• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.295-296
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• 2015

We presented the methods calculating the reduction efficiency of nitrogen oxide for the low $NO_x$ burner as the pollution prevention facilities. The standard $NO_x$ concentration was used on the emission factor of LNG, $3.7g/m^3$. The $NO_x$ reduction efficiency based on the $NO_x$ concentration was presented and the relationships between the $NO_x$ concentration and the emission factor or the specific heat emission factor were derived. These results could be accurately reflected on calculating the amount of the nitrogen oxide emissions. In addition, according to the arrangement of the low $NO_x$ burners the methods of applying their $NO_x$ reduction efficiency were proposed. The $NO_x$ reduction efficiency for the facilities consisting of the low $NO_x$ burners and the non-low $NO_x$ burners could be estimated with information about the reduction efficiency of each low $NO_x$ burners, the fuel consumption rate, and the heating value of fuel.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.64-71
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• 2013

In this study we designed a lean $NO_x$ trap (LNT) model with $GT-POWER^{TM}$ program and then the LNT model was compared to the bench flow reactor test results. This model consists of 9 kinetic reactions to represent the main steps of NO oxidation, $NO_x$ adsorption, $NO_x$ release and then its reduction. The comparison was performed on the operating conditions at the space velocity of 50,000 1/hr and 80,000 1/hr with the temperature range of $200^{\circ}C{\sim}500^{\circ}C$ with the even spaced temperature step of $50^{\circ}C$. The experimental results show that the $NO_x$ conversion efficiency was enhanced by the temperature up to $350^{\circ}C$ and then decayed at higher temperatures. The LNT model predicts the similar trend of the $NO_x$ conversion efficiency to the experimental results below $350^{\circ}C$, but overestimates above $350^{\circ}C$. This overestimation comes from the higher reduction efficiency which was obtained by the different reduction gas composition such as $C_3H_6$ in the model to replace $CH_4$, $C_2H_4$ in the bench test.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2874-2879
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• 2008

The Selective catalytic reduction(SCR) system is a highly-effective device of $NO_x$ reduction for diesel engines. Generally, the ammonia($NH_3$) generated from a liquid urea-water solution is used for the reductant. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency becomes lower, due to temperature window. And space velocity also affects to $NO_x$ conversion efficiency. This paper reviews a laboratory study to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the SCR system. The maximum conversion efficiency of $NO_x$ was indicated when the $NH_3$ to $NO_x$ ratio was 1.2 and the space velocity was $60,000\;h^{-1}$. The results of this paper contribute to improve overall $NO_x$ reduction efficiency and $NH_3$ slip.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.85-90
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• 2010

As the environmental regulation of vehicle emission is strengthened, investigations for $NO_x$ and PM reduction strategies are popularly conducted. Two current available technologies for continuous $NO_x$ reduction onboard diesel vehicles are Selective Catalytic Reduction (SCR) using aqueous urea and lean $NO_x$ trap (LNT) catalysts. The experiments were conducted to investigate the $NO_x$ reduction performance of SCR system which can control the ratio of $NO/NO_2$, temperature and SV(space velocity), and the model gas was used which is similar to a diesel exhaust gas. The maximum reduction efficiency is indicated when the $NO:NO_2$ ratio is 1:1 and the SV is 30,000 $h^{-1}$ in $300^{\circ}C$. Generally, ammonia slip from SCR reactors are rooted to incomplete conversion of $NH_3$ over the SCR. In this research, slip was occurred in 6cases (except low SV and $NO:NO_2$ ratio is 1:1) after SCR. Among 6 case of slip occurrence, the maximum conversion efficiency is observed when SV is 60,000 $h^{-1}$ in $400^{\circ}C$.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.179-187
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• 2008

A mathematical modeling of $NO_x$ reduction in $NH_3$-SCR process is conducted. The present deterministic model solves one-dimensional conservation equations of mass and species concentrations for channel flows and the catalytic reaction. NO and NO_2$ reactions by the vanadium catalyst in the presence of $NH_3$ are calculated with the rate expressions of Langmuir-Hinshelwood scheme. The modeling was validated with extensive empirical data regarding $NO_x$ reduction efficiency. Analysis of De-$NO_x$ sensitivity conducted with regard to oxygen and water yielded highly accurate prediction over a wide range of $NO_2/NO_x$ ratios from 0 to 1 in a temperature range of $200^{\circ}C{\sim}550^{\circ}C$. The $NO_x$ reduction largely depends on $NO_2/NO_x$ ratio at temperatures lower than $300^{\circ}C$. NO reduction efficiency is significantly augmented with increasing in $NH_3$/NO ratio at higher temperatures, whereas rather insensitive to the $NH_3$/NO ratio at lower temperatures.

• 한국가스학회지
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• 제19권5호
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• pp.20-28
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• 2015

탄화수소 선택적 촉매환원공정에서 ${\gamma}$-알루미나에 지지된 금속 산화물 촉매의 크기 및 형태에 따른 질소산화물 ($NO_x$) 저감 특성에 대해 조사하였다. 환원촉매로는 Ag, Cu 및 Ru를 사용하였으며, n-heptane을 환원제로 사용하였다. Ag/${\gamma}$-$Al_2O_3$ 촉매의 경우 온도범위 $250{\sim}400^{\circ}C$에서 20 nm>50 nm>80 nm 순으로 Ag의 크기가 작을수록 $NO_x$ 전환효율이 높게 나타났다. 금속 산화물 촉매의 형태에 따른 영향은 구형과 선형에 대해 살펴보았다. Ag와 Cu는 동일한 조건에서 선형이 구형보다 $NO_x$ 전환효율이 높은 것으로 나타났으나, Ru의 경우에는 형태에 따른 영향이 거의 관찰되지 않았다. 사용된 금속산화물 촉매 중에서 Ag를 사용했을 때 $NO_x$ 저감효율이 가장 높았으며, 선형의 Ag를 사용했을 때 $300^{\circ}C$의 반응온도에서 대부분의 $NO_x$를 제거할 수 있었다. Cu와 Ru 촉매상에서는 NO가 환원되기보다는 $NO_2$로의 산화반응이 우세하여 전체적으로 $NO_x$ 저감효율이 낮게 나타났다.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.68-76
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• 2008

Diesel $NO_x$ reduction by $NH_3$-SCR in conjunction with the effective oxidation precatalyst was analytically investigated. Physicochemical processes in regard to $NH_3$-SCR $NO_x$ reduction and catalytic NO-$NO_2$ conversion are formulated with detailed descriptions on the commanding reactions. A unified model is correctly validated with experimental data in terms of extents of $NO_x$ reduction by SCR and NO-$NO_2$ conversion by DOC. The present deterministic model based on the rate expressions of Langmuir-Hinshelwood reaction scheme finds a conversion extent directly. A series of numerical experiments concomitant with parametric analysis of the $NO_x$ reduction was conducted. $NO_x$ reduction is promoted in proportion to DOC volume ar lower temperatures and an opposite holds at lower space velocity and intermediate temperatures. $NO_x$ conversion is weakly correlated to the space velocity and the DOC volume at higher exhaust temperature. In DOC-SCR system, the $NO_x$ reduction efficiency depends on the $NH_3/NO_x$ ratio.

• 공업화학
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• 제29권1호
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• pp.103-111
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• 2018

본 연구에서는 온도가 큰 폭으로 변화하는 배기가스에 대응하기 위하여 플라즈마 촉매 공정을 이용하여 넓은 온도범위($150{\sim}500^{\circ}C$)에서 질소산화물($NO_x$)의 전환효율을 향상시키고자 하였다. 촉매 자체의 활성이 높은 고온에서는 $NO_x$저감이 효과적으로 일어나므로 고온 영역에서는 플라즈마 발생을 중지한 채 운전하고, 저온영역에서는 촉매상에 플라즈마를 발생시켜 $NO_x$ 전환효율을 증가시켰다. 촉매의 종류, 반응온도, 환원제(n-헵테인)의 농도 및 에너지 밀도의 변화가 $NO_x$ 전환효율에 미치는 영향을 조사하였다. 다양한 촉매를 비교분석한 결과, 고온에서 촉매에 의한 $NO_x$ 전환효율은 $Ag-Zn/{\gamma}-Al_2O_3$ 촉매의 경우가 90% 이상으로 가장 우수하였다. 저온 영역에서는 탄화수소 선택적 환원 공정에 의해 $NO_x$가 거의 제거되지 않았으나, 플라즈마를 촉매상에서 발생시킬 경우 약 90%의 높은 $NO_x$ 전환효율을 나타내었다. 배기가스의 온도변화에 대응하여 플라즈마를 촉매상에 생성시켜 운전할 경우 $150{\sim}500^{\circ}C$에서 $NO_x$ 전환효율을 높게 유지할 수 있다.

• 에너지공학
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• 제10권4호
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• pp.363-369
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• 2001

중급규모의 가스화 복합/열병합 플랜트의 공정설계와 성능평가를 수행하였다. 설계된 플랜트 공정을 바탕으로 가스터빈 연소기에 비포화 또는 포화된 질소를 분사시키거나 가스연료를 포화시키는 여러 가지 $NO_x$ 저감 기술들을 시도하여, $NO_x$ 저감 기법이 $NO_x$ 배출량에 미치는 영향과 플랜트의 출력, 효율 및 안정성에 미치는 영향을 동시에 검토하였다. 가스 연료의 포화보다는 질소의 분사를 통한 $NO_x$ 저감효과가 더욱 현저하며, 질소분산 시 포화된 질소를 사용하는 경우 $NO_x$ 저감 효과는 더욱 향상되었다. 또한 $NO_x$ 저감 기법의 적용은 $NO_x$ 배출량의 감소와 더불어 플랜트의 출력 및 효율 향상도 수반하나, 가스터빈의 불안정한 운전을 초래할 수도 있었다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.