Experimental study and thermodynamic modeling of CO 2 gas hydrate formation in presence of zinc oxide nanoparticles

Gas hydrates are the foremost flow assurance issue in deep water operations. Since heat transfer is a limiting factor in gas hydrate formation processes, a better understanding of its relation to hydrate formation is important. This work presents findings from experimental study of the effect of gas hydrate content on heat transfer through a cylindrical wall. The experiments were carried out at temperature conditions similar to those encountered in flowlines in deep water conditions. Experiments were conducted on methane hydrate, Tetrahydrofuran hydrate, and ethylene oxide hydrate respectively in stirred cylindrical high pressure autoclave cells. Methane hydrate was formed at 90 bars (pressure), and 8°C, followed by a cooling/heating cycle in the range of 8°C → 4°C → 8°C. Tetrahydrofuran (THF) and ethylene oxide (EO) hydrates were formed at atmospheric pressure and system temperature of 1°C in contact with atmospheric air. This was followed by a heating/cooling cycle within the range of 1°C → 4°C → 1°C, since the hydrate equilibrium temperature of THF hydrate is 4.98°C in contact with air at atmospheric pressure. The experimental conditions of the latter hydrate formers were more controlled, given that both THF and EO are miscible with water. We found in all cases a general trend of decreasing heat transfer coefficient of the cell content with increasing concentration of hydrate in the cell, indicating that hydrate formation creates a heat transfer barrier. The hydrate equilibrium temperature seemed to change with a change in the stoichiometric concentration of THF and EO. While the methane hydrate cooling/heating cycles were performed under quiescent conditions, the effect of stirring was investigated for the latter hydrate formers.

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Prediction of Methane and Ethane Gas Hydrate Formation and Their Mixture in a Porous Medium

Archives of Industrial Engineering ◽

10.31829/2637-9252/aie2019-2(1)-109 ◽

2019 ◽

pp. 1-16

Keyword(s):

Porous Medium ◽

Porous Media ◽

Thermodynamic Modeling ◽

Gas Hydrate ◽

Pore Diameter ◽

Laboratory Data ◽

Hydrate Formation ◽

Equilibrium Temperature ◽

Formation Temperature ◽

Gas Hydrate Formation

The purpose of this paper is to study the thermodynamic modeling of the conditions for methane and ethane gas hydrate formation and their mixtures in a porous and non-porous environment. In this paper, the Van der Waals- Platteeuw thermodynamic model was used for prediction of gas hydrate formation conditions. Also, the SRK and PTV equations of state were used for calculations of driving force. In this research, the results of thermodynamic modeling in a porous were compared with the non-porous environment and laboratory data in the literature. Studies have shown that the results of the modeling are in good agreement with the laboratory data and the percentage of errors is low. The results also showed that with increasing pressure of porous and non-porous media, the equilibrium temperature increases. In addition, the effect of the pore diameter of porous media on the results of modeling was investigated for methane, ethane and their mixtures during gas hydrates formation. The results showed that by increasing the pressure for any size of the pore diameter of the porous medium, hydrate formation temperature increases. In addition, by increasing the pore diameter of the porous medium, hydrate formation temperature methane, ethane and their mixture increase at a constant pressure. The results also showed that the equilibrium temperature of the non-porous medium is higher than the equilibrium temperature of the non-porous medium. This shows that the hydrate formation in the porous medium has a deterrent effect and leads to lower temperatures and higher temperatures conditions for gas hydrate formation. The results showed that by increasing the percentage of methane in a porous or non-porous medium, the temperature of hydrate formation of the binary gas mixture of methane and ethane decreases.

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