Equilibrium conditions for clathrate hydrates formed from carbon dioxide or ethane in the presence of aqueous solutions of 1,4-dioxane and 1,3-dioxolane

Kinetic mechanisms of methane hydrate replacement and carbon dioxide hydrate reorganization

In this study, we reported the dissociation conditions for the carbon dioxide hydrate in the presence of cyclic ethers such as 1,3,5-Trioxane, 2,5-Dihydrofuran, 1,3-Dioxolane, and 3,4-Dihydro-2H-pyran. We measured the three phase (H-Lw-V) experimental data by using isochoric method. The experiments were conducted in the carbon dioxide + water + cyclic ethers in the pressure from 1.6 MPa to 3.5 MPa. All of them were conducted at 10 wt %. The experimental results showed that 1,3,5-Trioxane, 2,5-Dihydrofuran, and 1,3-Dioxolane could increase the carbon dioxide hydrate equilibrium temperature at about 5 K, 6.9 K, and 4.2 K respectively. The cyclic ethers of 1,3,5-Trioxane, 2,5-Dihydrofuran, and 1,3-Dioxolane in this study could promote the formation of carbon dioxide hydrate, and the promoting effect decreased in the following order: 2,5-Dihydrofuran > 1,3,5-Trioxane > 1,3-Dioxolane. However, 3,4-Dihydro-2H-pyran showed the totally different result in carbon dioxide system. 3,4-Dihydro-2H-pyran could inhibit the carbon dioxide hydrate formation. The average inhibit temperature is about 1.3 K.

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

ABSTRACTA laboratory‐scale batch reactor is built and operated to study the kinetic of formation of carbon dioxide hydrate in deionized water and sodium dodecyl sulfate (SDS) solutions. In this experimental work, the formation of carbon dioxide hydrate in deionized water (18 Ω) is investigated at fixed temperature of 273.65 K and different pressures of 20, 25, 30, and 35 bar, respectively. The formation of carbon dioxide hydrate in SDS solutions is investigated by using various concentrations of SDS up to 3000 ppm at temperature of 273.65 K and 35 bar. For carbon dioxide hydrate, the induction time decreases with the increase of initial carbon dioxide pressure because of the increase of subcooling and driving force in the system. Moreover, experimental results show that the addition of SDS reduces the induction time required for hydrate formation and significantly increases the carbon dioxide uptake, and these effects are concentration dependent. Furthermore, the addition of SDS in the hydrate‐forming systems has been shown to improve the apparent rate constant of the system. These results show that SDS shows a good promise to be used as low‐dosage hydrate promoter to improve the efficiency of gas hydrate‐based processes. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Experiment and model investigation of D-sorbitol as a thermodynamic hydrate inhibitor for methane and carbon dioxide hydrates

Effects of additive mixtures (THF/SDS) on carbon dioxide hydrate formation and dissociation in porous media

Generation laws and distribution characteristics of carbon dioxide hydrate in a reaction kettle

The processes of breaking, solution, and formation of hydrates behind a shock wave of moderate amplitude were studied experimentally in water with carbon dioxide bubbles under different initial static pressures. It is shown that an increase in the static pressure in a gas-liquid medium leads to reduction of critical relative amplitude of the shock wave, corresponding to starting development of Kelvin — Helmholtz instability and bubble splitting into small gas inclusions behind the shock wave front. It is shown that the rates of carbon dioxide solution and hydrate formation behind the shock wave front are close by the value; their dependences on medium and wave parameters are determined. Calculations by the model of gas hydration behind the shock wave are presented.

Inhibition effect of amino acids on carbon dioxide hydrate

ABSTRACTWe report in this study the dissociation conditions for the carbon dioxide hydrate in the presence of additive materials. We measured the hydrate-water-vapor (H-Lw-V) three-phase equilibrium data using the isochoric method. Examples of these phase equilibrium data for the additive materials of 1,3,5-trioxane, 2,5-dihydrofuran, 1,3-dioxolane, and 3,4-dihydro-2H-pyran are presented. The experimental pressure range is from 1.6 to 3.3 MPa, and the concentration of each additive is at 10 wt%. The experimental results indicate that cyclic ethers of 1,3,5-trioxane, 2,5-dihydrofuran, and 1,3-dioxolane promote the formation of carbon dioxide hydrate. Their promotion effects at a given pressure are up to 5 K, 6.9 K, and 4.2 K, respectively, The additive material of 3,4-dihydro-2H-pyran, however, shows the inhibitor behavior. The average inhibition effect is about 1.3 K at a given pressure.

Incipient equilibrium hydrate formation conditions for hydrogen sulfide, carbon dioxide, and ethane in aqueous solutions of ethylene glycol and sodium chloride were experimentally obtained in the temperature range 264−290 K and the pressure range 0.23−3.18 MPa. A variable-volume sapphire cell was used for the measurements.

Experimental study on the effect of pore size on carbon dioxide hydrate formation and storage in porous media

The mechanism of replacement of methane by carbon dioxide in the hydrate in the process of CO2 injection into a reservoir with formation of fronts of methane hydrate dissociation and carbon dioxide hydrate generation is investigated. It is found that such a replacement regime can be implemented in both low- and high-permeability reservoirs. It is shown that in the highintensity injection regime the heat flux from the well does not affect propagation of the fronts of methane hydrate dissociation and carbon dioxide hydrate generation. In this case the replacement regime is maintained by only the heat released at formation of carbon dioxide hydrate. An increase in the injection pressure may lead to suppression of methane hydrate dissociation and termination of the replacement reaction. The critical diagrams of existence of the regime of conversion of methane hydrate to carbon dioxide hydrate are constructed.

Sequestration of carbon dioxide (CO2) in gas hydrate and its disposal in shallow sediments under hydrate stability conditions is an efficient way of reducing carbon dioxide emission to the atmosphere. Laboratory modelling of carbon dioxide hydrate formation in freezing and frozen sand demonstrates that sediments within and below permafrost are potentially suitable reservoirs in this respect. The experiments are conducted in high-pressure cells with automatic pressure and temperature monitoring during hydrate formation in ice-bearing sand samples saturated with carbon dioxide at constant negative temperatures of −1°C to −8°С. The work includes testing the sensitivity of pore carbon dioxide formation to temperature, cyclic freezing/thawing, and initial ice saturation. According to experimental evidence, pore carbon dioxide hydrate can form in a large range of negative temperatures, while pore moisture can be liquid or solid. Hydrate formation accelerates when the samples are exposed to cyclic freezing and thawing. The formation of carbon dioxide hydrate is most active in the 45%–65% range of initial ice saturation. The results have implications for possible patterns of carbon dioxide hydrate formation in permafrost by injection of carbon dioxide into the zone of hydrate stability and for respective permafrost responses.

Gas hydrates are crystalline structures formed by water molecules and compounds of low molecular weights, being formed under suitable conditions of pressure and temperature. Although initially considered as inconveniences to the natural gas industries, they are currently considered as promising alternatives for solving some important global issues, such as contributing to the reduction of effects caused by the greenhouse gases. This concern related to the control of emissions of polluting gases has mobilized hundreds of countries that, at the United Nations Climate Change Conference (COP), agreed to reduce emissions of carbon dioxide and other gases by 2100. However, despite several strategies in the reduction of carbon dioxide emissions have been proposed, many rely on political incentives and substantial investments to convert pre-existing technologies to clean technologies, making such applicability and adaptability problematic. Thus, innovative Carbon Capture and Storage (CCS) techniques are being studied, which considers the use of gas hydrates formation to trap these gases, presents perspectives of lower costs and low environmental damages, promising to overcome the above mentioned problem, besides capturing and storing adequately the carbon dioxide and methane emitted. The need for robust evaluation of the thermodynamic equilibrium of hydrate-containing systems arises in order to make the proposal feasible and used on a large scale. The present work extensively solidifies this assessment of hydrate phase equilibria by proposing the isofugacity and Gibbs energy minimization criteria coupled to the nonlinear programming for the calculation of phase equilibria in the formation of methane and carbon dioxide hydrates. The Soave-Redlich-Kong cubic equation (SRK) was used to calculate the liquid and gaseous phases, and the Van der Waals and Platteeuw models were used to describe the solid phase of the hydrate. The procedure was implemented in the General Algebraic Modeling System (GAMS) software and in the CONOPT3 solver, with some numerical procedures performed in Microsoft Office Excel. The comparison between the results obtained from the present study by the isofugacity criterion and experimental data has been carried out, allowing concluding the satisfactory prediction of the phase equilibria behavior of systems containing hydrates.