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다공성 니켈 연료 전극 내부에서 탄화수소의 열분해를 통한 직접 탄소 연료 전지의 연료공급
이학규(Hakgyu Yi),이성국(Chengguo Li),타헤레 잘랄라바디(Tahereh Jalalabadi),이동근(Donggeun Lee) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.6
본 연구에서는 직접 탄소 연료전지(DCFC)에서 세 종류의 탄화수소(메탄, 에탄, 프로판) 열분해를 이용하여 다공성 니켈 연료극에 탄소를 직접 생성시켜 연료극과 연료간의 물리적 접촉을 향상시켰다. 전자현미경으로 각각의 탄화수소로부터 생성된 탄소 입자들이 탄소 수가 증가함에 따라 각각 탄소구형체(CS), 탄소나노튜브(CNT), 탄소나노섬유(CNF)임을 확인하였다. 그리고 탄소 샘플들의 결정성을 알아보기 위해 라만 산란 분석을 수행하였고, 탄화수소의 탄소 수가 증가할수록 생성된 탄소의 결정성이 떨어지고 더 유연하였다. 동일한 질량의 탄소로 채워진 연료극의 DCFC 성능을 700 ℃ 에서 측정하였고, CNT와 CNF 가 CS 보다 반응성이 좋아 각각 148%, 210% 높은 전력밀도를 보였다. 이는 결정성이 떨어지는 CNT 와 CNF 의 낮은 전하전달저항에 의한 것으로 사료된다. This study offers a novel method for improving the physical contact between the anode and fuel in a direct carbon fuel cell (DCFC): a direct generation of carbon in a porous Ni anode through the thermal decomposition of gaseous hydrocarbons. Three kinds of alkane hydrocarbons with different carbon numbers (CH4, C2H6, and C3H8) are tested. From electron microscope observations of the carbon particles generated from each hydrocarbon, we confirm that more carbon spheres (CS), carbon nanotubes (CNT), and carbon nanofibers (CNF) were identified with increasing carbon number. Raman scattering results revealed that the carbon samples became less crystalline and more flexible with increasing carbon number. DCFC performance was measured at 700 °C with the anode fueled by the same mass of each carbon sample. One-dimensional carbon fuels of CNT and CNF more actively produced and had power densities 148 and 210 times higher than that of the CS, respectively. This difference is partly attributed to the findings that the less-crystalline CNT and CNF have much lower charge transfer resistances than the CS.
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Li, Chengguo,Yi, Hakgyu,Lee, Donggeun Elsevier 2016 Journal of Power Sources Vol.309 No.-
<P><B>Abstract</B></P> <P>In this paper, we propose a novel idea that might allow resolution of the two biggest challenges that hinder practical use of direct carbon fuel cells (DCFC). This work involved 1) the use of three types of porous Ni anode with different pore sizes, 2) size matching between the anode pores and solid fuel particles in a molten-carbonate (MC) slurry, and 3) provision of a continuous supply of fuel-MC slurry through the porous Ni anode. As a result, larger numbers of smaller pores in the anode were preferred for extending the triple phase boundary (TPB), as long as the fuel particles were sufficiently small to have full access to the inner pore spaces of the anode. For example, the maximal power density achieved in the case of optimal size matching, reached 645 mW cm<SUP>−2</SUP>, which is 14-times greater than that for the case of poorest size-matching and 64-times larger than that for a non-porous anode, and lasted for more than 20 h. After 20 h of steady operation at a fixed current density (700 mA cm<SUP>−2</SUP>), the electric potential slightly decreased due to partial consumption of the fuel. The cell performance readily recovered after restarting the supply of MC-fuel slurry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A potentially continuous fuel supply with increasing fuel-anode contacts in a DCFC. </LI> <LI> Of importance was the size match between the anode pores and fuel particles. </LI> <LI> Maximal power density under the optimal size-matching reached 645 mW cm<SUP>−2</SUP>. </LI> <LI> More than 20-h steady operation was achieved at a current density of 700 mA cm<SUP>−2</SUP>. </LI> </UL> </P>
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A TGA study of CO 2 gasification reaction of various types of coal and biomass
Tahereh Jalalabadi,Chengguo Li,Hakgyu Yi,Donggeun Lee 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7
The CO 2 gasification kinetics of various carbonaceous samples of high- and low-rank coal and a biomass were determined under CO 2flow with increasing temperature in a Thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy (FTIR). We utilized four different types of fuels and their chars with significant differences in their physico-chemical properties that are being most widely used in Korea. As a result, fuels with larger surface area and more catalytic components in ash were preferred for increasing the intrinsic reactivity of CO 2 gasification particularly for low-rank coals and biomass, respectively. It was postulated that the catalytic effect of ash components could compensate for the lack of active sites in the biomass samples. From the practical point of view, the utilization of the low-rank coal with the porous char structure with blending the biomass is recommended for a remarkable increase of the gasification rate.
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