Changes in char reactivity due to char–oxygen and char–steam reactions using victorian brown coal in a fixed-bed reactor

This study was to examine the influence of reactions of char–O2 and char–steam on the char reactivity evolution. A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at 800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation (ex-situ reactivity) using TGA (thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3% O2 in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.

Graphical AbstractThis graph is trying to describe the difference in the reactivity of chars from gasification in low concentration of oxygen and/or steam. It was believed that the coal/char–oxygen reactions were less selective than coal/char–steam reactions. In other words, the steam would preferentially consume some reactive carbon structure in coal or char, leaving more inert carbon structure in char. Thus the chars derived from different gasifying agents have different char structures and show different activities.Figure optionsDownload as PowerPoint slide