Catalytic hydrogen production from municipal sludge in supercritical water with partial oxidation

This paper describes partial oxidative gasification of municipal sludge with NaOH catalyst, using a batch type reactor. Hydrogen peroxide was employed as oxygen source. The reaction is studied in the ranges of 623-723 K, 23-28 MPa and various reaction time 5-40 min. We found that sludge at low concentrations can be completely gasified and no char or tar was observed. Gaseous products were composed of H₂, CO₂, CO, CH₄, and so on. The improvement of gasification efficiency by partial oxidation was accompanied with high yield of hydrogen and carbon monoxide. The effect of partial oxidation was investigated. For comparison, we also conducted the experiments without catalyst at the same conditions. The yield of hydrogen with NaOH was almost twice as much as that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of sludge to produce H₂. The catalytic effect of NaOH was the inhibition of char formation and promotion of CO yields and thus H₂ by water-gas shift reaction.