Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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Re-carbonation of Calcined Limestone Under Oxy-Circulating Fluidized Bed Combustion Conditions

순산소 순환유동층 연소 조건에서 생석회의 재탄산화 반응

  • Kim, Ye Bin (Department of Mineral Resources and Energy Engineering, Chonbuk National University) ;
  • Gwak, You Ra (Department of Mineral Resources and Energy Engineering, Chonbuk National University) ;
  • Keel, Sang In (Environment Systems Research Division, Korea Institute of Machinery and Materials (KIMM)) ;
  • Yun, Jin Han (Environment Systems Research Division, Korea Institute of Machinery and Materials (KIMM)) ;
  • Lee, See Hoon (Department of Mineral Resources and Energy Engineering, Chonbuk National University)
  • 김예빈 (전북대학교 자원에너지공학과) ;
  • 곽유라 (전북대학교 자원에너지공학과) ;
  • 길상인 (한국기계연구원 환경기계연구실) ;
  • 윤진한 (한국기계연구원 환경기계연구실) ;
  • 이시훈 (전북대학교 자원에너지공학과)
  • Received : 2018.07.27
  • Accepted : 2018.10.04
  • Published : 2018.12.01
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Abstract

In order to investigate the re-carbonation behaviors of limestones in an oxy-circulating fluidized bed combustor (Oxy-CFBC), the re-carbonation characteristics of domestic 4 different limestone samples were analyzed in a thermogravimetric analyzer (TGA-N1000) with the higher concentration of $CO_2$. Effect of reaction temperature ($600{\sim}900^{\circ}C$) and $CaCO_3$ content (77~95%) of limestones were determined and the mass change of the CaO was observed. Under the temperature of $800^{\circ}C$, the conversion rate increased with increasing reaction temperature. However, the conversion rate decreased with increasing reaction temperature over $800^{\circ}C$. In the case of $CaCO_3$ content, the conversion was remarkably different at $870^{\circ}C$. In addition, reaction rate equations for simulating the re-carbonation of limestone by using gas solid reaction models were proposed in this study.

순산소 순환유동층 보일러에서 탈황을 위해 이용되는 석회석의 재탄산화 거동을 분석하기 위하여, 상용 순환유동층 보일러에서 이용되는 석회석 4종의 재탄산화 반응 특성을 열중량분석기(TGA-N1000)에서 고농도의 $CO_2$ 가스를 이용하여 분석하였다. 생석회의 재탄산화 반응은 반응온도($600{\sim}900^{\circ}C$), 석회석의 $CaCO_3$ 함량(77~95%) 등의 조건에 따른 질량 변화를 통해 고찰되었다. $600{\sim}800^{\circ}C$의 온도 영역에서는 반응 온도가 증가함에 따라 전환율이 증가하였고, $850{\sim}900^{\circ}C$ 에서는 반응 온도가 증가함에 따라 전환율이 감소하는 경향이 발견되었다. $CaCO_3$ 함량의 경우, $870^{\circ}C$의 반응온도에서 뚜렷한 전환율의 차이를 보였다. 또한 기-고체반응속도 모델들에 적용하여 석회석의 재탄산화 반응을 모사하는 반응속도식을 제시하였다.

Keywords

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Fig. 1. Thermodynamic equilibrium curve of CaCO3 calcination.

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Fig. 2. Conversion of re-carbonation with variation of time at different temperature of four limestones (a) A (b) B (c) C and (d) D.

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Fig. 3. SEM images (a) CaO and (b) CaCO3 from limestones A.

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Fig. 4. Reaction temperature versus final conversion.

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Fig. 5. Reactivity of limestone A through (a) SCM and (b) VRM.

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Fig. 6. Arrhenius plots of four limestones (a) A, (b) B, (c) C and (d) D.

Table 1. Chemical analysis of the limestones

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Table 2. Frequency Factor and Activation Energy

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Table 3. Rate equation of re-carbonation

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