초임계수산화와 습식산화에서 Ethylene glycol 계열화합물 분해특성 비교 = Comparison between Supercritical Water Oxidation and Wet Air Oxidation of Aqueous Solutions of Ethylene Glycols

국문 초록 (Abstract)

난분해성 유기물질이 포함된 폐액의 소각처리 대체방법인 초임계수산화와 습식산화방법을 이용하여 ethylene glycol 계열화합물(HO(CH₂CH₂O)_(n)H) 수용액 분해특성을 비교하였다. 초임계수산화반응은 등온관형반응기를 이용하여 반응온도 380~425℃, 필요산소량 100~400%, 250 bar 등압에서 수행되었으며, 습식산화법은 회분식반응기를 이용하여 반응온도 200~300℃, 필요산소량 100~400%에서 수행되었다. 일반적으로 적용되는 산화반응조건에서 완전산화되는 반응시간은 습식산화법에서는 수시간이 필요한 반면, 초임계산화법에서는 1 min 이내로 소요되었다. Ethylene glycol 계열화합물(EG, DEG, TEG) 분해는 두 방법 모두에서 분자량이 증가할수록 분해율이 증가하였으며, 분해가 잘되지 않는 EG의 경우 습식산화법에서는 300℃, 초임계수산화법에서는 425℃의 반응온도가 필요하다. 습식산화법에서는 필요산소량이 증가함에 따라 분해반응속도가 증가한 반면, 초임계수산화법에서는 분해율 영향이 적었다. 이는 초임계수산화 조건에서는 산소와 물이 단일상으로 혼재하므로 물질전달 제한이 없기 때문이다. 초임계수산화법은 습식산화법에 비해 고온ㆍ고압이 요구되지만 처리용량과 효율을 획기적으로 증가시킬 수 있다.

다국어 초록 (Multilingual Abstract)

The processes of supercritical water oxidation (SCWO) and wet air oxidation (WAO) are promising alternatives to incineration of aqueous recalcitrant organic waste streams, and had been compared with decomposition of aqueous solutions of ethylene glycols (HO(CH_(2)CH_(2)O__(n)H). The SCWO experiments were performed in an sothermal tubular flow reactor at temperatures ranging from 380 to 425 ℃. The initial amount of air ranged from 100 to 400% of stoichiometrically required amount of air for complete oxidation, while the operating pressure was maintained at 250 bar for all runs. The WAO experiments were studied in a batch autoclave reactor at temperature between 200 and 300 ℃ and stoichiometrically required oxygen ratio from 100 to 400%. Though reaction times in WAO were up to several hours, a complete destruction of ethylene glycols (EGs; in SCWO required less than 1 min of reaction time under each conventional reaction condition. SCWO conditions increased the decomposition rate of EG. The decomposition rate of ethylene glycol cornpounds increased with increasing ethylene glycol units in the both processes. Among the three EG compounds (EG, DEG and TEG)), EG was the most refractory compound, which has decomposed well at around 300 ℃ for WAO and 425 ℃ for SCWO. Whereas the increasing amount of oxygen required accelerated EG decomposition in WAO, it had little effect on EG destruction in SCWO. It suggests that the mass transfer limitation does not exist because oxygen became completely miscible with supercritical water, like single phase reaction under SCWO. Though SCWO process required more severe reaction conditions, SCWO dramatically increased the removal capacity and efficiency compare to WAO.