Download or read book OXIDATION OF MERCURY ACROSS SCR CATALYSTS IN COAL FIRED POWER PLANTS BURNING LOW RANK FUELS written by and published by . This book was released on 2004 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the fifth Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-03NT41728. The objective of this program is to measure the oxidation of mercury in flue gas across SCR catalyst in a coal-fired power plant burning low rank fuels using a slipstream reactor containing multiple commercial catalysts in parallel. The Electric Power Research Institute (EPRI) and Argillon GmbH are providing co-funding for this program. This program contains multiple tasks and good progress is being made on all fronts. During this quarter, the available data from laboratory, pilot and full-scale SCR units was reviewed, leading to hypotheses about the mechanism for mercury oxidation by SCR catalysts.

Download or read book OXIDATION OF MERCURY ACROSS SCR CATALYSTS IN COAL FIRED POWER PLANTS BURING LOW RANK FUELS written by and published by . This book was released on 2004 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the sixth Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-03NT41728. The objective of this program is to measure the oxidation of mercury in flue gas across SCR catalyst in a coal-fired power plant burning low rank fuels using a slipstream reactor containing multiple commercial catalysts in parallel. The Electric Power Research Institute (EPRI) and Argillon GmbH are providing co-funding for this program. This program contains multiple tasks and good progress is being made on all fronts. During this quarter, a review of the available data on mercury oxidation across SCR catalysts from small, laboratory-scale experiments, pilot-scale slipstream reactors and full-scale power plants was carried out. Data from small-scale reactors obtained with both simulated flue gas and actual coal combustion flue gas demonstrated the importance of temperature, ammonia, space velocity and chlorine on mercury oxidation across SCR catalyst. SCR catalysts are, under certain circumstances, capable of driving mercury speciation toward the gas-phase equilibrium values at SCR temperatures. Evidence suggests that mercury does not always reach equilibrium at the outlet. There may be other factors that become apparent as more data become available.

Download or read book OXIDATION OF MERCURY ACROSS SCR CATALYSTS IN COAL FIRED POWER PLANTS BURNING LOW RANK FUELS written by Constance Senior and published by . This book was released on 2003 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-03NT41728. The objective of this program is to measure the oxidation of mercury in flue gas across SCR catalyst in a coal-fired power plant burning low rank fuels using a slipstream reactor containing multiple commercial catalysts in parallel. The Electric Power Research Institute (EPRI) and Ceramics GmbH are providing co-funding for this program. This program contains multiple tasks and good progress is being made on all fronts. During this quarter, analysis of the coal, ash and mercury speciation data from the first test series was completed. Good agreement was shown between different methods of measuring mercury in the flue gas: Ontario Hydro, semi-continuous emission monitor (SCEM) and coal composition. There was a loss of total mercury across the commercial catalysts, but not across the blank monolith. The blank monolith showed no oxidation. The data from the first test series show the same trend in mercury oxidation as a function of space velocity that has been seen elsewhere. At space velocities in the range of 6,000-7,000 hr{sup -1} the blank monolith did not show any mercury oxidation, with or without ammonia present. Two of the commercial catalysts clearly showed an effect of ammonia. Two other commercial catalysts showed an effect of ammonia, although the error bars for the no-ammonia case are large. A test plan was written for the second test series and is being reviewed.

Download or read book Coal Fired Flue Gas Mercury Emission Controls written by Jiang Wu and published by Springer. This book was released on 2015-03-17 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury (Hg) is one of the most toxic heavy metals, harmful to both the environment and human health. Hg is released into the atmosphere from natural and anthropogenic sources and its emission control has caused much concern. This book introduces readers to Hg pollution from natural and anthropogenic sources and systematically describes coal-fired flue gas mercury emission control in industry, especially from coal-fired power stations. Mercury emission control theory and experimental research are demonstrated, including how elemental mercury is oxidized into oxidized mercury and the effect of flue gas contents on the mercury speciation transformation process. Mercury emission control methods, such as existing APCDs (air pollution control devices) at power stations, sorbent injection, additives in coal combustion and photo-catalytic methods are introduced in detail. Lab-scale, pilot-scale and full-scale experimental studies of sorbent injection conducted by the authors are presented systematically, helping researchers and engineers to understand how this approach reduces the mercury emissions in flue gas and to apply the methods in mercury emission control at coal-fired power stations. Readers will arrive at a comprehensive understanding of various mercury emission control methods that are suitable for industrial applications. The book is intended for scientists, researchers, engineers and graduate students in the fields of energy science and technology, environmental science and technology and chemical engineering.

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.

Download or read book Coal Gasification and Its Applications written by David A. Bell and published by William Andrew. This book was released on 2010-12-08 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Skyrocketing energy costs have spurred renewed interest in coal gasification. Currently available information on this subject needs to be updated, however, and focused on specific coals and end products. For example, carbon capture and sequestration, previously given little attention, now has a prominent role in coal conversion processes.This book approaches coal gasification and related technologies from a process engineering point of view, with topics chosen to aid the process engineer who is interested in a complete, coal-to-products system. It provides a perspective for engineers and scientists who analyze and improve components of coal conversion processes.The first topic describes the nature and availability of coal. Next, the fundamentals of gasification are described, followed by a description of gasification technologies and gas cleaning processes. The conversion of syngas to electricity, fuels and chemicals is then discussed. Finally, process economics are covered. Emphasis is given to the selection of gasification technology based on the type of coal fed to the gasifier and desired end product: E.g., lower temperature gasifiers produce substantial quantities of methane, which is undesirable in an ammonia synthesis feed. This book also reviews gasification kinetics which is informed by recent papers and process design studies by the US Department of Energy and other groups, and also largely ignored by other gasification books.• Approaches coal gasification and related technologies from a process engineering point of view, providing a perspective for engineers and scientists who analyze and improve components of coal conversion processes • Describes the fundamentals of gasification, gasification technologies, and gas cleaning processes • Emphasizes the importance of the coal types fed to the gasifier and desired end products • Covers gasification kinetics, which was largely ignored by other gasification books - Provides a perspective for engineers and scientists who analyze and improve components of the coal conversion processes - Describes the fundamentals of gasification, gasification technologies, and gas cleaning processes - Covers gasification kinetics, which was largely ignored by other gasification books

Download or read book Selective Catalytic Reduction Technology for the Control of Nitrogen Oxide Emissions from Coal Fired Boilers written by Gene Knight and published by DIANE Publishing. This book was released on 2008-08 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Clean Coal Technology Demo. Program (CCTDP) is an effort to demonstrate a new generation of innovative coal utilization processes in a series of facilities built across the country. These projects are carried out on a commercial scale to prove technical feasibility and provide the info. required for future applications. Projects have demonstrated technical options with the potential to meet the needs of energy markets while satisfying environ. requirements. Part of this program is the demo. of technologies designed to reduce emissions of oxides of nitrogen (NOx) from existing coal-fired utility boilers. This report summarizes the status of selective catalytic reduction (SCR) technology for the control of NOx emissions from high-sulfur, coal-fired boilers. Illus.

Download or read book Mercury Control written by Evan J. Granite and published by John Wiley & Sons. This book was released on 2015-01-20 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: This essential handbook and ready reference offers a detailed overview of the existing and currently researched technologies available for the control of mercury in coal-derived gas streams and that are viable for meeting the strict standards set by environmental protection agencies. Written by an internationally acclaimed author team from government agencies, academia and industry, it details US, EU, Asia-Pacific and other international perspectives, regulations and guidelines.

Download or read book Evaluation of the Impact of Chlorine on Mercury Oxidation in a Pilot scale Coal Combustor the Effect of Coal Blending written by Shannon D. Serre and published by . This book was released on 2009 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Coal-fired power plants are a major source of mercury (Hg) released into the environment and the utility industry is currently investigating options to reduce Hg emissions. One control option is to utilize existing pollution control equipment such as wet flue gas desulfurization (FGD) scrubbers. The split (speciation) between chemical forms of mercury (Hg) species has a strong influence on the control and environmental fate of Hg emissions from coal combustion. The high-temperature coal combustion process releases Hg in elemental form (Hg0). A significant fraction of the Hg0 can be subsequently oxidized in the low-temperature, post-combustion environment of a coal-fired boiler. Relative to Hg0, oxidized Hg (Hg2+) is more effectively removed by air pollution control systems (APCS). For example, the water-soluble Hg2+ is much more easily captured than insoluble Hg0 in FGD units. Selective catalytic reduction (SCR) technology widely applied for reducing NOX emissions from power plants also affects the speciation of Hg in the coal combustion flue gases. Recent full-scale field tests conducted in the U.S. showed increases in Hg oxidation across the SCR catalysts for plants firing bituminous coals with sulfur (S) content ranging from 1.0 to 3.9%. However, plants firing subbituminous Powder River Basin (PRB) coals which contains significantly lower chlorine (Cl) and sulfur (S) content and higher calcium (Ca) content than those of the bituminous coals, showed very little change in mercury speciation across the SCR reactors. A field study conducted by EPRI showed blending of PRB coal with a bituminous coal (60% PRB/40% bituminous) resulted in increased Hg2+ from 45% at the SCR inlet to 93% at the outlet. Coal blending appears to be a potentially cost effective approach for increasing Hg oxidation for PRB coal-fired SCR systems."--Abstract.

Download or read book Control of mercury emissions from coalfired electric utility boilers interim report including errata dated 32102 written by and published by DIANE Publishing. This book was released on with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Regenerated Catalyst for Mercury Speciation written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In March of 2005, U.S. Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR). Mercury from coal-fired power plants was to be reduced from the current 48 to 38 tons/yr by 2010 and then 15 tons/yr by 2018. It is expected that the first phase reduction of (almost equal to)21% will be achieved by cobenefits that will occur as a result of installing additional selective catalytic reduction (SCR) and flue gas desulfurization (FGD) systems to meet the new Clean Air Interstate Rule (CAIR). Detroit Edison (DTE) is installing SCR at all four units at its Monroe Station and will eventually install wet-FGD systems. As such, the Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and DTE have contracted with the Energy & Environmental Research Center (EERC) to determine the extent of mercury oxidation that occurs at Monroe Station. The EERC originally did mercury speciation sampling at Monroe Station in 2004 and then went back in 2005 to determine if any changes occurred as a result of catalyst aging. During the second test, in addition to measuring the mercury speciation at the inlet and outlet of the SCR, the EERC also completed sampling at a location between the catalyst layers. The results are shown in Table 1. In Table 1, the results show that (almost equal to)40% of the Hg was in oxidized form (Hg{sup 2+}) at the inlet and nearly 100% Hg{sup 2+} at the outlet. The results at the midpoint were between 40% and 100%. As part of their overall strategy to reduce SCR costs, utilities and SCR vendors are attempting to regenerate catalyst layers that have degenerated over time. If these regenerated catalysts are used, the question remains as to the effect this process will have on the ability of these catalysts to oxidize mercury as well as reduce NO(subscript x). The current project is designed to measure the Hg speciation across an SCR using a regenerated catalyst. The results were compared to previous results to determine what, if any, changes occurred. Two series of tests were completed: one early in the ozone season (July 2006) and the second near the end (September 2006). The goal of this project is to determine the effect SCR catalyst regeneration has on Hg speciation and emissions from combustion of a blend of eastern bituminous and Powder River Basin (PRB) coal at DTE's Monroe Station. Specific objectives include the following: (1) Compare the Hg speciation results at the inlet and outlet of the SCR. Determine the change in the concentration of oxidized Hg across the SCR. In addition, determine if the number of catalyst layers has any effect. (2) Compare results from previous testing to determine if there are changes in mercury speciation as a result of catalyst regeneration. (3) Determine the overall speciated Hg emissions (from a separate project funded by DTE).

Download or read book Evaluation of Mercury Emissions from Coal Fired Facilities with SCR and FGD Systems written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO(subscript x), and SO2 control technologies. It is expected that these data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the ninth in a series of topical reports, describes the results and analysis of mercury sampling performed on Unit 1 at Plant 7, a 566 MW unit burning a bituminous coal containing 3.6% sulfur. The unit is equipped with a SCR, ESP, and wet FGD to control NO(subscript x), particulate, and SO2 emissions, respectively. Four sampling tests were performed in August 2004 during ozone season with the SCR operating; flue gas mercury speciation and concentrations were determined at the SCR inlet, SCR outlet, air heater outlet (ESP inlet), ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Three sampling tests were also performed in November 2004 during non-ozone season with the SCR bypassed; flue gas mercury speciation and concentrations were determined at the ESP outlet (FGD inlet), and at the stack (FGD outlet). Process samples for material balances were collected during the flue gas measurements. The results show that, at the point where the flue gas enters the FGD, a greater percentage of the mercury was in the oxidized form when the SCR was operating compared to when the SCR was bypassed (97% vs 91%). This higher level of oxidation resulted in higher mercury removals in the FGD because the FGD removed 90-94% of the oxidized mercury in both cases. Total coal-to-stack mercury removal was 86% with the SCR operating, and 73% with the SCR bypassed. The average mercury mass balance closure was 81% during the ozone season tests and 87% during the non-ozone season tests.

Download or read book Evaluation of Mercury Emissions from Coal Fired Facilities with SCR and FGD Systems written by J. E. Locke and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: CONSOL Energy Inc., Research & Development (CONSOL), with support from the U.S. Department of Energy, National Energy Technology Laboratory (DOE) and the Electric Power Research Institute (EPRI), is evaluating the effects of selective catalytic reduction (SCR) on mercury (Hg) capture in coal-fired plants equipped with an electrostatic precipitator (ESP)--wet flue gas desulfurization (FGD) combination or a spray dyer absorber--fabric filter (SDA-FF) combination. In this program CONSOL is determining mercury speciation and removal at 10 coal-fired facilities. The principal purpose of this work is to develop a better understanding of the potential mercury removal ''co-benefits'' achieved by NO{sub x}, and SO{sub 2} control technologies. It is expected that this data will provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. Ultimately, this insight could help to design and operate SCR and FGD systems to maximize mercury removal. The objectives are (1) to evaluate the effect of SCR on mercury capture in the ESP-FGD and SDA-FF combinations at coal-fired power plants, (2) evaluate the effect of SCR catalyst degradation on mercury capture; (3) evaluate the effect of low load operation on mercury capture in an SCR-FGD system, and (4) collect data that could provide the basis for fundamental scientific insights into the nature of mercury chemistry in flue gas, the catalytic effect of SCR systems on mercury speciation and the efficacy of different FGD technologies for mercury capture. This document, the tenth in a series of topical reports, describes the results and analysis of mercury sampling performed on two 468 MW units burning bituminous coal containing 1.3-1.7% sulfur. Unit 2 is equipped with an SCR, ESP, and wet FGD to control NO{sub x}, particulate, and SO{sub 2} emissions, respectively. Unit 1 is similar to Unit 2, except that Unit 1 has no SCR for NOx control. Four sampling tests were performed on both units in January 2005; flue gas mercury speciation and concentrations were determined at the economizer outlet, air heater outlet (ESP inlet), ESP outlet (FGD inlet), and at the stack (FGD outlet) using the Ontario Hydro method. Process samples for material balances were collected with the flue gas measurements. The results show that the SCR increased the oxidation of the mercury at the air heater outlet. At the exit of the air heater, a greater percentage of the mercury was in the oxidized and particulate forms on the unit equipped with an SCR compared to the unit without an SCR (97.4% vs 91%). This higher level of oxidation resulted in higher mercury removals in the scrubber. Total mercury removal averaged 97% on the unit with the SCR, and 87% on the unit without the SCR. The average mercury mass balance closure was 84% on Unit 1 and 103% on Unit 2.

Download or read book Oxidation of Mercury in Products of Coal Combustion written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Laboratory measurements of mercury oxidation during selective catalytic reduction (SCR) of nitric oxide, simulation of pilot-scale measurements of mercury oxidation and adsorption by unburned carbon and fly ash, and synthesis of new materials for simultaneous oxidation and adsorption of mercury, were performed in support of the development of technology for control of mercury emissions from coal-fired boilers and furnaces. Conversion of gas-phase mercury from the elemental state to water-soluble oxidized form (HgCl2) enables removal of mercury during wet flue gas desulfurization. The increase in mercury oxidation in a monolithic V2O5-WO3/TiO2 SCR catalyst with increasing HCl at low levels of HCl (

Download or read book Catalyst Additives to Enhance Mercury Oxidation and Capture written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Preliminary research has shown that SCR catalysts employed for nitrogen-oxide reduction can effectively oxidize mercury. This report discusses initial results from fundamental investigations into the behavior of mercury species in the presence of SCR catalysts at Southern Research Institute. The testing was performed at Southern Research's Catalyst Test Facility, a bench-scale reactor capable of simulating gas-phase reactions occurring in coal-fired utility pollution-control equipment. Three different SCR catalysts are currently being studied in this project--honeycomb-type, plate-type, and a hybrid-type catalyst. The catalysts were manufactured and supplied by Cormetech Inc., Hitachi America Ltd., and Haldor-Topsoe Inc., respectively. Parametric testing was performed to investigate the contribution of flue-gas chemistry on mercury oxidation via SCR catalysts. Methods and procedures for experimental testing continue to be developed to produce the highest quality mercury-oxidation data. During this past quarter, it was discovered that long periods (12 - 24 hours) are required to equilibrate the catalysts in the system. In addition, after the system has been equilibrated, operational changes to temperature, gas concentration, or flow rate shifts the equilibrium, and steady-state must be reestablished, which can require as much as twelve additional hours per condition change. In the last quarter of testing, it was shown that the inclusion of ammonia had a strong effect on the oxidation of mercury by SCR catalysts, both in the short-term (a transitional period of elemental and oxidized mercury off gassing) and the long-term (less steady-state mercury oxidation). All experiments so far have focused on testing the catalysts in a simulated Powder River Basin (PRB) flue-gas environment, which contains lower sulfur and chlorine than produced by other coals. In the next quarter, parametric testing will be expanded to include flue gases simulating power plants burning Midwestern and Eastern coals, which are higher in sulfur and chlorine. Also, the isolation of such gases as hydrogen chloride (HCl), ammonia (NH3), and sulfur trioxide (SO3) will be investigated. All of these efforts will be used to examine the kinetics of mercury oxidation across the SCR catalysts with respect to flue gas composition, temperature, and flow rate.

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.

Download or read book Fundamentals of Mercury Transformations in Coal Combustion Flue Gas written by Balaji Krishnakumar and published by . This book was released on 2008 with total page 798 pages. Available in PDF, EPUB and Kindle. Book excerpt: