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 ...
Effects of volatile–char interactions on in-situ destruction of nascent tar during the pyrolysis and gasification of biomass. Part II. Roles of steamSong, Yao; Wang, Yi; Hu, Xun; Xiang, J.; Song, H.; Mourant, Daniel; Li, Tingting; Wu, Liping; Li, Chun-Zhu (2015)This study aims to investigate the importance of steam to tar destruction during the volatile–char interactions. Steam was supplied in the absence and presence of nascent char during the pyrolysis/gasification of biomass ...