Roles of inherent metallic species in secondary reactions of tar and char during rapid pyrolysis of brown coals in a drop-tube reactor

Hayashi Jun-Ichiro, Masahiro Iwatsuki, Kayoko Morishita, Atsushi Tsutsumi, Chun Zhu Li, Tadatoshi Chiba

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Abstract

Two pairs of raw and acid-washed coal samples were prepared from Yallourn and Loy Yang brown coals, and subjected to rapid pyrolysis in a drop-tube reactor at 1073-1173 K in a stream of N2 or H2O/N2 mixture. Examinations were made on the roles of the inherent metallic species in the secondary reactions of nascent tar and char that were formed by the intraparticle primary reactions. The experimental results revealed that the inherent metallic species were essential for vary rapid steam reforming/gasification of the nascent tar/char and simultaneous suppression of soot formation. In the absence of the metallic species, the soot formation from the tar accounted as much as 15-19 and 6-13% of the carbon in coal in N2 and H2O/N2, respectively. The metallic species reduced the yield of soot to 6-8% in N2 by enhancing the reforming of tar by H2O generated from the pyrolysis of coal. In the H2O/N2 stream, instead of soot formation, a net gasification conversion up to 17% within 4.3 s was observed in the presence of the metallic species as a result of catalytic gasification of the nascent char. Moreover, the metallic species catalyzed the steam reforming of the nascent tar, giving its conversion up to 99%. Over the range of the conditions employed, a one-to-one stoichiometry was established between the steam consumption and the yield of carbon oxides formed by the steam reforming/gasification and water-gas-shift reaction.

Original languageEnglish
Pages (from-to)1977-1987
Number of pages11
JournalFuel
Volume81
Issue number15
DOIs
Publication statusPublished - Oct 1 2002

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Tars
Coal
Tar
Lignite
Soot
Pyrolysis
Gasification
Steam reforming
Carbon
Water gas shift
Steam
Reforming reactions
Stoichiometry
Oxides
Acids

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry

Cite this

Roles of inherent metallic species in secondary reactions of tar and char during rapid pyrolysis of brown coals in a drop-tube reactor. / Jun-Ichiro, Hayashi; Iwatsuki, Masahiro; Morishita, Kayoko; Tsutsumi, Atsushi; Li, Chun Zhu; Chiba, Tadatoshi.

In: Fuel, Vol. 81, No. 15, 01.10.2002, p. 1977-1987.

Research output: Contribution to journalArticle

Jun-Ichiro, Hayashi ; Iwatsuki, Masahiro ; Morishita, Kayoko ; Tsutsumi, Atsushi ; Li, Chun Zhu ; Chiba, Tadatoshi. / Roles of inherent metallic species in secondary reactions of tar and char during rapid pyrolysis of brown coals in a drop-tube reactor. In: Fuel. 2002 ; Vol. 81, No. 15. pp. 1977-1987.
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AB - Two pairs of raw and acid-washed coal samples were prepared from Yallourn and Loy Yang brown coals, and subjected to rapid pyrolysis in a drop-tube reactor at 1073-1173 K in a stream of N2 or H2O/N2 mixture. Examinations were made on the roles of the inherent metallic species in the secondary reactions of nascent tar and char that were formed by the intraparticle primary reactions. The experimental results revealed that the inherent metallic species were essential for vary rapid steam reforming/gasification of the nascent tar/char and simultaneous suppression of soot formation. In the absence of the metallic species, the soot formation from the tar accounted as much as 15-19 and 6-13% of the carbon in coal in N2 and H2O/N2, respectively. The metallic species reduced the yield of soot to 6-8% in N2 by enhancing the reforming of tar by H2O generated from the pyrolysis of coal. In the H2O/N2 stream, instead of soot formation, a net gasification conversion up to 17% within 4.3 s was observed in the presence of the metallic species as a result of catalytic gasification of the nascent char. Moreover, the metallic species catalyzed the steam reforming of the nascent tar, giving its conversion up to 99%. Over the range of the conditions employed, a one-to-one stoichiometry was established between the steam consumption and the yield of carbon oxides formed by the steam reforming/gasification and water-gas-shift reaction.

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