The PPR78 model is a predictive cubic equation of state relying on the group-contribution concept. Our previous studies have highlightened its capacity to predict the phase behavior of mixtures containing a large variety of compounds: alkanes, alkenes, aromatic compounds, permanent gases, sulfur compounds, etc. In this paper, it is attempted for the first time to answer the question "can the PPR78 model be safely used in energy-rate balances?". To do so, the largest possible number of enthalpy of mixing data and isobaric heat capacity of mixing data were collected in the open literature and predicted using the PPR78 model. It is shown that although certainly perfectible, this model generally provides from acceptable to accurate estimations of these properties depending on the nature of the mixtures and the conditions of temperature and pressure as well. Furthermore, this paper proposes some general reflections both on conceptual and practical issues: Is it always possible to claim that the excess enthalpy and the enthalpy of mixing are two strictly equivalent quantities? Does an equation of state have the same capacity to reproduce enthalpy of mixing data in one-phase and in two-phase regions? Which criterion should be used for evaluating the accuracy of an equation of state in terms of energy-rate balances?

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International audienceCubic equations of state (EoS) are widely used for the prediction of thermodynamic properties of petroleum fluids containing both well-defined and pseudo-components. Such EoS require as input parameters the critical temperature (T-c), the critical pressure (P-c), and the acentric factor (omega) of each compound. For well-defined components, such properties are known from experiments and easily obtained. For pseudo-components they are routinely estimated using one of the numerous characterization methods (CM) available in the open literature. A CM is nothing more than a set of correlations which makes it possible to estimate T-c, P-c, and omega of a pseudo-component (PC) from the knowledge of its normal boiling point (NBP), molecular weight (MW), or specific gravity (SG). Regarding the binary-interaction parameters (BIP) k(ij) (where i and/or j are/is a pseudo-component(s)) which appear in classical mixing rules, they are either set to zero or estimated by a specific correlation. Most of the proposed correlations are however purely empirical and usually only make possible the estimation of the k(ij) between light components (H2S, CO2, N-2, C-1, C-2, and C-3) and a pseudo-component. The full k(ij) matrix is thus beyond reach and the BIP are usually temperature-independent. In this work, the PPR78 model is used to predict BIP suitable for the PengRobinson EoS whereas the PR2SRK model is used to predict BIP suitable for any other cubic EoS. Since these models can be seen as group-contribution methods (GCM) to estimate the kij, one needs to access the chemical structure of each PC. The chemical structure of PC is however too complex to be precisely determined. For this reason, it was assumed that each PC was made of only three groups: C-PAR, C-NAP, and C-ARO in order to take into account their paraffinic, naphthenic, and aromatic characters, respectively. The occurrences (N) of the three aforementioned groups are determined from the knowledge of T-c,CM, P-c,(CM), and omega(CM) (issuing from a CM). To reach this goal, GC methods aimed at estimating T-c, P-c, and omega of hydrocarbons were developed. Such methods have the ability to consider only three elementary groups: C-PAR, C-NAP, and C-ARO. In the end, the three known properties (T-c,CM, P-c,(CM), and omega(CM)) can be expressed as functions of N-PAR, N-NAP, and N-ARO (the occurrences of the groups) and we thus only need to solve a system of three equations with three unknowns. To check its validity, the present approach is applied to the prediction of the phase behavior of real petroleum fluids containing pseudo-components. The test results show the pertinence of the proposed method to predict the k(ij) when i and/or j is a pseudo-component

A model is presented for the prediction of the corrosion rate by carbon dioxide (CO 2) under dewing conditions. A mechanistic approach is developed that takes into consideration the hydrodynamics, thermodynamics, heat and mass transfer, chemistry, and electrochemistry during the phenomenon of top-of-the line corrosion. This model is validated by experimental data. It offers a better insight into the role played by primary parameters such as temperature, total pressure, partial pressure of CO 2 , gas velocity, and condensation rate.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA full analysis of the problem of coupling two independent industrial simulators, a reservoir simulator and a steady-state network simulator, has been performed.