Kinetic modelling of methane hydrate formation and agglomeration with and without anti-agglomerants from emulsion in pipelines

GasHyDyn : Logiciel de simulation de la composition et de la stabilité des hydrates de gazNational audienceOffshore systems mainly containing crude oil, natural gas and water operate at low temperature and high pressure which favour conditions for gas hydrate formation and agglomeration. Gas hydrate is a serious issue in flow assurance; it may cause many troubles, especially, plugging in oil and gas pipeline. This work is to intend to develop a kinetic model to predict gas hydrate formation, agglomeration and plugging in flowlines based on the experimental data obtained from Archimede Flowloop from the work of Mendes-Melchuna (2015). In this model, the mean droplet size of emulsion will be calculated from flow parameters to evaluate the surface area of droplets which are very critical parameters for kinetic model of gas hydrate formation in emulsion. It is important to note that anti-agglomerants (AAs) may modify the water-oil interfacial tension leading to smaller mean droplet size. A preliminary study of the emulsion formation and behaviour will contribute to a better understanding of the hydrates formation and agglomeration

Use of a predictive electrolyte equation of state for the calculation of the gas hydrate formation temperature in the case of systems with methanol and salts

International audienceAn electrolyte EOS based on Peneloux's non-electrolyte PR-EOS has been applied to the prediction of the temperature associated to the formation of gas hydrate from water-methanol-salts solutions. Original assumptions have been developed to allow the calculation of model ionic parameters from experimental solvation diameters. A mixing rule is used for the extension of the approach to water-methanol mixed solvents solutions. When applied to systems with CH4 and CO2 hydrates, the deviations between predicted equilibrium temperatures and calculated ones is less than I K over a wide range of conditions

Liquid–liquid equilibria of binary and ternary systems involving monoethyleneglycol, water, n-alkanes at three temperatures: 283.15, 303.15 and 333.15 K

International audienceNew solubility data of binary and ternary systems involving ethylene glycol (or MEG), water and n-alkanes (hexane, heptane, octane, nonane, undecane, dodecane and hexadecane) under atmospheric pressure at three temperatures 283.15, 303.15 and 333.15 K are reported. The reported values are original except for binary systems where some points were found in the literature for comparison. The non-random two-liquid (NRTL) were used to correlate the experimental data of the binary mixtures. The interaction parameters obtained with the experimental binary systems were used to predict the ternary systems

Liquid–Liquid Equilibria of Binary, Ternary, and Quaternary Systems Involving Monoethylene Glycol, Water, Toluene, p -Xylene, Hexane, and Octane

International audienceTo prevent gas hydrate formation and the plugging of the pipe, monoethylene glycol, MEG, is injected into the wellhead. To develop the thermodynamic model for the optimization of MEG injection, liquid–liquid equilibrium, LLE, studies are necessary. In the present work, original data are presented of binary, ternary, and quaternary systems involving MEG, water, hexane, octane, toluene, and p-xylene under atmospheric pressure and in the temperature range between 278.15 and 333.15 K. The NRTL thermodynamic model was used for the solubility prediction of binary, ternary, and quaternary systems. The adjustable parameters of the model were determined through regression of binary mixtures data from literature. Experimental and predicted solubilities are in a quite good agreement, in view of the low solubility data involved in the different systems

Impact of Associated Gases on Equilibrium and Transport Properties of a CO2 Stream: Molecular Simulation and Experimental Studies

International audienceDuring the various carbon dioxide capture and storage (CCS) stages, an accurate knowledge of thermodynamic properties of CO2 streams is required for the correct sizing of plant units. The injected CO2 streams are not pure and often contain small amounts of associated gaseous components such as O2,N2, SOx ,NOx , noble gases, etc. In this work, the thermodynamic behavior and transport properties of some CO2-rich mixtures have been investigated using both experimental approaches and molecular simulation techniques such as Monte Carlo and molecular dynamics simulations.Using force fields available in the literature,we have validated the capability of molecular simulation techniques in predicting properties for pure compounds, binary mixtures, as well as multicomponent mixtures. These validations were performed on the basis of experimental data taken from the literature and the acquisition of new experimental data. As experimental data and simulation results were in good agreement, we proposed the use of simulation techniques to generate new pseudoexperimental data and to study the impact of associated gases on the properties of CO2 streams. For instance, for a mixture containing 92.0mol% of CO2, 4.0mol% of O2, 3.7mol% of Ar, and 0.3mol% of N2, we have shown that the presence of associated gases leads to a decrease of 14% and 21% of the dense phase density and viscosity, respectively, as compared to pure CO2 properties

Liquid–Liquid Equilibria at Three Temperatures (between 280.15 K and 333.15 K) of Binary, Ternary, and Quaternary Systems Involving Monoethylene Glycol, Water, Cyclohexane, para -Xylene, trans - and cis -Dimethylcyclohexane, and trans - and cis -Decahydronaphthalene

International audienceNew solubility data for binary (ethylene glycol (or MEG) + cyclohexane or para-xylene), ternary (MEG/water + cyclohexane or para-xylene), and quaternary systems (MEG/water + trans- and cis-1,2-dimethylcyclohexane or trans- and cis-decahydronaphthalene (decalin)) under atmospheric pressure at three temperatures between 280.15 K and 333.15 K are reported. No literature data was available to compare with the present study. The consistency of the experimental data was checked through an Othmer–Tobias plot. The nonrandom two-liquid (NRTL) and the Soave–Redlich–Kwong modified (SRKM) thermodynamic models were used to correlate the experimental liquid–liquid equilibrium (LLE) data for all of the studied systems

Experimental procedure and results to measure the composition of gas hydrate, during crystallization and at equilibrium, from N₂-CO₂-C₂H₆-C₃H₈-C₄H₁₀ gas mixtures

PosterInternational audienceGas hydrates are of great interest in petroleum industry. They are especially a flow assurance issue in deep offshore oilfields. In this study, an experimental work concerning the equilibrium of gas hydrates of light hydrocarbon molecules is proposed. 12 experiments from N2-CO2-CH4-C2H6-C3H8-C4H10 gas mixtures in temperature range of [0.8-19°C] and pressure range of [1.4 - 66bars] have been carried out. 78 equilibrium points have been measured following two procedures. The first and main procedure (71 equilibrium data) corresponds to a procedure at high crystallization rate (high supersaturation, or high &#916P). The objective of this first procedure is to study the gas hydrates formation in usual dynamic conditions (start-up or reboot of an exploitation). The second procedure corresponds to a procedure at very low crystallization rate (7 data). The objective of this second procedure is to anticipate a further study about the thermodynamic or kinetic involvement in hydrate formation. It might also be closer to the conditions along a pipe-line at steady state. In this article, for all the points and procedures, the PT data are given. Also, the hydrate phase molar compositions are given for most of the measured equilibria

Enthalpy and Heat Capacity Changes on Mixing: Fundamental Aspects and Prediction by Means of the PPR78 Cubic Equation of State

The PPR78 model is a predictive cubic equation of state relying on the group-contribution concept. Our previous studies have highlightened its capacity to predict the phase behavior of mixtures containing a large variety of compounds: alkanes, alkenes, aromatic compounds, permanent gases, sulfur compounds, etc. In this paper, it is attempted for the first time to answer the question “<i>can the PPR78 model be safely used in energy-rate balances?</i>”. To do so, the largest possible number of enthalpy of mixing data and isobaric heat capacity of mixing data were collected in the open literature and predicted using the PPR78 model. It is shown that although certainly perfectible, this model generally provides from acceptable to accurate estimations of these properties depending on the nature of the mixtures and the conditions of temperature and pressure as well. Furthermore, this paper proposes some general reflections both on conceptual and practical issues: Is it always possible to claim that the excess enthalpy and the enthalpy of mixing are two strictly equivalent quantities? Does an equation of state have the same capacity to reproduce enthalpy of mixing data in one-phase and in two-phase regions? Which criterion should be used for evaluating the accuracy of an equation of state in terms of energy-rate balances

Liquid–Liquid Equilibria of Binary and Ternary Systems Methanol/Water + n -Hexane, + n -Octane, + n -Dodecane, and + n -Hexadecane in the Temperature Range between T = 283.15 K and T = 333.15 K

International audienceOriginal very low solubility data for binary (methanol + dodecane) and ternary systems (methanol/water + hexane, or octane, or dodecane, or hexadecane) under atmospheric pressure at three temperatures between 283.15 and 333.15 K are reported. The experimental values were compared with literature data when available. Two models (NRTL and UNIQUAC) were used to correlate and predict the experimental data