223 results found
Ramdin M, De Mot B, Morrison ART, et al., 2021, Electroreduction of CO2/CO to C2 Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis., Ind Eng Chem Res, Vol: 60, Pages: 17862-17880, ISSN: 0888-5885
Direct electrochemical reduction of CO2 to C2 products such as ethylene is more efficient in alkaline media, but it suffers from parasitic loss of reactants due to (bi)carbonate formation. A two-step process where the CO2 is first electrochemically reduced to CO and subsequently converted to desired C2 products has the potential to overcome the limitations posed by direct CO2 electroreduction. In this study, we investigated the technical and economic feasibility of the direct and indirect CO2 conversion routes to C2 products. For the indirect route, CO2 to CO conversion in a high temperature solid oxide electrolysis cell (SOEC) or a low temperature electrolyzer has been considered. The product distribution, conversion, selectivities, current densities, and cell potentials are different for both CO2 conversion routes, which affects the downstream processing and the economics. A detailed process design and techno-economic analysis of both CO2 conversion pathways are presented, which includes CO2 capture, CO2 (and CO) conversion, CO2 (and CO) recycling, and product separation. Our economic analysis shows that both conversion routes are not profitable under the base case scenario, but the economics can be improved significantly by reducing the cell voltage, the capital cost of the electrolyzers, and the electricity price. For both routes, a cell voltage of 2.5 V, a capital cost of $10,000/m2, and an electricity price of <$20/MWh will yield a positive net present value and payback times of less than 15 years. Overall, the high temperature (SOEC-based) two-step conversion process has a greater potential for scale-up than the direct electrochemical conversion route. Strategies for integrating the electrochemical CO2/CO conversion process into the existing gas and oil infrastructure are outlined. Current barriers for industrialization of CO2 electrolyzers and possible solutions are discussed as well.
Sanchez-Vicente Y, Trusler JPM, 2021, Saturated-Phase Densities of (CO2 + Methylcyclohexane) at Temperatures from 298 to 448 K and Pressures up to the Critical Pressure, JOURNAL OF CHEMICAL AND ENGINEERING DATA, ISSN: 0021-9568
Xiao X, Trusler JPM, Yang X, et al., 2021, Equation of State for Solid Benzene Valid for Temperatures up to 470 K and Pressures up to 1800 MPa, JOURNAL OF PHYSICAL AND CHEMICAL REFERENCE DATA, Vol: 50, ISSN: 0047-2689
Ansari H, Rietmann E, Joss L, et al., 2021, A shortcut pressure swing adsorption analogue model to estimate gas-in-place and CO2 storage potential of gas shales, Fuel: the science and technology of fuel and energy, Vol: 301, Pages: 1-13, ISSN: 0016-2361
Natural gas extraction from shale formations has experienced a rapid growth in recent years, but the low recovery observed in many field operations demonstrates that the development of this energy resource is far from being optimal. The ambiguity in procedures that account for gas adsorption in Gas-in-Place calculations represents an important element of uncertainty. Here, we present a methodology to compute gas production curves based on quantities that are directly accessed experimentally, so as to correctly account for the usable pore-space in shale. We observe that adsorption does not necessarily sustain a larger gas production compared to a non-adsorbing reservoir with the same porosity. By analysing the entire production curve, from initial to abandonment pressure, we unravel the role of the excess adsorption isotherm in driving this behaviour. To evaluate scenarios of improved recovery by means of gas injection, we develop a proxy reservoir model that exploits the concept of Pressure Swing Adsorption used in industrial gas separation operations. The model has three stages (Injection/Soak/Production) and is used to compare scenarios with cyclic injection of CO2 or N2. The results show that partial pressure and competitive adsorption enhance gas production in complementary ways, and reveal the important trade-off between CH4 recovery and CO2 storage. In this context, this proxy model represents a useful to tool to explore strategies that optimise these quantities without compromising the purity of the produced stream, as the latter may introduce a heavy economic burden on the operation.
Aljeshi YA, Taib MBM, Trusler JPM, 2021, Modelling the Diffusion Coefficients of Dilute Gaseous Solutes in Hydrocarbon Liquids, INTERNATIONAL JOURNAL OF THERMOPHYSICS, Vol: 42, ISSN: 0195-928X
Mutailipu M, Liu Y, Song Y, et al., 2021, The pH of CO2–saturated aqueous KCl solutions at temperatures between 298 K and 423 K at pressures up to 13.5 MPa, Chemical Engineering Science, Vol: 234, Pages: 1-10, ISSN: 0009-2509
The pH of CO2-saturated brines is of importance in geological carbon storage utilizing saline aquifers as it is a key variable controlling fluid-mineral chemical reactions that affect CO2 storage capacity and security. In this paper, we report experimental measurements of the pH of CO2-saturated aqueous KCl solutions carried out using high-pressure glass and ZrO2 pH electrodes, coupled with a Ag/AgCl reference electrode, at a temperatures from (298 to 423 K) and at pressure between (0.2 and 13.5) MPa. The results are in good agreement with values predicted using the Pitzer model with the McInnes convention as implemented in the PHREEQC geochemical simulator software. The pH of CO2-saturated KCl solutions decreases with increasing partial pressure of CO2 and increases with increasing temperature. Increasing the molality of the KCl solutions tends to lower the pH but not as rapidly as is the case the NaCl.
Torín-Ollarves GA, Trusler JPM, 2021, Solubility of Hydrogen in Sodium Chloride Brine at High Pressures, Fluid Phase Equilibria, Pages: 113025-113025, ISSN: 0378-3812
Ansari H, Joss L, Hwang J, et al., 2020, Supercritical adsorption in micro- and meso-porous carbons and its utilisation for textural characterisation, Microporous and Mesoporous Materials, Vol: 308, ISSN: 1387-1811
Understanding supercritical gas adsorption in porous carbons requires consistency between experimental measurements at representative conditions and theoretical adsorption models that correctly account for the solid’s textural properties. We have measured unary CO2 and CH4 adsorption isotherms on a commercial mesoporous carbon up to 25 MPa at 40 °C, 60 °C and 80 °C. The experimental data are successfully described using a model based on the lattice Density Functional Theory (DFT) that has been newly developed for cylindrical pores and used alongside Ar (87K) physisorption to extract the representative pore sizes of the adsorbent. The agreement between model and experiments also includes important thermodynamic parameters, such as Henry constants and the isosteric heat of adsorption. The general applicability of our integrated workflow is validated by extending the analysis to a comprehensive literature data set on a microporous activated carbon. This comparison reveals the distinct pore-filling behaviour in micro- and mesopores at supercritical conditions, and highlights the limitations associated with using slit-pore models for the characterisation of porous carbons with significant amounts of mesoporosity. The lattice DFT represents a departure from simple adsorption models, such as the Langmuir equation, which cannot capture pore size dependent adsorption behaviour, and a practical alternative to molecular simulations, which are computationally expensive to implement.
Lv P, Stevar MSP, Trusler JPM, 2020, Interfacial tensions in the (CH4 + CO2 + H2O) system under two- and three-phase conditions, Fluid Phase Equilibria, Vol: 522, Pages: 1-13, ISSN: 0378-3812
Interfacial properties of the (CH4 + CO2 + H2O) system are of great importance in many geotechnical engineering applications. In this study, we report the first experimental measurements of the interfacial tensions in the (CH4 + CO2 + H2O) system under both three-phase (VLLE) and biphasic conditions. The measurements were made by the pendant drop method. The compositions of the coexisting phases were obtained from a previous study of the phase behavior and the phase densities were then calculated from an equation of state. IFTs along five isotherms in the VLLE region and along six isotherms in biphasic region are reported. In the VLLE region, the IFT between the water-rich liquid and the gas phase varied between (33 and 39) mN·m−1, with a sharp increase as the pressure increased along an isotherm towards the upper critical end point. In the same region, the IFT between the water-rich and CO2-rich liquids varied between (30 and 33) mN·m−1. The IFT between the gas phase and the CO2-rich liquid phase was too small to measure accurately but an approximate value was obtained which is consistent with Antonov's equality. In the biphasic region, measurements were made at temperatures up to 423 K and at pressures up to 30 MPa. As observed in other water-gas systems, the IFT declines monotonically along isotherms with increasing pressure and decreases with increasing temperature at constant pressure.
Souza LFS, Ghafri SZSA, Fandiño O, et al., 2020, Vapor-liquid equilibria, solid-vapor-liquid equilibria and H2S partition coefficient in (CO2 + CH4) at temperatures between (203.96 and 303.15) K at pressures up to 9 MPa, Fluid Phase Equilibria, Vol: 522, Pages: 1-13, ISSN: 0378-3812
Vapor-liquid equilibrium (VLE) measurements of the (CO2 + CH4) system are reported along seven isotherms at temperatures varying from just above the triple point to just below the critical point of CO2 at pressures from the vapor pressure of pure CO2 to approximately 9 MPa, including near-critical states. From these data, the critical locus has been determined and correlated over its entire length. The VLE data are correlated with the Peng-Robinson equation of state (PR-EoS), using a temperature-dependent binary interaction parameter, and also compared with the predictions of the GERG-2008 equation of state. The former represents the phase compositions across all isotherms with a root-mean-square mole-fraction deviation of S = 0.0075 while, for the latter, S = 0.0126. Measurements of the three-phase solid-vapor-liquid equilibrium (SVLE) line are reported at temperatures from approximately (204 to 216) K and a new correlation is developed which is valid from 145 K to the triple point of CO2. Additionally, we report the partitioning of trace levels of H2S between coexisting liquid and vapor phases of the (CO2 + CH4) system and compare the results with the predictions of the PR-EoS.
Taib MBM, Trusler JPM, 2020, Diffusion Coefficients of Methane in Methylbenzene and Heptane at Temperatures between 323 K and 398 K at Pressures up to 65 MPa (vol 41, 119, 2020), INTERNATIONAL JOURNAL OF THERMOPHYSICS, Vol: 41, ISSN: 0195-928X
Al Habsi SSA, Al Ghafri SZS, Bamagain R, et al., 2020, Experimental and modelling study of the phase behavior of (methyl propanoate + carbon dioxide) at temperatures between (298.15 and 423.15) K and pressures up to 20 MPa, Fluid Phase Equilibria, Vol: 519, Pages: 1-8, ISSN: 0378-3812
In this work, we report phase equilibrium measurements on the system (methyl propanoate + carbon dioxide) carried out with a high-pressure quasi-static-analytical apparatus. The measurements were made along six isotherms at temperatures from (298.15 to 423.15) K and at pressures up to the critical pressure at each temperature. Vapor-liquid equilibrium (VLE) data obtained for the mixture have been compared with the predictions of the Statistical Associating Fluid Theory coupled with the Mie potential and a group-contribution approach for the functional group interaction parameters (SAFT-γ Mie). The group interaction parameters in SAFT-γ Mie for the COO–CO2 interaction have been revised in this work by fitting to our experimental VLE data. After tuning, the SAFT model was found to be in good agreement with the measured data for both the liquid and vapor phases. Additionally, the data were compared with the predictions of the Peng-Robinson equation of state (PR-EoS) with one-fluid mixing rules and a temperature-independent binary parameter. This model fitted the VLE data well, except in the critical region. The present work is expected to contribute to optimization of biodiesel production processes.
Humberg K, Richter M, Trusler JPM, et al., 2020, Measurements and modelling of the viscosity of (methane + ethane) mixtures at temperatures from (253.15 to 473.15) K with pressures up to 2 MPa, The Journal of Chemical Thermodynamics, Vol: 147, Pages: 1-17, ISSN: 0021-9614
We present viscosity measurements of three (methane + ethane) gas mixtures as well as of the pure fluids methane and ethane over the temperature range from (253.15 to 473.15) K at pressures between (0.1 and 2.0) MPa; the relative expanded combined uncertainty (k = 2) in viscosity ranges between (0.16 and 0.49) %. Measurements were carried out relative to helium using a rotating-body viscometer. The composition of the commercially purchased gas mixtures was verified in-house through highly accurate density measurements utilizing a well-proven two-sinker magnetic-suspension densimeter. We compare our experimental viscosities to experimental literature data, recent ab initio calculated values and correlations. Around ambient conditions, the new pure fluid data do not differ more than 0.1 % from reference and ab initio calculated values. At the highest temperature of the present study, deviations of the new data to ab initio data increase to 0.20 % and 0.33 % for methane and ethane, respectively. For an appropriate evaluation of the binary mixture data and for the purpose of data comparison, a second-order viscosity virial correlation for the present mixture was fitted to the experimental data for the pure fluids and for one mixture. The correlation is based on the modified Enskog theory for hard sphere mixtures. As a result, the relative deviations of the pure fluid data do not exceed 0.15 %, and the maximum relative deviation of all viscosity data from the model was 0.22 %. This implies that all experimental viscosity data are reproduced or predicted, respectively, within their experimental uncertainties.
Scholz CW, Sanchez-Vicente Y, Tananilgul T, et al., 2020, Speeds of Sound in n-Pentane at Temperatures from 233.50 to 473.15 K at Pressures up to 390 MPa, JOURNAL OF CHEMICAL AND ENGINEERING DATA, Vol: 65, Pages: 3679-3689, ISSN: 0021-9568
Taib MBM, Trusler JPM, 2020, Diffusion Coefficients of Methane in Methylbenzene and Heptane at Temperatures between 323 K and 398 K at Pressures up to 65 MPa, INTERNATIONAL JOURNAL OF THERMOPHYSICS, Vol: 41, ISSN: 0195-928X
Zheng L, Rucker M, Bultreys T, et al., 2020, Surrogate models for studying the wettability of nanoscale natural rough surfaces using molecular dynamics, Energies, Vol: 13, ISSN: 1996-1073
A molecular modeling methodology is presented to analyze the wetting behavior of natural surfaces exhibiting roughness at the nanoscale. Using atomic force microscopy, the surface topology of a Ketton carbonate is measured with a nanometer resolution, and a mapped model is constructed with the aid of coarse-grained beads. A surrogate model is presented in which surfaces are represented by two-dimensional sinusoidal functions defined by both an amplitude and a wavelength. The wetting of the reconstructed surface by a fluid, obtained through equilibrium molecular dynamics simulations, is compared to that observed by the different realizations of the surrogate model. A least-squares fitting method is implemented to identify the apparent static contact angle, and the droplet curvature, relative to the effective plane of the solid surface. The apparent contact angle and curvature of the droplet are then used as wetting metrics. The nanoscale contact angle is seen to vary significantly with the surface roughness. In the particular case studied, a variation of over 65° is observed between the contact angle on a flat surface and on a highly spiked (Cassie–Baxter) limit. This work proposes a strategy for systematically studying the influence of nanoscale topography and, eventually, chemical heterogeneity on the wettability of surfaces.
Binti Mohd Taib M, Trusler JPM, 2020, Residual entropy model for predicting the viscosities of dense fluid mixtures, The Journal of Chemical Physics, Vol: 152, Pages: 164104-164104, ISSN: 0021-9606
In this work, we have investigated the mono-variant relationship between the reduced viscosity and residual entropy in pure fluids and in binary mixtures of hydrocarbons and hydrocarbons with dissolved carbon dioxide. The mixtures considered were octane + dodecane, decane + carbon dioxide, and 1,3-dimethylbenzene (m-xylene) + carbon dioxide. The reduced viscosity was calculated according to the definition of Bell, while the residual entropy was calculated from accurate multi-parameter Helmholtz-energy equations of state and, for mixtures, the multi-fluid Helmholtz energy approximation. The mono-variant dependence of reduced viscosity upon residual molar entropy was observed for the pure fluids investigated, and by incorporating two scaling factors (one for reduced viscosity and the other for residual molar entropy), the data were represented by a single universal curve. To apply this method to mixtures, the scaling factors were determined from a mole-fraction weighted sum of the pure-component values. This simple model was found to work well for the systems investigated. The average absolute relative deviation (AARD) was observed to be between 1% and 2% for pure components and a mixture of similar hydrocarbons. Larger deviations, with AARDs of up to 15%, were observed for the asymmetric mixtures, but this compares favorably with other methods for predicting the viscosity of such systems. We conclude that the residual-entropy concept can be used to estimate the viscosity of mixtures of similar molecules with high reliability and that it offers a useful engineering approximation even for asymmetric mixtures.
Trusler J, Binti Mohd Taib M, 2020, Viscosity and Density of 1,3-Dimethylbenzene + Carbon Dioxide at Temperatures from 298 to 423 K and at Pressures up to 100 MPa, Journal of Chemical and Engineering Data, Vol: 65, Pages: 2186-2193, ISSN: 0021-9568
We reported experimental measurements of the viscosity and density of mixtures of 1,3-dimethylbenzene and carbon dioxide with mole fractions of carbon dioxide between 0 and 0.652. In this study, we used a vibrating wire viscometer–densimeter to measure the viscosity and density simultaneously at temperatures ranging from 298 to 423 K and at pressures up to 100 MPa. The Tait–Andrade and Tait equations have been used to correlate the experimental data for viscosity and density, respectively, at each composition, and the absolute average relative deviations (AARDs) were found to be ≤0.7% for viscosity and ≤0.1% for density. We also developed correlations for the viscosity and density surfaces as functions of temperature, pressure, and mole fraction with AARDs of 1.9% for viscosity and 0.3% for density. The data presented in this work will contribute to developing predictive models for the thermophysical properties of asymmetric mixtures under high temperature and pressure conditions.
Muller E, Trusler J, Bresme F, et al., 2020, Employing SAFT coarse grained force fields for the molecular simulation of thermophysical and transport properties of CO2 – n-alkane mixtures, Journal of Chemical and Engineering Data, Vol: 65, Pages: 1159-1171, ISSN: 0021-9568
We report an assessment of the predictive and correlative capability of the SAFT coarse-grained force field as applied to mixtures of CO2 with n-decane and n-hexadecane. We obtain the pure and cross-interaction parameters by matching simulations to experimental phase equilibrium behavior and transfer these parameters to predict shear viscosities. We apply both equilibrium (based on the Green–Kubo formulation) and nonequilibrium (based on the application of an external force to generate an explicit velocity field) algorithms. Single- and two-site models are explored for CO2, and while for volumetric properties both models provide good results, only the model that aligns with the molecular shape is found to be robust when describing highly asymmetric binary mixtures over wide ranges of temperature and pressure. While the models provide good quantitative predictions of viscosity, deviations among the algorithms and with experimental data are encountered for binary mixtures involving longer chain fluids, and in particular at high-pressure and low-temperature states.
Malta JÁMSC, Calabrese C, Nguyen T-B, et al., 2020, Measurements and modelling of the viscosity of six synthetic crude oil mixtures, Fluid Phase Equilibria, Vol: 505, ISSN: 0378-3812
The viscosity and density are reported for six synthetic mixtures, composed of up to 13 components, designed to match a light, dead crude oil of API 32° and molar mass of approximately 184 g mol−1. The measurements were made in the liquid region at temperatures between (323 and 398) K and in the pressure range from 1 MPa to 70 MPa. The viscosity was measured with a vibrating-wire viscometer, while the density was measured by means of a vibrating U-tube densimeter. The density and viscosity data have expanded relative uncertainties of 0.12% and 1.2%, respectively with a coverage factor of 2.We have used the measured viscosity data to test the predictive power of the four viscosity models, the extended hard sphere (EHS), one-component EHS (1-cEHS), three-component EHS (3-cEHS) and Vesovic-Wakeham (VW), that have their basis in kinetic theory and the molecular description of the fluid. Two of the models (EHS and VW) require full compositional description of the mixture, while the other two belong to a new family of models which dispense with full compositional characterization, but retain molecular description. On average the EHS and VW models predict the viscosity data with lower deviations than 1-cEHS and 3-cEHS models, but all four models represent the data with uncertainty of 5–10%.
Sanchez-Vicente Y, Tay WJ, Al Ghafri SZ, et al., 2020, Density and phase behavior of the CO2 + methylbenzene system in wide ranges of temperatures and pressures, Industrial & Engineering Chemistry Research, Vol: 59, Pages: 7224-7237, ISSN: 0888-5885
Knowledge of the thermophysical properties of CO2-hydrocarbon mixtures over extended ranges of temperature and pressure is crucial in the design and operation of many carbon capture and utilization processes. In this paper, we report phase behavior, saturated-phase densities, and compressed-liquid densities of CO2 + methylbenzene at temperatures between 283 K and 473 K and at pressures up to 65 MPa over the full composition range. The saturated-phase densities were correlated by a recently developed empirical equation with an absolute average relative deviation (ΔAARD) of ∼0.5%. The compressed-fluid densities were also correlated using an empirical equation with an ΔAARD value of 0.3%. The new data have been compared with the predictions of two equations of state: the predictive Peng–Robinson (PPR-78) equation of state and the SAFT-γ Mie equation of state. In both of these models, binary parameters are estimated using functional group contributions. Both models provided satisfactory representation of the vapor–liquid equilibrium and saturated-phase-density data, but the accuracy decreased in the prediction of the compressed-liquid densities where the ΔAARD was ∼2%. The isothermal compressibility and isobaric expansivity are also reported here and were predicted better with SAFT-γ Mie than with PPR-78. Overall, the comparisons showed that SAFT-γ Mie performs somewhat better than PPR-78, but the results suggest that further refinement of the SAFT-γ Mie parameter table are required.
Krevor S, Blunt MJ, Trusler JPM, et al., 2020, Chapter 8: An introduction to subsurface CO<inf>2</inf> storage, RSC Energy and Environment Series, Pages: 238-295, ISBN: 9781788014700
The costs of carbon capture and storage are driven by the capture of CO2 from exhaust streams or the atmosphere. However, its role in climate change mitigation is underpinned by the potential of the vast capacity for storage in subsurface geologic formations. This storage potential is confined to sedimentary rocks, which have substantial porosity and high permeability in comparison to crystalline igneous and metamorphic rocks. These in turn occur in the sedimentary basins of the Earth's continents and near shore. However, the specific capacity for storage is not correlated simply to the existence of a basin. Consideration must also be made of reservoir permeability, caprock integrity, injectivity, fluid dynamics, and geomechanical properties of pressurisation and faulting. These are the topics addressed in this chapter. These processes and properties will combine in complex ways in a wide range of settings to govern the practicality of storing large volumes of CO2. There is clear potential for storage at the scale required to mitigate the worst impacts of global climate change, estimated to be in the order of 10 Gt CO2 per year by 2050. However, until at least dozens of commercial projects have been built in a range of geologic environments, the upper reaches of what can be achieved, and how quickly, will remain uncertain.
Chow YTF, Maitland GC, Trusler JPM, 2020, Erratum to “Interfacial tensions of (H2O + H2) and (H2O + CO2 + H2) systems at temperatures of (298 to 448) K and pressures up to 45 MPa” [Fluid Phase Equil. 475 (2018) 37–44], Fluid Phase Equilibria, Vol: 503, ISSN: 0378-3812
Galindo A, Trusler JPM, 2020, Preface, Fluid Phase Equilibria, Vol: 503, ISSN: 0378-3812
Ramdin M, Morrison ART, de Groen M, et al., 2019, High-pressure electrochemical reduction of CO2 to formic acid/formate: effect of pH on the downstream separation process and economics, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 22718-22740, ISSN: 0888-5885
We use a high-pressure semicontinuous batch electrochemical reactor with a tin-based cathode to demonstrate that it is possible to efficiently convert CO2 to formic acid (FA) in low-pH (i.e., pH < pKa) electrolyte solutions. The effects of CO2 pressure (up to 50 bar), bipolar membranes, and electrolyte (K2SO4) concentration on the current density (CD) and the Faraday efficiency (FE) of formic acid were investigated. The highest FE (∼80%) of FA was achieved at a pressure of around 50 bar at a cell potential of 3.5 V and a CD of ∼30 mA/cm2. To suppress the hydrogen evolution reaction (HER), the electrochemical reduction of CO2 in aqueous media is typically performed at alkaline conditions. The consequence of this is that products like formic acid, which has a pKa of 3.75, will almost completely dissociate into the formate form. The pH of the electrolyte solution has a strong influence not only on the electrochemical reduction process of CO2 but also on the downstream separation of (dilute) acid products like formic acid. The selection of separation processes depends on the dissociation state of the acids. A review of separation technologies for formic acid/formate removal from aqueous dilute streams is provided. By applying common separation heuristics, we have selected liquid–liquid extraction and electrodialysis for formic acid and formate separation, respectively. An economic evaluation of both separation processes shows that the formic acid route is more attractive than the formate one. These results urge for a better design of (1) CO2 electrocatalysts that can operate at low pH without affecting the selectivity of the desired products and (2) technologies for efficient separation of dilute products from (photo)electrochemical reactors.
Souza LFS, Herrig S, Span R, et al., 2019, Experimental density and an improved Helmholtz-energy-explicit mixture model for (CO<inf>2</inf> + CO), Applied Energy, Vol: 251, ISSN: 0306-2619
This study reports new density measurements of the (CO2 + CO) system at temperatures from (283 to 373) K and pressures up to 48 MPa for four different mixtures, with compositions ranging from (5 to 50) mol% CO. A commercial vibrating-tube densimeter was used to measure the density of each mixture as a function of pressure and temperature. Temperature and pressure were measured with expanded uncertainties (k = 2) of 0.05 K and 0.035 MPa, respectively. The relative combined expanded uncertainty (k = 2) of the density was estimated to be between (0.2 and 1.8) %, with values ≤1% for most state points. The new data significantly expand the pressure and composition ranges of the available density data for the (CO2 + CO) system. Together with recently published vapour-liquid-equilibrium data, the new data enabled the development of an improved Helmholtz-energy-explicit mixture model. The new model is based on the mathematical approach of the GERG-2008 and EOS-CG models with new adjustable parameters. As a result, the new mixture model allows for a significantly more accurate description of the thermodynamic properties of the (CO2 + CO) system than GERG-2008 and EOS-CG. A detailed comparison among our density data, experimental data from the literature and the different mixture models is presented.
Zheng L, Trusler JPM, Bresme F, et al., 2019, Predicting the pressure dependence of the viscosity of 2,2,4-trimethylhexane using the SAFT coarse-grained force field, Fluid Phase Equilibria, Vol: 496, Pages: 1-6, ISSN: 0378-3812
This work is framed within AIChE's 10th Industrial Fluid Properties Simulation Challenge, with the aim of assessing the capability of molecular simulation methods and force fields to accurately predict the pressure dependence of the shear viscosity of 2,2,4-trimethylhexane at 293.15 K (20 °C) at pressures up to 1 GPa. In our entry for the challenge, we employ coarse-grained intermolecular models parametrized via a top-down technique where an accurate equation of state is used to link the experimentally-observed macroscopic volumetric properties of fluids to the force-field parameters. The state-of-the-art version of the statistical associating fluid theory (SAFT) for potentials of variable range as reformulated in the Mie incarnation is employed here. The potentials are used as predicted by the theory, with no fitting to viscosity data. Viscosities are calculated by molecular dynamics (MD) employing two independent methods; an equilibrium-based procedure based on the analysis of the pressure fluctuations through a Green-Kubo formulation and a non-equilibrium method where periodic perturbations of the boundary conditions are employed to simulate experimental shear stress conditions. There is an indication that, at higher pressures, the model predicts a solid phase (freezing) which we believe to be an artefact of the simplified molecular geometry used in the modelling. A comparison (made after disclosure of the experimental data) show that the model consistently underpredicts the viscosity by about 30%, but follows the pressure dependency accurately.
Calabrese C, McBride-Wright M, Maitland GC, et al., 2019, Extension of vibrating-wire viscometry to electrically conducting fluids and measurements of viscosity and density of brines with dissolved CO2 at reservoir conditions, Journal of Chemical and Engineering Data, Vol: 64, Pages: 3831-3847, ISSN: 0021-9568
In order to design safe and effective storage of anthropological CO2 in deep saline aquifers, it is necessary to know the thermophysical properties of brine–CO2 solutions. In particular, density and viscosity are important in controlling convective flows of the CO2-rich brine. In this work, we have studied the effect of dissolved CO2 on the density and viscosity of NaCl and CaCl2 brines over a wide range of temperatures from 298 to 449 K, with pressures up to 100 MPa, and salinities up to 1 mol·kg–1. Additional density measurements were also made for both NaCl and CaCl2 brines with dissolved CO2 at salt molalities of 2.5 mol·kg–1 in the same temperature and pressure ranges. The viscosity was measured by means of a vibrating-wire viscometer, while the density was measured with a vibrating U-tube densimeter. To facilitate the present study, the theory of the vibrating-wire viscometer has been extended to account for the electrical conductivity of the fluid, thereby expanding the use of this technique to a whole new class of conductive fluids. Relative uncertainties were 0.07% for density and 3% for viscosity at 95% confidence. The results of the measurements show that both density and viscosity increase as a result of CO2 dissolution, confirming the expectation that CO2-rich brine solutions will sink in an aquifer. We also find that the effect of dissolved CO2 on both properties is sensibly independent of salt type and molality.
Al Ghafri SZS, Matabishi EA, Trusler JPM, et al., 2019, Speed of sound and derived thermodynamic properties of para-xylene at temperatures between (306 and 448)K and at pressures up to 66 MPa, Journal of Chemical Thermodynamics, Vol: 135, Pages: 369-381, ISSN: 0021-9614
The speed of sound in p-xylene has been measured at temperatures ranging from (306 to 447) K and at pressures from just above saturation to 66 MPa. Measurements were performed using a new double-path pulse-echo instrument, fabricated from Invar 36, that was designed for ease of assembly and calibration as well as robust operation. The cell’s path length was calibrated with water at a single state point against the IAPWS-95 equation of state, with path length corrections for temperature and pressure calculated using material-property data. Validation measurements on water over the range of experimental conditions investigated resulted in deviations from IAPWS-95 smaller than the equation’s relative uncertainty of 0.1 %. The expanded relative uncertainty of the measurements over the reported ranges of pressure and temperature varied from (0.023 to 0.104) % at 95 % confidence. The measured data for p-xylene were compared with the Helmholtz equation of state (EOS) of Zhou et al., which is stated to have a relative uncertainty in sound-speed of 0.3 % in the liquid region. Relative deviations between experiment and the EOS of up to 1 % were observed, especially at high temperatures and low pressures, indicating that the current Helmholtz model should be revised using the new experimental data. Additionally, density, isobaric specific heat capacity, and other thermodynamic properties of p-xylene were derived from the speed-of-sound data by thermodynamic integration; these results expand upon the available literature data and are generally in good agreement with the current Helmholtz EOS. The relative expanded uncertainties for liquid density and isobaric specific heat capacity in this work are estimated to be 0.2 % and 1 %, respectively, equivalent to the uncertainty of the EOS.
Fernandez J, Assael MJ, Enick RM, et al., 2019, International Standard for viscosity at temperatures up to 473 K and pressures below 200 MPa (IUPAC Technical Report), PURE AND APPLIED CHEMISTRY, Vol: 91, Pages: 161-172, ISSN: 0033-4545
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