Applied Chemistry for Engineering (공업화학)

The Korean Society of Industrial and Engineering Chemistry (한국공업화학회)
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Optimization of the Organic Rankine Cycle Condition for Effective Utilization of Multiple Waste Heat Sources in Biogas-to-Hydrogen Process

바이오가스 수소화 공정 내 다중 폐열원의 효과적인 활용을 위한 유기랭킨사이클 조건 최적화

  • Yejun Park (Energy AI & Computational Science Laboratory, Korea Institute of Energy Research) ;
  • Dabin Seo (Energy AI & Computational Science Laboratory, Korea Institute of Energy Research) ;
  • Young-Hwan Chu (Energy AI & Computational Science Laboratory, Korea Institute of Energy Research)
  • 박예준 (한국에너지기술연구원 에너지AI.계산과학실) ;
  • 서다빈 (한국에너지기술연구원 에너지AI.계산과학실) ;
  • 주영환 (한국에너지기술연구원 에너지AI.계산과학실)
  • Received : 2024.12.03
  • Accepted : 2025.01.12
  • Published : 2025.02.10
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Abstract

The biogas-to-hydrogen process produces hydrogen through the reforming of methane gas generated through anaerobic digestion of organic waste materials, and there are unit processes that use a lot of electricity, such as gas compression in the process requiring further reduction of the electric energy used in the process itself or generation of additional power by utilizing waste heat. In this study, three waste heat sources in the biogas-to-hydrogen process were assigned, and an organic Rankine cycle (ORC) was installed to maximize the power production by optimizing the system pressure and the amount of working fluid sent to each waste heat source. The simulation study and techno-economic analysis showed that 30 bar was determined to be the optimal system pressure when installing an ORC system using R600a as the working fluid, and the optimal distribution ratio of the working fluid to the three waste heat sources was 36.9:37.2:25.9, which resulted in the highest system efficiency of 15.2%. The economic feasibility of the ORC was also demonstrated with a payback period of 5.5 years when applying these optimal operating conditions at a 3 MT/h biogas processing scale.

바이오가스 수소화 공정은 유기성 폐자원의 혐기성 소화를 통해 발생하는 메탄가스의 개질을 통해 수소를 생산하는 공정으로서, 공정 내 가스 압축 등과 같이 전기에너지 사용량이 많은 단위공정이 존재하여 공정 자체적으로 전기에너지 사용량을 더 절감하거나 폐열 등을 활용해 전력을 추가로 생산해야 할 필요성이 존재한다. 이에 본 연구에서는 바이오가스 수소화 공정 내 세 곳의 폐열원을 지정하고 하나의 유기랭킨사이클(ORC)을 설치하되 시스템 압력과 각 폐열원에 보내는 작동 유체의 양을 최적화함으로써 자체 전력 생산을 극대화하고자 하였다. 시뮬레이션 스터디 및 경제성 분석 결과, R600a를 작동 유체로 사용하는 ORC 시스템을 설치할 경우 30 bar가 최적의 시스템 압력으로 결정되었고 세 곳의 폐열원으로 보내는 작동 유체의 최적 배분 비율을 36.9 : 37.2 : 25.9로 지정할 때 ORC의 시스템 효율이 15.2%로 가장 높게 나타남을 확인하였다. 또한 바이오가스 3 MT/h 처리 규모에서 해당 최적 운전 조건을 적용했을 때, 투자회수기간이 5.5년으로 산정되어 경제성이 입증되었다.

Keywords

Acknowledgement

본 연구는 한국에너지기술연구원 기본사업(C4-2450)과 한국에너지기술평가원 에너지저감 공정촉매 재자원화 기술개발사업(No. 20228A10100020)의 지원으로 수행되었습니다.

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