• Title/Summary/Keyword: NOx Reduction Ratio

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Application of SNCR/SCR Combined process for effective operation of SCR Process

  • 최성우;최상기
    • Journal of Environmental Science International
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    • v.12 no.1
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    • pp.47-54
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    • 2003
  • This paper have examined the optimum combination of SNCR and SCR by varying SNCR injection temperature and NSR ratio along with SCR space velocity. NOx reduction experiments using a SNCR/SCR combined process have been conducted in simple NO/NH$_3$/O$_2$ gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial NOx concentration was 500 ppm in the presence of 5% O$_2$. Commercial catalyst, sulfated V$_2$O$\_$5/-WO$_3$/TiO$_2$, was used for SCR NOx reduction. The residence time and space velocity were around 1.67 sec, 2,400 h$\^$-1/ and 6,000 h$\^$-1/ in the SNCR and SCR reactors, respectively. SNCR NOx reduction effectively occurred in a temperature window of 900-950$^{\circ}C$. About 88% NOx reduction was achieved with an optimum temperature of 950$^{\circ}C$ and NSR=1.5. SCR NOx reduction using commercial V$_2$O$\_$5/-WO$_3$-SO$_4$/TiO$_2$ catalyst occurred in a temperature window of 200-450$^{\circ}C$ 80-98% NOxreduction was possible with SV=2400 h$\^$-1/ and a molar ratio of 1.0-2.0. A SNCR/SCR(SV=6000 h$\^$-1/) combined process has shown same NOx reduction compared with a stand-alone SCR(SV=2400 h$\^$-1/) unit process of 98% NOx reduction. The NH$_3$-based chemical could routinely achieve SNCR/SCR combined process total NOx reductions of 98% with less than 5 ppm NH$_3$ slip at NSR ranging from about 1.5 to 2.0, SNCR temperature of 900$^{\circ}C$-950$^{\circ}C$, and SCR space velocity of 6000 h$\^$-1/. Particularly, more than 98% NOx reduction was possible using the combined process under the conditions of T$\_$SNCR/=950$^{\circ}C$, T$\_$SCR/=350$^{\circ}C$, 5% O$_2$, SV=6000 h$\^$-1/ and NH$_3$/NOx=1.5. A catalyst volume was about three times reduced by SNCR/SCR combined process compared with SCR process under the same controlled conditions.

Numerical Modeling of Vanadia-based Commercial Urea-SCR plus DOC Systems for Heavy-duty Diesel Exhaust Aftertreatment Systems (바나듐 기반의 Urea-SCR과 DOC가 결합된 Heavy-Duty 디젤 배출가스 후처리 시스템의 SCR De-NOx 성능 향상에 관한 수치해석 연구)

  • Yun, Byoung-Kyu;Kim, Chong-Min;Kim, Man-Young;Cho, Gyu-Baek;Kim, Hong-Suk;Jeong, Young-Il
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.2
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    • pp.24-30
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    • 2010
  • In this study, numerical experiments were carried out to estimate the SCR De-NOx performance in DOC plus SCR systems. The SCR De-NOx phenomena are described by Langmuir-Hinshelwood reaction scheme. After validating the present approach by comparing the present results with the experimental results, such various parameters as space velocity, $H_2O$ concentration, $NO_2$/NOx ratio and relative volume of DOC are explored to increase the SCR De-NOx performance. The results indicate that SCR De-NOx performance largely depends on space velocity and $NO_2$/NOx ratio, especially below $200^{\circ}C$. SCR De-NOx performance is seriously affected by relative volume of DOC with SCR due to increasing in $NO_2$/NOx ratio at below $250^{\circ}C$.

Improving the performance of a Medium Speed Diesel Engine Using Miller Cycle (Miller 사이클을 이용한 중형 디젤 기관 성능 개선)

  • 김동훈;김기두;하지수;김호익;김주태
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.2
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    • pp.248-255
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    • 2002
  • Miller cycle was studied and analyzed by engine performance simulation to achieve very low fuel consumption and to meet the IMO NOx regulation on a medium speed diesel engine. Based on the performance simulation results the intake valve closing time for HYUNDAI HiMSEN 6H21/32 engine was set at 0deg.ABDC(After Bottom Dead Center). Also, the simulation results indicated that significant NOx reduction could be achieved with low reduction of fuel consumption. The performance simulation investigated the effect of compression ratio and turbocharger on fuel consumption and NOx concentration in combination with Miller cycle. The results indicated a significant reduction of fuel consumption with keeping NOx concentration. The results of performance simulation were compared with measured data to verify simulation results. The comparison showed the maximum error was 2.34% in exhaust temperature. Also, the experimental result showed that improvement in BSFC(Brake Specific Fuel Consumption) was 5.8g/kwh with keeping NOx level similar to simulation result.

NOx Emission Characteristics of 100kW Gas Burner by FGR (100kW용량가스 연소기의 FGR에 의한 Nox발생 특성 연구)

  • Kim, K.L.;Kim, H.J.;Park, B.S.;Kim, J.J.
    • 한국연소학회:학술대회논문집
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    • 2001.11a
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    • pp.1-7
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    • 2001
  • FGR is one of the most widely used methods of NOx reduction in the combustion process. It was investigated the effect of FGR, excess air ratio, peak temperature and firing rate on NOx emission in this study. 100kW burner and LNG were adopted in this experiment. NOx emission was notably decreased with the increase of FGR, however CO emission was also drastically increased in the 25% FGR. And excess air ratio, peak temperature and firing rate did not affect the NOx emission appreciably in the normal operating condition.

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Low Temperature Selective Catalytic Reduction of NOx over V2O5/TiO2 Catalyst Doped with Mn (Mn이 첨가된 V2O5/TiO2 촉매상에서 질소산화물의 저온 SCR 특성)

  • Cheon, Tae Jin;Choe, Sang Gi;Choe, Seong U
    • Journal of Environmental Science International
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    • v.13 no.6
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    • pp.537-542
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    • 2004
  • $V_{2}O_{5}/TiO_{2}$ catalysts promoted with Mn were prepared and tested for selective catalytic reduction of NOx in $NH_3.$ The effects of promoter content, degree of catalyst loading were investigated for NOx activity while changing temperatures, mole ratio, space velocity and $O_2$ concentration. Among the various $V-{2}O_{5}$ catalysts having different metal loadings, $V-{2}O_{5}$(1 wt.%) catalyst showed the highest activity(98%) under wide temperature range of $200-250^{\circ}C.$ When the $V-{2}O_{5}$ catalyst was further modified with 5 wt.% Mn as a promoter, the highest activity(90-47%) was obtained over the low temperature windows of $100-200^{\circ}C.$ From Mn-$V_{2}O_{5}/TiO_{2}$, it was found that by addition of 5 wt.% Mn on $V_{2}O_{5}/TiO_{2}$ catalyst, reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and NOx reduction. According to the results, NOx removal decreased for 10%, but the reaction temperature down to $100^{\circ}C.$

The Effects of Exhaust Gas Recirculation on Non-premixed Combustion (배기가스 재순환이 비예혼합 연소시스템에 미치는 영향)

  • Yu, Byeonghun;Kim, Jinsu;Lee, Chang-Eon
    • Journal of the Korean Society of Combustion
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    • v.19 no.3
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    • pp.26-33
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    • 2014
  • We examined the characteristics of $NO_x$ emission for CH4/air non-premixed flames using the exhaust gas recirculation(EGR) methods, which are the air-induced EGR(AI-EGR) and fuel-induced EGR(FI-EGR) methods. Our experimental results show that the $NO_x$ emission index($EI_{NOx}$) decreased with increasing EGR ratio. In the range needed to form a stable flame, the reduction rate of $EI_{NOx}$ for the FI-EGR method was approximately 29% when the EGR ratio was 20%, and the reduction rate for the AI-EGR method was approximately 28% with 25% of the EGR ratio. According to the flame structure based on numerical results, high temperature regions for the FI-EGR method were narrower and lower than those for the AI-EGR method at the same EGR ratio. Furthermore, based on the experimental results for swirl flames, the reduction rate of $EI_{NOx}$ for the FI-EGR method was approximately 49% with 15% of the EGR ratio, while the maximum reduction rate for AI-EGR method was approximately 45% with 25% of the EGR ratio. Consequently, we verified that the FI-EGR method was more effective than the AI-EGR method in reducing $NO_x$ emission for non-premixed flames with EGR. We expect that the results of this study will provide fundamental information relating to hybrid combustion systems, which can be used in the design of combustion systems in the future.

A Study on the Simultaneous Reduction of NOx and Soot with Diesel-Methanol Stratified Injection System in a Diesel Engine (Part II : Combustion and Exhaust Characteristics of Stratified Injection) (층상연료분사(경유/메탄올)를 이용한 디젤엔진의 NOx와 Soot 동시 저감에 관한 연구 (제2보 : 층상분사 연소특성 및 배기 특성))

  • Kang, B.M.;Lee, T.W.;Chung, S.S.;Ha, J.Y.
    • Journal of ILASS-Korea
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    • v.7 no.1
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    • pp.7-13
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    • 2002
  • This paper is study on simultaneous reduction of NOx and soot for direct injection diesel engine using high and low cetane fuels. The stratified injection system was applied for diesel engine to use high and low cetane fuel. In this study, diesel fuel was used as high cetane fuels, methanol was used as low cetane fuels. Some parts of the injection system, ie. Nozzle holder. delivery vale, was remodeled to inject dual fuel sequentially from one injector. The leak injection quantity ratio of dual fuel was certificated by volumetric ratio at injection quantity experiment. According as concentration of low cetane fuel was varied, combustion experiment was performed using Toroidal and Complex chamber. Also, exhaust gas and fuel consumption were measured at the same time. Simultaneous reduction of NOx and soot was achieved at complex chamber regardless of concentration of low cetane fuel. However, according as concentration of low cetane fuel was increased, THC and CO was increased.

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Combustion Radicals and NOx Emissions Characteristics by Control of Partially Premixed Flames (부분적 예혼합화염제어에 의한 연소 라디칼 및 NOx 배출물 특성)

  • Kim, Tae-Gwon;Jang, Jun-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.4
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    • pp.561-569
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    • 2002
  • This paper presents an investigation on $C_2$, CH, OH radicals and NOx emissions in partially premixed flames with acoustic excitation. The radicals are visualized by the digital image technique with optical filters and ICCD camera while NOx emissions are determined by a chemiluminescent detection(NOx analyser). The measurements are made in flames with an overall equivalence ratio (${\phi}_o$) 0.5 and a center tube equivalence ratio(${\phi}_c$) varing from 1.1 to 5.0 for a constant fuel flow rate. In the case of excitation, the visual shape of the flame is changed from laminar to turbulent-like flames. Images of $C_2$, CH, and OH radicals resemble those of the flame appearances as the excitation phase is varied, and the radicals generated at the upstream are convected toward the downstream. It is inferred that the flame characteristics is affected by the flow characteristics of air-fuel mixture. In the case of acoustic excitation, OH radicals are much increased relative to unexcitation. From the radicals and flame visualization under acoustic excitation, the reduction of flame length affects the shorter residence time of center tube mixture, and significantly influences the NOx reduction.

Experimental Investigation of NOX Reduction using a Hybrid Fuel Lean Reburning System (NOx 저감을 위한 하이브리드 연료희박 재연소 연구)

  • Kim, Hak-Young;Baek, Seung-Wook;Hwang, Chang-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.3
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    • pp.283-290
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    • 2010
  • The main goal of this study is to examine the use of a hybrid -fuel lean reburning system with air staging for $NO_X$ reduction. The experimental variables include the reburn fuel fraction, sizes of reburn- fuel-injection nozzles, oxygen enrichment ratio, and location of reburn- fuel- injection. The effect of the flow field induced by air- staging combustion on $NO_X$ reduction is considered, and then, the $NO_X$ reduction rate is compared with only fuel lean reburning system. On the basis of the effectiveness of each De-$NO_X$ process, the advantage of using the hybrid reburning system with air staging is determined and discussed.

Study on Coal Combustion Characteristics with 1MWth Test Facility (1MWth 실험연소로를 이용한 석탄의 연소특성 연구)

  • Jang, Gil Hong;Chang, In Gab;Jeong, Seok Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.11
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    • pp.1464-1472
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    • 1999
  • Design and operation of $1MW_{th}$ pulverized coal combustion testing facility are described. Also the influence of air staging on NOx emission and burnout of coal flames was investigated in this facility. The test facility consisted of coal feeding system, firing system and flue gas treatment system. A top-fired externally air staging burner was adopted in order to avoid influence of gravity on the coal particles and for easy maintenance. Distribution of temperature and chemical species concentration of coal flames could be measured in vertical pass of furnace. Main fuel was pulverized (83.4% less than $80{\mu}m$) Australian high bituminous coal. From variety of test conditions, overall excess air ratio was selected at 1.2(20% excess air). Tho study showed that increasing the staged air resulted in lower NOx omission, and it was suggested to be more than 40% of the total combustion air for the substantial NOx reduction. Sufficient burnout was not achievable when NOx emission was less than 500ppm. Also, the amount of core air did not influence tho NOx reduction.