CO2 Hydrate Formation Research Articles

Experimental and numerical analysis of CO2 and CH4 hydrate formation kinetics in microparticles: A comparative study based on shrinking core model

The promotion of gas hydrate formation kinetics through mass transfer enhancement has been an important research topic, for which microparticles have been considered an effective method. In this work, carbon dioxide (CO2) and methane (CH4) hydrate formation kinetics in microparticles are investigated using “dry water” particles made of 3, 5 and 8-wt% silica. A modified shrinking-core model is established to study the CO2 and CH4 hydrates formation kinetics. It is the first model that integrates the effects of dissolved gas, the capillary effect of porous hydrate shell, and the volume change from water to hydrate. The experimental results reveal that “dry water” particles with 8-wt% silica has the highest normalized gas uptake due to their small particle size. The simulation results show an initial effective diffusion coefficient of 6.41–6.50×10–14 m2s−1 for CO2 and a slightly higher 6.83×10–14 m2s−1 for CH4 hydrate formation. The average effective diffusion coefficient of gas is higher in smaller particles. The water consumed through capillaries is more prominent in smaller particles, but it only accounts for less than 10% of water consumed at the hydrate–water interface. Furthermore, a decoupled heat transfer model was developed to quantify the effect of heat transfer in gas hydrate formation. The instantaneous temperature gradient in the hydrate shell is of a small magnitude of 10–2 K m−1, indicating that the impact of the heat transfer on hydrate formation kinetics is negligible. This work provides comprehensive insights into gas hydrate formation in microparticles and contributes as a theoretical basis for the improvement of gas hydrate kinetics through mass transfer enhancement.

CO2 enhanced gas recovery and sequestration as CO2 hydrate in shallow gas fields in Alberta, Canada

In this study, we carry out reservoir simulations to investigate the effect of CO2 hydrate formation on CO2 storage capacity in shallow gas fields. Results show that CO2 hydrate formation moderates the reservoir pressure due to volume shrinkage thus allowing more CO2 (122–212% pore volume) to be stored. The CO2 storage capacity in a gas field with CO2 hydrate formation is up to 3.2 times that without CO2 hydrate formation. Due to CO2 hydrate formation, the CO2 storage capacity in a gas field first increases when initial water saturation increases from 0.1 to 0.3 but then decreases when the initial water saturation increases from 0.3 to 0.5. However, the CO2 storage capacity decreases with an increase in initial water saturation if there is no CO2 hydrate forms. Results of screening show that out of 68,327 gas fields in Alberta, 517 gas fields can be used to store CO2 as CO2 hydrate, giving a total CO2 storage capacity of 536 Mt. Of this, depleted gas fields in Alberta have the highest CO2 storage capacity including the Chard and Saleski gas fields with storage capacity of 138 Mt and 94 Mt, respectively.

Carbon Dioxide Captured on a Wet Si−C Composite Material with a Surfactant‐derived Carbon Film

AbstractThe storage capacity of carbon dioxide (CO2) on the wet SBA‐15 material can be greatly improved by forming gas hydrates. The presence of generous polar groups (hydroxyl groups) on the surface of SBA‐15 hinders the formation of CO2 hydrates. In order to further improve its CO2 adsorption capacity, the polar surfaces of SBA‐15 material are changed into non‐polar carbon surfaces by covering with carbon film, and Si−C composite is obtained. Compared with the SBA‐15 material, the pore size and pore volume of the Si−C composite material reduces but its morphology and structure are unchanged. Whether pre‐adsorbed water or not, the experiment results showed that the Si−C composite material is more conducive to the adsorption of CO2 than the SBA‐15 material. In a comparison of the Si−C composite material and the SBA‐15 material at 2.5 MPa, the CO2 adsorption capacity increased from 3.8 mmol/g to 8.5 mmol/g with dry samples, and the CO2 adsorption capacity increased from 20.1 mmol/g to 26.9 mmol/g with wet samples at Rw=2.0.

Equilibrium conditions of hydrate dissociation of CO2 + bromocyclohexane or tetrahydrothiophene + H2O

Hydrate can be used as an effective way to separate CO2. However, the formation of CO2 hydrate requires high pressure and low temperature conditions in pure water, it limits the hydrate method application for the separation of CO2. Thermodynamic prompters can be used to reduce the pressure of CO2 hydrate formation. In this work, the effect of tetrahydrothiophene and bromocyclohexane on CO2 hydrate dissociation conditions is first studied. The addition of tetrahydrothiophene can greatly reduce the equilibrium pressure of CO2 hydrate dissociation. Structure II hydrate forms in the system of CO2 + tetrahydrothiophene + H2O, while structure I hydrate forms in the system of CO2 + H2O. Hydrate equilibrium pressure increases with the increase of temperature. At any temperature, the hydrate equilibrium pressure of CO2 + tetrahydrothiophene + H2O reduces more than 2 MPa, compared the hydrate equilibrium pressure of CO2 in pure water in this work. Bromocyclohexane has almost no effect on the phase equilibrium conditions of CO2 hydrate. The experimental results also show that tetrahydrothiophene can be as a promoter for CO2 hydrate formation.

Hydrate phase equilibrium and dissociation enthalpies for tetrahydrothiophene and different gas systems

The phase equilibrium data of hydrate formation in tetrahydrothiophene (THT) and different gasses including CH4, H2, CO2, and IGCC syngas(40 mol% CO2/60 mol% H2) were measured in this work. The results show that the addition of THT remarkably reduces the CH4, H2, CO2, and IGCC syngas hydrate formation conditions. Besides, for H2, CO2, and IGCC syngas, THT's effect in reducing hydrate formation conditions is slightly less than that in the system containing CP or 5.6 mol% THF. However, for the CH4 gas, the hydrate formation conditions curve obtained from the system containing THT, 5.6 mol% THF and CP are almost similar. In addition, since THT is a water-insoluble promoter, the results proved that its molar fractions can not affect the hydrate formation conditions. Based on the phase equilibrium data we obtained, the dissociation enthalpies of hydrate formation in these systems were also determined via the Clausius-Clapeyron equation and its modified style. The hydrate dissociation enthalpies for THT + CH4, THT + H2, THT + CO2, and THT + IGCC syngas are within 102.2 - 115.26 kJ•mol−1, 312.01 - 315.94 kJ•mol−1, 149.93–213.40 kJ•mol−1 and 160.19 - 181.02 kJ•mol−1, respectively.

Effect of liquid alkane on carbon dioxide hydrate formation

Hydrophobic surface affects gas hydrate formation. It is an effective method to promote hydrate formation by adding hydrophobic materials into hydrate formation system. However, it is little known about the interaction between hydrate formation and macroalkane. n-Dodecane and n-tetradecane are selected as additives to investigate their effect on CO2 hydrate formation in this work. The addition of liquid alkanes effectively improves hydrate nucleation, shortens the induction time of CO2 hydrate formation, and improves the hydrate growth rate. In addition, the total CO2 uptake at the end of the experiments was increased in the presence of liquid alkanes. Compared with the addition of n-dodecane, n-tetradecane has a weaker effect on CO2 hydrate formation. Increasing the stirring rate can effectively reduce the induction time of hydrate formation and improve hydrate growth rate, but has little effect on gas storage capacity in hydrates. The experimental results also show that the increase of experimental pressure or the decrease of temperature is conducive to hydrate formation.

Enhanced CO2 sequestration based on hydrate technology with pressure oscillation in porous medium using NMR

Carbon dioxide (CO2) is a dominant greenhouse gas in the atmosphere that contributes to global warming. A promising approach to mitigate CO2 emissions is CO2 capture and storage (CCS) through clathrate hydrate crystallization under the seafloor; however, numerous issues regarding the mechanisms of concentration, efficiency, and stability of CO2 hydrate sequestration in seafloor sediments remain under dispute. This study employed low-field nuclear magnetic resonance (NMR) measurements to observe the in-situ formation of CO2 hydrate using the pressure oscillation method in porous media and evaluate the carbon sequestration efficiency. Our results indicate that CO2 hydrates are preferentially formed in large pore spaces, further hindering the subsequent gas contact with water in isolated pores. Additionally, a high initial water saturation is more conducive to high-quantity CO2 hydrate capture and sequestration in a pressure variation environment with a higher driving force. The proposed pressure oscillation method could effectively break the mass transfer barriers in the later stage of hydrate formation with the help of CO2 solubility fluctuations, significantly increase the rate of later hydrate formation, and shorten the period of hydrate sequestration.

Superabsorbent polymer for improved CO2 hydrate formation under a quiescent system

The hydrate formation rate and conversion yield are essential factors for hydrate-based gas storage and accordingly various thermodynamic and kinetic promoters have been extensively investigated. However, for hydrate-based CO2 capture, carbonate ions induced from dissolved CO2 in water hinder the performance of kinetic promoters (e.g., sodium dodecyl sulfate (SDS)). In this work, we introduce a superabsorbent polymer (SAP) matrix that provides an extremely high interfacial area between a sorbed tetrahydrofuran (THF) solution and gaseous CO2. The SAP enhanced the formation rate of binary THF-CO2 hydrate, despite the absence of mechanical agitation. We varied the concentration of THF, temperature, reactor volume, and the ratio of solution to the reactor for a systematic study and explored their effects on the CO2 storage capacity and the induction time. We observed that highly concentrated THF and a larger reactor with a high gas-liquid contact area enhanced the CO2 storage capacity and formation rate. Raman and PXRD spectroscopic analyses were employed to investigate the guest distribution and crystalline structure of the THF-CO2 hydrates synthesized under various conditions. All the binary hydrates were structure-II (sII) hydrates, and there was no pure structure-I (sI) CO2 hydrate. Based on the spectroscopic results, we developed a theoretical model that could calculate the amount of enclathrated CO2 and dissolved CO2 in liquid phases separately. This work reveals that SAP has excellent potential for rapid CO2 capture in hydrate media with a high water-to-hydrate conversion ratio.

Effect of Thiouronium-Based Ionic Liquids on the Formation and Growth of CO2 (sI) and THF (sII) Hydrates.

In this manuscript, two thiouronium-based ionic liquids (ILs), namely 2-ethylthiouronium bromide [C2th][Br] and 2-(hydroxyethyl)thiouronium bromide [C2OHth][Br], were tested at different concentrations (1 and 10 wt%) for their ability to affect CO2 (sI) and tetrahydrofuran (THF) (sII) hydrate formation and growth. Two different methods were selected to perform a thermodynamic and kinetic screening of the CO2 hydrates using a rocking cell apparatus: (i) an isochoric pressure search method to map the hydrate phase behavior and (ii) a constant ramping method to obtain the hydrate formation and dissociation onset temperatures. A THF hydrate crystal growth method was also used to determine the effectiveness of the ILs in altering the growth of type sII hydrates at atmospheric pressure. Hydrate–liquid–vapor equilibrium measurements revealed that both ILs act as thermodynamic inhibitors at 10 wt% and suppress the CO2 hydrate equilibria ~1.2 °C. The constant ramping methodology provides interesting results and reveals that [C2OHth][Br] suppresses the nucleation onset temperature and delays the decomposition onset temperatures of CO2 hydrates at 1 wt%, whereas suppression by [C2th][Br] was not statistically significant. Normalized pressure plots indicate that the presence of the ILs slowed down the growth as well as the decomposition rates of CO2 hydrates due to the lower quantity of hydrate formed in the presence of 1 wt% ILs. The ILs were also found to be effective in inhibiting the growth of type sII THF hydrates without affecting their morphology. Therefore, the studied thiouronium ILs can be used as potential dual-function hydrate inhibitors. This work also emphasizes the importance of the methods and conditions used to screen an additive for altering hydrate formation and growth.

Laboratory demonstration of the stability of CO2 hydrates in deep-oceanic sediments

Naturally occurring methane (CH4) hydrates in oceanic sediments have been stable for millions of years. As a natural analog, is it possible to store carbon dioxide (CO2) in the form of hydrates in oceanic sediments for long durations? This is a key question that has had a minimal experimental investigation. Despite the extensive research conducted on CO2 hydrates in carbon capture, CO2-CH4 exchange, and promoter/inhibitor effects on CO2 hydrate formation kinetics, fundamental understanding of and demonstration of CO2 hydrate stability under oceanic sediment conditions remains elusive. In this work, an experimental study has been conducted that provides conclusive insights into the stability of the CO2 hydrates across oceanic sediments. By conducting an experimental study mimicking the oceanic sediment conditions inside a laboratory-scale high-pressure reactor system, we observed that CO2 hydrates formed at reactor walls and inside the sand bed were stable for the entire test period (one month), after which they were intentionally dissociated. This study offers scientific evidence and support for sequestering CO2 in the form of hydrates across oceanic sediments for extended durations.

Comparison of SDS and L-Methionine in promoting CO2 hydrate kinetics: Implication for hydrate-based CO2 storage

The continuously increasing CO2 emissions since industrialization has sparked widespread concerns on environmental and climate change issues. Carbon sequestration and storage technologies (e.g., hydrate-based CO2 sequestration) present promising potential for the disposing of excessive CO2 in geological media. High gas uptake capacity and rapid CO2 hydrate formation kinetics are required for the application of such a technology. In this study, we compared the kinetic promotion effects of sodium dodecyl sulfate (SDS) and L-methionine (L-Met) on CO2 hydrate with the objective of identification of an effective and eco-friendly CO2 hydrate kinetic promoter. The experimental results suggested that L-Met (0.1 wt%) promotes CO2 hydrates formation significantly with a gas uptake in CO2 hydrate five times more than SDS at the same concentration. The hydrate morphology observations indicated that the wall-climbing hydrates associated with the addition of L-Met induced by the capillary driving force offer a possible explanation for the difference in the observed kinetics. A novel calculation method was developed to quantify the partition of CO2 in gas, liquid and hydrate phases. Increasing the initial gas–liquid ratio promotes CO2 stored in the hydrate phase as solid rather than in the liquid phase as dissolution. We further demonstrated the reusability of L-Met in five consecutive cycles of CO2 hydrate formation and dissociation. It was assessed that L-Met as a CO2 hydrate kinetic promoter is superior to SDS and can be employed as an efficient, reliable and eco-friendly kinetic promoter for the hydrate-based CO2 sequestration technology.

Optimal absorbents of CO2 hydrate formation and energy consumption analysis for district cooling application under low pressure conditions

Hydrate-based CO2 capture technology is considered one of the most applicable methods for carbon capture, utilization, and storage, owing to its vast potential and cost effectiveness. Hydrate slurries with an appropriate solid fraction guarantee applicable flowing conditions, and their high dissociation enthalpy permits their use for cold thermal energy transportation. Nevertheless, the required conditions for hydrate formation make the direct capture and subsequent utilization of hydrate slurries challenging. Thus, thermodynamic promoters have been introduced to the hydrates to alleviate the formation conditions and facilitate their practical application. Tetrahydrofuran and tetra-n-butylammonium bromide are selected because of their inherent interaction with water molecules during hydrate formation. Hydrate formation using the pure promoters as well as a mixture of the two is evaluated based on various perspectives. The induction time, hydrate growth period, CO2 capture ratio, and exothermic behavior of each absorbent are assessed under varying concentration and formation conditions. These key parameters provide considerable insight for determining optimal conditions for hydrate slurry-based cold thermal transportation. Based on the performance evaluation, three cases of single promoters and three mixed promoters under the condition of 3 bar are selected for the measurement of dissociation enthalpy. The results reveal that under 3 bar formation conditions, a 3:1 (THF mol%: TBAB mol%) concentration is suitable for ensuring a sufficiently high heat of dissociation and rapid hydrate slurry formation to permit considerable CO2 capture. Consequently, an alternative to a conventional district cooling system by replacing it with a CO2 hydrate slurry cooling system is proposed, and a sufficient reduction in energy consumption is demonstrated.

Effect of different salts on the kinetic parameters of the carbon dioxide hydrate formation

In this study, the effects of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2) on the kinetic parameters of carbon dioxide (CO2) hydrate formation including induction time, amount of gas consumption, rate of gas consumption and storage capacity were experimentally studied. Aqueous solutions with the ion concentration same as the Persian Gulf Seawater were prepared and all the experiments were conducted at a temperature of 274.15 K and pressure of 3.5 MPa. The results showed that salts have an inhibitory effect on the kinetic parameters of CO2 hydrate formation by reducing CO2 solubility in water and electrostatic interaction between water molecules and ions. The intensity of ion inhibition depends on the ion size, ion charge, ion concentration, and the kosmotropic and chaotropic properties of ions. Examination of the kinetic parameters of CO2 hydrate formation in saline solutions with a constant concentration of 1000 mg/L of each ion showed that the Mg2+ has the greatest inhibitory effect on the kinetic parameters by increasing the induction time by 110.71% and reducing gas consumption, rate of gas consumption, and storage capacity by 48.21%, 82.14%, and 68.75%, respectively compared to pure water. The results showed that the inhibition effect of salt ions on the CO2 hydrate formation is in the following order: Mg2+> Ca2+>Na+>K+.

Synthesis of Cu-Al LDH nanofluid and effectiveness as a promoter for CO2 hydrate formation

The present study focuses on the synthesis of a hybrid nanofluid (Cu-Al LDH) and the investigation of its effectiveness as a promoter for CO2 hydrate formation. The Cu-Al LDH nanofluid has been prepared using the one-step co-precipitation technique. XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses have been carried out to evaluate the structural features and particle size measurement. The stability of nanofluid is evaluated using zeta potential measurements. The hydrate formation experiments are conducted in a pilot-scale reactor of 25 L volume with a design pressure of 180 bar. The wall temperature of the reactor is set at 2 °C. The charging of the reactor is carried out in both single and dual-stage at the maximum pressure of 30 bar. The results on the enhancement of gas absorption, total gas consumption, and water to hydrate conversion compared to pure water are reported. Parametric study on the effect of Cu-Al LDH nanofluid concentrations (0.25, 0.5, and 1.0 wt%) and molar ratios (Cu2+:Al3+: Na+ = 4:1:4 and 4:1:4.7) have been carried out. The gas absorption process is more sensitive to molar ratio than the concentration of LDH nanofluid, and about 20 times increase in absorption takes place due to LDH nanofluid in dual gas charging mode. The shuttle effect of the nanoparticle is primarily attributed to the increase in CO2 gas absorption. The strength of gas absorption influences the hydrate morphology. Accordingly, hydrate formation is initiated from the gas–liquid interface in low CO2 absorption case, and hydrate slurry formation inside the bulk fluid followed by layer-wise growth of hydrate from the interface takes place in high gas absorption case. Maximum 176.19% increase in gas consumption is observed at 0.5 wt% nanofluid concentration for (Cu2+:Al3+: Na+ = 4:1:4.7) molar ratio compared to pure water.

Hydrate phase equilibrium determination and thermodynamic modeling of CO2 + epoxy heterocycle + water systems

Ethylene oxide (EO), 1,3-propylene oxide (PO), tetrahydrofuran (THF), 1,3-dioxolane (1.3-DX), 1,4-dioxane (1,4-DX) and 1,3,5-trioxane (s-TO) were selected to investigate their thermodynamic promotion effects on CO2 hydrate formation. New hydrate phase equilibrium data of carbon dioxide + epoxy heterocycles + water systems were determined employing an isochoric temperature-search method in the temperature range of (273.15 to 295.35) K and the pressure range of (0.4 to 4.5) MPa. Results showed that the presence of epoxy heterocycles significantly increased the hydrate formation temperature substantially compared with that of pure CO2 hydrate. Under the same conditions, the phase equilibrium temperature of CO2 hydrate under the action of the additive was from low to high: PO < 1,4-DX < 1,3-DX < s-TO < EO < THF. CO2 hydrate dissociation enthalpies with different epoxy heterocycles were also calculated from Clausius–Clapeyron equation to infer their stabilities and the structures formed. It was found that the estimated enthalpy of dissociation was consistent with the superiority sequence obtained from the phase equilibrium data, illustrating that the water-soluble sII clathrate former of THF had the highest hydrate promoting effect. Moreover, Chen-Guo model, associated with a modified Joshi empirical activity model and PR equation of state was proposed further to predict hydrate phase equilibrium. Satisfactory agreement was observed between predictions and experimental data. Analysis of the results confirmed that the proposed thermodynamic model worked well in describing phase behavior of complex hydrates and the maximum relative error of the pressure was less than 8.5%.

Kinetic insight on CO2 hydrate formation and dissociation in quartz sand in presence of brine

CO2 storage as hydrates in porous media is a promising method to sequester carbon dioxide (CO2) that need to be comprehended to guide its potential site selection prospects. In this study, CO2 hydrate formation and dissociation were studied in three quartz sand particles with varying petrophysical properties such as surface area, pore size, and porosities. The studied quartz sand particle sizes are QS-1 (<0.6 mm), QS-2 (0.6–0.8 mm), and QS-3 (0.8–2.0 mm). The hydrate formation experiments were conducted in a high-pressure hydrate reactor with and without brine (3.3 wt.% NaCl) at 4 MPa and temperatures of 274.15 K and 277.15 K in 100% sample saturation. The hydrate dissociation kinetics were studied at two different temperatures of 277.15 K and 279.15 K. The results show that hydrates form faster in deionized water (DI) than brine solution. The presence of brine reduced the CO2 storage capacity by 30% compared with deionized water. In addition, the presence of brine reduces the stability of CO2 hydrates. CO2 hydrate formation and dissociation behavior in porous media is highly controlled by the quartz sand porosity, pore size, and surface area. The quartz sand particles with low porosity were found to efficiently store more CO2 with a fast onset hydrate formation time of 6 hr and high gas to hydrate conversion of 55%. However, the CO2 hydrates in the sand particles with low porosity were less stable and averagely prolonged the time take to release 90% of CO2 of the systems with high porosity by 39%.

Experimental investigation of CO2 hydrate formation in silica nanoparticle system under static conditions

CO2 hydrate has potential applications in air conditioning cold storage, seawater desalination, carbon capture and storage, etc. Research on CO2 hydrate formation is of great significance in order to solve the problems of long introduction time and slow growth rate. This work focuses on the kinetics of CO2 hydrate formation in the presence of silica nanoparticle under static conditions. A total of 17 sets of experiments were performed with the particle size of 5 nm, 25 nm, 50 nm, 100 nm and the concentration of 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%. We found silica nanoparticles can effectively promote the CO2 hydrate formation and the promotion effect is enhanced with the increase of concentration within a certain range (0–0.5 wt%). The experimental results show that the shortest induction time is reduced by 72.3%, the minimum subcooling degree is reduced by 3 K and the maximum conversion rate is increased by 39%. The promotion or inhibitory effect on hydrate formation depends on the concentration of nanoparticles for hydrophilic nanomaterials. Furthermore, the fluctuation–dissipation in gas consumption in the pre-nucleation stage was proposed with the decay of the fluctuation autocorrelation function obeying to the Onsager hypothesis. The variable parameters n and k of the Avrami equation were obtained and compared to explain the experimental results under different nanoparticle systems.

Experimental and computational investigation of hydrophilic monomeric substances as novel CO2 hydrate inhibitors and potential synergists

CO2 hydrate formation in the CO2 transmission pipelines for ocean or geological sequestration can result in pipeline blockage and rupture. Herein, monomeric substances (urea (U), acetamide (A), and glycine (G)) that are easily decomposable were evaluated as kinetic hydrate inhibitors and potential synergists for CO2 hydrate using experimental and computational approaches. The onset temperatures of CO2 + inhibitor hydrates were experimentally measured using a high-pressure autoclave reactor. G showed the best inhibition effect among single inhibitors, and combinations of U + A and A + G made the inhibition synergism for CO2 hydrate. Moreover, molecular dynamics simulations were also conducted to understand the nucleation and formation behaviors of CO2 hydrate in the presence of single and mixed inhibitors at a molecular level. The profiles of F4 order parameters and hydrate counts for each CO2 + inhibitor system followed the experimental results. Analyses of hydrogen bond distributions, radial distribution function, and mean squared displacement were carefully conducted to elucidate the inhibition mechanism of monomeric substances and their inhibition synergism for CO2 hydrate. The experimental and computational results would provide insights into the development of new biodegradable CO2 hydrate inhibitors and contribute to safe transportation and injection of CO2 for long-term storage.

Optimal Conditions for Saline Water Desalination by Formation of Co2 Hydrate

Optimal Conditions for Saline Water Desalination by Formation of Co2 Hydrate

Cooperative Effect of Surfactant and Porous Media on Co2 Hydrate Formation and Capacity of Gas Storage

Cooperative Effect of Surfactant and Porous Media on Co2 Hydrate Formation and Capacity of Gas Storage