Mercury capture by native fly ash carbons in coal-fired power plants

James C. Hower, Constance L. Senior, Eric M. Suuberg, Robert H. Hurt, Jennifer L. Wilcox, Edwin S. Olson

Research output: Contribution to journalReview articlepeer-review

246 Scopus citations

Abstract

The control of mercury in the air emissions from coal-fired power plants is an ongoing challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals. The chemistry of the feed coal and the resulting composition of the flue gas enhances Hg capture by fly ash carbons. This is particularly evident in the correlation of feed coal Cl content to Hg oxidation to HgCl2, enhancing Hg capture. Acid gases, including HCl and H2SO2 (at small concentrations) and the combination of HC1 and NO2, in the flue gas can enhance the oxidation of Hg. In this presentation, we discuss the transport of Hg through the boiler and pollution-control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by coal-derived fly ash carbons.

Original languageEnglish
Pages (from-to)510-529
Number of pages20
JournalProgress in Energy and Combustion Science
Volume36
Issue number4
DOIs
StatePublished - Aug 2010

Bibliographical note

Funding Information:
The support of the Spanish Ministry of Science and Education through grant ENE2007-63641 is gratefully acknowledged. Financial support for T. García-Armingol was provided by CSIC (Spanish National Research Council, Spanish Ministry of Science and Education) through grant JAEPre_076. The authors wish to acknowledge the contributions of other current and past members of the research group (R. Hernández, A. Sanz, R. Ichaso, M.A. González, J. Barroso, A. Pina and A. Smolarz) to several of the studies mentioned here as well as the help of S. Lipari with the editing of some parts of this work. We are most grateful to many other authors for granting permission to use their work and for providing original illustrations.

Keywords

  • Coal
  • Fly ash
  • Mercury
  • Pollution control
  • Unburned carbon

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology

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