• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.8
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• pp.636-644
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• 2008

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

• Journal of Hydrogen and New Energy
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• v.25 no.4
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• pp.425-435
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• 2014

Simulation studies on catalytic methanation reaction in externally cooled tubular reactor filled with monolithic catalysts were carried out using a general purpose modelling tool $gPROMS^{(R)}$. We investigated the effects of operating parameters such as gas space velocity, temperature and pressure of feeding gas on temperature distribution inside the reactor, overall CO conversion, and chemical composition of product gas. In general, performance of methanation reaction is favored under low temperature and high pressure for a wide range of their values. However, methane production becomes negligible at temperatures below 573K when the reactor temperature is not high enough to ignite methanation reaction. Capacity enhancement of the reactor by increasing gas space velocity and/or gas inlet pressure resulted no significant reduction in reactor performance and heat transfer property of catalyst.

• Journal of Animal Science and Technology
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• v.54 no.1
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• pp.15-22
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• 2012

This study was conducted to investigate the effects of grain sources on the ruminal methane production in Hanwoo steers. Six Hanwoo steers (BW = 614.4 ${\pm}$ 8.3 kg) were fed, on a DM basis (TDN 6.91 kg), 10% rice straw and 90% barley or corn based concentrate, respectively, according to Korean Feeding Standards (Hanwoo). Each period lasted 18 days including a 14-day adaptation and a 4-day measuring period. The steers were in the ventilated hood-type respiration chamber system (one cattle per chamber) during each measuring period to measure heat and methane production for 1 day. Nutrient intake and digestibility were not affected by steer fed grain sources. Methane concentration was not affected by steer fed either barley or corn-based concentrate, respectively (0.022% vs. 0.025%). Methane production was greater by steers fed corn than those fed barley (119.3 g/day vs. 139.4 g/day). This result indicated that methane emission factor by maintenance energy requirement for the late fattening Hanwoo fed corn was higher than the steers fed barley (43.6 kg/head/year) vs. corn (50.9 kg/head/year). Methane conversion rate (Ym) was 0.04 Ym and 0.05 Ym for barley and corn, respectively.

• 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.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.1
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• pp.35-46
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• 1997

An experiment with growing bulls were conducted to determine the effect of supplementation of a straw (S) with 15% molasses and 3% urea as an intimate mix (UMS) on its dry matter (DM) intake and digestibility (DMD) and reduction of methane ($CH_4$) production from fermentation in vitro of the straw. In the next experiment, the feeding of the UMS was compared with that of the feeding of molasses and urea in meals (DS) or in lick blocks (DSUMB) as supplements to straw. The UMS feeding increased daily intake of straw DM ($89.5 g{\cdot}kgW^{-0.75}$, p < 0.01) and digestible crude protein (DCP 333 g, p < 0.001) and nitrogen (N) balances ($508mg{\cdot}kgW^{-0.75}{\cdot}d^{-1}$, p < 0.01) of the bulls than the feeding of 'S' ($65g{\cdot}kgW^{-0.75}$, 55 g and $8.0mg{\cdot}kgW^{-0.75}{\cdot}d^{-1}$, respectively). It also increased the digestibility of DM ($594g{\cdot}kg^{-1}$, p < 0.05), organic matter (OM, $641g{\cdot}kg^{-1}$, p < 0.05), CP ($619g{\cdot}kg^{-1}$, p < 0.001) and acid detergent fibre (ADF, 773, p < 0.05). The $CH_4$ emitted per g of DOM apparently fermented in the rumen (DOMR) was 91.0 ml in the 'S' and reduced (p < 0.05) to 61.6 ml in the UMS. The feeding of the UMS when compared with that of the DS or DSUMB also gave a higher straw intake (1.77% of live weight, LW, p <0.01) and ADF digestibility ($516g{\cdot}kg^{-1}$, p < 0.05) than the other diets (1.52% or 1.55% LW and 472 or $490g{\cdot}kg^{-1}$, respectively) in association with the increased microbial N yield in the rumen (14.1, 5.62 or $17.0g{\cdot}kg^{-1}$ DOMR, respectively, p < 0.05), daily LW gains (233, 125 or 93 g, respectively, p < 0.05) and feed conversion ratios of the diets (26.0, 56.1, or 57.6 g feed/g LW gain, p > 0.05, respectively). It can be concluded that molasses and urea feeding as an intimate mix with straw (UMS) increased its digestion and intake in association with a reduced methane emissions in the rumen. When compared with that of their feeding in meals or in lick blocks as supplements to straw the UMS gave the highest straw in take and digestion and live weight gains of growing bulls concurring the finding that the UMS system may be the best way of molasses and urea feeding to ruminants fed straws.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1268-1272
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• 2008

Low temperature plasma applied with partial oxidation is a technique to produce synthesis gas from methane. Low temperature plasma reformer has superior miniaturization and start-up characteristics to reformers using steam reforming or CO$_2$ reforming. In this research, a low temperature plasma reformer using GlidArc discharge was proposed. Reforming characteristics for each of the following variables were studied: gas components ratio (O$_2$/CH$_4$), the amount of steam, comparison of reaction on nickle and iron catalysts and the amount of CO$_2$. The optimum conditions for hydrogen production from methane was found. The maximum Hydrogen concentration of 41.1% was obtained under the following in this condition: O$_2$/C ratio of 0.64, total gas flow of 14.2 L/min, catalyst reactor temperature of 672$^{\circ}C$, the amount of steam was 0.8, reformer energy density of 1.1 kJ/L with Ni catalyst in the catalyst reactor. At this point, the methane conversion rate, hydrogen selectivity and reformer thermal efficiency were 66%, 93% and 35.2%, respectively.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.618-624
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• 2007

thermochemical methane reforming consisting of two steps on Cu/Fe/Zr mixed oxide media was carried out using a fixed bed infrared reactor. In the first step, the metal oxide was reduced with methane to produce CO, $H_2$ and the reduced metal oxide in the temperature of 1173 K. In the second step, the reduced metal oxide was re-oxidized with steam to produce $H_2$ and the metal oxide in the temperature of 973 K. The reaction characteristics on the added amounts of Cu in Cu/Fe/Zr mixed oxide media and the cyclic tests were evaluated. With the increase of the added amount of Cu in Cu/Fe/Zr mixed oxide media, the conversion of $CH_4$, the selectivity of $CO_2$ and the $H_2/CO$ molar ratio were increased, while the selectivity of CO was decreased in the first step. On the other hand, the evolved amount of $H_2$ was decreased with increasing the added amount of Cu in the second step. The $Cu_xFe_{3-x}O_4/ZrO_2$ medium added with Cu of x = 0.7 showed good regeneration properties in the 10th cyclic tests indicating that the medium had high durability. In addition, the gasification of the deposited carbon in the water splitting step was promoted with the addition of Cu in the media.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1113-1118
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• 2008

Characteristics of reduction properties and carbon deposition of $CuFe_2O_4$ and $Fe_3O_4$ were investigated by using TGA, XRD, SEM, TEM and gas analysis at $900^{\circ}C$. XRD analyses indicated that the reduced $Fe_3O_4$ was composed of Fe, graphite and $Fe_3C$ phases. In contrast, the reduced $CuFe_2O_4$ did not show the graphite or $Fe_3C$ phases. It was observed by SEM analysis that the surface of the $Fe_3O_4$ was completely covered with carbon, after methane partial oxidation. From gas analysis, $CuFe_2O_4$ showed much higher methane conversion and reduction kinetics as compared to the $Fe_3O_4$ under the same reaction conditions and the estimated carbon deposition amounts on the reduced $CuFe_2O_4$ was much lower than those on the reduced $Fe_3O_4$ during the syngas production process. It was found by TEM that carbon on the reduced $Fe_3O_4$ particles has a platelet shape.

• Journal of Hydrogen and New Energy
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• v.23 no.3
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• pp.213-218
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• 2012

Steam reforming of methane (SRM) is the primary method to produce hydrogen. Commercial Ni-based catalysts have been optimized for SRM with excess steam ($H_2O/CH_4$ > 2.5) at high temperatures (> $700^{\circ}C$). However, commercial catalysts are not suitable under severe conditions such as stoichiometric steam over methane ratio ($H_2O/CH_4$ = 1.0) and low temperature ($600^{\circ}C$). In this study, 15wt.% Ni catalysts supported on $Ce_{0.8}Zr_{0.2}O_2$ were prepared at various calcination temperatures for SRM at a very high gas hourly space velocity (GHSV) of $621,704h^{-1}$. The calcination temperature was systematically varied to optimize 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst at a $H_2O/CH_4$ ratio of 1.0 and at $600^{\circ}C$. 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ exhibited the highest $CH_4$ conversion as well as stability with time on stream. Also, 15wt.% $Ni-Ce_{0.8}Zr_{0.2}O_2$ catalyst calcined at $500^{\circ}C$ showed the highest $H_2$ yield (58%) and CO yield (21%) among the catalysts. This is due to complex NiO species, which have relatively strong metal to support interaction (SMSI).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.425-430
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• 2012

In this study, a preconverter of an MCFC for an emergency electric power supplier is numerically simulated to increase the hydrogen production from natural gas (methane). A commercial code is used to simulate a porous catalyst with a user subroutine to model three dominant chemical reactions-steam reforming, water-gas shift, and direct steam reforming. To achieve a fuel conversion rate of 10% in the preconverter, the required external heat flux is supplied from the outer wall of the preconverter. The calculated results show that the temperature distribution and chemical reaction are extremely nonuniform near the wall of the preconverter. These phenomena can be explained by the low heat conductivity of the porous catalyst and the endothermic reforming reaction. The calculated results indicate that the use of a compact-size preconverter makes the chemical reaction more uniform and provides many advantages for catalyst maintenance.