Hydrogen production by Zhundong coal gasification in supercritical water

The high sodium content of Zhundong coal restricts its application in direct combustion and supercritical water gasification is a promising clean and efficient coal conversion technology. To obtain the gasification and sodium distribution characteristics of Zhundong coal in supercritical water, experimental investigations were conducted in autoclaves and supercritical water fluidized bed reactors. The experimental results showed that as the concentration of Zhundong coal slurry decreased or the residence time increased, more sodium was released from the solid phase in autoclaves. Carbon gasification efficiency of more than 95% was obtained with the coal slurry of 30 wt%∼40 wt% in the fluidized bed reactor. Less than 0.07% sodium was released from the reactor, in other words, most of the sodium remaining could be collected and caused no pollution and fouling problems for downstream process. Supercritical water fluidized bed reactor appeared to be a promising reactor for supercritical water gasification of Zhundong coal.