### 8. 英文概要

Development of the Efficient Recycling Technology for Waste Organic Solvent

Recently, Volatile Organic Compounds (VOC) exhausted from coating and printing plants has become a serious problem as air pollution. Particularly, VOCs (Volatile Organochlorine Compounds) such as DCM ((Dichloromethane) and TCE (Trichloroethylene)) was reported as carcinogens by Ministry of Health. DCM was the largest amount of emission among VOCs in 2012 and is difficult to remove by general adsorbents because of its low boiling temperature. The method absorbing VOC in the exhaust by the removal solvent is effective. However, the removal solvent absorbed VOC becomes industrial waste if it throws away, so that the regeneration of the removal solvent is preferable. In this study, the efficient regeneration technology of waste solvent containing VOC was developed. We investigated the following research subjects.

1. The removal technology for VOC in the exhaust gas by spraying removal solvent

The removal treatment of IPA (Isopropyl Alcohol) which released from the drying process in semiconductor manufacturing process has become a problem. The removal technology of IPA was developed by spraying removal solvent to PUF (Polyurethane Foam) as a gas absorption material. As the result of calculating Henry's constant for various solvents by using UNIFAC (Universal Functional Activity Coefficient) method, it was found that TPGME (Tripropylene glycol mono-methyl ether) is the best removal solution for IPA. TPGME also meets other requirements as a removal solvent such as high boiling point, low viscosity, safety property and reasonable price.

As results of evaluation experiments removing IPA in the exhaust gas, it was found that the developed equipment could remove IPA with 62.5% of removal efficiency by the condition of co-current flow at flow rate of $ 1m^{3}/min $ of exhaust gas and 1L/min of removal solvent. Moreover, more than 90% of IPA in the exhaust gas can be removed in the case of the double-stage equipment at $ 15^{\circ}C $ of gas absorption temperature.

According to Henry’s law, the lower gas absorption temperature becomes the more gases absorbing into removal solvent. The removal equipment for VOCC such as DCM and TCE by spraying removal solvent to cooling fin as a heat exchanger was developed. Because of its large heat transfer area of cooling fin, fast heat exchanging coincided with fast gas absorption into removal solvent. TEGDME (Tetra ethylene glycol dimethyl Ether) was selected as the best removal solvent by using UNIFAC method. As results of evaluation experiments removing DCM and TCE in the exhaust gas, it was found that the developed double-stage equipment could remove 92.3% of DCM and 92.5% of TCE by the condition of co-current flow at flow rate of $ 1 \, m^{3}/min $ of exhaust gas and $ 1 \, L/min $ of removal solvent in the case of $ 4.5^{\circ}C $ of gas absorption temperature.

Furthermore, the third-stage removal equipment was investigated to use TPGME which is one quarter the price instead of TEGDME. Removal experiment of DCM and TCE from exhaust gas using the third-stage equipment with cooling fins was carried out, and removal efficiencies of DCM and TCE was $ 93.1 \pm 1.6\% $ (n=5) and $ 98.8 \pm 0.6\% $ (n=5), respectively, at $ 8.1^{\circ} $ C. These experimental removal efficiencies were agreed with theoretical values of 93.2% for DCM and 99.5% for TCE.

As the result of several experiments, the developed equipment by spraying removal solvent to cooling fin can remove VOCC in exhaust gas with the removal efficiency of more than 90%.