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Reactions of gaseous, elemental mercury with dilute halogen solutions

Description: Of the trace elements known to exist in fossil fuels, mercury (Hg) has emerged as one of the greatest concerns. Mercury has been found to be emitted from combustion in at least two different chemical forms: elemental Hg and oxidized Hg compounds. Precise identification of the oxidized compounds emitted has not been accomplished to date. However, most workers in this field assume that mercuric chloride should be the predominant oxidized species. Mercuric chloride should be readily removed in a wet scrubber system because of its relatively high solubility in water. However, it has been presumed, and we have shown, that elemental Hg will pass through a wet scrubber system with little or no removal being effected. Therefore, it is important, in order to obtain a high total Hg removal, to study methods that might result in a removal of gaseous, elemental Hg from a flue-gas stream. In this regard, we have been studying the effect of dilute halogen-containing solutions on elemental Hg in gas streams of various compositions. In particular, the results of passing Hg through bubblers containing solutions of iodine, chlorine, and chloric acid are described. Mercury found in the bubbler solutions is an indication of the extent of reaction (oxidation) of elemental Hg with the halogen species, since we have found very little Hg transferred to the liquid phase when only distilled water is used in the bubblers. Results using commercial iodine, sodium hypochlorite, and NOXSORB (sup TM) solutions are presented and discussed.
Date: July 1996
Creator: Mendelsohn, M. H. & Livengood, C. D.
Partner: UNT Libraries Government Documents Department

Critical review of mercury chemistry in flue gas.

Description: Mercury (Hg) and its compounds have long been recognized as potentially hazardous to human health and the environment. Many man-made sources of mercury have been reduced in recent years through process changes and control measures. However, emissions of mercury from coal-fired power plants, while exceedingly dilute by the usual pollution standards, still constitute a major source when considered in the aggregate. Concerns over those emissions and the prospect of impending emissions regulations have led to a wide range of research projects dealing with the measurement and control of mercury in flue gas. This work has made considerable progress in improving the understanding of mercury emissions and their behavior, but inconsistencies and unexpected results have also shown that a better understanding of mercury chemistry is needed. To develop a more complete understanding of where additional research on mercury chemistry is needed, the U.S. Department of Energy (DOE) asked Argonne National Laboratory (Argonne) to conduct a critical review of the available information as reported in the technical literature. The objectives were to summarize the current state of the art of chemistry knowledge, identify significant knowledge gaps, and recommend future research to resolve those gaps. An initial evaluation of potential review topics indicated that the scope of the review would need to be limited and focused on the most important topics relative to mercury control. To aid in this process, Argonne developed a brief survey that was circulated to researchers in the field who could help identify and prioritize the many aspects of the problem. The results of the survey were then used to design and guide a highly focused literature search that identified key papers for analysis. Each paper was reviewed, summarized, and evaluated for the relevance and quality of the information presented. The results of that work provided the basis for ...
Date: November 27, 2006
Creator: Mendelsohn, M. H. & Livengood, C. D.
Partner: UNT Libraries Government Documents Department

A new method for oxidation of gaseous, elemental mercury.

Description: 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{sup 0}removal in wet scrubber systems by altering the chemical form of the Hg{sup 0} 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{sup 0} at about 300 F, we found that nearly 100% of the Hg{sup 0} 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 (SO{sub 2}) 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, SO{sub 2} concentration, NO concentration, and reaction time (residence time).
Date: August 23, 1999
Creator: Livengood, C. D. & Mendelsohn, M. H.
Partner: UNT Libraries Government Documents Department

Process for combined control of mercury and nitric oxide.

Description: 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{sup 0}) 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{sup 0}, 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{sup 0} 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{sup 0} 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 ...
Date: November 3, 1999
Creator: Livengood, C. D. & Mendelsohn, M. H.
Partner: UNT Libraries Government Documents Department

Enhancement of mercury control in flue-gas cleanup systems

Description: This paper summarizes research at Argonne National Laboratory which is focused on techniques to enhance the capture of elemental mercury and integrate its control into existing flue-gas cleanup (FGC) systems. Both laboratory and field tests have shown that very little elemental mercury is captured in a wet scrubber system due to the low solubility of that species. To enhance the ability of wet scrubbers to capture mercury, Argonne has studied improved mass transfer through both mechanical and chemical means, as well as the conversion of elemental mercury into a more soluble species that can be easily absorbed. Current research is investigating the roles of several halogen species either alone or in combination with typical flue-gas components such as sulfur dioxide and nitric oxide in the oxidation of mercury to form compounds that are easily scrubbed from the flue gas.
Date: July 1, 1996
Creator: Livengood, C.D.; Huang, Hann S.; Mendelsohn, M.H. & Wu, Jiann M.
Partner: UNT Libraries Government Documents Department

Removal of mercury from coal-combustion flue-gas

Description: Combustion sources, including those using coal for fuel, contribute a significant fraction of total anthropogenic mercury emissions. Recent field studies have shown that current flue-gas cleanup (FGC) systems are relatively ineffective in controlling elemental mercury, which is a major component of the mercury emissions for many systems. Research at Argonne National Laboratory has been focused on techniques to enhance the capture of elemental mercury in existing FGC systems. For dry processes, these studies have included evaluation of activated carbons and investigation of sorbents based upon chemical pretreatment of low-cost mineral substrates. To enhance the ability of wet scrubbers to capture mercury, the studies have looked at the effects of improved mass transfer through both mechanical and chemical means, as well as the conversion of elemental mercury into more soluble species that can be easily absorbed.
Date: December 1, 1995
Creator: Livengood, C.D.; Huang, H.S.; Mendelsohn, M.H. & Wu, J.M.
Partner: UNT Libraries Government Documents Department

Development of mercury control enhancements for flue-gas cleanup systems

Description: Combustion sources, including those using coal for fuel, contribute a significant fraction of total anthropogenic mercury emissions. Unfortunately, recent field studies have shown that current flue-gas cleanup (FGC) systems are relatively ineffective in controlling elemental mercury, which is a major component of the mercury emissions for many systems. Research at Argonne National Laboratory has been focused on techniques to enhance the capture of elemental mercury in existing FGC systems. For dry processes, these studies have included evaluation of the factors that control mercury capture by commercial activated carbons (both with and without chemical pretreatment), testing of novel proprietary sorbents under development by several firms, and investigation of sorbents based upon chemical pretreatment of low-cost mineral substrates. To enhance the ability of wet scrubbers to capture mercury, the studies have looked at the effects of improved mass transfer through both mechanical and chemical means, as well as the conversion of elemental mercury into more soluble species that can be easily absorbed.
Date: August 1, 1995
Creator: Livengood, C.D.; Huang, H.S.; Mendelsohn, M.H. & Wu, Jiann M.
Partner: UNT Libraries Government Documents Department

Investigation of modified speciation for enhanced control of mercury

Description: Mercury was identified as a hazardous air pollutant in Title 3 of the 1990 Clean Air Act Amendments. It has been singled out for particular scrutiny because of its behavior in the environment (bioaccumulation) and its potential for deleterious effects on humans and wildlife. After studying the sources of mercury in the environment, the US Environmental Protection Agency has concluded that coal-fired boilers generate a significant fraction of the total anthropogenic emissions. Therefore, the agency is currently considering whether to impose mercury control requirements on coal-fired boilers in the electric utility industry. However, the costs for potential control measures (such as sorbent injection) can be extremely high. Mercury removal with chloric acid solutions was tested. The presence of NO increased Hg removal. It appeared that both gas-gas and gas-liquids reactions were operating, with the gas-phase reactions involving NO becoming increasingly important as the solute concentration was raised. From these studies, it was concluded that even higher Hg{sup 0} removals could be obtained if more of the reagent was made available for reaction in the gas phase. For this reason (and also to simulate a more real-world duct-injection process) a new series of tests was initiated in which an ultrasonic atomizer was used to inject small droplets of the oxidizing solutions into a flowing gas stream containing Hg{sup 0} vapors and other typical flue-gas components. The results of those tests are described in this paper.
Date: August 1, 1998
Creator: Livengood, C.D. & Mendelsohn, M.H.
Partner: UNT Libraries Government Documents Department

Investigation of modified speciation for enhanced control of mercury

Description: The control of hazardous air pollutant (HAP) emissions was addressed in Title III of the Clean Air Act Amendments of 1990, which provided an initial list of 189 elements and compounds of concern. The combustion of coal has the potential to produce a number of those species, either directly as a result of the trace elements found in coal, or as products of chemical reactions occurring in combustion. However, field studies conducted by the U.S. Department of Energy (DOE), the Electric Power Research Institute (EPRI), and others have shown that the actual emissions are very low and that effective particulate-matter capture can control most of the inorganic species. The most significant exception is mercury, which has also been singled out for particular regulatory attention because of its behavior in the environment (bioaccumulation) and the potential for deleterious health effects. In anticipation of possible regulations regarding mercury emissions, research efforts sponsored by DOE, EPRI, and others are investigating the risks posed by mercury emissions, improved techniques for measuring those emissions, and possible control measures. The focus in the control research is on techniques that can be used in conjunction with existing flue-gas-cleanup (FGC) systems in order to minimize additional capital costs and operational complexity. The very small amount of mercury (on the order of a few micrograms per cubic meter) in flue gas, its occurrence in several chemical forms that vary from system to system, the very low solubility of the elemental form, and the fact that it is usually in the vapor phase combine to make the achievement of cost-effective control a challenging task.
Date: September 1, 1997
Creator: Livengood, C.D. & Mendelsohn, M.H.
Partner: UNT Libraries Government Documents Department

Enhanced control of mercury emissions through modified speciation

Description: In anticipation of possible regulations regarding mercury emissions, research efforts sponsored by DOE, EPRI, and others are investigating the risks posed by mercury emissions, improved techniques for measuring those emissions, and possible control measures. The focus in the control research is on techniques that can be used in conjunction with existing flue-gas-cleanup (FGC) systems in order to minimize additional capital costs and operational complexity. Argonne National Laboratory has supported the DOE Fossil Energy Program for over 15 years with research on advanced environmental control technologies. The emphasis in Argonne`s work has been on integrated systems that combine control of several pollutants. Specific topics have included spray drying for sulfur dioxide and particulate-matter control with high-sulfur coal, combined sulfur dioxide and nitrogen oxides control technologies, and techniques to enhance mercury control in existing FGC systems. The latter area has focused on low-cost dry sorbents for use with fabric filters or electrostatic precipitators and techniques for improving the capture of mercury in wet flue-gas desulfurization (FGD) systems. This paper presents results from recent work that has studied the effects of several oxidizing agents in combination with typical flue-gas species (e.g., nitrogen oxides and sulfur dioxide) on the oxidation of Hg{sup 0}.
Date: July 1, 1997
Creator: Livengood, C.D. & Mendelsohn, M.H.
Partner: UNT Libraries Government Documents Department

Development of mercury control techniques for utility boilers

Description: This paper gives an overview of research being conducted at Argonne National Laboratory on the capture of mercury in flue gas by both dry sorbents and wet scrubbers. The emphasis in the research is on development of a better understanding of the key factors that control the capture of mercury. Future work is expected to utilize that information for the development of new or modified process concepts featuring enhanced mercury capture capabilities.
Date: June 1, 1995
Creator: Livengood, C.D.; Mendelsohn, M.H.; Huang, H.S. & Wu, J.M.
Partner: UNT Libraries Government Documents Department

Development of mercury control technology for coal-fired systems

Description: The emission of hazardous air pollutants (air toxics) from various industrial processes has emerged as a major environmental issue that was singled out for particular attention in the Clean Air Act Amendments of 1990. In particular, mercury emissions are the subject of several current EPA studies because of concerns over possible serious effects on human health. Some of those emissions originate in the combustion of coal, which contains trace amounts of mercury, and are likely to be the subject of control requirements in the relatively near future. Data collected by the Department of Energy (DOE) and the Electric Power Research Institute (EPRI) at operating electric-power plants have shown that conventional flue-gas cleanup (FGC) technologies are not very effective in controlling emissions of mercury in general, and are particularly poor at controlling emissions of elemental mercury. This paper gives an overview of research being conducted at Argonne National Laboratory on improving the capture of mercury in flue gas through the use of dry sorbents and/or wet scrubbers. The results and conclusions to date from the Argonne research on dry sorbents can be summarized as follows: lime hydrates, either regular or high-surface-area, are not effective in removing elemental mercury; mercury removals are enhanced by the addition of activated carbon; mercury removals with activated carbon decrease with increasing temperature, larger particle size, and decreasing mercury concentration in the gas; chemical pretreatment (e.g., with sulfur or CaCl{sub 2}) can greatly increase the removal capacity of activated carbon; chemically treated mineral substrates have the potential to be developed into effective and economical mercury sorbents; sorbents treated with different chemicals respond in significantly different ways to changes in flue-gas temperature.
Date: August 1, 1995
Creator: Livengood, D.C.; Huang, H.S.; Mendelsohn, M.H. & Wu, Jiann M.
Partner: UNT Libraries Government Documents Department

Elemental mercury removal using a wet scrubber.

Description: Mercury (Hg) is a toxic metal that is emitted into the environment by both natural and human activities. Acute and chronic exposure to mercury and methyl mercury in humans results in central nervous system damage, kidney damage, and even death. Although some Hg emission sources have been regulated, coal-fired utilities have not been. In anticipation of federal regulations on mercury emissions from coal-fired power plants, Argonne National Laboratory (ANL) has designed a flue gas simulation system to study the removal of elemental mercury. The simulated flue gas enters the system and combines with the inlet mercury vapor (from a calibrated permeation tube), carried by nitrogen gas. This combined gas continues past the flow meter and the pressure gage to the reactor inlet. Inside the reactor chamber, the flue gas is sprayed with NOXSORB{reg_sign}, a chloric acid solution, which reacts with elemental mercury. The amount of reaction (oxidation) of elemental mercury is important since mercury in an oxidized form is highly soluble, In this form, the Hg can be picked up downstream by a wet scrubber from fossil-fuel burning utilities. Experiments on mercury removal from flue gases have been conducted at ANL, with the participation of a senior design team from Purdue University Calumet. Temperature variations ranging from room temperature to 350 F have been studied. Other parameters, such as the concentration of NOXSORB{reg_sign}, were also tested. Furthermore, pump speed and sprayer droplet sizes of the NOXSORB{reg_sign} solution were studied. A literature survey on the current and proposed mercury control legislation, along with the existing control technologies, has been performed as part of the senior design project. With guidance from ANL, an understanding of the simulation system has been developed. This information has been used to determine the mass transfer. Another literature survey was performed on the reaction kinetics of mercury. ...
Date: May 19, 1999
Creator: Gonzalez, E.; Livengood, C. D.; Martin, K.; Mendelsohn, M. H. & Zhou, C. Q.
Partner: UNT Libraries Government Documents Department