scholarly journals Hydrate—A Mysterious Phase or Just Misunderstood?

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 880 ◽  
Author(s):  
Bjørn Kvamme ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Navid Saeidi
Keyword(s):  
Pure Water ◽  
Hydrate Formation ◽  
Free Water ◽  
Mineral Surfaces ◽  
Dual Roles ◽  
Hydrate Reservoir ◽  
Nucleation Sites ◽  
Stability Limits ◽  
Real Stability ◽  
Non Equilibrium

Hydrates that form during transport of hydrocarbons containing free water, or water dissolved in hydrocarbons, are generally not in thermodynamic equilibrium and depend on the concentration of all components in all phases. Temperature and pressure are normally the only variables used in hydrate analysis, even though hydrates will dissolve by contact with pure water and water which is under saturated with hydrate formers. Mineral surfaces (for example rust) play dual roles as hydrate inhibitors and hydrate nucleation sites. What appears to be mysterious, and often random, is actually the effects of hydrate non-equilibrium and competing hydrate formation and dissociation phase transitions. There is a need to move forward towards a more complete non-equilibrium way to approach hydrates in industrial settings. Similar challenges are related to natural gas hydrates in sediments. Hydrates dissociates worldwide due to seawater that leaks into hydrate filled sediments. Many of the global resources of methane hydrate reside in a stationary situation of hydrate dissociation from incoming water and formation of new hydrate from incoming hydrate formers from below. Understanding the dynamic situation of a real hydrate reservoir is critical for understanding the distribution characteristics of hydrates in the sediments. This knowledge is also critical for designing efficient hydrate production strategies. In order to facilitate the needed analysis we propose the use of residual thermodynamics for all phases, including all hydrate phases, so as to be able to analyze real stability limits and needed heat supply for hydrate production.

scholarly journals Stages in the Dynamics of Hydrate Formation and Consequences for Design of Experiments for Hydrate Formation in Sediments

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3399 ◽  
Author(s):  
Bjørn Kvamme ◽  
Richard B. Coffin ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Shouwei Zhou ◽  
...  
Keyword(s):  
Natural Gas ◽  
Mass Transport ◽  
Liquid Water ◽  
Transport Model ◽  
Hydrate Formation ◽  
Mineral Surfaces ◽  
Geological Time ◽  
Hydrate Reservoir ◽  
Hydrate Saturation ◽  
Mass Transport Model

Natural gas hydrates in sediments can never reach thermodynamic equilibrium. Every section of any hydrate-filled reservoir is unique and resides in a stationary balance that depends on many factors. Fluxes of hydrocarbons from below support formation of new hydrate, and inflow of water through fracture systems leads to hydrate dissociation. Mineral/fluid/hydrate interaction and geochemistry are some of the many other factors that determine local hydrate saturation in the pores. Even when using real sediments from coring it is impossible to reproduce in the laboratory a natural gas hydrate reservoir which has developed over geological time-scales. In this work we discuss the various stages of hydrate formation, with a focus on dynamic rate limiting processes which can lead to trapped pockets of gas and trapped liquid water inside hydrate. Heterogeneous hydrate nucleation on the interface between liquid water and the phase containing the hydrate former rapidly leads to mass transport limiting films of hydrate. These hydrate films can delay the onset of massive, and visible, hydrate growth by several hours. Heat transport in systems of liquid water and hydrate is orders of magnitude faster than mass transport. We demonstrate that a simple mass transport model is able to predict induction times for selective available experimental data for CO2 hydrate formation and CH4 hydrate formation. Another route to hydrate nucleation is towards mineral surfaces. CH4 cannot adsorb directly but can get trapped in water structures as a secondary adsorption. H2S has a significant dipole moment and can adsorb directly on mineral surfaces. The quadropole-moment in CO2 also plays a significant role in adsorption on minerals. Hydrate that nucleates toward minerals cannot stick to the mineral surfaces so the role of these nucleation sites is to produce hydrate cores for further growth elsewhere in the system. Various ways to overcome these obstacles and create realistic hydrate saturation in laboratory sediment are also discussed.

scholarly journals Small Alcohols as Surfactants and Hydrate Promotors

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 345
Author(s):  
Bjørn Kvamme
Keyword(s):  
Kinetic Modelling ◽  
Hydrate Formation ◽  
Formation Enthalpy ◽  
Mineral Surfaces ◽  
Surface Charges ◽  
Surrounding Water ◽  
Mole Percent ◽  
Bottle Neck ◽  
Stability Limits

Many methods to produce hydrate reservoirs have been proposed in the last three decades. Thermal stimulation and injection of thermodynamic hydrate inhibitors are just two examples of methods which have seen reduced attention due to their high cost. However, different methods for producing hydrates are not evaluated thermodynamically prior to planning expensive experiments or pilot tests. This can be due to lack of a thermodynamic toolbox for the purpose. Another challenge is the lack of focus on the limitations of the hydrate phase transition itself. The interface between hydrate and liquid water is a kinetic bottle neck. Reducing pressure does not address this problem. An injection of CO2 will lead to the formation of a new CO2 hydrate. This hydrate formation is an efficient heat source for dissociating hydrate since heating breaks the hydrogen bonds, directly addressing the problem of nano scale kinetic limitation. Adding limited amounts of N2 increases the permeability of the injection gas. The addition of surfactant increases gas/water interface dynamics and promotes heterogeneous hydrate formation. In this work we demonstrate a residual thermodynamic scheme that allows thermodynamic analysis of different routes for hydrate formation and dissociation. We demonstrate that 20 moles per N2 added to the CO2 is thermodynamically feasible for generating a new hydrate into the pores. When N2 is added, the available hydrate formation enthalpy is reduced as compared to pure CO2, but is still considered sufficient. Up to 3 mole percent ethanol in the free pore water is also thermodynamically feasible. The addition of alcohol will not greatly disturb the ability to form new hydrate from the injection gas. Homogeneous hydrate formation from dissolved CH4 and/or CO2 is limited in amount and not important. However, the hydrate stability limits related to concentration of hydrate former in surrounding water are important. Mineral surfaces can act as hydrate promotors through direct adsorption, or adsorption in water that is structured by mineral surface charges. These aspects will be quantified in a follow-up paper, along with kinetic modelling based on thermodynamic modelling in this work.

scholarly journals Novel Surfactant-Free Water Dispersion Technique of TiO2 NPs Using Focused Ultrasound System

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 427
Author(s):  
Seon Ae Hwangbo ◽  
Minjeong Kwak ◽  
Jaeseok Kim ◽  
Tae Geol Lee
Keyword(s):  
Tio2 Nanoparticles ◽  
Focused Ultrasound ◽  
Pure Water ◽  
Free Water ◽  
Dispersion Stability ◽  
Renewable Energy Resources ◽  
Water Dispersion ◽  
Dispersion State ◽  
Dispersion Technique

Titanium dioxide (TiO2) nanoparticles are used in a wide variety of products, such as renewable energy resources, cosmetics, foods, packaging materials, and inks. However, large quantities of surfactants are used to prepare waterborne TiO2 nanoparticles with long-term dispersion stability, and very few studies have investigated the development of pure water dispersion technology without the use of surfactants and synthetic auxiliaries. This study investigated the use of focused ultrasound to prepare surfactant-free waterborne TiO2 nanoparticles to determine the optimal conditions for dispersion of TiO2 nanoparticles in water. Under 395–400 kHz and 100–105 W conditions, 1 wt% TiO2 colloids were prepared. Even in the absence of a surfactant, in the water dispersion state, the nanoparticles were dispersed with a particle size distribution of ≤100 nm and did not re-agglomerate for up to 30 days, demonstrating their excellent dispersion stability.

scholarly journals Cyclopentadienone Iron Tricarbonyl Complexes-Catalyzed Hydrogen Transfer in Water

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 421 ◽  
Author(s):  
Daouda Ndiaye ◽  
Sébastien Coufourier ◽  
Mbaye Diagne Mbaye ◽  
Sylvain Gaillard ◽  
Jean-Luc Renaud
Keyword(s):  
Metal Complexes ◽  
Hydrogen Transfer ◽  
Low Cost ◽  
Pure Water ◽  
Free Water ◽  
Water Soluble ◽  
Tricarbonyl Complex ◽  
Reaction Conditions ◽  
Catalytic Systems ◽  
Iron Tricarbonyl

The development of efficient and low-cost catalytic systems is important for the replacement of robust noble metal complexes. The synthesis and application of a stable, phosphine-free, water-soluble cyclopentadienone iron tricarbonyl complex in the reduction of polarized double bonds in pure water is reported. In the presence of cationic bifunctional iron complexes, a variety of alcohols and amines were prepared in good yields under mild reaction conditions.

Improved thermal model considering hydrate formation and deposition in gas-dominated systems with free water

Fuel ◽  
2019 ◽  
Vol 236 ◽  
pp. 870-879 ◽  
Author(s):  
Zhiyuan Wang ◽  
Jing Yu ◽  
Jianbo Zhang ◽  
Shun Liu ◽  
Yonghai Gao ◽  
...  
Keyword(s):  
Thermal Model ◽  
Hydrate Formation ◽  
Free Water

Fractionation of Hydrogen Isotopes in Aqueous Lithium Chloride Solutions

1988 ◽  
Vol 43 (5) ◽  
pp. 449-453 ◽  
Author(s):  
Masahisa Kakiuchi
Keyword(s):  
Oxygen Isotope ◽  
Isotope Effect ◽  
Lithium Chloride ◽  
Structural Changes ◽  
Platinum Catalyst ◽  
Pure Water ◽  
Free Water ◽  
Hydrogen Gas ◽  
Water Molecules ◽  
Chloride Solutions

The D/H ratio of hydrogen gas in equilibrium with water vapor over aqueous lithium chloride solutions was measured at 25 °C, using a hydrophobic platinum catalyst. Experimental details are described. The hydrogen isotope effect between the solution and pure water depends linearly on the LiCl concentration up to ca. 12 m, and at higher concentrations a marked deviation from linearity takes place, as was also observed for the oxygen isotope effect measured by Bopp et al. On the basis of these hydrogen and oxygen isotope effects it is concluded that H218O is enriched in the water molecules coordinated to Li+ ions and HD16O is enriched in the free water molecules of the solution. The observed deviation from linearity for concentrations higher than ca. 12m is interpreted in terms of structural changes in the hydration sphere of the Li+ ions.

scholarly journals Why Should We Use Residual Thermodynamics for Calculation of Hydrate Phase Transitions?

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4135
Author(s):  
Bjørn Kvamme ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Wantong Sun ◽  
Mojdeh Zarifi ◽  
...  
Keyword(s):  
Natural Gas ◽  
Hydrate Formation ◽  
Reference Method ◽  
Temperature Stability ◽  
Heat Pumps ◽  
Ideal Gas ◽  
Thermodynamic Method ◽  
Hydrate Phase ◽  
Model Scheme ◽  
Non Equilibrium

The formation of natural gas hydrates during processing and transport of natural has historically been one of the motivations for research on hydrates. In recent years, there has been much focus on the use of hydrate as a phase for compact transport of natural gas, as well as many other applications such as desalination of seawater and the use of hydrate phase in heat pumps. The huge amounts of energy in the form of hydrates distributed in various ways in sediments is a hot topic many places around the world. Common to all these situations of hydrates in nature or industry is that temperature and pressure are both defined. Mathematically, this does not balance the number of independent variables minus conservation of mass and minus equilibrium conditions. There is a need for thermodynamic models for hydrates that can be used for non-equilibrium systems and hydrate formation from different phase, as well as different routes for hydrate dissociation. In this work we first discuss a residual thermodynamic model scheme with the more commonly used reference method for pressure temperature stability limits. However, the residual thermodynamic method stretches far beyond that to other routes for hydrate formation, such as hydrate formation from dissolved hydrate formers. More important, the residual thermodynamic method can be utilized for many thermodynamic properties involved in real hydrate systems. Consistent free energies and enthalpies are only two of these properties. In non-equilibrium systems, a consistent thermodynamic reference system (ideal gas) makes it easier to evaluate most likely distribution of phases and compositions.

scholarly journals Ice nucleation efficiency of clay minerals in the immersion mode

2012 ◽  
Vol 12 (13) ◽  
pp. 5859-5878 ◽  
Author(s):  
V. Pinti ◽  
C. Marcolli ◽  
B. Zobrist ◽  
C. R. Hoyle ◽  
T. Peter
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Differential Scanning Calorimeter ◽  
Pure Water ◽  
Nucleation Site ◽  
Ice Nucleation ◽  
Nucleation Sites ◽  
The One ◽  
Site Classes

Abstract. Emulsion and bulk freezing experiments were performed to investigate immersion ice nucleation on clay minerals in pure water, using various kaolinites, montmorillonites, illites as well as natural dust from the Hoggar Mountains in the Saharan region. Differential scanning calorimeter measurements were performed on three different kaolinites (KGa-1b, KGa-2 and K-SA), two illites (Illite NX and Illite SE) and four natural and acid-treated montmorillonites (SWy-2, STx-1b, KSF and K-10). The emulsion experiments provide information on the average freezing behaviour characterized by the average nucleation sites. These experiments revealed one to sometimes two distinct heterogeneous freezing peaks, which suggest the presence of a low number of qualitatively distinct average nucleation site classes. We refer to the peak at the lowest temperature as "standard peak" and to the one occurring in only some clay mineral types at higher temperatures as "special peak". Conversely, freezing in bulk samples is not initiated by the average nucleation sites, but by a very low number of "best sites". The kaolinites and montmorillonites showed quite narrow standard peaks with onset temperatures 238 K

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