먼지와 질소산화물의 동시처리를 위한 촉매필터의 질소산화물 제거특성에 대한 연구

최현덕 연세대학교 대학원 2003 국내석사

본 연구는 실제 발전소 등에서 집진공정과 NOx저감 SCR공정이 함께 설치된 공정에서 나타나는 촉매의 활성저하 및 plugging 현상과 재 가열해야하는 에너지 손실 등의 문제점들을 해결하여 열효율 향상과 처리비용 절감 및 장치설비 공간, 설치비용 등의 절감 등의 효과를 얻기 위해 질소산화물 제거를 위한 촉매공정과 먼지제거를 위한 집진공정을 일체화한 hybrid system의 촉매필터를 고안하여 제작하였다. 일차적으로 촉매필터의 NOx 전환율에 대한 실험을 수행하였으며, 그에 따른 필터에 담지된 촉매의 양, NH₃/NOx 몰비, Face velocity, 시간, 온도 등에 대해 각각 NOx 전환율 test 및 slip되는 NH₃ 검출 등 기초적인 실험을 실시하여 실험결과를 토대로 NOx 저감용 촉매필터개발에 필요한 조건들을 알아보았다. 촉매를 코팅시키기 위해서는 필터의 표면뿐만 아니라 내부까지 코팅하기 위해 코팅장치를 제작하여 실시한 결과 SEM분석을 통해 필터의 각 fiber에 촉매가 내부까지 고르게 코팅이 되었으며, 필터의 pore를 막는 현상은 없었다. 하지만 바인더의 영향으로 고정층에서의 실험과 비교하여 전환율이 낮아졌으며, 이점에 대해서는 새로운 바인더의 개발을 필요로 한다. 촉매필터의 반응성 실험결과 먼저 face velocity 결과로부터 촉매필터는 불규칙하게 구성된 fiber에 의해 유체의 흐름이 불규칙하여 반응gas와 촉매와의 mass transfer를 증가시키게 되므로 honeycomb에 비해 space velocity가 2.5배 크더라도 같은 전환율을 얻었다. 촉매의 담지량은 필터의 압력손실을 감안하여 그 양을 결정해야하며, 촉매의 담지량별 실험결과 촉매의 담지량이 증가할수록 높은 전환율을 보였으나 그 담지량을 10.97g 이상 증가시킬 경우 증가율이 감소되는 경향을 나타냈다. 따라서 촉매의 최적 담지량을 10.97g로 결정했으며, 단위면적당 촉매코팅양은 0.46g/㎠이다. 반응온도는 230℃이상에서 NH₃가 자체산화와 고온에서의 NO₂생성으로 인해 반응에 필요한 NH₃의 감소로 전환율이 약간 감소하는 결과를 얻었으며, NH₃의 배출은 온도전역에서 NH₃/NOx mole ratio 1.0부터 배출되기 시작하므로 NH₃로 인한 2차 오염을 방지하기 위해 0.9 이하에서 결정해야한다. 또한 face velocity 실험결과 0.8에서 2.0사이에서 90~82%의 전환율을 얻었다. 따라서 0.46g/㎠의 촉매를 코팅한 필터에, 반응온도 190~230℃, face velocity 0.8~1.6m/min, NH₃/NOx mole ratio 0.9로 실험조건을 할 경우, NOx를 85% 제거할 수 있으며, 또한 NH₃에 의한 2차 오염도 방지할 수 있는 것으로 나타났다. The typical air pollution control devices (Bag filter or Selectively Catalyst Reactor) were used to have some troubles, such as plugging, catalyst activity drop, and energy loss for flue gas re-heating, during the operation to control the particulate matters and NOx from power plant as the emission source. This study was focused on the energy, cost, and spatial effective process which referred as hybrid system; combined process of catalytic process for NOx and particulate matter control. The NOx conversion rate and detection of slipped NH₃ were investigated to estimate the appropriate amount of catalyst, NH₃/NOx mole ratio, face velocity of flue gas, residence time, and temperature. To coat filter with catalyst, the coater, which was available to coat not only surface but also inner space of filter fiber, was needed. It was regarded that the catalyst was fluently coated on surface and inside without any stopping pore of filter as the result of SEM analysis. However, the NOx conversion rate in the experiment of coated filter was lower than the fixed bed experiment's because of the binder. The advanced binder will be required in further research. Even though the catalytic filter had 2.5 times faster space velocity than honeycomb's, it showed similar NOx conversion rate with honeycomb type because of its irregular flow by porous fiber. The amount of catalyst loaded on the fiber must be decided with the consideration of pressure drop of filter. The NOx conversion rate was increased with the amount of catalyst loaded on the filter; however, after more than 10.97g of catalyst loaded, the conversion rate was decreased. Thus, the optimum amount of catalyst loaded was regarded as 0.46g catalyst per unit area of filter. The NOx conversion rate was decreased at the temperature 230℃ and above, because NH₃ was oxidized by itself and was decreased by forming NO₂ under the high temperature. The drawing off of NH₃ was observed after the NH₃/NOx mole ratio 1.0 in all experimented temperature (150-230℃), so that the mole ratio must be below 0.9 to prevent secondary contamination. Additionally, the NOx conversion rate showed 90% and 82% at the mole ratio 0.8 and 2.0, respectively, as results from the face velocity experiment. As the conclusions, the optimum conditions of NOx control in hybrid system were regarded to the conditions such as 0.46g catalyst coated per unit area of filter, 190~230℃ of reaction temperature, 0.8~1.6m/min of face velocity, and 0.9 of NH₃/NOx mole ratio to eliminate 85% of NOx and to prevent the secondary contamination.

도시고형폐기물 소각시설 집진공정에서의 다이옥신류 거동특성 및 운전변수에 관한 연구

윤균덕 서울시립대학교 2000 국내박사

粉體塗料 塗裝工程의 集塵裝置에 관한 연구

김인성 崇實大學校 産業大學院 1997 국내석사

산업용 보일러 시스템의 SNCR 공정과 집진.축열 장치 고도설계를 위한 수치해석

신미수 忠南大學校 2003 국내박사

Since 1970s, Computational Fluid Dynamics (CFD) or Computational Fluid Engineering (CFE) has become a reliable and cost-effective designing tool and this method has been widely employed for various fields of industrial problems including energy and environmental topics. As a part of similar research efforts, in this study, the development of a reliable comprehensive computer modeling of this area is made. The purpose of this numerical study is, of course, to assist in the design and the determination of optimal operating condition of related facilities as a supplemental tool of analytical and experimental methods. This study deals with the three components as a combined system, that is, industrial boiler, high temperature cyclone, and thermal stratification storage tank, which might be considered as loosely-linked, three-separate systems. But the specific topics of this study are consistently focused on the combustion-related air and thermal pollution problems together with the aspect of energy saving. In more detail, for the system of industrial boiler, turbulent reaction modeling is made in order to investigate the NO reduction via SNCR process. For this, a couple of turbulent reaction modeling and calculation have been performed, that is, turbulence fuel combustion including minor pollutant formation and destruction in turbulent flows. To be specific to the latter case, the modeling and computer code incorporation are made for the thermal NO formation and its destruction by the reaction with the liquid-phase reduction material such as urea. Further, the volatilization and trajectory of liquid droplet are analyzed in the frame of Lagrangian approach in 3-D rectangular coordinate. In order to achieve the SNCR modeling of industrial 3-D boiler, a couple of preliminary investigations have been made successfully for the small gaseous LNC combustor in 2-D axi-symmetric coordinate and 2-D rectangualr-shape afterburner of waste-off gaseous incinerator. For the second system of cyclone, a series of numerical investigation with experiment have been made for the dust collector cyclone operating with high temperature and pressure environment. The main purpose of this study is to develop a reliable computer program to figure out the physical concept of dust collection mechanism in extreme operating condition and thereby to obtain useful engineering data to enhance the high efficiency of dust collection. The third part of this study deals with the thermal storage system supplied mainly by the waste energy, in which the focus of the study is given on the enhancement of energy utilization by the resolution of the buoyancy-driven thermal stratification problem in the process of cold and hot water loading and discharging. In this topic, proper operating conditions of laboratory and commercial scale system are suggested by the systematic investigation of important parameters. Special emphasis is given on the development of the evaluation method for the degree of thermal stratification, which is directly linked to the performance of thermal storage system but mainly dependent on empiricism. Major useful results via this study can be drawn and summarized separately for three area of this thesis as follows: 1. A turbulent reaction program including SNCR modeling is first developed and tested for a small 2-D axi-symmetric gaseous combustor and an afterburner of waste-off incinerator, in which the modeling of afterburner is simplified by 2-D rectangular geometry. The purpose of this preliminary study is to evaluate and confirm various sub-models of the comprehensive program for the relatively simple and small system in order to develop a computer program of a 3-D full-scale industrial boiler. The program developed has been successfully evaluated by a series of parametric investigation with important operational and design parameters. For instance, numerical simulation has been made with various parameters such as theoretical air ratio, swirl intensity, heating value, the change of injection method of reducing agents such as injection velocity and position of injection port. The calculated results are in general physically acceptable and show consistent trend. In more specific, NOx can be removed more efficiently with the increase of swirl intensity, the increase of penetration depth of the reducing agent due to the increase the velocity, drop size and the employment of mixing air, etc. In particular, as might be expected, the generation of thermal NOx rapidly increases as heating values increases. For the industrial boiler with 3-D rectangular coordinate, the general coding are made for various turbulence modeling such as turbulent flow, turbulent fuel combustion, thermal NO formation and destruction together with the NO reaction with reducing material. Further, the incorporation of drop trajectory model is successfully is made in 3-D rectangular coordinate with Lagrangian frame and the swirl effect is also incorporated by the resolution of the tangential velocity component of cylindrical coordinate into x- and y- velocity components in rectangular coordinate. Based on the calculation results, the SNCR method in a industrial boiler shows the possibility as one of viable NO reduction method by the use of well designed mixing air of reducing agent. Note that the application of SNCR method to industrial boiler is usually known as not feasible due to the insufficient residence time for proper mixing. The main swirl burner effect on the characteristics of flame is considered. As expected a short flame was created and thereby NO_(X) is removed more efficiently by the increase the proper region of temperature for NO reduction reaction. 2. Considering the design of high efficiency cyclone, the important thing to note is to minimize the pressure drop with the enhancement of the efficiency of dust collection. Thus the computer program developed for the cyclone of high temperature and pressurized environment was successfully validated by the comparison of calculated pressure drop data with experimental value obtained also in this study. In general, the pressure drop increases as the increase of flow rate, the reduction of operating temperature decreased, and the increase of operating pressure. Dust removal efficiency also shows that it increases as the increase of flow rate and temperature with the decrease of temperature. Further the efficiency is also found to decrease as the vortex finder diameter of cyclones increased. But the efficiency was not affected significantly by the change of the length of vortex finder length. 3. The computer program developed for thermal storage tank is evaluated successfully against the experimental temperature data and dye visualization method of flow pattern. Based on the results of numerical simulation it was found that the degree of thermal stratification in a large storage tank was most significantly affected by increase of hot water loading time due to increase of the diffusion and convection heat transfer. Also the type of diffuser shows a certain degree of visible effect on the performance of tank, in which curved type diffusers were found to be more effective than the flat type. The performance evaluation method developed in this study is based on the novel idea that the best performance of storage tank can be obtained when the minimum convective mixing occurs, that is, the loading is made by the plug-type flow. Thus in order to model this situation, plug type flow situation is assumed with constant axial velocity and thereby the convective mixing effect is completely annihilated. This kind of performance evaluation is accomplished by the solving governing equation of energy with constant axial velocity without radial velocity component. This method is no more dependent on empiricism of the evaluation of the degree of the thermal stratification. Using this method, it was shown that the efficiency of laboratory scale tank is much inferior than that of the commercial scale. It can be qualitatively explained by the relative strength of the overall thermal input and the degree of heat mixing. In overall conclusion, this study deals with the three components as a combined system, that is, industrial boiler, high temperature cyclone and thermal stratification storage tank. Three programs developed are successfully evaluated with experimental data and a number of useful conclusion are drawn such as the feasibility of the use of SNCR method to industrial boiler, the rational evaluation method of the performance of thermal storage tank and possible application of high efficiency cyclone in extreme environment.

유리용해로 공정의 먼지 비저항에 따른 전기집진기 효율변화에 관한 연구

배현기 亞洲大學校 産業大學院 1995 국내석사

Rice Husks를 이용한 제철소 집진DUST중의 중금속 고정화 공정 연구

추호선 中央大學校 1993 국내석사