Changes In Char Structure During The Gasification Of A Victorian Brown Coal In Steam And Oxygen At 800 ℃

摘要

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 ℃ in atmospheres containing 15% H_2O, 2000 ppm O_2, or 15% H_2O 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_2O 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_2O had almost the same features as the chars from the gasification in 15% H_2O 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.