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Electron beam processing for decomposition treatment of gaseous formaldehyde after sterilization

殺菌終了後のホルムアルデヒド含有空気の電子ビーム処理プロセスの開発

島田 明彦; 箱田 照幸; 小嶋 拓治

Shimada, Akihiko; Hakoda, Teruyuki; Kojima, Takuji

ホルムアルデヒド(HCHO)とメタノール(CH$$_{3}$$OH)を含む空気(いわゆるホルマリンガス)は、薫蒸殺菌に使用した後の排出のためにその短時間無害化処理が求められており、短時間大量処理に有効な電子ビーム(EB)を用いた方法を検討した。90$$sim$$1200ppmvのHCHOと30$$sim$$340ppmvのCH$$_{3}$$OHを含む空気を5$$sim$$80kGyで電子ビーム照射し、照射後の残存HCHO濃度を測定し、この結果から、初期HCHO濃度[HCHO]$$_{0}$$(ppmv)とこれを10ppmvに減少させるために必要な線量$$D$$(kGy)の関係式として、$$D$$=-4.2$$times$$10$$^{-5}$$[HCHO]$$_{0}$$$$^{2}$$+1.2$$times$$10$$^{-1}$$[HCHO]$$_{0}$$-1.2が得られた。さらに、これをもとにして、300keV, 30mAのEB発生器を用いて、1200ppmvのHCHOと340ppmvのCH$$_{3}$$OHを含む2000m$$^{3}$$の空気のEB処理に要する時間を算出すると、熱触媒法では、2$$sim$$3日であるが、約13時間に短縮できることがわかった。

Electron beam (EB) suitable for decomposition of dilute organic pollutants in high-flow rate air was applied to the treatment of formaldehyde (HCHO)/air mixture for purification in the clean room after sterilization. Air mixtures containing 90-1230 ppmv of HCHO with and without 30-340 ppmv of methanol (CH$$_{3}$$OH), which are commonly used for sterilization, were irradiated by EB to the absorbed doses of 5-80 kGy (=kJ/kg). The dose required for decreasing initial HCHO concentration to 10 ppmv was examined as a function of initial HCHO concentration (ppmv) in the air mixture ([HCHO]$$_{0}$$) with and without CH$$_{3}$$OH. The following relations were obtained: $$D$$=-4.2$$times$$10$$^{-5}$$[HCHO]$$_{0}$$$$^{2}$$+1.2$$times$$10$$^{-1}$$[HCHO]$$_{0}$$-1.2 and $$D$$=-3.8$$times$$10$$^{-5}$$[HCHO]$$_{0}$$$$^{2}$$+1.0$$times$$10$$^{-1}$$ [HCHO]$$_{0}$$-1.0, respectively, where $$D$$ (kGy) is dose. According to these results, the treatment completion time of HCHO/air mixture with CH$$_{3}$$OH using EB was simulated considering the conceptual processing. This EB processing can be applicable, e.g. the clean rooms at the food packaging factories, and contributes to improve the operation efficiency of the factories.

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分野:Engineering, Chemical

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