• Title/Summary/Keyword: NOx Reduction Ratio

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The Numerical Study on the Flow Control of Ammonia Injection According to the Inlet NOx Distribution in the DeNOx Facilities (탈질설비 내에서 입구유동 NOx 분포에 따른 AIG유동제어의 전산해석적 연구)

  • Seo, Deok-Cheol;Kim, Min-Kyu;Chung, Hee-Taeg
    • Clean Technology
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    • v.25 no.4
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    • pp.324-330
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    • 2019
  • The selective catalytic reduction system is a highly effective technique for the denitrification of the flue gases emitted from the industrial facilities. The distribution of mixing ratio between ammonia and nitrogen oxide at the inlet of the catalyst layers is important to the efficiency of the de-NOx process. In this study, computational analysis tools have been applied to improve the uniformity of NH3/NO molar ratio by controlling the flow rate of the ammonia injection nozzles according to the distribution pattern of the nitrogen oxide in the inlet flue gas. The root mean square of NH3/NO molar ratio was chosen as the optimization parameter while the design of experiment was used as the base of the optimization algorithm. As the inlet conditions, four (4) types of flow pattern were simulated; i.e. uniform, parabolic, upper-skewed, and random. The flow rate of the eight nozzles installed in the ammonia injection grid was adjusted to the inlet conditions. In order to solve the two-dimensional, steady, incompressible, and viscous flow fields, the commercial software ANSYS-FLUENT was used with the k-𝜖 turbulence model. The results showed that the improvement of the uniformity ranged between 9.58% and 80.0% according to the inlet flow pattern of the flue gas.

Numerical Simulation on the Effects of Air Staging for Pulverized Coal Combustion in a Tangential-firing Boiler (접선연소식 보일러에서 미분탄 연소 시 공기 배분의 영향에 대한 전산해석연구)

  • Kang, Kieseop;Ryu, Changkook
    • Korean Chemical Engineering Research
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    • v.55 no.4
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    • pp.548-555
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    • 2017
  • This study investigated the influence of air staging on combustion and NOx emission in a tangential-firing boiler at a 560 MWe capacity. For air staging, the stoichiometric ratio (SR) for the burner zone was varied from 0.995 to 0.94 while the overall value was fixed at 1.2. The temperature and heat flux in the burner zone and upper furnace corresponded to the distribution of SR, while the total boiler efficiency remained similar. The NOx emission at the furnace exit was reduced by up to 20% when the SR in the burner zone decreased to 0.94. However, the amount of unburned carbon and slagging propensity was not noticeably influenced by the changes in the SR of the burner zone. Therefore, it was favorable to lower the SR of the burner zone for reduction of NOx emission.

A Study on Exhaust Gas Characteristics of Off-road Mechanical Diesel Engine According to EGR Map Application (Off-Road 기계식 디젤엔진의 EGR Map 적용에 따른 배출가스 특성 연구)

  • Kim, HoonMyung;Kang, JeongHo;Han, DaHye;Ha, HyeongSoo;Jung, HakSup;Pyo, SuKang;Ahn, JuengKyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.8
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    • pp.665-670
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    • 2014
  • Because reducing atmospheric pollution is becoming a serious issue, studies are actively focusing on exhaust gas reduction. This study was conducted to determine the emission characteristics when applying an EGR system, the main approach used for NOx reduction, to an off-road mechanical diesel engine. For the application of the EGR system, the emission characteristics in consideration of the engine conditions were analyzed. The optimum EGR ratio for NOx emission reduction was determined by applying variable EGR conditions for each engine speed condition. Considering the above process, the emission characteristics of the modified EGR condition are compared with those of other conditions (non-EGR and existing EGR condition) in the NRTC mode. Consequently, NOx emission was reduced by around 42 compared with the non-EGR condition when using the modified EGR map.

Improving Compression and Throat Ratios of Combustion Chamber for Reduction of Exhaust Emissions for a Swirl Chamber Type Diesel Engine (와류실식 디젤기관의 배기배출물 저감을 위한 연소실의 압축비 및 분구면적비 개선)

  • Lee, Chang-Kyu;Huh, Yun-Kun;Seo, Sin-Won
    • Korean Journal of Agricultural Science
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    • v.37 no.3
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    • pp.501-508
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    • 2010
  • A swirl chamber type diesel engine attachable to 18 kW agricultural tractors was improved to reduce exhaust emissions. Compression ratio and throat area ratio of the combustion chamber were varied to determine optimum combustion conditions. Tests were composed of full load and 8-mode emission tests. Compression ratio was fixed as 21, but the swirl chamber volume was increased by 3.8%. Output power, torque, specific fuel consumption, exhaust gas temperature, and smoke level were not considerably different for compression ratios of 21.5 (reference condition) and 21 (test condition), while NOx, HC, CO and PM levels for the compression ratio of 21 were decreased by 11%, 46%, 28%, 11%, respectively, from those for the compression ratio of 21.5. The tests were also conducted with a compression ratio of 22 and 4.3% increased chamber volume. Output power, torque, exhaust gas temperature and smoke level were greater, while specific fuel consumption was less for the compression ratio of 22 than those for the compression ratio of 21.5. Increase of compression ratio decreased HC and CO levels by 24%, 39%, but increased NOx and PM levels by 24%, 39%. Based on these results, a compression ratio of 21 was selected as an optimum value. Then, full load tests with the selected compression ratio of 21 were carried out for different throat ratios of 1.0%, 1.1%, 1.2%. Output power and torque were greatest and smoke was lowest when throat area ratio was 1.1%, which satisfied the target values of specific fuel consumption (less than 272 g/$kW{\cdot}h$) and exhaust gas temperature (less than $550^{\circ}C$). Therefore, a throat area ratio of 1.1% was selected as an optimum value.

SOx and NOx removal performance by a wet-pulse discharge complex system (습식-펄스방전 복합시스템의 황산화물 및 질소산화물 제거성능 특성)

  • Park, Hyunjin;Lee, Whanyoung;Park, Munlye;Noh, Hakjae;You, Junggu;Han, Bangwoo;Hong, Keejung
    • Particle and aerosol research
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    • v.15 no.1
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    • pp.1-13
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    • 2019
  • Current desulfurization and denitrification technologies have reached a considerable level in terms of reduction efficiency. However, when compared with the simultaneous reduction technology, the individual reduction technologies have issues such as economic disadvantages due to the difficulty to scale-up apparatus, secondary pollution from wastewater/waste during the treatment process, requirement of large facilities for post-treatment, and increased installation costs. Therefore, it is necessary to enable practical application of simultaneous SOx and NOx treatment technologies to remove two or more contaminants in one process. The present study analyzes a technology capable of maintaining simultaneous treatment of SOx and NOx even at low temperatures due to the electrochemically generated strong oxidation of the wet-pulse complex system. This system also reduces unreacted residual gas and secondary products through the wet scrubbing process. It addresses common problems of the existing fuel gas treatment methods such as SDR, SCR, and activated carbon adsorption (i.e., low treatment efficiency, expensive maintenance cost, large installation area, and energy loss). Experiments were performed with varying variables such as pulse voltage, reaction temperature, chemicals and additives ratios, liquid/gas ratio, structure of the aeration cleaning nozzle, and gas inlet concentration. The performance of individual and complex processes using the wet-pulse discharge reaction were analyzed and compared.

Effects of Pilot Injection Method Following the Main Injection on Ignition Promotion and Exhaust Gas Reduction in a Diesel-Fueled HCCI Engine (디젤 예혼합압축착화엔진에서 주연료 분사 후 점화 연료 분사 방법을 통한 점화 촉진과 배기가스 개선 효과)

  • Kook, Sang-Hoon;Bae, Choong-Sik
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.27-32
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    • 2003
  • Diesel-Fueled HCCI(Homogeneous Charge Compression Ignition) Engine is an advanced combustion process explained as a premixed charge of diesel fuel and air is admitted into the cylinder and compression ignited. It has possibility to reduce NOx by spontaneous auto-ignition at multiple points that allows very lean combustion resulting in low combustion temperatures. Also PM could be reduced by the premixed combustion and no fuel-rich zones. But HCCI couldn't be realized because of the difficulties in vaporizing the diesel, control of combustion phase directly. To solve these problems, new fuel injection strategy, explained as the pilot fuel injection to promote ignition near TDC following the main fuel injection at the extremely advanced timing, is applied during the compression ratio is varied from 18.9:1 to 27.7:1 This is not a pilot fuel to promote the ignition but also the direct control method of the combustion phase. Experimental result shows the pilot fuel injection promote the ignition and the compression ignition of the HCCI engine is achieved as compression ratio becomes higher. Also there is an optimal pilot fuel injection timing for the HCCI combustion. NOx is reduced more than 90% compared to DI-Diesel case but PM and THC emission needs more investigation.

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Estimation of the Exhaust Characteristics of Biodiesel Used in Diesel Engine (디젤엔진에서 바이오디젤의 배기가스 특성 평가)

  • Baek, Seok Heum;Yoon, Jeong Hwan;Jung, Woo Sung;Ha, Hyeong Soo;Chung, Sung Sik;Yeom, Jeong Kuk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.2
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    • pp.129-137
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    • 2014
  • In this study, the characteristics of exhaust gas as a function of the biodiesel mixing ratio were investigated. Diesel and waste oil were used for preparing mixed fuel, and the ratios of the mixed fuel were varied in the BD3~BD100 range. The injection pressures(${\Delta}p_{inj}$) was considered as an experimental variable and was set to 400 bar, 600 bar, 800 bar, 1000 bar, and 1200 bar. Furthermore, for quantitatively analyzing the characteristics of exhaust gas(NOx and Soot), the concepts of Pearson correlation coefficient and Spearman rank-order correlation coefficient based on statistics were introduced. Consequently, it was found that the correlation of the emission of NOx and Soot is linear, and the Pearson and Spearman coefficients are -0.732 and -0.724, respectively, under all analysis conditions. Especially, for the injection pressure of 800 bar, a simultaneous reduction in NOx and Soot emission is possible by controlling the biodiesel mixing ratio. This is because the correlation coefficients of NOx and Soot emissions were nearly 0, as the Pearson correlation coefficient was -0.089.

Combustion Characteristics of Non-premixed VIStA Burner in Once-Through-Type Boiler (관류보일러 연소실에서 비예혼합 VIStA 버너의 연소 특성)

  • Ahn, Joon;Kim, Hyouck-Ju;Choi, Kyu-Sung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.5
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    • pp.547-552
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    • 2010
  • A modified VIStA (vortex inertial staged air) burner was developed and used in a once-through-type boiler. For safety, the combustion in this burner is of the non-premixed type. An air damper is installed to control the distribution of air to each combustion chamber. The effects of the air-fuel ratio and air distribution on NOx formation were investigated. The newly modified VIStA burner gives NOx reduction effect by maximum 20% in the combustion chamber of a boiler, while it yields more uniform flame than the conventional burner.

Co-combustion Characteristics of Mixed Coal with Anthracite and Bituminous in a Circulating Fluidized Bed Boiler (순환유동층 보일러에서 무연탄-유연탄의 혼합연소 특성)

  • Jeong, Eui-Dae;Moon, Seung-Jae
    • Plant Journal
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    • v.6 no.2
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    • pp.70-77
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    • 2010
  • This study investigated the characteristics of co-combustion of mixed anthracite (domestic and Vietnam) and bituminous coal (Sonoma, Australia) at circulating fluidized bed boiler in Donghae thermal power plant when mixing ratio of bituminous coal is variable. Co-combustion of bituminous coal contributes to improvement in general combustion characteristics such as moderately retaining temperature of furnace and recycle loop, reducing unburned carbon powder, and reducing discharge concentration of NOx and limestone supply owing to improvement in anthracite combustibility as the mixing ratio was increased. However, bed materials were needed to be added externally when the mixing ratio exceeded 40% because of reduction in generating bed materials based on reduction in ash production. When co-combustion was conducted in the section of 40 to 60% in the mixing ratio while the supplied particles of bituminous coal was increased from 6 mm to 10 mm, continuous operation was shown to be possible with upper differential pressure of 100 mmH2O (0.98 kPa) and more without addition of bed materials for the co-combustion of mixed anthracite and bituminous coal (to 50% or less of the ratio) and that of domestic coal and bituminous coal (to 60% of the ratio).

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A numerical study of the air fuel ratio effect on the combustion characteristics in a MILD combustor (공연비 변화가 MILD 연소 특성에 미치는 영향에 관한 해석적 연구)

  • Ha, Ji-Soo;Kim, Tae-Kwon;Shim, Sung-Hoon
    • Journal of Korean Society of Environmental Engineers
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    • v.32 no.6
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    • pp.587-592
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    • 2010
  • A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10 m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30 m/s. The air velocity 18 m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10 m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10 m/s is biased to the air nozzle side and for the case of air injection velocity 30 m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20 m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20 m/s are lower than the cases with air injection velocity 10, 30 m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.