• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1247-1254
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• 2000

The effects of recirculated exhaust gas on the characteristics of $NO_x$ and soot emissions under a wide range of engine load have been experimentally investigated by a water-cooled, four-cylinder, indirect injection, four cycle and marine diesel engine operating at two kinds of engine speeds. The simultaneous control of $NO_x$ and soot emissions in diesel engines is targeted in this study. The EGR system is used to reduce $NO_x$ emissions, and a novel diesel soot removal device with a cylinder-type scrubber for the experiment system which has 6 water injectors(A water injector has 144 nozzles in 1.0 mm diameter) is specially designed and manufactured to reduce the soot contents in the recirculated exhaust gas to intake system of the engines. The intake oxygen concentration and the mean equivalence ratio calculated by the intake air flow and fuel consumption rate, and the exhaust oxygen concentration measured are used to analyse and discuss the influences of EGR rate on $NO_x$ and soot emissions. The experiments are performed at the fixed fuel injection timing of $15.3^{\circ}$ BTDC regardless of experimental conditions. It is found that $NO_x$ emissions are decreased and soot emissions are increased owing to the drop of intake oxygen concentration and exhaust oxygen concentration, and the rise of equivalence ratio as the EGR rate rises.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.69-76
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• 1997

Industrial-scale pulse corona process to remove $SO_2$ and $NO_x$ simultaneously from combustion flue gas has been studied. The pilot plant built in the present study treats 2,000 $Nm^3$/hr of flue gas from a boiler. The geometry of the pulse corona reactor is similar to that of an electrostatic precipitator commonly used in industry, A thyratron switch and magnetic pulse compressors, which can generate up to 130 kV of peak pulse voltage and up to 30 kW of average pulse power, have been used to produce pulsed corona. The removal efficiencies of $S0_2$ and $NO_x$ with the present process are maximum of 95 % and 85 %, respectively. Electrical power consumption to produce the pulsed corona, which has been one of the major difficulties to apply this process to industry, has been evaluated in the present study. The results showed that the power consumption can be reduced significantly by simultaneous addition of hydrocarbon injection and heterogeneous phase reactions to the process.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.363-369
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• 2001

Process design and performance evaluation were made for medium-size gasification combined/cogeneration plant. Based on the designed plant process configuration, the effects of $NO_x$ reduction techniques on the $NO_x$ emission, the power output, the efficiency and the stability of plant are investigated by applying various $NO_x$ reduction methods such as unsaturated/saturated nitrogen injection and fuel saturation of gas turbine combustor. The $NO_x$ reduction by nitrogen injection is more remarkable than that by fuel saturation, and its effect can be more enhanced by using saturated nitrogen. In addition, the applications of $NO_x$ reduction techniques accompany the improvement of plant power output and efficiency with the decrease of $NO_x$ emission, while it can cause unstable gas turbine operation.

• Analytical Science and Technology
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• v.15 no.5
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• pp.427-432
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• 2002

The combustion behavior of heavy oil and its emulsion with water was evaluated. The concentration of $SO_x$ in the combustion gas of emulsion oil was reduced to 57% with respect to that of the combustion gas from neat heavy oil. Also, the concentration of $NO_x$ in the combustion gas of emulsion oil was reduced to 67% with respect to that of the combustion gas of neat heavy oil. These reductions of $SO_x$ in the combustion gas of emulsion oil seems to be due to the reaction with salts included in surfactant of emulsion oil. Also, the combustion efficiency of emulsion oil is evaluated to be about 6% higher than that of neat heavy oil.

• Journal of Sensor Science and Technology
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• v.18 no.6
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• pp.456-461
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• 2009

Perovskite-structure $Sr(Ti_{1-x}Fe_x)O_3$ thick films, in which x is 0.4 or 0.6, were prepared by normal ceramic process on alumina substrate. Electrical resistance was measured as a function of thermal treatment condition including atmosphere, time, and temperature. The resistance of $Sr(Ti_{1-x}Fe_x)O_3$ films is lower than those of $SrTiO_3$ or $SrFeO_3$ films. The temperature coefficient of resistance over $550^{\circ}C$ was measured to be 0 for the $Sr(Ti_{1-x}Fe_x)O_3$ films after thermal treatment at $1100^{\circ}C$ in air. The sensing property of the films was also measured as a function of temperature and gas such as $O_2$, CO, $CO_2$, NO and $NO_2$. $Sr(Ti_{1-x}Fe_x)O_3$ films showed a good sensing property for $O_2$, but no sensing signal for CO, $CO_2$, NO and $NO_2$.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.8-12
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• 1999

$\textrm{WO}_3$ semiconductive film, which is known to have a sensitivity on $\textrm{NO}_X$ gas was prepared on 8YSZ (8% Yttria stabilized $\textrm{ZrO}_2$) ionic conductor substrate that has oxygen ion pumping effect. Microstructure and electrical properity, especially $\textrm{NO}_X$ sensitivity as a function of DC voltage applied to 8YSZ substrate was examined. When the $\textrm{WO}_3$ film was annealed, it showed amorphous structure, while crystallization was occurred at $600^{\circ}$C revealing orthorhombic phase of $\textrm{WO}_3$. As the annealing temperature increases, (111) and (001) peaks of $\textrm{WO}_3$ film was enhanced. At $400^{\circ}C$ when DC voltage was applied, comparing with no DC bias, more stable and large response characteristics was showed, and the best sensitivity was observed at 2V. Recovery characteristics of NO gas was much better that that of $\textrm{NO}_2$ gas.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1322-1326
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• 1999

In2O3 thick film gas sensor for detecting NOx gas of high concentration was fabricated by a screen printing technique. This work focussed on investigation of the change of sensitivity to NOx gas with firing temperatures of sensing layer and on improvement of the sensitivity by adding catalysts such as Al,. Ru, and SnO2 The cross sensitivites of sensor to CO, H2, CH4 and i-C4H10 gases were also examined under NO2 gas concentration of 200ppm Pure In2O3 gas sensor prepared at a firing temperature of 50$0^{\circ}C$ showed a maximum sensitivity to NOx gas at the operating temperature of 40$0^{\circ}C$ Al(0.004 wt%)-In2O3 sensor largely improved the sensitivities to both NO2 and NO gas and showed a superior selectivity compared with other gas sensors.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.601-604
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• 1998

NOX detecting gas sensors using TiO2 doped tungsten oxide semiconductor were prepared and their electrical and sensing characteristics have been investigated. In normal air condition, the sensors of WO3, TiO2 doped WO3 show grain boundary heights of 0.34 eV, 0.25 eV, respectively. The grain boundary barrier energy variation was increased by doping TiO2 into large variation of resistance to NOX gases. And doping the TiO2 4 wt.%, the particle size of WO3 polycrystal films showed higher sensitivity and better sorption characteristics to NOX gas than the pure WO3 films material in air at operating temperature of $350^{\circ}C.$ The TiO2 doped WO3 semiconductor gas sensor shows nano-sized particle size and good sensitivity to sub-ppm concentration of NOX.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.455-460
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• 2022

Brush-like ZnO hierarchical nanostructures decorated with MgxZn1-xO (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were fabricated and examined for application to a gas sensor. They were synthesized using vapor phase growth (VPG) on indium tin oxide (ITO) substrates. To generate electronic accumulation at ZnO surface, MgZnO nanoparticles were prepared by sol-gel method, and the ratio of Mg and Zn was adjusted to optimize the device for NO₂ gas detection. As the electrons in the accumulation layer generated by the heterojunction reacted faster and more frequently with the gas, the sensitivity and speed improved. When tested as sensing materials for gas sensors at 100 ppm NO₂ at 300℃, these MgZnO decorated ZnO nanostructures exhibited an improvement from 165 to 514 times compared to pristine ZnO. The response and recovery time of the MgZnO decorated ZnO samples were shorter than those of the pristine ZnO. Various analyzing techniques, including field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD) were employed to confirm the growth morphology, atomic composition, and crystalline information of the samples, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.203-206
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• 2000

In this experiment, an attempt to use pellets($BaTiO_3$, $TiO_2$, ${\gamma}-Al_2O_3$, sludge) for $NO_x$ removal was conducted The effect of pellets on NO removal from simulated flue gas was experimentally investigated for packed-bed reactor of plate-plate geometry. An experimental investigation has been conducted for NO concentration of 50ppm balanced by air, and gas flow rate of $5{\ell}/min$. Ceramic pellets were used for surface discharge and the sludge pellets was added on $BaTiO_3$ and $TiO_2$ to increase $NO_x$ removal rate. In the result, $NO_x$ removal rate using $TiO_2$ was better than other pellets. $NO_2$ segnificatly generated by using $BaTiO_3$ pellets and sludge pellets used with $BaTiO_3$ decreased $NO_2$ generation.