Ethane Hydrate Formation Research Articles

Accurate prediction of the interfacial tension of surfactant/fluid mixtures during gas hydrate nucleation: The case of SDS surfactant-based systems near ethylene hydrate formation region

Interfacial tension of surfactant/fluid mixtures are of the utmost interest for the oil and gas industries and, in particular, for designing and optimizing hydrate-based technologies. This work deals with the potential application of the Adaptive Neuro Fuzzy Inference System (ANFIS) for accurate prediction of interfacial tensions of aqueous solution of SDS surfactant/ethylene near ethylene hydrate formation region. The second objective of the work is to obtain other properties including critical micelle concentration (CMC) and the surface excess concentration by using predicted model. The predicted results are in excellent agreement with measured data over wide ranges of operating conditions with the absolute average deviation of 1.3491%.

A unified approach for description of gas hydrate formation kinetics in the presence of kinetic promoters in gas hydrate converters

The kinetic promoters have found wide applications in enhancing the rate of energy conversion and storage via gas hydrate formation processes. Effects of different kinetic promoters such as anionic surfactants sodium dodecyl sulfate (SDS), dodecylbenzene sulfonic acid (DBSA), and sodium dodecyl benzene sulfonate (SDBS); cationic surfactants, Cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB) and non-ionic surfactants, alkylpolyglucoside (APG), dodecyl polysaccharide glycoside (DPG), TritonX-100 (TX100) on methane (CH4), ethane (C2H6) and propane (C3H8) gas hydrate formation processes are investigated in this work. A macroscopic kinetic model based on the time variations of reaction chemical potential is also presented for global description of gas hydrate formation processes. Experimental gas hydrate formation data are employed to validate the proposed kinetic model. Effects of promoter’s concentrations and agitation intensities on the gas consumption profiles are also investigated. A universal correlation and a unified kinetic map have been proposed for macroscopic description of gas hydrate formation kinetics in the presence or absence of kinetic promoters. According to the presented unified kinetic map, a unique region of gas hydrate formation is identified for the first time. For negligible amounts of kinetic promoters, the presented region disappears and approaches to a unique path at high agitation intensities. The presented unified approach is very useful for global understanding of gas hydrate formations processes in the absence or presence of kinetic promoters.

Equilibrium of Ethane Hydrate Formation in Carbon Pores

The formation of hydrates in carbon pores was utilized to store natural gas, and ethane is the second major component of natural gas; therefore, ethane hydrate formation in carbon pores is studied in comparison with that of methane. Ethane is a major raw material of ethylene in the petrochemical industry; therefore, its mixture with ethylene is of importance and the formation condition of ethane hydrates was compared also with that of ethylene. The equilibrium isotherms of ethane on wet carbons with different water contents as well as the isotherms for different temperatures were collected, from which the formation pressures of ethane hydrates as well as the enthalpy change of ethane hydrate formation were determined. It was shown that the largest volumetric capacity for ethane storage is observed at the water load that just about fully fills pore spaces. Ethane hydrates were formed in wet activated carbons at about same pressures as in water media and the formation pressure is much lower than that required for methane hydrates formation.

Metastability of Ethane Clathrate Hydrate Induced by [Co(NH3)6]3+Complex

The metal complex of [Co(NH 3 ) 6 ] 3+ is introduced to C 2 H 6 hydrate to confirm its possible inclusion in hydrogen-bonded water cages and the occurrence of metastable structure. The 13 C NMR spectra of C 2 H 6 +([Co(NH 3 ) 6 ]Cl 3 + 6NaOH in D 2 O) hydrate confirmed a new peak at 6.5 ppm matching with C 2 H 6 in sII-L cages. The retarded appearance of metastable sII phase is due to brine rejection of the cobalt complex occurring during solution freezing. The anions of OH and F were found to be incorporated in the host water cage framework, providing proton-deficient sites. The ionic conductivity of the frozen [Co(NH 3 ) 6 ] 3+ solution increased up to 20-fold after ethane hydrate formation, implying the incorporation of F ― into the host lattice. A notable finding of this work is that the metastability occurs only when the cobalt complex is in the presence of anions such as OH ― and F ― .

Modeling of methane and ethane hydrate formation kinetics based on non-equilibrium thermodynamics

In this study, experimental data of the kinetics of methane and ethane hydrate formation at constant volume were collected. The experiments were carried out in a batch reactor at different temperatures and pressures. The property of chemical affinity was used in the modeling of hydrate formation rate in a constant volume process. In this model a macroscopic driving force was defined which only needed the initial (experimental condition, temperature, and pressure) and final conditions (equilibrium conditions); thus, this model did not have the limitations of microscopic models, such as heat and mass transfer coefficients or population of particles, which may differ for each experiment. The experiments were carried out at temperatures 273, 274, 275.5, and 276 K for methane and 272, 273, 274, and 275 K for ethane with different initial pressures. The parameters of the model, Ar and tK, were obtained for each experiment, and the results show that the parameter of for each gas has a constant value. Subsequently, parameters of the model were used to predict experimental data and the variation of pressures with time. The results indicated that this model can well predict constant volume experimental data for crystals I hydrate former.

Study of the Kinetics and Morphology of Gas Hydrate Formation

The kinetics and morphology of ethane hydrate formation were studied in a batch type reactor at a temperature of ca. 270–280 K, over a pressure range of 8.83–16.67 bar. The results of the experiments revealed that the formation kinetics were dependant on pressure, temperature, degree of supercooling, and stirring rate. Regardless of the saturation state, the primary nucleation always took place in the bulk of the water and the phase transition was always initiated at the surface of the vortex (gas-water interface). The rate of hydrate formation was observed to increase with an increase in pressure. The effect of stirring rate on nucleation and growth was emphasized in great detail. The experiments were performed at various stirring rates of 110–190 rpm. Higher rates of formation of gas hydrate were recorded at faster stirring rates. The appearance of nuclei and their subsequent growth at the interface, for different stirring rates, was explained by the proposed conceptual model of mass transfer resistances. The patterns of gas consumption rates, with changing rpm, have been visualized as due to a critical level of gas molecules in the immediate vicinity of the growing hydrate particle. Nucleation and decomposition gave a cyclic hysteresis-like phenomena. It was also observed that a change in pressure had a much greater effect on the rate of decomposition than it did on the formation rate. Morphological studies revealed that the ethane hydrate resembles thread or is cotton-like in appearance. The rate of gas consumption during nucleation, with different rpm and pressures, and the percentage decomposition at different pressures, were explained precisely for ethane hydrate.

Kinetic inhibitor of hydrate crystallization.

We present the results of a combined theoretical/experimental study into a new class of kinetic inhibitor of gas hydrate formation. The inhibitors are based on quaternary ammonium zwitterions, and were identified from a computational screen. Molecular dynamics simulations were used to characterize the effect of the inhibitor on the interface between a type II hydrate and natural gas. These simulations show that the inhibitor is bifunctional, with the hydrophobic end being compatible with the water structure present at the hydrate interface, while the negatively charged functional group promotes a long ranged water structure that is inconsistent with the hydrate phase; the sulfonate-induced structure was found to propagate strongly over several solvation shells. The compound was subsequently synthesized and used in an experimental study of both THF and ethane hydrate formation, and was shown to have an activity that was comparable with an existing commercial kinetic inhibitor: PVP.

Equilibrium Data for Methane, Ethane, and Propane Incipient Hydrate Formation in Aqueous Solutions of Ethylene Glycol and Diethylene Glycol

Equilibrium experimental data for methane, ethane, and propane incipient hydrate formation in the presence of diethylene glycol and that for propane in the presence of ethylene glycol were obtained. Forty-six experiments were performed in the temperature and pressure ranges (264 to 283) K and (0.181 to 4.5) MPa, respectively, using the pressure search method. The experimental data were compared with predictions made using a hydrate equilibrium calculation method. The average deviation between the experimental data and calculated values was found to be 4.91%.

Effect of polyethylene oxide on gas hydrate phase equilibria

Englezos P. and Ngan Y.T., 1994. Effect of polyethylene oxide on gas hydrate phase equilibria. Fluid Phase Equilibria, 92: 271-288. Incipient phase equilibrium data for methane, ethane and propane hydrate formation in aqueous solutions of polyethylene oxide (PEO) were measured. The experiments were performed in the temperature range of 273.55–285.3 K. The range of measured incipient equilibrium hydrate formation pressures was 0.187–9.961 MPa. Aqueous polyethylene oxide solutions at 5, 15 and 25 wt.% were used. The results indicate a very weak inhibiting effect compared with the effect of electrolytes and alcohols on the equilibrium hydrate formation conditions. The measured equilibrium hydrate formation pressures were compared with the predictions from the existing gas hydrate equilibria prediction method. The data were found to be in good agreement with the predicted values.

Experimental study on the equilibrium ethane hydrate formation conditions in aqueous electrolyte solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExperimental study on the equilibrium ethane hydrate formation conditions in aqueous electrolyte solutionsP. Englezos and P. R. BishnoiCite this: Ind. Eng. Chem. Res. 1991, 30, 7, 1655–1659Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July 1991https://doi.org/10.1021/ie00055a038RIGHTS & PERMISSIONSArticle Views355Altmetric-Citations65LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (579 KB) Get e-Alerts Get e-Alerts

Kinetics of ethane hydrate formation

The kinetics of ethane hydrate formation after commencement of nucleation were studied at temperatures from 274 to 282 K over a pressure range of 0.6–2.6 MPa. Gaseous ethane was reacted with liquid water in a semi-batch stirred tank reactor. The results of the experiments revealed that the reaction rates were governed by the same kinetic parameters as those found for the methane hydrate formation, i.e. interfacial area, pressure, temperature and degree of supercooling. A semi-empirical model was used to correlate the experimental data.