Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Oxidation Of Mercury In Products Of Coal Combustion
Download Oxidation Of Mercury In Products Of Coal Combustion full books in PDF, epub, and Kindle. Read online Oxidation Of Mercury In Products Of Coal Combustion ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Oxidation of Mercury in Products of Coal Combustion by :
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 (
Book Synopsis Mercury Control by : Evan J. Granite
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.
Book Synopsis Coal Fired Flue Gas Mercury Emission Controls by : Jiang Wu
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.
Book Synopsis Mercury Emission Behavior During Isolated Coal Particle Combustion by : Madhu Babu Puchakayala
Download or read book Mercury Emission Behavior During Isolated Coal Particle Combustion written by Madhu Babu Puchakayala and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Of all the trace elements emitted during coal combustion, mercury is most problematic. Mercury from the atmosphere enters into oceanic and terrestrial waters. Part of the inorganic Hg in water is converted into organic Hg (CH3Hg), which is toxic and bioaccumulates in human and animal tissue. The largest source of human-caused mercury air emissions in the U.S is from combustion coal, a dominant fuel used for power generation. The Hg emitted from plants primarily occurs in two forms: elemental Hg and oxidized Hg (Hg2). The coal chlorine content and ash composition, gas temperature, residence time and presence of different gases will decide the speciation of Hg into Hg0 and Hg2. For Wyoming coal the concentrations of mercury and chlorine in coal are 120ppb and 140ppb. In order to understand the basic process of formulation of HgCl2 and Hg0 a numerical model is developed in the current work to simulate in the detail i) heating ii) transient pyrolysis of coal and evolution of mercury and chlorine, iii) gas phase oxidation iv) reaction chemistry of Hg and v) heterogeneous oxidation of carbon during isolated coal particle combustion. The model assumes that mercury and chlorine are released as a part of volatiles in the form of elemental mercury and HCl. Homogenous reaction are implemented for the oxidation of mercury. Heterogeneous Hg reactions are ignored. The model investigates the effect of different parameters on the extent of mercury oxidation; particle size, ambient temperature, volatile matter, blending coal with high chlorine coal and feedlot biomass etc, . Mercury oxidation is increased when the coal is blended with feedlot biomass and high chlorine coal and Hg % conversion to HgCl2 increased from 10% to 90% when 20% FB is blended with coal. The ambient temperature has a negative effect on mercury oxidation, an increase in ambient temperature resulted in a decrease in the mercury oxidation. The percentage of oxidized mercury increases from 9% to 50% when the chlorine concentration is increased from 100ppm to 1000ppm. When the temperature is decreased from 1950 K to 950 K, the percentage of mercury oxidized increased from 3% to 27%.
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 CHARACTERIZATION OF COAL COMBUSTION BY-PRODUCTS FOR THE RE-EVOLUTION OF MERCURY INTO ECOSYSTEMS. by :
Download or read book CHARACTERIZATION OF COAL COMBUSTION BY-PRODUCTS FOR THE RE-EVOLUTION OF MERCURY INTO ECOSYSTEMS. written by and published by . This book was released on 2005 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is concern that mercury (Hg) in coal combustion by-products might be emitted into the environment during processing to other products or after the disposal/landfill of these by-products. This perception may limit the opportunities to use coal combustion by-products in recycle/reuse applications and may result in additional, costly disposal regulations. In this program, CONSOL conducted a comprehensive sampling and analytical program to include ash, flue gas desulfurization (FGD) sludge, and coal combustion by-products. This work is necessary to help identify potential problems and solutions important to energy production from fossil fuels. The program objective was to evaluate the potential for mercury emissions by leaching or volatilization, to determine if mercury enters the water surrounding an active FGD disposal site and an active fly ash slurry impoundment site, and to provide data that will allow a scientific assessment of the issue. Toxicity Characteristic Leaching Procedure (TCLP) test results showed that mercury did not leach from coal, bottom ash, fly ash, spray dryer/fabric filter ash or forced oxidation gypsum (FOG) in amounts leading to concentrations greater than the detection limit of the TCLP method (1.0 ng/mL). Mercury was detected at very low concentrations in acidic leachates from all of the fixated and more than half of the unfixated FGD sludge samples, and one of the synthetic aggregate samples. Mercury was not detected in leachates from any sample when deionized water (DI water) was the leaching solution. Mercury did not leach from electrostatic precipitator (ESP) fly ash samples collected during activated carbon injection for mercury control in amounts greater than the detection limit of the TCLP method (1.0 ng/mL). Volatilization tests could not detect mercury loss from fly ash, spray dryer/fabric filter ash, unfixated FGD sludge, or forced oxidation gypsum; the mercury concentration of these samples all increased, possibly due to absorption from ambient surroundings. Mercury loss of 18-26% was detected after 3 and 6 months at 100 F and 140 F from samples of the fixated FGD sludge. Water samples were collected from existing ground water monitoring wells around an active FGD disposal site (8 wells) and an active fly ash slurry impoundment (14 wells). These were wells that the plants have installed to comply with ground water monitoring requirements of their permits. Mercury was not detected in any of the water samples collected from monitoring wells at either site. A literature review concluded that coal combustion byproducts can be disposed of in properly designed landfills that minimize the potentially negative impacts of water intrusion that carries dissolved organic matter (DOM). Dissolved organic matter and sulfate-reducing bacteria can promote the transformation of elemental or oxidized mercury into methyl mercury. The landfill should be properly designed and capped with clays or similar materials to minimize the wet-dry cycles that promote the release of methylmercury.
Book Synopsis Mercury Reaction Chemistry in Combustion Flue Gases from Experiments and Theory by : Bihter Padak
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.
Book Synopsis Fundamentals of Mercury Transformations in Coal Combustion Flue Gas by : Balaji Krishnakumar
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:
Book Synopsis OXIDATION OF MERCURY ACROSS SCR CATALYSTS IN COAL-FIRED POWER PLANTS BURNING LOW RANK FUELS. by : Constance Senior
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.
Book Synopsis OXIDATION OF MERCURY ACROSS SCR CATALYSTS IN COAL-FIRED POWER PLANTS BURING LOW RANK FUELS. by :
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.
Book Synopsis High Temperature Mercury Oxidation Kinetics Via Bromine Mechanisms by : Terumi Okano
Download or read book High Temperature Mercury Oxidation Kinetics Via Bromine Mechanisms written by Terumi Okano and published by . This book was released on 2009 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: As the foremost production of electricity in the United State comes from coal-fired plants, there is much more to learn on the topic of mercury which is a common component in coal. The speciation of mercury in the flue gas determines the best control technology for a given system. Because of the difficulty in measuring mercury at different stages of the process, it is practical to use mercury reaction kinetics to theoretically determine mercury speciation based upon coal composition, plant equipment and operating conditions. Elemental mercury cannot be captured in wet scrubbers; however, its oxidized forms can. Chlorine is a reasonable oxidizing agent and is naturally found in bituminous coal, but bromine is an even better oxidizing agent because of its larger size, it has stronger London dispersion force interactions with mercury. Bromine additive technologies have recently been implemented in several companies to enhance mercury oxidation. Because capture technologies are highly dependent upon the form of mercury that is present, investigations into their speciation are extremely important. Though there have been numerous efforts to study mercury compounds as relevant to atmospheric studies, there is little data currently available for mercury compounds found in combustion flue gases. It would be particularly beneficial to obtain kinetic rate constants at various high temperature and pressure conditions typical for a combustion system. Prevalent species of mercury containing bromine in coal combustion flue gases were studied using density functional theory (DFT) and a broad range of ab initio methods. Reaction enthalpies, equilibrium bond distances, and vibrational frequencies were all predicted using DFT as well as coupled cluster (CC) methods. All electronic calculations were carried out using the Gaussian03 or MOLPRO software programs. Kinetic predictions of three first-stage and three second-stage oxidation reactions involving the formation of oxidized mercury via bromine containing compounds are presented. Understanding the speciation of mercury in the flue gases of coal combustion is paramount in developing efficient technologies to ensure its capture.
Book Synopsis Effects of Fly Ash on the Oxidation of Mercury During Post-combustion Conditions by : Hongqun Yang
Download or read book Effects of Fly Ash on the Oxidation of Mercury During Post-combustion Conditions written by Hongqun Yang and published by . This book was released on 2002 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions from coal-fired power plants pose impact on human health. The emissions will be regulated in the near future. Mercury speciation in flue gas has an important effect on the efficiency of mercury emission control devices. This study focuses on the role of fly ash on the oxidation of Hg0 in bench-scale simulated flue gas environment and in laboratory-scale coal combustion flue gas environment. The effects of flue gas matrices, temperature, fly ash mineralogy and morphology on the oxidation of Hg0 are studied. Conclusions are drawn based on the testing results: *Mercury chemistry is very complex in flue gas. *The presence of fly ash is critical for heterogeneous Hg0 oxidation. *The flue gas components, including NO2, HC1, NO and SO2, have strong effects on the potential of whole fly ashes to oxidize Hg0. *Fly ash specific surface area appears to have a determining effect on Hg0 heterogeneous oxidation.
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 Fine Particle and Mercury Formation and Control During Coal Combustion by : Xiaofei Wang
Download or read book Fine Particle and Mercury Formation and Control During Coal Combustion written by Xiaofei Wang and published by . This book was released on 2014 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulverized coal combustion is widely used worldwide for the production of electricity. However, it is one of the primary emission sources of air pollutants, including particulate matter (fly ash) and mercury (Hg), into the atmosphere. This dissertation investigated three aspects of pollutant formation and control from the coal combustion process: (1) organic aerosol formation during coal combustion, (2) mercury removal during coal combustion by injection of Vanadium Pentoxide (V2O5), and (3) submicrometer particle formation during oxy-coal combustion. Part. 1. While the characterization and formation of the mineral matter component of aerosol during coal combustion has been well studied and understood, the characterization and fate of corresponding organic matter content was not examined in detail earlier. The first part of this dissertation studies the formation mechanism of organic aerosols during coal combustion. Pilot-scale experiments were conducted in a 1 MW coal combustor, and showed that black carbon aerosol formation was greatly enhanced by increasing the fuel-air equivalence ratio. However, organic carbon aerosol formation was lowered by increasing the fuel-air equivalence ratio, which was opposite to the trend of black carbon aerosol formation. This phenomenon indicates that the formation mechanism of organic carbon aerosol is different from black carbon (soot) aerosol. Detailed organic aerosol formation mechanisms have been studied in a laboratory-scale system. Aerosol mass spectrometry techniques were applied to characterize both coal combustion aerosols from a drop-tube coal combustor and coal pyrolysis products from a flat-flame coal pyrolyzer. The chemical composition of major species for both combustion organic aerosols and pyrolysis products are hydrocarbons, carboxylic acids and aromatic compounds. The similarities of the chemical compositions demonstrate that the products from coal pyrolysis, (the initial step of coal combustion), are the precursors of organic aerosols. More carboxylic acids and oxygenated organic compounds were found in the combustion aerosols, indicating that many pyrolysis products are oxidized before they are converting to organic aerosols. A strong correlation between inorganic and organic aerosol formation mechanisms has been found in this work, demonstrating that inorganic particles play a critical role as carriers of organic species. Sulfate species in inorganic aerosols play a particularly important role in organic aerosol formation. Enhanced organic aerosol formation during the combustion of high sulfur content coal has been observed for the first time. High resolution mass spectra analysis shows the presence of amine-like organics in the aerosols. The correlation between particulate sulfate and organics suggests that acidic sulfate particles may absorb basic amine-like organics, a major coal pyrolysis product, from the gas phase into the particle phase via acid-base neutralization reactions. Part. 2. Coal combustion is a major source of atmospheric mercury. High-temperature sorbent injection is an efficient method to capture metallic species during combustion. This part of the study examines the performance on Hg capture from pulverized coal combustion in a drop-tube furnace. V2O5 was tested as a sorbent and demonstrated good performance on elemental mercury capture, which results from the formation of ultrafine V2O5 particles during the combustion process. It is proposed that the ultrafine V2O5 particles catalyzed Hg0 oxidation on their large surfaces. Hg2+, the oxidation product, may condense on fly ash particle surfaces or on tubing surfaces, thereby being removed from the flue gas. Part. 3. Coal combustion is the largest single contributor to global anthropogenic CO2 emissions. Oxy-coal combustion replaces the air with oxygen and uses recycled flue gas (RFG) as a diluent, resulting in a higher concentration (>98%) of CO2 in the exhaust, which promotes more effective control, capture, and possible conversion of CO2. This part of the dissertation investigates the effects of recycling (up to recycle ratios of 60%) on submicrometer particle formation in a drop-tube furnace system. The recycled exhaust gas containing lower O2 concentration and higher CO2 concentration suppressed submicrometer particle formation. However, it was found that water vapor in recycled exhaust gas greatly enhanced the formation of submicrometer particles. The gas composition changes that result from exhaust-gas recycling significantly affected the size distribution of submicrometer particles at the exit of the combustor. Differences in the particle size distribution with and without the filtration of recycled exhaust gas were insignificant. The composition of the resultant particles in oxy-coal combustion and conventional coal-air combustion as determined by X-ray diffraction was similar.
Book Synopsis Evaluation of the Impact of Chlorine on Mercury Oxidation in a Pilot-scale Coal Combustor, the Effect of Coal Blending by : Shannon D. Serre
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.
Book Synopsis Coal Combustion Products (CCPs) by : Tom Robl
Download or read book Coal Combustion Products (CCPs) written by Tom Robl and published by Woodhead Publishing. This book was released on 2017-04-29 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coal Combustion Products (CCPs): Their Nature, Utilization and Beneficiation is a valuable resource for engineers and scientists from the coal, cement, concrete, and construction industries seeking an in-depth guide to the characteristics, utilization, beneficiation, and environmental impacts of coal combustion by-products. Researchers in universities working in this area will also find much to expand their knowledge. The book provides a detailed overview of the different waste materials produced during power generation from coal, exploring their nature, beneficiation techniques, applications, and environmental impacts. Strong focus is placed on coal fly ash, bottom ash, and flue gas desulfurization materials, and their employment in cement, concrete, gypsum products, aggregates, road construction, geotechnics, and agriculture, among other products and industries. Part 1 focuses on the nature of coal ashes, with chapters on their origin, generation, and storage, both in ponds and landfill. The coal combustion by-products produced as a result of clean coal technologies are the focus of the final chapter in the section. The next group of chapters in Part 2 considers the utilization of different waste materials, including the key products coal fly ash, bottom ash, and flue gas desulfurization materials. This is followed by a contribution reviewing the latest research into innovative and advanced uses for coal ash. After an introduction to ash quality problems and quality monitoring, Part 3 concentrates on the essential area of by-product beneficiation techniques, in other words how to maximize the quality of materials for the end user. Topics covered include separation methods, thermal processing, and chemical passivation. The final section of the book addresses environmental issues, including the use of coal combustion by-products in green construction materials and the essential health and safety considerations associated with their use. An essential reference on the nature, reactivity, beneficiation, potential and environmental risks of coal-combustion by-products Contains an in-depth review of the origin and geochemistry of coal ash Explores the utilization of coal combustion by-products as supplementary cementitious materials to reduce the anthropomorphic greenhouse gas emissions associated with the use of ordinary Portland cement concrete Describes the essential area of the toxicology of coal combustion by-products
Book Synopsis The Homogeneus Forcing of Mercury Oxidation to Provide Low-Cost Capture by :
Download or read book The Homogeneus Forcing of Mercury Oxidation to Provide Low-Cost Capture written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace amounts of mercury are found in all coals. During combustion, or during thermal treatment in advanced coal processes, this mercury is vaporized and can be released to the atmosphere with the ultimate combustion products. This has been a cause for concern for a number of years, and has resulted in a determination by the EPA to regulate and control these emissions. Present technology does not, however, provide inexpensive ways to capture or remove mercury. Mercury that exits the furnace in the oxidized form (HgCl2) is known to much more easily captured in existing pollution control equipment (e.g., wet scrubbers for SO2), principally due to its high solubility in water. Work funded by DOE has helped understand the chemical kinetic processes that lead to mercury oxidation in furnaces. The scenario is as follows. In the flame the mercury is quantitatively vaporized as elemental mercury. Also, the chlorine in the fuel is released as HCl. The direct reaction Hg+HCl is, however, far too slow to be of practical consequence in oxidation. The high temperature region does supports a small concentration of atomic chlorine. As the gases cool (either in the furnace convective passes, in the quench prior to cold gas cleanup, or within a sample probe), the decay in Cl atom is constrained by the slowness of the principal recombination reaction, Cl+Cl+M-->Cl2+M. This allows chlorine atom to hold a temporary, local superequilibrium concentration . Once the gases drop below about 550 C, the mercury equilibrium shifts to favor HgCl2 over Hg, and this superequilibrium chlorine atom promotes oxidation via the fast reactions Hg+Cl+M-->HgCl+M, HgCl+Cl+M-->HgCl2+M, and HgCl+Cl2-->HgCl2+Cl. Thus, the high temperature region provides the Cl needed for the reaction, while the quench region allows the Cl to persist and oxidize the mercury in the absence of decomposition reactions that would destroy the HgCl2. Promoting mercury oxidation is one means of getting moderate-efficiency, 'free' mercury capture when wet gas cleanup systems are already in place. The chemical kinetic model we developed to describe the oxidation process suggests that in fuel lean gases, the introduction of trace amounts of H2 within the quench region leads to higher Cl concentrations via chain branching. The amount of additive, and the temperature at the addition point are critical. We investigated this process in a high-temperature quartz flow reactor. The results do indicate a substantial amount of promotion of oxidation with the introduction of relatively small amounts of hydrogen at around 1000 K ((almost equal to)100 ppm relative to the furnace gas). In practical systems the source of this hydrogen is likely to be a small natural gas steam reformer. This would also produce CO, so co-injection of CO was also tested. The CO did not provide any additional promotion, and in some cases led to a reduction in oxidation. We also examined the influence of NO and SO2 on the promotion process. We did not see any influence under the conditions examined. The present results were for a 0.5 s, isothermal plug flow environment. The next step should be to determine the appropriate injection point for the hydrogen and the performance under realistic temperature quench conditions. This could be accomplished first by chemical kinetic modeling, and then by tunnel flow experiment.
