【作者】 陈杰；

【导师】 施耀；

【作者基本信息】 浙江大学 ， 环境工程， 2011， 博士

【摘要】 现代工业的快速发展也使每年排入环境的有毒有害废气大幅增加,尤其是挥发性有机废气(VOCs)的排放,严重干扰居民的日常生活,恶化人们的生存环境,进而对人体健康和生态环境造成危害。低温等离子体技术工艺流程简单、开停方便、运行费用低、去除效率高,在VOCs治理上具有明显优势,是国内外目前的研究热点之一。本论文采用高压脉冲电源和线筒式介质阻挡反应器对甲硫醚在空气中的降解情况、背景气对甲硫醚降解的影响和等离子体+吸附复合技术降解甲硫醚做了基础研究；对皮革厂产生的VOCs废气进行实验室小试；建立光电一体化去除木业行业喷漆VOCs废气示范工程。论文取得以下主要结论：(1)在本实验条件下,甲硫醚去除率随着峰值电压、脉冲频率、停留时间的增加而提高。甲硫醚初始浓度过高会导致去除率的下降,但是在出气达标的情况下,适当增加初始浓度有利于提高能量利用率。在本体系中,甲硫醚由等离子体反应器降解后的主要副产物是O3、NOx、SO2。甲硫醚的初始浓度增加可以降低出气中O3、NOx的含量,SO2浓度则会提高。在较高峰值电压下,出气中SO2选择性会提高。流量为1000mL/min,甲硫醚初始浓度为832mg/m3,峰值电压为40kV时,甲硫醚去除率为100%,SO2选择性为70%。(2)甲硫醚的浓度一定时,在不同的背景气中,等离子体反应器的起晕电压均与总气压成正比。当甲硫醚浓度为832mg/m3,标准大气压下,本实验中反应器的起晕充电电压为2.4kV。在相同的峰值电压下,甲硫醚在介电常数小的背景气中容易降解。等离子体环境下,背景气中不同的湿度条件对甲硫醚的降解有较大影响。适当的湿度可以提高去除率和能量利用率。本实验的最佳湿度为0.3vol%。O2在等离子体降解甲硫醚的过程中具有重要作用。O2在高能电子和自由基的作用下生成具有强氧化性的O3和含氧自由基,促进甲硫醚的降解。背景气中O2含量直接决定副产物O3、NOx、SO2的生成量。当背景气中O2含量为5%时,甲硫醚去除率较高,同时副产物O3、NOX、SO2生成量相对较少。(3)峰值电压和初始浓度是影响皮革废气(主要成分二甲胺)去除率和能量利用率的重要因素。在峰值电压为41.25kV时,761mg/m3的二甲胺去除率可达100%；高的氧气含量可促进含氧活性粒子的生成,从而提高二甲胺的去除率；背景气中的高湿度会增加等离子体反应器中OH自由基的浓度,抑制臭氧生成,从而影响二甲胺的去除效果。在实验条件下,0.3vo1%为低温等离子体降解二甲胺的最佳湿度；低温等离子体降解二甲胺和甲硫醚混合废气时存在协同作用,可以提高去除率、能量利用率并减少副产物生成,总污染物的能量利用率从2.13mg/kJ提高到5.20mg/kJ。(4)吸附饱和甲硫醚的活性炭在介质阻挡放电区域内可以有效再生,活性炭经过4次再生后再生效率保持在90%以上。活性炭再生效率随着等离子体反应器中能量密度的增加而提高。在本实验条件下,背景气中含有适当的湿度可以促进活性炭的再生。另外,背景气中低氧气含量(≤5vo1%)对活性炭再生起促进作用,而高氧气含量(>5vo1%)起抑制作用。活性炭在低温等离子体再生过程中比表面积和微孔孔容增加,但是持续的再生过程会引起活性炭表面结构坍塌和微孔堵塞,从而降低活性炭对甲硫醚的吸附能力。同时介质阻挡放电过程也会削弱活性炭对甲硫醚的亲和力。(5)活性炭协同介质阻挡放电能显著提高甲硫醚去除率。湿度极大地影响甲硫醚在活性炭协同低温等离子体体系中的降解。在20℃时,25%的相对湿度最有利于促进甲硫醚去除。活性炭协同等离子体可以有效控制出气中的副产物。在合理的能量密度下,等离子体会改变活性炭表面性质,使活性炭长时间保持吸附活性。(6)低温等离子体与紫外光催化技术相结合可以有效去除木业家具厂产生的喷漆VOCs废气,最终实现VOCs废气达标排放。更多还原

【Abstract】 With the industry developing, the emission of hazardous gasous pollutants grows fast, especially the emission of volatile organic compounds (VOCs), which causes detrimental influences on both human health and global environment. Non-thermal plasma (NTP) techniques have great industrial potential for VOCs removal with relatively low power consumption and high removal efficiency. At present, many researches have been focused on NTP techniques applying in VOCs control. In this study, a wire-cylinder dielectric barrier discharge (DBD) reactor was adopted to investigate the decomposition of dimethyl sulfide (DMS), the influence of balance gas on decomposition of DMS and decomposition of DMS by NTP+activated carbon (AC). A laboratory scale experiment on removal of leather industrial waste gas was carried out. A demonstration project on spray painting VOCs control by NTP techniques was established. The main conclusions of this paper are as follows:(1) Under the experimental condition, the conversion of DMS increases with a increasemnt of peak voltage, pulse frequency and resident time. High initiate concentration causes a reduction of DMS conversion. However, energy cost decreases with increasing of the initial DMS concentration. In the cases of DMS removal, the main byproducts are NOx, SO2 and O3. The concentration of O3 and NOX in outlet gas decreases and SO2 concentration increases with an increasement of the initial DMS concentration. The selection of SO2 is enhanced at a higher peak voltage. High energy electrions and free radicals play important roles in decomposition of DMS in NTP.(2) The breakthrough voltage of DMS in Ar is lower than that of DMS in N2, both of which are proportional to the gas pressures. The breakthrough voltage in this DBD reactor with DMS in air is 2.4 kV at a 1 atm. At a fixed peak voltage, DMS in smaller dielectric strength balance gas is easier to decomposition by NTP. The humidity in balance gas strongly affects DMS decomposition by NTP. Proper humidity improves conversion and energy efficiency. The highest DMS removal efficiency is achieved with the gas stream containing 0.3 vol% H2O in air. Oxygen plays an important role in decomposition of DMS in NTP. Oxygen reacts with high energy electrons to form O3 and O radical, resulting in boosting DMS decomposition. The presence of O2 in balance gas determines the amount of NOx, SO2 and O3 produced.5% oxygen is the optimum concentration in decomposition of DMS, due to relatively higher conversion of DMS and fewer yields of O3, NOx and SO2.(3) Peak voltage and initial dimethylamine (DML) concentration are important factors that influence the DML removal efficiency and energy yield. The conversion of DML of 761 mg/m3 reaches 100% at a peak-voltage of 41.25 kV. Higher oxygen content (0-21%) promotes production of active species such as ozone, leading to higher DML conversion. Humidity enhances the amount of OH radicals and inhibits ozone production in reactor, which codetermines the optimum humidity of 0.3% under the experiment conditions (0-0.8%). When DML and DMS were decomposed together, synergistic actions exist in the processes, leading to higher conversion, higher energy yield and less byproducts formation. The energy yield is promoted from 2.13 to 5.20 mg/kJ.(4) The DMS exhausted AC is regenerated efficiently in the discharge zone by DBD. The regeneration efficiency keeps above 90% after 4 regeneration cycles. The regeneration efficiency increases with the energy density increasing. Under the experimental conditions, an appropriate humidity level in balance gas promotes AC regeneration. A promoting effect of low O2 concentration (<5%) and a adverse effect of high O2 concentration (>5%) on AC regeneration are obtained in the study. DBD process can make surface area, pore volume of AC increase. And successive AC regeneration processes cause wall destruction and pores blockage, resulting in reduction of adsorption capacity. Surface chemistry of AC also plays an important role in adsorption capacity. Increasing carboxylic groups produced by DBD weakens the affinity of DMS toward the surface of AC.(5) NTP assistanted by AC can improve DMS conversion dramasticly. The humidity in balance gas strongly influences DMS decomposition by NTP+AC system.25% of relative humidity is optimum for DMS decomposition in NTP+AC system. NTP+AC system can effectively control the byproducts. NTP at a propriate energy density can modify AC surface and keep AC adsorbable for long term. (6) NTP combined UV can efficiently remove spray painting VOCs. In demonstration project, the emission of waste gas from plant reaches the standard after treatment.更多还原