• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2753-2760
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• 2021

This paper proposes using sodium-cooled fast reactor technologies for use in hydrogen vapor methane (SMR) modification. Using three independent energy rings in the Russian BN-600 fast reactor, steam is generated in one of the steam-generating cycles with a pressure of 13.1 MPa and a temperature of 505 ℃. The reactor's second energy cycles can increase the gas-steam mixture's temperature to the required amount for efficient correction. The 620 ton/hr 540 ℃ steam generated in this cycle is sufficient to supply a high-temperature synthesis current source (700 ℃), which raises the steam-gas mixture's temperature in the reactor. The proposed technology provides a high rate of hydrogen production (approximately 144.5 ton/hr of standard H₂), also up to 25% of the original natural gas, in line with existing SMR technology for preparing and heating steam and gas mixtures will be saved. Also, exergy analysis results show that the plant's efficiency reaches 78.5% using HTR heat for combined hydrogen and power generation.

• Journal of Hydrogen and New Energy
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• v.30 no.2
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• pp.111-118
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• 2019

Greenhouse gas emissions have a profound effect on global warming. Various environmental regulations have been introduced to reduce the emissions. The largest amount of greenhouse gases, including carbon dioxide, is produced in the steel industry. To decrease carbon dioxide emission, hydrogen-based iron oxide reduction, which can replace carbon-based reduction has received a great attention. Iron production generates various by-product gases, such as cokes oven gas (COG), blast furnace gas (BFG), and Linz-Donawitz gas (LDG). In particular, COG, due to its high concentrations of hydrogen and methane, can be reformed to become a major source of hydrogen for reducing iron oxide. Nevertheless, continuous COG cannot be supplied under actual operation condition of steel industry. To solve this problem, this study proposed to use two alternative COG-based fuel mixtures; one with natural gas and the other with biogas. Reforming study on two types of mixed gas were carried out to evaluate catalyst performance under a variety of operating conditions. In addition, methane conversion and product composition were investigated both theoretically and experimentally.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.5-11
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• 2014

In this study, greenhouse gas emission for small scale landfill (H and Y landfill) was investigated to deduce special the methane generation rate constant(k). To achieve the purpose, the data of physical composition was collected and amount of LFG emission was calculated by using FOD method suggested in 2006 IPCC GL. Also, amount of LFG emission was directly measured in the active landfill sites. By comparing the results, the methane generation rate constant(k), which was used as input variable in FOD method suggested in 2006 IPCC GL, was deduced. From the results on the physical composition, it was shown that the ranges of DOC per year in H (1997~2011) and Y (1994~2011) landfill sites were 13.16 %~23.79 % ($16.52{\pm}3.84%$) and 7.24 %~34.67 % ($14.56{\pm}7.30%$), respectively. The DOC results showed the differences with the suggested values (= 18 %) in 2006 IPCC GL. The average values of methane generation rate constant(k) from each landfill site were $0.0413yr^{-1}$ and $0.0117yr^{-1}$. The results of methane generation rate constant(k) was shown big difference with 2006 IPCC GL defualt value (k = 0.09). It was confirmed that calculation results of greenhouse gas emission using default value in 2006 IPCC GL show excessive output.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.890-893
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• 2012

Gas hydrates are solid crystal structures formed by enclathration of gaseous guest species into 3-dimensional lattice structure of hydrogen-bonded water molecules. These compounds can be potentially used as an energy storage/transportation medium because they can hold a large amount of gas in a small volume of the solid phase. In addition, huge amount of natural gas, buried in seabeds or permafrost region in the form of the solid hydrate, is regarded as a future energy source. In this study, synthesized natural gas, whose composition is 90.0 mol% of methane, 7.0 mol% of ethane, and 3.0 mol% of propane, was used to identify formation behaviors of natural gas hydrates for the purpose of applying the gas hydrate to a storage/transportation medium of natural gas. According to the experimental results obtained by means of the solid-state NMR and high-resolution powder XRD methods, it is found that formed natural gas hydrates have crystal structure of the structure-II hydrate, and that methane occupies both small and large cages, while the others only occupy large ones. In addition, both the NMR spectroscopy and the gas chromatograph showed that there exists preferential occupation among the natural gas components during the hydrate formation. Compositional changes after the hydrate formation revealed that the preferential occupation is in order of propane, ethane, and methane (propane is the most preferential guest species when forming natural gas hydrates).

• The Korean Journal of Petroleum Geology
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• v.6 no.1_2 s.7
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• pp.37-43
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• 1998

Chemical components of water, chemical and isotopic compositions of extractable gases were analyzed to characterize the properties of the natural gases which are dissolved in ground water in the Pohang area. Amount of total extracted gases ranges from 27 ml/l to 50.1 ml/l. Hydrocarbon gases are composed of methane ($27{\~}376,420 ppm$) and ethane ($19{\~}127 ppm$). Amount of total hydrocarbon gases is related to the lithology and geological factors around the reservoir. Quantity of hydrocarbon gases tends to increase in the Tertiary reservoirs and in the reservoirs where the Tertiary formations are thick enough. According to the relationship between hydrocarbon gases and total solids in the ground water, it is believed that the hydrocarbon gases were dissolved in the Tertiary formation water. Based on the methane content ($>99.9\%$) and isotopic composition (${\delta}C^{13};-73.1\%_{\circ}{\~}-43.22\%_{\circ}$), we interpret the gases to be of predominantly biogenic origin which were generated by the methanogenic bacterial processes under the low temperature and anoxic conditions.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.515-521
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• 2004

Anaerobic digestion has many advantages over the more conventional aerobic treatment processes such as low levels of excess sludge production, low space (area) requirements, and the production of valuable biogas. The purpose of this study was to evaluate the effect of organic loading rate of anaerobic digestion on thermophilic($55^{\circ}C$) and mesophilic($35^{\circ}C$) conditions. Fluorescent in situ hybridization (FISH) method was also used to study the microbial community in the reactors. The stabilizing time in mesophilic anaerobic reactors was shorter as approximately 20 days than 40 days in the thermophilic anaerobic reactors. The amount of methane production rate in anaerobic reactors was independent of the concentrations of supplied substrates and the amount of methanogens. When the microbial diversity in the mesophilic and thermophilic reactors, which had been treated with acetate-based artificial wastewater, were compared, it was found that methanogenesis was carried out by microbial consortia consisting of bacteria and archaea such as methanogens. To investigate the activity of bacterial and archaeal populations in all anaerobic reactors, the amount of acetate was measured. Archaea were predominant in all reactors. Interestingly, Methanothrix-like methanogens appeared in mesophilic anaerobic reactors with high feed substrate concentrations, whereas it was not observed in thermophilic anaerobic reactors.

• Journal of the Korean Institute of Gas
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• v.14 no.2
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• pp.7-14
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• 2010

Synthesis gas was produced by the partial oxidation of methane. For the preparation of catalysts, Ni, known to be active in this reaction and cheap, was used as the active component and $CeO_2$, having high oxygen storage capability and high redox ability, was used as the support. The catalysts were prepared by the impregnation and urea methods. The catalyst prepared by the urea method showed about 11 times higher surface area and finer particle size than that prepared by the impregnation method. The catalysts prepared by the urea method showed higher methane conversion and synthesis gas selectivity than that prepared by the impregnation method. In this reaction, carbon deposition is a problem to be solved, so La was added to the catalyst system to reduce the carbon deposition. TGA analysis results showed that there was 2% carbon deposition with La-added catalysts and 16% with La-free catalysts. It was found that the addition of La decreases the amount of carbon deposition and prevents catalyst deactivation.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.13-18
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• 2014

BMP test was carried out to evaluate the characteristics for co-digestion of night soil and food waste. 6 types of sludge were tested in 30 days which were raw, excess, digested, night soil/septic tank (1:1), food waste (food : dilution water = 1:1), and mixed sludge. Bio gas was produced actively after 2 days, and continued in 2 weeks. Gas generation amount was decreased rapidly after considerable space of time. Especially maximum productivity of gas was shown in 7~8 days. The ultimate methane yields of raw, excess, digested, night soil/septic tank, food waste, and mixed sludge were 64.63, 67.49, 66.45, 72.44, 107.85, and 46.71 mL $CH_4/g$ VS respectively from Modified Gompertz model. The lag growth phase time and maximum specific methane production rate of mixed sludge were 1.88 day and 80.4 mL/day respectively. The methane potential of mixed sludge was higher than individual sludge. So high methane potential was expected by controlling mixing ratio of food waste. Besides stable operation of digestion tank and the solution of oligotrophic problem were possible.

• Korean Journal of Microbiology
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• v.45 no.1
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• pp.17-25
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• 2009

We studied soil components, methane production, the number of methanogens, and T-RFLP patterns dependent on agricultural methods with the change of seasons. There is no regular increase or decrease tendency of the most soil components followed by sampling period. And the water content in soil was higher in October than May. Also a lot of methanogens existed in soil, and acetotrophs were relatively of smaller number than hydogenotrophs and formate utilizing methanogens using MPN (most probable number) enumeration. In the experiment using the formate, it was used from the first week, and only a minute amount was detecte after four weeks. However in the acetate, it was increased until the third week, and after that was consumed. And there was higher methane production for all soil samples which administered with the hydrogen spike. The activity of methanogens was higher in the organic and low-agrichemical agricultural method samples, and the organic agricultural method had high methanogen activity among the other samples. A result of T-RFLP pattern of mcrA gene digested with Sau96I, methanogen community have a little relation with agricultural methods and seasons. This results also agreed to no critical difference the soil components dependent on agricultural methods, but some analytical data have a positive relationship with a agricultural methods. Therefor we could concluded that the comparison study of community for soil bacteria sufficiently could be useful for the microbiological indicator.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.214-222
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• 2012

Several acidogenesis batch tests, and BMP (Biochemical Methane Potential) with food waste leachate was tested at various organic loading rates (OLRs) on the mesophilic ($35^{\circ}C$) and thermophilic ($55^{\circ}C$) conditions. In acidogenesis batch test, VS removal efficiencies were 27.3% and 30.6% at $35^{\circ}C$ and $55^{\circ}C$, respectively. Removal efficiency of VS at $55^{\circ}C$ was higher than that at $35^{\circ}C$. With decrease in VS, SCOD increased as reaction time increased. Solubilization efficiency of VS were 27.4% and 33.4% at each reaction temperature within 4 days acid fermentation. Methane yield were 461 and 413 $mLCH_4/gVS$ at mesophilic and thermophilic BMP test, respectively. SCOD solubilizations in the themophilic acid fermenter showed 8~17% higher than those in the mesophilic fermenter. COD removal efficiency showed higher in the mesophilic acid fermenter at low organic loading rate. While at high organic loading rate, it was higher in the thermophilic acid fermenter. VS removal efficiency was higher at the mesophilic temperature, however, it decreased at OLR higher than 6 kg $COD/m^3{\cdot}day$. On the contrary, VS removal efficiency did not decrease but maintain at thermophilic temperature. The amount of methane gas generated from mesophilic methanogenesis digester was 12.6, 21.6, 27.4 L/day at OLR of 4, 5, 6 $COD/m^3{\cdot}day$, respectively. The amount of methane gas generated from themophilic methanogenesis digester was 14.3, 20.6, 25.2 L/day at each OLR, respectively, which is about 15~20 L/day lower than those generated at mesophilic digester.