• 한국분무공학회지
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• 제24권2호
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• pp.51-57
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• 2019

In this study, the spray atomization characteristics of urea injector used in SCR system for construction machinery was analyzed, and the uniformity index at the front of mixer and NOx conversion efficiency were evaluated through numerical analysis. Spray visualization and droplet size/velocity measurement were performed and the measured results were used to verify the spray analysis model to calculate the uniformity index in the exhaust gas after-treatment system. For the flow analysis, STAR-CCM, a three-dimensional CFD, was used and the uniformity index of the SCR system at the front of the mixer was calculated using the droplet dissociation model and the wall collision model. Finally, the DeNOx performance for the average condition of the NRTC driving mode was calculated to understand the NOx conversion efficiency reflecting the exhaust gas temperature. The simulation results show that the uniformity index at the front of mixer was calculated as 0.862 and DeNOx efficiency was 75.9%.

• 한국환경과학회지
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• 제27권10호
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• pp.809-820
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• 2018

DeNOx experiments for the effects of hydrocarbon additives on diesel SNCR process were conducted under oxidizing diesel exhaust conditions. A diesel-fueled combustion system was set up to simulate the actual cylinder and head, exhaust pipe and combustion products, where the reducing agent $NH_3$ and $C_2H_6/diesel$ fuel additives were separately or simultaneously injected into the exhaust pipe, used as the SNCR flow reactor. A wide range of air/fuel ratios (A/F=20~40) were maintained, based on engine speeds where an initial NOx level was 530 ppm and the molar ratios (${\beta}=NH_3/NOx$) ranged between 1.0~2.0, together with adjusting the amounts of hydrocarbon additives. Temperature windows were normally formed in the range of 1200~1350K, which were shifted downwards by 50~100K with injecting $C_2H_6/diesel$ fuel additives. About 50~68% NOx reduction was possible with the above molar ratios (${\beta}$) at the optimum flow #1 ($T_{in}=1260K$). Injecting a small amount of $C_2H_6$ or diesel fuel (${\gamma}=hydrocarbon/NOx$) gave the promising results, particularly in the lower exhaust temperatures, by contributing to the sufficient production of active radicals ($OH/O/HO_2/H$) for NOx reduction. Unfortunately, the addition of hydrocarbons increased the concentrations of byproducts such as CO, UHC, $N_2O$ and $NO_2$, and their emission levels are discussed. Among them, Injecting diesel fuel together with the primary reductant seems to be more encouraging for practical reason and could be suggested as an alternative SNCR DeNOx strategy under diesel exhaust systems, following further optimization of chemicals used for lower emission levels of byproducts.

• 한국응용과학기술학회지
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• 제28권4호
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• pp.379-385
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• 2011

One of main catalysts for De-NOx in SCR is a $V_2O_5/TiO_2$, and this work formulated powdery catalysts focusing ultimately on corrugate catalytic support. The prepared catalyst consisted of anatase $TiO_2$. Amount of the added vanadium oxide determined the viscosity of catalyst slurry, which is important for washcoat for a final corrugate type catalytic reactor. The test showed a proportional relation between adsorption amount of ammonia and specific surface area. De-NOx efficiency could be obtained up to 96.3 % at $400^{\circ}C$ with a spacial velocity of $4,000hr^{-1}$.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.237-239
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• 2009

This paper presents a new developed 160kV-120kW Class MPC (magnetic pulse compressor) power supply for DeNOx, DeSOx system. The circuit consists of N-series connected CCPS (capacitor charging power supply) and MPC Tank. The MPC power supply developed compared to the conventional LC resonant type has many advantage, it was verified reliability of a product by module, simulator and tank connection test. Now, the developed MPC power supply is installed POSCO sintering plant for DeSOx, DeNOx system.

• 대한환경공학회지
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• 제22권4호
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• pp.671-678
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• 2000

열중량분석기와 관형 고정층 반응기에서 $CuO/{\gamma}-Al_2O_3$ 흡수제/촉매의 SOx와 NOx 동시제거 반응특성에 대하여 고찰하였다. $CuO/{\gamma}-Al_2O_3$ 흡수제/촉매의 아황산가스 제거능은 반응온도 $450^{\circ}C$와 담지량 6wt% 이상에서 담체인 알루미나의 반응참여에 의하여 급격히 증가하였다. $CuO/{\gamma}-Al_2O_3$ 흡수제/촉매의 탈질 효율은 반응온도, $370^{\circ}C$에서 최대값을 보였으며 그 이상의 온도에서는 $NH_3$가스의 산화반응에 의하여 반응온도가 증가할수록 제거효율은 감소하였다. 흡수제/촉매 표면에 sulfate가 존재하는 경우 최대 탈질 효율을 보이는 반응온도는 증가하였다. SOx와 NOx 동시 제거반응에서 $CuO/{\gamma}-Al_2O_3$ 흡수제/촉매의 NO제거 활성은 $NH_4HSO_4$와 같은 암모늄염의 생성으로 인하여 크게 감소하였다. SOx와 NOx 동시제거 반응에 있어서 최대의 탈질 효율을 보이는 반응온도는 $SO_2$ 가스의 존재로 인하여 $400^{\circ}C$로 증가하였다.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.180-186
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• 2009

To meet the NOx limit without a penalty of fuel consumption, urea SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, as a basic research to develop an algorithm for urea injection control, the characteristics of engine out NOx emission and behavior of NOx reduction during steady-state and transient conditions were investigated using 2L DI diesel engine. Test results show that on increasing the catalyst temperature the variations in the outlet NOx concentration are faster and maximal allowable $NH_3$ storage exponentially decreases. For change from a low to high engine load, it can be seen that a few seconds after load-step is required to reach full NOx conversion and the adsorbed amount of $NH_3$ at lower temperature desorb during the next temperature increase, causing $NH_3$ slip. Engine out NOx emission needs to be corrected because NOx emissions just after step load is lower than that of steay state condition.

• Korean Chemical Engineering Research
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• 제49권1호
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• pp.89-94
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• 2011

하이브리드 SNCR-SCR 공정의 질소산화물 저감특성을 파일럿 규모의 흐름반응기를 이용하여 고찰하였다. SNCR 공정의 질소산화물 저감효율은 $970^{\circ}C$에서 80% 수준이었으며 하이브리드 SNCR-SCR 공정은 NSR = 2.0, $940{^{\circ}C}$에서 92%의 저감율을 보였다. SNCR 단일 공정과 비교할 때, 하이브리드 SNCR-SCR 공정은 $940^{\circ}C$보다 낮은 저온영역에서 보다 효과적이었다. 암모니아 유출농도는 비교적 높은 공간속도조건에서 1 ppm 이하로 유지되었으며 요구되는 촉매양은 SCR 단일공정과 비교할 때 2/3 수준으로 감소하였다. 질소산화물 저감을 위한 하이브리드 SNCR-SCR 공정의 주요인자는 SNCR 공정에 분사되는 요소용액의 질소산화물에 대한 선택도와 생성되는 암모니아 농도로 조사되었다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.71-76
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• 2003

A numerical simulation of selective catalytic reduction (SCR) for NO with $NH_3$ is conducted over the $V_2O_5/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The governing $NH_3$ and NO transport equations are considered by using the time-dependent FCT (Flux-Corrected Transport) algorithm. After a validating simulation for $NH_3$ step feed and shut-off experiments is analyzed, transient behavior of $NH_3$ and NO concentration in a SCR catalyst is investigated by changing such parameters as inflow $NH_3$ concentration, temperature of the catalyst, and $NH_3$/NOx ratios.

• 동력기계공학회지
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• 제17권1호
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• pp.19-26
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• 2013

The purpose of the study is carried out volume optimization of a combined system consisting of an LNT and SCR catalysts from the standpoint of its economic feasibility and de-NOx performance. Under the rich air-fuel ratio conditions for 5s (${\Phi}$=1.1), CO, $H_2$ and THC were generated at levels of 4%, 1.2% and $110ppmC_1$, respectively. The NOx conversion of the 1+1 combination was 5% lower than that of the 1.5+0.5 combination, however the reduced volume of the LNT catalyst decreased the total cost by about 6%. Therefore, the optimal volume ratio of the LNT and SCR catalysts was found to be the 1+1 catalyst combination, which has the highest total score in the terms of an economic feasibility and the NOx performance.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.117-124
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• 2011

Automotive engines require strategies to fulfill the emission regulations in terms of NOx and PM. A dramatic reduction in NOx and PM emissions could be achieved with high pressure injection, innovative combustion strategies and EGR. Recently, Lean NOx Trap (LNT) and Urea-SCR are considered as more practical strategy to suppress the engine-out emissions substantially for copying with severe regulation. These systems need to reduce the reducing agent injection system which has a huge impact on NOx purification efficiency. In this paper, different three injectors have been used to investigate spray characteristics and engine emission test was conducted to clarify the effect of these injectors on the NOx reduction.