• Title/Summary/Keyword: Ambient gas

Search Result 735, Processing Time 0.025 seconds

Electrochemical Nitrogen Reduction Reaction to Ammonia Production at Ambient Condition (상온 상압 조건에서 전기화학적 질소환원반응을 통한 암모니아 생산 연구 동향)

  • Lee, Dong-Kyu;Sim, Uk
    • Journal of the Korean Electrochemical Society
    • /
    • v.22 no.1
    • /
    • pp.1-12
    • /
    • 2019
  • The reduction of nitrogen to produce ammonia has been attracting much attention as a renewable energy technology. Ammonia is the basis for many fertilizers and is also considered an energy carrier that can power internal combustion engines, diesel engines, gas turbines, and fuel cells. Traditionally, ammonia has been produced through the Haber-Bosch process, in which atmospheric nitrogen combines with hydrogen at high temperature ($350-550^{\circ}C$) and high pressure (150-300 bar). This process consumes 1-2% of current global energy production and relies on fossil fuels as an energy source. Reducing the energy input required for this process will reduce $CO_2$ emissions and the corresponding environmental impact. For this reason, developing electrochemical ammonia-production methods under ambient temperature and pressure conditions should significantly reduce the energy input required to produce ammonia. In this review, we introduce the electrochemical nitrogen reduction reaction at ambient condition. Numerical studies on the electrochemical nitrogen reduction mechanism have been carried out through the computation of density function theory. Electrodes such as nanowires and porous electrodes have been also actively studied for further participation in electrochemical reactions.

Atmospheric Distribution of PCDD/F Concentrations in Gyeonggi-do, South Korea (경기도 내 대기 중 다이옥신 분포 특성에 관한 연구)

  • Heo, Jong-Won;Min, Yoon-Ki;Kim, Dong-Gi;Choi, Il-Woo;Kim, Jong-Soo;Song, Il-Seok;Lee, Gangwoong
    • Journal of Korean Society for Atmospheric Environment
    • /
    • v.31 no.6
    • /
    • pp.548-561
    • /
    • 2015
  • Atmospheric concentrations of polychlorinated dibezo-p-dioxins and furans (PCDD/Fs) were investigated at urban-residential (Group I: Suwon, Guri and Goyang), industrial (Group II: Ansan, Siheung and Bucheon), urban-rural mixed (Group III: Yangju, Pocheon and Dongducheon) and rural regions (Group IV: Yangpyeong) in Gyeonggi-do from February 2012 to November 2012 quarterly. The concentrations of PCDD/Fs ranged from 0.018 to $0.109pgTEQm^{-3}$ in Group I (mean value: $0.061pgTEQm^{-3}$), 0.059 to $0.367pgTEQm^{-3}$ in Group II (mean value: $0.179pgTEQm^{-3}$), 0.072 to $0.836pgTEQm^{-3}$ in Group III (mean value: $0.334pgTEQm^{-3}$) and 0.014 to $0.066pgTEQm^{-3}$ in Group IV (mean value: $0.034pgTEQm^{-3}$), respectively. In spite of the less PCDD/F emission sources than Group II (industrial regions), the level of PCDD/Fs in urban-rural mixed area showed the highest values with high fluctuation. It's likely that the Group III was affected by fugitive emissions such like biomass burning and unregulated open burning. The mean contribution of particle phase to total PCDD/F concentration was above 83% because most of PCDD/F congeners were partitioned into particle phase. We evaluated their gas-to-particles equilibriums with the regression between the particle-gas partition coefficient, $K_P(m^3{\mu}g^{-1})$ and corresponding subcooled liquid vapor pressure ($P_L$). The logarithm-$K_P$ of PCDD/Fs was poorly correlated with $P_L$ at low ambient temperature (below $10^{\circ}C$) and the slope (m) values for log-log plots of the $K_P$ vs. $P_L$ was steeper in the Group 2 and Group 3 than residential area. It implies that the slope values were likely influenced by both the direct emission source of PCDD/Fs and ambient temperature.

Design for Landfill Gas Application by Low Calorific Gas Turbine and Green House Optimization Technology (Low Calorific Gasturbine 매립지 적용 및 유리온실 운용기술 설계)

  • Hur, Kwang-Beom;Park, Jung-Keuk;Lee, Jung-Bin;Rhim, Sang-Gyu
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2010.06a
    • /
    • pp.244.1-244.1
    • /
    • 2010
  • Bio energy development by using Low Calorific Gas Turbine(LCGT) has been developed for New & Renewable energy source for next generation power system, low fuel and operating cost method by using the renewable energy source in landfill gas (LFG), Food Waste, water waste and Livestock biogas. Low calorific fuel purification by pretreatment system and carbon dioxide fixation by green house system are very important design target for evaluate optimum applications for bio energy. Main problems and accidents of Low Calorific Gas Turbine system was derived from bio fuel condition such as hydro sulfide concentration, siloxane level, moisture concentration and so on. Even if the quality of the bio fuel is not better than natural gas, LCGT system has the various fuel range and environmental friendly power system. The mechanical characterisitics of LCGT system is a high total efficiency (>70%), wide range of output power (30kW - 30MW class) and very clean emmission from power system (low NOx). Also, we can use co-generation system. A green house designed for four different carbon dioxide concentration from ambient air to 2000 ppm by utilizing the exhaust gas and hot water from LCGT system. We look forward to contribute the policy for Renewable Portfolio Standards(RPS) by using LCGT power system.

  • PDF

Performance Predictions of Gas Foil Journal Bearings with Turbulent Flows (난류 유동을 갖는 가스 포일 저널 베어링의 성능 예측)

  • Mun, Jin Hyeok;Kim, Tae Ho
    • Tribology and Lubricants
    • /
    • v.35 no.3
    • /
    • pp.190-198
    • /
    • 2019
  • Gas foil bearings (GFBs) enable small- to medium-sized turbomachinery to operate at ultra-high speeds in a compact design by using ambient air or process gas as a lubricant. When using air or process gas, which have lower viscosity than lubricant oil, the turbomachinery has the advantage of reduced power loss from bearing friction drag. However, GFBs may have high Reynolds number, which causes turbulent flows due to process gas with low viscosity and high density. This paper analyzes gas foil journal bearings (GFJBs) with high Reynolds numbers and studies the effects of turbulent flows on the static and dynamic performance of bearings. For comparison purposes, air and R-134a gas lubricants are applied to the GFJBs. For the air lubricant, turbulence is dominant only at rotor speeds higher than 200 krpm. At those speeds, the journal eccentricity decreases, but the film thickness, power loss, and direct stiffness and damping coefficients increase. On the other hand, the R-134a gas lubricant, which that has much higher density than air, causes dominant turbulence at rotor speeds greater than 10 krpm. The turbulent flow model predicts decreased journal eccentricity but increased film thickness and power loss when compared with the lamina flow model predictions. The vertical direct stiffness and damping coefficients are lower at speeds below 100 krpm, but higher beyond that speeds for the turbulent model. The present results indicate that turbulent flow effects should be considered for accurate performance predictions of GFJBs with high Reynolds number.

An Experimental Study on the Self-excited Instabilities in Model Gas Turbine Combustor (모델 가스터빈 연소기내의 자발 불안정성에 관한 실험적 연구)

  • Lee, Min-Chul;Hong, Jung-Goo;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
    • /
    • 2004.11a
    • /
    • pp.197-205
    • /
    • 2004
  • Most of gas turbines is operated by the type of dry premixed combustion to reduce NOx emission and economize fuel consumption. However this type operation, combustion induced instability brought failure problems cause by high pressure and heat release fluctuations. Though there has been lots of studies since Lord Rayleigh to understand this instability mechanism and control the instabilities, none of them made matters clear. In order to understand the instability phenomena, a simple experimental study with dump combustor was conducted at the moderate pressure and ambient temperature conditions. From this model gas turbine combustor self-excited instabilities at the resonance mode(200Hz) and bulk mode(10Hz) were occurred and observed at the three points of view; pressure, heat release and equivalence ratio which are acquired by peizo-electric transducer, HICCD camera and acetone LIF respectively. From this results we could see the instability mechanism clear with the account of time scale analysis which explained by the propagation of pressure wave to the upward of mixture stream and convectional transfer of the equivalence ratio fluctuation by this pressure fluctuation.

  • PDF

A Study of Nitrous Oxide Thermal Decomposition and Reaction Rate in High Temperature Inert Gas (고온 불활성 기체 분위기에서 아산화질소 열분해 및 반응속도에 관한 연구)

  • Lee, Han Min;Yun, Jae Geun;Hong, Jung Goo
    • Journal of ILASS-Korea
    • /
    • v.25 no.3
    • /
    • pp.132-138
    • /
    • 2020
  • N2O is hazardous atmosphere pollution matter which can damage the ozone layer and cause green house effect. There are many other nitrogen oxide emission control but N2O has no its particular method. Preventing further environmental pollution and global warming, it is essential to control N2O emission from industrial machines. In this study, the thermal decomposition experiment of N2O gas mixture is conducted by using cylindrical reactor to figure out N2O reduction and NO formation. And CHEMKIN calculation is conducted to figure out reaction rate and mechanism. Residence time of the N2O gas in the reactor is set as experimental variable to imitate real SNCR system. As a result, most of the nitrogen components are converted into N2. Reaction rate of the N2O gas decreases with N2O emitted concentration. At 800℃ and 900℃, N2O reduction variance and NO concentration are increased with residence time and temperature. However, at 1000℃, N2O reduction variance and NO concentration are deceased in 40s due to forward reaction rate diminished and reverse reaction rate appeared.

Analysis of Emission Gas Characteristics for Gasoline Vehicles using the Inspection Results of Car Emission (운행차 배출가스 정밀검사 결과를 이용한 가솔린 차량에 대한 배출가스 특성 분석)

  • Roh, Hyun Gu
    • Journal of ILASS-Korea
    • /
    • v.23 no.3
    • /
    • pp.128-135
    • /
    • 2018
  • In this study, the following conclusions could be obtained from the analysis of emissions contribution rates and features for contaminated emissions by 13,456 gasoline vehicles passed in the vehicle load test (ASM-idle) under the inspection year 2013 to 2017. It was confirmed that the contamination of the CO, HC, NOx by the displacement is reduced on over 3L engine. As a result of comparing the exhaust gas in the low speed idle mode and the AS2525 mode, the exhaust gas in the low speed idle mode was measured high. It is estimated that if ISG function is applied, emissions from idle condition will be reduced. NOx emissions were reduced when the engine power was above 200HP. It has been confirmed that the amount of exhaust emissions are significantly reduced for vehicles manufactured after 2004. As a result of analyzing the exhaust gas according to the season, it is judged that there is a correlation between HC and NOx according to the ambient temperature. The concentration of exhaust emission in vehicles with high accumulated distance increases, which is considered to be the result of aging of the vehicle.

Effect of Flue Gas Heat Recovery on Plume Formation and Dispersion

  • Wu, Shi Chang;Jo, Young Min;Park, Young Koo
    • Particle and aerosol research
    • /
    • v.8 no.4
    • /
    • pp.161-172
    • /
    • 2012
  • Three-dimensional numerical simulation using a computational fluid dynamics (CFD) was carried out in order to investigate the formation and dispersion of the plume discharged from the stack of a thermal power station. The simulation was based on the standard ${\kappa}{\sim}{\varepsilon}$ turbulence model and a finite-volume method. Warm and moist exhaust from a power plant stack forms a visible plume as entering the cold ambient air. In the simulation, moisture content, emission velocity and temperature of the flue gas, air temperature and wind speed were dealt with the main parameters to analyze the properties of the plume composed mainly of water vapor. As a result of the simulation, the plume could be more apparent in cold winter due to a big difference of latent heat capacity. At no wind condition, the white plume rises 120 m upward from the top of the stack, and expands to 40 m around from the stack in cold winter after flue gas heat recovery. The influencing distance of relative humidity will be about 100 m to 400 m downstream from the stack with a cross wind effect. The decrease of flue gas temperature by heat recovery of thermal energy facilitates the formation of the plume and restrains its dispersion. Wind speed with vertical distribution affects the plume dispersion as well as the density.

100 MWe Oxyfuel Power Plant Boiler System Process Design and Operation Parameters Sensitivity Analysis (100 MWe급 순산소연소 발전소 보일러계통 공정설계 및 운전변수 민감도 예측)

  • Baek, Sehyun;Ko, SungHo
    • Journal of the Korean Society of Combustion
    • /
    • v.18 no.4
    • /
    • pp.1-11
    • /
    • 2013
  • The oxy-fuel combustion is $CO_2$ capture technology that uses mixture of pure $O_2$ and recirculated exhaust as oxidizer. Currently some Oxy-fuel power plants demonstration project is underway in worldwide. Meanwhile research project for converting 125 MWe Young-Dong power plant to 100 MWe oxy-fuel power plants is progress. In this paper, 1 D process analytical approach was applied for conducting process design and operating parameters sensitivity analysis for oxy-fuel combustion of Young-Dong power plant. As a result, appropriate gas recirculation rates was 74.3% that in order to maintain normal rating superheater, reheater steam temperature and boiler heat transfer patterns. And boiler efficiency 85.0%, CPU inlet $CO_2$ mole concentration 71.34% was predicted for retrofitted boiler. The oxygen concentration in the secondary recycle gas is predicted as 27.1%. Meanwhile the oxygen concentration 22.4% and moisture concentration 5.3% predicted for primary recycle gas. As the primary and secondary gas recirculation increases, then heat absorption of the reheater is tends to increases whereas superheater side is decreased, and also the efficiency is tends to decrease, according to results of sensitivity analysis for operating parameters. In addition, the ambient air ingression have a tendency to lead to decline of efficiency for boiler as well as decline of $CO_2$ purity of CPU inlet.

Prediction of Heat Transfer Rates to Spray Water Droplets in a High Pressure Mixture Composed of Saturated Steam and Noncondensable Hydrogen Gas (고압의 포화수증기-비응축성 수소기체 혼합기 속에서 분무수적으로의 열전달을 예측)

  • Lee, S.K.;Jo, J.C.;Cho, J.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.3 no.5
    • /
    • pp.337-349
    • /
    • 1991
  • Heat and mass transfer rates to spray water droplets for spray transients in a high pressure vessel have been predicted by two different droplet models: the complete mixing model and the non-mixing model. In this process, the ambient fluid surrounding the droplets is a real-gas mixture composed of saturated steam and noncondensable hydrogen gas at high pressure. The physical properties of the mixture are estimated by applying the concept of compressibility factor and using appropriate correlations. A computer program, DROPHMT, to calculate the heat and mass transfer rates for two different droplet models has been developed. As an illustrative application of the computer program to engineering practices, heat and mass transfer rates to spray water droplets for spray transients in a Pressurized Water Reactor (PWR) pressurizer have been calculated, and the typical results have been provided.

  • PDF