Ozonation for the chemical modification of carbon surfaces in fly ash

Gao, Yuan; Külaots, Indrek; Chen, X.; Aggarwal, R. K.; Mehta, A.K.; Suuberg, Eric M.; Hurt, Robert H.

doi:10.1016/s0016-2361(00)00149-6

Cited by 29 publications

(44 citation statements)

References 14 publications

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“…5.I). Figure 5.II shows the classical Criegee mechanism of ozonolysis, involving 1,3 dipolar cycloaddition to carbon carbon double bonds as described by Criegee [25], and later confirmed by 17 ONMR spectroscopy [26]. The primary ozonide in Fig.…”

Section: Resultsmentioning

confidence: 67%

“…Oxidation imparts hydrophilicity to carbon surfaces [16,17], which is desirable for Hg-sorbents used in power station applications, where contamination of fly ash by hydrophobic activated carbon adversely affects the properties of fly ash concrete [16,18]. In previous experiments from our laboratory, ozone treatment did increase the hydrophilicity of activated carbon as desired, but did not enhance the performance of the activated carbon as mercury sorbent, and under some conditions degraded the performance.…”

Section: Introductionmentioning

confidence: 89%

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High capacity mercury adsorption on freshly ozone-treated carbon surfaces

Manchester

Wang

Külaots

et al. 2008

Carbon

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A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozonetreated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with aging. FTIR analysis shows broad C-O stretch features from 950 to 1300 cm −1 , which decay upon atmospheric exposure and are similar to the C-O-C asymmetric stretch features of ethylene secondary ozonide. The combined results suggest that the ultra-high mercury capture efficiency is due to a subset of labile C-O functional groups with residual oxidizing power that are likely epoxides or (epoxide-containing) secondary ozonides. The results open the possibility for in situ ozonolysis to create high-performance carbon-based Hg sorbents.

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Section: Resultsmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 89%

High capacity mercury adsorption on freshly ozone-treated carbon surfaces

Manchester

Wang

Külaots

et al. 2008

Carbon

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“…The cumulative amounts of ozone fed to the reactor in these experiments ranged from 51 to 251 gm-ozone/kg ash and were 4 to 21 time higher than the minimum theoretical stoichiometric requirement for complete NH 3 oxidation to nitrate and water. This high ozone usage is likely due to kinetic limitations of the ozone / ammonia reaction, which has been previously studied in aqueous solution where it exhibits reaction times on the order of minutes or greater [Kuo et al 1997, Singer andZilli, 1975], and to competition from the ozone/carbon chemisorption reaction, which is fast [Gao et al, 2001]. The ozone/carbon chemisorption reaction is known to improve the air entrainment behavior of these high carbon ashes by reducing hydrophobic surface area [Gao et al, 2001], but here the reaction rapidly consumes ozone that would otherwise be available for ammonia destruction.…”

Section: Flowing Fogmentioning

confidence: 99%

“…This high ozone usage is likely due to kinetic limitations of the ozone / ammonia reaction, which has been previously studied in aqueous solution where it exhibits reaction times on the order of minutes or greater [Kuo et al 1997, Singer andZilli, 1975], and to competition from the ozone/carbon chemisorption reaction, which is fast [Gao et al, 2001]. The ozone/carbon chemisorption reaction is known to improve the air entrainment behavior of these high carbon ashes by reducing hydrophobic surface area [Gao et al, 2001], but here the reaction rapidly consumes ozone that would otherwise be available for ammonia destruction. The extent of ammonia removal/destruction by ozone increases with increasing temperature to 150 o C, further suggesting kinetic limitations for this reaction.…”

Section: Flowing Fogmentioning

confidence: 99%

“…These two objectives form the basis for the two tasks described below: In Task 5.2 on ammonia removal, special emphasis was placed on controlled addition of small amounts of moisture to avoid wet ash handling, so-called "semi-dry processing", which is the basis for several industrial patents [Gasioroski andHrach, 2000, Katsuya et al, 1996], and on the use of ozone, which has recently been found to passivate unburned carbon surfaces in fly ash and thus improve air entrainment properties of problem ash streams [Gao et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

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NOx Control Options and Integration for US Coal Fired Boilers

Bockelie¹,

Davis²,

Linjewile³

et al. 2003

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This is the fourteenth Quarterly Technical Report for DOE Cooperative Agreement No: DE-FC26-00NT40753. The goal of the project is to develop cost effective analysis tools and techniques for demonstrating and evaluating low NO x control strategies and their possible impact on boiler performance for boilers firing US coals. The Electric Power Research Institute (EPRI) is providing co-funding for this program. Using the initial CFD baseline modeling of the Gavin Station and the plant corrosion maps, six boiler locations for the corrosion probes were identified and access ports have been installed. Preliminary corrosion data obtained appear consistent and believable.In situ, spectroscopic experiments at BYU reported in part last quarter were completed. New reactor tubes have been made for BYU's CCR that allow for testing smaller amounts of catalyst and thus increasing space velocity; monolith catalysts have been cut and a small reactor that can accommodate these pieces for testing is in its final stages of construction. A poisoning study on Ca-poisoned catalysts was begun this quarter. A possible site for a biomass co-firing test of the slipstream reactor was visited this quarter. The slipstream reactor at Rockport required repair and refurbishment, and will be re-started in the next quarter. This report describes the final results of an experimental project at Brown University on the fundamentals of ammonia / fly ash interactions with relevance to the operation of advanced NO x control technologies such as selective catalytic reduction. The Brown task focused on the measurement of ammonia adsorption isotherms on commercial fly ash samples subjected to a variety of treatments and on the chemistry of dry and semi-dry ammonia removal processes.iii Table of Our program contains five major technical tasks:• evaluation of Rich Reagent Injection (RRI) for in-furnace NO x control;• demonstration of RRI technologies in full-scale field tests at utility boilers;• impacts of combustion modifications (including corrosion and soot);• ammonia adsorption / removal from fly ash; and • SCR catalyst testing.To date, good progress is being made on the overall program. We have seen considerable interest from industry in the program due to our successful initial field tests of the RRI technology and the corrosion monitor.During the last three months, our accomplishments include the following:• Using the initial CFD baseline modeling of the Gavin Station and the plant corrosion maps, six boiler locations for the corrosion probes were identified and access ports have been installed.• One probe has been collecting data for more than three months and two others have been in service for more than two months; preliminary corrosion data obtained appear consistent and believable.• In situ, spectroscopic experiments at BYU reported in part last quarter were completed; the most significant finding of these investigations was a consistent indication that vanadium does not sulfate during SCR reaction in the presence of gas-phase SO 2 whil...

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