Abstract: The supercritical water gasification of phenolic wastewater without
oxidant was performed to degrade pollutants and produce hydrogen-enriched
gases. The simulated o-cresol wastewater was gasified at 440–650°C
and 27.6 MPa in a continuous Inconel 625 reactor with the residence time of
0.42–1.25 min. The influence of the reaction temperature, residence time,
pressure, catalyst, oxidant and the pollutant concentration on the gasification
efficiency was investigated. Higher temperature and longer residence time
enhanced the o-cresol gasification. The TOC removal rate and hydrogen
gasification rate were 90.6% and 194.6%, respectively, at the temperature of
650°C and the residence time of 0.83 min. The product gas was mainly
composed of H_2, CO_2,
CH_4 and CO, among which the total molar percentage of
H_2 and CH_4 was higher than 50%. The
gasification efficiency decreased with the pollutant concentration increasing.
Both the catalyst and oxidant could accelerate the hydrocarbon gasification at
a lower reaction temperature, in which the catalyst promoted
H_2 production and the oxidant enhanced
CO_2 generation. The intermediates of liquid effluents were
analyzed and phenol was found to be the main composition. The results indicate
that the supercritical gasification is a promising way for the treatment of
hazardous organic wastewater.
