• Title/Summary/Keyword: NOx

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Simultaneous Removal of NO and SO2 using Microbubble and Reducing Agent (마이크로버블과 환원제를 이용한 습식 NO 및 SO2의 동시제거)

  • Song, Dong Hun;Kang, Jo Hong;Park, Hyun Sic;Song, Hojun;Chung, Yongchul G.
    • Clean Technology
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    • v.27 no.4
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    • pp.341-349
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    • 2021
  • In combustion facilities, the nitrogen and sulfur in fossil fuels react with oxygen to generate air pollutants such as nitrogen oxides (NOX) and sulfur oxides (SOX), which are harmful to the human body and cause environmental pollution. There are regulations worldwide to reduce NOX and SOX, and various technologies are being applied to meet these regulations. There are commercialized methods to reduce NOX and SOX emissions such as selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR) and wet flue gas desulfurization (WFGD), but due to the disadvantages of these methods, many studies have been conducted to simultaneously remove NOX and SOX. However, even in the NOX and SOX simultaneous removal methods, there are problems with wastewater generation due to oxidants and absorbents, costs incurred due to the use of catalysts and electrolysis to activate specific oxidants, and the harmfulness of gas oxidants themselves. Therefore, in this research, microbubbles generated in a high-pressure disperser and reducing agents were used to reduce costs and facilitate wastewater treatment in order to compensate for the shortcomings of the NOX, SOX simultaneous treatment method. It was confirmed through image processing and ESR (electron spin resonance) analysis that the disperser generates real microbubbles. NOX and SOX removal tests according to temperature were also conducted using only microbubbles. In addition, the removal efficiencies of NOX and SOX are about 75% and 99% using a reducing agent and microbubbles to reduce wastewater. When a small amount of oxidizing agent was added to this microbubble system, both NOX and SOX removal rates achieved 99% or more. Based on these findings, it is expected that this suggested method will contribute to solving the cost and environmental problems associated with the wet oxidation removal method.

Fabrication of Stack-Structured Gas Sensor of LaCrxCo1-xO3/Li1.3Al0.3Ti1.7(PO4)3 and Its NOx Sensing Properties (LaCrxCo1-xO3/Li1.3Al0.3Ti1.7(PO4)3의 적층구조를 가지는 가스센서 제조와 그의 NOx 검지특성)

  • Lee, Young-Sung;Shimizu, Y.;Song, Jeong-Hwan
    • Korean Journal of Materials Research
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    • v.25 no.8
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    • pp.423-428
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    • 2015
  • Impedancemetric $NO_x$ (NO and $NO_2$) gas sensors were designed with a stacked-layer structure and fabricated using $LaCr_xCo_{1-x}O_3$ (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and $Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ plates as the solid-electrolyte transducer material. The $LaCr_xCo_{1-x}O_3$ layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and $NO_x$ sensing properties of the $LaCr_xCo_{1-x}O_3$ powders were investigated with powder X-ray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of $NO_x$ at $400^{\circ}C$ (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at $700^{\circ}C$, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the $LaCr_xCo_{1-x}O_3$powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the $LaCr_xCo_{1-x}O_3$ powders with $0{\leq}x<0.8$ had a rhombohedral symmetry. The size of the particles in the $LaCr_xCo_{1-x}O_3$powders increased from 0.1 to $0.5{\mu}m$ as the Co concentration increased. The sensing performance of the stack-structured $LaCr_xCo_{1-x}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to $NO_2$ gas. Compared to other impedancemetric sensors, the $LaCr_{0.8}Co_{0.2}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensor exhibited good reversibility and reliable sensingresponse properties for $NO_x$ gases.

Photochemical Conversion of NOX in Atmosphere by Photocatalyst Coated Mortar (광촉매 코팅한 모르타르를 이용한 대기 중 NOX의 광화학적 변환)

  • Hyeon Jin;Kyong Ku Yun;Hajin Choi;Kyo-Seon Kim
    • Korean Chemical Engineering Research
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    • v.61 no.2
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    • pp.240-246
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    • 2023
  • This study was performed to convert NOx in atmosphere by photochemical reaction utilizing the eco-friendly solar energy. The mortar specimen coated with photocatalyst was fabricated and the photochemical conversion efficiency of NOx was analyzed. The photocatalyst coated concrete was fabricated by first adding TiO2 photocatalyst on the bottom of mold first and next adding cement mortar and, then, curing the concrete mortar. The grease was sprayed on the bottom of mold in advance so that the concrete can be demolded easily after curing. The conversion efficiencies of NOx by photochemical reactions were investigated systematically by changing the process variable conditions of amount of TiO2 coating, UV-A light intensity, total gas flow rate, relative humidity and initial NOx concentration. It was confirmed that the photocatalyst coated concrete fabricated in this study could convert NOx successfully for various process conditions in atmosphere. In future, we believe this research result can be utilized as basic data to design the infrastructure of building, tunnel and road for controlling efficiently the air pollutants such as NOx, SOx, and VOCs.

Effect of Intermittent Plasma Discharge on the Hydrocarbon Selective Catalytic Reduction of Nitrogen Oxides (간헐적 플라즈마 방전이 질소산화물의 탄화수소 선택적 촉매환원에 미치는 영향)

  • Kyeong-Hwan Yoon;Y. S. Mok
    • Applied Chemistry for Engineering
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    • v.34 no.5
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    • pp.507-514
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    • 2023
  • The selective catalytic reduction (SCR) of nitrogen oxides (NOx) was investigated in a catalyst (Ag/γ-Al2O3) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NOx removal to several aldehydes. Compared to using the catalyst alone, higher NOx conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NOx reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NOx reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NOx reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NOx reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NOx reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.

Nitrogen oxide (NOX) and Sulfur Oxide (SOX) Removal Capacities of Textile FabricsCoated with Nano-pore Materials (나노 공극소재로 코팅된 모헤어의 질소산화물(NOX) 및 황산화물(SOX) 제거 성능평가)

  • Lee, Jae-Uk;Yang, Keun-Hyeok;Mun, Ju-Hyun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.157-158
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    • 2020
  • The present study examined the effectiveness of textile fabrics coated with nano-pore materials on removing the nitrogen oxide (NOX) and sulfur oxide (SOX) in the atmospheric environment. The tested approach is favorable for absorbing NOX and SOX, even under the washing condition.

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Study of the Optimal Calcination Temperature of an Al/Co/Ni Mixed Metal Oxide as a DeNOx Catalyst for LNT

  • Jang, Kil Nam;Han, Kwang Seon;Hong, Ji Sook;You, Young-Woo;Suh, Jeong Kwon;Hwang, Taek Sung
    • Clean Technology
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    • v.21 no.3
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    • pp.184-190
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    • 2015
  • Most of LNT catalysts use noble metals such as Pt for low temperature NOx oxidation but there is an economic weakness. For the purpose of overcoming this, this study is to develop DeNOx catalyst for LNT excluding PGM (platinum group metal) such as Pt, Pd, Rh, etc. To do so, Al/Co/Ni catalyst selected as a preliminary test is used to study fundamental property and NOx’s conversion according to calcined temperature. Ultimately, that is, Al/Co/Ni mixed metal oxide which does not use PGM is selected and physicochemical characterization is performed by way of XRD, EDS, SEM, BET and ramp test and NOx conversion is also analyzed. This study shows that all samples consist of mixed oxides of spinel structure of Co2AlO4 and NiAl2O4 and have enough pore volume and size for redox. But as a result of NH3-TPD test, it is desired that calcined temperature needs to be maintained at 700 ℃ or lower. Also only samples which are processed under 500 ℃ satisfied NO and NOx conversion simultaneously through ramp test. Based on this study’s results, optimum calcined temperature for Al/Co/Ni=1.0/2.5/0.3 mixed metal oxide catalyst is 500 ℃.

Experimental Evaluation of Developed Ultra-low NOx Coal Burner Using Gas in a Bench-scale Single Burner Furnace (Bench-scale 연소로에서 가스 혼소를 통한 초 저 NOx 석탄 버너 개발 연구)

  • Chae, Taeyoung;Lee, Jaewook;Lee, Youngjae;Yang, Won
    • Clean Technology
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    • v.28 no.2
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    • pp.117-122
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    • 2022
  • This study developed and tested an ultra-low NOx burner in an 80 kW combustion furnace. The experiment was conducted in an 80 kW single burner combustion furnace with changing the swirl numbers, total equivalence ratios, and primary/secondary oxidizer ratios. In this study, liquefied natural gas (LNG) was used as an auxiliary fuel to significantly reduce NOx production. In a thermal power plant, the amount of NOx generated during coal combustion is about 300 ppm. However, using the burner tested in this study, it was possible to reduce the amount of NOx generated via LNG co-firing to 40 ppm. If the input amount of the primary oxidizer is enough for the gas to be completely combusted and the gas and coal are added simultaneously, the combusted gas forms a high-temperature region at the burner outlet and volatilizes the coal. As a result, the N contained in the devolatilized coal is discharged. Therefore, when the coal is subsequently burned, the amount of NOx produced decreases because there is almost no N remaining in the coal. If a thermal power plant burner is developed based on the results of this study, it is expected that the NOx generation will be significantly lower in the early stage of combustion.

Performance Management of a DeNOx System for Stationary Sources and Regeneration Strategies of DeNOx Catalysts (고정원 탈질시스템의 성능관리와 탈질촉매 재생전략)

  • Kim, Moon Hyeon
    • Clean Technology
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    • v.22 no.3
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    • pp.141-153
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    • 2016
  • Numerous stationary NOx emission sources have employed a suitable deNOx technology that is typically selective catalytic reduction (SCR) of NOx by NH3 over V2O5/TiO2-based catalysts with on-demand monolithic structures. These structured catalysts undergo a time-on-deterioration of deNOxing activity on site. Thus, we need more efficient, more deactivation-tolerant, more economic deNOx systems and for which, their performance management is essential. This review has covered details of strategies to successfully manage the performance of SCR catalysts and timely replace them to new or rejuvenated ones. Key considerations to maintain the catalyst activity will be reviewed. Details of the sequential addition of new catalysts and the replacement of life-end catalysts and their regeneration will be discussed with general guidances to determine the time for such a replacement. Finally, a better way to get more economic approaches to deNOx system management will be proposed here.

Long-term Trend Analysis of NOx and SOx over in East Asia Using OMI Satellite Data and National Emission Inventories (2005-2015) (OMI 위성 자료와 국가 배출량 자료를 활용한 동아시아의 NOx, SOx 변화 장기 분석(2005-2015))

  • Seo, Jeonghyeon;Yoon, Jongmin;Choo, Gyo-Hwang;Kim, Deok-rae;Lee, Dong-Won
    • Korean Journal of Remote Sensing
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    • v.36 no.2_1
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    • pp.121-137
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    • 2020
  • Data from the Ozone Monitoring Instrument (OMI) satellite and national emission inventories were used in this study to analyze air quality in East Asia and estimate the impact of domestic and foreign emissions on South Korea's air quality, based on which future emissions were predicted. The concentration trends of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in East Asia from 2005 to 2015 showed that both substances were highest in North East China (NEC), followed by South East China (SEC) and Seoul Metropolitan Area (SMA). The average SO2 concentration was 1.63 times higher in NEC than in SMA. Analysis on the ratios of NO2/SO2 and NOx/SOx provides an indirect picture of the effect of transboundary air pollutants on atmospheric composition in Korea. The concentration ratio of NO2/SO2 in all study areas peaked in 2013 and SMA's emission ratio of NOx/SOx increased in 2015 by over 22% from 2013. Despite the reduction in domestic emissions, the concentration-to-emission ratios (NO2/NOx, SO2/SOx) rose gradually, which implies that other factors besides domestic emissions (e.g., foreign sources, lifetime, etc.) influence air quality in SMA. We estimated future emissions of NOx and SOx in SMA to be 296.2 and 39.0 ktons in 2025 and 284.4 and 33.8 ktons in 2035, respectively. Application of the inter-comparison techniques of this study to the data from the Geostationary Environment Monitoring Instrument (GEMS) is expected to provide concrete information which can be used to improve national emission inventories and figure out factors and sources that affect domestic air quality.

Air Pollutant Removal Rates of Concrete Permeable Blocks Produced with Coated Zeolite Beads (코팅된 제올라이트 비드를 이용한 콘크리트 투수블록의 대기전구물질 제거율 평가)

  • Park, Jun-Seo;Yang, Keun-Hyeok
    • Journal of the Korea Institute of Building Construction
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    • v.23 no.2
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    • pp.153-164
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    • 2023
  • The objective of this study is to examine the removal rate of air pollutants, specifically sulfur oxides (SOx) and nitrogen oxides(NOx), using concrete permeable blocks containing zeolite beads coated with materials capable of eliminating these pollutants. Titanium dioxide(TiO2) powder and coconut shell powder were utilized for the removal of SOx and NOx and were applied as coatings on the zeolite beads. Concrete permeable block specimens embedded with the coated zeolite beads were produced using an actual factory production line. Test results demonstrated that the concrete permeable block containing zeolite beads coated with coconut shell powder in the surface layer achieved SOx and NOx removal rates of 12.5% and 99%, respectively, exhibiting superior performance compared to other blocks. Additionally, the flexural strength and slip resistance were 5.3MPa and 65BPN or higher, respectively, satisfying the requirements specified in KS F 4419 and KS F 4561. Conversely, the permeability coefficient exhibited low permeability, with grades 2 and 3 before and after contaminant pollution, according to the standard for 'design, construction, and maintenance of pavement using permeable block'. In conclusion, incorporating zeolite beads coated with coconut shell powder in the surface layer enables simultaneous removal of SOx and NOx, irrespective of ultraviolet rays, while maintaining adequate flexural strength and slip resistance. However, the permeability is significantly reduced, necessitating further improvements.