Optimalisering av DMR prosesser for flytendegjøring av naturgass
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Four DMR processes alternatives were modeled and optimized in Aspen HYSYS in order to evaluate their efficiency. The alternatives studied are processes developed by Shell, Air Products and Chemicals, Inc (APCI), Axens-IFP and Tealarc. The objective of the project was to test the Hyprotech SQP optimizer in Aspen HYSYS and report on the its performance, while comparing the energy requirements and the configuration complexity for the proposed processes. The mixed refrigerants composition, as well as their inlet pressures were the main variables in the optimization problem formulation. The degree of meeting the constraints of the process paid a crucial role when analyzing the performance of the optimizer. Exergy analysis was conducted in order to find the exergy loss and the exergy efficiency of the proposed solutions. The optimization results showed that the Shell alternative had the lowest specific power consumption of 214.8 kWh⁄ton , while the Tealarc alternative had the highest exergy efficiency of 56.8%. However, from the complexity point of view, Shell alternative was a better solution for the offshore floating vessels due to its lower equipment size. Further work should be conducted to improve the optimizer performance, by developing a new nonlinear programming method that would solve the optimization problem.