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Thermodynamic analysis and process optimization of a natural gas liquid recovery unit based on the Joule – Thomson process

Nabati Shoghl, S ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.1016/j.jngse.2021.104265
  3. Publisher: Elsevier B.V , 2021
  4. Abstract:
  5. A thermodynamic analysis was conducted on the Joule-Thomson (JT) process to improve separation performance and exergy efficiency of a three-stage throttling process in a natural gas liquid (NGL) recovery plant. The JT inversion curve (JTIC) along with the phase envelope diagram (PED) were used to study phase transition during the throttling process. Three different objective functions—maximization of NGL recovery rate, improvement of cooling performance, and minimization of the exergy destruction—were investigated in this study to increase the NGL recovery rate with minimum energy consumption. It was observed that the improvement of cooling performance did not always increase the NGL recovery rate. Therefore, the cooling performance is not a suitable objective function for optimizing the JT process. To find the optimal operating condition seven different intermediate pressure ratios were defined. Then, the influence of the number of stages and intermediate pressure ratio on these objective functions was studied. The results showed that upon changing the pressure gradient from 35 to 5 bar, the exergy efficiency of JT valve 2 and JT valve 3 improved from 91.6 to 98.9% and 91–98.4%, respectively. In addition, when the pressure gradient in the JT valve 2 changed from 5 bar to 35 bar, the NGL recovery rate at this stage increased from 1.54 to 21.79 kmol/h. The results indicated that the optimum operational condition was obtained at the intermediate pressure ratio. © 2021 Elsevier B.V
  6. Keywords:
  7. Cooling ; Energy utilization ; Exergy ; Natural gas ; Optimization ; Phase diagrams ; Phase transitions ; Pressure gradient ; Recovery ; ASPEN PLUS ; Cooling performance ; Intermediate pressures ; Joule-Thomson ; Natural gas liquid recoveries ; Objective functions ; Phase envelope ; Pressure ratio ; Recovery rate ; Soave-redlich-kwong ; Thermoanalysis
  8. Source: Journal of Natural Gas Science and Engineering ; Volume 96 , 2021 ; 18755100 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S1875510021004637