Variation of carbon crystalline structures and CO2 gasification reactivity of Shenfu coal chars at elevated temperatures

When the carbon crystalline structures of Shenfu coal chars were analyzed by XRD, they could be divided into two components with a relatively poor crystalline structure component (P component) and a relatively good crystalline structure component (G component). During the elevated temperature pyrolysis, a more prolonged thermal history and a higher pyrolysis temperature resulted in a larger fraction of the G component and the P component, respectively, and the graphitization of Shenfu coal chars was not quite easy. During the gasification, the consumption of the P component was larger than that of the G component. Besides, the CO2 gasification reactivity of Shenfu coal chars was also investigated by an isothermal thermogravimetric analysis at the ambient pressure and gasification temperatures of 950-1400 degrees C. The pyrolysis heating rate had a significant effect on the reactivity of resulting chars, which was that the gasification activity of rapid pyrolysis chars was. higher or several times higher than that of slow pyrolysis chars. As the gasification temperature was elevated, the reactivity of coal chars increased, while the increasing extent of the reactivity of coal chars was smaller and smaller above the ash fusion temperature and even almost unchanged in the higher temperature range. The rate-controlling step of the gasification reaction changed gradually from the chemical reaction in the low temperature range (950-1150 degrees C) to the gas diffusion in high temperature range (1150-1400 degrees C).