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Modeling of Asphaltene Precipitation from Crude Oil with the Cubic Plus Association Equation of State
journal contribution
posted on 2017-01-03, 00:00 authored by Alay Arya, Xiaodong Liang, Nicolas von Solms, Georgios M. KontogeorgisIn
this study, different modeling approaches using the Cubic Plus
Association (CPA) equation of state (EoS) are developed to calculate
the asphaltene precipitation onset condition and asphaltene yield
from degassed crude oil during the addition of n-paraffin.
A single model parameter is fitted to calculate the asphaltene onset
condition during the addition of different n-paraffin
precipitants (n-pentane to n-hexadecane).
Three parameters per precipitant are fitted to calculate the asphaltene
yield during the addition of the precipitant. The results obtained
from the model are compared with the experimental data for eight different
crude oils. Results were also obtained for seven crudes using the
Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) EoS
based approach described in the literature. The CPA EoS based approaches
treat the asphaltene fraction as an associating component whereas
the PC-SAFT EoS based approach does not. A comparison between the
approaches shows that the CPA EoS based approaches, developed in this
work, give more reliable results. The predictions from the PC-SAFT
EoS based approach result in behavior that is unphysical: the mole
fraction of n-paraffin (at the precipitation onset)
and the asphaltene yield do not decrease with the carbon number of n-paraffin. Furthermore, it is shown that the approach,
developed in this work, can predict the onset conditions of asphaltene
precipitation resulting from a blend of two or more crudes.