Energy & Fuels, Vol.31, No.6, 6435-6444, 2017
Gasification Characteristics and Sodium Transformation Behavior of High-Sodium Zhundong Coal
The Zhundong coalfield is a newly discovered superhuge coal deposit in China. Zhundong coal is considered as a potential resource for gasification, due to its high reactivity. However, the high sodium content in Zhundong coal could cause serious ash-related problems during its thermal utilization. This study was conducted to investigate the gasification characteristics and sodium transformation behavior of a typical high-sodium Zhundong coal. The gasification performance of Zhundong coal is greatly improved at elevated temperature, which is verified by both thermogravimetric analysis and bench-scale study in a bubbling fluidized bed reactor. Compared to Shigouyi coal, Zhundong coal shows better gasification reactivity at the same temperature, indicating better adaptability of Zhundong coal to fluidized bed gasification. Sodium in Zhundong coal chiefly exists as the water-soluble form. The temperature is a crucial parameter affecting the release and transformation of sodium. With increasing, temperature, more sodium is released to the gas phase, primarily in the form of NaCl(g). Sodium in the gasification fly ash mainly exists as NaCl, and a small amount of NaAlSiO4 is also identified, whereas the major crystalline phase of sodium in the bottom ash is NaAlSiO4. The formation of high-melting-point sodium containing NaAlSiO4 is beneficial for mitigation of bed agglomeration problems during high-sodium coal gasification.