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NH3 에 의한 선택적 촉매환원반응에서 V2O5/TiO2 촉매의 격자산소 거동에 관한 연구
문승현,이호택,이현구 ( Seung Hyun Moon,Ho Taek Lee,Hyun Ku Rhee ) 한국화학공학회 1998 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.36 No.6
Selective catalytic reduction(SCR) of nitric oxides using NH₃ has been recognized as one of the most effective denitrification processes to reduce NO_x from stationary sources. In this study, detachment and replenishment of lattice oxygen of V₂O_5/TiO₂ catalyst was investigated. In the flow of NH₃/N₂ without gaseous oxygen, NH₃reacted with the lattice oxygen to produce NO over V₂O_5/TiO₂ catalyst containing more than 3 wt% V₂O_5 whereas V₂O_5/TiO₂ catalyst containing less than 3 wt% V₂O_5 showed insignificant NO production. This indicates that lattice oxygen detaches from V₂O_5/TiO₂ catalysts having more than a certain amount of V₂O_5. Lattice oxygen-detached catalysts were regenerated by gaseous oxygen. Lattice oxygen of V₂O_5 impregnated on V₂TiO₂ was easily regenerated regardless of the temperature, but in the bulk V₂O_5, increasing the regeneration temperature leads to an increase in the degree of regeneration. From the results of TGA analysis conducted in a flow of oxygen, NH₃ pre-treated V₂O_5/TiO₂ catalyst containing more than a certain amount of V₂O_5 showed an increase of the catalyst weight as well as an increase in the H₂O concentration. This observation may be considered to support the reaction paths for detachment and replenishment of lattice oxygen proposed by Bosch et al.[1].
공업화학 , 촉매 / 반응공학 : Pitch 계 활성탄소섬유를 이용한 NO2 흡착
문승현(Seung Hyun Moon),전상구(Sang Goo Jeon),신대현(Dae Hyun Shin),김광호(Kwang Ho Kim),오창섭(Chang Sup Oh) 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.2
Adsorption and reduction of NO_2 over pitch based ACFs as received and calcined at 1,100℃ were studied in the ranges of concentrations (NO_2: 250-1,000ppm, O_2: 0-10%) and temperatures (30-70℃). Temperature-programmed-desorption(TPD) and Diffuse reflectance spectroscopy (DRIFTS) were also applied to analyze adsorbed NO_2 species. Pitch based ACFs showed rapid NO_2 reduction and adsorption. A higher reaction temperature of 70℃ decreased the ratio of NO_2 adsorption to reduction in the stationary state and shortened the time to the breakthrough. Higher NO_2 concentration increased the rates of both adsorption and reduction to shorten breakthrough time, whereas oxygen changed NO_2 profiles, by enhancing NO_2 adsorption rate and decreasing both reduction rate and capacity. The mole ratio of O/N evolved from TPD decreased and converged to a constant value according to NO_2 adsorption time, showing that NO_x species adsorbed on the ACF changed its oxidation state from higher to lower one along with the time of NO_2 adsorption. Such a trend was confirmed by the DRIFTS spectra of the adsorbed NO_2 over the ACF. To investigate active sites for NO_2 adsorption and reduction, the amount and types of oxygen functional groups were controlled by various pre-treatment. NO_2 adsorption on these pre-treated ACF showed that NO_2 adsorption site was C=0 and NO_2 reduction site was vacant carbon.
탈질공정에 사용되는 우레아 수용액의 열분해와 분사방향에 관한 연구
문승현(Seung Hyun Moon) 大韓環境工學會 2009 대한환경공학회지 Vol.31 No.7
본 연구에서는 열중량분석법(Thermo-Gravimetric Analysis, TGA)을 이용하여 우레아 수용액의 농도와 열전달 속도가 우레아 수용액으로부터 암모니아가 생성되는 과정에 미치는 영향을 관찰하였다. 또한 1,000 N㎥/h 규모의 유류 연소 보일러에 도입된 관통형 노즐을 사용하여 우레아의 분사방향을 상방과 하방으로 하였을 때를 비교함으로써 분사된 우레아가 지나는 경로에서 주위온도가 미치는 영향을 검토하였다. 질소 또는 공기 분위기에서 수행된 열중량분석 실험에서, 우레아는 산소의 존재유무에 관계없이 동일한 열분해 과정을 거쳤으며, 우레아 수용액은 가열속도에 따라 매우 다른 무게 감량 경향을 보여 가열속도가 우레아의 분해에 중요한 인자임을 나타내었다. 농도가 10%~40%인 우레아 수용액에서 우레아 열분해 시작 온도는 큰 차이를 보이지 않으므로, 농도의 영향은 그리 크지 않았다. 위치가 다른 세 곳에서 온도를 동일하게 유지하였을 때 상부 분사인 경우 탈질 효율은 각각 68.1%, 71.8%, 70.8%로 나타나 크게 차이가 나지 않았다. 동일 지역을 향하여 하부에서 분사한 경우와 상부에서 분사한 경우의 탈질 효율을 비교하면 각각 68.1%와 9.5%를 보여 동일한 지역에 분사된 우레아일지라도 분사방향에 따라 탈질 효율에는 큰 차이를 보였다. In this study, thermo-gravimetric analysis(TGA) was used to investigate the effect of urea concentration and heating rate on the ammonia(NH₃) formation process from urea solution. A newly designed pipe nozzle was inserted through a 1,000 Nßⓒ/h oil firing boiler to compare the DeNOx efficiencies between the upward and downward nozzle. This experiment reveals the effect of path which an urea droplet goes through. Urea solution showed the same TGA graph without regard to the presence of oxygen. Heating rate had a great influence on the weight loss trend. But the concentration of urea solution between 10% and 40% did not affect so much the thermal decomposition temperature. Therefore, heating rate is more important factor on the thermal decomposition of urea than the concentration of urea solution. Three nozzles located at different positions showed similar DeNOx efficiencies such as 68.1%, 71.8%, 70.8% at the same temperature. Even though urea solution was injected for the same zone, the injection direction made much difference in DeNOx efficiency. A upward nozzle showed 68.1% and downward nozzle 9.5%. This results illustrate the importance of heating rate.
문승현(Seung Hyun Moon),이승재(Seung Jae Lee),유인수(In Soo Ryu) 大韓環境工學會 2010 대한환경공학회지 Vol.32 No.10
폐 목재 소각 보일러 배가스로부터 질소산화물을 저감하기 위하여 설치된 선택적촉매환원 공정의 시운전 중에 전단에 설치된 여과포의 일부 소실이 발생되었다. 여과포 소실에 따른 불완전 연소 가스는 2단으로 설치된 저온 탈질촉매 표면을 미연탄소로 침적시켜 촉매의 탈질 효율을 급격히 저감시켰다. 활성 저하의 원인 분석을 위하여 XRD, EDX, BET, TGA, SEM 등 다양한 특성 분석을 실시하였다. 재생 방법으로 산 세척, 초음파 수 세척, 공기 중 소성의 방법을 적용한 결과, 공기분위기에서 450℃로 2시간 소성하는 것이 최적조건 임을 밝혀내었다. 재생된 촉매는 2 cm × 2 cm × 10 cm(촉매 무게 10 g) Honeycomb 촉매 시료를 이용하여 활성을 측정한 결과 사용 전 촉매와 동일한 수준의 활성인 180℃에서 NOx저감 효율 100%를 나타내었다. A bag filter system was partially burnt down during a trial run of waste wood incineration boiler. This brought about unburned hydrocarbon which caused a rapid deactivation of low temperature SCR catalyst set up in two stage after the bag filter. The deactivated catalyst was investigated in order to trace the origin by several characterization methods such as XRD, EDX, BET, TGA, SEM. The deactivated catalyst was regenerated by different methods such as acid washing, water washing in ultrasonication, and calcination treatment under air condition. It is found the calcination treatment under air condition at 450℃ for 2 hours to be the best regeneration method. The catalytic activity was measured in the form of 2 cm × 2 cm × 10 cm (catalyst weight 10 g) honeycomb type. A deNOx efficiency of the regenerated catalyst showed 100% at 180℃ which is the same level of fresh one.