• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.127-138
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• 2016

Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.77-78
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• 2015

산업화로 인하여 토지의 사막화, 물부족, 오존층 파괴, 지구 온난화 등 많은 환경문제가 발생되었으며 아직 진행 중에 있다. 이에 UN에서는 환경 규제를 강화하였으며 국제해사기구(IMO:International Maritime Organization)에서는 선박의 배기가스 규제 강화를 위하여 NOx(질소산화물) 및 SOx(황산화물)의 배기량을 줄이도록 하고 있으며 2016년부터는 본격적으로 규제하려 하고 있다. 상기의 규제 물질 중 NOx를 제거하는 선택적환원촉매(SCR:Selectivity Catalytic Reduction) 시스템은 선박의 배기가스가 지나가는 통로에 요소수(Urea)를 분무하여 $260^{\circ}C$ 이상의 높은 온도에서 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응, 결합함으로서 NOx를 질소와 산소로 분리, 제거하는 방식이다. 하지만 선박의 경우 대부분 엔진이 2행정으로 배기가스 온도가 일반적으로 $180^{\circ}C{\sim}220^{\circ}C$이기 때문에 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응하지 않아 환원률이 높지 않다. 이에 우리는 초미세기포를 이용하여 낮은 온도에서도 반응할 수 있는 요소수 및 요소수 활성화 기기를 개발하여 상기의 문제점들을 최소화 할 수 있도록 하였다. 또한 SCR 시스템의 점성유동해석을 통하여 보다 효율적인 SCR 시스템의 개발을 할 수 있도록 기여하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.88-89
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• 2016

선택적 환원 촉매(SCR : Selective Catalytic Reduction) 시스템은 대기오염을 예방하기 위한 배기가스 처리장치 중 하나이다. 본 연구에서는 전산유체역학(CFD : Computational Fluid Dynamics)를 사용하여 SCR 시스템 의 효율향상을 위하여 ANSYS-CFX package를 이용하여 점성 유동 해석을 수행하였다. SCR 시스템의 점성 유동 흐름의 전산 유체 역학을 이용하여 시뮬레이션하기 위하여 Navier-Stokes 방정식을 지배방정식으로 사용하였다. CATIA V5를 사용하여 SCR 시스템의 형상을 3D 모델링을 하였고, 암모니아와 배기가스의 혼합 비율을 확인하기 위해 요소수 분사 노즐의 위치를 변경하였다. 요소수 분사 노즐은 배기관의 입구로부터 1/3, 1/2, 2/3에 위치한다. 또한, 분사 노즐의 위치가 배기관 입구의 1/3에 위치할 때 노즐의 분사구수에 따른 효율을 확인하기 위하여 분사구수를 4Hole, 6Hole, 8Hole일 경우를 확인하여 비교하였다. 시뮬레이션의 결과로는 배기관 입구에 가까울수록, 분사구수가 많을수록 효율이 좋아짐을 확인하였다.

• Journal of the Korea Convergence Society
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• v.10 no.8
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• pp.153-158
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• 2019

The overall environmental regulations of the industry have been strengthened due to environmental pollution that occurred in modern society. Therefore, R&D of selective reduction catalyst (SCR) is needed to meet these environmental regulations. This paper carried out thermal analysis to develop the pneumatic damper valve (PDV), which is a key component of SCR system. For thermal analysis, verification of material properties was performed first. Verification was performed through the thermal properties test and the thermal tensile test of the specimen, and the results were reinforced with the material properties to enhance the reliability of the thermal analysis.The heat analysis was intended to identify thermal characteristics with PDV in total of three materials (SM400B, SS275, SB410) applied under the conditions of use of PDV, and to confirm the structural stability of the PDV.

• Clean Technology
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• v.27 no.3
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• pp.207-216
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• 2021

Major anthropogenic emissions of elemental mercury (Hg⁰) occur from coal-fired power plants, and the emissions can be controlled successfully using NH₃-SCR (selective catalytic reduction) systems with catalysts. Although the catalysts can easily convert the gaseous mercury into Hg²⁺ species, the reactions are greatly dependent on the flue gas constituents and SCR conditions. Numerous deNO_xing catalysts have been proposed for considerable reduction in power plant mercury emissions; however, there are few studies to date of elemental mercury oxidation using SCR processes with MW- and full-scale coal-fired boilers. In these flue gas streams, the chemistry of the mercury oxidation is very complicated. Coal types, deNO_xing catalytic systems, and operating conditions are critical in determining the extent of the oxidation. Of these parameters, halogen element levels in coals may become a key vehicle for obtaining better Hg⁰ oxidation efficiency. Such halogens are Cl, Br, and F and the former one is predominant in coals. The chlorine exists in the form of salts and is transformed to gaseous HCl with a trace amount of Cl₂ during the course of coal combustion. The HCl acts as a very powerful promoter for high catalytic Hg⁰ oxidation; however, this can be strongly dependent on the type of coal because of a wide variation in the chlorine contents of coal.

• Clean Technology
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• v.20 no.3
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• pp.269-276
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• 2014

This study was aimed to develop catalytic system for the dry-based reduction of oxidized mercury ($Hg^{2+}$) to elemental mercury ($Hg^0$) which is one of the most important components comprising mercury continuous emission monitoring system (Hg-CEMS). Based on the standard potential in oxidation-reduction reaction, transition metals including Fe, Cu, Ni and Co were selected as possible candidates for catalyst proceeding spontaneous reduction of $Hg^{2+}$ into $Hg^0$. These transition metal catalysts revealed high activity for reduction of $Hg^{2+}$ into $Hg^0$ in the absence of oxygen in reactant gases. However, their activities were greatly decreased in the presence of oxygen, which was attributed to the transformation of transition metals by oxygen to the corresponding transition metal oxides with less catalytic activity for the reduction of oxidized mercury. Hydrogen supplied to the reactant gases significantly enhanced $Hg^{2+}$ reduction activity even in the presence of oxygen. It might be due to occurrence of combustion reaction between $H_2$ and $O_2$ causing the consumption of $O_2$ at such high reaction temperature at which oxidized mercury reduction reaction took place. Because the system showed high activity for $Hg^{2+}$ reduction to $Hg^0$, which was compatible to that of wet-chemistry technology using $SnCl_2$ solution, the catalytic reduction system of Fe catalyst with the supply of $H_2$ could be employed as a commercial system for the reduction of oxidized mercury to elemental mercury.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.772-777
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• 2012

Factors acting on the deactivation of $V_2O_5/TiO_2$ catalysts were investigated in the selective catalytic reduction(SCR) process for long term operation. The activity of $V_2O_5/TiO_2$ catalysts was decreased rapidly after 8 months from the starting of operation in the selective catalytic reaction processes. From ICP-AES analysis, the deactivation of the used catalysts could be caused from the calcium component included in urea solution as a reducing agent. It was found from the $NH_3$-TPD experiments that the strong basic element like Ca component drastically affected the acidity of the $V_2O_5/TiO_2$ catalyst. The results gave an explanation on the reason why the component of Ca, even though its concentration is very low, could lead to the deactivation of $V_2O_5/TiO_2$ catalyst in the selective catalytic reaction processes.

• Plant Journal
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• v.18 no.3
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• pp.52-61
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• 2022

This study tested the effect of de-NOx Facility operating condition on Nox emisiion in a 125 MW wood pellet power plant in Yeongdong Eco Power Plant Unit 1, which is in operation. As SNCR urea flow rate increased, NOx emission gradually decreased, but ammonia slip after SCR increased. The boiler under test has a structure that is unfavorable to SNCR operation due to the high internal temperature, and the optimum location of the nozzle will be required. SCR dilution air temperature change did not affect the amount of NOx generated. Increasing SCR ammonia flow reduced the NOx emission at SCR outlet and also increased the NOx removal efficiency. However, the ammonia flow rate of 111 kg/h, which does not exceed the ammonia slip its own reference limit, is estimated to be the maximum operating standard. The increase in SCR mixer pressure reduced NOx emission and the removal efficiency was also measured to be the most effective variable to inhibit NOx production.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.540-546
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• 2006

Effects of organic and inorganic additives on the SNCR reaction of NOx were investigated in a pilot scale flow reactor with a variation of operating parameters. NOx reduction efficiency increased with the increase of a residence time and an initial NOx concentration. NOx reduction reaction by urea solution started to appear about 850 and then reached to maximum value around $970^{\circ}C$. NOx reduction efficiency also increased with the increase of NSR (Normalized Stoichiometric Ratio) up to 2.0. Addition of ethanol and phenol as an organic additives shifted the optimum temperature window to lower region with decreasing the maximum NOx reduction efficiency. This might be due to the side reaction of hydrocarbon in ethanol structure. NaOH addition widened the temperature window and enhanced the NOx reduction efficiency about 10％ due to the chain reaction of NaOH and the reduction of $N_2O$.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.05a
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• pp.236-239
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• 1995

50 kW$_{th}$ 용량의 기체연료버너에서 암모니아 기체와 요소용액을 이용한 선택적 무촉매 환원법 (SNCR;Selective Non-catalytic Reduction) 으로 질소산화물 (NOx) 저감에 관하여 연구하였다. 암모니아는 요소요액보다 더 낮은 반응온도에서 더 높은 효율을 보여주지만 경제성과 암모니아의 부식성 및 맹독성으로 인하여 취급하기에 곤란한 점이 있다. 반면에 요소용액은 적절한 액상첨가제와 기상첨가제를 사용하여 넓은 반응온도범위에서 높은 효율을 얻을 수 있으며 공정상의 조업비를 절감할 수 있다. 본 실험에서는 액상 첨가제인 $CH_3$OH 와 $C_2$H$_{5}$OH 을 사용하여 5$0^{\circ}C$ 정도의 최적반응온도 감소를 얻었으며 LPG 와 합성가스(CH$_4$:CO:H$_2$:$CO_2$=1:4:4:2) 틀 기상 첨가제로 사용하여 높은 질소산화물 저감 효율을 관찰하였다.