Hydrate Dissociation Pressures Research Articles

CO2 solubility in aqueous solution of salts: Experimental study and thermodynamic modelling

AbstractThere are many economic obstacles and complex engineering problems associated with CO2 capture and storage in saline aquifers that need to be addressed. Overcoming such challenges requires precise knowledge on the fluid phase equilibria of CO2‐brine systems. Having accurate CO2 solubility data over a wide range of temperature and pressure can greatly assist in resolving these obstacles by improving the performance and accuracy of the thermodynamic modeling and subsequent CCS engineering success.CO2 solubility in pure water and NaCl solutions has been widely studied in the literature, however, there is a lack of data on CO2 solubility at lower temperatures (below 298 K). Furthermore, limited phase equilibria data are available for CO2 solubility in CaCl2, MgCl2, and KCl solutions at elevated temperatures (i.e., T > 323.15 K).In this work, the phase equilibria of CO2 and brine systems are investigated experimentally and theoretically. In this study, solubilities of CO2 in pure water and various concentrations of NaCl (10, 15, 20, and 22 wt%), KCl (10, 15, and 22 wt%), CaCl2 (7.5, 10, 15.7, and 23.4 wt%), and MgCl2 (6.7, 11, 18, and 29 wt%) aqueous solutions are reported. All CO2 solubilities were measures at 323.15, 373.15, and 423.15 K and over various pressure ranges, while solubilities in 10 and 20 wt% NaCl aqueous solutions were also measured over the temperature range of 263 to 298 K and pressures up to the hydrate dissociation pressure of each system. Equation of state modelling using the PC‐SAFT and the Cubic Plus Association equations of state, is performed in the theoretical part of the study to validate the measured solubility data. © 2024 The Author(s). Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Evaluation of the perturbed hard-sphere-chain equation of state for calculations of methane hydrate formation condition in the presence of ionic liquids

This work aims to evaluate the performance of the Perturbed Hard-Sphere-Chain (PHSC) equation of state (EoS) for the calculation of methane hydrate formation in the presence of ionic liquids (ILs). The van der Waals and Platteeuw model is utilized to calculate the hydrate dissociation pressure. The performance of the PHSC model is compared to cubic EoSs and the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) model. Two activity coefficient models are used to estimate the water activity in the presence of ILs. The results show that PHSC EoS with an activity coefficient model provides lower average error values (lower than 2%) and changing the activity coefficient models does not have a great effect on reducing the error. Also, the results of cubic-based EoSs are quite remarkable considering their simplicity. The PHSC model can be utilized as a robust and efficient thermodynamic model for hydrate dissociation pressure calculation in the presence of IL.

Experimental measurement and thermodynamic modeling of hydrate stability conditions in the methane + cyclopentane + tetra-n‑butyl ammonium chloride (TBAC) aqueous solution system

The present study investigates hydrate dissociation conditions in methane + cyclopentane (CP) and tetra-n‑butyl ammonium chloride (TBAC) aqueous solution. The experimental work was done using an isochoric vessel with varying compositions of the promoters in the pressure and temperature ranges of (1.42 to 4.90) MPa and (291.2 to 298.9) K, respectively. The methane hydrate dissociation pressure was predicted by the Gibbs minimization method. The findings denote that adding CP to the TBAC-containing system shifts the hydrate dissociation temperature of methane to higher values. The results also show an average increase of 12, 9, 5, and 3 K in hydrate dissociation temperature for 5, 10, 20, and 30 wt% TBAC in aqueous solution within the pressures. These results can be caused by the existence of more dodecahedral cages that are inhabited by methane. Thus, it makes hydrates more stable and increases the temperature of hydrate dissociation. On the other hand, adding TBAC to CP containing system has an inhibitor effect. The methane hydrate dissociation temperature was not changed sensibly when a 5 wt% TBAC was added to CP containing system. When the addition of the TBAC weight percentage to CP containing system is increased to 10, the average hydrate dissociation temperature decreases by 1 K within the pressures. When adding 20 and 30 wt% TBAC to CP containing system an average decrease of 2 K and 3 K in the hydrate dissociation temperature is resulted, respectively, within the pressures. The reduction in the hydrate dissociation temperatures can be attributed to salting-out and ion clustering. The experimental data and modeling results for the hydrate dissociation pressures exhibit an AARD of 2.4 %.

Evaluation of a Simplified Model for Three-Phase Equilibrium Calculations of Mixed Gas Hydrates

In this study, we perform an extensive evaluation of a simple model for hydrate equilibrium calculations of binary, ternary, and limited quaternary gas hydrate systems that are of practical interest for separation of gas mixtures. We adopt the model developed by Lipenkov and Istomin and analyze its performance at temperature conditions higher than the lower quadruple point. The model of interest calculates the dissociation pressure of mixed gas hydrate systems using a simple combination rule that involves the hydrate dissociation pressures of the pure gases and the gas mixture composition, which is at equilibrium with the aqueous and hydrate phases. Such an approach has been used extensively and successfully in polar science, as well as research related to space science where the temperatures are very low. However, the particular method has not been examined for cases of higher temperatures (i.e., above the melting point of the pure water). Such temperatures are of interest to practical industrial applications. Gases of interest for this study include eleven chemical components that are related to industrial gas-mixture separations. Calculations using the examined methodology, along with the commercial simulator CSMGem, are compared against experimental measurements, and the range of applicability of the method is delineated. Reasonable agreement (particularly at lower hydrate equilibrium pressures) between experiments and calculations is obtained considering the simplicity of the methodology. Depending on the hydrate-forming mixture considered, the percentage of absolute average deviation in predicting the hydrate equilibrium pressure is found to be in the range 3–91%, with the majority of systems having deviations that are less than 30%.

Multiphysical evolution and dynamic competition involved in natural gas hydrate dissociation in porous media and its implications for engineering

Hydrate (shorted for natural gas hydrate) is one of the most promising future energies, and dissociating hydrate in situ is commonly recognized as the best strategy to realize commercial exploitation. So it is significant to understand the fundamental mechanism in the process of hydrate dissociation involving complicated thermal-hydraulic-mechanical-chemical phenomena. To date, the multiphysical evolution patterns are not revealed by the overall comparison among different phenomena, and we still have little knowledge on the contributions of different influence factors to hydrate dissociation rate. More importantly, the fundamental study has a considerable gap to the real engineering. Therefore, in this paper, a fully-coupled thermal-hydraulic-mechanical-chemical model is developed to further analyze the evolution of all phenomena from both global and local perspectives and find the coupled relationships among physical/chemical phenomena from a dynamic competition perspective. Results show that the global spatial distributions of pressure, hydrate saturation and strain show one simple pattern during hydrate dissociation，while those of temperature and hydrate dissociation rate manifest four and three complex patterns respectively. The effective hydrate reaction specific area, reaction coefficient and pressure difference play different roles in the domination of the trend and value of hydrate dissociation rate. Additionally, two examples are given to demonstrate the implications of the fundamental mechanism to the engineering. A negative-power-law relation is found between the finish time of hydrate dissociation and the heat transfer coefficient of outside heat source (geothermal heat in real engineering). A good linear relation between hydrate dissociation front and pressure transfer front is found, which provides a possible easy way to predict the range of dissociated hydrate by pressure in the real engineering.

Unraveling the complex pressure propagation of two-time depressurization production in Shenhu hydrate reservoir: Insights for long-term exploitation

Depressurization serves as the primary method for exploiting marine hydrate reservoirs, and understanding the long-term pressure propagation efficiency and identifying the potential limiting factors are crucial for enhancing and optimizing this approach. In this study, we employed numerical modeling to simulate two-time depressurization exploitation in the Shenhu hydrate reservoir, aiming to predict the long-term gas production and pressure propagation efficiency under various depressurization schemes. Our simulation results indicate: 1) The pressure propagates rapidly near the wellhead and gradually decelerates with distance due to the impeding influence of the reservoir's low intrinsic permeability and groundwater seepage in the covering strata. 2) Pressure propagation in single-well systems exhibits substantial variation among sublayers, resulting in limited areas of hydrate dissociation. Long-term gas production depends on the hydrate dissociation. Consequently, the total 5-year gas production for single-vertical-well and single-horizontal-well systems are only 3.59 × 106 m3 and 5.04 × 106 m3, respectively. 3) Multi-horizontal-well systems can significantly extend pressure propagation, but the maximum increase in gas production is only 47.0%. This is due to the reservoir's low permeability (2.3 mD), which severely hampers hydrate dissociation pressure, limiting it to 8 MPa. Therefore, optimizing depressurization requires reservoir modifications to enhance reservoir permeability.

Separation of CH4 - CO2 gas mixture by gas hydrate crystallisation: A parametric study

In the present study a comprehensive experimental study of the CO2 gas hydrate recovery from the CH4 (81.70 mol.%) - CO2 (18.30 mol.%) experimental gas mixture was realised. The effect of the mode, temperature, pressure, and promoter on the CO2 gas hydrate recovery efficiency was investigated. The parametric study will optimise the technology of gas hydrate crystallisation to CO2 remove from natural gas. The gas mixture process separation factor and gas hydrate recovery were studied in SDS (0.30 wt%) aqueous solutions with and without THF (3.80 wt%). The separation simulation was performed for the two modes: pressure-dropping and constant pressure in the temperature range 272.15–283.15 К at the driving forces 1.00 and 2.00 MPa 8 h after the start of the gas hydrate formation. The different temperature dependence is shown for the CH4 and CO2 gas hydrate recovery in depending on the aqueous solution. The CO2 gas hydrate recovery maximum, equal to 63.92% (without THF) and 57.19% (with THF), is observed at the constant pressure separation at 272.15 K and 2.00 MPa. However, THF addition makes it possible to decrease the gas hydrate dissociation pressure of the experimental gas mixture in 7.87 times at 272.15 K. Thus, the choice of the aqueous solution was determined by the aim for the gas hydrate separation – high gas hydrate recovery (without THF) or low process pressure (with THF).

Modeling of xenon gas hydrate distribution coefficient at methane-containing mixtures separation

The aim of this study is to theoretically estimate of xenon (Xe) gas hydrate distribution coefficient. For the first time, the effect of various natural gas compositions on the Xe gas hydrate distribution coefficient has been investigated at the gas hydrate dissociation pressures, 4.00 and 8.00 MPa in the temperature range 273.15–283.15 K. Based on the results obtained, it can be concluded that Xe concentration in the gas hydrate phase is efficient at the minimum C3H8 concentration in a multicomponent gas mixture close to natural gas composition, at temperature and pressure conditions equal to 273.15 K and 8.00 MPa.

INVESTIGATION OF THE GAS HYDRATE EQUILIBRIUM IN CH4 - CO2 - H2O MIXTURE IN THE PRESENCE OF THF - SDS PROMOTERS

The present study deals with the investigation of a unique technology – gas hydrate crystallisation. This technology is proposed as an alternative approach to natural gas purification from acid gases, particularly from CO2. To implement the gas hydrate crystallisation technology at CO2 recovery from natural gas we experimentally determined the gas hydrate dissociation pressures of the CH4 (81.70 mol.%) - CO2 (18.30 mol.%) gas mixture in THF (3.80 wt.%) aqueous solution with and without SDS (0.30 wt.%) in the temperature range of 283.71–288.00 К. It was found that the gas hydrate dissociation pressures of the mixture under consideration with and without SDS (0.30 wt.%) were in the range of 0.7570–1.9328 MPa at these conditions. The thermodynamically simulated gas hydrate dissociation pressures of the considered mixture without THF (3.80 wt.%) were 6.0828–10.179 MPa at the same temperature range. An average pressure decrease of 6.79 times was observed for the considered temperature range at the addition of THF (3.80 wt.%). According to the experimental results, the enthalpies of the gas hydrate dissociation of the CH4 (81.70 mol.%) - CO2 (18.30 mol.%) gas mixture in THF (3.80 wt.%) aqueous solution with and without SDS (0.30 wt.%) were calculated and were in the ranges of 20.85–33.64 and 22.04–39.81 kJ/mol, respectively.

A priori assessment of long‐term productivity of frac‐packed wells for producing natural gas from marine gas hydrate reservoirs

AbstractThis work investigates the feasibility of using frac‐packing techniques to complete wells in marine gas hydrate fields. It focuses on the long‐term well productivity under pseudo‐steady state flow conditions after the gas hydrate reservoir pressure drops to below the hydrate dissociation pressure within the well drainage area. The analytical model proposed by Shan et al. (J Energy Sci Eng, 2020, 8, 1247) for cross‐flow in the fractured region was modified in this study to include the horizontal radial flow in the non‐fractured region of the well drainage area. Methods were developed to predict the fracture geometry and to design proppant size distribution for formation sand/particle control. Sensitivity analyses with the model identified the fracture radius and permeability being the key factors affecting the productivity of frac‐packed wells. Well productivity was found to increase non‐linearly with fracture radius and permeability. The benefit of increasing fracture size drops due to the choking effect near the wellbore and pressure loss inside the fracture. The benefit of increasing fracture permeability diminishes when the fracture permeability is large due to the bottleneck of low reservoir permeability. Gas hydrate wells in the Shenhu area, northern South China Sea, can be elevated to commercial levels of greater than 10 MMscf per day with a proppant injection volume of 110 cubic feet during frac‐packing. Well productivity can be further increased by injecting higher proppant volume to enlarge fracture. This work presents a simple method for assessment of frac‐packing design to improve well productivity in marine gas hydrate reservoirs.

Cage occupancy and dissociation enthalpy of hydrocarbon hydrates

AbstractAn elaborated statistical mechanical theory on clathrate hydrates is applied to exploration of their phase equilibria and dissociation enthalpies. The experimental dissociation pressures of methane, ethane, acetylene, and propane hydrates are well recovered by the method we have proposed. We estimate water/hydrate and hydrate/guest two‐phase coexisting conditions in the temperature, pressure, and composition space in addition to three‐phase equilibrium conditions. It is shown that the occupancy of guest molecules and the two‐phase boundaries in the phase diagram vary depending sensitively on its size. Enthalpy components arising from the host and guest interactions are separately calculated from the temperature dependence of the corresponding free energy values. This enables to evaluate the dissociation enthalpy at any stable and metastable thermodynamic state taking account of the phase transition in the coexisting phase such as melting of ice, notably that along the three‐phase equilibrium line.

Thermodynamic Modeling Study on Phase Equilibrium of Gas Hydrate Systems for CO2 Capture

A thermodynamic model is introduced to describe equilibrium conditions of gas hydrates formed from mixtures of CO2, N2 and H2O. The model employs the van der Waals and Platteeuw (vdW–P) solid solution theory and a modified version of cubic-plus-association equation of state that uses the Peng–Robinson equation of state for physical interactions (PR–CPA) to describe hydrate and fluid phases, respectively. When not available elsewhere, the model parameters are determined as part of this work. Pure component parameters for N2 were calculated by fitting of the PR–CPA parameters to vapor pressures and saturated liquid densities. Moreover, solubility data for N2 in pure water are used to fit the binary interaction parameter for the N2–H2O system. Finally, Kihara cell potential parameters are obtained by regressing the model to the hydrate dissociation pressures of mixed hydrates. The model is validated with available experimental data in terms of equilibrium dissociation pressure and hydrate composition. Results reveal that the model is capable of describing equilibrium conditions with high accuracy. In addition to the equilibrium dissociation pressure, the model is able to predict hydrate compositions with satisfactory accuracy compared to other models, although such data were not utilized as reference data in the fitting procedure. Due to disparity amongst various data sets for the studied system, it is difficult to find unequivocally a model that perform better for all data sets. However, the introduced model shows more accurate results for most data sets and obtains satisfactory agreement in the rest. Additionally, the presented model predicts the structural transition boundary better than other similar models.

VdWP-FL: An Improved Thermodynamic Theory for Gas Hydrates with Free-Energy Contributions due to Hydrate Lattice Flexibility

A modification of the original van der Waals and Platteuw (vdWP) theory that accounts for free-energy contributions due to the vibrational and librational movement of water molecules in the hydrate lattice is presented. The modified theory is labeled vdWP-FL. In our previous work, we had presented a method to compute these contributions to the partition function. This was successfully applied to simulated phase equilibria of various gas hydrates. In this work, we apply the vdWP-FL theory to experimental data of gas hydrate phase equilibria and recompute the guest–water potentials. The empty hydrate reference properties are directly computed from molecular simulations. In this implementation of the vdWP-FL theory, only one parameter per guest molecule per cavity type is regressed from the experimental data on gas hydrates. The gas hydrates chosen for this study are methane, ethane, carbon dioxide, propane, iso-butane, and the hydrates formed by their binary mixtures. The vdWP-FL theory gives accurate predictions of the dissociation temperatures and pressures of the above gas hydrates and their mixtures. In addition, it also predicts the hydrate cage occupancy accurately.

Modeling the Hydrate Dissociation Pressure of Light Hydrocarbons in the Presence of Single NaCl, KCl, and CaCl2 Aqueous Solutions Using a Modified Equation of State for Aqueous Electrolyte Solutions with Partial Ionization

In this study, we present the modeling of the hydrate dissociation pressures for methane, ethane, and propane in the presence of NaCl, KCl, and CaCl2 aqueous solutions using a modified equation of state for aqueous electrolyte solutions with partial ionization (AES-PI) coupled with the van der Waals–Platteeuw theory. The proposed thermodynamic model includes a linear correlation for describing the ionic hydration process as a function of the pressure and molality. The proposed approach is capable of representing the inhibition effect at different salt concentrations. The results showed an excellent agreement between the experimental data and the calculated values at different conditions typical of the deepwater environment.

Predicting semiclathrate hydrates dissociation pressure using a rigorous machine learning approach

In this study, a supervised learning algorithm known as multi-layer perceptron neural network (MLP-NN) is employed to predict the dissociation pressure of semiclathrate hydrates of CO2+N2, CH4+N2, CO2+CH4, CO2, CH4, and N2 systems in the presence of different concentrations of TBAB. The hydrate dissociation pressure was assumed as a function of the molar concentrations of the gases, the weight percent of TBAB tetra n-butyl ammonium bromide (TBAB) and the system temperature. A data set of 349 data points gathered from the open literature and divided into 70%, 15%, and 15% ratio for three subsets of training, validation and testing, respectively. The optimum network structure was selected through a trial and error procedure with the overall R2 of 0.97, MSE of 0.16, and AARD% of 6.19%. While both graphical and statistical measures approved the robustness and performance of the network, the applicability of the model and quality of experimental data was investigated through Leverage approach.

Phase stability conditions for clathrate hydrate formation in (fluorinated refrigerant + water + single and mixed electrolytes + cyclopentane) systems: Experimental measurements and thermodynamic modelling

Phase equilibrium conditions (dissociation data) for clathrate hydrates (gas hydrates) were studied for systems involving fluorinated refrigerants + water + single and mixed electrolytes (NaCl, CaCl2, MgCl2 and Na2SO4) at varying salt concentrations in the absence and presence of cyclopentane (CP). The ternary systems for (R410a or R507) + water + CP were performed in the temperature and pressures ranges of (279.8–294.4) K and (0.158–1.385) MPa, respectively. Measurements for {R410a + water + (NaCl or CaCl2) + CP} were undertaken at salt concentrations of (0.10, 0.15 and 0.20) mass fractions in the temperature and pressure ranges of (278.4–293.7) K and (0.214–1.179) MPa, respectively. The temperature and pressure conditions for the (R410a + water + Na2SO4) system were investigated at salt concentration of 0.10 mass fraction in range of (283.3–291.6) K and (0.483–1.373) MPa respectively. Measurements for {(R410a or R507) + water + mixed electrolytes NaCl, CaCl2, MgCl2} were undertaken at various salt concentrations of (0.002–0.15) mass fractions in the temperature and pressure ranges of (274.5–292.9) K and (0.149–1.119) MPa in the absence and presence of CP, for which there are no published data related to mixed salt and a promoter. The phase equilibrium measurements were performed using a non-visual isochoric equilibrium cell and the pressure-search technique. This study was focused on obtaining equilibrium data that can be utilized to design and optimize for water desalination process and the development of a Hydrate Electrolyte–Cubic Plus Association (HE–CPA) Equation of State based model. The results indicate hydrate dissociation pressure reduction/hydrate dissociation temperature increase up to ambient conditions in the presence of promoter (CP). The experimental results were then modelled. The modelling results are in good agreement with the measured hydrate dissociation data.

Dissociation behaviors of methane hydrate in marine sediments from South China Sea under constant pressure

The dissociation behaviors of methane hydrate under constant pressure in the marine sediments from the South China Sea were experimental studied. The experiments were carried out in a high-pressure reactor with the effective volume of 416 cm3. The marine sediments with mean pore diameter of 12.178 nm and total pore volume of 4.997×102 mL/g, surface area of 16.412 m2/g were used for the experiments. The mass fraction of water in the marine sediments is 40%. The methane hydrate was formed at the initial pressure of 14.4 MPa and dissociated by depressurization through the gas release from the reactor to the supply vessel with the volume of 1091 cm3. The moles of the gas released were calculated by the pressure change in the supply vessel. The dissociation experiments were carried out at the temperature range of 274.15–281.15 K and the dissociation pressure range of 3.0–5.0 MPa. The experimental results show that the hydrate begins to dissociate during the depressurization period, resulting in the significant decrease of the temperature in the reactor to be below the melting-point due to that the hydrate dissociation is an endothermal process. The lowest temperature during the hydrate dissociation in marine sediments is significantly lower than that in silica sands. The methane hydrate can dissociate when the pressure is higher than the equilibrium dissociation pressure for bulk methane hydrate. The dissociation rate of methane hydrate, the final gas dissociated from the hydrate and the final hydrate dissociation ratio increase with the decrease of dissociation pressure. For the experiments with different experimental temperature, the hydrate dissociation rate increases with the increase of the experimental temperature, and the final gas dissociated from hydrate is affected by the initial hydrate saturation in the marine sediments. The hydrate can dissociate completely when the dissociation pressure is lower than the equilibrium hydrate dissociation pressure corresponding to the experimental temperature for the bulk hydrate.

Study on the decomposition conditions of gas hydrate in quartz sand-brine mixture systems

There are huge reserves of natural gas hydrates, a type of low-carbon energy resource, and it is considered important to study the stability conditions of hydrates in situ, to facilitate reserve evaluation and exploitation. The decomposition conditions of methane hydrate were determined in a quartz sand-brine mixing system, using an isothermal, stepwise, depressurising method. Influencing factors, such as sand particle size and pore water salt concentration, and the combined effect of these factors on the hydrate phase equilibrium, were investigated. The results showed that the decomposition pressure was distributed over a small range, and at specific temperatures. This may be partly related to the uneven distribution of pore size, but was shown to be mainly owing to the change of salt concentration during hydrate dissociation, as verified by differential scanning calorimetry. In addition, the hydrate dissociation pressure increased slightly with decreased particle size, and the maximum relative deviation of the dissociation pressure was 1.68%, when the sand particle size was within 100 mesh, which was mathematically negligible. For predicting the decomposition condition of hydrate in the quartz sand-brine mixing system, commercially-available CSMgem and PVTsim software showed high accuracy across a large temperature interval. An in-house, Chen-Guo hydrate model was valid when the temperature was below 277 K, while the Multiflash programme exhibited too large an error to be applied to this system.

Theoretical modeling of the hybrid membrane-gas hydrate crystallisation process for xenon recovery

A mathematical model of the hybrid membrane-gas hydrate crystallisation for xenon (Xe) recovery from binary gas mixtures approximated to natural gas composition and normalised by 100% is considered. The first gas mixture is CO2 (97.09 vol.%) and Xe (2.91 vol.%). The second gas mixture is H2S (97.09 vol.%) and Xe (2.91 vol.%). The third gas mixture is CH4 (99.84 vol.%) and Xe (0.16 vol.%). Poly(dimethylsiloxane) and Cellulose triacetate membranes are used. The process at the gas hydrate mixture dissociation pressures and the gas hydrate formation temperature is 275.15 K. The dependences of the gas hydrate, the membrane, the hybrid membrane-gas hydrate Xe recoveries through the membranes versus gas mixture withdrawn are obtained. Xe has the good gas hydrate-forming properties and will the most effective concentration in the gas hydrate phase. For the most efficient Xe recovery in the membrane-gas hydrate module must not be impurities with the gas hydrate dissociation pressure and permeability through the membrane close to Xe. It is shown that the largest Xe recovery is 20.08 in CH4 (99.84 vol.%) and Xe (0.16 vol.%) gas mixture. Thus, the efficiently Xe recovery from the main natural gas component – CH4 by the hybrid membrane-gas hydrate crystallisation is possible.

Phase stability conditions of clathrate hydrates in the (methane + 3-methyl-1-butanol + water), (methane + 3,3-dimethyl-2-butanone + water) and (methane + 2,3-dimethyl-2-butene + water) systems: Experimental measurements and thermodynamic modeling

Abstract In this communication, hydrate dissociation data for methane + three liquid hydrocarbons namely 3-methyl-1-butanol, 3,3-dimethyl-2-butanone and 2,3-dimethyl-2-butene are reported. An isochoric pressure-search method was employed to generate the four-phase equilibrium data in the diverse pressure ranges (2.43–8.23 MPa, 1.73–7.56 MPa, and 2.81–7.05 MPa), respectively. The corresponding temperature ranges are (274.3–284.3 K, 277.1–288.9 K and 274.4–283.3 K), respectively. The obtained results in comparison with methane hydrate dissociation data indicate that at a given pressure, the hydrate dissociation temperature in the system consisting of methane + 3-methyl-1-butanol + water roughly equals to those in the system with methane hydrate. Although four phase hydrate dissociation data of methane + 2,3-dimethyl-2-butene + water system has not been determined to exhibit promotion effect, the reduction of hydrate dissociation pressure was observed in the methane + 3,3-dimethyl-2-butanone + water system. Furthermore, estimation of hydrate dissociation conditions of the aforementioned systems has been done by applying the van der Waals-Platteeuw type thermodynamic model and a good agreement is observed.