Download or read book Computational and Experimental Studies of Mercury Homogeneous and Heterogeneous Oxidation in Flue Gases Derived from Coal fired Power Plants written by Junru Li and published by . This book was released on 2010 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational and Experimental Studies of Mercury Homogeneous and Heterogeneous Oxidation in Flue Gases Derived Form Coal fired Power Plants written by Junru Li and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Mercury Control written by Evan J. Granite and published by John Wiley & Sons. This book was released on 2014-09-17 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 Fundamentals of Mercury Oxidation in Flue Gas written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project was to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involved both experimental and modeling efforts. The team was comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective was to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters studied include HCl, NO(subscript x), and SO2 concentrations, ash constituents, and temperature. The results suggested that homogeneous mercury oxidation is below 10% which is not consistent with previous data of others and work which was completed early in this research program. Previous data showed oxidation above 10% and up to 100%. However, the previous data are suspect due to apparent oxidation occurring within the sampling system where hypochlorite ion forms in the KCl impinger, which in turn oxidized mercury. Initial tests with entrained iron oxide particles injected into a flame reactor suggest that iron present on fly ash particle surfaces can promote heterogeneous oxidation of mercury in the presence of HCl under entrained flow conditions. Using the data generated above, with homogeneous reactions accounting for less than 10% of the oxidation, comparisons were made to pilot- and full-scale data. The results suggest that heterogeneous reactions, as with the case of iron oxide, and adsorption on solid carbon must be taking place in the full-scale system. Modeling of mercury oxidation using parameters from the literature was conducted to further study the contribution of homogeneous pathways to Hg oxidation in coal combustion systems. Calculations from the literature used rate parameters developed in different studies, in some cases using transition state theory with a range of approaches and basis sets, and in other cases using empirical approaches. To address this, rate constants for the entire 8-step homogeneous Hg oxidation sequence were developed using an internally consistent transition state approach. These rate constants when combined with the appropriate sub-mechanisms produced lower estimates of the overall extent of homogeneous oxidation, further suggesting that heterogeneous pathways play an important role in Hg oxidation in coal-fired systems.

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.

Download or read book Mercury Speciation in Coal Fired Power Plant Flue Gas Experimental Studies and Model Development written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall goal of the project was to obtain a fundamental understanding of the catalytic reactions that are promoted by solid surfaces present in coal combustion systems and develop a mathematical model that described key phenomena responsible for the fate of mercury in coal-combustion systems. This objective was achieved by carefully combining laboratory studies under realistic process conditions using simulated flue gas with mathematical modeling efforts. Laboratory-scale studies were performed to understand the fundamental aspects of chemical reactions between flue gas constituents and solid surfaces present in the fly ash and their impact on mercury speciation. Process models were developed to account for heterogeneous reactions because of the presence of fly ash as well as the deliberate addition of particles to promote Hg oxidation and adsorption. Quantum modeling was used to obtain estimates of the kinetics of heterogeneous reactions. Based on the initial findings of this study, additional work was performed to ascertain the potential of using inexpensive inorganic sorbents to control mercury emissions from coal-fired power plants without adverse impact on the salability fly ash, which is one of the major drawbacks of current control technologies based on activated carbon.

Download or read book Mercury Emission and its Control in Chinese Coal Fired Power Plants written by Jinsong Zhou and published by Springer. This book was released on 2015-01-13 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Mercury Emission and its Control in Chinese Coal-Fired Power Plants" focuses on investigating mercury emissions samplings and measurement in Chinese coal-fired power plants, mercury emission estimations and future trends, mercury speciation transformation during coal combustion, mercury control and mercury stability in byproducts. The book not only introduces mercury emissions from actual coal-fired power plants, but also presents studies on the mechanism of mercury emission and its control. This is a valuable reference for engineering thermal physicists, thermal engineers, and chemical engineers. Jinsong Zhou, Zhongyang Luo, and Mengxiang Fang are Professors in the College of Mechanical and Energy Engineering, Zhejiang University, China. Yanqun Zhu is Associate Professor in the College of Mechanical and Energy Engineering, Zhejiang University, China.

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:

Download or read book Mercury Reaction Chemistry in Combustion Flue Gases from Experiments and Theory written by Bihter Padak and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions from coal combustion processes constitute a significant amount of the elemental mercury released into the atmosphere today. Coal-fired power plants in the United States, with the capacity of just over 300GW, are the greatest anthropogenic source of mercury emissions. Mercury exists in coal combustion flue gas in a variety of forms depending on the coal type and combustion conditions; i.e., elemental, oxidized and particulate. Particulate mercury in the flue gas can be removed using air pollution control devices such as electrostatic precipitators and fabric filters. Oxidized mercury is easily captured by wet flue gas desulfurization scrubbers, while gaseous elemental mercury passes through the scrubbers readily. Activated carbon, when injected into the gas stream of coal-fired boilers, is effective in capturing both elemental and oxidized mercury through adsorption processes. However, the mechanism by which mercury adsorbs on activated carbon is not exactly known and its understanding is crucial to the design and fabrication of effective capture technologies for mercury. The objective of the current study is to apply theoretical-based cluster modeling to examine the possible binding mechanism of mercury on activated carbon. The effects of activated carbon's different surface functional groups and halogens on elemental mercury adsorption have been examined. Also, a thermodynamic approach is followed to examine the binding mechanism of mercury and its oxidized species such as HgCl and HgCl2 on a simulated carbon surface with and without Cl. Energies of different possible surface complexes and possible products are compared and dominant pathways are determined relatively. Since different methods are employed to capture varying forms of mercury, understanding mercury speciation during combustion and how the transformations occur between different forms is essential to developing an effective control mechanism for removing mercury from flue gas. In this study, homogeneous oxidation of mercury via chlorine is examined experimentally in a simulated flue gas environment. Mercury and chlorine are introduced into a laminar premixed methane-air flame. Cooled flue gas is sampled and sent to a custom-built electron ionization quadrupole mass spectrometer specially designed for mercury measurement on the order of parts per billion (ppb) in flue gas. The use of a mass spectrometer allows for distinguishing between the different forms of oxidized mercury (Hg+, Hg+2). By directly measuring mercury species accurately, one can determine the actual extent of mercury oxidation in the flue gas, which will aid in further developing mercury control technologies.

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 21st European Symposium on Computer Aided Process Engineering written by and published by Elsevier. This book was released on 2011-06-10 with total page 2086 pages. Available in PDF, EPUB and Kindle. Book excerpt: The European Symposium on Computer Aided Process Engineering (ESCAPE) series presents the latest innovations and achievements of leading professionals from the industrial and academic communities. The ESCAPE series serves as a forum for engineers, scientists, researchers, managers and students to present and discuss progress being made in the area of computer aided process engineering (CAPE). European industries large and small are bringing innovations into our lives, whether in the form of new technologies to address environmental problems, new products to make our homes more comfortable and energy efficient or new therapies to improve the health and well being of European citizens. Moreover, the European Industry needs to undertake research and technological initiatives in response to humanity's "Grand Challenges," described in the declaration of Lund, namely, Global Warming, Tightening Supplies of Energy, Water and Food, Ageing Societies, Public Health, Pandemics and Security. Thus, the Technical Theme of ESCAPE 21 will be "Process Systems Approaches for Addressing Grand Challenges in Energy, Environment, Health, Bioprocessing & Nanotechnologies."

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.

Download or read book Homogeneous and Heterogeneous Oxidation of Gaseous Elemental Mercury written by Graydon Snider and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury is an atmospheric global pollutant with complex cycling behavior. Two-thirds of the mercury present in our atmosphere is anthropogenic in origin. Chemical oxidation of gaseous elemental mercury governs the deposition rate of mercury over most lakes, land, and oceans. A major uncertainty comes from the effect of atmospheric surfaces such as aerosols. Much research is devoted to mercury capture technologies to be used in coal fire power plants, which are the major source of anthropogenic emissions.This thesis is a report on oxidation kinetics and mechanistic studies relevant to mercury-scavenging reactions. It provides an overview of the mechanisms of mercury oxidation by ozone, nitrogen dioxide, and titanium dioxide (exposed to ultra-violet light). The role of surfaces was quantified, as appropriate for each system. Crossover effects between gaseous co-pollutants (e.g. CO, SO2) and surfaces (SiO2, TiO2) are discussed. Rate constants were measured for each...

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 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 2009 with total page 51 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 150°C. 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.