Measurement and Prediction of the Viscosity of Hydrocarbon Mixtures and Crude Oils

Crude oil is a complex mixture of hydrocarbons whose physical properties vary significantly with its composition, temperature and pressure. Viscosity is a particularly important property influencing the flow of oil in hydrocarbon reservoirs and its displacement by water and other fluids during production processes. The modelling and optimisation of such processes would be greatly aided by models which predict the viscosity of crude oils at (high) reservoir temperatures and pressures (HTHP), ideally from a knowledge of the oil composition. This research has involved making accurate HTHP viscosity measurements on a range of hydrocarbon systems and using these to evaluate the ability of an effective hard-sphere model to predict the data with minimal calibration. In the first phase, the viscosity and density of a range of pure hydrocarbons, representative of those found in crude oils, and their mixtures, were measured at temperatures and pressures covering typical reservoir conditions (up to 448.15 K and 135 MPa). The vibrating wire technique was used for viscosity in conjunction with a vibrating U-tube densimeter. The ability of the Dymond-Assael (DA) effective hard-sphere model to correlate and predict the viscosity of both the pure components and the complex mixtures was investigated. Agreement for pure components was within ± 5 % whereas for the mixtures this ranged from ± 5% to ± 25 % depending on the complexity. The same thermophysical properties were determined for two North Sea crude oil samples at temperatures ranging from (298.15 to 448.15) K and pressures up to 135 MPa. The effect of adding an alkane mixture diluent was also investigated. It was found that by treating the crude oils as effective single hydrocarbon components, the Dymond-Assael model could correlate their viscosity to within the experimental uncertainty and that of the diluted crudes to within ±10%. The overall study gives encouragement that a limited number of calibration viscosity/density measurements on a crude oil should enable prediction of its viscosity over a wide range of temperatures and pressures and enable viscosity changes to be predicted when crude oils are mixed with components whose DA parameters are known

Thermodynamic investigations of some aqueous solutions through calorimetry and densimetry

xvii, 220 leaves : ill. ; 28 cm.Relative densities and heat capacity ratios have been measured for selected aqueous systems. These measurements have been used to calculate apparent molar volumes and heat capacities. Densities of aqueous sodium bromide have been measured from 374 to 522 K and 10.00 to 30.00 MPa using a recently developed high temperature and pressure vibrating tube densimeter. These data have been used to test the utility of an automated high temperature and pressure densimetric data analysis program. Apparent molar volumes and heat capacities of several aqueous rare earth sulphate systems at 298.15 K and 0.10 MPa have been reported, and discussed in terms of ionic contributions. Single ion partial molar volumes and heat capacities for aqueous trivalent rare earth species have been estimated in a review of apparent molar data from the literature and through the use of semi-empirical Debye-Huckel equation. These singles ion properties have subsequently been used to estimate the single ion properties of the monosulphate and disulphate rare earth complex species. Rigorous relaxation calculations are presented in a discussion of apparent molar heat capacities, where relaxation contributions are shown to be negative. Apparent molar volumes and densities for aqueous L-histidine, L-phenylalanine, L-tyrosine, L-tryptophan, and L-dopa have been used to estimate reported partial molar properties have been added to several reported properites for other amino acids and peptides to construct an additivity scheme that utilises the revised Helgeson, Kirkham, and Flowers (HKF) equations of state for neutral organic species. A volumetric study of aqueous glycine, L-serine, and glyclylglycine has been conducted at temperatures from 298 K to 423 K and pressures from 0.10 to 30.00 MPa. These data have been used to evaluate HKF coefficients in a discussion of peptide stability at elevated temperatures and pressures

Modeling and Experimental Measurements of Thermodynamic Properties of Natural Gas Mixtures and Their Components

Chemical process design requires mathematical models for predicting thermophysical properties. Those models, called equations of state (EoS), need experimental data for parameter estimation and validation. This work presents a detailed description of a vibrating tube densimeter, which is an alternative technique for measurement of p-ρ-T data in gases at critical conditions. This apparatus can measure fluids in a temperature range of 300 K to 470 K and pressures up to 140 MPa. This work calibrates the vibrating tube using a physical-based methodology with nitrogen, methane and argon measurements. Carbon dioxide and ethane p-ρ-T data validate calibration procedures covering a wide range in density and pressure. The vibrating tube densimeter performs density measurements for nitrogen + methane mixtures for pressures up to 140 MPa. This work also presents a new equation of state (EoS) having a rational form that can describe properties with accuracy comparable to the best multi-parametric equations with less mathematical complexity. This EoS presents the Helmholtz residual energy as a ratio of two polynomial functions in density (no exponential terms in density are included), which can describe the behavior of pure components. The EoS can be transformed to describe other thermophysical properties as pressure, compressibility factor, heat capacity and speed of sound. Also this equation can calculate saturated liquid-vapor properties with 20 times less computational time. This work presents rational EoS for nitrogen, argon and methane applicable in wide ranges of pressure and temperature. Finally, this work proposes a new mixing rule for binary mixtures of gases based upon a quadratic combination of residual Helmholtz energy. This approach divides the energy contribution between interactions of same species and interaction of different species molecules. A rational form is proposed for description of energy interaction between molecules of different species. The mixing rule is applied to nitrogen + methane data

Redesign of a High-Pressure, Single-Sinker Magnetic Suspension Densimeter to Measure Highly Accurate Densities for Fluids: Applications to Helium, Argon, and Helium + Methane Mixtures

The petrochemical industry requires highly accurate equations of state (EoS) to calculate thermodynamic properties such as densities and calorific properties. However, the accuracy of an EoS depends upon the accuracy of the data used to construct it. Thus, a need exists for high accuracy p-p-T measurements. Multiple apparatus can provide high accuracy p-p-T measurements, but they do not operate over broad ranges of pressure and temperature. One apparatus that can operate over a broad range is a single sinker magnetic suspension densimeter (MSD). This work presents the redesign of the TAMU MSD. This apparatus is a unique MSD because its pressure measurement range extends to 200 MPa. A system redesign has enabled the apparatus to achieve a temperature range of 300 to 500 K. The redesign entailed creating a new electrical heating system, heating shields, vacuum insulation, and new frame. Improvements for the measurement processes of the system include a new measurement sequence that reduces measurement time by approximately half. After recommissioning the MSD, nitrogen measurements validated the system performance. After verifying system accuracy, measurements included two pure fluids, helium and argon, from 300 to 450 K up to 200 MPa. Additional measurements included three binary mixtures of methane + helium covering the same property ranges. Finally, this work proposes a new approach to creating mixing rules for binary mixtures of “simple” molecules based upon a quadratic compositional dependence of the residual Helmholtz energy. This approach describes the contributions from interactions between unlike molecules with an interaction Helmholtz energy. A rational polynomial in density with coefficients having both temperature and compositional dependence describes these interactions within the accuracy of experimental measurements. This form is less complex than other mixture models that include exponential terms in density, thus the approach is more attractive for process modeling. Mixtures containing methane, ethane, nitrogen, carbon dioxide, argon, hydrogen, krypton and helium provide tests for the mixing rule

Density and Phase Behavior of the CO2 + Methylbenzene System in Wide Ranges of Temperatures and Pressures

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

Caracterização e modelação de propriedades termofísicas e de excesso de misturas eutéticas

Deep eutectic solvents (DES), a new class of solvents, have attracted the researcher’s attention in the last years due to their unique and “green” properties, such as their easy formulation and environmental impact, projecting them as alternative solvents for a large number of applications, like catalysis, organic synthesis, dissolution and extraction processes, electrochemistry, material chemistry and desulfurization of fuels. DES are formed by an eutectic mixture of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). Owing to their promising applications, their physicochemical characterization, aiming at their use on industrial processes, stands highly relevant. This work focus on the formulation of eutectic mixtures, composed of [Ch]Cl + [EG], [Ch]Cl + [Gly] e [Ch]Cl + Ureia, and their thermophysical characterization, namely viscosity, density and boiling temperatures, at a wide range of temperatures (283 to 363 K) and pressures (0.05 to 100 MPa). The experimental data was further modeled using the soft-SAFT equation of state (EoS); an advance EoS able to explicitly account for the association between the DES constituents and shown to be able to describe the nonideality of the liquid phase. The soft-SAFT development allowed to propose new association schemes and molecular parameters for urea.Os solventes eutécticos profundos (DES), uma nova categoria de solventes, tem recentemente atraído a atenção dos investigados devido às suas propriedades. A sua preparação fácil e baixo impacto ambiental, têm projetado estes solventes alternativos para um grande número de aplicações, nomeadamente na eletroquímica, na catálise, na síntese orgânica, em processos de dissolução e extração e na dessulfurização de combustíveis. Os DES formam-se de uma mistura eutética de um dador de ponte de hidrogénio (HBD) e um recetor de pontes de hidrogénio (HBA). Devido ao seu potêncial e às enúmeras aplicações propostas, a sua caracterização físico-química torna-se extremamente relevante quando se imagina a sua introdução em processos industriais. Este trabalho é focado na formulação das misturas eutécticas compostas por [Ch]Cl + [EG], [Ch]Cl + [Gly] e [Ch]Cl + Ureia, e na sua caraterização termofísica, nomeadamente viscosidade, densidade e pontos de ebulição numa gama de temperatura entre 283.15 K e 363.15 K e a pressões entre 0.1 e 100MPa. Os dados experimentais foram posteriormente modelados usando a equação de estado (EoS) soft-SAFT; uma EoS capaz de ter em consideração a associação existente entre os componentes do DES e que consegue descrever a sua não idealidade em fase liquida. O desenvolvimento da soft-SAFT permitiu propor um novo esquema associativo e novos parâmetros moléculares para a ureia.Mestrado em Engenharia Químic

High pressure thermophysical behaviour of reference and new lubricants. Mineral, synthetic and vegetable oils and ionic liquids

This PhD Thesis is devoted to the study of several thermophysical properties, over broad ranges of temperature and pressure, of mineral and semisynthetic reference lubricants, vegetable oils and developed biodegradable lubricants, as well as ionic liquids (ILs) for their use as hydraulic fluids, gear and two stroke lubricants. The first property studied was the density from 278.15 K to 398.15 K up to 120 MPa. Density was measured by means of two different vibrating tube densimeters from Anton Paar (Graz, Austria). Results for eight reference oils, two vegetable base oils and eleven biodegradable lubricants for different applications are provided. Moreover density data for seven ILs are provided. Density data of all the studied fluids were correlated by means of the Tammann-Tait equation and the isothermal compressibility, κT, and the coefficient of thermal expansivity, αT, were obtained

High-accuracy P-p-T measurements of pure gas and natural gas like mixtures using a compact magnetic suspension densimeter

Highly accurate data for density measurements are required for engineering calculations as well for developing equations of state (EOS) for use in the custody transfer of natural gas through pipelines. The widely used present industry standard, the AGA8-DC92 EOS, was developed against a database of reference quality natural gas mixtures with compositions containing less than 0.2 mole percent of the heavier C6+ fraction. With the advances in technology in the late nineties, it is possible to produce gas from deep and ultra-deepwater of the Gulf of Mexico where the pressures and temperatures encountered are much higher. Produced gas mixtures have compositions containing higher percentages of the C6+ fraction. As AGA8-DC92 is a statistical fit equation developed for one set of conditions, time has come to evaluate its performance to assess whether it is still viable for gas custody transfer with a new set of conditions encountered. A highly accurate, high pressure and temperature, compact single sinker magnetic suspension densimeter has been used first to determine densities of pure componentâÂÂs densities for which very reliable data are available. After validating its performance, the densities of four light natural gas mixtures, containing no C6+ fraction and two heavy gas mixtures containing more than 0.2 mole percent of the heavier C6+ fraction, were measured. The light mixtures were measured in the temperature range of 250 to 450 K and in the pressure range of 10 to 150 Mpa (1450 to 21,750 psi); the heavy mixtures were measured in the range of 270 to 340 K and in the pressure range of 3.45 to 34.45 MPa (500 to 5,000 psi). Out of those, the data of only two light natural gas mixtures have been presented in the dissertation. Data on two heavy mixtures have not been published due to reasons of confidentiality. Measured densities of light mixtures, not containing the C6+ fraction show less than expected relative deviations from the AGA8-DC92 EOS predictions except at low temperature. The deviation with the recently developed GERG02 EOS was more pronounced. A force transmission error analysis and uncertainty analysis was carried out. The total uncertainty was calculated to be 0.105 %. The data measured as a part of this research should be used as reference quality data either to modify the parameters of AGA8-DC92 EOS or develop a more reliable equation of state with wider ranges of pressure and temperature

Lubricant properties of trimethylolpropane trioleate biodegradable oil: High pressure density and viscosity, film thickness, Stribeck curves and influence of nanoadditives

Lubricant properties of trimethylolpropane trioleate synthetic base oil (TMPTO) were experimentally determined under different temperatures, pressures and rolling-sliding conditions. With the aim to obtain the viscosity-pressure coefficient, density and viscosity measurements were performed up to 150 MPa with a falling-body viscometer and a vibrating tube densimeter, respectively. Film thickness and friction properties were determined with a ball-on-disc apparatus from temperatures of 303.15 to 353.15 K, from slide-roll ratios from 5 to 50% at 50 N (applied load). Finally, it has also been evaluated if the use of nanoparticles as additives could involve changes on film thickness and Stribeck curves of TMPTO base oil. For this aim, hexagonal-boron nitride nanoparticles (h-BN) and graphene nanoplatelets (GnPs) were used at mass concentrations of 0.25, 0.5 and 1.0 wt%. The viscosity of TMPTO increases from 15 mPa s (at 10 MPa and 353.15 K) to 525 mPa s (at 150 MPa and 303.15 K). The Stribeck curves for TMPTO are placed between elastohydrodynamic and mixed lubrication. All nanolubricants show very similar Stribeck curves, being the lowest friction coefficient obtained for 0.25 wt% of GnP. It has been found that for most of the experimental conditions the addition of the GnP promotes an increase of the film thicknessSpanish Ministry of Economy and Competitiveness, the European Regional Development Fund programme and the Xunta de Galicia have supported this manuscript through ENE2017-86425-C2-2-R, GRC ED431C 2020/10 and ED431E 2018/08 projects. Dr. María J. G. Guimarey acknowledges a postdoctoral fellowship from the Xunta de Galicia (Spain) and the financial support from IACOBUS programmeS

Accurate Measurements and Modeling of the PpT Behavior of Pure Substances and Natural Gas-Like Hydrocarbon Mixtures

The scale of the energy business today and a favorable and promising economic environment for the production of natural gas, requires study of the thermophysical behavior of fluids: sophisticated experimentation yielding accurate, new volumetric data, and development and improvement of thermodynamic models. This work contains theoretical and experimental contributions in the form of 1) the revision and update of a field model to calculate compressibility factors starting from the gross heating value and the mole fractions of diluents in natural gas mixtures; 2) new reference quality volumetric data, gathered with state of the art techniques such as magnetic suspension densimetry and isochoric phase boundary determinations; 3) a rigorous first-principles uncertainty assessment for density measurements; and 4) a departure technique for the extension of these experimental data for calculating energy functions. These steps provide a complete experimental thermodynamic characterization of fluid samples. A modification of the SGERG model, a standard virial-type model for prediction of compressibility factors of natural gas mixtures, matches predictions from the master GERG-2008 equation of state, using least squares routines coded at NIST. The modification contains new values for parametric constants, such as molecular weights and the universal gas constant, as well as a new set of coefficients. A state-of-the-art high-pressure, single-sinker magnetic suspension densimeter is used to perform density measurements over a wide range of temperatures and pressures. This work contains data on nitrogen, carbon dioxide, and a typical residual gas mixture (95% methane, 4% ethane, and 1% propane). Experimental uncertainty results from a rigorous, first-principles estimation including composition uncertainty effects. Both low- and high-pressure isochoric apparatus are used to perform phase boundary measurements. Isochoric P-T data can determine the phase boundaries. Combined with density measurements, isochoric data provides isochoric densities. Further mathematical treatment, including noxious volume and thermal expansion corrections, and isothermal integration, leads to energy functions and thus to a full thermodynamic characterization