Oxy-fuel combustion of millimeter-sized coal char: Particle temperatures and NO formation

Jacob Brix, Leyre Gómez Navascués, Joachim Bachmann Nielsen, Peter Løvengreen Bonnek, Henning Engelbrecht Larsen, Sønnik Clausen, Peter Glarborg, Anker Degn Jensen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In this work, differences in particle temperature and NO yield during char oxidation in O2/N2 and O2/CO2 atmospheres, respectively, have been examined. A laboratory scale fixed bed reactor, operated isothermally at 1073 K, was used for combustion of millimeter-sized lignite and bituminous coal char particles in 5–80 vol.% O2. Experiments were carried out with both single particles of different sizes (1.3–543 mg) and multiple particles (30–50 mg). Particle temperatures and structural changes were recorded by a Charged Coupled Device (CCD) camera during the experiments. The particle surface temperatures increased with mass loading, by as much as 700 K above the furnace set point. The formation of NO from lignite char was not influenced by the change from N2 to CO2 whereas the NO yield from bituminous coal char was considerably lower in O2/CO2 compared O2/N2. For both chars the conversion to NO decreased as the O2 concentration or the particle size increased. However, for the bituminous coal char, a peak in NO yield was observed at an intermediate particle size of 0.1–0.2 g. The differences in the effect of gas atmosphere, O2 concentration, and particle mass on the NO yield from oxidation of bituminous coal char and lignite char, respectively, cannot be fully explained. Char/NO interactions appear to be quite complex, and mineral catalysis and release to the gas-phase of volatile N-species such as HCN, either from secondary pyrolysis or as a product of the char–N + O2 reaction, may play a role.
Original languageEnglish
JournalFuel
Volume106
Issue number0
Pages (from-to)72-78
ISSN0016-2361
DOIs
Publication statusPublished - 2013

Keywords

  • Oxy-fuel
  • Combustion
  • CCD camera
  • Particle temperature
  • NO

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