• Title/Summary/Keyword: Solid-gas reaction

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Synthesis of $WS_2$ Solid Lubricant and Its Application to Ball Bearing ($WS_2$고체윤활제의 합성 및 구름베어링 적용)

  • 신동우;윤대현;최인혁;김경도;정진수;정용선
    • Tribology and Lubricants
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    • v.15 no.1
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    • pp.77-82
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    • 1999
  • The processing conditions fur the synthesis of platelet W $S_2$ lubricant powder through a solid-gas reaction were optimized. The mixture of tungsten and sulfur powders were sealed in a vacuum of 10$^{-6}$ torr, prior to heat-treating at 85$0^{\circ}C$ fur 8 days. The reaction product showed a well-developed platelet W $S_2$ powder with an average size of 3.8 ${\mu}{\textrm}{m}$. The TGA/DTA analysis of the synthesized W $S_2$ powder was performed up to 120$0^{\circ}C$ at a rate of 1$0^{\circ}C$/min in flowing air (100 ${\mu}{\textrm}{m}$/min) atmosphere. The weight loss was about 6% up to 120$0^{\circ}C$ compared to the original weight. A rapid weight loss of about 5% occurred in the temperature range of 44$0^{\circ}C$ to 66$0^{\circ}C$ and an exothermic peak observed due to the transition of W $S_2$ to W $O_3$. The synthesized W $S_2$powder was coated on the commercial deep grooved ball bearing (No. 6203) to examine the effect of W $S_2$, coating layer on the noise and endurance of the ball bearing. The level of noise obtained from W $S_2$, coated-ball bearing (56 ㏈) was higher. than the value (32 ㏈) occurred in the case of greece lubrication. The endurance of the ball-bearing assembled after the coating of W $S_2$ powder onto each part increased 50 times compared to the non-coated ball-bearing..

Syngas Production Based on Co-electrolysis of CO2 and H2O in Solid Oxide Electrolysis Cell (고체 산화물 CO2-H2O 공전해 기반 합성가스 생산 기술 )

  • NAMGI JEON;SANGHYEOK LEE;SANGKUK KIM;CHIKYU AHN;JIN SOO AHN
    • Transactions of the Korean hydrogen and new energy society
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    • v.35 no.2
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    • pp.140-145
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    • 2024
  • High temperature co-electrolysis of H2O-CO2 mixtures using solid oxide cells has attracted attention as promising CO2 utilization technology for production of syngas (H2/CO), feedstock for E-fuel synthesis. For direct supply to E-fuel production such as hydrocarbon and methanol, the outlet gas ratio (H2/CO/CO2) of co-electrolysis should be controlled. In this work, current voltage characteristic test and product gas analysis were carried out under various reaction conditions which could attain proper syngas ratio.

The Effect of ZnO Content on the Performance of Spray-dried Zn-based Desulfurization Sorbent for H2 Cleanup (황화수소 정제용 아연계 분무건조 탈황제의 활성성분 함량 변경에 따른 물성 및 반응 특성)

  • Baek, Jeom In;Eom, Tae Hyoung;Lee, Joong Beom;Jegarl, Seong;Ryu, Chong Kul
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.5
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    • pp.482-490
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    • 2014
  • Gaseous sulfur compound such as $H_2S$ or COS in coal- or biomass-derived hot syngas can be purified by solid sorbents at high temperatures. In this study, we investigated the physical properties and reactivity of solid regenerable desulfurization sorbents with 37.2, 41.9, and 46.5wt% ZnO to look into the ZnO content effect. The sorbents were produced by spray-drying method to apply to a fluidized-bed process. Sulfidation and regeneration reaction were carried out using a thermogravimetric analyzer. Sorbent prepared with 46.5wt% ZnO had physical properties suitable for a fluidized-bed process applications such as spherical shape, sufficient mechanical strength and density, high porosity and surface area. It showed high sulfur sorption capacity of 10.4wt% (ZnO utilization of 57%) at reaction temperatures of 500 and $650^{\circ}C$ for sulfidation and regeneration, respectively. However, the sulfur sorption capacity and ZnO utilization were significantly reduced and dimple shape appeared when the ZnO content decreased to 37.2 and 41.9wt%. Sulfur sorption capacity and regenerability were improved as reaction temperature increased within the experimental temperatures used in this work. The reaction temperature zones of $1500{\sim}550^{\circ}C$ and $650{\sim}700^{\circ}C$ are recommended for sulfidation and regeneration, respectively, to lead best reaction performances of the ZnO-based spray-dried sorbents developed in this work.

An Experimental Guide to Predictable Fuel Cell Operations by Controlling External Gas Supply (외부 유입 가스 조절을 통한 연료전지 구동 성능 안정화)

  • Jang, Hansaem;Park, Youngeun;Lee, Jaeyoung
    • Applied Chemistry for Engineering
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    • v.29 no.5
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    • pp.626-629
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    • 2018
  • Fuel cell is one of the promising electrochemical technologies enabling power production with various fuel sources such as hydrogen, hydrocarbon and even solid carbon. However, its long-term performance is often unstable and unpredictable. In this work, we observed that gasification-driven hydrocarbons were the culprit of unpredictability. Therefore, we controlled the presence of hydrocarbons with the help of external gas supply, i.e. argon and carbon dioxide, and suggested the optimal amount of carbon dioxide required for predictable fuel cell operations. Our optimization strategy was based upon the following observations; carbon dioxide can work as both an inert gas and a fuel precursor, depending on its amount present in the reactor. When deficient, the carbon dioxide cannot fully promote the reverse Boudouard reaction that produces carbon monoxide fuel. When overly present, the carbon dioxide works as an inert gas that causes fuel loss. In addition, the excessive carbon monoxide may result in coking on the catalyst surface, leading to the decrease in the power performance.

Variation of Oxygen Nonstoichiometry of Porous $La_{0.6}Ca_{0.4}MnO_{3-{\delta}}$ SOFC-Cathode under Polarization

  • Mizusaki, Junichiro;Harita, Hideki;Mori, Naoya;Dokiya, Masayuki;Tagawa, Hiroaki
    • The Korean Journal of Ceramics
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    • v.6 no.2
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    • pp.177-182
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    • 2000
  • At the porous $La_{0.6}Ca_{0.4}MnO_{3-{\delta}}$(LCM)/YSZ electrodes of solid oxide fuel cells (SOFC), the electrochemical redox reaction of oxygen proceeds via the triple boundary (TPB) of gas/LCM/YSZ. The surface diffusion of adsorbed oxygen on LCM has been proposed as the rate determining process, assuming the gradient of oxygen chemical potential from the outer surface of porous layer to TPB. Along with the formation of this gradient, oxygen nonstoichiometry in the bulk of LCM may varies. In this paper, an electrochemical technique was described precisely to determine the variation of oxygen content in LCM of porous LCM/YSZ under polarization. It was shown that the oxygen potential in LCM layer under large cathodic polarization is much lower than that in the gas phase, being determined from the electrode potential and Nernst equation.

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Study on the Strategy of Numerical Modeling for Hybrid Combustion (하이브리드 연소의 수치 모델링 전략에 관한 연구)

  • Yoon, Changjin;Kim, Jinkon;Moon, Heejang
    • Journal of Aerospace System Engineering
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    • v.1 no.2
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    • pp.37-42
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    • 2007
  • This paper proposes a numerical modeling approach to simulate the hybrid combustion phenomena. From the physical understandings of hybrid combustion, the computational domain was separated into three regions: the solid fuel, gas phase reactive flow, and the interface between solid and fluid. Moreover, for the accurate calculation, computational grids for these regions was generated at every time step considering the instantaneous moving interface which are governed by the balance equations using thermal pyrolysis. In the domain of reactive flow, by virtue of diffusion flame structure, turbulent combustion modeling was introduced using either mixture fraction approach or mean reaction rate approach.

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Formation of Hydroxyl Radical from the Hydrogen Chemisorbed Silicon Surface by Incident Oxygen Atoms

  • Ree, Jong-Baik;Chang, Kyung-Soon;Kim, Yoo-Hang;Shin, Hyung-Kyu
    • Bulletin of the Korean Chemical Society
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    • v.24 no.7
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    • pp.986-992
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    • 2003
  • We have calculated the probability of the OH formation and energy deposit of the reaction exothermicity in the newly formed OH, particularly in its vibrational motion, in the gas-surface reaction O(g) + H(ad)/Si → OH(g) + Si on the basis of the collision-induced Eley-Rideal mechanism. The reaction probability of the OH formation increases linearly with initial excitation of the HSi vibration. The translational and vibrational motions share most of the energy when the H-Si vibration is initially in the ground state. But, when the initial excitation increases, the vibrational energy of OH rises accordingly, while the energies shared by other motions vary only slightly. The product vibrational excitation is significant and the population distribution is inverted. Flow of energy between the reaction zone and the solid has been incorporated in trajectory calculations. The amount of energy propagated into the solid is only a few percent of the available energy released in the OH formation.

A Study on the Carburization Mechanism of Iron by Solid Carbon (고체탄소(固體炭素)에 의한 철(鐵)의 침탄기구(浸炭機構)에 대(對)한 연구(硏究))

  • Kwon, Ho-Young;Cho, Tong-Rae;Kang, Sei-Sun
    • Journal of Korea Foundry Society
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    • v.8 no.3
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    • pp.287-295
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    • 1988
  • The experiment was carried out for the purpose of studying the carburization of pure iron ingot and sintered iron powder by solid carbon in the atmosphere of CO gas. The volocity of carburization was estimaed by the diffusion coefficient D calculated by carburization equation. The results obtained were as follow: 1. The higher the carburization temperature, carburization depth and carbon concentration were increased, and the melting zone which had $2.8{\sim}3.4%C$ at the $3{\sim}4mm$ from interface of carburization was formed at $1300^{\circ}C$. 2. The main carburization mechanism of pure iron ingot and the sintered iron powder were proceeded by CO gas up to $1100^{\circ}C$, solid carbon over than $1300^{\circ}C$, respectively. 3. The main carburization mechanism of pure iron ingot at $1200^{\circ}C$ was proceeded by solid carbon, and sintered iron powder was proceeded bs CO gas, however, in case the reaction time, the carburization was proceeded by solid carbon over than 5hrs. 4. The diffusion coefficient D of carbon were $0.559{\times}10^{-6}cm^2.sec^{-1}$ at $1100^{\circ}C$, $0.237{\times}10^{-6}cm^2.sec^{-1}$ at $1200^{\circ}C$, $0.087{\times}10^{-6}cm^2.sec^{-1}$ at $1300^{\circ}C$, in case of pure iron ingot carburized. 5. The diffusion coefficient D of carbon were $0.124\;cm^2.sec^{-1}$ at $1100^{\circ}C$, $0.102\;cm^2.sec^{-1}$ at $1200^{\circ}C$, $0.480\;{\times}10^{-6}cm^2.sec^{-1}$ at $1300^{\circ}C$, in the case of sintered iron carburized at the pressuring $4ton\;/\;cm^2$.

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Joining of 8 mol% YSZ Solid Electrolyte and Perovskite LaMnO3 (8 mol% YSZ 고체전해질과 페로프스카이트 $LaMnO_3$와의 접합)

  • 김명철;박순자
    • Journal of the Korean Ceramic Society
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    • v.29 no.5
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    • pp.377-382
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    • 1992
  • For the development of solid oxide fuel cell the joined interface formation between perovskite oxygen electrode and YSZ solid electrolyte is emphasized in the aspect of reducing the undisirable overpotential. The diffusion couple of LaMnO3 and YSZ was prepared by hot pressing at 130$0^{\circ}C$ in the flow of oxygen gas. The high temperature solid state reaction mechanism between LaMnO3 and YSZ is discussed on the basis of the cation composition profile through EDX analysis. The cation components in perovskite compound diffuse considerably into YSZ, while cations of YSZ diffuse little into perovskite.

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Thermal and Physicochemical Characteristics of Solid Fuel Extruded with Cattle Feedlot Manure (우분 성형 고형연료의 열 및 물리화학적 특성)

  • Lee, Gwi-Hyun
    • Journal of Biosystems Engineering
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    • v.35 no.1
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    • pp.64-68
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    • 2010
  • Cattle feedlot manure could be used effectively as the solid fuel for heating of agricultural facilities. Therefore, this study was carried out to investigate the thermal and physicochemical characteristics of solid fuel extruded with cattle feedlot manure. Calorific values of the solid fuel extruded with cattle feedlot manure, which was dried to the moisture contents of 0.0% (w.b) and 35.0% (w.b,) were 14,906 kJ/kg and 11,797 kJ/kg, respectively. Calorific value of extruded solid fuel was linearly decreased with the increase of moisture content. The first, second, and third reaction point during thermal pyrolysis of solid fuels extruded with cattle feedlot manure was investigated as $108.1^{\circ}C$, $312.2^{\circ}C$, and $459.4^{\circ}C$, respectively. The maximum reaction point was presented at the temperature of $312.2^{\circ}C$. Weight loss of extruded cattle feedlot manure during thermal pyrolysis until $600^{\circ}C$ was reached to about 60%. Volume decrease of initial extruded cattle feedlot manure was 61% during drying for the use as solid fuel. Maximum strength of extruded cattle feedlot manure, which was dried as the moisture content of 10% (w.b.) was 41,9150 N/$m^2$. Ignition gas analysis of extruded cattle feedlot manure presented that it has small amount of $NO_x$ and $SO_x$. It was shown that dried cattle feedlot manure had main components of C and O including small amount of Mg, Si, and Ca.