Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Modeling And Experimental Studies Of Mercury Oxidation And Adsorption In A Fixed Bed Reactor
Download Modeling And Experimental Studies Of Mercury Oxidation And Adsorption In A Fixed Bed Reactor full books in PDF, epub, and Kindle. Read online Modeling And Experimental Studies Of Mercury Oxidation And Adsorption In A Fixed Bed Reactor ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed Reactor by :
Download or read book Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed Reactor written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents experimental and modeling mercury oxidation and adsorption data. Fixed-bed and single-particle models of mercury adsorption were developed. The experimental data were obtained with two reactors: a 300- W, methane-fired, tubular, quartz-lined reactor for studying homogeneous oxidation reactions and a fixed-bed reactor, also of quartz, for studying heterogeneous reactions. The latter was attached to the exit of the former to provide realistic combustion gases. The fixed-bed reactor contained one gram of coconut-shell carbon and remained at a temperature of 150oC. All methane, air, SO2, and halogen species were introduced through the burner to produce a radical pool representative of real combustion systems. A Tekran 2537A Analyzer coupled with a wet conditioning system provided speciated mercury concentrations. At 150°C and in the absence of HCl or HBr, the mercury uptake was about 20%. The addition of 50 ppm HCl caused complete capture of all elemental and oxidized mercury species. In the absence of halogens, SO2 increased the mercury adsorption efficiency to up to 30 percent. The extent of adsorption decreased with increasing SO2 concentration when halogens were present. Increasing the HCl concentration to 100 ppm lessened the effect of SO2. The fixed-bed model incorporates Langmuir adsorption kinetics and was developed to predict adsorption of elemental mercury and the effect of multiple flue gas components. This model neglects intraparticle diffusional resistances and is only applicable to pulverized carbon sorbents. It roughly describes experimental data from the literature. The current version includes the ability to account for competitive adsorption between mercury, SO2, and NO2. The single particle model simulates in-flight sorbent capture of elemental mercury. This model was developed to include Langmuir and Freundlich isotherms, rate equations, sorbent feed rate, and intraparticle diffusion. The Freundlich isotherm more accurately described in-flight mercury capture. Using these parameters, very little intraparticle diffusion was evident. Consistent with other data, smaller particles resulted in higher mercury uptake due to available surface area. Therefore, it is important to capture the particle size distribution in the model. At typical full-scale sorbent feed rates, the calculations underpredicted adsorption, suggesting that wall effects can account for as much as 50 percent of the removal, making it an important factor in entrained-mercury adsorption models.
Book Synopsis Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed and Entrained-Flow Reactor by :
Download or read book Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed and Entrained-Flow Reactor written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents experimental and modeling mercury oxidation and adsorption data. Fixed-bed and single-particle models of mercury adsorption were developed. The experimental data were obtained with two reactors: a 300-W, methane-fired, tubular, quartz-lined reactor for studying homogeneous oxidation reactions and a fixed-bed reactor, also of quartz, for studying heterogeneous reactions. The latter was attached to the exit of the former to provide realistic combustion gases. The fixed-bed reactor contained one gram of coconut-shell carbon and remained at a temperature of 150oC. All methane, air, SO2, and halogen species were introduced through the burner to produce a radical pool representative of real combustion systems. A Tekran 2537A Analyzer coupled with a wet conditioning system provided speciated mercury concentrations. At 150°C and in the absence of HCl or HBr, the mercury uptake was about 20%. The addition of 50 ppm HCl caused complete capture of all elemental and oxidized mercury species. In the absence of halogens, SO2 increased the mercury adsorption efficiency to up to 30 percent. The extent of adsorption decreased with increasing SO2 concentration when halogens were present. Increasing the HCl concentration to 100 ppm lessened the effect of SO2. The fixed-bed model incorporates Langmuir adsorption kinetics and was developed to predict adsorption of elemental mercury and the effect of multiple flue gas components. This model neglects intraparticle diffusional resistances and is only applicable to pulverized carbon sorbents. It roughly describes experimental data from the literature. The current version includes the ability to account for competitive adsorption between mercury, SO2, and NO2. The single particle model simulates in-flight sorbent capture of elemental mercury. This model was developed to include Langmuir and Freundlich isotherms, rate equations, sorbent feed rate, and intraparticle diffusion. The Freundlich isotherm more accurately described in-flight mercury capture. Using these parameters, very little intraparticle diffusion was evident. Consistent with other data, smaller particles resulted in higher mercury uptake due to available surface area. Therefore, it is important to capture the particle size distribution in the model. At typical full-scale sorbent feed rates, the calculations underpredicted adsorption, suggesting that wall effects can account for as much as 50 percent of the removal, making it an important factor in entrained-mercury adsorption models.
Download or read book Lüdin Max (1919-?). written by and published by . This book was released on 1939 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zeitungsausschnitte.
Book Synopsis Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine by : Andrew Rodger Fry
Download or read book Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine written by Andrew Rodger Fry and published by . This book was released on 2008 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mercury Oxidation Across the Selective Catalytic Reduction (SCR) Unit by : Ana Suarez Negreira
Download or read book Mercury Oxidation Across the Selective Catalytic Reduction (SCR) Unit written by Ana Suarez Negreira and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions from coal-fired power plants represent 32% of the total anthropogenic mercury emissions in the United States (60 tons in 2012, 2000 tons worldwide). In recent years, public concern has increased due to the long-term irreversible effects of mercury on the environment and human health. As a result, the U.S. Environmental Protection Agency (EPA) proposed in December 2011 the Mercury and Air Toxics Standards (MATS); which require U.S. natural gas and coal-fired power plants to install air pollution control devices to prevent 91% of the Hg present in flue gas from being released. Currently, there are several air pollution control devices designed to reduce Hg emissions in power plants and whose working principles depend on the nature of the mercury species. Mercury is present in the flue gas in three forms: elemental (Hg0), oxidized (Hg+2) and particulate (HgP). Oxidized Hg is highly soluble in aqueous solutions, as compared to the insoluble and nonreactive Hg0, thus allowing for the removal of the former by conventional air pollution control devices. As a matter of fact, the promotion of Hg0 oxidation along the path of the flue gas from the boiler to the stack is currently the best approach to remove it by using current emission control technologies. The catalytic oxidation of mercury can be obtained through specific Hg oxidation catalysts such as noble metals or as a co-benefit of existing control technologies such as the Selective Catalyst Reduction (SCR) unit for NOx reduction. The latter option would be particularly attractive due to the associated low economic investment, since 40% of electricity from coal sources is produced in power plants that are already equipped with SCR units. However, little is known about the fate of mercury across the SCR unit, since most of the research work has been devoted to their applicability for NOx reduction. Understanding which are the key factors controlling the oxidation of mercury and developing a detailed mechanism of Hg oxidation across the SCR unit is a primary objective of this dissertation. One of the main achievements of this work has been the integration of an atomic-scale model with bench-scale experiments to identify key factors in Hg oxidation as a co-benefit of the SCR unit. Widely employed materials in commercial SCR catalysts include titania-supported vanadium and tungsten oxides, i.e., V2O5-WO3-TiO2, which were therefore investigated in this study. Theoretical models were used to assess the role of each component, namely, the support (TiO2), the active phase (V2O5) and the promoters (WO3), on the activity of this catalyst towards Hg oxidation. These include both density functional theory and ab-initio thermodynamic calculations; the latter are applied to investigate the effects of temperature and flue gas composition (which is coal dependent) on the reactivity of the catalyst under realistic operating conditions. Active phase, support and structural promoter were incorporated progressively into the analysis, thereby modeling the SCR catalyst with an increased level of complexity. The DFT results show that the active phase, V2O5, alone is not reactive under flue gas conditions and that the presence of the support leads to an increase of its reactivity toward Hg oxidation, presumably due to the higher dispersion of the vanadia phase on the TiO2 surface. Particular focus was given to the interaction of water with the supported system, due the significant concentration of water vapor present in the flue gas (≈ 10%). It is shown that water interacts with the surface in either a molecular or dissociative fashion, depending on the water coverage, which is in turn temperature-dependent. Interestingly, a stabilization effect is observed at low water coverages, as the latter tends to dissociate on the surface, thus yielding a reconstructed surface with attached hydroxyl groups. Moreover, a dehydration process is observed that takes place with increasing temperature and that leads to a water-free surface above 390 K. The analysis of the reactivity of the supported vanadium oxide catalyst was completed by a study of the adsorption energies of gas species that likely play a role in Hg oxidation (i.e., Hg, HgCl, HCl and H2O). Hereby, it was observed that surfaces with high water coverage show higher reactivity towards HgCl (the gas specie with the highest adsorption energy) followed by HCl. The adsorption energies of Hg suggested a negligible interaction with the vanadia dimer. Ab initio thermodynamic calculations were carried out to take into account the effect of temperature and entropy loss on the adsorption energies of these species; based on these results, a mechanism to explain Hg oxidation to HgCl2 was proposed, which involves the adsorption of HCl and HgCl, following a Langmuir-Hinshelwood mechanism. As a final step in the theoretical analysis, the incorporation of WO3 into the model shows that these ternary systems (V2O5-WO3-TiO2) are even more reactive than the binary systems (V2O5-TiO2). First, the effect of the surface coverage was studied by comparing the reactivity of the low- and high-loading binary systems. This analysis indicated enhanced reactivity of the SCR catalyst toward HgCl, HCl and Hg, with increasing loadings of the active phase. The effect of the surface composition on the reactivity of the catalyst was estimated by comparing the reactivity of the binary monolayer systems (i.e., 100% V2O5-TiO2 or 100%WO3-TiO2) against ternary systems (V2O5-WO3-TiO2 with different V2O5/WO3 ratios). This study showed a higher reactivity of the ternary system, with the 75%V2O5-25%WO3-TiO2 system representing the optimal catalyst composition toward Hg oxidation. The theoretical studies were complemented by Hg oxidation experiments carried out in a lab-scale packed-bed reactor with the purpose of benchmarking some of the predictions of the computational work. The effects of flue gas composition, catalyst formulation, temperature and space velocity on the Hg oxidation efficiency of different SCR catalysts were examined under typical flue gas conditions. The effect of the catalyst composition on the activity toward Hg oxidation was analyzed by testing four different SCR catalysts: 4%V2O5-10%WO3-TiO2, 1%V2O5-10%WO3-TiO2, 1%V2O5-TiO2 and 10%WO3-TiO2). It was shown that the binary systems have a lower activity compared to the ternary systems, thus supporting the predictions from first-principles calculations described above. Through the kinetic analysis, parameters such as reaction orders and the apparent activation energy were derived. By using the power law equation, it was found that O2 is zeroth-order and Hg is first-order in terms of the Hg oxidation rate. For the case of HCl, the reaction order could not be estimated using such a simple equation, and a more complex equation is necessary to capture the complexities of the heterogeneous reaction pathway. The activation energy takes a value of about 40 kJ/mol and is in reasonable agreement with data from the literature. It is worth pointing out that the intrinsic difficulty of measuring very low Hg concentration (≈ 5 ppb) results in large uncertainties associated with relevant parameters such as oxidation efficiencies and reaction rates.
Book Synopsis Fundamental Understanding of Mercury Removal from Coal Combustion by : Erdem Sasmaz
Download or read book Fundamental Understanding of Mercury Removal from Coal Combustion written by Erdem Sasmaz and published by Stanford University. This book was released on 2011 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coal-fired power plants are a major anthropogenic source of worldwide mercury (Hg) emissions. Since mercury is considered to be one of the most toxic metals found in the environment, Hg emissions from coal-fired power plants is of major environmental concern. Mercury in coal is vaporized into its gaseous elemental form throughout the coal combustion process. Elemental Hg can be oxidized in subsequent reactions with other gaseous components (homogeneous) and solid materials (heterogeneous) in coal-fired flue gases. While oxidized Hg in coal-fired flue gases is readily controlled by its adsorption onto fly ash and/or its dissolution into existing solution-based sulfur dioxide (SO2) scrubbers, elemental Hg is not controlled. The extent of elemental Hg formed during coal combustion is difficult to predict since it is dependent on the type of coal burned, combustion conditions, and existing control technologies installed. Therefore, it is important to understand heterogeneous Hg reaction mechanisms to predict the speciation of Hg emissions from coal-fired power plants to design and effectively determine the best applicable control technologies. In this work, theoretical and experimental investigations have been performed to investigate the adsorption and in some cases the oxidation, of Hg on solid surfaces, e.g., calcium oxide (CaO), noble metals and activated carbon (AC). The objective of this research is to identify potential materials that can be used as multi-pollutant sorbents in power plants by carrying out both high-level density functional theory (DFT) electronic structure calculations and experiments to understand heterogeneous chemical pathways of Hg. This research uses a fundamental science-based approach to understand the environmental problems caused by coal-fired energy production and provides solutions to the power generation industry for emissions reductions. Understanding the mechanism associated with Hg and SO2 adsorption on CaO will help to optimize the conditions or material to limit Hg emissions from the flue gas desulfurization process. Plane-wave DFT calculations were used to investigate the binding mechanism of Hg species and SO2 on the CaO(100) surface. The binding strengths on the high-symmetry CaO adsorption sites have been investigated for elemental Hg, SO2, mercury chlorides (HgCl and HgCl2) and mercuric oxide (HgO). It has been discovered that HgCl, HgCl2, and SO2 chemisorb on the CaO(100) surface at 0.125 ML coverage. Binding energies of elemental Hg are minimal indicating a physisorption mechanism. Noble metals such as palladium (Pd), gold (Au), silver (Ag), and copper (Cu) have been proposed to capture elemental Hg. Plane-wave DFT calculations have been carried out to investigate the mercury interactions with Pd binary alloys and overlays in addition to pure Pd, Au, Ag, and Cu surfaces. It has been determined that Pd has the highest mercury binding energy in comparison to other noble metals. In addition, Pd is found to be the primary surface atom responsible for increasing the adsorption of Hg with the surface in both Pd binary alloys and overlays. Deposition of Pd overlays on Au and Ag has been found to enhance the reactivity of the surface by shifting the d-states of surface atoms up in energy. The possible binding mechanisms of elemental Hg onto virgin, brominated and sulfonated AC fiber and brominated powder AC sorbents have been investigated through packed-bed experiments in a stream of air and simulated flue gas conditions, including SO2, hydrogen chloride (HCl), nitrogen oxide (NO) nitrogen dioxide (NO2). A combination of spectroscopy and plane-wave DFT calculations was used to characterize the sorption process. X-ray photoelectron spectroscopy (XPS) and x-ray absorption fine structure (XAFS) spectroscopy were used to analyze the surface and bulk chemical compositions of brominated AC sorbents reacted with Hg0. Through XPS surface characterization studies it was found that Hg adsorption is primarily associated with halogens on the surface. Elemental Hg is oxidized on AC surfaces and the oxidation state of adsorbed Hg is found to be Hg2+. Though plane-wave DFT and density of states (DOS) calculations indicate that Hg is more stable when it is bound to the edge carbon atom interacting with a single bromine bound atop of Hg, a model that includes an interaction between the Hg and an additional Br atom matches best with experimental data obtained from extended x-ray absorption fine structure (EXAFS) spectroscopy. The flue gas species such as HCl and bromine (Br2) enhance the Hg adsorption, while SO2 is found to decrease the Hg adsorption significantly by poisoning the active sites on the AC surface. The AC sorbents represent the most market-ready technology for Hg capture and therefore have been investigated by both theory and experiment in this work. Future work will include similar characterization and bench-scale experiments to test the metal-based materials for the sorbent and oxidation performance.
Book Synopsis Experimental Investigation and Kinetic Modeling of Homogeneous Mercury Oxidation by Halogens by : Brydger Cauch
Download or read book Experimental Investigation and Kinetic Modeling of Homogeneous Mercury Oxidation by Halogens written by Brydger Cauch and published by . This book was released on 2008 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals of Mercury Oxidation in Flue Gas by :
Download or read book Fundamentals of Mercury Oxidation in Flue Gas written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO(subscript x), and SO2 concentrations, ash constituents, and temperature. This report summarizes Year 2 results for the experimental and modeling tasks. Experiments in the mercury reactor are underway and interesting results suggested that a more comprehensive look at catalyzed surface reactions was needed. Therefore, much of the work has focused on the heterogeneous reactions. In addition, various chemical kinetic models have been explored in an attempt to explain some discrepancies between this modeling effort and others.
Book Synopsis Mercury Oxidation and Adsorption Over Cupric Chloride-based Catalysts and Sorbents for Mercury Emissions Control by : Xin Li
Download or read book Mercury Oxidation and Adsorption Over Cupric Chloride-based Catalysts and Sorbents for Mercury Emissions Control written by Xin Li and published by . This book was released on 2012 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions control is of great importance in environment protection as well as public health. Current mercury emissions control technologies are not well designed nor optimized, mainly due to the lack of fundamental understanding of adsorption and/or catalytic mechanisms and necessary kinetic modeling and reliable simulation data. This work aims to advance the fundamental mechanistic understanding of heterogeneous catalytic oxidation reaction and adsorption by using the reaction between Hg(0) vapor and CuCl2 and the subsequent adsorption of resultant oxidized mercury onto sorbents. XANES and EXAFS were used to determine mercury compounds formed on AC sorbents. The XANES study on raw and CuCl2-impregnated AC sorbents suggests that little or no elemental mercury is formed onto any spent sorbents and the chemisorption of Hg(0) vapor is very likely to be the dominant mechanism. HgCl2 is found to be a major oxidation reaction product when CuCl2 and HCl were impregnated onto raw AC regardless of the type of the carrier gas (i.e. N2 or O2). The adsorption isotherms of HgCl2 on DARCO-HG and CuCl2-impregnated AC were found to be of the Langmuir type. The kinetic adsorption constants were estimated by fitting the model simulation with experimental data. The breakthrough data from experiments are in good agreement with the calculation results from the modified kinetic model. The simulation results indicate that pore diffusion resistance significantly increases with an increase in sorbent particle size. HgCl2 adsorption removal performance was also predicted in an entrained flow system using a modified model. The CuCl2/[alpha]-Al2O3 catalyst possesses high activity for the oxidation of Hg(0) to Hg2+, with an excellent stability under the environment similar to the flue gas from coal-fired power plants. The CuCl2 crystallites formed onto [alpha]-Al2O3 were very stable up to 300oC, and undergo the thermal reduction process from Cu(II) to Cu(0) via Cu(I). In the absence of HCl and O2 gases, CuCl2 was found to follow a Mars-Maessen mechanism by consuming lattice chlorine of CuCl2 for Hg(0) oxidation and to be reduced to CuCl. In the presence of 10 ppmv HCl, 2,000 ppmv SO2, and 6% O2 gases, the CuCl2/[alpha]-Al2O3 sample works as an Hg(0) oxidation catalyst exhibiting>90% conversion with good resistance to SO2 at 140oC. The reduced CuCl was able to be re-chlorinated to CuCl2 under HCl and O2 gases by following the Deacon reaction. Multiple copper species were found to be formed when [gamma]-Al2O3 is used as a substrate as opposed to one Cu(II) species on [alpha]-Al2O3. The CuCl2/[gamma]-Al2O3 catalysts with low CuCl2 loading (
Book Synopsis Adsorption and Coprecipitation Studies of Mercury on Hydrous Iron Oxide by : Peter Avotins
Download or read book Adsorption and Coprecipitation Studies of Mercury on Hydrous Iron Oxide written by Peter Avotins and published by . This book was released on 1975 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Studies of Mercury Oxidation by Anaerobic Bacteria by : Matthew Jordan Colombo
Download or read book Experimental Studies of Mercury Oxidation by Anaerobic Bacteria written by Matthew Jordan Colombo and published by . This book was released on 2013 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury is a toxic element with complex biogeochemistry. Bacteria influence mercury fate and transport in the environment by contributing to mercury sorption, reduction, and methylation. While these biogeochemical reactions have been well studied, the role of bacteria in mercury oxidation is poorly understood. In this dissertation, the oxidation of elemental mercury by anaerobic bacteria is documented in detail. The oxidation and methylation of elemental mercury by Desulfovibrio desulfuricans ND132 is described in Chapter 2. Bulk chemical analyses, derivatization reactions, and X-ray absorption spectroscopy showed that D. desulfuricans ND132 oxidized elemental mercury to divalent mercury and produced methylmercury when provided with elemental mercury as its sole mercury source. X-ray absorption spectroscopy demonstrated that the majority of cell-associated mercury was oxidized and covalently bound to organic sulfur. This work reveals previously unrecognized mercury transformations by anaerobic bacteria that may be important in anoxic aquatic settings. Other phylogenetically and metabolically diverse anaerobic bacteria were then investigated for their mercury oxidation abilities in Chapter 3. Geothrix fermentans H5, Shewanella oneidensis MR-1, and Cupriavidus metallidurans AE104 all oxidized elemental mercury to divalent mercury. Heat-inactivation of the cells did not diminish mercury oxidation ability, indicating that the bacteria do not have to be metabolically active to oxidize mercury. X-ray absorption spectroscopy also revealed that oxidized mercury was bound to cellular thiol groups. The results of this study suggest that mercury oxidation may be widespread among bacteria and be mediated by a passive cellular mechanism. Chapter 4 presents preliminary data demonstrating the fractionation of mercury stable isotopes during microbial mercury oxidation, in which the light isotopes preferentially accumulate in the oxidized product. Fractionation appeared to be mass dependent since no odd isotope anomalies or deviations from theoretical fractionation laws were observed. The data, considered in light of past experimental and theoretical work, suggests that isotope fractionation was the result of a kinetic isotope effect. This study provides initial insight into isotope fractionation during mercury oxidation and guides future efforts to detect this reaction in the environment.
Book Synopsis Fundamentals of Mercury Oxidation in Flue Gas by : Joseph Helble
Download or read book Fundamentals of Mercury Oxidation in Flue Gas written by Joseph Helble and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. This report summarizes Year 3 results for the experimental and modeling tasks. Experiments have been completed on the effects of chlorine. However, the experiments with sulfur dioxide and NO, in the presence of water, suggest that the wet-chemistry analysis system, namely the impingers, is possibly giving erroneous results. Future work will investigate this further and determine the role of reactions in the impingers on the oxidation results. The solid-phase experiments have not been completed and it is anticipated that only preliminary work will be accomplished during this study.
Book Synopsis Kinetic Modeling of Mercury Desorption and Adsorption on Fixed-bed Sorbents by : Youngkil Lee
Download or read book Kinetic Modeling of Mercury Desorption and Adsorption on Fixed-bed Sorbents written by Youngkil Lee and published by . This book was released on 1999 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling of Adsorption and Desorption of Mercury on Sorbents in a Fixed Bed Absorber by : Feng Guo
Download or read book Modeling of Adsorption and Desorption of Mercury on Sorbents in a Fixed Bed Absorber written by Feng Guo and published by . This book was released on 1997 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Gas-phase Mercury Oxidation by : Paula Andrea Buitrago
Download or read book Gas-phase Mercury Oxidation written by Paula Andrea Buitrago and published by . This book was released on 2011 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamental Understanding of Mercury Removal from Coal Combustion by : Erdem Sasmaz
Download or read book Fundamental Understanding of Mercury Removal from Coal Combustion written by Erdem Sasmaz and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coal-fired power plants are a major anthropogenic source of worldwide mercury (Hg) emissions. Since mercury is considered to be one of the most toxic metals found in the environment, Hg emissions from coal-fired power plants is of major environmental concern. Mercury in coal is vaporized into its gaseous elemental form throughout the coal combustion process. Elemental Hg can be oxidized in subsequent reactions with other gaseous components (homogeneous) and solid materials (heterogeneous) in coal-fired flue gases. While oxidized Hg in coal-fired flue gases is readily controlled by its adsorption onto fly ash and/or its dissolution into existing solution-based sulfur dioxide (SO2) scrubbers, elemental Hg is not controlled. The extent of elemental Hg formed during coal combustion is difficult to predict since it is dependent on the type of coal burned, combustion conditions, and existing control technologies installed. Therefore, it is important to understand heterogeneous Hg reaction mechanisms to predict the speciation of Hg emissions from coal-fired power plants to design and effectively determine the best applicable control technologies. In this work, theoretical and experimental investigations have been performed to investigate the adsorption and in some cases the oxidation, of Hg on solid surfaces, e.g., calcium oxide (CaO), noble metals and activated carbon (AC). The objective of this research is to identify potential materials that can be used as multi-pollutant sorbents in power plants by carrying out both high-level density functional theory (DFT) electronic structure calculations and experiments to understand heterogeneous chemical pathways of Hg. This research uses a fundamental science-based approach to understand the environmental problems caused by coal-fired energy production and provides solutions to the power generation industry for emissions reductions. Understanding the mechanism associated with Hg and SO2 adsorption on CaO will help to optimize the conditions or material to limit Hg emissions from the flue gas desulfurization process. Plane-wave DFT calculations were used to investigate the binding mechanism of Hg species and SO2 on the CaO(100) surface. The binding strengths on the high-symmetry CaO adsorption sites have been investigated for elemental Hg, SO2, mercury chlorides (HgCl and HgCl2) and mercuric oxide (HgO). It has been discovered that HgCl, HgCl2, and SO2 chemisorb on the CaO(100) surface at 0.125 ML coverage. Binding energies of elemental Hg are minimal indicating a physisorption mechanism. Noble metals such as palladium (Pd), gold (Au), silver (Ag), and copper (Cu) have been proposed to capture elemental Hg. Plane-wave DFT calculations have been carried out to investigate the mercury interactions with Pd binary alloys and overlays in addition to pure Pd, Au, Ag, and Cu surfaces. It has been determined that Pd has the highest mercury binding energy in comparison to other noble metals. In addition, Pd is found to be the primary surface atom responsible for increasing the adsorption of Hg with the surface in both Pd binary alloys and overlays. Deposition of Pd overlays on Au and Ag has been found to enhance the reactivity of the surface by shifting the d-states of surface atoms up in energy. The possible binding mechanisms of elemental Hg onto virgin, brominated and sulfonated AC fiber and brominated powder AC sorbents have been investigated through packed-bed experiments in a stream of air and simulated flue gas conditions, including SO2, hydrogen chloride (HCl), nitrogen oxide (NO) nitrogen dioxide (NO2). A combination of spectroscopy and plane-wave DFT calculations was used to characterize the sorption process. X-ray photoelectron spectroscopy (XPS) and x-ray absorption fine structure (XAFS) spectroscopy were used to analyze the surface and bulk chemical compositions of brominated AC sorbents reacted with Hg0. Through XPS surface characterization studies it was found that Hg adsorption is primarily associated with halogens on the surface. Elemental Hg is oxidized on AC surfaces and the oxidation state of adsorbed Hg is found to be Hg2+. Though plane-wave DFT and density of states (DOS) calculations indicate that Hg is more stable when it is bound to the edge carbon atom interacting with a single bromine bound atop of Hg, a model that includes an interaction between the Hg and an additional Br atom matches best with experimental data obtained from extended x-ray absorption fine structure (EXAFS) spectroscopy. The flue gas species such as HCl and bromine (Br2) enhance the Hg adsorption, while SO2 is found to decrease the Hg adsorption significantly by poisoning the active sites on the AC surface. The AC sorbents represent the most market-ready technology for Hg capture and therefore have been investigated by both theory and experiment in this work. Future work will include similar characterization and bench-scale experiments to test the metal-based materials for the sorbent and oxidation performance.
Book Synopsis Experimental and Kinetic Study of Mercury Adsorption on Various Activated Carbons in a Fixed Bed Adsorber by : Youngkil Lee
Download or read book Experimental and Kinetic Study of Mercury Adsorption on Various Activated Carbons in a Fixed Bed Adsorber written by Youngkil Lee and published by . This book was released on 2003 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
