Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Analysis of Predicted Reduction Characteristics of Ash Deposition Using Kaolin as a Additive During Pulverized Biomass Combustion and Co-firing with Coal

미분탄 연소 시스템에 바이오매스 혼소시 카올린 첨가제 적용에 따른 회 점착 저감 특성 예측 연구

  • Jiseon Park (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Jaewook Lee (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Yongwoon Lee (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Youngjae Lee (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Won Yang (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Taeyoung Chae (Carbon Neutral Technology R&D Department, Korea Institute of Industrial Technology) ;
  • Jaekwan Kim (KEPCO Research Institute)
  • 박지선 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 이재욱 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 이용운 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 이영재 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 양원 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 채태영 (한국생산기술연구원 탄소중립산업기술연구부문) ;
  • 김재관 (한전 전력연구원)
  • Received : 2023.06.30
  • Accepted : 2023.08.17
  • Published : 2023.09.30
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Abstract

Biomass has been used to secure renewable energy certificates (REC) in domestic and overseas coal-fired power plants. In recent years, biofuel has been diversified from traditional wood pellets to non-woody biomass. Non-woody biomass has a higher content of alkaline metals such as K and Na than wood-based biomass, resulting in a lower melting point and an increase in slagging on boiler tubes, which reduces boiler efficiency. This study analyzed the effect of kaolin, an additive commonly used to increase melting points, on biomass co-firing to coal through thermochemical equilibrium calculations. In a previous experiment on biomass co-firing to coal conducted at 80 kWth, it was interpreted that the use of kaolin actually increased the amount of fouling. In this study, analysis showed that when kaolin was added, aluminosilicate compounds were generated due to Al2O3, which is abundant in coal, and mullite was formed. Thus, it was confirmed that the amount of slag increased when more kaolin was used. Further analysis was conducted by increasing the biomass co-firing rate from 0% to 100% at 10% intervals, and the results showed non-linear liquid slag generation. As a result, it was found that the least amount of liquid slag was generated when the biomass co-firing rate was between 50 and 60%. The phase diagram analysis showed that high melting point compounds such as leucite and feldspar were most abundantly generated under these conditions.

국내외 석탄화력발전소에서 REC(Renewable energy certificate) 확보를 위해 혼소되고 있는 바이오매스는 기존의 목질계 바이오매스인 우드 펠릿에서부터 최근 들어 초본계 바이오매스로의 확대가 진행되고 있다. 초본계 바이오매스의 경우 목질계 바이오매스에 비해 K, Na 등의 알칼리계 금속 함량이 더 높아 회융점이 더 낮고, 이 때문에 보일러 튜브에의 회 점착을 늘려 보일러의 효율을 떨어뜨리는 원인이 되고 있다. 본 연구에서는 초본계 바이오매스 연소시 회 융점을 높여 회 점착을 감소시키기 위해 많이 사용되고 있는 첨가제인 카올린(kaolin)이 석탄-바이오매스 혼소시 미치는 영향을 열화학 평형 계산을 통해 분석하고자 하였다. 이전 연구에서 수행된 80 kWth 급 미분탄 - 바이오매스 혼소 실험에서 카올린을 사용하는 경우 오히려 회 점착량이 늘어나는 원인을 해석을 통해 분석하였으며, 해석을 수행한 결과 석탄에 많이 포함되어 있는 Al2O3 때문에, Al-Si 계열 첨가제인 카올린 투입시 aluminosilicate 화합물의 생성이 촉진되어 용융점이 낮은 mullite가 많이 형성, 카올린을 더 사용할수록 슬래그 생성이 증가하는 것을 확인하였다. 추가적으로 바이오매스 혼소율을 0~100%까지 10% 간격으로 증가시켜가면서 해석을 수행하였으며, 그 결과 비선형적인 액상 슬래그 생성 특성을 확인하였다. 결과적으로는 바이오매스 혼소율 50~60% 조건일 때 가장 적은 량의 액상 슬래그가 생성됨을 파악하였다. phase diagram을 분석한 결과, 고용융점 화합물(leucite, feldspar)이 해당 조건에서 가장 많이 생성되는 것을 확인하였다.

Keywords

Acknowledgement

본 연구는 한전 전력연구원의 "석탄화력 시스템 유연운전을 위한 연소 및 배가스 처리설비 최적화 기술 개발(R20GA10)"과제의 지원을 받아 수행되었습니다.

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