Research On The Treatment Of Gaseous Pollutants With Built-in Microwave Electrodeless Ultraviolet Lamps

In recent years, a new type of microwave discharge electrodeless lamp (MDEL) as UV light sources have been gradually developed. Treatment of pollutants with MDEL has become a research hotspot. There are dozens of research papers in that regard, but most are involved in aqueous phase, for not many reports of gaseous pollutants. The research group I belonged is first to deal gaseous pollutants with microwave discharge lamp device in the world. The device was an external electrodeless lamp structure (i.e. Exterior Microwave Discharge Electrodeless Lamps, EMDELs), In the device only a part of lamp is inserted into resonant cavity, and microwave energy will be transmitted to inspire lamp on the other side of the lamp, then ultraviolet light is produced to treat the polluted gas..Because the lamp is not fully stimulated, the degradation rate of gaseous pollutants is not high. Therefore, this study developed a new type of lamp built-in structure (i.e.Interior Microwave Discharge Electrodeless Lamps, IMDELs) to overcome the drawbacks of external lamp structure, still for dealing with gaseous pollutants.In this study, the optimization process of interior lamp construction expanded, and H2S, CS2, ethyl acetate are used as the treated objects, and a new type of built-in convection IMDEL devices ultimately developed to achieve completely efficient handling of dynamic gas flow of pollutants in the resonant cavity, and to some extent alleviated the negative impact of thermal effects with interior microwave discharge electrodeless Iodine lamp (IMDEL-I2), which greatly improves the treatment and energy-use efficiency of various gaseous pollutants controling.This study carried out innovative work in the following areas:(1) Parameter optimization of microwave discharge electrodeless lampThe preliminary performance of four excimer lamp was analyzed, including IMDEL-I2 and IMDEL-Hg and IMDEL-Br2 and IMDEL-Se. The further study about microwave IMDEL-I2 was done, including the buffer substance the type of research, the ratio of light-emitting material and the buffer material.(2) MDEL-I2 directly in the resonant cavity:A simple built-in IMDEL-I2 device was developed to treat low concentration of butyl acetate. In the condition of retent time 13.3s and inlet concentration 1.5mg/m3, the degradation rate of butyl acetate reach 78%, but as the retent time of 3.3s, the degradation rate fall to 48%. In addition, the experiment found that the simple built-in IMDEL-I2 device had some defects such as corrosion, high energy consumption. Therefore, the follow-up experiment, the imple built-in IMDEL-I2 device are not used, and butyl acetate not as the treatment object.(3) IMDEL-Hg in the quartz tube:A new built-in-tube IMDEL-Hg device was developed to treat H2S and data was gathered for next experiments with microwave discharge electrodeless Iodine lamp. Experiments show that the H2S degradation rate of IMDEL-Hg can increased by 13% or more than EMDEL-Hg,and energy efficiency has been further improved. In the condition of retent time 1.5s and inlet concentration 7.9mg/m3,the H2S degradation rate was 91%, Ey of 58.2 mg/kWh; When the H2S inlet concentration increased to 24.6mg·m-3, the degradation rate was 57%, Ey of 115.6 mg/kWh.(4) IMDEL-I2 in the quartz tube:the experiment study of the H2S degradation with built-in-tube IMDEL-I2 device was carried out. When IMDEL-I25.3mg/L was used,because the amount of photons was not enough due to iodine deficiency and the heating maybe affected the degradation rate of H2S, so the H2S degradation rate remained less than 50%. When IMDEL-I2 21.2mg/L was used, Experiments found out the problem of frequent overheating. Therefore, the follow-up experiment focused on heating effect of IMDEL-I2.(5) Heating effect of built-in-tube 1MDEL-I2:The relevant laws of heating effect about IMDEL-I2. was studied, and so the data gives a strong foundation for controling lamp temperature and increasing the degradation rate. Experimental results show that 1) the length of cavity resonator was extended, the MEDL was offsided from the center zone,the pipeline was adjusted vertically from the flat, All the measure will be good for heat dissipation.2) electrodeless iodine lamp excited by microwave can release a large amount of heat, which increased the lamp temperature. And the heating affected the degradation rate of H2S.3) The heat amount was different,when IMDEL-I2 in different positions in the cavity. and the temperature reduced about 10?,if 9 cm of IMDEL-I2 placed outside the resonant cavity.at the same time, the the degradation rate of H2S was increased.4) H2S photolysis reaction heat had some effect on the lamp temperature; the lamp temperature increased by only about 5?.at the presence of H2S photolysis reaction heat when the total treated amount increase from 6.18 mg/m3 to 8.69 mg/m3.(5) Built-in convection IMDEL-12:A new type of built-in convection IMDEL devices was ultimately developed. The internal gas of IMDEL can be recycled by convection to cool the lamp, so the problem of frequent overheating was avoided. Resonator can be placed vertically to promote the further excitation lamp, and ultimately improve the ability of gas degradation. Microwave electrodeless iodine lamp fully in the cavity also improved the utilization of lamps.Using the new built-in convection microwave electrodeless lamp for Treatment of iodine H2S, in the condition of RT 1.2s and inlet concentration 9.7mg/m3 and input power 200W, the degradation rate can reach 71.4%.Compared with the results of the built-in-tube IMDEL-Hg device, the degradation rate and energy efficiency are almost the same,and avoid the secondary pollution of mercury. Compared with the external microwave electrodeless lamp, the degradation rate and energy efficiency have improved significantly.Using the new built-in convection microwave electrodeless lamp for Treatment of iodine CS2, in the condition of inlet concentration 9.7mg/m3 and input power 200W and RT 1.2s, the degradation rate can reach 96.0%.Compared with the external microwave electrodeless lamp,the degradation rate and energy efficiency have improved significantly.