| Summary: | 碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 92 === The semiconductor and optical-electric industries manufacture use many chemical solvent, such as isopropyl alcohol (IPA), acetone. Notably, large amount of volatile organic compounds (VOCs) are released into atmosphere during manufacturing processes. Presently, most of the semiconductors use activated carbon adsorption tower, wet scrubber, condense incinerator (zeolite rotary adsorber + incinerator) to control the exhausted VOCs. Activated carbon adsorption tower needs regular exchange carbon to maintain its adsorption capability, so it requires more energy. According to the Taiwan EPA (2003) surveying the VOCs treatment equipment in the industries, the scrubber is one of the popular treatment process. The theory of wet scrubber is to transfer the VOCs from a gas to liquid phase. When absorption of the VOCs in liquid approaches saturation that the wasted liquid needs further treatment. Therefore, the emission and control of HAPs in the science-based Industrial Park need further study. This study set up a set of pilot-scale scrubbing and oxidative system (a 220 cm H × 20 cm L × 5 cm W scrubber and a 220 cmH × 15 cm-dia. oxidizer) to evaluate the performance the treatment of gas-borne VOCs emitted from semiconductor and optical-electric industry. Operation parameters are gas flow rate of 300 L/min, VOCs concentrations of 50-500 ppm, UV185nm intensity of 14 W/m, and UV254nm intensity of 9 W/m. The target VOCs is propylene glycol monomethyl ether acetate (PGME) and toluene. Operational parameters, such as influent VOCs concentration (C0), the height of the water (H), the concentration of the hydrogen peroxide, were conducted in the study.
The batch experiment in the oxidizer, it is include toluene and PGME to deal with different depth of water. The experiment results show to remove tap water achieve＞85% removal efficiency of the PGME without any additives on oxidation process. The different oxidation processes deal with toluene in the different depth of water, the removal efficiency and degradation toluene in the aqueous is UV/H2O2 ＞ UV ＞ without. With the depth of water raising the removal and degradation efficiency follow increase. As comparison with the UV and UV/H2O2 processes, the addition of H2O2 can meet more oxidizing potential of the hydroxyl radical and promote the removal efficiency. Under the different hydrogen peroxide dose, UV254nm with 100ppm hydrogen peroxide can achieve 80％ removal efficiency and maintain for 140 min. In the experiment processes the reaction constant of the different processes are KOH ＞ KUV ＞ KO, and the UV185nm with H2O2 is the best (0.7 hr-1).
The result in the pilot-scale scrubbing and oxidative system deal with toluene, the removal efficiency is the high exhaust gas concentration better than low gas concentration, and low superficial gas velocity is better than high gas velocity. In the 10 hours experiment period the H2O2 add into the system with batch, it can raising the removal efficiency and also degradation the toluene in the water. Compare the system deal with different PGME concentration in the same L/G, UV/H2O2 can effective degradation the PGME in the water of the low PGME concentration. When accede to the H2O2 can’t obvious the PGME in the water have a change, because the H2O2 is always enough for UV/H2O2 produce OH free radical degradation PGME in the water.
|
|---|
