Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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Design and Optimization of Pilot-Scale Bunsen Process in Sulfur-Iodine (SI) Cycle for Hydrogen Production

수소 생산을 위한 Sulfur-Iodine Cycle 분젠반응의 Pilot-Scale 공정 모델 개발 및 공정 최적화

  • Park, Junkyu (Department of Environmental Science and Engineering College of Engineering, Kyung Hee University) ;
  • Nam, KiJeon (Department of Environmental Science and Engineering College of Engineering, Kyung Hee University) ;
  • Heo, SungKu (Department of Environmental Science and Engineering College of Engineering, Kyung Hee University) ;
  • Lee, Jonggyu (Research Institute of Industrial Science & Technology) ;
  • Lee, In-Beum (Department of Chemical Engineering, Pohang University of Science and Technology) ;
  • Yoo, ChangKyoo (Department of Environmental Science and Engineering College of Engineering, Kyung Hee University)
  • 박준규 (경희대학교 공과대학 환경응용과학과) ;
  • 남기전 (경희대학교 공과대학 환경응용과학과) ;
  • 허성구 (경희대학교 공과대학 환경응용과학과) ;
  • 이종규 (포항산업과학연구원) ;
  • 이인범 (포항공과대학교 화학공학과) ;
  • 유창규 (경희대학교 공과대학 환경응용과학과)
  • Received : 2020.02.05
  • Accepted : 2020.03.06
  • Published : 2020.05.01
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Abstract

Simulation study and validation on 50 L/hr pilot-scale Bunsen process was carried out in order to investigate thermodynamics parameters, suitable reactor type, separator configuration, and the optimal conditions of reactors and separation. Sulfur-Iodine is thermochemical process using iodine and sulfur compounds for producing hydrogen from decomposition of water as net reaction. Understanding in phase separation and reaction of Bunsen Process is crucial since Bunsen Process acts as an intermediate process among three reactions. Electrolyte Non-Random Two-Liquid model is implemented in simulation as thermodynamic model. The simulation results are validated with the thermodynamic parameters and the 50 L/hr pilot-scale experimental data. The SO2 conversions of PFR and CSTR were compared as varying the temperature and reactor volume in order to investigate suitable type of reactor. Impurities in H2SO4 phase and HIX phase were investigated for 3-phase separator (vapor-liquid-liquid) and two 2-phase separators (vapor-liquid & liquid-liquid) in order to select separation configuration with better performance. The process optimization on reactor and phase separator is carried out to find the operating conditions and feed conditions that can reach the maximum SO2 conversion and the minimum H2SO4 impurities in HIX phase. For reactor optimization, the maximum 98% SO2 conversion was obtained with fixed iodine and water inlet flow rate when the diameter and length of PFR reactor are 0.20 m and 7.6m. Inlet water and iodine flow rate is reduced by 17% and 22% to reach the maximum 10% SO2 conversion with fixed temperature and PFR size (diameter: 3/8", length:3 m). When temperature (121℃) and PFR size (diameter: 0.2, length:7.6 m) are applied to the feed composition optimization, inlet water and iodine flow rate is reduced by 17% and 22% to reach the maximum 10% SO2 conversion.

Sulfur-Iodine cycle (SI cycle)은 요오드와 황을 첨가하여 최종적으로 물을 열화학적으로 분해하여 산소와 수소를 생산하는 공정으로 황산분해, 요오드화 수소 분해, 분젠반응 등 세가지 반응들로 이루어져 있다. 분젠 반응은 두가지 공정 중간에 존재하므로 두 반응에 필요한 화학물을 조달하는 역할로 이에 대한 상분리 및 반응기에 대한 분석이 중요하다. 본 연구에서는 50 L/hr 수소를 생산하는 pilot scale의 Sulfur-Iodine Cycle 중 분젠 공정에 대한 모사, 민감도 분석, 민감도 분석을 토대로한 각각 상분리기와 분젠 반응기에 대한 최적 조건을 제시하였다. 열역학 물성치의 계산을 위해 Electrolyte Non-Random Two Liquid (ELECNRTL) model 사용하였다. 모델에 대한 신뢰도 확보를 위해서 실제 pilot scale의 공정 데이터와 검증을 수행하였다. 반응기의 종류를 선정하기 위해 Continuous Stirred Tank Reactor (CSTR)과 Plug Flow Reactor (PFR) 동일한 온도 및 부피 변화에서 SO2 전환율을 비교하였다. 상분리기 선정을 위해 3상 분리 시스템(기체-액체-액체)과 액체-기체 분리 후 액체-액체 구조에서 H2SO4 상과 HIX 상에서의 불순물들을 비교하였다. PFR에서 온도, 지름, 길이를 결정 변수로 SO2 전환율을 최대화 하기 위한 최적화를 수행하였는데, 온도 121 ℃와 PFR의 지름이 0.20 m 및 길이 7.6 m 일 때 SO2 전환율이 98% 최적 결과임을 확인하였다. 기존 pilot scale과 동일한 운전 조건 하에 PFR의 지름 3/8 inch, 길이 3.0 m, 120 ℃ 일 때 인입 몰량인 I2 및 H2O를 결정 변수로 SO2 전환율에 대한 최적화를 수행하였을 때, SO2 전환율이 10% 일때 H2O 및 I2 의 인입 몰량은 각각 17%와 22%로 감소하였다. 앞선 조업 조건 최적화 조건 (121 ℃, 지름 0.20 m, 길이: 7.6 m) 경우에는 SO2 전환율이 98% 일 때 H2O가 1% 그리고 I2가 7% 감소하였다. 상분리기에서 HIX 상내 H2SO4 최소화하는 목적함수에서 그에 상응하는 온도, I2와 H2O를 결정 변수로 설정하였을 때, H2O 몰량이 기존공정보다 17% 감소하고 I2 몰량이 24% 감소하였을 때 최소 불순물이 생성하였다.

Keywords

References

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