Phase Equilibria for Carbon Capture and Storage

Carbon dioxide (CO2) is an important material in many industries but is also representing more than 80% of greenhouse gases (GHGs). Anthropogenic carbon dioxide accumulates in the atmosphere through burning fossil fuels (coal, oil, and natural gas) in power plants and energy production facilities, and solid waste, trees, and other biological materials. It is also the result of certain chemical reactions in different industry (e.g., cement and steel industries). Carbon capture and storage (CCS), among other options, is an essential technology for the cost-effective mitigation of anthropogenic CO2 emissions and could contribute approximately 20% to CO2 emission reductions by 2050, as recommended by International Energy Agency (IEA). Although CCS has enormous potential in numerous industries and petroleum refineries due their large CO2 emissions, a significant impediment to its utilization on a large scale remains both operating and capital costs. It is possible to reduce the costs of CCS for the cases where industrial processes generate pure or rich CO2 gas streams, but they are still an obstacle to its implementation. Therefore, significant interest was dedicated to the development of improved sorbents with increased CO2 capacity and/or reduced heat of regeneration. However, recent results show that phase equilibria, transport properties (e.g., viscosity, diffusion coefficients, etc.) and other thermophysical properties (e.g., heat capacity, density, etc.) could have a significant effect on the price of the carbon. In this context, we focused our research on the phase behavior of physical solvents for carbon dioxide capture. We studied the phase behavior of carbon dioxide and different classes of organic substances, to illustrate the functional group effect on the solvent ability to dissolve CO2. In this chapter, we explain the role of phase equilibria in carbon capture and storage. We describe an experimental setup to measure phase equilibria at high-pressures and working procedures for both phase equilibria and critical points. As experiments are usually expensive and very time consuming, we present briefly basic modeling of phase behavior using cubic equations of state. Phase diagrams for binary systems at high-pressures and their construction are explained. Several examples of phase behavior of carbon dioxide + different classes of organic substances binary systems at high-pressures with potential role in CCS are shown. Predictions of the global phase diagrams with different models are compared with experimental literature data

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Vapour -liquid equilibrium, thermodynamic and volumetric properties were predicted for three pure hydrofluorocarbons: difluoromethane (R32), pentafluoroethane (R125) and 1,1,1,2 -tetrafluoroethane (R134a) Refrigerants are the working fluids in refrigeration, airconditioning and heat pumping systems. The development of models for representation and prediction of physical properties and phase equilibria as well as the improvement of current equations of state (EOS) is of particular interest for the refrigeration industry The difluoromethane (R32), pentafluoroethane (R125) and 1,1,1,2 -tetrafluoroethane (R134a) are environmentally acceptable refrigerants (their ozone depletion potentials are zero) and present a considerable interest in the search for alternative refrigerants. In previous works [3, 4] some properties of pure refrigerants and refrigerant mixtures were calculated by cubic equations of state. The purpose of this paper is to present the result of simultaneous calculation of vapour -liquid equilibrium, thermodynamic and volumetric properties on R32, R125, and R134a pure fluids as well as on binary and ternary mixtures of these refrigerants. Three cubic equations of state GEOS3C The GEOS3C equation of state The GEOS3C equation of state is a general form The GEOS3C equation is based on the GEOS equation In this work, the coefficients a, b, c, d of eqn. (1) were obtained for mixtures of hydrofluorocarbons using the classical van der Waals mixing rules without interaction parameters Results and discussions In order to predict accurate values for mixture properties, an equation of state must first be able to properly represent the behavior of pure substances. The equations of state GEOS3C, SRK and PR were tested firstly to calculate equilibrium and thermodynamic properties for R32, R125 and R134a pure fluids, along the saturation curve. The calculations were compared with data of ASHRAE collection The following thermodynamic properties have been calculated together with the saturation pressure and the two phase densities: compressibility factor, Z; enthalpy, H; enthalpy of vaporization, ∆ vap H; entropy, S. The results of the calculations for R32, R125 and R134a are summarized in tables 2-4

Measurement and modelling of mass diffusion coefficients for application in carbon dioxide storage and enhanced oil recovery

In this work, measurements were carried out by the Taylor dispersion method [1, 2] to determine the mutual diffusion coefficient for CO2 in water or hydrocarbon at effectively infinite dilution. Measurements were carried out for CO2 in water, hexane, heptane, octane, decane, dodecane, hexadecane, cyclohexane, squalane and toluene at temperatures between 298 K and 423 K with pressures up to 69 MPa. Measurements of CO2 diffusivity in different brines were also carried out by 13C pulsed-field gradient NMR

An improved reduction method for phase stability testing in the single-phase region

A new reduction method for mixture phase stability testing is proposed, consisting in Newton iterations with a particular set of independent variables and residual functions. The dimension of the problem does not depend on the number of components but on the number of components with nonzero binary interaction parameters in the equation of state. Numerical experiments show an improved convergence behavior, mainly for the domain located outside the stability test limit locus in the pressure–temperature plane, recommending the proposed method for any applications in which the problematic domain is crossed a very large number of times during simulations

High-pressure phase equilibrium for carbon dioxide + ethyl n -butyrate binary system

Vapor-liquid equilibrium data were measured for the carbon dioxide + ethyl n-butyrate (EB) binary system at high-pressures. Five isotherms are reported at (333.15, 343.15, 353.15, 363.15, and 373.15) K and pressures up to 121.75 bar. A static-analytical method with phases sampling was used. The new experimental results are compared with existing literature data and discussed. In order to provide a continuous and consistent description of the system phase behavior, unique sets of interaction parameters for different approaches with the Peng-Robinson (PR) equation of state (EoS) and classical van der Waals mixing rules were obtained. A constant kij value of -0.048 is recommended, providing an excellent description of the data reported in this work, especially for the liquid phase. Predictions are also compared with the other available literature data and discussed.Fil: Sima, Sergiu. University Politehnica of Bucharest. Faculty of Applied Chemistry and Materials Science. Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry; RumaniaFil: 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: Secuianu, Catinca. University Politehnica of Bucharest. Faculty of Applied Chemistry and Materials Science. Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry; Rumania. Imperial College London. Department of Chemical Engineering; Reino Unid

Editor's preface for the special issue ``Romanian International Conference on Chemistry and Chemical Engineering''

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