Experimental study on the catalytic supercritical water oxidation of oilfield sludge

Oilfield sludge is a kind of hazardous waste. In this study, supercritical water oxidation (SCWO) was used to treat oilfield sludge. The effect of operating parameters was investigated, including temperature (390-450 degrees C), reaction time (5-30 min), oxidation coefficients (OC, 1.0-5.0) and Ni/Al2O3 catalyst. The experimental results showed that higher temperature and higher oxidation coefficient favored the degradation of oilfield sludge. Carbon in oilfield sludge was mainly converted to gas phase, for instance, 63.6% of carbon was converted to gas at 5.0 OC, 20 min and 450 degrees C without catalyst. The removal efficiency of total organic carbon (TRE) could be up to 96.0% at 450 degrees C, 20 min, and 4.0 OC without catalyst. Furthermore, the addition of Ni-based catalysts could also improve TRE. TRE and carbon conversion efficiency (CE) were 95.2% and 68.2% at 1.5 OC, 20 min and 450 degrees C with 20Ni/Al catalyst addition, respectively, which were higher than that of without catalyst (89.5% and 33.8%). The characterization and regeneration of catalyst were also carried out. Catalyst Ni/Al2O3 had good reliability, the TRE of 92.5% and the catalytic recovery efficiency of 52.6% were observed after three cycles.

Automated summary

In this study, SCWO was used to treat oilfield sludge, with higher temperature and oxidation coefficient found to favor the degradation of sludge. The addition of Ni/Al2O3 catalyst further improved the removal efficiency of total organic carbon.