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Methane from Gas Hydrates
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
Methane clathrates (hydrates) are commonly formed during natural gas production operations, when liquid water is condensed in the presence of methane at high pressure. It is known that larger hydrocarbon molecules such as ethane and propane can also form hydrates, although these are not as stable as methane hydrates. Once formed, hydrates can block pipeline and processing equipment. They are generally removed by (1) reduction of the pressure, (2) addition of heat, or (3) dissolving them using chemicals such as methanol and ethylene glycol. Care must be taken to ensure that the removal of the hydrates is carefully controlled, because as the hydrate undergoes phase transition, the release of water and methane can occur at very high rates. The rapid release of methane gas in a closed system can result in a rapid increase in pressure [104,105], which can be harmful to the drilling operation. In recent years, hydrate formation during drilling operation is controlled with the use of kinetic hydrate inhibitors [96–99,113–116], which dramatically slow the rate of hydrate formation and anti-agglomerates, which prevent hydrates from sticking together to block pipes and other parts of equipment.
Natural Gas
Published in Roy L. Nersesian, Energy Economics, 2016
Clathrate compounds are water molecules that under certain conditions bond to form an ice-like cage that encapsulates a gas molecule, which if methane is called methane hydrate.137 Methane hydrates are essentially natural gas molecules trapped in a lattice of ice whose structure is maintained in a low-temperature and moderate-to-high pressure environment. Methane hydrates can be shaped into an ice ball like those carefully sculpted by Calvin in the “Calvin and Hobbs” comic strip to throw at Suzie. The only difference is that a methane hydrate ice ball can be ignited. One cubic meter of methane hydrates contains enough embedded natural gas that, when released, expands to an incredible 160 cubic meters at atmospheric pressure.
Renewables—The Future’s (only) Hope!
Published in Anco S. Blazev, Energy Security for The 21st Century, 2021
Here we discuss energy resources that have been around for billions of years, but are yet to be discovered and explored. These are the mysterious and little known methane hydrates, also called hydrocarbon clathrates — natural gas-like, intermolecular compounds that occur naturally in submarine continental margins and regions and predominantly in the arctic permafrost. They are also expected to be found within medium- to large-sized icy moons of the outer solar system and in the polar regions of Mars.
Molecular dynamics simulation for studying the stability of structure H clathrate-hydrates of argon and large guest molecules
Published in Journal of Dispersion Science and Technology, 2018
Pourya Reshadi, Hamid Modarress, Bahram Dabir, Sepideh Amjad-Iranagh
Depending on the size of guest molecules and their properties, clathrate-hydrates generally form into one of three different structures: cubic structure I (sI),[9] face-centered cubic structure II (sII)[10] and hexagonal structure H (sH),[11] which differ in the number and type of cages found in the unit cell of the crystal structure. The cubic sI with a lattice parameter of 12.05 Å has two types of cages in its unit cell: two 512 (small) and six 51262 (large) cages. The 512 cage (pentagonal dodecahedral) is composed of 20 water molecules with 12 pentagonal rings of water, whereas the 51262 (tetrakaidecahedral) cage is formed by 24 water molecules and has 12 pentagonal and two hexagonal rings of water. Similarly, sII has cubic structure with lattice parameter 17.3 Å and its unit cell includes sixteen 512 (small) and eight 51264 (large) cages of water. Unlike I and II structures, H forms the hexagonal structure and its unit cell has the lattice parameters of a = b = 12.2 Å and c = 10.1 Å and is composed of three different types of cages: three 512 (small), two 435663 (medium) and one 51268 (large) cages of water.[1]
Experimental study and modeling of the kinetics of gas hydrate formation for acetylene, ethylene, propane and propylene in the presence and absence of SDS
Published in Petroleum Science and Technology, 2019
Hamed Hashemi, Saeideh Babaee, Kaniki Tumba, Amir H. Mohammadi, Paramespri Naidoo, Deresh Ramjugernath
Gas hydrates, or clathrate hydrates, which are a type of clathrates, are crystalline inclusion compounds obtained when appropriately-sized liquid or gas molecules are encapsulated in cage-like structures consisting of hydrogen-bonded water molecules. For the same entrapped molecule (guest), the occupancy of the cages provided by water molecules (host), and the composition of the hydrate vary in accordance to temperature and pressure changes. Hence, gas hydrates can be regarded as non-stoichiometric compounds (Carroll 2009; Sloan and Koh 2008). The three common hydrate crystalline structures are named I, II and H, depending on the chemical nature and the size of the guest (Sloan and Koh 2008).
Predicting semiclathrate hydrates dissociation pressure using a rigorous machine learning approach
Published in Journal of Dispersion Science and Technology, 2020
Aminreza Hosseinzadeh, Abolfazl Mohammadi, Ebrahim Soroush
Clathrate hydrates, a subset of clathrate or inclusion compounds, are non-stoichiometric ice-like crystalline solids composed of water molecules and appropriate guest molecules like CO2, CO, N2, O2, H2, and CH4, which are form in low temperatures and specific pressures.[1–3] The water molecules due to hydrogen bonding form lattice or cage structures with large and small cavities, which are host to the gas molecules that have smaller molecular diameters than the cavities. Subsequently, the structure that is thermodynamically unstable, become stable and clathrate hydrates are form.