• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.11
• /
• pp.5610-5614
• /
• 2012

Performance of catalyst was studied with various operating conditions for selective catalytic reduction of $NO_x$ with $NH_3$. It is confirmed that catalysts containing Mn and Cu have a good efficiency in the usage of oxygen by the $H_2$-TPR analysis. In the case of catalyst #1, $NO_x$ conversion was decrease with the increase of reaction temperature. But in the case of catalyst #2, $NO_x$ conversion was increased and then remained constant with the increase of reaction temperature. This phenomenon is due to the difference of the $NH_3$ oxidation of both catalysts.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.608-613
• /
• 2019

NOx (Nitrogen oxide) in the exhaust gas from vehicle engines is considered one of the most harmful substances in air pollution problems. NOx is made when combustion occurs under high temperature conditions and EGR (exhaust gas recirculation) is normally used to lower the combustion temperature. As the EGR ratio increases, the NOx level becomes low, but a high EGR ratio makes the combustion unstable and causes further air pollution problems, such as CO and unburned hydrocarbon level increase. This study showed that fuel droplets could move more freely by the radiation of sonic wave for the stable combustion. In addition, the engine performance improved with increasing EGR ratio. As a basic study, the effect of sonic wave radiation on the velocity of fuel droplets was studied using CFD software. The results showed that the velocity of small droplets increased more under high frequency sonic wave conditions and the velocity of the large droplets increased at low frequency sonic wave conditions. In addition, an engine analysis model was used to study the effects of the increased combustion stability. These results showed that a 15% increase in EGR ratio in combustion resulted in a 45% decrease in NOx and a 10% increase in thermal efficiency.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.6
• /
• pp.645-653
• /
• 2005

The effects of a WI(Water Injection) at the intake Pipe and an urea injection at the exhaust pipe for a 4-cylinder DI(Direct Injection) diesel engine were investigated experimentally The water quantity was controlled by temperature of intake manifold and MAF(Manifold Air Flow). In addition, the urea quantify was controlled by NOx quantify and MAF. Effects of WI system, urea-SCR system and tandem system were investigated for with and without EGR(Exhaust Gas Recirculation). As the results. the SUF(Stoichiometric Urea Flow) and NOx map were obtained. In addition, NOx results can be visualized with engine speed and engine load. It was concluded. therefore, that the NOx reduction effects of the tandem system without the EGR were more than those with the EGR base engine.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.8
• /
• pp.8-13
• /
• 2018

Nitrogen oxides (NOx) have recently been very influential in the generation of ultrafine dust, which is of great social interest in terms of improving the atmospheric environment. Nitrogen oxides are generated mainly by the reaction of nitrogen and oxygen in air in a combustion gas atmosphere of high temperature in a combustion apparatus such as thermal power generation. Recently, research has been conducted on the combustion that recirculates the exhaust gas to the cylindrical burner by using a piping using a Coanda nozzle. In this study, three types of burners were carried out through computational fluid analysis. Case 1 burner with the outlet of the combustion gas to the right, Case 2 burner with both sides as gas exit, Case 3 burner with left side gas exit. The pressure, flow, temperature, combustion reaction rate and distribution characteristics of nitrogen oxides were compared and analyzed. The combustion reaction occurred in Case 1 and Case 2 burner in the right direction with combustion gas recirculation inlet and Case 3 burner in the vicinity of mixed gas inlet. The temperature at the outlet was about $100^{\circ}C$ lower than that of the other burners as the Case 2 burner was exhausted to both sides. The NOx concentration of Case 1 burner at the exit was about 20 times larger than that of the other burners. From the present study, it could be seen that it is effective for the NOx reduction to exhaust the exhaust gas to both side gas exits or to exhaust the exhaust gas to the opposite direction of inlet of recirculation gas.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.6
• /
• pp.167-175
• /
• 2018

Natural gas is a clean fuel that discharges almost no air-contaminating substances. This study examined the simultaneous reduction of $CH_4$ and NOx of NGOC/LNT catalysts for CNG buses related to the improvement of the $de-CH_4/NOx$ performance, focusing mainly on identifying the additive catalysts, loading of the washcoat, stirring time, and types of substrates. The 3wt. % Ni-loaded NGOC generally exhibited superior $CH_4$ reduction performance through $CH_4$ conversion, because Ni is an alkaline, toxic oxide, and exerts a reducing effect on $CH_4$. A excessively small loading resulted in insufficient adsorption capacity of harmful gases, whereasa too high loading of washcoat caused clogging of the substrate cells. In addition, with the economic feasibility of catalysts considered, the appropriate amount of catalyst washcoat loading was estimated to be 124g/L. The NOx conversion rate of the NGOC/LNT catalysts stirred from $200^{\circ}C$ to $550^{\circ}C$ for 5 hours showed 10-15% better performance than the NGOC/LNT catalysts mixed for 2 hours over the entire temperature range. The NGOC/LNT catalysts exhibitedapproximately 20% higher $de-CH_4$ performance on the ceramic substrates than on the metal substrates.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.4
• /
• pp.775-784
• /
• 2000

Nitrate dry deposition fluxes were directly measured using knife-leading-edge surrogate surface (KSS) covered with greased strips and a water surface sampler (WSS). The average gaseous flux ($8.3mg/m^2/day$) was much higher than the average particulate one ($3.0mg/m^2/day$). The best fit gas phase mass transfer coefficient (MTC) of $HNO_3$ was obtained by linear regression analysis between measured gaseous flux containing nitrogen compounds and measured ambient $HNO_3$ concentration. The result showed that the MTCs of $HNO_3$ were approximately two times higher than those of $SO_2$. Especially, during the ozone action day, measured gaseous fluxes containing nitrogen compounds were much higher than those ones calculated as the product of measured ambient $HNO_3$ concentration and gas phase MTC of $HNO_3$, which is calculated from MTC of $SO_2$ using Graham's diffusion law. This result indicated that other nitrogen compounds except $HNO_3$ contributed to gaseous flux containing nitrogen compounds into the water surface sampler. The theoretical calculations suggest the contributions of nitrous acid ($HNO_2$) and PAN to the gaseous dry deposition flux of nitrogen containing compounds to the WSS.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.4
• /
• pp.1923-1930
• /
• 2012

Mn-Cu catalysts were tested for selective catalytic reduction of NOx with NH3. Influence of initial reaction temperature was studied for NOx conversion in which reaction temperature was changed three patterns. NOx conversion of catalysts calcined at 200, 300 and $340^{\circ}C$ was measured during the changing temperature. Hydrogen conversion efficiency of calcined catalysts was also measured in the $H_2$-TPR system. The deactivation effect of $SO_2$ on catalyst was investigated with the on-off control of $SO_2$ supply. The catalyst which calcined above $340^{\circ}C$ was somewhat deactivated with thermal shock. The reason of deactivation was draw from the results of surface area and hydrogen conversion.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.9
• /
• pp.4250-4256
• /
• 2011

Mn catalyst promoted with Cu were prepared and tested for selective catalytic reduction of $NO_x$ with $NH_3$. Performance of each catalyst was investigated for $NO_x$ activity while changing temperature, space velocity, water content and $O_2$ concentration. Hydrogen conversion efficiency of catalyst was also measured in the $H_2$-TPR system. The inhibition effect of water on catalyst was investigated with the on-off control of water supply. High activity of Mn-Cu catalyst was observed for $160{\sim}260^{\circ}C$. It is found that increase of oxygen concentration acts as a promotor to the increase of catalyst activity but water content acts as a inhibitor.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.9
• /
• pp.407-411
• /
• 2003

The purpose of this paper is to study the removal of nitrogen oxide(NOx) using a wire-plate type plasma reactor with magnet attached for indoor air purification. In order to produce a more effective reactor, we conducted magnetic field simulations. The results of the magnetic field simulations show that NOx can be removed more effectively. The results from the magnetic field simulation show that when 7 magnets were applied to the reactor, the magnetic flux density was at its highest amount than when using 0, 3, or 5 magnets. From the data obtained by the simulation results a plasma reactor was made and thus, several experiments were conducted. The best removal efficiency was obtained with 14 W AC power to the reactor with 5 magnets.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2000.11a
• /
• pp.441-442
• /
• 2000

오존은 질소산화물, 일산화탄소 및 휘발성 유기화학물질 등의 광화학반응에 의해 생성되는 2차 오염물질이다(Haagen-Smit and Fox, 1953). 오존은 낮은 농도에서도 인체 및 식물에게 영향을 미치는 것으로 알려져 있다. 우리나라에서도 오존의 대기환경기준을 8시간 평균 0.06ppm, 1시간 평균 0.10ppm으로 낮추고, 오존예보제ㆍ경보제 등을 운영하여 오존에 의한 영향을 줄이고자 노력하고 있다. 그러나 서울과 같은 도시 밀집지역은 자동차의 밀집과 대형건축물의 증가, 기류 정체로 오염물질의 확산이 어렵고 도심지 내 열섬(heat island)현상으로 대기온도가 증가하여 오존생성에 유리한 조건을 형성함으로 인해 연평균 오염도가 1990년 이후 꾸준히 증가하고 있는 추세이다. (중략)