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The Effects Of Carbon In Ash On Mercury Capture From Flue Gas
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Book Synopsis The Effects of Carbon-in-ash on Mercury Capture from Flue Gas by : Kyung Man Kim
Download or read book The Effects of Carbon-in-ash on Mercury Capture from Flue Gas written by Kyung Man Kim and published by . This book was released on 2010 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury existing as a trace element in coal is an important pollutant because coal burning is increasing around the world for energy production and coal-fired plants are the largest anthropogenic source of mercury emission to the environment. Mercury behavior in the homogeneous conditions of cooling flue gas is characterized using equilibrium study and fundamental mercury kinetics depending on the time-temperature history. Up-to-date version of mercury oxidation based on quench rate is plotted with revised mercury mechanism. Slow quench rates show better mercury oxidation at the typical cooling rate in power plant. Mercury capture mostly occurs under heterogeneous conditions between sorbent particles and gaseous mercury, and this study is mainly devoted to understanding the role of carbon-in-ash on mercury capture from flue gas. Coal flyash samples are characterized by loss-on-ignition (LOI), surface area (BET) tests, and scanning electron microscopy (SEM). Flyash sorbents are injected using an in-flight configuration and then mercury concentration is measured by Hg CEMS. The unburned carbon is one main factor for capturing mercury. However, mercury uptake is shown to be relatively low when using flyash from high rank coal such as anthracite because of the small surface area coming from the non-porous structure. Therefore, when flyash is used as a sorbent for mercury capture, quantitative surface area should be compared and coal rank also should be considered. Non-carbon zeolite injection showed that carbon has physico-chemically favorable structure to capture mercury as well as creating high surface area with the ash. A detailed diffusion mechanism for the mercury capture process was examined using a relatively simple 1-D model. Porosity and Knudsen diffusivity are very important in intra-particle diffusion based on the investigation of sensitivity of diffusion factors. Under the conditions of this study, it appears that elemental mercury can be more readily captured than oxidized mercury because of its lower molecular weight.
Book Synopsis Mercury Control by : Evan J. Granite
Download or read book Mercury Control written by Evan J. Granite and published by John Wiley & Sons. This book was released on 2015-01-20 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: This essential handbook and ready reference offers a detailed overview of the existing and currently researched technologies available for the control of mercury in coal-derived gas streams and that are viable for meeting the strict standards set by environmental protection agencies. Written by an internationally acclaimed author team from government agencies, academia and industry, it details US, EU, Asia-Pacific and other international perspectives, regulations and guidelines.
Book Synopsis Coal Fired Flue Gas Mercury Emission Controls by : Jiang Wu
Download or read book Coal Fired Flue Gas Mercury Emission Controls written by Jiang Wu and published by Springer. This book was released on 2015-03-17 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury (Hg) is one of the most toxic heavy metals, harmful to both the environment and human health. Hg is released into the atmosphere from natural and anthropogenic sources and its emission control has caused much concern. This book introduces readers to Hg pollution from natural and anthropogenic sources and systematically describes coal-fired flue gas mercury emission control in industry, especially from coal-fired power stations. Mercury emission control theory and experimental research are demonstrated, including how elemental mercury is oxidized into oxidized mercury and the effect of flue gas contents on the mercury speciation transformation process. Mercury emission control methods, such as existing APCDs (air pollution control devices) at power stations, sorbent injection, additives in coal combustion and photo-catalytic methods are introduced in detail. Lab-scale, pilot-scale and full-scale experimental studies of sorbent injection conducted by the authors are presented systematically, helping researchers and engineers to understand how this approach reduces the mercury emissions in flue gas and to apply the methods in mercury emission control at coal-fired power stations. Readers will arrive at a comprehensive understanding of various mercury emission control methods that are suitable for industrial applications. The book is intended for scientists, researchers, engineers and graduate students in the fields of energy science and technology, environmental science and technology and chemical engineering.
Book Synopsis Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas by : Sharon Sjostrom
Download or read book Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas written by Sharon Sjostrom and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With the Nation's coal-burning utilities facing the possibility of tighter controls on mercury pollutants, the U.S. Department of Energy is funding projects that could offer power plant operators better ways to reduce these emissions at much lower costs. Sorbent injection technology represents one of the simplest and most mature approaches to controlling mercury emissions from coal-fired boilers. It involves injecting a solid material such as powdered activated carbon into the flue gas. The gas-phase mercury in the flue gas contacts the sorbent and attaches to its surface. The sorbent with the mercury attached is then collected by the existing particle control device along with the other solid material, primarily fly ash. During 2001, ADA Environmental Solutions (ADA-ES) conducted a full-scale demonstration of sorbent-based mercury control technology at the Alabama Power E.C. Gaston Station (Wilsonville, Alabama). This unit burns a low-sulfur bituminous coal and uses a hot-side electrostatic precipitator (ESP) in combination with a Compact Hybrid Particulate Collector (COHPAC{reg_sign}) baghouse to collect fly ash. The majority of the fly ash is collected in the ESP with the residual being collected in the COHPAC{reg_sign} baghouse. Activated carbon was injected between the ESP and COHPAC{reg_sign} units to collect the mercury. Short-term mercury removal levels in excess of 90% were achieved using the COHPAC{reg_sign} unit. The test also showed that activated carbon was effective in removing both forms of mercury-elemental and oxidized. However, a great deal of additional testing is required to further characterize the capabilities and limitations of this technology relative to use with baghouse systems such as COHPAC{reg_sign}. It is important to determine performance over an extended period of time to fully assess all operational parameters. The project described in this report focuses on fully demonstrating sorbent injection technology at a coal-fired power generating plant that is equipped with a COHPAC{reg_sign} system. The overall objective is to evaluate the long-term effects of sorbent injection on mercury capture and COHPAC{reg_sign} performance. The work is being done on one-half of the gas stream at Alabama Power Company's Plant Gaston Unit 3 (nominally 135 MW). Data from the testing will be used to determine: (1) If sorbent injection into a high air-to-cloth ratio baghouse is a viable, long-term approach for mercury control; and (2) Design criteria and costs for new baghouse/sorbent injection systems that will use a similar, polishing baghouse (TOXECON{trademark}) approach.
Book Synopsis Fundamental Understanding of Mercury Removal from Coal Combustion by : Erdem Sasmaz
Download or read book Fundamental Understanding of Mercury Removal from Coal Combustion written by Erdem Sasmaz and published by Stanford University. This book was released on 2011 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coal-fired power plants are a major anthropogenic source of worldwide mercury (Hg) emissions. Since mercury is considered to be one of the most toxic metals found in the environment, Hg emissions from coal-fired power plants is of major environmental concern. Mercury in coal is vaporized into its gaseous elemental form throughout the coal combustion process. Elemental Hg can be oxidized in subsequent reactions with other gaseous components (homogeneous) and solid materials (heterogeneous) in coal-fired flue gases. While oxidized Hg in coal-fired flue gases is readily controlled by its adsorption onto fly ash and/or its dissolution into existing solution-based sulfur dioxide (SO2) scrubbers, elemental Hg is not controlled. The extent of elemental Hg formed during coal combustion is difficult to predict since it is dependent on the type of coal burned, combustion conditions, and existing control technologies installed. Therefore, it is important to understand heterogeneous Hg reaction mechanisms to predict the speciation of Hg emissions from coal-fired power plants to design and effectively determine the best applicable control technologies. In this work, theoretical and experimental investigations have been performed to investigate the adsorption and in some cases the oxidation, of Hg on solid surfaces, e.g., calcium oxide (CaO), noble metals and activated carbon (AC). The objective of this research is to identify potential materials that can be used as multi-pollutant sorbents in power plants by carrying out both high-level density functional theory (DFT) electronic structure calculations and experiments to understand heterogeneous chemical pathways of Hg. This research uses a fundamental science-based approach to understand the environmental problems caused by coal-fired energy production and provides solutions to the power generation industry for emissions reductions. Understanding the mechanism associated with Hg and SO2 adsorption on CaO will help to optimize the conditions or material to limit Hg emissions from the flue gas desulfurization process. Plane-wave DFT calculations were used to investigate the binding mechanism of Hg species and SO2 on the CaO(100) surface. The binding strengths on the high-symmetry CaO adsorption sites have been investigated for elemental Hg, SO2, mercury chlorides (HgCl and HgCl2) and mercuric oxide (HgO). It has been discovered that HgCl, HgCl2, and SO2 chemisorb on the CaO(100) surface at 0.125 ML coverage. Binding energies of elemental Hg are minimal indicating a physisorption mechanism. Noble metals such as palladium (Pd), gold (Au), silver (Ag), and copper (Cu) have been proposed to capture elemental Hg. Plane-wave DFT calculations have been carried out to investigate the mercury interactions with Pd binary alloys and overlays in addition to pure Pd, Au, Ag, and Cu surfaces. It has been determined that Pd has the highest mercury binding energy in comparison to other noble metals. In addition, Pd is found to be the primary surface atom responsible for increasing the adsorption of Hg with the surface in both Pd binary alloys and overlays. Deposition of Pd overlays on Au and Ag has been found to enhance the reactivity of the surface by shifting the d-states of surface atoms up in energy. The possible binding mechanisms of elemental Hg onto virgin, brominated and sulfonated AC fiber and brominated powder AC sorbents have been investigated through packed-bed experiments in a stream of air and simulated flue gas conditions, including SO2, hydrogen chloride (HCl), nitrogen oxide (NO) nitrogen dioxide (NO2). A combination of spectroscopy and plane-wave DFT calculations was used to characterize the sorption process. X-ray photoelectron spectroscopy (XPS) and x-ray absorption fine structure (XAFS) spectroscopy were used to analyze the surface and bulk chemical compositions of brominated AC sorbents reacted with Hg0. Through XPS surface characterization studies it was found that Hg adsorption is primarily associated with halogens on the surface. Elemental Hg is oxidized on AC surfaces and the oxidation state of adsorbed Hg is found to be Hg2+. Though plane-wave DFT and density of states (DOS) calculations indicate that Hg is more stable when it is bound to the edge carbon atom interacting with a single bromine bound atop of Hg, a model that includes an interaction between the Hg and an additional Br atom matches best with experimental data obtained from extended x-ray absorption fine structure (EXAFS) spectroscopy. The flue gas species such as HCl and bromine (Br2) enhance the Hg adsorption, while SO2 is found to decrease the Hg adsorption significantly by poisoning the active sites on the AC surface. The AC sorbents represent the most market-ready technology for Hg capture and therefore have been investigated by both theory and experiment in this work. Future work will include similar characterization and bench-scale experiments to test the metal-based materials for the sorbent and oxidation performance.
Book Synopsis Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired Flue Gas by :
Download or read book Field Test Program for Long-Term Operation of a COHPAC System for Removing Mercury from Coal-Fired 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: With the Nation's coal-burning utilities facing the possibility of tighter controls on mercury pollutants, the U.S. Department of Energy is funding projects that could offer power plant operators better ways to reduce these emissions at much lower costs. Sorbent injection technology represents one of the simplest and most mature approaches to controlling mercury emissions from coal-fired boilers. It involves injecting a solid material such as powdered activated carbon into the flue gas. The gas-phase mercury in the flue gas contacts the sorbent and attaches to its surface. The sorbent with the mercury attached is then collected by the existing particle control device along with the other solid material, primarily fly ash. During 2001, ADA Environmental Solutions (ADA-ES) conducted a full-scale demonstration of sorbent-based mercury control technology at the Alabama Power E.C. Gaston Station (Wilsonville, Alabama). This unit burns a low-sulfur bituminous coal and uses a hot-side electrostatic precipitator (ESP) in combination with a Compact Hybrid Particulate Collector (COHPAC{reg_sign}) baghouse to collect fly ash. The majority of the fly ash is collected in the ESP with the residual being collected in the COHPAC{reg_sign} baghouse. Activated carbon was injected between the ESP and COHPAC{reg_sign} units to collect the mercury. Short-term mercury removal levels in excess of 90% were achieved using the COHPAC{reg_sign} unit. The test also showed that activated carbon was effective in removing both forms of mercury-elemental and oxidized. However, a great deal of additional testing is required to further characterize the capabilities and limitations of this technology relative to use with baghouse systems such as COHPAC{reg_sign}. It is important to determine performance over an extended period of time to fully assess all operational parameters. The project described in this report focuses on fully demonstrating sorbent injection technology at a coal-fired power generating plant that is equipped with a COHPAC{reg_sign} system. The overall objective is to evaluate the long-term effects of sorbent injection on mercury capture and COHPAC{reg_sign} performance. The work is being done on one-half of the gas stream at Alabama Power Company's Plant Gaston Unit 3 (nominally 135 MW). Data from the testing will be used to determine: (1) If sorbent injection into a high air-to-cloth ratio baghouse is a viable, long-term approach for mercury control; and (2) Design criteria and costs for new baghouse/sorbent injection systems that will use a similar, polishing baghouse (TOXECON{trademark}) approach.
Book Synopsis Effects of Fly Ash on the Oxidation of Mercury During Post-combustion Conditions by : Hongqun Yang
Download or read book Effects of Fly Ash on the Oxidation of Mercury During Post-combustion Conditions written by Hongqun Yang and published by . This book was released on 2002 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury emissions from coal-fired power plants pose impact on human health. The emissions will be regulated in the near future. Mercury speciation in flue gas has an important effect on the efficiency of mercury emission control devices. This study focuses on the role of fly ash on the oxidation of Hg0 in bench-scale simulated flue gas environment and in laboratory-scale coal combustion flue gas environment. The effects of flue gas matrices, temperature, fly ash mineralogy and morphology on the oxidation of Hg0 are studied. Conclusions are drawn based on the testing results: *Mercury chemistry is very complex in flue gas. *The presence of fly ash is critical for heterogeneous Hg0 oxidation. *The flue gas components, including NO2, HC1, NO and SO2, have strong effects on the potential of whole fly ashes to oxidize Hg0. *Fly ash specific surface area appears to have a determining effect on Hg0 heterogeneous oxidation.
Book Synopsis Clean Air Act by : John B. Stephenson (au)
Download or read book Clean Air Act written by John B. Stephenson (au) and published by DIANE Publishing. This book was released on 2005-12 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: In March 2005, the EPA issued a rule that will limit mercury emissions (ME) -- a toxic element that causes neurological problems -- from coal-fired power plants, the nation's largest ind'l. source of ME. Under the rule, ME are to be reduced from a baseline of 48 tons/yr. to 38 tons in 2010 & to 15 tons in 2018. The ME target for 2010 is based on the level of ME achievable with technol. for controlling other pollutants -- which also capture some mercury -- because it believed emerging mercury controls had not been adequately demonstrated. This report: describes the use, availability, & effectiveness of technol. to reduce ME at power plants; & identifies the factors that influence the cost of these technol. & reports on available cost estimates. Tables.
Book Synopsis Development of Mercury Control Technology for Coal-fired Systems by :
Download or read book Development of Mercury Control Technology for Coal-fired Systems written by and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 CaCl2) 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.
Book Synopsis Investigation and Demonstration of Dry Carbon-Based Sorbent Injection for Mercury Control by : Terry Hunt
Download or read book Investigation and Demonstration of Dry Carbon-Based Sorbent Injection for Mercury Control written by Terry Hunt and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Public Service Company of Colorado and ADA Technologies, Inc. have performed a study of the injection of activated carbon for the removal of vapor-phase mercury from coal-fired flue gas streams. The project was completed under contract to the US Department of Energy's National Energy Technology Laboratory, with contributions from EPRI and Public Service Company. The prime contractor for the project was Public Service Company, with ADA Technologies as the major subcontractor providing technical support to all aspects of the project. The research and development effort was conducted in two phases. In Phase I a pilot facility was fabricated and tests were performed using dry carbon-based sorbent injection for mercury control on a coal-fired flue gas slipstream extracted from an operating power plant. Phase II was designed to move carbon injection technology towards commercial application on coal-fired power plants by addressing key reliability and operability concerns. Phase II field work included further development work with the Phase I pilot and mercury measurements on several of PSCo's coal-fired generating units. In addition, tests were run on collected sorbent plus fly ash to evaluate the impact of the activated carbon sorbent on the disposal of fly ash. An economic analysis was performed where pilot plant test data was used to develop a model to predict estimated costs of mercury removal from plants burning western coals. Testing in the pilot plant was undertaken to quantify the effects of plant configuration, flue gas temperature, and activated carbon injection rate on mercury removal. All three variables were found to significantly impact the mercury removal efficiency in the pilot. The trends were clear: mercury removal rates increased with decreasing flue gas temperature and with increasing carbon injection rates. Mercury removal was much more efficient with reverse-gas and pulse-jet baghouse configurations than with an ESP as the particulate control device. The native fly ash of the host unit provided significant mercury removal capacity, so that the activated carbon sorbent served as an incremental mercury removal mechanism. Tests run to characterize the waste product, a combination of fly ash and activated carbon on which mercury was present, showed that mercury and other RCRA metals of interest were all below Toxic Characteristic Leaching Procedure (TCLP) regulatory limits in the leachate. The presence of activated carbon in the fly ash was shown to have an effect on the use of fly ash as an additive in the manufacture of concrete, which could limit the salability of fly ash from a plant where activated carbon was used for mercury control.
Book Synopsis Mercury Reaction Chemistry in Combustion Flue Gases from Experiments and Theory by : Bihter Padak
Download or read book Mercury Reaction Chemistry in Combustion Flue Gases from Experiments and Theory written by Bihter Padak and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions from coal combustion processes constitute a significant amount of the elemental mercury released into the atmosphere today. Coal-fired power plants in the United States, with the capacity of just over 300GW, are the greatest anthropogenic source of mercury emissions. Mercury exists in coal combustion flue gas in a variety of forms depending on the coal type and combustion conditions; i.e., elemental, oxidized and particulate. Particulate mercury in the flue gas can be removed using air pollution control devices such as electrostatic precipitators and fabric filters. Oxidized mercury is easily captured by wet flue gas desulfurization scrubbers, while gaseous elemental mercury passes through the scrubbers readily. Activated carbon, when injected into the gas stream of coal-fired boilers, is effective in capturing both elemental and oxidized mercury through adsorption processes. However, the mechanism by which mercury adsorbs on activated carbon is not exactly known and its understanding is crucial to the design and fabrication of effective capture technologies for mercury. The objective of the current study is to apply theoretical-based cluster modeling to examine the possible binding mechanism of mercury on activated carbon. The effects of activated carbon's different surface functional groups and halogens on elemental mercury adsorption have been examined. Also, a thermodynamic approach is followed to examine the binding mechanism of mercury and its oxidized species such as HgCl and HgCl2 on a simulated carbon surface with and without Cl. Energies of different possible surface complexes and possible products are compared and dominant pathways are determined relatively. Since different methods are employed to capture varying forms of mercury, understanding mercury speciation during combustion and how the transformations occur between different forms is essential to developing an effective control mechanism for removing mercury from flue gas. In this study, homogeneous oxidation of mercury via chlorine is examined experimentally in a simulated flue gas environment. Mercury and chlorine are introduced into a laminar premixed methane-air flame. Cooled flue gas is sampled and sent to a custom-built electron ionization quadrupole mass spectrometer specially designed for mercury measurement on the order of parts per billion (ppb) in flue gas. The use of a mass spectrometer allows for distinguishing between the different forms of oxidized mercury (Hg+, Hg+2). By directly measuring mercury species accurately, one can determine the actual extent of mercury oxidation in the flue gas, which will aid in further developing mercury control technologies.
Book Synopsis Removal of Mercury from Coal-combustion Flue-gas by :
Download or read book Removal of Mercury from Coal-combustion Flue-gas written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Mercury Emissions from Curing Concretes that Contain Fly Ash and Activated Carbon Sorbents by : C. Cheng
Download or read book Mercury Emissions from Curing Concretes that Contain Fly Ash and Activated Carbon Sorbents written by C. Cheng and published by . This book was released on 2006 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: One method for reduction of mercury emissions from coal-fired utility boilers is injection of chemically modified powdered activated carbon sorbents into hot flue gas streams and subsequent capture of the mercury-containing sorbent along with fly ash. The trapping of mercury by sorbents boosts the net quantity of mercury in the resulting composite fly ash-sorbent, thus increasing the total mercury content in the final coal combustion product. Because this fly ash-sorbent may be incorporated into various types of concrete, an understanding of the fate of mercury in these concretes is needed to support future applications of the new fly ash-sorbent products. Possible differences in gaseous mercury releases from curing fly-ash concretes were investigated by collection and measurement of mercury from concretes that contained different fly ashes and carbon-based sorbents. Air above curing concretes was sampled by iodated carbon traps to collect gas-phase mercury over the standard 28-day curing period. Air sampling was extended for an additional 28 days for two selected concretes. All experiments were performed in a laboratory environment and were designed to provide estimates of upper limits on gaseous mercury release from curing concretes that contain fly ash and sorbent material. The observed emissions of mercury for the complete curing process demonstrated a dependency on mercury concentrations in the concrete, the type of coal burned, and the presence of sorbent. Release of mercury from these concretes was less than 0.31% of the total quantity of mercury present from all sources. The dependence of mercury release on the organic carbon content of the fly ash was particularly notable. Lower emissions of mercury were observed for the ash containing activated carbon sorbent than would be expected based on the correlation with organic carbon, suggesting that the brominated powdered activated carbon more tightly binds the mercury as compared to unburned carbon in the ash. During the extended curing tests, mercury release slowly diminished with time. The decrease in mercury emission corresponds to an expected loss of porosity for the concrete and loss of water to hydration reactions by the components of cement.
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 Demonstration of An Integrated Approach to Mercury Control at Lee Station by :
Download or read book Demonstration of An Integrated Approach to Mercury Control at Lee Station written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: General Electric (GE) has developed an approach whereby native mercury reduction on fly ash can be improved by optimizing the combustion system. This approach eliminates carbon-rich areas in the combustion zone, making the combustion process more uniform, and allows increasing carbon content in fly ash without significant increase in CO emissions. Since boiler excess O2 can be also reduced as a result of optimized combustion, this process reduces NO(subscript x) emissions. Because combustion optimization improves native mercury reduction on fly ash, it can reduce requirements for activated carbon injection (ACI) when integrated with sorbent injection for more efficient mercury control. The approach can be tailored to specific unit configurations and coal types for optimal performance. This report describes results of a U.S. DOE sponsored project designed to evaluate the effect of combustion conditions on 'native' mercury capture on fly ash and integrate combustion optimization for improved mercury and NO(subscript x) reduction with ACI. The technology evaluation took place in Lee Station Unit 3 located in Goldsboro, NC and operated by Progress Energy. Unit 3 burns a low-sulfur Eastern bituminous coal and is a 250 MW opposed-wall fired unit equipped with an ESP with a specific collection area of 249 ft2/kacfm. Unit 3 is equipped with SO3 injection for ESP conditioning. The technical goal of the project was to evaluate the technology's ability to achieve 70% mercury reduction below the baseline emission value of 2.9 lb/TBtu, which was equivalent to 80% mercury reduction relative to the mercury concentration in the coal. The strategy to achieve the 70% incremental improvement in mercury removal in Unit 3 was (1) to enhance 'naturally' occurring fly ash mercury capture by optimizing the combustion process and using duct humidification to reduce flue gas temperatures at the ESP inlet, and (2) to use ACI in front of the ESP to further reduce mercury emissions. The program was comprised of field and pilot-scale tests, engineering studies and consisted of eight tasks. As part of the program, GE conducted pilot-scale evaluation of sorbent effect on mercury reduction, supplied and installed adjustable riffle boxes to assist in combustion optimization, performed combustion optimization, supplied mobile sorbent injection and flue gas humidification systems, conducted CFD modeling of sorbent injection and flue gas humidification, and performed mercury testing including a continuous 30-day sorbent injection trial. Combustion optimization was the first step in reduction of mercury emissions. Goals of combustion optimization activities were to improve 'native' mercury capture on fly ash and reduce NO(subscript x). Combustion optimization included balancing of coal flow through individual burners to eliminate zones of carbon-rich combustion, air flow balancing, and burner adjustments. As part of the project, the original riffle boxes were replaced with Foster-Wheeler's adjustable riffle boxes to allow for biasing the coal flow between the coal pipes. A 10-point CO/O2/NO(subscript x) grid was installed in the primary superheater region of the back pass to assist in these activities. Testing of mercury emissions before and after combustion optimization demonstrated that mercury emissions were reduced from 2.9 lb/TBtu to 1.8 lb/TBtu due to boiler operation differences in conjunction with combustion optimization, a 38% improvement in 'native' mercury capture on fly ash. Native mercury reduction from coal was (almost equal to)42% at baseline conditions and 64% at optimized combustion conditions. As a result of combustion optimization NO(subscript x) emissions were reduced by 18%. A three-dimensional CFD model was developed to study the flow distribution and sorbent injection in the post air heater duct in Lee Station Unit 3. Modeling of the flow pattern exiting the air pre-heater demonstrated that because of the duct transition from a circular opening at the exit of air-pre-heater to a rectangular ESP inlet duct, flow separation occurred at the corners after the transition. Modeling also demonstrated that the flow was severely biased from the South side to the North side due to the bend of the duct. Results of CFD modeling were used to design lances for better sorbent distribution across the ESP inlet duct. Modeling of water injection demonstrated that because of flue gas temperature biasing, the droplet evaporation rate was slower on the North side than that on the South side of the duct. Modeling suggested that an improvement of water droplet evaporation could be achieved by closing the lance on the North side where flue gas temperatures were lower. Preliminary evaluation of the effect of carbon-based sorbents on mercury reduction took place in a 1 MBtu/hr (300 kW) Boiler Simulator Facility using the same coal as fired at Lee Station.
Book Synopsis Mercury study report to Congress by :
Download or read book Mercury study report to Congress written by and published by DIANE Publishing. This book was released on with total page 1811 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis EFFECTS OF FLY ASH ON MERCURY OXIDATION DURING POST COMBUSTION CONDITIONS. by :
Download or read book EFFECTS OF FLY ASH ON MERCURY OXIDATION DURING POST COMBUSTION CONDITIONS. written by and published by . This book was released on 2000 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests were performed in simulated flue gas streams using two fly ash samples from the electrostatic precipitators of two full-scale utility boilers. One fly ash was derived from a Powder River Basin (PRB) coal, while the other was derived from Blacksville coal (Pittsburgh No. 8 seam). The tests were performed at temperatures of 120 and 180 C under different gas compositions using whole fly ash samples as well as magnetic and nonmagnetic concentrates from sized fly ash. Only the Blacksville ash contained magnetic phases. The whole and fractionated fly ash samples were analyzed for morphology, chemical composition, mineralogical composition, total organic carbon, porosity, and surface area. Mineralogically, the Blacksville ash was composed predominantly of magnetite, hematite, quartz, and mullite, while the PRB ash contained mostly quartz with lesser amounts of lime, periclase, and calcium aluminum oxide. The iron oxides in the Blacksville ash were concentrated almost entirely in the largest size fraction. As anticipated, there was not a clean separation of magnetic (Fe-rich) and nonmagnetic (aluminosilicate-rich) phases for the Blacksville ash. The Blacksville ash had a significantly higher surface area and a much higher unburned carbon content than the PRB ash. Elemental mercury (Hg) streams were injected into the simulated flue gas and passed over filters (housed in a convection oven) loaded with fly ash. Concentrations of total, oxidized, and elemental Hg downstream from the ash samples were determined by the Ontario Hydro Method. The gas stream composition and whether or not ash was present in the gas stream were the two most important variables. Based on the statistical analyses, the presence of HCl, NO, NO2, and SO2 and all two-way gas interactions were significant. In addition, it appears that even four-factor interactions between those gases are significant. The HCl, NO2, and SO2 were critical gases resulting in Hg oxidation, while the presence of NO appeared to suppress oxidation. The Blacksville fly ash tended to show slightly more catalytic activity than the PRB fly ash, but this could be largely due to the higher surface area of the Blacksville ash. Temperature was not a statistically important factor. The magnetic (Fe-rich) phases did not appear to be more catalytically active than the nonmagnetic phases, and unburned carbon did not appear to play a critical role in oxidation chemistry.
