【作者】 黄丽萍；

【导师】 朱益民；

【作者基本信息】 大连海事大学 ， 环境科学， 2010， 博士

【摘要】 本文系统研究了以线极为高压极的电晕放电伏安关系,确定采用以针板式直流电晕放电为核心技术研制成空气净化单元。以室内空气净化为研究目标,针对空气中的颗粒物、细菌与病毒及气态污染物三大污染进行去除实验及应用试验研究。通过条件实验确定优化的电极结构及运行参数、探索分析各污染物的去除机理；并在此基础上进行封闭空间内的净化试验。研制成可实用的空气净化器,使得最终能够在室内空气净化中同时、一体、且高效净化颗粒物、致病细菌和病毒、及气态污染物。室内空气污染物呈多元性,主要包括颗粒物污染,微生物污染、挥发性有机化合物污染及其他化学污染,这些污染物之间还具有交叉作用。目前主要净化技术包括过滤、静电收尘、臭氧等,但在可处理污染物颗粒大小、处理效率、处理毒害气体及杀菌的广普性和一体性方面,已无法满足要求。电晕放电非热等离子体和光催化剂结合被视为在空气净化中具有更多优势,分别对这两种技术进行综述,提出发展以电晕放电引发的等离子体技术和光催化技术联合为核心的净化器。系统研究以线极为发射极的不同构型直流电晕放电的伏安关系,根据实验得到的外加电压及放电电流值,对各构型下的电晕放电伏安关系式进行推导得到线发射极电晕放电伏安关系式为I=AV2(V-Vc)/L[R/ln(R/r0)]2。对结果进行理论分析,认为电晕放电的迁移区中形成电流的是正离子和/或负离子；且由c-V曲线可区分电晕放电的阶段：起始阶段、稳定阶段及预击穿过渡阶段。相对于单极电晕放电,双极电晕放电的迁移区中离子密度均倍增,且推知其电离区中电子密度也相应倍增；迁移区中正负离子的复合可以忽略,且双极电晕放电中正负电晕放电间存在相互电离作用。考虑到在可注入能量密度及放电稳定性方面针极电晕放电优于线极电晕放电,选择优化的针极电极结构作为空气净化的放电反应器。以可吸入颗粒物为研究对象,采用研制的空气净化单元进行一次通过处理实验,得到电晕放电捕集可吸入颗粒物的效率η随颗粒物粒径Dp的增大而增大,随风量Q的减小而增大；CADR随Q和Dp的增大显著提高。通过理论分析,定性揭示高效捕集可吸入颗粒物的规律。在此基础上,进行悬浮颗粒物和可吸入颗粒物捕集的室内应用试验,结果表明能快速有效的将较高初始浓度的悬浮颗粒物净化至达到国家标准；较低浓度的情况下下降一个数量级；对不同粒径的可吸入颗粒物具有高效捕集率及洁净空气量值。针板式电晕放电双极电晕放电净化装置对粒径≤1μm的细小颗粒物比单级放电具有更好的处理效果。证明该净化单元具有快速高效去除室内空气中的悬浮颗粒物及可吸入颗粒物、高洁净空气量等优点。以空气中细菌为研究对象,采用研制的空气净化单元进行一次通过处理实验,结果表明杀菌效率随消毒时间延长和放电电压增高而增高；处理风量越小,杀菌效果越好。得到放电场中的最优风速及单位放电体积对应最优风量。探讨细菌的消毒机理,认为电晕放电杀灭空气自然菌的过程中,高能电子和活性粒子起主导作用。细菌消毒的室内应用试验结果表明在室内自然菌严重污染的条件下,非热放电净化器处理30min后达到国家标准；处理60min后达到卫生部版标准Ⅲ类区域的洁净度要求。对常见的副流感病毒及单纯疱疹病毒进行灭活实验,证实针阵列对板电晕放电能快速、高效灭活空气中PIV和HSV-I病毒。认为放电产生的紫外光、高能电子和自由基的共同作用是灭活PIV和HSV-I病毒的主因。分别发生较高浓度的多种气态污染物,模拟封闭室内气态污染物污染,采用针阵列对板电晕放电发生装置为核心的空气净化单元进行净化试验。结果显示,本净化装置对气态污染物具有广普的净化作用；净化效率和速率优于目前同类的优质空气净化器产品,其净化作用具有高效性。较细致研究本净化装置对典型室内甲醛污染的净化效果,运行风量和放电功率较大时有利于甲醛去除；正电晕放电效果优于负电晕放电。定性解释甲醛去除机理、分析自由基反应过程。最后采用提出的非热放电结合光催化作用方式PPC,以燃烟燃烧产生的污染气体为研究对象,一次通过净化装置,通过比较NTP和PPC作用方式的实验结果,分析作用规律。确证PPC方式具有协同净化效应,原因为在高压强电场、电子、离子和紫外的共同作用下同时发生等离子体化学反应和光催化反应。更多还原

【Abstract】 This thesis systematically studied the voltage-current relationship in DC corona discharge with wire electrode as the emitting electrode and adopted an indoor air cleaning unit having its core technology characterized by needle-plate DC corona discharge. Taking indoor air purification as the principal goal, removal experiments and application tests aiming at suspended particles/inhalable particles capture, airborne bacteria and virus sterilization, and harmful chemical pollutant gases purification were carried out respectively. According to the conditional experiments results, optimized electrode structure and running parameters were determined, the rules were discussed and the mechanisms were analyzed. Based on the above results, the purification tests were carried out in closed rooms. Finally the air cleaner has advantages of simultaneous, integrated and efficiently removal of particles, pathogenic bacteria and virus, and harmful gases.It has been summarized that indoor air pollution is complicated, mainly including particle pollution, microorganism pollution, volatile organic compounds and other chemical pollution. What’s more, these pollutions have cross actions in ambient air. Current purification technologies mainly include infiltration, electrostatic collection, ozone sterilization, and etc. However, these technologies are undesirable in respect of small-size particle capture, treatment efficiency, extensiveness of harmful gases and bacteria and virus, and integrated capability of removing complicated pollutants. The development tendency shows that non-thermal plasma induced by corona discharge combining photo-catalyst has more advantages in indoor air purification. Thus, these two technologies were introduced, and finally an air cleaner featured with these two technologies was proposed.The voltage-current characteristics of corona discharge in emitting wire electrode configuration were studied systematically. According to the current and voltage values under different experiment conditions, the relationship of current and voltage was deduced as I=AV2(V-Vc)/L[R/ln(R/r0)]2 in corona discharge in emitting wire electrode configuration. Theoretical analysis was made and it was believed that the positive and/or negative ions form the current in migration area. The c-V curves provided evidence for distinguish the discharge stages as initial stage, stable stage and transitional stage to pre-breakdown. Compared to unipolar discharges, the ion concentrations of migration area are doubled in bipolar discharges; and the electron concentrations in ionization area are also doubled. The recombination of positive and negative ions can be neglected. Considering greater injective energy density and better discharge stability of corona discharge in emitting needle electrode than in wire electrode, the optimized discharge reactor of needle electrode was determined to be the core unit in the air cleaner.This new air cleaning unit was used to capture inhalable particles (Ips) in air when it was passed through the discharge reactor for one time. The results showed that better capture efficiency of IPs by corona discharge was obtained with an increase in the size of particle diameters Dp and decrease in the air flow rates Q. The values of CADR significantly increased with an increase in both Dp and Q. The reasons why this unit possessed higher capture efficiency were revealed by theoretical analysis. Then the indoor applicatio tests for suspended particle capture and IPS removal were carried out based on above study. It was indicated that the concentration of suspended particles would meet the national standard in short treatment time when initial concentration was high; and when initial concentration was low, it also would be decreased by one magnitude. Desirable capture efficiencies and CADR values of IPS with different diameter ranges were obtained. Compared to unipolar discharge, needle-plate bipolar corona discharge had better treatment result for IPs whose size was less than 1μm. It was proved that the cleaning unit was characterized by rapid and efficient capture of suspended particles and IPs and desirable CADR value.The airborne bacteria were sterilized by this air cleaning unit when the air was passed through the discharge reactor for one time. Results showed that the sterilization efficiency is increased with an increase in treatment time and applied voltage. The smaller the air flow rate was, the better the sterilization effect would be obtained. The optimal air velocity in discharge field and corresponding optimal air flow rate per unit volume of the reactor was determined. In addition, the sterilization mechanism was discussed and it was concluded that high-energy electrons and active particles play dominant roles in the sterilization process. The application tests results showed that after 30min treatment the bacteria concentration met the national standard of China and after 60min treatment it met the cleanliness requirements ofⅢarea identified by the ministry of health of China. Also, the PIV and HSV-I viruses were killed by this cleaner. The results showed that needle-plate corona discharge is capable to kill these viruses rapidly and efficiently. It was believed that the combination of UV light, high-energy electrons and radicals produced in discharge process is responsible for viruses killing.Multiple gas-phase pollutants were generated to simulate the air pollution in closed rooms respectively and the purification tests were carried out. Results showed that this cleaning unit has extensive and universal effect on gas pollutants removal; the efficiency and the effect were both better than other air cleaner. The purification effect of this cleaning unit on typical formaldehyde degradation was studied in detail. Results showed that higher treatment air flow rate and greater discharge power would benefit the formaldehyde removal; positive corona discharge has better effect than negative corona discharge. Qualitative analysis of the formaldehyde degradation mechanism and radical reactions were conducted. Finally non-thermal plasma combining with photo-catalyst technology has been proposed and utilized in purification of pollutant gases produced by burning cigarettes. The results of NTP and PPC treatment on pollutant gas when passed through the unit were compared and the rules were analyzed. It was proved that PPC method possessed synergetic effect in burning cigarette pollutant gas purification and the pollutants were removed by plasma chemical reaction and photo-catalysis reactions induced by high field intensity field, electrons, ions and UV lights.更多还原