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Experimental And Kinetic Modeling Investigation Of Gas Phase Mercury Oxidation Reactions With Chlorine
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Book Synopsis Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine by : Andrew Rodger Fry
Download or read book Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine written by Andrew Rodger Fry and published by . This book was released on 2008 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Investigation and Kinetic Modeling of Homogeneous Mercury Oxidation by Halogens by : Brydger Cauch
Download or read book Experimental Investigation and Kinetic Modeling of Homogeneous Mercury Oxidation by Halogens written by Brydger Cauch and published by . This book was released on 2008 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Gas-phase Mercury Oxidation by : Paula Andrea Buitrago
Download or read book Gas-phase Mercury Oxidation written by Paula Andrea Buitrago and published by . This book was released on 2011 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals of Mercury Oxidation in Flue Gas by :
Download or read book Fundamentals of Mercury Oxidation in Flue Gas written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO(subscript x), and SO2 concentrations, ash constituents, and temperature. This report summarizes Year 2 results for the experimental and modeling tasks. Experiments in the mercury reactor are underway and interesting results suggested that a more comprehensive look at catalyzed surface reactions was needed. Therefore, much of the work has focused on the heterogeneous reactions. In addition, various chemical kinetic models have been explored in an attempt to explain some discrepancies between this modeling effort and others.
Book Synopsis Fundamentals of Mercury Oxidation in Flue Gas by : Joseph Helble
Download or read book Fundamentals of Mercury Oxidation in Flue Gas written by Joseph Helble and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. This report summarizes Year 3 results for the experimental and modeling tasks. Experiments have been completed on the effects of chlorine. However, the experiments with sulfur dioxide and NO, in the presence of water, suggest that the wet-chemistry analysis system, namely the impingers, is possibly giving erroneous results. Future work will investigate this further and determine the role of reactions in the impingers on the oxidation results. The solid-phase experiments have not been completed and it is anticipated that only preliminary work will be accomplished during this study.
Book Synopsis 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 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 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 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.
Book Synopsis Control of mercury emissions from coalfired electric utility boilers interim report including errata dated 32102 by :
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:
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 Kinetic Studies and Computational Modeling of Atomic Chlorine Reactions in the Gas Phase by : Ionut M. Alecu
Download or read book Kinetic Studies and Computational Modeling of Atomic Chlorine Reactions in the Gas Phase written by Ionut M. Alecu and published by . This book was released on 2009 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine by :
Download or read book The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bench-scale experiments were conducted in a quartz-lined, natural gas-fired reactor with the combustion air replaced with a blend of 27 mole percent oxygen, with the balance carbon dioxide. Quench rates of 210 and 440 K/s were tested. In the absence of sulfur dioxide, the oxy-firing environment caused a remarkable increase in oxidation of mercury by chlorine. At 400 ppm chlorine (as HCl equivalent), air-firing results in roughly 5 percent oxidation. At the same conditions with oxy-firing, oxidation levels are roughly 80 percent. Oxidation levels with bromine at 25 and 50 ppm (as HBr equivalent) ranged from 80 to 95 percent and were roughly the same for oxy- and air-firing conditions. Kinetic calculations of levels of oxidation at air- and oxy-conditions captured the essential features of the experimental results but have not revealed a mechanistic basis for the oxidative benefits of oxy-firing conditions. Mixtures of 25 ppm bromine and 100 and 400 ppm chlorine gave more than 90 percent oxidation. At all conditions, the effects of quench rate were not significant. The presence of 500 ppm SO2 caused a dramatic decline in the levels of oxidation at all oxy-fired conditions examined. This effect suggests that SO2 may be preventing oxidation in the gas phase or preventing oxidation in the wetconditioning system that was used in quantifying oxidized and elemental mercury concentrations. Similar effects of SO2 have been noted with air-firing. The addition of sodium thiosulfate to the hydroxide impingers that are part of wet conditioning systems may prevent liquid-phase oxidation from occurring.
Book Synopsis Kinetic Modeling of H2O2-enhanced Oxidation of Flue Gas Elemental Mercury from Coal-fired Utility Boilers by : Bela Kishore Deshpande
Download or read book Kinetic Modeling of H2O2-enhanced Oxidation of Flue Gas Elemental Mercury from Coal-fired Utility Boilers written by Bela Kishore Deshpande and published by . This book was released on 2008 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Homogeneous Forcing of Mercury Oxidation to Provide Low-Cost Capture by : John C. Kramlich
Download or read book The Homogeneous Forcing of Mercury Oxidation to Provide Low-Cost Capture written by John C. Kramlich and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxidized mercury formed in combustors (e.g., HgCl{sub 2}) is much more easily captured in existing pollution control equipment (e.g., wet scrubbers for SO{sub 2}) than elemental mercury. This is principally due to the high solubility of the oxidized form in water. Work over the last several years in our laboratory and elsewhere has identified the general outlines of the homogeneous chemistry of oxidation. The goal of the work reported here is to make use of this knowledge of the oxidation mechanism to devise simple and inexpensive ways to promote the oxidation. The hypothesis is that simple fuels such as hydrogen or CO can promote oxidation via the free radicals they generate during their decomposition. These free radicals then promote the formation of Cl from HCl via reactions such as OH+HCl {yields} H{sub 2}O+Cl. The Cl (and Cl{sub 2} derived from Cl recombination) are considered the principal oxidizing species. In our studies, mercury vapor is exposed to HCl under isothermal conditions in a gas containing N{sub 2}, O{sub 2}, and H{sub 2}O. The experiments systematically explore the influence of reaction temperature, HCl concentration, and H{sub 2}O concentration. These baseline conditions are then perturbed by the addition of varying amounts of H{sub 2}, CO, and H{sub 2}/CO added jointly. The following report presents the results of a literature review associated with the dissertation of the student supported by the program. This outlines the state-of-the-art in mercury behavior. It then describes the experimental facilities and the results of tests involving the promotion of the oxidation reaction by H{sub 2}, CO, and H{sub 2}/CO combinations. These results indicate a substantial enhancement of oxidation under isothermal conditions at 900-1000 K, while the additives inhibit oxidation at 1200 K. The next step is to determine whether the existing chemical kinetic models of mercury oxidation are capable of reproducing this behavior. These models can then be used to extrapolate the findings to nonisothermal conditions typical of boiler environments. This would provide guidance on where to inject the oxidation promoters in a practical boiler, and how much promoter is required.
Book Synopsis Mercury Emission and its Control in Chinese Coal-Fired Power Plants by : Jinsong Zhou
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.
