Activity coefficients in nearly athermal mixtures predicted from equations of state: Don't blame the cubic when it is the lack of a third parameter!

The idea that cubic EoS's are very primitive and limited models, quite extended at present among researchers working on fluid properties and phase equilibria, has different roots, including some limitations observed specifically for classic and popular equations like Peng-Robinson (PR) or Soave-Redlich-Kwong (SRK). These are two-parameter models, i.e. they have only an attractive and a repulsive parameter to characterize each molecule, while other models like SAFT but also cubic –and still for non-associating molecules-introduce also a third parameter related somehow to the molecular structure or shape. One of the alluded limitations, actually a very clear one, is the complete failure in describing the non-ideality in nearly athermal mixtures, like those composed of n-alkanes with different chain lengths: SRK and PR predict positive deviations from ideality, which increase with the system asymmetry, while experimental measurements show exactly the opposite, i.e. increasing negative deviations from ideality. This provides an excellent opportunity to try to clarify whether such failure is due to the cubic nature of these classic models or to their two-parameter character and/or to the classic van der Waals one-fluid (vdW1f) mixing rules typically used. With that motivation, in this work we used models representing three different categories, in a completely predictive way: a two-parameter cubic EoS (PR), a three-parameter cubic EoS (RKPR) and a three-parameter SAFT EoS (PC-SAFT). Their predictions of infinite dilution activity coefficients were analyzed and compared, in contrast to available data for different mixtures of n-butane to n-octane as the lighter compound and paraffins ranging from C16 to C36 as the heavier, in both extremes of dilution. The obtained results, and their analysis, allowed us to extract very clear conclusions which were not present in the literature so far, regarding the importance of a third parameter in any type of EoS.Fil: Tassin, Natalia Giselle. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Rodriguez Reartes, Sabrina Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Cismondi Duarte, Martín. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentina. YPF - Tecnología; Argentin

A comparative study between Helmholtz and entropy scaling approaches for viscosity of natural gas mixtures based on the GERG-2008 equation of state

This study compares the perfomance of Helmholtz scaling approach, the residual entropy scaling approach, and the modified entropy scaling approach proposed by Bell for predicting the viscosities of pure n-alkanes, as well as other light compounds, and natural gas mixtures at different pressure and temperature conditions. The modified entropy scaling approach showed the lowest global average absolute deviation (AAD) for pure components, with a value of 2.37%. In comparison, the Helmholtz scaling approach had a slightly higher value of 2.70%, while the entropy scaling approach produced the highest value at 4.02%. The predictive performance of different mixing rules was evaluated for a strongly asymmetric binary system (methane + n-decane), across a broad range of compositions, pressures, and temperatures. For all-natural gas mixtures, excellent results were achieved with similar AAD values obtained for entropy and Helmholtz scaling approaches, at 2.73% and 2.72%, respectively. The modified entropy scaling approach presented an AAD value of 3.12%. The results obtained with each of the binary and multicomponent mixtures allowed us to confirm the accuracy of the Helmholtz scaling, entropy scaling, and modified entropy scaling approach using GERG 2008 in the prediction of natural gas viscosities when appropriate mixing rules were selected for each approach.Fil: Theran Becerra, Oscar Ivan. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Benelli, Federico Ezequiel. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Cismondi Duarte, Martín. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentin

New correlations for prediction of high-pressure phase equilibria of n-alkane mixtures with the RKPR EoS: Back from the use of l ij (Repulsive) interaction parameters

After detecting some inadequate predictions of volumetric properties and solid-liquid equilibria with the RKPR Equation of State coupled to previously correlated parameters (Cismondi Duarte, M.; et al. Fluid Phase Equilib. 2015, 403, 49-59), we analyzed the causes and concluded that the problems were related to the predominant role of the lij repulsive interaction parameter on those correlations. With the aim of proposing a model able to describe in a correct and consistent way the phase and volumetric behavior of the n-alkane-n-alkane binary mixtures, including the more asymmetric ones, here we made a turn back from our previous parameter correlations. Leaving behind the use of lij parameters, which combined with the arithmetic average combining rule transforms the quadratic into a linear mixing rule for the covolume, we developed in this work for PR and RKPR EoS new correlations of the kij attractive parameters with temperature dependence for the homologous series of binary mixtures formed by methane, ethane, propane, n-butane, or n-pentane with heavier normal alkanes, adopting zero values when both carbon numbers are equal to or higher than six. This also involved a new parametrization of pure n-alkanes for the RKPR EoS and new volume shift correlations for both models. The results show a very good predictive power for the phase behavior of n-alkane binary systems, with RKPR showing a much better performance than that of PR in the case of the more asymmetric systems, and a correct description of volumetric properties.Fil: Tassin, Natalia Giselle. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Rodriguez Reartes, Sabrina Belen. Departamento de Ingenieria Quimica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Cismondi Duarte, Martín. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentin

Molecular solvent design and near critical solvents optimization with ecofac

In this work an efficient analysis tool for separation process design and property predictions is presented. ECOFAC can estimate pure compound and solution properties, specially some of environmental interest, generate the best potential solvents for a specific liquid-liquid extraction or extractive distillation problem through molecular design, or find the optimal operating conditions for a given supercritical extraction process.Fil: Cismondi Duarte, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Díaz, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Espinosa, Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Assessment of ground deformation and seismicity in two areas of intense hydrocarbon production in the Argentinian Patagonia

The exploitation of both conventional and unconventional hydrocarbons may lead to still not well-known environmental consequences such as ground deformation and induced/triggered seismicity. Identifying and characterizing these effects is fundamental for prevention or mitigation purposes, especially when they impact populated areas. Two case studies of such effects on hydrocarbon-producing basins in Argentina, the Neuquén and the Golfo de San Jorge, are presented in this work. The intense hydrocarbon production activities in recent years and their potential link with the occurrence of two earthquakes of magnitude 4.9 and 5 near the operating well fields is assessed. A joint analysis of satellite radar interferometry and records of fluid injection and extraction demonstrate that, between 2017 and 2020, vertical ground displacements occurred in both study areas over active well fields that might indicate a correlation to hydrocarbon production activities. Coseismic deformation models of the two earthquakes constrain source depths to less than 2 km. The absence of seismicity before the beginning of the hydrocarbon activities in both areas, and the occurrence of the two largest and shallow earthquakes in the vicinity of the active well fields just after intensive production periods, points towards the potential association between both phenomena.Fil: Tamburini Beliveau, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Grosso Heredia, Javier A.. Universidad Nacional del Comahue; ArgentinaFil: Béjar Pizarro, Marta. Instituto Geológico y Minero de España; EspañaFil: Pérez López, Raúl. Instituto Geológico y Minero de España; EspañaFil: Portela, Juan. Universidad Politécnica de Madrid; EspañaFil: Cismondi Duarte, Martín. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; ArgentinaFil: Monserrat, Oriol. Centre Tecnològic de Telecomunicacions de Catalunya; Españ

Phaseenvelopes for reservoir fluids with asphaltene onset lines: An integral computation strategy for complex combinations of two- and three phase behaviors

Despite the fact that many publications have dealt with asphaltene onset pressure (AOP) lines during the last 2 or 3 decades, no explicit method for tracing these and other related boundaries from equation of state (EoS) models has been proposed in the literature. In this work, a new integral algorithmic strategy for the construction of complete phase envelope diagrams based on an EoS is presented. The method of Michelsen for tracing two-phase boundaries is used, while for three-phase saturation lines, an equivalent method was designed, including a second set of K factors and a phase fraction as extra independent variables. The double-saturation point is defined, and its importance is highlighted, from both phase behavior and algorithmic perspectives. Specific issues as recognition of unstable segments, such as false bubble curves, are also discussed. Three different fluids from the literature are taken as case studies to illustrate the application of the proposed strategy and discuss different types of behavior. In particular, an unexpected second three-phase region was predicted at higher temperatures in two of the three cases studied. This could serve as inspiration for new experimental studies, to see whether the existence of such a region can be confirmed for some reservoir fluids, or it could be just an artificial behavior predicted by the models. In summary, computer codes based on the proposed strategy might become a useful tool for researchers or professionals dealing with asphaltene phase behavior in reservoir fluids.Fil: Cismondi Duarte, Martín. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentin

Automated calculation of complete Pxy and Txy diagrams for binary systems

An algorithm for the calculation of global phase equilibrium diagrams has been recently developed [M. Cismondi, M.L. Michelsen, Global phase equilibrium calculations: critical lines, critical end points and liquid-liquid-vapour equilibrium in binary mixtures, J. Supercrit. Fluids 39 (2007) 287-295]. It integrates the calculation of critical lines, liquid-liquid-vapour (LLV) lines and critical end points, and was implemented in the software program GPEC: global phase equilibrium calculations [M. Cismondi, D.N. Nuñez, M.S. Zabaloy, E.A. Brignole, M.L. Michelsen, J.M. Mollerup, GPEC: a program for global phase equilibrium calculations in binary systems, in: Proceedings of the CD-ROM EQUIFASE 2006, Morelia, Michoacán, Mexico, October 21-25, 2006; www.gpec.plapiqui.edu.ar]. In this work we present the methods and computational strategy for the automated calculation of complete Pxy and Txy diagrams in binary systems. Being constructed from the points given by the global phase diagram at a specified temperature or pressure, their calculation does not require the implementation of stability analysis. We illustrate the application of the algorithm through a variety of Pxy and Txy diagrams generated using the RK-PR EOS.Fil: Cismondi Duarte, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Michelsen, Michael. Technical University of Denmark; Dinamarc

Molecular Design of Solvents: An Efficient Search Algorithm for Branched Molecules

A fast generation and test algorithm is applied within a new approach for designing branched molecules with physical properties and molecular constraints. Computer-aided product design requires the generation of feasible compounds and the prediction of mixture and pure-component properties by group contribution methods. A desirable property of the molecular design procedure is the chemical stability/feasibility of the generated chemical structures. On the basis of the electronegativity of the group attachments, a new characterization of group combination properties and the corresponding feasibility criteria for computer-aided generation of branched structures are presented. A synthesis procedure and a strategy for reducing the size of the combinatorial synthesis problem are discussed. Finally, the corresponding step-by-step algorithm is described.Fil: Cismondi Duarte, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Global phase equilibrium calculations: Critical lines, critical end points and liquid–liquid–vapour equilibrium in binary mixtures

A general strategy for global phase equilibrium calculations (GPEC) in binary mixtures is presented in this work along with specific methods for calculation of the different parts involved. A Newton procedure using composition, temperature and volume as independent variables is used for calculation of critical lines. Each calculated point is analysed for stability by means of the tangent plane distance, and the occurrence of an unstable point is used to determine a critical endpoint (CEP). The critical endpoint, in turn, is used as the starting point for constructing the three-phase line. The equations for the critical endpoint, as well as for points on the three-phase line, are also solved using Newton's method with temperature, molar volume and composition as the independent variables. The different calculations are integrated into a general procedure that allows us to automatically trace critical lines, critical endpoints and three-phase lines for binary mixtures with phase diagrams of types from I to V without advance knowledge of the type of phase diagram. The procedure requires a thermodynamic model in the form of a pressure-explicit EOS but is not specific to a particular equation of state.Fil: Cismondi Duarte, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Michelsen, Michael L.. Technical University of Denmark; Dinamarc

A General Approach to Phase Diagrams for Binary Systems

This chapter illustrates the wide variety of binary fluid phase equilibrium diagrams that can be obtained using models of the equation of state (EOS) type. It also highlights the need for paying attention to the predicted binary key lines, such as critical and liquid–liquid–vapor (LLV) equilibrium lines, when fitting binary interaction parameters of an EOS model. Besides, efficient algorithms for the EOS-based automated computation of complete Univariant Lines Phase Equilibrium Diagrams and of complete restricted binary phase equilibrium diagrams, such as isoplethic, isothermal, or isobaric diagrams, are described.Fil: Cismondi Duarte, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; ArgentinaFil: Zabaloy, Marcelo Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin