• Title/Summary/Keyword: $NO_{x}$

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Control Oriented Storage and Reduction Modeling of the Lean NOx Trap Catalyst (제어를 위한 Lean NOx Trap의 흡장 및 환원 모델링)

  • Lee, Byoungsoo;Han, Manbae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.2
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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.

A Numerical Study on the $NO_{x}$ Reduction in 500MW Pulverized Coal Tangential Firing Boiler (500MW급 접선분사형 미분탄보일러의 $NO_{x}$ 저감에 관한 수치해석적 연구)

  • Choi, Choeng-Ryul;Kang, Dae-Woong;Kim, Chang-Nyung;Park,, Man-Heung;Kim, Kwang-Chu;Kim, Jong-Kill
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.967-972
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    • 2001
  • The emission of $NO_{x}$ during coal combustion is a major reason of environment impact. $NO_{x}$ is an acid rain precursor and participates in the generation of smog through ozone production. $NO_{x}$ can be divided into thermal $NO_{x}$, fuel $NO_{x}$ and prompt $NO_{x}$. Thermal $NO_{x}$ is formed in a highly temperature condition dependent. Fuel $NO_{x}$ is dependent on the local combustion characteristics and initial concentration of nitrogen bound compound, while prompt $NO_{x}$ is formed in a significant quantity in some combustion environments, such as low temperature and short residence times. This paper presents numerical simulation of the flow and combustion characteristics in the furnace of a tangential firing boiler of 500MW with burners installed at the every comer of the furnace. The purpose of this paper is to investigate the reduction of $NO_{x}$ emission in a 500MW pulverized coal tangential firing boiler with different OFA's and burner angles. Calculations with different air flow rates of over fired air(OFA) and burner angles are performed.

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The Methods Calculating the Reduction Efficiency of Nitrogen Oxide for the Facilities Including the Low NOx Burners (저녹스 버너 설치 시설의 질소산화물 저감 효율 산정 방법)

  • Lee, Ki Yong;Talukder, Niladri
    • 한국연소학회:학술대회논문집
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    • 2015.12a
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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.

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Evaluation Study on the Effects of $NO_x$ Reduction Techniques on the Performance and the Emission Characteristics of Medium Size Gasification Combined Cycle Plant (중급 규모 가스화 복합발전 플랜트의 $NO_x$ 저감 방식이 성능 및 환경특성에 미치는 영향에 관한 평가 연구)

  • Lee, Chan;Seo, Je-Young
    • Journal of Energy Engineering
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    • v.10 no.4
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    • pp.363-369
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    • 2001
  • Process design and performance evaluation were made for medium-size gasification combined/cogeneration plant. Based on the designed plant process configuration, the effects of $NO_x$ reduction techniques on the $NO_x$ emission, the power output, the efficiency and the stability of plant are investigated by applying various $NO_x$ reduction methods such as unsaturated/saturated nitrogen injection and fuel saturation of gas turbine combustor. The $NO_x$ reduction by nitrogen injection is more remarkable than that by fuel saturation, and its effect can be more enhanced by using saturated nitrogen. In addition, the applications of $NO_x$ reduction techniques accompany the improvement of plant power output and efficiency with the decrease of $NO_x$ emission, while it can cause unstable gas turbine operation.

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A Study of $NO_x$ Reduction in Stage Combustion (단계적 연소의 $NO_x$ 저감에 대한 연구)

  • 채재우;전영남;이운영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.6
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    • pp.1556-1571
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    • 1993
  • Nitrogen oxides ($NO_x$) are air pollutants which are generated from the combustion of fossil fuels. Stage combustion is an effective method to reduce $NO_x$ emissions. The effects of $NO_x$ reduction by stage combustion in a pilot scale combustor(6.6kW) have been investigated using propane gas flames laden with NH$_{3}$ as Fuel-N. The results in this study are follows; (1) $NO_x$ emissions are dependent on the reducing environment of fuel-rich zone regardless of total air ratio. The maximum $NO_x$ reduction is at the stoichiometric ratio of 0.8 to 0.9 in the reducing zone. (2) $NO_x$ reduction is maximum when burnout air is injected at the point where the oxygen in reducing zone is almost consumed. (3) $NO_x$ reduction is dependent upon the temperature of reducing zone with best effect above 950.deg. C in the reducing zone. (4) The fuel stage combustion is more effective to reduce $NO_x$ formation in the wide range of stoichiometric ratio than two stage combustion. (5) The results of this study could be utilized mainly in a design strategy for low $NO_x$ emission from the combustion of high fuel-nitrogen in energy sources ratio than as an indication of the absolute levels of $NO_x$ which can be achieved by stage combustion techniques in large scale facilities.

An Experimental Study on Flame and $NO_x$ Emission Characteristics of Front Mixing Premix Combustor ($NO_x$ 선단 예혼합 연소기의 화염 및 $NO_x$ 배출 특성 연구)

  • Shin, Myung-Chul;Kim, Se-Won;Mun, Min-Uk
    • Journal of the Korean Society of Combustion
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    • v.11 no.2
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    • pp.22-27
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    • 2006
  • This experimental study has been mainly motivated to obtain generally applicable design correlation for the front mixing premix combustor. The design concept of the front mixing premix combustor is to minimize thermal $NO_x$ and prompt $NO_x$ formation by maintaining low peak flame temperature, and nearly uniform flame temperature through rapid mixing process near the ignition point. The present experimental results clearly indicate that the front mixing premix combustor yields the $NO_x$ level lower than 43 ppm $NO_x$ emissions and the nearly uniform temperature distribution.

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The Effect of an Oxidation Precatalyst on the $NO_x$ Reduction by $NH_3$-SCR Process in Diesel Exhaust ($NH_3$-SCR 방법에 의한 디젤 배기 내 De-$NO_x$ 과정에서의 DOC에 의한 영향과 저감 성능 변화)

  • Jung, Seung-Chai;Yoon, Woong-Sup
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.5
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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.

Determination of an LNT Regeneration Condition Based on a NOx Storage Fraction in a 2.2L Direct Injection Diesel Engine (2.2L 디젤 엔진에서 NOx 흡장률 기반 LNT 재생 조건 결정)

  • Chun, Bongsu;Lee, Jungwoo;Han, Manbae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.3
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    • pp.345-351
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    • 2016
  • This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

A Performance Modeling of the Lean NOx Trap Catalyst with GT-POWERTM (GT-POWERTM를 이용한 Lean NOx Trap 촉매 성능 모델링)

  • Kim, Hyunjun;Han, Manbae;Jeon, Ji-Yong;Kim, Tae-Min
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.6
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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.

On the $NO_x$ in Direct Injection diesel engine (직접분사식 디이젤의$NO_x$에 관하여)

  • 안수길
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.12 no.1
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    • pp.1-6
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    • 1976
  • To investigate the relation of $NO_x$ emission and consumption rate in a direct injection diesel engine with a multihole nozzle under same fuel consumption and rpm, a naphthyl ethylenediaming method on NO, emission and Tektronix oscilloscop on the indicator diagrams have been used. Comparisons of the $NO_x$ emission and fuel consumption rate made on various conditions have led to the fllowing results. 1. The higher the injection pressure in the later injection time the lower $NO_x$ emission and the fuel consumption rate have been attained. 2. By the change of nozzle hole diameter under the same injection pressure, the $NO_x$ emission was much more lowered in the small diameter than large one, but fuel consumption rate was in inverse proption to the $NO_x$ emission. 3. The effect of injection spray angle, $\frac{1_n}{d_n}$ on $NO_x$ emission, fuel consumption rate under same injection time and injection pressure was neglectable.

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