Changes in char reactivity and structure during the gasification of a Victorian brown coal: Comparison between gasification in O 2 and CO 2

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Char reactivity is an important factor influencing the efficiency of a gasification process. As a low-rank fuel, Victorian brown coal with high gasification reactivity is especially suitable for use with gasification-based technologies. In this study, a Victorian brown coal was gasified at 800 °C in a fluidised-bed/fixed-bed reactor. Two different gasifying agents were used, which were 4000 ppm O 2 balanced with argon and pure CO 2. The chars produced at different gasification conversion levels were further analysed with a thermogravimetric analyser (TGA) at 400 °C in air for their reactivities. The structural features of these chars were also characterised with FT-Raman/IR spectroscopy. The contents of alkali and alkaline earth metallic species in these chars were quantified. The reactivities of the chars prepared from the gasification in pure CO 2 at 800 °C were of a much higher magnitude than those obtained for the chars prepared from the gasification in 4000 ppm O 2 also at 800 °C. Even though both atmospheres (i.e. 4000 ppm O 2 and pure CO 2) are oxidising conditions, the results indicate that the reaction mechanisms for the gasification of brown coal char at 800 °C in these two gasifying atmospheres are different. FT-Raman/IR results showed that the char structure has been changed drastically during the gasification process.