industrial application because it has a certain oxidation activity in the absence of HCl, high stability and a large temperature window. (C) 2014 Elsevier B.V. All rights reserved.

Utilization of simulated flue gas for cultivation of Scenedesmus dimorphus

Effects of flue gas components on growth of Scenedesmus dimorphus were investigated and two methods were carried out to eliminate the inhibitory effects of flue gas on microalgae. S. dimorphus could tolerate CO2 concentrations of 10–20% and NO concentrations of 100–500ppm, while the maximum SO2 concentration tolerated by S. dimorphus was 100ppm. Addition of CaCO3 during sparging with simulated flue gas (15% CO2, 400ppm SO2, 300ppm NO, balance N2) maintained the pH at about 7.0 and the algal cells grew well (3.20gL−1). By intermittent sparging with flue gas controlled by pH feedback, the maximum biomass concentration and highest CO2 utilization efficiency were 3.63gL−1 and 75.61%, respectively. These results indicated that S. dimorphus could tolerate high concentrations of CO2 and NO, and the methods of CaCO3 addition and intermittent sparging have great potential to overcome the inhibition of flue gas on microalgae.