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Title: Regimes of association of arsenic and selenium during pulverized coal combustion

Abstract

A suite of six coals, of widely differing As, Se, Ca, Fe, and sulfur contents, was burned under self-sustaining conditions in a 17 kW downflow laboratory combustor. Size segregated ash-laden aerosol samples were isokinetically withdrawn and collected on a Berner low pressure impactor. Correlations between trace element concentration (As or Se) and that of major elements (as functions of particle size) were then used to infer chemical associations between trace metals and Ca and/or Fe, and how these depended on sulfur. These baseline data led to formation of the following hypotheses, namely: (1) dominant As and Se partitioning mechanisms depend on the availability of Ca and/or Fe active sites for surface reaction; (2) increasing combustion temperature increases the availability of active cation sites, and increases partitioning of As and Se to fly ash by surface reaction; (3) sulfur competes with these surface reactions, decreasing As and Se partitioning to fly ash surfaces. These hypotheses were tested by manipulating the As, Se, Ca, Fe, and S contents for various coals by doping. Temperature was adjusted in order to achieve comparisons of different coals and different coal constituents at similar thermal conditions, through O{sub 2} and CO{sub 2} addition, as required. Thesemore » results confirmed the hypotheses above, and allowed an association regime map to be constructed. This map shows that both As and Se associate with Fe and Ca, provided active sites are available. Se reacts preferentially with Fe over Ca when both are available while As reactions with both Fe and Ca are comparable. Sulfur can prevent association of both As and Se, by preferentially reacting with active sites, especially those on Fe. When sufficient sites are not available, the release of vapor-phase As and Se species is promoted. 23 refs., 4 figs., 4 tabs.« less

Authors:
;  [1]
  1. University of Arizona, Tucson, AZ (United States). Department of Chemical and Environmental Engineering
Publication Date:
OSTI Identifier:
20905880
Resource Type:
Journal Article
Journal Name:
Proceedings of the Combustion Institute
Additional Journal Information:
Journal Volume: 31; Journal Issue: 2; Conference: 31. international symposium on combustion, Heidelberg (Germany), 5-11 Aug 2006; Other Information: wendt@eng.utah.edu; Journal ID: ISSN 1540-7489
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL; PULVERIZED FUELS; COMBUSTION; ARSENIC; SELENIUM; TRACE AMOUNTS; CALCIUM; IRON; PARTITION; FLY ASH; PARTICLE SIZE; SULFUR; COAL RANK

Citation Formats

Seames, Wayne S, and Wendt, Jost O.L. Regimes of association of arsenic and selenium during pulverized coal combustion. United States: N. p., 2007. Web. doi:10.1016/j.proci.2006.08.066.
Seames, Wayne S, & Wendt, Jost O.L. Regimes of association of arsenic and selenium during pulverized coal combustion. United States. https://doi.org/10.1016/j.proci.2006.08.066
Seames, Wayne S, and Wendt, Jost O.L. 2007. "Regimes of association of arsenic and selenium during pulverized coal combustion". United States. https://doi.org/10.1016/j.proci.2006.08.066.
@article{osti_20905880,
title = {Regimes of association of arsenic and selenium during pulverized coal combustion},
author = {Seames, Wayne S and Wendt, Jost O.L.},
abstractNote = {A suite of six coals, of widely differing As, Se, Ca, Fe, and sulfur contents, was burned under self-sustaining conditions in a 17 kW downflow laboratory combustor. Size segregated ash-laden aerosol samples were isokinetically withdrawn and collected on a Berner low pressure impactor. Correlations between trace element concentration (As or Se) and that of major elements (as functions of particle size) were then used to infer chemical associations between trace metals and Ca and/or Fe, and how these depended on sulfur. These baseline data led to formation of the following hypotheses, namely: (1) dominant As and Se partitioning mechanisms depend on the availability of Ca and/or Fe active sites for surface reaction; (2) increasing combustion temperature increases the availability of active cation sites, and increases partitioning of As and Se to fly ash by surface reaction; (3) sulfur competes with these surface reactions, decreasing As and Se partitioning to fly ash surfaces. These hypotheses were tested by manipulating the As, Se, Ca, Fe, and S contents for various coals by doping. Temperature was adjusted in order to achieve comparisons of different coals and different coal constituents at similar thermal conditions, through O{sub 2} and CO{sub 2} addition, as required. These results confirmed the hypotheses above, and allowed an association regime map to be constructed. This map shows that both As and Se associate with Fe and Ca, provided active sites are available. Se reacts preferentially with Fe over Ca when both are available while As reactions with both Fe and Ca are comparable. Sulfur can prevent association of both As and Se, by preferentially reacting with active sites, especially those on Fe. When sufficient sites are not available, the release of vapor-phase As and Se species is promoted. 23 refs., 4 figs., 4 tabs.},
doi = {10.1016/j.proci.2006.08.066},
url = {https://www.osti.gov/biblio/20905880}, journal = {Proceedings of the Combustion Institute},
issn = {1540-7489},
number = 2,
volume = 31,
place = {United States},
year = {Sun Jul 01 00:00:00 EDT 2007},
month = {Sun Jul 01 00:00:00 EDT 2007}
}