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.
Download or read book Fundamentals of Mercury Oxidation in Flue Gas written by Joseph Helble and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NO{sub x}, and SO{sub 2} concentrations, ash constituents, and temperature. This report summarizes Year 3 results for the experimental and modeling tasks. Experiments have been completed on the effects of chlorine. However, the experiments with sulfur dioxide and NO, in the presence of water, suggest that the wet-chemistry analysis system, namely the impingers, is possibly giving erroneous results. Future work will investigate this further and determine the role of reactions in the impingers on the oxidation results. The solid-phase experiments have not been completed and it is anticipated that only preliminary work will be accomplished during this study.
Download or read book 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.
Download or read book Mercury as a Global Pollutant written by Donald B. Porcella and published by Springer. This book was released on 2014-08-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: ACKNOWLEDGEMENTS xiv PART I MERCURY AND HUMAN HEALTH B. WHEATLEY and S. PARADIS I Exposure of Canadian Aboriginal Peoples to Methylmercury 3-11 M. GIRARD and C. DUMONT I Exposure of James Bay Cree to Methylmercury during Pregnancy for the Years 1983-91 13-19 M. RICHARDSON, M. MITCHELL, S. COAD and R. RAPHAEL I Exposure to Mercury in Canada: A Multimedia Analysis 21-30 M. RICHARDSON, M. EGYED and D. J. CURRIE I Human Exposure to Mercury may Decrease as Acidic Deposition Increases 31-39 L. E. FLEMING, S. WATKINS, R. KADERMAN, B. LEVIN, D. R. AVYAR, M. BIZZIO, D. STEPHENS and J. A. BEAN I Mercury Exposure in Humans through Food Consumption from the Everglades of Florida 41-48 J. M. GEARHART, H. J. CLEWELL III, K. S. CRUMP, A. M. SHIPP and A. SILVERS I Pharmacokinetic Dose Estimates of Mercury in Children and Dose-Response Curves of Performance Tests in a Large Epidemiological Study 49-58 I. SKARE I Mass Balance and Systemic Uptake of Mercury Released from Dental Amalgam Fillings 59-67 J. DELLINGER, N. KMIECIK, S. GERSTENBERGER and H. NGU I Mercury Contamina tion of Fish in the Ojibwa Diet: I. Walleye Fillets and Skin-On versus Skin-Off Sampling 69-76 J. DELLINGER, L. MALEK and M. BEATTIE I Mercury Contamination of Fish in the Ojibwa Diet: II. Sensory Evoked Responses in Rats Fed Walleye 77-83 H. AKAGI, O. MALM, F. J. P. BRANCHES, Y. KINJO, Y. KASHIMA, J. R. D. GUIMARAES, R. B. OLIVEIRA, K. HARAGUCHI, W. C. PFEIFFER, Y.
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:
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:
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.
Download or read book Mercury Photosensitised Oxidation Reactions in the Gas Phase written by Robin Henry Burgess and published by . This book was released on 1957 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book The Gas Phase Oxidation of Hydrocarbons written by V. Ya. Shtern and published by Elsevier. This book was released on 2016-07-29 with total page 721 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Gas-Phase Oxidation of Hydrocarbons reviews research on the mechanism of oxidation of paraffins, naphthenes, olefines, and aromatic hydrocarbons and explains in detail the phenomena and theories with significant kinetic equations and graphs. This book first presents a study of the development of research on the gaseous-phase oxidation of hydrocarbons. The non-chain schemes for the oxidation of hydrocarbons, such as hydroxylation, peroxidation, and aldehyde and dehydrogenation schemes, are then discussed. This book also presents experimental investigations and important topics such as oxidation of methane and olefinic hydrocarbons. This selection will be invaluable to students and experts in the field of chemistry and related disciplines.
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.
Download or read book A New Method for Oxidation of Gaseous Elemental Mercury written by and published by . This book was released on 1999 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elemental mercury (Hg) is difficult to remove from flue-gas streams using existing wet-scrubber technology, primarily because of its limited volubility in water. We have proposed and tested a concept for enhancing gaseous Hg°removal in wet scrubber systems by altering the chemical form of the Hg° to a water-soluble oxidized species. Recently, we have discovered a new method for injection of the oxidizing species that dramatically improves reactant utilization and at the same time gives significant nitric oxide (NO) oxidation as well. Our method uses a diluted oxidizing solution containing chloric acid and sodium chlorate (sold commercially as NOXSORB{trademark}). When this solution is injected into a gas stream containing Hg° at about 300 F, we found that nearly 100% of the Hg° was removed from the gas phase and was recovered in liquid samples from the test system. At the same time, approximately 80% of the added NO was also removed (oxidized). The effect of sulfur dioxide (SO2) on this method was also investigated, and it appears to decrease slightly the amount of Hg oxidized. We are currently testing the effect of variations in oxidizing solution concentration, SO2 concentration, NO concentration, and reaction time (residence time).
Download or read book Mercury Contaminated Sites written by Ralf Ebinghaus and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: An up-to-date overview of the characterization, risk assessment and remediation of mercury-contaminated sites. The book summarizes, for the first time, works from Europe, Russia and the American continent, and review chapters are supplemented by detailed, international case studies.
Download or read book Analysis of Halogen Mercury Reactions in Flue Gas written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxidized mercury species may be formed in combustion systems through gas-phase reactions between elemental mercury and halogens, such as chorine or bromine. This study examines how bromine species affect mercury oxidation in the gas phase and examines the effects of mixtures of bromine and chlorine on extents of oxidation. Experiments were conducted in a bench-scale, laminar flow, methane-fired (300 W), quartz-lined reactor in which gas composition (HCl, HBr, NO(subscript x), SO2) and temperature profile were varied. In the experiments, the post-combustion gases were quenched from flame temperatures to about 350 C, and then speciated mercury was measured using a wet conditioning system and continuous emissions monitor (CEM). Supporting kinetic calculations were performed and compared with measured levels of oxidation. A significant portion of this report is devoted to sample conditioning as part of the mercury analysis system. In combustion systems with significant amounts of Br2 in the flue gas, the impinger solutions used to speciate mercury may be biased and care must be taken in interpreting mercury oxidation results. The stannous chloride solution used in the CEM conditioning system to convert all mercury to total mercury did not provide complete conversion of oxidized mercury to elemental, when bromine was added to the combustion system, resulting in a low bias for the total mercury measurement. The use of a hydroxylamine hydrochloride and sodium hydroxide solution instead of stannous chloride showed a significant improvement in the measurement of total mercury. Bromine was shown to be much more effective in the post-flame, homogeneous oxidation of mercury than chlorine, on an equivalent molar basis. Addition of NO to the flame (up to 400 ppmv) had no impact on mercury oxidation by chlorine or bromine. Addition of SO2 had no effect on mercury oxidation by chlorine at SO2 concentrations below about 400 ppmv; some increase in mercury oxidation was observed at SO2 concentrations of 400 ppmv and higher. In contrast, SO2 concentrations as low as 50 ppmv significantly reduced mercury oxidation by bromine, this reduction could be due to both gas and liquid phase interactions between SO2 and oxidized mercury species. The simultaneous presence of chlorine and bromine in the flue gas resulted in a slight increase in mercury oxidation above that obtained with bromine alone, the extent of the observed increase is proportional to the chlorine concentration. The results of this study can be used to understand the relative importance of gas-phase mercury oxidation by bromine and chlorine in combustion systems. Two temperature profiles were tested: a low quench (210 K/s) and a high quench (440 K/s). For chlorine the effects of quench rate were slight and hard to characterize with confidence. Oxidation with bromine proved sensitive to quench rate with significantly more oxidation at the lower rate. The data generated in this program are the first homogeneous laboratory-scale data on bromine-induced oxidation of mercury in a combustion system. Five Hg-Cl and three Hg-Br mechanisms, some published and others under development, were evaluated and compared to the new data. The Hg-halogen mechanisms were combined with submechanisms from Reaction Engineering International for NO(subscript x), SO(subscript x), and hydrocarbons. The homogeneous kinetics under-predicted the levels of mercury oxidation observed in full-scale systems. This shortcoming can be corrected by including heterogeneous kinetics in the model calculations.
Download or read book Process for Combined Control of Mercury and Nitric Oxide written by and published by . This book was released on 1999 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuing concern about the effects of mercury in the environment may lead to requirements for the control of mercury emissions from coal-fired power plants. If such controls are mandated, the use of existing flue-gas cleanup systems, such as wet scrubbers currently employed for flue-gas desulfurization, would be desirable, Such scrubbers have been shown to be effective for capturing oxidized forms of mercury, but cannot capture the very insoluble elemental mercury (Hg°) that can form a significant fraction of the total emissions. At Argonne National Laboratory, we have proposed and tested a concept for enhancing removal of Hg°, as well as nitric oxide, through introduction of an oxidizing agent into the flue gas upstream of a scrubber, which readily absorbs the soluble reaction products. Recently, we developed a new method for introducing the oxidizing agent into the flue-gas stream that dramatically improved reactant utilization. The oxidizing agent employed was NOXSORB{trademark}, which is a commercial product containing chloric acid and sodium chlorate. When a dilute solution of this agent was introduced into a gas stream containing Hg° and other typical flue-gas species at 300 F, we found that about 100% of the mercury was removed from the gas phase and recovered in process liquids. At the same time, approximately 80% of the nitric oxide was removed. The effect of sulfur dioxide on this process was also investigated and the results showed that it slightly decreased the amount of Hg° oxidized while appearing to increase the removal of nitric oxide from the gas phase. We are currently testing the effects of variations in NOXSORB{trademark} concentration, sulfur dioxide concentration, nitric oxide concentration, and reaction time (residence time). Preliminary economic projections based on the results to date indicate that the chemical cost for nitric oxide oxidation could be less than $5,000/ton removed, while for Hg° oxidation it would be about $20,000/lb removed.
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.
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.
