• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.4
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• pp.387-394
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• 2011

A study on the removal of sulfur dioxide and nitrogen oxide was carried out using a non-thermal nano-pulse corona discharger at different gas temperatures. Pulse voltage with a high voltage of 50 kV, a pulse rising time of about 100 ns, a full width at half maximum of about 500 ns and a frequency of 1 kHz was applied to a wire-cylinder corona reactor. Ammonia and propylene gases were added into the corona reactor as additives with a static mixer. Ammonia addition had less effect on $SO_2$ reduction at the higher temperature because of the retardation of ammonium sulfate formation. However, propylene addition enhanced NO reduction at higher temperature due to increased gas mixture. $SO_2$ was further removed at the mixed $SO_2$ and NO gas due to increased $NO_2$ by the conversion of NO. The addition of ammonia and propylene gases was more highly dominant for the removal of sulfur dioxide compared to the sole pulse corona without the additives. However, the specific energy density per unit concentration of pulse corona as well as propylene additive was an important factor to remove NO gas. Therefore, the specific energy density per unit concentration of 0.04 Wh/($m^3{\cdot}ppm$) was necessary for the NO removal of more than 80% with the concentration ratio of 2.0 for propylene and NO. Hydrogen peroxide was another alternative additive to remove both $SO_2$ and NO in the nano-pulse corona discharger.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.1-7
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• 2023

Gas separation technology becomes more useful because key gases such as H₂ and CO₂ regarding renewable energy resources and environmental pollutant can be effectively extracted in mixed gases. For reducing energy consumption on gas separation, membrane and adsorption processes are widely used. In both processes, porous materials are needed as membrane and adsorbent. In particular, metal-organic frameworks (MOFs), one class of the porous materials, have been developed for the purpose of gas adsorption and separation. While the number of the MOF structures is increasing due to chemical and structural tunability, good MOF membranes and adsorbents have been rarely reported by trial-and-error experiments. To accelerate the discovery of high-performing porous materials that can separate H₂ and CO₂, a high-throughput computational screening technique was used as efficient skill. This review introduces crucial studies of porous materials and the high-throughput computational screening works focusing on gas separation of H₂ and CO₂.

• Journal of Animal Science and Technology
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• v.53 no.5
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• pp.475-480
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• 2011

This study was conducted to investigate the effects of different feeding level of TDN (Total Digestible Nutrients) on the generation of main greenhouse gases such as carbon dioxide and methane in Hanwoo cows. The diet TDN (kg) adjusted to achieve ADG of 0 g/day (Control), 200 g/day (T1), and 400 g/day (T2) of the maintenance level TMR (Total Mixed Ration) delivered twice a day at 08:30 and 17:30. Cow are housed in a respiration chamber and the environmental temperature was maintained at $20^{\circ}C$. The gases were measured for 24 hours using the multi-detector instrument Mamos-300. The analyzed methane emissions of T1 and T2 were 33.5% and 69.6% higher than control, respectively, and the carbon dioxide emissions were 21.1% and 40.6% higher than control. Also, the hourly pattern of carbon dioxide and methane production were showed very similar emission. Gas production showed peak after 1 hour of feeding and this gap was wider in the afternoon than in the morning hours. It is clearly conducted that $CO_2$ and $CH_4$ emissions were different by limited intake levels of feed.

• Clean Technology
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• v.21 no.4
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• pp.271-277
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• 2015

A photocatalyst which mixed by the commercialized P25-TiO₂ and a synthesized Ag_xO was used in an appropriate weight ratio to effectively produce hydrogen gas in this study. The Ag_xOs were synthesized with the conventional sol-gel method, and tetramethylammonium hydroxides were added at the synthesis process in order to stabilize the solutions, and then the solutions were heat-treated at the temperatures of -5, 25, and 50 ℃, resulted to obtain the three types of silver oxides. Physicochemical properties of the synthesized Ag_xOs were identified through X-ray diffraction analysis (XRD), scanning emission microscopy (SEM), ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). In the photolysis results of water/methanol (weight ratio 1:1) solution, the mixture of P25-TiO₂/Ag_xO exhibited a significantly higher hydrogen gases evolution, compared to that of pure P25-TiO₂. Additionally, the addition of H₂O₂ as an supplement oxidant and in Ag_xO synthesized at 50 ℃ improved the hydrogen production efficiency. In particular, the emitted hydrogen gases reached to 13,000 μmol during 8 hours when a mixed catalyst, Ag_xO of 0.1 g and P25-TiO₂ of 0.9 g, were used.

• Membrane Journal
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• v.29 no.1
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• pp.51-60
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• 2019

In order to improve gas separation properties of polymeric membranes which have been widely applied in the industry field, aluminosilicate hollow nanoparticles named as allophanes were synthesized by sol-gel method and formulated in Poly(dimethylsiloxane) (PDMS) matrix to investigate the gas separation properties of PDMS membrane. Transmission electron microscope (TEM), Energy dispersive X-ray analysis (EDX), X-ray diffractometer (XRD), Surface area and pore size analyzer (BET) and Fourier transform infrared spectrophotometer (FTIR) were carried out to characterize the synthetic allophanes. Then the PDMS mixed matrix membranes were prepared by adding different volume fraction of allophanes. To examine the effect of allophanes addition in PDMS matrix using unmodified allophane and modified ones, the gas permeation experiments were performed using oxygen, nitrogen, methane and carbon dioxide. As the volume fraction of modified allophane increased up to 4.05 Vol% the permeability of four test gases through PDMS mixed matrix membranes increased. Also, the selectivity of $O_2/N_2$ and $CO_2/CH_4$ increased with the contents of the modified allophane. Further improvement of gas separation properties of PDMS mixed matrix membranes containing higher volume percent of allophanes can be expected as long as well dispersion of allophanes in PDMS matrix can be achieved for better PDMS membranes.

• Journal of Sensor Science and Technology
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• v.6 no.5
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• pp.369-375
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• 1997

$V_{2}O_{5}/ThO_{2}/Pd$-doped $SnO_{2}$ sensor has a good selectivity and stability to CO at high sensor temperature of about $500^{\circ}C$, and shows rapid response. In particular, many kinds of interference gases, such as $NO_{x}$, $C_{3}H_{8}$, $CH_{4}$ and $SO_{2}$ have been found to give only a slight influence on the sensor selectivity to CO gas sensitivity by doped $V_{2}O_{5}$ (3.0 wt.%). For the sensor we used well-known thick film technological route with $V_{2}O_{5}$(3.0 wt.%), Pd(1.0 wt.%) and $ThO_{2}$(l.5 wt.%) as catalytic materials. In the case of mixed $NO_{x}$-CO gases, as combustion exhaust gas, only CO detection by $SnO_{2}$ type semiconductor sensor is generally very difficult because of $NO_{x}$ interference. The developed sensors can use to measure the exhausting gas of the automobile or the boiler for the Air-to-Fuel ratio control.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.227-234
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• 2002

With the increasing environmental consideration and stricter regulations, gasification of waste is considered to be more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in the fixed bed gasifier to investigate the gasification behavior with the operating conditions. Waste pelletized with a diameter of 2~3cm and 5cm of length was gasified at the temperature range of 1100~145$0^{\circ}C$. It was shown that the composition of H$_2$ was in the range of 30~40% and CO 15~30% depending upon oxygen/waste ratio. Casification of waste due to thermoplastic property from mixed plastic melting and thermal cracking shows a prominent difference from that of coal or coke. It was desirable to maintain the top temperature up to foot to ensure the mass transfer and uniform reaction through the packed bed. As the bed height was increased, the formation of H$_2$ and CO was increased whilst $CO_2$ decreased by the char-$CO_2$ reaction and plastic cracking. From the experimental results, the cold gas efficiency was around 61% and heating values of product gases were in the range of 2800~3200㎉/Nm3.

• Laser Solutions
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• v.7 no.2
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• pp.19-26
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• 2004

The effect of shield gas on the weldability, mechanical properties and formability of CO2 laser weld joint in 600MPa grade high strength steel was investigated. Bead on plate welds were made under various welding speed and shield gas. Tensile test was carried out under the load of perpendicular and parallel direction to the weld line, Formability of the joint was evaluated by Erichsen test. As the welding speed increases, the porosity fraction decreases. The porosity fraction in the joint used Ar-$50\%He$ mixed gas as a shield gas was lower than that of the joint used Ar gas. Hardness at the weld metal of full penetrated joint was nearly equal to that of water quenched raw metal. In a tensile test under a perpendicular load to the weld axis, strength and elongation of joint produced by optimum condition were nearly equal to those of base metal. However, the strength of joint in a tensile test under a parallel load to weld axis was higher than that of raw metal, but the elongation of joint was lower than that of raw metal. Elongation and formability were further increased by the method of using Ar+He mixed gas as a shield gas as compared with Ar gas. Formabilities of joints were recorded ranging from $58\%\;to\;70\%$ of that of base metal with different shield gases.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.3
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• pp.281-290
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• 2011

In this study, a series of experiments were carried out to measure temporal stability of reduced sulfur compounds (RSCs) in Tedlar bag samples as a function of elapsed storage time. To this end, temporal variability of 4 RSC standard gases ($H_2S$, $CH_3SH$, DMS, DMDS) was measured up to 29 days. For the purpose of comparison, RSC samples were stored in both individual and mixed state. In the case of mixed standard, samples were also examined to allow comparison between light and dark condition. Then results of $CH_3SH$ data were the most stable with the least change in its concentrations through the end of exps (29 days). When compared with previous studies, the extent of stability appeared to be influenced by the initial concentration levels of samples. When the patterns were compared between individual and mixture samples, differences were not significant in the case of $H_2S$ and DMS. The effects of light conditions on temporal stability were seen to be fairly sensitive on most RSC other than $H_2S$. The results of our study confirm that the stability of RSC storage is affected by their involvement in photochemical reactions.