• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.111-118
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• 2009

A hybrid SNCR/SCR plant was designed and manufactured, and experimented on the SNCR process in the first step to investigate the optimum operation conditions of SNCR, with the equivalence ratio of the reducing agent(NSR, 0.5~5.0), reaction temperature($850{\sim}1,100^{\circ}C$), nozzle type(wall nozzle, pipe nozzle), and nozzle position as variables. In the case of wall nozzles, the NOx reduction efficiency rapidly increased to 87% at 2.5 NSR and slowed down after this. Compared to the upward spray from the pipe nozzle, wall nozzles have narrower range of applicable reaction temperature. In the case of pipe nozzles, it rapidly increased to 77% at 1.5 NSR. But the pipe nozzle downward had no NOx reduction efficiency; on the contrary, NOx increased. When the reducing agent was sprayed upward from a pipe nozzle, the NOx reduction efficiency was 50~75% in the range of 0.5~1.5 NSR, and the NOx reduction efficiency was constant without fluctuations even in the change of reaction temperature from 890 to $1,000^{\circ}C$. When 5% urea solution was sprayed upward from the pipe nozzle, 200 ppm NOx decreased to approximately 60 ppm at 1.2 NSR, and the non-reacted $NH_3$ was 50~100 ppm. In this condition, we expect over 90% NOx reduction efficiency without additional supply of $NH_3$ to SCR at the back of SNCR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.503-510
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• 2016

Incinerators generally emit pollutants such as NOx and CO during the combustion process. In this paper, pollutant emissions and temperature distributions were studied in a simulated incinerator with a reversed (relative to the flue gas flow) secondary air injection system. The experiments were performed by using a lab-scale furnace in order to evaluate the effects of the injection location, direction and flow rate of secondary air jets. The emission of NOx was lower in the case of reversed secondary air injection than in the case of cross injection, due to the recirculation and mixing of the exhaust gas. In the reversed air injection cases, thermal NOx emissions decreased as secondary air ratio increased from 30 to 60 and slightly increased at secondary air ratios higher than 60. In most cases, CO emissions were not detected except for a few reversed secondary air injection cases, in which cases CO concentrations below 2ppm were observed.

• 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 $250^{\circ}C$.

• The Plant Pathology Journal
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• v.38 no.4
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• pp.345-354
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• 2022

NADPH oxidase (Nox) complexes are known to play essential roles in differentiation and proliferation of many filamentous fungi. However, the functions of Noxs have not been elucidated in Colletotrichum species. Therefore, we set out to characterize the roles of Nox enzymes and their regulators in Colletotrichum scovillei, which causes serious anthracnose disease on pepper fruits in temperate and subtropical and temperate region. In this study, we generated targeted deletion mutants for CsNox1, CsNox2, CsNoxR, and CsNoxD via homologous recombination. All deletion mutants were normal in mycelial growth, conidiation, conidial germination, and appressorium formation, suggesting that CsNox1, CsNox2, CsNoxR, and CsNoxD are not involved in those developmental processes. Notably, conidia of 𝜟Csnox2 and 𝜟Csnoxr, other than 𝜟Csnox1 and 𝜟Csnoxd, failed to cause anthracnose on intact pepper fruits. However, they still caused normal disease on wounded pepper fruits, suggesting that Csnox2 and CsnoxR are essential for penetration-related morphogenesis in C. scovillei. Further observation proved that 𝜟Csnox2 and 𝜟Csnoxr were unable to form penetration peg, while they fully developed appressoria, revealing that defect of anthracnose development by 𝜟Csnox2 and 𝜟Csnoxr resulted from failure in penetration peg formation. Our results suggest that CsNox2 and CsNoxR are critical for appressorium-mediated penetration in C. scovillei-pepper fruit pathosystem, which provides insight into understanding roles of Nox genes in anthracnose disease development.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.117-124
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• 2011

Automotive engines require strategies to fulfill the emission regulations in terms of NOx and PM. A dramatic reduction in NOx and PM emissions could be achieved with high pressure injection, innovative combustion strategies and EGR. Recently, Lean NOx Trap (LNT) and Urea-SCR are considered as more practical strategy to suppress the engine-out emissions substantially for copying with severe regulation. These systems need to reduce the reducing agent injection system which has a huge impact on NOx purification efficiency. In this paper, different three injectors have been used to investigate spray characteristics and engine emission test was conducted to clarify the effect of these injectors on the NOx reduction.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.183-190
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• 2002

In order to reduce NOx emissions in the 20kw class microturbines under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and pressure. Air from a compressor with the temperature of 500K to 650K and the pressure of 0.3bar gauge to 0.7bar gauge, was supplied to the combustor through an air preheat-treatment. Sampling exhaust gases were measured at the immediate exit of the combustor. for the effect of temperature on NO and CO emissions. though NOx was increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx and CO were increased also. NOx was decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratios of 0.10 to 0.25 in a lean region. NOx was increased with increasing equivalent ratios, but CO was decreased as an influence of flame temperature. In the very lean region of the equivalent ratio below 0.12, CO was increased suddenly, due to instability. As the results of this study, NOx and CO are found to be reduced to the similar level at the same time when operated at optimal conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.77-84
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• 2002

Measurements of NO and NOx emission of laminar partially premixed LPG/air flames with and without acoustic excitation are reported. The NOx emission at the tailpipe of a combustion chamber is determined by chemiluminescent analyser. The NOx measurements are taken in flames with several different center tube equivalance ratio( ø$\sub$o/), and overall equivalace ratio(ø$\sub$o/) for a fixed fuel flowrate. The NOx emission decrease to reach a minimum value at an optimum ø$\sub$c/ 2. Theø$\sub$c/ 2 flame gives a compromise of thermal NO and prompt NO mechanism. In the case of excitation. the visual shape of the flame is changed from laminar flame to turbulent-like flame. With increasing levels of excitation amplitude, an optimum value of the NO and NOx emission exists. A shorter flame caused by the enhanced upstream mixing due to acoustic excitation results in the reduction of NO and NOx emission in the present flames. The reduction of flame length affects the shorter residence time of center tube mixture, and significantly influences the NOx reduction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.833-841
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• 2002

The present study examined the possibility of NOx reduction in the high temperature industrial furnaces, duct burner of gas turbine cogeneration and two-stage gas turbine combustor. The experimental study was carried out for the non-premixed flame of second stage combustor with the variations of oxygen concentration in the hot exhaust gas of first stage combustor. It also examined the flammability range, temperature and NOx, $CO_2$, $O_2$formation in the combustor with respect to oxygen concentration in which the fuel(natural gas) is supplying into the hot exhaust gas. The results show that the inner temperature of flame reaches 1,20$0^{\circ}C$ at EGR $O_2$23% and that 15ppm of NOx at EGR $O_2$15.5% increases up to 60ppm at EGR $O_2$23%. It is believed that Fenimore＇s prompt NOx mechanism is more influential on the NOx formation than Zeldovich＇s thermal NOx mechanism does.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.952-960
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• 2009

Selective Catalytic Reduction (SCR) system is a high-effective NOx reduction technology in diesel engines. As the emission standard of diesel engines is more stringent, vehicle manufactures makes efforts on emission technologies. This paper discusses the performance of Urea-SCR system according to the engine operating conditions in a passenger diesel engine. Engine test results in this paper show that it is important to consider the catalyst temperature and space velocity to obtain high NOx conversion efficiency. In condition of high catalyst temperature, over 90% NOx conversion efficiency is indicated. However, when catalyst temperature is low, NOx conversion efficiency was decreased. Also, it was shown that space velocity mainly effects on the DeNOx performance under 220 degree celsius of SCR catalyst temperature. As the urea injection pressure was decreased, NOx conversion efficiency was declined. It is concerned about urea droplet atomization. This work shown in this paper can lead to improved overall NOx conversion efficiency.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.155-160
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• 2001

The low NOx characteristics have been investigated to develop the combustor for micro turbine. The lean premixed combustion technology was applied to reduce the NOx emission. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of $450\sim650K$ were supplied to the combustor through the air preheater. The temperature and emissions of NOx and CO were measured at the exit of combustor, The exit temperature and NOx were increased and CO was decreased with increasing inlet air temperature. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The NOx was decreased with decreasing the equivalence ratio. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.4. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The NOx was decreased and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.