engleski

Modeliranje fizikalno-kemijskih svojstava nafte /Brončana medalja/

The basic model was developed as the continuation of our previous research1–4 dealing with the concept of additive group contributions method5, 6 with use the pseudo-component approach7. Then, the program entitled CRUDE_OIL_PROPERTIES has been designed which is based on this model for prediction the properties of crude oil. The program is the most important part of the innovation. The model requires the following data: a complete TBP-analysis (boiling point temperature vs. liquid volume boil-off), a PNA (paraffin-naphthene-aromatic) analysis and density, preferably for each sub fraction. Often, all of these data are not available for complex carbon mixtures such as crude oil and various procedures for transforming incomplete information on C6+ fraction into satisfactory TBP analyses are used as described in reference 8. The procedure is as follows: • The TBP curve is divided in five sub fractions or pseudo-components (the number of pseudo-components should be as low as possible, and five to ten are recommended), as shown in Figure 1, each containing three model compounds: one paraffinic (P), one naphthenic (N), and one aromatic (A). Figure 1. The TBP analysis of the crude oil Obod from INA oil fields • Model compounds are defined for each pseudo-component in terms of UNIFAC1 groups as –CH3, –CH2–, and ACH (aromatic hydrocarbon group) (Figure 2). • Adjustment of the number of group in each model compound is made so as to match the midvolume boiling point for each pseudo-component. The result of this procedure provides a set of well-defined model compounds which represent the complex petroleum mixture. Figure 2. Sample group assignments Example of calculation was done for the pseudo-component III (as shown in Figure 1). The observed midvolume boiling point is 320.2 K at 0.101 MPa, and the following PNA analysis yields 9.69% P, 51% N and 39.31% A. Our first set of model compounds is listed in Table 1. The number n is established with the bubble point of the mixture of model compound adjusted to the observed midvolume boiling point. The good agreement was obtained after five iterations, and results are shown in Table 2. Table 1. The first set of model compound Table 2. Final set of model compounds For T = 320.2 K we got n = 0.89. This corresponds to Mr = 132 (observed value 139), PP0 = 0.110, PN0 = 0.09 and PA0 = 0.107 MPa. Conclusions Calculated thermodynamic properties are compared with the corresponding experimental values and a very good agreement was obtained for temperatures less than 600 K. At higher temperatures, a relatively poor prediction can be attributed to the less reliable group of the UNIFAC model1 at more extreme conditions. Standard procedures may be used for estimation critical properties, acentric factor, and molecular masses of model compounds. This allows the inclusion of complex petroleum fraction in already generalized methods for phase equilibria calculation based on equation of state or the activity coefficient models. Literature 1. R. Vuković, A. Erceg, G. Bogdanić, HR Patent P980606 (2002). 2. A. Erceg Kuzmić, M. Radošević, G. Bogdanić, R. Vuković, HR Patent Notification P20070164 A2, (2008). 3. A. Erceg Kuzmić, M. Radošević, G. Bogdanić, R. Vuković, Fuel, 86 (10-11), 1409-1416 (2007). 4. A. Erceg Kuzmić, M. Radošević, G. Bogdanić, V. Srića, R. Vuković, Fuel, 87 (13-14) 2943-2950 (2008). 5. Aa. Fredenslund, J. Gmehling, P. Rasmussen, Vapor-Liquid Equilibria with UNIFAC. A Group Contribution Method, Elsevier, Amsterdam, 1977. 6. G. Bogdanić: Additive Group Contribution Methods for Predicting the Properties of Polymer Systems (Chapter 7, pp. 155-197), Polymeric Materials, Ed. A. Nastasijević, Transworld Research Signpost, Trivandrum, Kerala, India (2009). 7. K. S. Pedersen, Aa. Fredenslund, P. Thomassen, Properties of Oils and Natural Gases, Gulf Publishing Company, Book Division, Houston, 1985. 8. J. H .Erbar, Reserach Report 13, Gas Process Association, Tulsa, OK, 1997. The authors acknowledge the partial support of the Ministry of Science, Education and Sports of the Republic of Croatia (Grant No. 061-0000000-3029) and of the Czech Science Foundation (Grant No. 104/07/0444).

Modeliranje; Fizilakno-kemijska svojstva nafte

Brončana medalja