Equilibrium and transport properties of CO2+N2O and CO2+NO mixtures : a molecular simulation and equation of state modelling study.

International audienceIn the present study, the thermodynamic behaviour and transport properties of CO2+N2O and CO2+NO mixtures have been investigated using molecular simulation and equation of state modelling. Molecular simulations were based on Monte Carlo and Molecular Dynamics calculations using force fields calibrated from pure component properties and no adjustment of mixture properties was performed. Original force fields were proposed for N2O, NO and N2O2 molecules. Special attention must be paid when studying nitric oxide containing systems because this compound can exist as a mixture of monomers (NO) and dimers (N2O2) under certain pressure and temperature conditions. Liquid-vapour coexistence properties of the reacting NO-N2O2 system were thus first investigated using combined reaction ensemble and Gibbs ensemble Monte Carlo methods. Using the new force fields proposed, phase compositions, phase densities and phase viscosities were determined for CO2+NOx mixtures. Due to the strong similarities between carbon dioxide and nitrous oxide (Tc(CO2) = 304.21 K; Tc(N2O) = 309.57 K; Pc(CO2) = 7.38 MPa; Pc(N2O) = 7.24 MPa), the obtained thermodynamic and transport properties for a CO2+N2O mixture with 10 mol% of N2O are similar to pure CO2 properties in the whole range of studied temperatures (273 - 293 K), in agreement with available experimental data. Calculations of CO2+NO equilibrium and transport properties were also performed at three different temperatures in the range of 253 - 273 K. At these temperatures, only the monomer form of the nitric oxide (NO) has to be accounted for. The performed calculations are pure predictions since no experimental data are available in the open literature for this system. For a mixture containing 10 mol% of NO, the simulation results show a decrease of the liquid densities and viscosities of 9% and 24% with respect to corresponding pure CO2 values, respectively. The new pseudo-experimental data generated in this work were finally used to calibrate binary interaction parameters required in standard cubic equations of states. Both Peng-Robinson and Soave-Redlich-Kwong equations of state have been considered and after the regression, they display a decent match with experimental and pseudo-experimental data of the vapour-liquid equilibrium for the two studied mixtures

CO2 streams containing associated components—A review of the thermodynamic and geochemical properties and assessment of some reactive transport codes

AbstractModelling of the impact on storage of “ CO2-associated components” has rarely been addressed so far. This review, performed within the European research project CO2ReMoVe, exposes a selection of CO2 streams compositions coming from thermal power plants emissions and those injected in pilot sites part of the CO2ReMoVe project. It highlights the lack of data coming from laboratory experiments to describe properly the physical properties of some relevant gas mixtures. The geochemical impact of only 2 components (SO2 and H2S) is evidenced by some geochemical studies. Concerning the numerical modelling, four reactive transport codes (PHREEQC, SCALE2000, TOUGHREACT and COORES) were assessed. Actual limitations lie mainly in the capacity of calculating the physical properties of the whole set of gases (CO2–O2–SO2–N2–Ar–NOx–H2S–COS–CO–H2–HCl–NH3–CH4–C2H6–H2O). The new data acquired within on-going French projects will complete the knowledge of such complex gas mixtures behaviour

Industrial Perspective on Natural Gas Hydrates

Natural gas hydrates are usually considered as possible nuisances in the development of oil and gas fields, mainly in deepwater drilling operations and if multiphase transport technologies are to be examined. However they have an energetic potential value if economic recovery schemes are found for the enormous amounts of methane trapped in the hydrates naturally occurring in the earth crust ( white coal ). On another side, hydrates can be used for the safe and economic storage of natural gas, mainly in cold countries. In remote offshore areas, the use of hydrates for natural gas transportation is also presently considered as an economic alternative to the processes based either on liquefaction or on compression. This paper presents some possible medium-term industrial perspectives, either to reduce the nuisance of hydrates or to exploit their potential applications

Gas Permeation in Semicrystalline Polyethylene as Studied by Molecular Simulation and Elastic Model

We have employed molecular simulation to study the permeation of two different gases (CH4 and CO2) in polyethylene. The simulations have been performed at temperatures below the polymer melting point. Although under such conditions, polyethylene is in a semicrystalline state, we have used simulation boxes containing only a purely amorphous material. We showed in previous works [Memari P., Lachet V., Rousseau B. (2010) Polymer 51, 4978] that the effects of the complex morphology of semicrystalline materials on solubility can be implicitly taken into account by an ad-hoc constraint exerted on the amorphous phase. Here, it has been shown that our method can be applied not only for the calculation of equilibrium properties but also for transport properties like diffusion coefficients. In addition, the ad-hoc constraint has been theoretically related to the fraction of elastically effective chains in the material by making use of Michaels and Hausslein elastic model [Michaels A.S., Hausslein R.W. (1965) J. Polymer Sci.: Part C 10, 61]. We observe that the transport properties in amorphous regions are strongly governed by this fraction of elastically effective chains

Gas Permeation in Semicrystalline Polyethylene as Studied by Molecular Simulation and Elastic Model

We have employed molecular simulation to study the permeation of two different gases (CH4 and CO2) in polyethylene. The simulations have been performed at temperatures below the polymer melting point. Although under such conditions, polyethylene is in a semicrystalline state, we have used simulation boxes containing only a purely amorphous material. We showed in previous works [Memari P., Lachet V., Rousseau B. (2010) Polymer 51, 4978] that the effects of the complex morphology of semicrystalline materials on solubility can be implicitly taken into account by an ad-hoc constraint exerted on the amorphous phase. Here, it has been shown that our method can be applied not only for the calculation of equilibrium properties but also for transport properties like diffusion coefficients. In addition, the ad-hoc constraint has been theoretically related to the fraction of elastically effective chains in the material by making use of Michaels and Hausslein elastic model [Michaels A.S., Hausslein R.W. (1965) J. Polymer Sci.: Part C 10, 61]. We observe that the transport properties in amorphous regions are strongly governed by this fraction of elastically effective chains

Applications of Molecular Simulation in Oil and Gas Production and Processing

Molecular simulation is an emerging technique which consists in performing a detailed simulation of microscopic systems involving typically a few hundreds of molecules. On the basis of these simulations, appropriate statistical averages are performed to derive fluid properties that can be compared with experimental measurements. The purpose of the article is first to provide the reader with basic notions of molecular simulation. Then, application examples are given in several fields of the oil and gas industry. In reservoir engineering, the examples relate to the properties of poorly known hydrocarbons, the thermal properties of natural gases, and the phase equilibria and volumetric properties of acid gas - hydrocarbon mixtures. The application to gas production and processing is illustrated by the phase equilibria involving methanol (a common solvent or hydrate inhibitor) and the solubility at high pressure of gases in polymer materials. In hydrocarbon processing, the solubility of hydrogen sulfide in hydrocarbons at high temperature is discussed. For each type of problem, molecular simulation has provided useful predictions together with a better understanding of the relation between properties and chemical structure. It provides an intermediate way between experiments and classical thermodynamic models. Cheaper and more rapid than new measurements, it nonetheless allows an improved determination of the parameters of routine models