• Clean Technology
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• v.12 no.4
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• pp.232-237
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• 2006

The zinc-based desulfurization sorbents for a fluidized-bed system were prepared by a spray drying method and the effects of the pH and viscosity of the slurry on the attrition resistance of the prepared sorbents were investigated in this work. In order to improve the attrition resistance, alumina sol was used for an inorganic binder and pH of the slurry was changed for its better dispersion in slurry. The attrition resistance of the prepared sorbents decreased due to the phase transition of alumina sol to gel as the slurry pH increased to its basicity. The optimum pH condition for the good attrition resistance of the sorbents was about 6.0 in this study. It was confirmed that the attrition property of the sorbents were varied with the viscosity of the slurry. The attrition resistance of the sorbents prepared by the spray drying method increased as their bulk density increased, while it decreased as the surface area and porosity of the sorbents. The optimum viscosity for the high attrition was in the range 400-500 cP.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.217-221
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• 2008

In this study, We have been investigated the effect of calcination temperature and high-energy ball-milling of powder influences the $BaTiO_3$-based PTCR(Positive Temperature coefficient Resistance) characteristics and microstructure. The mixed powder was obtained from $BaCO_3$, $TiO_2$, $CeO_2$ ball-milled in attrition mill. The mixed powder was calcine from 1000 $^{\circ}C$ to 1200 $^{\circ}C$ in air and then it was sintered in reduction- re-oxidation atmosphere. As a result, The room-temperature electrical resistivity decreased and increased with increasing calcination temperature. specially, Attrition milled powder could have low room-temperature resistivity and high PTC jump order at 1100 $^{\circ}C$. attrition milling had lower room-temperature resistivity than ball milling. Particle size decreased by Attrition milling of powder influences in calcination temperature and room-temperature resistivity.

• Journal of Energy Engineering
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• v.13 no.1
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• pp.75-81
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• 2004

ZZFCa sorbents for hot gas desulfurization in IGCC were prepared by adding calcium oxide to ZZF sorbent in order to improve its attrition resistance in this study. ASTM attrition test for the sorbent was performed at several different weight percentages of CaO to investigate the attrition characteristics of ZBFCa sorbents as a function of CaO content. Attrition index of ZZF without CaO was 28.3% and its collected attrition index was 10.8％. ZZFCa-3 containing 3 wt% CaO showed the lowest attrition index (AI=17.3％, CAI=8.8％) in the test. From the results of SEM morphologies and particle size distribution measurements, ZZFCa-3 maintained a fine shape and a desirable average particle size even after attrition test. In the experiments of sulfidation/regeneration for ZZFCa-3 sorbent concentration of hydrogen sulfide in coal gas was lowered from 10000 ppm to below 1 ppm. Sulfur removing capacity was about 28.8 g S/100 g sorbent. Neither formation of CaSO$_4$ was observed in XRD measurement nor SO$_2$ slippage was observed during sulfidation process.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.3
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• pp.208-219
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• 2004

To find a suitable oxygen carrier particle for a 50kW chemical-looping combustor, which was designed and installed to demonstrate continuous oxidation and reduction, three oxygen carrier particles(NiO/bentonite, $NiO/NiAl_2O_4$, $CoO_x/CoAl_2O_4$) were prepared. The reactivity and the attrition resistance of particles were measured and investigated by a thermo-gravimetrical analyzer and an attrition test apparatus respectively. From the viewpoints of oxygen transfer capacity, optimum reaction temperature(operating temperature range), reaction rate, carbon deposition rate, and attrition resistance, NiO/bentonite particle showed better performance than the other particles, therefore we selected NiO/bentonite particle as an optimum oxygen carrier particle.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2067-2076
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• 2000

The experiments have been made to develop manganese-based sorbent(MT, MFT) for the removal of hydrogen sulfide from simulated hot coal gases. Manganese-based sorbents were tested in an ambient-pressure fixed-bed reactor to calculate H2S removal efficiency. and a three hole jet attrition tester to characterize the sorbent physical properties. According to the experimental results of attrition test. the attrition resistance of 5% bentonite containing sorbent was higher than that of 2% bentonite. The attrition resistances of both sorbents increased with induration temperature. Effects of sulfidation temperature. space velocity. and $H_2S$ concentrations on the $H_2S$ removal efficiency were investigated. Experimental results showed that $H_2S$ could be removed from 5,100ppmv to 20ppmv at $450^{\circ}C$, and to 30~65ppmv at $550{\sim}650^{\circ}C$ for both MT/MFT sorbents. As for the change of space velocity, the breakthrough time was decreased with space velocity.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.404-411
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• 2016

To select appropriate oxygen carrier candidates for chemical looping combustion, reduction characteristics of seven oxygen carriers were measured and discussed using three different reduction gases, such as $H_2$, CO, and $CH_4$. Moreover, attrition losses of those oxygen carriers also measured and compared. Among seven oxygen carrier particles, OCN703-1100 and NiO/bentonite particles showed higher oxygen transfer capacity than other particles, but these particles showed more attrition loss than other particles. C14 and C28 particles which used as cheap oxygen carriers in European country showed lower oxygen transfer capacity and less attrition loss. Based on the experimental results, we could select OCN717-R1SU, NC001, and N002 particles as candidates for future works because these oxygen carriers showed enough oxygen transfer capacity and good attrition resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.288-288
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• 2007

본 연구에서 내환원성 $BaTiO_3$의 PTCR(Positive Temperation Coefficient Resistance) 특성 및 미세구조에 대한 분쇄 및 출발 원료들의 하소 조건의 영향을 연구하였다. $BaCO_3$, $TiO_2$, $CeO_2$를 Attrition milling 하여 1차 혼합 및 분쇄한 후 건조하여 혼합분말을 얻었으며, $(Ba_{1-x}Ce_x)TiO_3$를 합성하기 위하여 $1000^{\circ}C{\sim}1200^{\circ}C$ 공기중에서 하소하였다. 각 하소온도에서 제조한 $(Ba_{1-x}Ce_x)TiO_3$에 첨가제를 2차 혼합하고 초미분쇄하여 분말을 제조하였다. 직경 5mm 의 시편을 제조하여 환원 및 재산화 분위기에서 소결을 한 후 상온저항값 및 R-T특성을 측정하였고 SEM 을 통해 미세구조를 관찰하였다. 또한 하소 후 온도에 따른 상분석을 XRD를 통하여 분석하였다. 그 결과 하소온도가 증가함에 따라 상온저항값은 감소하는 경황을 보였으며 PTC특성은 감소하다가 증가하는 경향을 보였다. 초미분쇄에 따른 입자크기는 $1{\mu}m$이하로 작아졌으며 미립화가 됨에 따라 하소/소결온도에 앙향을 줄 것으로 사료된다.

• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.302-308
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• 2003

The peformence tests of zinc-based desulfurization sorbents using the yellow earth as support for the hot gas clean up were carried out. The zinc-based sorbent with 25 wt％ yellow earth was prepared, and their properties such as the reaction rate, the sulfur capacity and the attrition resistance, were investigated. The reactivity tests for hot gas desulfurization was performed at middle temperatures (sulfidation/regeneration：480$^{\circ}C$/580$^{\circ}C$). During multi-cyclic desulfurization, the deactivation of zinc-based sorbent was decreased by the addition of yellow earth, and their efficiency was enhanced. The ZnO/yellow earth sorbent had high reactivity, good regenerability, long-term durability (about 19 gS/100 g sorbent for 10-cycles) and high attrition resistance (AI=19.1％). It was concluded that the peroperties of zinc-based sorbent were improved by metal oxides (Fe$_2$O$_3$, Na$_2$O, MnO$_2$, etc) in the yellow earth. From these results, it was confirmed that the desulfurization properties of zinc-based sorbents at middle temperatures could be improved by the yellow earth using as support.

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.48-54
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• 2006

In this thesis, accelerated life test (ALT) method and procedure for rubber O-ring are applied to assure specified reliability of the products at guaranteeing the life of the products. Rubber O-ring is parts that keep intensity or make machine operation smoothly on attrition portion of machine and is used to prevent that oil is leaked. Usually. Rubber O-ring used NBR that is copolymer of acrylonitrile and butadiene. this are superior oil resistance, heat resistance, durability of abrasion, cold resistance, chemical resistance etc. The accelerated life test model for rubber O-ring are developed using the relationship between stresses and life characteristics of products. Using the accelerated life test method and the acceleration life test equipment which is developed, we performed life test, collected life data and analyzed the results of tests. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test times and costs of the tests remarkably.