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Catalytic Oxidation And Heterogeneous Capture Of Elemental Gas Phase Mercury
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Book Synopsis Catalytic Oxidation and Heterogeneous Capture of Elemental Gas-phase Mercury by : Sandhya Eswaran
Download or read book Catalytic Oxidation and Heterogeneous Capture of Elemental Gas-phase Mercury written by Sandhya Eswaran and published by . This book was released on 2006 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability of three sorbents, activated carbon, char and mordenite, to adsorb mercury is determined using simulated flue gas containing 10-15 mu g/m3 of mercury, in a laboratory-scale, fixed-bed adsorption system. The adsorption performance of the three sorbents is compared by, adsorption rate, rather than the adsorption capacity. The effect of temperature, sorbent loading, mercury concentration and acid gases such as NO and SO2 on the adsorption rate is investigated and presented in this dissertation. The mercury adsorption rate is in the range of 3000 to 3900 ng/hr for all three sorbents and increases with temperature, mercury concentration and acid gas concentration. Temperature is the major factor affecting the mercury adsorption rate on activated carbon and char while the rate of mercury adsorption on the zeolite sorbent is more strongly affected by the mercury concentration in the flue gas stream.
Book Synopsis Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet FGD Systems by :
Download or read book Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet 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: This final report presents and discusses results from a mercury control process development project entitled ''Pilot Testing of Mercury Oxidation Catalysts for Upstream of Wet FGD Systems''. The objective of this project was to demonstrate at pilot scale a mercury control technology that uses solid honeycomb catalysts to promote the oxidation of elemental mercury in the flue gas from coal combustion. Oxidized mercury is removed in downstream wet flue gas desulfurization (FGD) absorbers and leaves with the FGD byproducts. The goal of the project was to achieve 90% oxidation of elemental mercury in the flue gas and 90% overall mercury capture with the downstream wet FGD system. The project was co-funded by EPRI and the U.S. Department of Energy's National Energy Technology Laboratory (DOE NETL) under Cooperative Agreement DE-FC26-01NT41185. Great River Energy (GRE) and City Public Service (now CPS Energy) of San Antonio were also project co-funders and provided host sites. URS Group, Inc. was the prime contractor. Longer-term pilot-scale tests were conducted at two sites to provide catalyst life data. GRE provided the first site, at their Coal Creek Station (CCS), which fires North Dakota lignite, and CPS Energy provided the second site, at their Spruce Plant, which fires Powder River Basin (PRB) coal. Mercury oxidation catalyst testing began at CCS in October 2002 and continued through the end of June 2004, representing nearly 21 months of catalyst operation. An important finding was that, even though the mercury oxidation catalyst pilot unit was installed downstream of a high-efficiency ESP, fly ash buildup began to plug flue gas flow through the horizontal catalyst cells. Sonic horns were installed in each catalyst compartment and appeared to limit fly ash buildup. A palladium-based catalyst showed initial elemental mercury oxidation percentages of 95% across the catalyst, declining to 67% after 21 months in service. A carbon-based catalyst began with almost 98% elemental mercury oxidation across the catalyst, but declined to 79% oxidation after nearly 13 months in service. The other two catalysts, an SCR-type catalyst (titanium/vanadium) and an experimental fly-ash-based catalyst, were significantly less active. The palladium-based and SCR-type catalysts were effectively regenerated at the end of the long-term test by flowing heated air through the catalyst overnight. The carbon-based catalyst was not observed to regenerate, and no regeneration tests were conducted on the fourth, fly-ash-based catalyst. Preliminary process economics were developed for the palladium and carbon-based catalysts for a scrubbed, North Dakota lignite application. As described above, the pilot-scale results showed the catalysts could not sustain 90% or greater oxidation of elemental mercury in the flue gas for a period of two years. Consequently, the economics were based on performance criteria in a later DOE NETL solicitation, which required candidate mercury control technologies to achieve at least a 55% increase in mercury capture for plants that fire lignite. These economics show that if the catalysts must be replaced every two years, the catalytic oxidation process can be 30 to 40% less costly than conventional (not chemically treated) activated carbon injection if the plant currently sells their fly ash and would lose those sales with carbon injection. If the plant does not sell their fly ash, activated carbon injection was estimated to be slightly less costly. There was little difference in the estimated cost for palladium versus the carbon-based catalysts. If the palladium-based catalyst can be regenerated to double its life to four years, catalytic oxidation process economics are greatly improved. With regeneration, the catalytic oxidation process shows over a 50% reduction in mercury control cost compared to conventional activated carbon injection for a case where the plant sells its fly ash. At Spruce Plant, mercury oxidation catalyst testing began in September 2003 and continued through the end of April 2005, interrupted only by a host unit outage in late February/early March 2005. With a baghouse upstream of the catalysts, sonic horns did not appear to be necessary and were never installed. Pressure drop across the four catalysts remained low. Catalyst activity for elemental mercury oxidation was difficult to evaluate at this site. It was found that the baghouse effectively oxidized elemental mercury in the flue gas, with the baghouse outlet flue gas averaging 81% mercury oxidation. This oxidation resulted in little elemental mercury remaining in the flue gas going to the oxidation catalyst pilot unit. In many instances, catalyst outlet elemental mercury concentrations were near detection limits for the measurement methods employed, so mercury oxidation percentages across the catalyst were uncertain.
Book Synopsis Oxidation of Elemental Mercury by Chlorine by :
Download or read book Oxidation of Elemental Mercury by Chlorine written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate oxidation rate constants of mercury gas are needed for determining its dispersion and lifetime in the atmosphere. They would also help in developing a technology for the control of mercury emissions from coal-fired power plants. However, it is difficult to establish the accurate rate constants primarily due to the fact that mercury easily adsorbs on solid surface and its reactions can be catalyzed by the surface. We have demonstrated a procedure that allows the determination of gas phase, surface-induced, and photo-induced contributions in the kinetic study of the oxidation of mercury by chlorine gas. The kinetics was studied using reactors with various surface to volume ratios. The effect of the surface and the photo irradiation on the reaction was taken into consideration. The pressure dependent study revealed that the gas phase oxidation was a three-body collision process. The third order rate constant was determined to be 7.5(±0.2) x 10−39 mL2 molecules−2s−1 with N2 as the third body at 297 ± 1 K. The surface induced reaction on quartz window was second order and the rate constant was 2.7 x 10−17 mL2 molecules−1 cm−2 sec. Meanwhile, the 253.7 nm photon employed for mercury detection was found to accelerate the reaction. The utilization efficiency of 253.7 nm photon for Hg° oxidation was 6.7 x 10−4 molecules photon−1 under the conditions employed in this study.
Book Synopsis Catalyst Additives to Enhance Mercury Oxidation and Capture by : Thomas K. Gale
Download or read book Catalyst Additives to Enhance Mercury Oxidation and Capture written by Thomas K. Gale and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis is the key fundamental ingredient to convert elemental mercury in coal-fired power stations into its oxidized forms that are more easily captured by sorbents, ESPs, baghouses, and wet scrubbers, whether the catalyst be unburned carbon (UBC) in the ash or vanadium pentoxide in SCR catalysts. This project has investigated several different types of catalysts that enhance mercury oxidation in several different ways. The stated objective of this project in the Statement of Objectives included testing duct-injection catalysts, catalyst-sorbent hybrids, and coated low-pressure-drop screens. Several different types of catalysts were considered for duct injection, including different forms of iron and carbon. Duct-injection catalysts would have to be inexpensive catalysts, as they would not be recycled. Iron and calcium had been shown to catalyze mercury oxidation in published bench-scale tests. However, as determined from results of an on-going EPRI/EPA project at Southern Research, while iron and calcium did catalyze mercury oxidation, the activity of these catalysts was orders of magnitude below that of carbon and had little impact in the short residence times available for duct-injected catalysts or catalyst-sorbent hybrids. In fact, the only catalyst found to be effective enough for duct injection was carbon, which is also used to capture mercury and remove it from the flue gas. It was discovered that carbon itself is an effective catalyst-sorbent hybrid. Bench-scale carbon-catalyst tests were conducted, to obtain kinetic rates of mercury adsorption (a key step in the catalytic oxidation of mercury by carbon) for different forms of carbon. All carbon types investigated behaved in a similar manner with respect to mercury sorption, including the effect of temperature and chlorine concentration. Activated carbon was more effective at adsorbing mercury than carbon black and unburned carbon (UBC), because their internal surface area of activated carbon was greater. Catalyst coating of low-pressure-drop screens was of particular interest as this project was being developed. However, it was discovered that URS was already heavily involved in the pursuit of this same technology, being funded by DOE, and reporting significant success. Hence, testing of SCR catalysts became a major focus of the project. Three different commercial SCR catalysts were examined for their ability to oxidize mercury in simulated flue-gas. Similar performance was observed from each of the three commercial catalysts, both in terms of mercury oxidation and SO{sub 3} generation. Ammonia injection hindered mercury oxidation at low HCl concentrations (i.e., {approx}2 ppmv), yet had little impact on mercury oxidation at higher HCl concentrations. On the other hand, SO{sub 2} oxidation was significantly reduced by the presence of ammonia at both low and high concentrations of HCl.
Book Synopsis Mercury Oxidation Via Catalytic Barrier Filters Phase II. by :
Download or read book Mercury Oxidation Via Catalytic Barrier Filters Phase II. written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.
Book Synopsis Mercury Oxidation Across the Selective Catalytic Reduction (SCR) Unit by : Ana Suarez Negreira
Download or read book Mercury Oxidation Across the Selective Catalytic Reduction (SCR) Unit written by Ana Suarez Negreira and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions from coal-fired power plants represent 32% of the total anthropogenic mercury emissions in the United States (60 tons in 2012, 2000 tons worldwide). In recent years, public concern has increased due to the long-term irreversible effects of mercury on the environment and human health. As a result, the U.S. Environmental Protection Agency (EPA) proposed in December 2011 the Mercury and Air Toxics Standards (MATS); which require U.S. natural gas and coal-fired power plants to install air pollution control devices to prevent 91% of the Hg present in flue gas from being released. Currently, there are several air pollution control devices designed to reduce Hg emissions in power plants and whose working principles depend on the nature of the mercury species. Mercury is present in the flue gas in three forms: elemental (Hg0), oxidized (Hg+2) and particulate (HgP). Oxidized Hg is highly soluble in aqueous solutions, as compared to the insoluble and nonreactive Hg0, thus allowing for the removal of the former by conventional air pollution control devices. As a matter of fact, the promotion of Hg0 oxidation along the path of the flue gas from the boiler to the stack is currently the best approach to remove it by using current emission control technologies. The catalytic oxidation of mercury can be obtained through specific Hg oxidation catalysts such as noble metals or as a co-benefit of existing control technologies such as the Selective Catalyst Reduction (SCR) unit for NOx reduction. The latter option would be particularly attractive due to the associated low economic investment, since 40% of electricity from coal sources is produced in power plants that are already equipped with SCR units. However, little is known about the fate of mercury across the SCR unit, since most of the research work has been devoted to their applicability for NOx reduction. Understanding which are the key factors controlling the oxidation of mercury and developing a detailed mechanism of Hg oxidation across the SCR unit is a primary objective of this dissertation. One of the main achievements of this work has been the integration of an atomic-scale model with bench-scale experiments to identify key factors in Hg oxidation as a co-benefit of the SCR unit. Widely employed materials in commercial SCR catalysts include titania-supported vanadium and tungsten oxides, i.e., V2O5-WO3-TiO2, which were therefore investigated in this study. Theoretical models were used to assess the role of each component, namely, the support (TiO2), the active phase (V2O5) and the promoters (WO3), on the activity of this catalyst towards Hg oxidation. These include both density functional theory and ab-initio thermodynamic calculations; the latter are applied to investigate the effects of temperature and flue gas composition (which is coal dependent) on the reactivity of the catalyst under realistic operating conditions. Active phase, support and structural promoter were incorporated progressively into the analysis, thereby modeling the SCR catalyst with an increased level of complexity. The DFT results show that the active phase, V2O5, alone is not reactive under flue gas conditions and that the presence of the support leads to an increase of its reactivity toward Hg oxidation, presumably due to the higher dispersion of the vanadia phase on the TiO2 surface. Particular focus was given to the interaction of water with the supported system, due the significant concentration of water vapor present in the flue gas (≈ 10%). It is shown that water interacts with the surface in either a molecular or dissociative fashion, depending on the water coverage, which is in turn temperature-dependent. Interestingly, a stabilization effect is observed at low water coverages, as the latter tends to dissociate on the surface, thus yielding a reconstructed surface with attached hydroxyl groups. Moreover, a dehydration process is observed that takes place with increasing temperature and that leads to a water-free surface above 390 K. The analysis of the reactivity of the supported vanadium oxide catalyst was completed by a study of the adsorption energies of gas species that likely play a role in Hg oxidation (i.e., Hg, HgCl, HCl and H2O). Hereby, it was observed that surfaces with high water coverage show higher reactivity towards HgCl (the gas specie with the highest adsorption energy) followed by HCl. The adsorption energies of Hg suggested a negligible interaction with the vanadia dimer. Ab initio thermodynamic calculations were carried out to take into account the effect of temperature and entropy loss on the adsorption energies of these species; based on these results, a mechanism to explain Hg oxidation to HgCl2 was proposed, which involves the adsorption of HCl and HgCl, following a Langmuir-Hinshelwood mechanism. As a final step in the theoretical analysis, the incorporation of WO3 into the model shows that these ternary systems (V2O5-WO3-TiO2) are even more reactive than the binary systems (V2O5-TiO2). First, the effect of the surface coverage was studied by comparing the reactivity of the low- and high-loading binary systems. This analysis indicated enhanced reactivity of the SCR catalyst toward HgCl, HCl and Hg, with increasing loadings of the active phase. The effect of the surface composition on the reactivity of the catalyst was estimated by comparing the reactivity of the binary monolayer systems (i.e., 100% V2O5-TiO2 or 100%WO3-TiO2) against ternary systems (V2O5-WO3-TiO2 with different V2O5/WO3 ratios). This study showed a higher reactivity of the ternary system, with the 75%V2O5-25%WO3-TiO2 system representing the optimal catalyst composition toward Hg oxidation. The theoretical studies were complemented by Hg oxidation experiments carried out in a lab-scale packed-bed reactor with the purpose of benchmarking some of the predictions of the computational work. The effects of flue gas composition, catalyst formulation, temperature and space velocity on the Hg oxidation efficiency of different SCR catalysts were examined under typical flue gas conditions. The effect of the catalyst composition on the activity toward Hg oxidation was analyzed by testing four different SCR catalysts: 4%V2O5-10%WO3-TiO2, 1%V2O5-10%WO3-TiO2, 1%V2O5-TiO2 and 10%WO3-TiO2). It was shown that the binary systems have a lower activity compared to the ternary systems, thus supporting the predictions from first-principles calculations described above. Through the kinetic analysis, parameters such as reaction orders and the apparent activation energy were derived. By using the power law equation, it was found that O2 is zeroth-order and Hg is first-order in terms of the Hg oxidation rate. For the case of HCl, the reaction order could not be estimated using such a simple equation, and a more complex equation is necessary to capture the complexities of the heterogeneous reaction pathway. The activation energy takes a value of about 40 kJ/mol and is in reasonable agreement with data from the literature. It is worth pointing out that the intrinsic difficulty of measuring very low Hg concentration (≈ 5 ppb) results in large uncertainties associated with relevant parameters such as oxidation efficiencies and reaction rates.
Book Synopsis Mercury Oxidation and Adsorption Over Cupric Chloride-based Catalysts and Sorbents for Mercury Emissions Control by : Xin Li
Download or read book Mercury Oxidation and Adsorption Over Cupric Chloride-based Catalysts and Sorbents for Mercury Emissions Control written by Xin Li and published by . This book was released on 2012 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions control is of great importance in environment protection as well as public health. Current mercury emissions control technologies are not well designed nor optimized, mainly due to the lack of fundamental understanding of adsorption and/or catalytic mechanisms and necessary kinetic modeling and reliable simulation data. This work aims to advance the fundamental mechanistic understanding of heterogeneous catalytic oxidation reaction and adsorption by using the reaction between Hg(0) vapor and CuCl2 and the subsequent adsorption of resultant oxidized mercury onto sorbents. XANES and EXAFS were used to determine mercury compounds formed on AC sorbents. The XANES study on raw and CuCl2-impregnated AC sorbents suggests that little or no elemental mercury is formed onto any spent sorbents and the chemisorption of Hg(0) vapor is very likely to be the dominant mechanism. HgCl2 is found to be a major oxidation reaction product when CuCl2 and HCl were impregnated onto raw AC regardless of the type of the carrier gas (i.e. N2 or O2). The adsorption isotherms of HgCl2 on DARCO-HG and CuCl2-impregnated AC were found to be of the Langmuir type. The kinetic adsorption constants were estimated by fitting the model simulation with experimental data. The breakthrough data from experiments are in good agreement with the calculation results from the modified kinetic model. The simulation results indicate that pore diffusion resistance significantly increases with an increase in sorbent particle size. HgCl2 adsorption removal performance was also predicted in an entrained flow system using a modified model. The CuCl2/[alpha]-Al2O3 catalyst possesses high activity for the oxidation of Hg(0) to Hg2+, with an excellent stability under the environment similar to the flue gas from coal-fired power plants. The CuCl2 crystallites formed onto [alpha]-Al2O3 were very stable up to 300oC, and undergo the thermal reduction process from Cu(II) to Cu(0) via Cu(I). In the absence of HCl and O2 gases, CuCl2 was found to follow a Mars-Maessen mechanism by consuming lattice chlorine of CuCl2 for Hg(0) oxidation and to be reduced to CuCl. In the presence of 10 ppmv HCl, 2,000 ppmv SO2, and 6% O2 gases, the CuCl2/[alpha]-Al2O3 sample works as an Hg(0) oxidation catalyst exhibiting>90% conversion with good resistance to SO2 at 140oC. The reduced CuCl was able to be re-chlorinated to CuCl2 under HCl and O2 gases by following the Deacon reaction. Multiple copper species were found to be formed when [gamma]-Al2O3 is used as a substrate as opposed to one Cu(II) species on [alpha]-Al2O3. The CuCl2/[gamma]-Al2O3 catalysts with low CuCl2 loading (
Book Synopsis 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 Introduction to Environmental Management by : Mary K. Theodore
Download or read book Introduction to Environmental Management written by Mary K. Theodore and published by CRC Press. This book was released on 2021-05-30 with total page 719 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written at a level that is accessible to students in all disciplines, Introduction to Environmental Management, Second Edition translates complex environmental issues into practical and understandable terms. The book provides students and practitioners an understanding of the regulations, pollutants, and waste management issues that can be applied in various related environmental fields and industries. This new edition is updated throughout and adds eleven new chapters, including coverage of water conservation, water toxins, measurement methods, desalination, industrial ecology, legal issues, and more. Features: Updated throughout and includes eleven all-new chapters Reviews the specialized literature on pollution prevention, sustainability, and the role of optimization in water treatment and related areas, as well as references for further reading Provides illustrative examples and case studies that complement the text throughout Includes ancillary exams and a solutions manual for adopting instructors This book serves as a complete teaching tool, offering a combination of insightful coverage, concise language, and convenient pedagogical features, and supplies practical guidance that will aid students and practitioners alike.
Book Synopsis The Forcing of Mercury Oxidation as a Means of Promoting Low-Cost Capture by : John C. Kramlich
Download or read book The Forcing of Mercury Oxidation as a Means of Promoting Low-Cost Capture written by John C. Kramlich and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace amounts of mercury are found in all coals. During combustion this mercury is vaporized and can be released to the atmosphere. 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 from flue gases. The mercury that exits the furnace in the oxidized form (HgCl{sub 2}) is known to much more easily captured in existing wet pollution control equipment (e.g., wet FGD for SO{sub 2}), principally due to its high solubility in water. Until recently, however, nobody knew what caused this oxidation, or how to promote it. Recent DOE-funded research in our group, along with work by others, has identified the gas phase mechanism responsible for this oxidation. 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 due to disassociation of HCl. 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 {yields} Cl{sub 2}+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 HgCl{sub 2} over Hg, and this superequilibrium chlorine atom promotes oxidation via the fast reactions Hg+Cl+M {yields} HgCl+M, HgCl+Cl+M {yields} HgCl{sub 2}+M, and HgCl+Cl{sub 2} {yields} HgCl{sub 2}+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 HgCl{sub 2}. Promoting mercury oxidation is one means of getting high-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 oxidation can be promoted by introducing trace amounts of H{sub 2} and/or CO within the quench region. The reaction of these fuels leads to free radicals that promote the selective conversion of HCl to Cl, which can then subsequently react with Hg. The work reported here from our Phase I Innovative Concept grant demonstrated this phenomenon, but it also showed that the process must be applied carefully to avoid promoting the recombination of Cl back to HCl. For example, addition of H{sub 2} at too high a temperature is predicted to actually decrease Cl concentrations via Cl+H{sub 2} {yields} HCl+H. At lower temperatures this reaction is slowed due to its activation energy. Thus, within the correct window, the process becomes selective for Cl promotion. Key parameters are the injection temperature of the promoter, the amount of the fuel added. A successful process based on this research will add a powerful tool to the mercury control arsenal. Presently, fractional oxidation in flue gases varies widely, but averages about 50%. The amounts of promoter needed to obtain quantitative oxidation are predicted to be small ({approx}50 ppm). The H{sub 2}/CO could be supplied by conventional natural gas reformer on site, and the low expected fuel concentration would require only a relatively trivial amount of natural gas, even for a large power plant. For example, a 600 MW{sub e} plant would require the order of only 1 MW thermal equivalent of natural gas. If the mercury in the stream approaching a FGD system is highly oxidized, then high captures could be achieved without any additional cost, even for fuels of low chlorine.
Book Synopsis Heterogeneous Uptake and Reactions of Atmospheric Gaseous Elemental Mercury and Its Application to Remediation Technologies by : Uday Kurien
Download or read book Heterogeneous Uptake and Reactions of Atmospheric Gaseous Elemental Mercury and Its Application to Remediation Technologies written by Uday Kurien and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Mercury (Hg) is a persistent global toxicant that is recognized as a priority contaminant by the United Nations Environment Program (UNEP). To combat the hazards associated with the environmental inputs of Hg, the Minamata treaty was signed by 128 countries in 2013. The treaty calls for a reduction in the anthropogenic release of Hg and for research to better understand Hg’s behaviour in the environment and atmosphere. This thesis addresses some of these challenges, by (1) identifying and characterizing potentially important gas phase and surface reactions of Hg (Theme 1) and (2) developing a proof-of-concept energy neutral technology to remove and recycle Hg from consumer electronics (Theme 2). The specific issues addressed within Theme 1 are: (1) Gaseous elemental mercury’s (Hg0(g)) uptake on the reactive components (iron(oxyhydr)oxide particles) of mineral dust and (2) particle surface mediated Hg0(g)-O3 reactions. Theme 2 addresses the development of an energy neutral technology for the recycling of Hg from Compact Fluorescent Lights (CFLs).In the first part of Theme 1, the uptake of Hg0(g) on iron (oxyhydr)oxides nanoparticles was investigated. Loss of gas phase Hg0(g) was observed when the iron (oxyhydr)oxides were irradiated with ultra violet and visible radiation (300 nm ≤ [lambda] ≤ 700 nm). Irradiation caused the rates of the uptake reactions to increase by up to 900-fold relative to dark reactions. Humidity was found to inhibit the uptake reaction. Possible mechanisms of the radiation enhanced uptake reactions and its inhibition by humidity are discussed. Adsorption isotherms for the visible radiation assisted uptake of Hg0(g) on [alpha]-Fe2O3 were evaluated and found to fit the Langmuir-Hinshelwood model. In the second part of Theme 1, the effect of [alpha]-Fe2O3 particles on the oxidation of Hg0(g) by O3 was investigated. Depending on the mass loading of the particles, the rates of the surface mediated oxidation reaction were found to be ~ 80 -2000-fold larger than those of the pure gas phase reaction, re-investigated in this study using particle free air. This evidence supports the longstanding belief that Hg0(g)-O3 oxidation kinetics are highly surface sensitive. The rates of the surface mediated reactions were found to be independent of O3 concentrations (1 – 40 ppm) and 0 % ≤ RH ≤ 75 %. At RH = 100 % the Hg0(g) loss profiles shifted from an exponential decay, typical of pseudo first order reactions, to a linear decay. The reaction rates were, however, still elevated relative to homogeneous reactions. Possible mechanisms of the surface mediated reaction and the effect of humidity are discussed.In Theme 2, we exploit the uptake of Hg0(g) on iron oxide surfaces to develop a laboratory scale energy neutral technology for the remediation of Hg0(g) from Compact Fluorescent Lights (CFLs). The application of this technology is intended to replace the presently employed high energy thermal desorption remediation techniques. Hg0(g) from CFLs was successfully trapped onto iron oxide nanoparticles (Fe3O4 and [alpha]-Fe2O3) of high crustal abundance, using batch and flow-through systems. Recovery (~ 40 % - 90 %) of Hg from the iron oxide nanoparticles and regeneration of the iron oxide nanoparticle surfaces were achieved via electrolysis in an aqueous solution of NaCl. The post-electrolysis iron oxide nanoparticles were reused to trap Hg0(g) in further remediation experiments. Even after 4 adsorption-electrolysis cycles, the iron oxides’ capacity to adsorb Hg0(g) did not diminish"--
Book Synopsis Homogeneous and Heterogeneous Oxidation of Gaseous Elemental Mercury by : Graydon Snider
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...
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 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 Emission and Control of Trace Elements from Coal-Derived Gas Streams by : Yongchun Zhao
Download or read book Emission and Control of Trace Elements from Coal-Derived Gas Streams written by Yongchun Zhao and published by Woodhead Publishing. This book was released on 2019-07-12 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emission and Control of Trace Elements from Coal-Derived Gas Streams presents an up-to-date and focused analysis on Trace element (TEs) emissions and control strategies during coal utilization. This book provides insights into how TE’s in coal are distributed from different coal-forming periods, coal ranks and coal-bearing regions. As the emission and control of TEs during coal utilization are a significant concern, this book introduces TEs in coal and pollution in an accessible way before discussing why they occur and how they are distributed during various stages of coal forming, also considering various regions and countries. Specific types of TEs in relation to partition in coal combustion, coal fires, gasification and coal feed furnace are then analyzed, providing the reader with practical knowledge to apply to their own research or projects. This book is an essential reference for energy engineers researching and working in coal technology, with a specific focus on emission control, as well as graduate students and researchers in energy engineering, environmental, thermal and chemical engineering who have an interest in trace element emission and control from coal utilization. Presents characteristics of TE emissions during coal utilization in laboratory-scale experiments, industrial furnaces and power plants Considers different legislation and case studies from various regions and countries Includes contributions from world renowned experts Presents a concise and focused analysis on TE emissions and control strategies
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 Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed Reactor by :
Download or read book Modeling and Experimental Studies of Mercury Oxidation and Adsorption in a Fixed-Bed Reactor written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents experimental and modeling mercury oxidation and adsorption data. Fixed-bed and single-particle models of mercury adsorption were developed. The experimental data were obtained with two reactors: a 300- W, methane-fired, tubular, quartz-lined reactor for studying homogeneous oxidation reactions and a fixed-bed reactor, also of quartz, for studying heterogeneous reactions. The latter was attached to the exit of the former to provide realistic combustion gases. The fixed-bed reactor contained one gram of coconut-shell carbon and remained at a temperature of 150oC. All methane, air, SO2, and halogen species were introduced through the burner to produce a radical pool representative of real combustion systems. A Tekran 2537A Analyzer coupled with a wet conditioning system provided speciated mercury concentrations. At 150°C and in the absence of HCl or HBr, the mercury uptake was about 20%. The addition of 50 ppm HCl caused complete capture of all elemental and oxidized mercury species. In the absence of halogens, SO2 increased the mercury adsorption efficiency to up to 30 percent. The extent of adsorption decreased with increasing SO2 concentration when halogens were present. Increasing the HCl concentration to 100 ppm lessened the effect of SO2. The fixed-bed model incorporates Langmuir adsorption kinetics and was developed to predict adsorption of elemental mercury and the effect of multiple flue gas components. This model neglects intraparticle diffusional resistances and is only applicable to pulverized carbon sorbents. It roughly describes experimental data from the literature. The current version includes the ability to account for competitive adsorption between mercury, SO2, and NO2. The single particle model simulates in-flight sorbent capture of elemental mercury. This model was developed to include Langmuir and Freundlich isotherms, rate equations, sorbent feed rate, and intraparticle diffusion. The Freundlich isotherm more accurately described in-flight mercury capture. Using these parameters, very little intraparticle diffusion was evident. Consistent with other data, smaller particles resulted in higher mercury uptake due to available surface area. Therefore, it is important to capture the particle size distribution in the model. At typical full-scale sorbent feed rates, the calculations underpredicted adsorption, suggesting that wall effects can account for as much as 50 percent of the removal, making it an important factor in entrained-mercury adsorption models.
