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Design and Optimization of Helium Extraction and Liquefaction Cycle from Natural Gas by Direct Method

Ardeshir Larijani, Morteza | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54409 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Afshin, Hossein
  7. Abstract:
  8. Helium is known as a strategic material due to its unique properties and applications in the development of advanced industries. Currently, natural gas is the only source from which helium can be produced economically. The United States, Qatar, Algeria, and Russia have the largest share of helium production, respectively. In this research, the process of helium extraction from natural gas and its liquefaction, independent of LNG production based on helium in South Pars gas of Iran, which is the largest helium reservoir in the world, were designed and simulated.In the helium liquefaction section, the speed and accuracy of the process simulation were improved by developing a home code based on the MBWR state equation and using the artificial intelligence neural network technique. Increasing the number of cooling steps from 2 to 4, increased the cold box exergy efficiency from 21% to 36%. The outlet pressure of the optimized compressor for the cycles with 2 to 4 expanders was about 20.55, 16.1 and 13.87 bar, respectively. According to the results, increasing the number of cooling steps to more than 4 steps did not have a significant effect on the performance of liquefaction cycles.The use of nitrogen for pre-cooling in the cold box reduced power consumption by 31% and 24%, and also increased IRR by 10.9% and 7.2% in parallel and series two-expander cycles with a capacity of 40 Lit / h, respectively.In the extraction unit, two distillation columns were used to separate the hydrocarbons and nitrogen in natural gas to achieve a final flow with 80% helium mole fraction. By implementing sensitivity analysis on the distillation column performance and determining the main performance parameters of the two distillation columns, 81 scenarios were selected for implementation in the integrated production process.In order to optimize the lateral cycles, 5 out of 81 scenarios obtained from the sensitivity analysis of distillation columns were selected for the final comparison of power consumption. The total power consumption, specific power consumption, and IRR in the scenario optimized by the particle mass algorithm were 9847.45 kW, 466.93 kW / kg, and 33.13%, respectively. Comparison of the optimized scenario and another scenario of the integrated process showed that the optimization of the crude gas helium production process reduced the power consumption by 11.8 MW and the IRR value by 2.11 times.In the code developed for the distillation column simulation, the performance conditions of the distillation column were improved by using the E-PPR78 state equation to predict the thermodynamic properties and improved theta algorithm for solving the column equations. In the improved condition, resulting from simultaneous changes in pressure, feed tray, and reflux coefficient compared to the improved condition based on increasing reflux coefficient, the molar fraction of methane in the upstream of the column and the energy consumption required by the column were reduced by 5% and 54%, respectively
  9. Keywords:
  10. Helium Gas ; Cryogenic ; Distillation Column ; Optimization ; Process Engineering ; Helium Extraction from Natural Gas ; Liquefaction Process

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