CO₂ gasification performance and alkali/alkaline earth metals catalytic mechanism of Zhundong coal char

Gasification is generally considered as the most effective for low rank coal exploitation, and CO₂ gasification offers the advantage of upgrading a greenhouse gas. Herein, the effects of alkali and alkaline earth metals on gasification of char derived from Zhundong low rank coal (R-char) were investigated using a thermo-gravimetric analyzer (TGA). Additionally, the characteristics of chars were analyzed by X-ray fluorescence (XRF) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results show that the carbon conversion increases as the temperature and CO₂ concentration increases. The R-char possesses a higher gasification rate and carbon conversion than the acid washing R-char (AR-char). It can be explained that the alkali and alkaline earth metals presence in coal char can remarkably facilitate the compound's decomposition and make more char surface exposure to react during the gasification process. For the kinetic analysis, the volumetric reaction model reveals a proper description among the three models (VRM, RPM, SCM), and the R-char and AR-char presents a compensation effect in VRM. Besides, the detailed correlation of two chars is ln (k₀)=0.10 E_A−1.77 (R-char) and ln (k₀)=0.10 E_A−2.85 (AR-char), respectively.