介质阻挡放电耦合准分子紫外光协同降解类二噁英物质的反应机理

Dielectric Barrier Discharge combined with Excimer Ultraviolet Light (DBD-EUL) has been developed by optimizing DBD setup and experimentally demonstrated as a new method that simultaneously produced plasma at atmospheric pressure and excimer UV radiation at vacuum-pressure with one single power supply. This new device combined simultaneously with plasma and photodissociation shows promise as a new technique to remove dioxin-like compounds from gas streams. This laboratory-scale DBD-EUL device integrates the use of a dielectric barrier discharge (DBD) plasma and ultraviolet radiation to remove dioxin-like compounds such as 4,4’-Dichlorobiphenyl and 3,4’-Dichlorodiphenyl ether. The study mainly emphasize a deep comprehending on the simultaneous removal mechanism of gaseous dioxin-like compounds, the identification and its distributing characteristic of active species generated by DBD-EUL reactor, the effect of DBD-driven ultraviolet wavelength and the energy distribution on synergistic decomposition efficiency of dioxin-like compounds. The influence mechanism of the degradation reactions of 4,4’-Dichlorobiphenyl and 3,4’-Dichlorodiphenyl will be performed under the different I-V features, plasma density, electron temperature, current density and the electron energy distribution. The effects of applied voltage, input current, power frequency, gas flow rate, original concentration as well as the ratio of H2O/O2 mixture on dioxin-like compounds removal efficiency will be aslo investigated. The study results can not only give scientific instructions for the treatment of gaseous dioxin-like compounds, but also give an idea for the disposal of dioxin and brominated dioxin compounds. For the time being, no studies relative to the field were reported.

“DBD耦合准分子紫外光（DBD-EUL）”是在单一DBD基础上，新增一个放电区，并用一个电源同时进行两个区域放电的一种新型放电形式，实现大气压下气体放电产生等离子体和低气压下卤素/惰性气体放电产生准分子紫外光，形成等离子体和光解技术的一体式融合。以类二噁英物质4,4’-二氯联苯和3,4’-二氯二苯醚为研究对象，探讨DBD-EUL协同降解污染物的反应机理，考察放电过程产生的各种活性粒子的形态及其分布特征，紫外辐射波长的类型对协同效应的影响机制，DBD-EUL能量分配及对污染物降解效果的影响机制，I-V特征、等离子体密度、电子温度、电流密度、电子能量分布等对降解反应的影响，并考察外施电压、电源频率、输入功率、介质间距、介质参数及水气、氧气含量等因素对协同作用的影响机制。本项目为DBD-EUL协同降解类二噁英物质提供反应动力学数据和科学依据，也为二噁英及溴代二噁英类物质的降解提供新途径。

本项目以类二噁英代表物氯苯、3,4-二氯二苯醚、4,4-二氯联苯为研究对象，采用介质阻挡放电（DBD）、DBD-催化、DBD诱导UV联合反应器三种类型的反应体系，探究了反应时间、样品初始浓度、外施电压、放电功率、背景气体种类及流速、体系湿度和气体混合比、辐射波长的类型、催化剂种类等因素，对目标物降解率的影响及反应机制，并开展了副产物NOx转化反应研究和垃圾焚烧烟气中的类二噁英物质分解现场中试研究。. 研究结果表明：（1）外施电压或放电功率是影响介质阻挡放电体系或者协同反应体系处理效果的主要因素。但随外施功率的增大，介质阻挡放电诱导无极紫外辐射协同反应的能率会随之降低，单一的DBD反应能率反而略有升高；（2）不同气体氛围对实验结果影响显著，对协同反应起促进作用的为氧活性粒子，有利的气体氛围排序为：氧气>空气>氮气>氩气。同时，对于协同反应管，一定比例的氩气和氧气混合气体的通入更有利于目标物降解，且增加气体湿度也利于污染物降解；（3）单一介质阻挡放电和无极紫外辐射协同反应这二者在主要实验因素的影响趋势差别不大，协同降解反应的效果好于单一介质阻挡放电反应，I2/Xe协同降解效果好于Hg/Ar协同降解反应；（4）在低能量密度条件下，CeO2/Al2O3催化剂和CeO2/CNTs催化剂皆能发挥出较好的效果；而在高能量密度条件下，两者催化辅助效应不明显；（5）DBD耦合MnOx/Al2O3和DBD耦合CuO/Al2O3催化剂反应器均比单DBD具有更好的二氧化碳选择性和目标降解效率；（6）在某垃圾焚烧现场中试结果显示，当二噁英类总量Σ(PCDDs+PCDFs)平均进口浓度0.33 ng/m³时，平均出口浓度为0.078 ng/m³，低于0.1 ng/m³的工业标准设计值，平均降解率为76.4%，且同现有处理手段相比，可使运行成本降低56%。. 本项目提出了一种DBD诱导产生短波长紫外光协同作用于含氯有机物的净化处理新方法，补充和完善了单DBD及DBD-催化反应器降解含氯有机物的降解机制，研究结果可为含氯有机物的分解处理提供科学依据和新途径。