Abstract In this paper, the soave-Redlich-Kwong (SRK) Eos is modified based onperturbation theory. The parameter of the new cubic equation of stateconsidered reduced temperature and a centric factor dependent. The average ofabsolute deviations of predicted vapor pressure, vapor volume and saturatedliquid density of 30 pure compounds are 0.814.2.G14 and 5.814%, respectively.Also comparison with the new equation of vaporization of pure compounds aregiven. The florry-Hugines (FH) model is similarly modified by an adjustableparameter. This parameter is defined based on molecular weight of asphaltene tomolecular weight of heavy oil ratio in form of polynomial function. The phasebehavior of asphaltene was extended by these modifications and theprecipitation of asphaltene is calculated by three n-alkanes solvents. Thecomparison between results is shown. The new model relatively accurate forpredicting phase behavior of asphaltene in heavy oil.
Introduction Deposition of complex and heavy organic compounds, which exist in petroleumcrude particularly in heavy oil, can cause a number of serious problems.Asphaltenes could flocculated under many different conditions, two commonlyconsidered examples an the asphaltenes produced by titration with n-alkanes andthose that appear during depressurization of live crude oils. Trbovich and King(1) listed 11 different causes of asphaltenes deposition (CO 2, rich gas), ph shift, maxing of crude streams, incompatible organic chemicals, stimulation, shear, pressure drop, streaming potential, temperature drop andcharged, bare metal surface one of the first thermodynamic models was developedby Hirschberg at all. This model considers the oil to be a binary mixture oftwo liquids (asphalt and solvent).
In their model, asphalt (resin and asphaltene) precipitates as singlehomogeneous compounds. In 1987, Leontaritis and Mansoori(2)proposed athermodynamic-colloid model, which is capable of predicting the onset ofasphaltene flocculation.
This model postulates that asphaltenes exist in the oil as solid particlesin colloidal suspension, stabilized by resins absorbed on their surface. Morerecently, Kawanka et al (3). Reported a continuous dynamic model in which theonset as well as the amount of asphaltene deposits can be predicted with themolecular weight distributions of asphaltenes.
They considered asphaltenes to be heterogeneous poly dispersed polymers.
Lark, Park and Mansoori (4) combined the two theories, namely, continuousthermodynamic model and steric colloidal model and developed the so-calledfractal aggregation model theory of heterogeneous polymer solutions for theprediction of the onset and around of asphaltene precipitations.
In this study, the SRK equation of state is modified. Based on simplifiedtheory of hard-core model. Also the flory-Huggine model modified by adjustableparameters based on ratio of molecular weight of asphaltene to molecular weightof heavy oil. With using these modifications phase behavior of asphaltene inheavy oil mixture has been studied.