Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Improved Performance of Direct Carbon Fuel Cell by Catalytic Gasification of Ash-free Coal

무회분탄 연료의 촉매 가스화에 의한 직접탄소연료전지의 성능 향상

  • Jin, Sunmi (Graduate School of Green Energy Technology, Chungnam National University) ;
  • Yoo, Jiho (Clean Fuel Center, Korea Institute of Energy Research) ;
  • Rhee, Young Woo (Graduate School of Green Energy Technology, Chungnam National University) ;
  • Choi, Hokyung (Clean Fuel Center, Korea Institute of Energy Research) ;
  • Lim, Jeonghwan (Clean Fuel Center, Korea Institute of Energy Research) ;
  • Lee, Sihyun (Clean Fuel Center, Korea Institute of Energy Research)
  • 진선미 (충남대학교 녹색에너지기술전문대학원) ;
  • 유지호 (한국에너지기술연구원 청정연료연구단) ;
  • 이영우 (충남대학교 녹색에너지기술전문대학원) ;
  • 최호경 (한국에너지기술연구원 청정연료연구단) ;
  • 임정환 (한국에너지기술연구원 청정연료연구단) ;
  • 이시훈 (한국에너지기술연구원 청정연료연구단)
  • Received : 2012.09.03
  • Accepted : 2012.09.27
  • Published : 2012.12.31
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Abstract

Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

탄소가 다량 포함된 석탄을 직접탄소연료전지(direct carbon fuel cell, DCFC) 연료로 사용 시 무기물인 회분은 반응 후 남아 접촉계면을 물리적으로 덮어 연료전지 성능을 저하시킨다. 본 연구에서는 회분이 제거된 무회분탄(ash-free coal, AFC)을 제조하고 이를 증기 가스화 촉매와 함께 도입한 후 DCFC 연료로써의 특성을 알아보았다. 고체산화물 연료전지(solid oxide fuel cell, SOFC) 기반의 DCFC에 무회분탄과 가스화 촉매인 탄산칼륨을 연료로 도입한 경우와 무회분탄만을 도입한 경우를 비교하였다. 열분해 반응 조건에서는 두 경우의 전력밀도 차이가 크지 않으나, 증기 가스화 조건에서는 촉매가 도입된 무회분탄이 상대적으로 높은 전력밀도 상승을 나타냈다. 이것은 증기 가스화 반응이 촉매에 의해 활성화되어 더 많은 양의 수소가 생산되었기 때문이다. 촉매 유무에 따른 수소 생성양의 차이를 가스크로마토그래피(gas chromatography, GC)로 정량 분석한 결과, 탄산칼륨첨가는 수소 생산 속도를 증가시킴을 확인하였다. 시간 경과에 따른 전력밀도의 감소는 촉매가 첨가된 연료에서 더 빠르게 나타났는데, 이는 촉매의 칼륨성분이 전해질과 반응하여 이성질 화합물을 형성하기 때문으로 생각된다. 얇은 두께의 전해질(30 ${\mu}m$) 도입에 의해 전력밀도가 향상되었다.

Keywords

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