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{"@context":"https://schema.org","@type":"QAPage","mainEntity":{"@type":"Question","name":"Error when computing vle of polyethylene + supercritical ethylene","text":"
I tried to compute the phase equilibrium of PE and ethylene with PC-SAFT EOS to reproduce the results of [T. Spyriouni, I.G. Economou / Polymer 46 (2005) 10772–10781]
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\nI modified the code in examples/pcsaft/PhaseDiagrmBinary.ipynb for supercritical mixture and is like this:
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from feos.si import *\nfrom feos.pcsaft import *\nfrom feos.eos import *\n\nimport matplotlib.pyplot as plt\nimport numpy as np\n\nethylene = PureRecord(\n    identifier=Identifier(\n        cas='74-85-1',\n        name='ethylene',\n        iupac_name='ethene',\n        smiles='C=C',\n        inchi='InChI=1/C2H4/c1-2/h1-2H2',\n        formula='C2H4'\n    ),\n    molarweight=28.05,\n    model_record=PcSaftRecord(\n        m=1.593,\n        sigma=3.445,\n        epsilon_k=176.47,\n    )\n)\n\npolyethylene = PureRecord(\n    identifier=Identifier(\n        cas='9002-88-4\"',\n        name='polyethylene',\n        iupac_name='whatever',\n        smiles='whatever',\n        inchi='Whatever',\n        formula='[C2H4]n'\n    ),\n    molarweight=99000,\n    model_record=PcSaftRecord(\n        m=2603.7,\n        sigma=3.75,\n        epsilon_k=252.00,\n    )\n)\n\nparams = PcSaftParameters.new_binary([ethylene, polyethylene], binary_record=0.0427)\n\nsaft = EquationOfState.pcsaft(params)\ndia_p = PhaseDiagram.binary_vle(saft, 423.15*KELVIN)\n
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But I got a error that
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dia_p = PhaseDiagram.binary_vle(saft, 423.15*KELVIN)\n            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\nRuntimeError: System is supercritical.\n
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I also tried the mixture of supercritical ethylene with shorter alkanes, FeOs pcsaft works well. Is it a error solving equations for polymer’s properties?
","upvoteCount":1,"answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"
Thank you for bringing this to our attention and the comprehensive example! While PC-SAFT can and has been used to describe properties of polymers, it was not a high priority of ours during the development of FeOs. The special circumstances like the high pressures and the extremely low (molar) concentrations of the polymer pose challenges on standard phase equilibrium calculations. The calculation of properties (e.g. activity or fugacity coefficients) can be expected to work perfectly fine for polymers. However, you would need a dedicated algorithm to determine the cloud or shadow points of polymer/monomer mixtures.
","upvoteCount":1,"url":"https://github.com/feos-org/feos/discussions/234#discussioncomment-9057601"}}}