低温等离子体除苯过程中臭氧的演变与作用

Transmutation and effect of ozone generation on benzene removal by low temperature plasma

大气污染物中,挥发性有机化合物(VOCs)已超越NOx和SO2成为排放量最高的气态污染物,对人体健康和环境的影响已引起广泛关注。相比传统去除VOCs的技术,低温等离子体法具有高效率、低能耗、易操作等优势,但有产生臭氧(O3)等副产物的问题。本研究选择苯作为VOCs的代表污染物,采用线管式介质阻挡放电反应器,考察电压、电流等放电参数对苯去除率、副产物臭氧浓度和CO2选择性的影响,重点分析臭氧的演变、机理及其作用。结果表明,影响臭氧浓度的直接因素是输入功率:随着输入功率的上升,苯去除率逐渐上升,臭氧浓度先上升后下降。其原因在于高功率下生成更多低能电子,使得臭氧分解为氧气。等离子体产生的臭氧无法直接氧化苯,但可以氧化苯的中间产物CO完全转化为CO2。

Among the air pollutants,volatile organic compounds(VOCs)have surpassed NOx and SO2 as the highest emission gaseous pollutants,and their impact on human health and the environment has attracted widespread concern.Compared with the traditional VOCs removal technology,the low temperature plasma method has the advantages of high efficiency,low energy consumption,and easy operation.However,it has the problem of by-products such as ozone(O3).Benzene was selected as the representative pollutant of VOCs in this study,and a wire-tube dielectric barrier discharge reactor was used to investigate the effects of discharge parameters such as voltage and current on benzene removal efficiency,by-product ozone concentration,and CO2 selectivity.The transmutation,mechanism and effect of ozone concentration were analyzed.The research results show that the input power is the direct factor affecting the ozone concentration.As the input power increases,the benzene removal efficiency gradually increases,and the ozone concentration first increases and then decreases.The reason is that high power generates more low-energy electrons,which can decompose ozone to produce oxygen.Ozone produced by plasma cannot oxidize benzene directly,but it can convert CO,an intermediate product of oxidized benzene,into CO2 completely.