Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part IX. Effects of volatile-char interactions on char–H2O and char–O2 reactivities
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Volatile-char interactions are an important consideration in the design and operation of a gasifier. This study aims to investigate the effects of volatile-char interactions on the in situ char–steam reactivity at 800 °C and the ex-situ char–O2 reactivity at 400 °C. A Victorian brown coal was gasified in 15% steam at 800 °C in a one-stage novel fluidised-bed/fixed-bed quartz reactor, in which the extent of volatile-char interactions could be controlled. The chars after varying extents of volatile-char interactions and/or varying extents of char conversion in steam were also collected for the measurement of their reactivity with air at 400 °C in a thermogravimetric analyser. Our results show that the char–steam gasification reactions were greatly inhibited by the volatile-char interactions. It is believed that the H radicals generated from the thermal cracking/reforming of volatiles slowed the char gasification in three ways: occupying the char reactive sites, causing the char structure to re-arrange/condense and enhancing the release of catalytic species inherently present in the brown coal. The importance of volatile-char interactions to char–steam reactivity was further confirmed by the char–air reactivity.
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Kajitani, Shiro; Tay, Hui-Ling; Zhang, Shu; Li, Chun-Zhu (2010)Victorian brown coal has high reactivity for gasification because of catalysis of inherent AAEM species. It was, however, found recently that the inhibitory effects of the volatile-char interactions on char gasification ...
Mechanisms and kinetic modelling of steam gasification of brown coal in the presence of volatile–char interactionskajitani, Shiro; Tay, Hui-ling; Zhang, Shu; Li, Chun-Zhu (2013)It is known that Victorian brown coal has higher reactivity for gasification because of catalysis of inherent AAEMspecies than high-rank coal. However, the experimental results of steam gasification of brown coal in a ...
Volatile-char interactions: Roles of in situ volatiles with distinctly-different chemistry in determining char structure and reactivityChen, X.; Wu, Hongwei (2018)© 2018 The Combustion Institute. This study reports the roles of volatiles with distinctly-different chemistry in determining char reactivity and char structure during in situ volatile-char interactions under non-catalytic ...