Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
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Thermodynamic Analysis on Hybrid Turbo Expander - Heat Pump System for Natural Gas Pressure Regulation

히트펌프를 적용한 터보팽창기 천연가스 정압기지의 열역학적 분석

  • Sung, Taehong (School of Mechanical Engineering, Pusan National University) ;
  • Kim, Kyoung Hoon (School of Mechanical Engineering, Kumoh National Institute of Technology) ;
  • Han, Sangjo (Dept. of Mechanical & Automotive Engineering, Seoul National University of Science & Technology) ;
  • Kim, Kyung Chun (School of Mechanical Engineering, Pusan National University)
  • 성태홍 (부산대학교 기계공학부) ;
  • 김경훈 (금오공과대학교 기계공학부) ;
  • 한상조 (서울과학기술대학교 기계자동차공학과) ;
  • 김경천 (부산대학교 기계공학부)
  • Received : 2014.05.12
  • Accepted : 2014.08.01
  • Published : 2014.08.31
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Abstract

In natural gas distribution system, gas pressure is regulated correspond to requirement using throttle valve which is releasing huge pressure energy as useless form. The waste pressure can be recovered by using turbo machinery devices such as a turbo expander. In this process, excessive temperature drop occurs due to Joule-Thompson effect during the expansion process. Installing natural gas boiler before or after the turbo expander prevents temperature drop. Fuel cell or gas engine hybrid system further improve the efficiency, but 1~2% of total transporting natural gas is used for operating the hybrid system. In this study, a heat pump system is proposed as a preheating device which can be operated without using transporting natural gas. Thermodynamic analysis on evaporating and condensing temperatures and refrigerants is conducted. Results show that R717 is proper refrigerant for the hybrid system with high COP and low turbine work within the defined operating conditions. In domestic usage in Korea, the heat pump system has more economic feasibility owing to natural gas being imported with a high price of LNG form.

상업용 천연가스 배급 시스템에서 천연가스의 공급압력은 압력조절밸브를 사용하여 제어하며 이때 막대한 압력에너지가 낭비된다. 이러한 폐압에너지는 터보 팽창기와 같은 터보기계를 사용하여 회수할 수 있으나 팽창과정에서 발생하는 Joule-Thompson 효과에 따라서 큰 온도강하가 발생한다. 터보 팽창기 전단 또는 후단에 보일러를 설치하여 영하의 온도를 방지할 수 있으며 또한 보일러를 대체하여 연료전지나 가스엔진의 폐열을 이용하여 천연가스를 예열할 수도 있으나 하이브리드 시스템의 구동을 위해 운영규모에 따라 일정량을 소모해야 한다. 이 연구에서는 천연가스가 가지고 있는 압력에너지를 활용하여 천연가스의 소모 없이 터보 팽창기와 연결된 히트펌프를 구동하여 천연가스를 예열하는 시스템을 제안하고 증발온도, 응축온도 및 작동유체의 변화에 따른 시스템의 열역학적 특성을 분석하였다. R717 냉매가 예상 작동범위 내에서 가장 높은 COP와 가장 낮은 압축일을 나타내 제안된 하이브리드 시스템에 적합함을 확인하였다. 보일러시스템과의 경제성 분석을 통해 천연가스를 LNG 형태로 수입하고 있는 국내의 경우 히트펌프 하이브리드 시스템이 경쟁력 있음을 확인하였다.

Keywords

References

  1. Pozivil, J., "Use of expansion turbines in natural gas pressure reduction stations." Acta Montanistica Slovaca, 3(9), 258-260, (2004)
  2. Hedman, B. A., "Waste energy recovery opportunities for interstate natural gas pipelines." Interstate Natural Gas Association of America, (2008)
  3. Rahman, M. M., "Power generation from pressure reduction in the natural gas supply chain in Bangladesh", Transaction of the Mech. Eng. Div., The Institution of Engineers, Bangladesh, 41(2), 89-95, (2010)
  4. Ardali, E. K., and Heybatian, E., "Energy Regenaration in Natural Gas Pressure Reduction Stations by Use of Gas Turbo-Expander; Evaluation of Available Potential in Iran", In proceedings 24th world gas conference, 5-9, (2009)
  5. Howard, C., Oosthuizen, P., and Peppley, B., "An investigation of the performance of a hybrid turboexpander-fuel cell system for power recovery at natural gas pressure reduction stations", Applied Thermal Engineering, 31(13), 2165-2170, (2011) https://doi.org/10.1016/j.applthermaleng.2011.04.023
  6. Sung, T. and Kim, K. C., "Thermodynamic Analysis on Hybrid Molten Carbonate Fuel Cell - Turbo Expander System for Natural Gas Pressure Regulation", KIGAS, 18(2), 28-34, (2014) https://doi.org/10.7842/kigas.2014.18.2.28
  7. Kostowski, W. J., and Uson, S., "Thermoeconomic assessment of a natural gas expansion system integrated with a co-generation unit", Applied Energy, 101, 58-66, (2013) https://doi.org/10.1016/j.apenergy.2012.04.002
  8. Bisio, G., "Thermodynamic analysis of the use of pressure exergy of natural gas", Energy, 20(2), 161-167, (1995) https://doi.org/10.1016/0360-5442(94)00074-D
  9. Ha, J. M., Hong, S., You, H. S. and Kim, K. C., "Turbo Expander Power Generation Using Pressure Drop in Natural Gas Pipeline", KIGAS, 16(3), 1-7, (2012) https://doi.org/10.7842/kigas.2012.16.3.001
  10. Maddaloni, J. D., and Rowe, A. M., "Natural gas exergy recovery powering distributed hydrogen production", International journal of hydrogen energy, 32(5), 557-566, (2007) https://doi.org/10.1016/j.ijhydene.2006.06.039
  11. Ha, J. M., Hong, S. and Kim, K. C., "Thermodynamic analysis on the feasibility of turbo expander power generation using natural gas waste pressure", KIGAS, 6(6), 136-142, (2012) https://doi.org/10.7842/kigas.2012.16.6.136
  12. Lemmon, E. W., Huber, M. L., and McLinden, M. O., "NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP. 9.0", (2010)
  13. British Standard BS EN 12186:2000 Gas supply systems. Gas pressure regulating stations for transmission and distribution. Functional requirements.

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