Correlations between Coal Compositions and Sodium Release during Steam Gasification of Sodium-Rich Coals

Abstract

Sodium release (SR) during gasification of sodium-rich coals has caused a series of severe operating problems. How to effectively estimate the SR is crucial to design the appropriate controlling technologies. In this work, the detailed correlations between coal compositions and SR, including the underlying mechanisms, were investigated in an atmospheric labscale tube furnace. Six sodium-rich coals were gasified at 900 and 1000 °C under a steam atmosphere. Several coal compositions, such as the content of Na and the mass ratios of Na/Cl, Na/S, Na/ash, and Na/(Si + Al), were correlated with SR. The results indicated that the SR had a close relationship with coal compositions. At both temperatures, the SR presented strongly positive correlations with the Na/(Si + Al) ratio of investigated coals, implying that the inhibiting effect of Si−Al minerals played a dominant role on the SR. However, as a result of the specificity of testing coals and steam atmosphere, the promoting effect of Cl was insignificant. At 1000 °C, it was found that the high content of calcite could notably increase the SR because the generated lime could consume Si−Al minerals, leading to the obvious reduction of captured sodium in the residue. In addition, thermodynamic equilibrium calculations by FactSage have been conducted in comparison to the experimental results.