Continuous hydrogen generation from lignite in supercritical water

For the production of hydrogen from lignite, a Supercritical Water (SCW) reactor with a coal feed rate of 1kg/h was set up, which was operated with continuous feeding of coal water slurry. The effects of reaction temperature (500℃～650℃), pressure (20MPa~30MPa), slurry concentration (20%~50%) and catalyst loading amount (0%~1% of coal) on the hydrogen generation characteristics were investigated. It is found that there is a notable increase in the hydrogen content and yield with the elevation of the reaction temperature. The hydrogen concentration and yield increase from 11% and 25mL/g coal to 29% and 110mL/g coal when the temperature increases from 500℃ to 650℃. The formation of methane is favored with the increase of reaction pressure. However, the carbon gasification rate and hydrogen yield decrease with the increase of slurry concentration. Moreover, the addition of 0.5% KOH can greatly improve the hydrogen production from high concentration coal water slurry. It is indicated that the reaction temperature and catalyst loading amount have a significant influence on the coal conversion and hydrogen yield, while the effect of pressure is relatively less significant.