Hydrogen production from lignite via supercritical water in flow-type reactor

A supercritical water reactor with throughput of 10  kg/h was set up, which was operated with continuous feeding of coal water slurry. The effects of reaction temperature (500–650 °C), pressure (20.0–30.0 MPa), Ca/C molar ratio (0–0.45) and O/C molar ratio (0–0.35) on the hydrogen generation characteristics were investigated. It is found that there is a notable increase in the hydrogen content and yield with the increase of reaction temperature. The hydrogen yield increases from 24.67 ml/g to 135.73 ml/g when the temperature increases from 500 °C to 650 °C. The contents of CO2 in gas product decrease, while that of hydrogen increases with the increase of Ca/C molar ratio. At Ca/C molar ratio of 0.45, nearly all CO2 is fixed. Correspondingly, the content of hydrogen in gas is 73.29%, and the yield of hydrogen is 348.30 ml/g compared to 135.42 ml/g in the absent of CaO. Moreover, both of CaO and KOH catalyze gasification and water-shift reaction. The formation of hydrogen and the carbon gasification efficiency are improved by the added H2O2 when O/C ratio is less than 0.3.