摘要: Lean methane from abandoned coal mines or drainage gas with methane concentration of 1%−3% is in general directly discharged into the atmosphere due to the lack of appropriate technology, which has caused serious environmental concerns due to its high global warming potential. While direct thermal oxidation of ultra-low methane in a flow reversal reactor offers an attractive solution, it poses challenges such as potential explosions and unstable combustion flames. Elucidating the dynamic behavior of thermal oxidation of ultra-low methane in a flow reversal reactor is the basis for practical application. To this end, autothermal operation boundary of a pilot-scale thermal flow reversal reactor was examined and the effects of hot gas withdrawal on the behavior of flow reversal reactor was deeply studied. It was found that autothermal operation can be achieved with a methane content of over 0.2% and heat can be recovered if methane content is over 0.5%. Withdrawal of hot air has a significant impact on the dynamic behavior of the reactor: maximum bed temperature at the pseudo-steady state without hot gas extraction keeps almost constant with methane concentration varying in 0.5%−3.0%; whereas for heat recovery by hot gas withdrawal, the maximum bed temperature increases with the increase of the amount of hot gas extracted, and the allowable hot gas exported from the reactor increases nearly linearly from 12.5% to 32% as the methane content increases from 0.5% to 3.0%. Furthermore, the appropriate switching time decreases with the increase of the amount of hot gas withdrawn; for most cases, reversing flow direction at a time interval of 30−50 s can ensure complete methane conversion and stable bed temperature. Thus, it may be concluded that lean methane (1%−3%) can be mitigated by thermal oxidation without worrying about the bed temperature runaway or explosion.
摘要: A stable metal-organic framework (MOF), MIL-101(Fe), was successfully synthesised using a solvothermal method and employed as a novel photocatalyst for degrading crude oil in oilfield wastewater. Through optimisation of reaction conditions, the following optimal parameters were determined: a dark reaction time of 30 min, a light reaction time of 30 min, a pH of 5.5, a catalyst amount of 150 mg/L, and a reaction temperature of 303.15 K. Under these reaction conditions, an impressive removal of 94.73% was achieved. This study represents the first application of Fe-based MOFs in the photocatalytic degradation of oilfield wastewater. MIL-101(Fe) notably demonstrated excellent stability under mild acid conditions and can be efficiently recycled. These findings offer valuable insights into using MIL-101(Fe) as a promising material for industrial applications in removing crude oil from oil-polluted water through photocatalytic degradation.