• Clean Technology
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• v.26 no.4
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• pp.239-250
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• 2020

Biomass is an abundant renewable energy resource that can replace fossil fuels for the reduction of greenhouse gas (GHG). Indonesia has a large number of cheap biomass feedstocks, such as reforestation (waste wood) and palm residues (empty fruit bunch or EFB). In general, raw biomass contains more than 20% moisture and lacks calorific value, energy density, grindability, and combustion efficiency. Those properties are not acceptable fuel attributes as the conditions currently stand. Recently, torrefaction facilities, especially in European countries, have been built to upgrade raw biomass to solid fuel with high quality. In Korea, there is no significant market for torrefied solid fuel (co-firing) made of biomass residues, and only the wood pellet market presently thrives (~ 2 million ton yr-1). However, increasing demand for an upgraded solid fuel exists. In Indonesia, torrefied woody residues as co-firing fuel are economically feasible under the governmental promotion of renewable energy such as in feed-in-tariff (FIT). EFB, one of the chief palm residues, could replace coal in cement kiln when the emission trading system (ETS) and clean development mechanism (CDM) system are implemented. However, technical issues such as slagging (alkali metal) and corrosion (chlorine) should be addressed to utilize torrefied EFB at a pulverized coal boiler.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.402.1-402.1
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• 2016

The performance of solid oxide fuel cells (SOFCs) is directly related to the electrocatalytic activity of composite electrodes in which triple phase boundaries (TPBs) of metallic catalyst, oxygen ion conducting support, and gas should be three-dimensionally maximized. The distribution morphology of catalytic nanoparticle dispersed on external surfaces is of key importance for maximized TPBs. Herein in situ grown nickel nanoparticle onto the surface of fluorite oxide is demonstrated employing gadolium-nickel co-doped ceria ($Gd0.2-xNixCe0.8O2-{\delta}$, GNDC) by reductive annealing. GNDC powders were synthesized via a Pechini-type sol-gel process while maximum doping ratio of Ni into the cerium oxide was defined by X-ray diffraction. Subsequently, NiO-GNDC composite were screen printed on the both sides of yttrium-stabilized zirconia (YSZ) pellet to fabricate the symmetrical half cells. Electrochemical impedance spectroscopy (EIS) showed that the polarization resistance was decreased when it was compared to conventional Ni-GDC anode and this effect became greater at lower temperature. Ex situ microstructural analysis using scanning electron microscopy after the reductive annealing exhibited the exsolution of Ni nanoparticles on the fluorite phases. The influence of Ni contents in GNDC on polarization characteristics of anodes were examined by EIS under H2/H2O atmosphere. Finally, the addition of optimized GNDC into the anode functional layer (AFL) dramatically enhanced cell performance of anode-supported coin cells.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.349-358
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• 1996

The leaching behavior of uranium from unirradiated CANDU UO$_2$ fuel pellet in the spent fuel wet storage and disposal conditions has been investigated. A modified IAEA leach test method was used, and then the extent of leaching was monitored by analysis for uranium in the leachant. The leach test has been performed in various leachants(demineralized water and boric acid solution at pH=6, synthetic granite groundwater) for a long-term period of 5.4 years, and the effect of temperature on the leach rate of uranium has been analyzed. The leach rates of uranium at $25^{\circ}C$ were dependent on the leachants. Over initial 100 days of leach periods, the leach rate in groundwater was the highest in three leachants and no significant differences of leach rates ore observed in the demineralized oater and boric acid solution. But these leach rates in three leachants around 2,000 days at $25^{\circ}C$ appeared to be reached the steady rates in the range of 1~5$\times$10$^{-8}$ g/$\textrm{cm}^2$ day. The leach rate of uranium in groundwater shooed to be independent of the temperature, but those in both demineralized water and boric acid solution increased with temperature. These results show that the leaching behavior of uranium from UO$_2$ fuel in both the demineralized water ann boric acid may be controlled tv the surface oxidative.dissolution reaction of UO$_2$ and the leach rate of uranium in groundwater at room temperature could mainly be controlled by the complex reaction of dissolved uranyl ions with carbonate ions and no variation of leach rate of UO$_2$ in groundwater with temperature may be due to the local deposition of passivating uranyl phases on the surface.

• Journal of Powder Materials
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• v.27 no.2
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• pp.119-125
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• 2020

One of the promising candidates for accident-tolerant fuel (ATF), a ceramic microcell fuel, which can be distinguished by an unusual cell-like microstructure (UO₂ grain cell surrounded by a doped oxide cell wall), is being developed. This study deals with the microstructural observation of the constituent phases and the wetting behaviors of the cell wall materials in three kinds of ceramic microcell UO₂ pellets: Si-Ti-O (STO), Si-Cr-O (SCO), and Al-Si-Ti-O (ASTO). The chemical and physical states of the cell wall materials are estimated by HSC Chemistry and confirmed by experiment to be mixtures of Si-O and Ti-O for the STO; Si-O and Cr-O for SCO; and Si-O, Ti-O, and Al-Si-O for the ASTO. From their morphology at triple junctions, UO₂ grains appear to be wet by the Si-O or Al-Si-O rather than other oxides, providing a benefit on the capture-ability of the ceramic microcell cell wall. The wetting behavior can be explained by the relationships between the interface energy and the contact angle.

• Journal of IKEEE
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• v.23 no.2
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• pp.586-593
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• 2019

In this paper, we introduce the wood pellet electric power generation system, which is an eco - friendly solid fuel processed pure wood, which is one of the largest capacity renewable power fuels in Korea, The Ministry of Commerce, Industry and Energy notified the Ministry of Land, Infrastructure, Transport and Tourism of the Ministry of Land, Transport and Maritime Affairs of the Ministry of Land, Transport and Maritime Affairs. Derived and validated. It is confirmed that the performance of the generator and the voltage control characteristics of excitation system are good even for the change of generator fuel. It can contribute to future reference at the plant that wants to replace fossil fuels with renewable fuels.

• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.8-13
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• 2006

The oxidation behavior of $UO_2$, pellet was studied using an XRD and a thermogravimetric analyzer in the temperature range from 573 to 873 K and in the density range from 94.64 to 99.10% of theoretical density in air. It was found from the XRD study that $UO_2$ was completely converted to $U_3O_8$ in this experimental temperature range. The formation of $U_3O_8$ displays sigmoidal reaction kinetics. The oxidation rate was reduced with density. Induction time for the oxidation of $UO_2$ was delayed with density because of open pore formed in surface of $UO_2$ pellet. The activation energy for oxidation of $UO_2$ was determined to be 89.54 kJ/mol and 34.40 kJ/mol in the temperature range from 573 to 723 K and from 723 to 873 K, respectively.

• Journal of the Korean Wood Science and Technology
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• v.38 no.1
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• pp.36-42
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• 2010

This study has been carried out to investigate the characteristics of pellets manufactured from sawdust, and a mixture of liquid wood-tar and sawdust. Pellets were prepared at room temperature under 2000 kgf/$cm^2$ using an universal testing machine. The pellets prepared from Q. variabilis wood had slightly higher density than those prepared from P. densiflora wood. The amount of fine particles from Q. variabilis wood pellets was smaller than those from P. densiflora wood. The pellets from P. densiflora wood had higher heating values than those from Q. variabilis wood. The wood pellets manufactured with wood tar showed higher moisture content, density and heating value, but lower fine particles. From the experimental results, it is suggested that wood tar can be used to obtain the higher quality wood pellets.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.455-464
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• 1999

The effect of TiO$_2$ on the sintering behavior of mixed UO$_2$-U$_3$O$_{8}$ Powder compacts has been investigated using the U$_{3}$O$_{8}$ powder made tv oxidation of defective UO$_{2}$ pellets. Without TiO$_2$, UO$_2$ pellet density is inversely proportional to U$_3$O$_{8}$ content and is below 94 %TD in the U$_3$O$_{8}$ range above 15 wt%. Using more than 0.1 wt % TiO$_2$, however, the density decreases slightly with U$_3$O$_{8}$ content and thus is higher than about 94% TD in the whole range of U$_3$O$_{8}$ content. The grain sizes of UO$_2$ pellets with more than 0.1 wt % TiO$_2$are larger than about 30${\mu}{\textrm}{m}$. Therefore, the U$_3$O$_{8}$ Powder can be reused without any restriction on its amount in UO$_2$ pellet fabrication by sintering the mixed UO$_2$-U$_3$O$_{8}$ compact with the aid of TiO$_2$. Mechanisms for densification and grain growth are proposed and discussed, based on a dilatometry study and an examination of microstructure. microstructure.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.2
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• pp.77-84
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• 2005

A voloxidizer for a hot cell demonstration, that handles spent fuels of a high radiation level in a limited space should be small and spent fuel powders should not be dispersed out of the equipment involved. In this study a density rate equation as well as the Stokes'equation has been proposed in order to obtain the theoretical terminal velocity of powders. The terminal velocity of U$_{3}$O$_{8}$ has been predicted by using the terminal velocity of SiO$_{2}$, and then determination has been the optimum air flow rate which is able to prevent powders from scattering. An equation which has shown a relationship between theoretical terminal velocities of U$_{3}$O$_{8}$ and SiO$_{2}$ has been derived with the help of the Stokes'equation, and then an experimental verification made for the theoretical Stokes' equation of SiO$_{2}$ by means of an experimental device made of acryl. The theoretical terminal velocity based on the proposed density rate equation has been verified by detecting U$_{3}$O$_{8}$ powders in a filter installed in the mock-up voloxidizer. As the results, the optimum air flow rates seem to be 20 LPM by the Stokes'equation while they are 14.5 L/min by the density rate equation. At the experiments with the mock-up voloxidizer, a trace amount of U$_{3}$O$_{8}$ seems to be detectable at the air flow rate of 14.5 L/min by the density rate equation, but U$_{3}$O$_{8}$ powders of 7$\mu$m diameter seem detectable at the air flow rate of 20 L/min by the Stokes'equation. It is revealed that 14.5 L/min is the optimum air flowe rate which is capable of preventing U$_{3}$O$_{8}$ powders from scattering in the UO$_{2}$ voloxidizer and the proposed density rate equation is proper to calculate the terminal velocity of U$_{3}$O$_{8}$ powders.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.757-767
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• 2015

This study was conducted to investigate the effects of moisture content and particle size of sawdust on the fuel characteristics of wood pellets produced with Mongolian oak (Quercus mongolica, QUM), red pine (Pinus densiflora, PID) and larch (Larix kaempferi, LAK) sawdust using a flat-die pelletizer. Prior to produce wood pellets, the sawdust was controlled to the moisture content of 8, 11, 12% and was screened to the particle size of 2 and 4 mesh. In the analysis of its chemical composition, QUM had a high ash content, and PID and LAK contained large amount of lignin. In case of the fuel characteristics, PID pellets had the lowest moisture content of pellets (P-MC), and LAR pellets was found to have the highest bilk density (BD) and durability (DU). With the increase of moisture content of sawdust (S-MC), P-MC and DU of QUM, PID and LAK pellets increased, but BD of QUM and LAK pellets decreased. When size of sawdust used for the production of wood pellets decreased, P-MC and BD of LAK pellets and BD of QUM pellets increased. Decrease of particle size contributed to the increase of DU of QUM, PID and LAK pellets. In addition, BD and DU of QUM pellets produced with 12% S-MC sawdust increased as its particle size reduced. For LAK pellets, DU was not influence by particle size in the S-MCs of 10% and 12%, but increased with the decrease of particle size in the S-MC of 8%. Based on the results and economical aspects, 10% MC and 2 mesh paricle size for QUM sawdust and 12% MC and 2 mesh particle size for PID sawdust might be optimal conditions for pellets production, and fuel characteristics of wood pellets produced by the conditions greatly exceeded the minimum requirements for the $1^{st}$-grade wood pellets of the standard designated by Korea Forest Research Institute.