• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.25-33
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• 2018

Renewable energy has been of interests in the area of modern alternative fuels. Biogas is produced in waste landfill sites through anaerobic digestion processes, including hydrolysis, acidogenesis, organic acid fermentation (acetogenesis), and methane fermentation (methanogenesis). High contents of fine dust and moisture limited its utilization for direct combustion, town gas and vehicle fuel. Thus, this study proposed a new design for a cooling device using a centrifugal cyclone for simultaneous removal of fine dust and moisture as a pretreatment in the purification processes. A heat exchanger and an ID fan, which are installed inside and outside of the cyclone, in order to cool the humid gas below the freezing point and form a foggy mist. Such an atmosphere enhanced to capture fine dust as recirculating the cold mist flow. The water removal rate was 80.8% at a relative humidity of 95%, and the particle removal efficiency was 98.3% for $2.5{\mu}m$. Simultaneous removal efficiency was 70.8% and 99.6% for particle and moisture respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.181.2-181.2
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• 2014

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly (methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. We found that the gas species of mass/charge (m/e) ratio of 15 ($CH_3{^+}$) was mainly originated from the thermal decomposition of PMMA, indicating that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for dominantly vaporizing hydrocarbon molecules from PMMA and the length of time, the gaseous hydrocarbon atmosphere is maintained, are dependent on both the heating temperature profile and the amount of a solid carbon feedstock. From those results, we strongly suggest that the heating rate and the amount of solid carbon are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ${\sim}2,700cm^2V^{-1}s^{-1}$ at room temperature, which is superior to common graphene converted from solid carbon.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.42-46
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• 2008

Even though fuel cell have high efficiency when pure hydrogen from gas tank is used as a fuel source, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of the electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. This study is aimed at investigating the effect of carbon dioxide on fuel cell performance. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run(10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography(GC).

• Journal of Energy Engineering
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• v.19 no.4
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• pp.240-245
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• 2010

In this study, characteristics of wood pellet gasification was studied using a Two Stage Gasifier which is consisted of pyrolysis reactor and ultra high temperature reformer. The average yields of $H_2$, $CH_4$, CO, $CO_2$ were 16.7, 11.3, 37.2, 26.6 L/mim, conversion rate from biomass to gas was 65% in pyrolysis reactor and gas yields in reformer were 55.4, 0.8, 120.8, 56.8 L/mim, respectively. The hydrogen flow rate from reformer is obtained 360.1 L/hr. The most of $CH_4$ was decomposed from 12.3 to 0.3 vol.% while $H_2$ is from 18.2 to 23.7 vol.% in reformer by methane dry reforming, Boudouard reaction, oxidation and/or steam reforming. The amount of $H_2O$ generated by hydration reaction from reformer was 1111.8 g, its accelerated conversion of $CH_4$ to other products. The conversion rate from $CH_4$ to other Compounds was 97.2%. Cold gas efficiency was 53.2%.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.2
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• pp.57-66
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• 2019

This study carried out on-site investigation and precision monitoring to prepare proper design and operation technical guidelines for the use of bio gas in organic waste resources (fertilizing urine, food waste, food waste, food waste, etc.). According to the government's mid- and long-term policy on bio gasification, the expansion of waste resources is actively being pushed forward. However, facilities that use the biogas produced for urban gas and transportation are still under-efficient. Precision monitoring was carried out for biogasification facilities of organic waste resources in seven locations nationwide. When the results of precision monitoring were summarized with the four-season average, the efficiency analysis of each organic waste resource showed that the organic breakdown rate was 66.3% on average on VS basis. Analysis of biogas characteristics before and after pretreatment revealed that the $H_2S$ average of the entire facility was measured at 949.7 ppm using iron salts and desulfurization (dry, wet) and that the quality refining facility shearing and rear end was 29.0 ppm and 0.3 ppm. The methane content was found to be reduced by 65.6% at the rear of the fire tank, 63.5% at the back and 97.5% at the rear.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.135-144
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• 2021

In this study, we investigated the characteristics of the process of hydrogen production using boil-of gas (BOG) generated from an LNG-fueled ship and the application of hydrogen fuel cell systems as auxiliary engines. In this study, the BOG steam reformer process was designed using the UniSim R410 program, and the reformer outlet temperature, pressure, and the fraction and consumption of the product according to the steam/carbon ratio (SCR) were calculated. According to the study, the conversion rate of methane was 100 % when the temperature of the reformer was 890 ℃, and maximum hydrogen production was observed. In addition, the lower the pressure, the higher is the reaction activity. However, higher temperatures have led to a decrease in hydrogen production owing to the preponderance of adverse reactions and increased amounts of water and carbon dioxide. As SCR increased, hydrogen production increased, but the required energy consumption also increased proportionally. Although the hydrogen fraction was the highest when the SCR was 1.8, it was confirmed that the optimal operation range was for SCR to operate at 3 to prevent cocking. In addition, the lower the pressure, the higher is the amount of carbon dioxide generated. Furthermore, 42.5 % of the LNG cold energy based on carbon dioxide generation was required for cooling and liquefaction.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.653-658
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• 2016

Poly(ether-block-amide)(PEBAX$_{(R)}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permselectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for PEBAX$^{(R)}$-1657 membrane, and compare with those obtained for other grade of pure PEBAX$^{(R)}$, PEBAX$^{(R)}$-2533 and PEBAX$^{(R)}$ based hybrid membranes. The hybrid membranes based PEBAX$^{(R)}$ were obtained by a sol-gel process using GPTMS ((3-glycidoxypropyl) trimethoxysilane) as the only inorganic precursor. Molecular structure and morphology of membrane were analyzed by $^{29}Si$-NMR, DSC and SEM. PEBAX$_{(R)}$-2533 membrane exhibited higher gas permeability coefficients than PEBAX$^{(R)}$-1657 membrane. This was explained by the increase of chain mobility. In contrast, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$-1657 membrane was higher than PEBAX$^{(R)}$-2533 membrane. It was explained by the decrease of diffusion selectivity caused by increase of chain mobility. For PEBAX$^{(R)}$/GPTMS hybrid membrane, gas permeability coefficients were decreased with reaction time. Gas permeability coefficient of $CH_4$ was more significantly decreased than $CO_2$. It can be explained by the reduction of chain mobility caused by the sol-gel process, and strong affinity of PEO segment with $CO_2$. Comparing with pure PEBAX$^{(R)}$-1657 membrane, ideal separation factor of $CO_2/CH_4$ for PEBAX$^{(R)}$/GPTMS hybrid membrane has decreased to 4.5%, and gas permeability coefficient of $CO_2$ has increased 3.5 times.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.541-554
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• 2000

Experimental study of anaerobic digestion process combined with and without the submerged separation membrane was investigated by using laboratory-scale reactor at the hydraulic retention time of 0.5 day and 1.0 day. The removal efficiencies of carbohydrate at the digester without and with membrane were 84.4 to 86.8 % and 99.6 to 99.7 %, respectively, and the methane gas recovery efficiencies were 0.4 to 1.2 % and 12.3 to 28.7 %. According to the measurement by the most probable numbers method. the numbers of various groups of bacteria in the digesters with membrane were enumerated in the following ranges ; acidogens : $1.7{\times}10^9$ to $5.0{\times}10^9MPN/m{\ell}$, homoacetogens : $5.0{\times}10^7$ to $2.4{\times}10^8MPN/m{\ell}$, $H_2$-utilizing methanogens : $1.3{\times}10^7$ to $9.2{\times}10^8MPN/m{\ell}$, and acetate-utilizing methanogens : $2.3{\times}10^6$ to $2.0{\times}10^8MPN/m{\ell}$. The number of methanogens at the digester with membrane increased by approximately $10^2$ to $10^4$ times in comparison with that of the digester without membrane.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.1
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• pp.77-87
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• 2014

In this study, an experimental approach to measure a suite of low weight hydrocarbons was investigated with an emphasis on ethylene (EL) along with many others (ethane (EA), propane (PA), propylene (PL), n-butane (BA), acetylene (AL), methyl acetylene (ML)). Their concentrations were quantified using GC-FID system equipped with thermal desorption (TD) system. The TD-based analysis was conducted using both Link Tube/Thermal Desorber (LT/TD) method and Modified Injection through a Thermal Desorption (MITD) method. The results of these analyses were evaluated in a number of respects. The system allowed the detection of all compounds except methane with the mean response factor (RF) of 10.28 (EA) to 11.94 (PL). The method detection limits of target compounds were seen in the range of 0.027 (ML) to 0.146 ng (BA). The emission flux of some environmental samples (fruits), when measured using a small flux chamber system, fell in the range of 0.14 (AL: Kiwi) to $181ng{\cdot}g^{-1}{\cdot}hr^{-1}$ (EL: Apple Peel). The results of this study confirm that the experimental approach developed in this study allows to accurately measure emissions of low weight hydrocarbons (LWHC) like ethylene from various natural and man-made source processes.

• Tunnel and Underground Space
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• v.7 no.2
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• pp.100-107
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• 1997

In case of a fire outbreak in a uni-directional road tunnel, the flow of traffic immediately behind the fire disaster will be stalled all the way back to the entrance of the tunnel. Furthermore, when the vehicle passengers try to flee away from the fire toward the entrance of the tunnel, the extremely hot fume that propagates in the same direction will be fatal to the multitudes evacuating, but may also cause damage to the ventilation equipments and the vehicles, compounding the evacuation process. This paper will present the 3-dimensional modelling analysis of the preventive measures of such a fume propagation in the same direction as the evacuating passengers. For the analysis, the fire hazard was assumed to be a perfect combustion of methane gas injected through the 1 m X 2 m nozzle in the middle of the tunnel, and the product of $CO_2$ as the indicator of the fume propagation. From the research results, when the fire hazard occurred in middle of the 400 m road tunnel, the air density decreased around the fire point, and the maximum temperatures were 996 K and 499 K at 210 m and 350 m locations, respectively, 60 seconds after fire disaster occurred, when the fumes were driven out only towards the exit-direction of the tunnel. By tracing the increase of $CO_2$ level over 1% mole fraction, the minimum longitudinal ventilation velocity was found to be 2.40 m/sec. Furthermore, through Analysis of the temperature distribution graphs, and observation of the cross-sectional distribution of $CO_2$ over 1% mole fraction, it was found that the fume did not mix with the air, but rather moved far in a laminar flow towards exit of the tunnel.