Changes in Char Structure during the Gasification of a Victorian Brown Coal in Steam and Oxygen at 800 °C

Char structure is an important factor influencing its reactivity during gasification. This study aims to investigate the changes in char structure during the gasification of brown coal. A Victorian brown coal was gasified in a fluidized-bed/fixed-bed reactor at 800 degrees C in atmospheres containing 15% H(2)O, 2000 ppm O(2), or 15% H(2)O and 2000 ppm O(2), respectively. Although the char gasification in 2000 ppm O(2) was mainly rate-limited by the external diffusion Of O(2), the char-H(2)O reaction was mainly rate-limited by the chemical reactions. The structural features of char at different levels of char gasification conversion were examined with FT-Raman spectroscopy. Our results show that the chars from the gasification in the mixture of 2000 ppm O(2) and 15% H(2)O had almost the same features as the chars from the gasification in 15% H(2)O alone when the same levels of char conversion were achieved. Both the thermal decomposition of char and the char gasification reactions could result in changes in char structure during gasification.