Gas Hydrate Technology Research Articles

Comparative kinetics and enhanced desalination efficiency of hydrate-based desalination using HFC-125a, HFC-134a, and HFC-152a through hydrate pelletization and induced melting

The present study demonstrates the feasibility of gas hydrate technology for effective desalination of salt water without requiring pre- or post-treatment. The research highlights two main aspects: the thermodynamic and comparative kinetic properties of hydrofluorocarbon (HFC) gases, and the novel concept of hydrate pelletization enhanced by an induced pellet melting procedure. The thermodynamic viability of HFC gases such as HFC-125a, HFC-134a, and HFC-152a for hydrate formation in both saline and non-saline conditions is underscored. For the first time, a comparative analysis of the gas uptake kinetics for these three gases is presented under 0, 3.5, and 8.0 wt% NaCl conditions. Results indicate that HFC-134a and HFC-152a exhibit rapid gas uptake kinetics, while HFC-125a shows sluggish kinetics, attributed to the effective pressure driving force and subcooling temperature. Regardless of the guest gas, the chosen experimental conditions achieved salt removal efficiency of ~70 % in 3.5 wt% NaCl and ~ 75 % in 8.0 wt% NaCl. The novel induced hydrate pellet melting approach significantly improved salt removal efficiency, exhibiting a nonlinear behavior where the rate of salt removal efficiency increases asymptotically as more hydrate melts. New insights into salt distribution within the hydrate pellet reveal that the core contains higher salinity, than the outer layer.

Comparison of physicochemical properties between CO2 and CH4 nanobubbles produced by gas hydrate decomposition

Nanobubbles, known for their distinctive physicite and chemical properties, have been successfully applied in various fields. However, the basic properties of nanobubbles formed by gas hydrate dissociation remain poorly understood. In this work, a series of experiments are conducted to investigate the physicochemical properties and stability of CO2 and CH4 nanobubbles produced by hydrate dissociation. The results indicate that the average size of CO2 and CH4 nanobubbles derived from hydrate decomposition slightly increases as the static time prolongs, exhibiting the excellent stability of nanobubbles. Similar to macroscopic bubbles, the size variation of both nanobubble types exhibits a positive correlation with temperature. The absolute value of the surface zeta potential of the CH4 nanobubbles decreases with time, while the opposite is true for the CO2 nanobubbles. Moreover, the expansion in size for both nanobubble types demonstrates a negative correlation with increasing pH, whereas the zeta potential displays a positive correlation with pH. We observed that nanobubble potential is substantially influenced by metal cations within the solution, and the potential effect of CO2 and CH4 nanobubbles was preliminarily discussed by settlement tests as well. These findings may serve as valuable references for future assessments of the role of nanobubbles in reservoir seepage processes and the advancement of gas hydrate technology.

Kinetics studies of CO2 hydrate formation in the presence of l-methionine coupled with multi-walled carbon nanotubes

In recent years, gas hydrate technology has been considered to be a promising method for CO2 capture and transport. Nevertheless, the development of the gas hydrate technology is hindered by the slow hydrate formation. In this work, the effects of concentration, initial pressure and gas-liquid ratio on the CO2 hydrate formation kinetics in the compound system of environmentally friendly additive l-methionine (L-met) coupled with low-dose multi-walled carbon nanotubes (MWCNTs) were investigated for the first time. The results showed that L-met coupled with MWCNTs could effectively promote the CO2 hydrate formation, and the promotion effect was related to the MWCNTs concentration. At 4.0 MPa, compared to the 0.1250 wt% L-met single system, the compound system with the MWCNTs concentration of 0.0270 wt%∼0.0720 wt% increased the CO2 gas consumption (Gsum) by an average of 6.37 %, and the induction time (tin) of CO2 hydrate formation were shortened by an average of 36.03 %. The optimal concentration of MWCNTs was 0.0450 wt%. Meanwhile, the increase of the pressure and gas-liquid ratio could effectively accelerate the kinetics of CO2 hydrate formation. The promotion effect of the pressure increasing was better than that of the gas-liquid ratio increasing. The pressure increasing could result in the maximum increase of 39.75 %, 122.83 %, and 69.85 % in Gsum, initial gas consumption rate (N10), and the gas to hydrate conversion (GTH), respectively; and the highest reduction of tin was 83.72 %. Furthermore, the hydrate morphological observations revealed that CO2 hydrate initially nucleated in the inner of L-met solution, and the hydrate particles in the compound system of L-met coupled with the MWCNTs were porous snowflakes. The wall climbing effect induced by capillary forces was further explained, and the presence of L-met enhanced the mass transfer capacity of CO2 hydrates. The practical use of fast hydrate formation technology for CO2 capture and sequestration has been facilitated by this work.

Thermodynamic phase equilibria study of Hythane (methane + hydrogen) gas hydrates for enhanced energy storage applications

Hydrogen blending with natural gas has become an effective technique for incorporating the characteristics of natural gas and facilitating the storage and transportation of hydrogen gas. The transportation of hydrogen and natural gas (methane) blend, also referred to as Hythane, presents numerous challenges, advantages, and disadvantages that differ based on the technology employed. The current research showcased a thorough examination of the thermodynamics involved in studying the three phase equilibrium analysis of gas hydrate technology for storing Hythane gas mixtures. Three different Hythane compositions varying in hydrogen percentage were selected, and the isochoric gas hydrate phase equilibria study was performed. The experimental results of phase equilibria and thermodynamic modelling using CPA EOS in software were compared. A similar study was also conducted in the presence of a 5.56 mol % THF solution to understand the reduction in the pressure requirement for the phase equilibria. Results from the mixed Hythane+THF gas hydrate findings suggested stable gas hydrate formation at much lower pressure requirements, increasing the credibility of storing Hythane mixtures in gas hydrates at moderate conditions. The gas compositions for each experiment were analyzed using gas chromatography to evaluate the presence of the desired gas in the hydrate phase. Heat exchange during the gas hydrate dissociation was analyzed using a high pressure differential scanning calorimeter (DSC). The change in the heat release temperature also indicates the stability of the gas hydrate, and with increasing hydrogen gas in the blend, the gas hydrate stability decreased. The Clausius-Clapeyron equation was employed to compute the heat of gas hydrate dissociation, and a comparison was made with the heat of dissociation obtained from the DSC study. The experimental investigations on Hythane gas hydrates were performed to find the hydrogen storage inside the gas hydrate phase and compare it with the previous studies of pure hydrogen hydrates. To demonstrate the Hythane gas transportation, Hythane gas hydrate pellets were formed, followed by their storage in a controlled environment to observeany changes in pressure and temperature. The Hythane gas hydrate pellets demonstrated exceptional stability of Hythane gas presenting an intriguing prospect for utilizing gas hydrate technology in Hythane gas transportation.

Exploring the Potential of HFC-125a Hydrate for Innovative Fire Suppression: A Gas Hydrate Technology Approach

Exploring the Potential of HFC-125a Hydrate for Innovative Fire Suppression: A Gas Hydrate Technology Approach

Eco-friendly hydrogels serving as water carriers for improving methane hydrate formation and dissociation processes

Natural gas hydrate (NGH) technology has broad application prospects in natural gas storage & transportation. In this work, we used eco-friendly hydrogel-based carriers to retain water, which were biodegradable polyvinyl alcohol-co-acrylic acid (PVA-co-PAA) hydrogels, and to react with methane gas and form hydrates. Results indicated that hydrates could be formed in the presences of swollen hydrogel particles without stirring or promoter adding, which might be owed to the enlarged gas–liquid interface and bulk of hydrophilic groups. When mass ratio of PVA to AA (MR) was 1:4, hydrogels performed best in improving hydrate formation kinetics: the induction time was 20.3 ± 20 min, the hydrate growth rate was 0.0217 ± 0.0088 mmol mL−1 min−1, and the methane uptake was 75.84 ± 4.70 mmol mol−1 water. Morphological observations revealed the water retaining behaviors of hydrogels during hydrate formation-dissociation process: a part of absorbed water transferred out of hydrogels to participate in hydrate formation, and afterwards hydrogels could re-absorbed the water released by hydrate dissociation. Moreover, hydrogels kept excellent recycling performance in seven repeated hydrate formation-dissociation cycles. Collectively, PVA-co-PAA hydrogels used as water carriers could improve mass transfer and reaction efficiency during methane hydrate formation-dissociation process, and meanwhile exhibited good recyclability due to strong water absorbing and retaining capabilities, implying that PVA-co-PAA hydrogels might potentially have broad applications in NGH technology.

Technological paradigm-based development strategy towards natural gas hydrate technology

Natural gas, the cleanest fossil fuel, accounts for 24% of global energy demand. As the demand rises, there is a higher technology requirement towards efficient gas storage and transportation. Therefore, based on the technology paradigm theory, this study developed a data analysis system based on bibliometric analysis and visualization techniques to reveal the development path for natural gas transportation technologies. It has identified that competition and diffusion stages of gas transportation technologies are common natural gas transportation technologies and adsorbed natural gas respectively, while the gas hydrates technology is in the shift stage. The importance of laws and policies in driving the technological evolution in these three stages was also examined. Natural gas hydrate’s superior energy storage capacity and moderate synthesis conditions make it a promising natural gas transportation technology. However, challenges, such as technological limitations, industrial realization, economic benefits, and environmental impacts hinder the paradigm shift. Therefore, an integrated natural gas transport system involving natural gas hydrate technology is proposed and associated policy recommendations are given in technological innovation, monitoring systems, and resource allocation to facilitate the development of natural gas hydrate transportation technology.

Driving sustainable energy storage: A multi-scale investigation of methane hydrate formation with green promoters and innovative reactor design

Synthetic Gas hydrates are promising materials for safe and compact energy storage but their wide-scale application is hindered by slow formation kinetics. We investigated the effect of green kinetic promoters of H-SSZ-13 zeolite, L-tryptophan, L-leucine, and L-methionine in a novel reactor design to accelerate hydrate formation at 6 MPa. In (NSR), H-SSZ-13 and L-tryptophan showed superior performance over L-leucine and L-methionine. While H-SSZ-13 showed the lowest average (t90) of 286 mins and the highest volumetric capacity of 115 V/V at 283 K, its kinetic performance, along with other promoters, dropped significantly at 293 K. We introduced a new (FBR) equipped with light (MFP) to increase gas diffusion and thermal conductivity. The combined effect of (FBR)-(MFP) reactor with zeolite significantly improved the kinetics overcoming (NSR) drawbacks. At 293.15 K, H-SSZ-13 zeolite promoter showed superior performance reducing the induction time and (t90) to 3 and 154 mins, respectively. Furthermore, it exploited 88.6%, and 96% of the sII clathrates volumetric storage capacity at 293 K and 283 K, respectively. Finally, we showed that the synthesized hydrates can be stored at atmospheric pressure for 4 months without significant methane loss. This multi-scale approach is paving the way for scaling up green and economical gas hydrate technology.

A new approach to producing a prospective energy resource based on coalmine methane

The paper describes topical issues of a prospective method for coalmine methane utilization for obtaining an additional valuable energy resource for the regional development of coal-mining areas. It is noted that the development of the extraction of methane resources is very urgent and is of great economic importance for ensuring the energy independence of Ukraine. The experience and technologies of using methane and coalmine gas by global coal-mining companies are analyzed. Modern prospects and opportunities for using coal gas are studied. There is a need to transform the coalmine methane removal system and directions for maximizing the use of its resources in a wide range of concentrations in the composition of gas-air mixtures based on the development of innovative technologies to improve the efficiency and cost-effectiveness of functioning coal-mining enterprises. Attention is focused on the advantages of using gas hydrate technologies for obtaining additional energy resource under conditions of changing coalmine methane concentrations. The specifics of the process of mixed gas hydrate formation from gas mixtures of various geneses have been studied. It has been revealed that it is the coalmine gas-methane composition that determines and forms the basic condition for hydrate formation. The thermobaric conditions for the hydrate formation process at different methane concentrations in gas mixtures of degassing systems have been experimentally determined. The results obtained are the basis for further research on efficiency of creating gas hydrates from coalmine methane and determining its minimum permissible concentration in the gas mixture of degassing systems according to the technological and economic criteria of hydrate formation.

Greenhouse gas (GHG) transport as solid natural gas (SNG) hydrate Pellets: Assessment of Self-Preservation & dissociation controls

Safe greenhouse gas (GHG) transport is an integral part of any carbon capture, utilization, and storage (CCUS) operations. This manuscript discusses the assessment of solid natural gas (SNG) hydrate technology to safely transport GHG utilizing the self-preservation capability of hydrates around 248 K. Ice shielding around hydrate grains has been previously implicated as a key mechanism for self-preservation of hydrates. However, there is a lack of thorough understanding of the hydrate grains sintering and compaction effects on self-preservation prior to the ice crust formation around the grains. In a first of its kind study, the promotional effects of hydrate grains compaction and sintering via pellet porosities, aging times, and formation times on self-preservation are presented. Furthermore, real time operational variables such as depressurization rates and system pressure build-up are studied. A unique integrated apparatus was designed to assess in-situ hydrate pellets formation, compaction, and dissociation. This method eliminated the uncertainties of possible hydrate dissociation during material transfer between the operational stages. Around 248 K, hydrate pellet stability occurs in two states: pre-self-preservation (initial fast hydrate dissociation) and extended self-preservation (slow hydrate dissociation over 200 + hours). Decreasing porosity via compaction and increasing formation and pellet-aging times via prolonged sintering increases hydrate pellet stability. The pellet stability can be further promoted by slowly depressurizing the pellet to ambient pressure and allowing pressure build-up from the dissociating hydrates. Additional transport risks are assessed through a sudden loss of temperature from 248 K, which are missing in the literature. Refrigeration failure of the pellet progresses in two stages: (1) a safe insulation stage characterized by slow dissociation and minimal gas evolution, followed by (2) a rapid dissociation stage during which complete dissociation of the pellet took place. Overall, this work elucidates the transportation factors governing self-preservation and dissociation, thus indicating the feasibility for safe GHG transport via SNG technology.

Separation of Xenon from Noble Gas Mixtures of Argon, Krypton, and Xenon Using Gas Hydrate Technology

Separation of Xenon from Noble Gas Mixtures of Argon, Krypton, and Xenon Using Gas Hydrate Technology

Review of Biosurfactants Gas Hydrate Promoters

Biosurfactants are promising additives for gas hydrate technology applications. They are believed to have better eco properties than conventional kinetic hydrate promoters such as sodium dodecyl sulfate (SDS). In this article, the research advances on the use of biosurfactants for gas hydrate formation enhancement have been reviewed and discussed in detail to provide current knowledge on their progress in green chemistry technologies. Specifically, the use of bio promoters in carbon capture, gas storage and transportation are discussed. By far, biosurfactants seem to perform better than conventional hydrate promoters and have the potential to lead to the commercialization of gas hydrate-based technologies in terms of improving hydrate kinetics.

Microscopic study on the key process and influence of efficient synthesis of natural gas hydrate by in situ Raman analysis of water microstructure in different systems with temperature drop

Gas hydrate technology has considerable potential in many fields. However, due to the lack of understanding of the micro mechanism of hydrate formation, it has not been commercially applied so far. Gas hydrate formation is essentially a gas-liquid-solid phase transition of water and gas molecules at a certain temperature and pressure. The key to the hydrate formation is the transformation of water molecule from disordered arrangement to ordered arrangement. In this process, weakly hydrogen bonded water will be correspondingly converted to strongly hydrogen bonded water. Through in situ Raman analysis and experiments, the position change of the corresponding peaks of the strongly hydrogen bonded water and the weakly hydrogen bonded water was compared in this work, and the key microscopic process and influence of gas hydrate formation in different systems were comprehensively studied and summarized. It is found that, with the decrease of temperature, the OH of the weakly hydrogen bonded water remains unchanged when the temperature drops to a certain value, which is the key to the transformation of water into cage hydrate rather than ice. The conversion from the weakly hydrogen bonded water to the strongly hydrogen bonded water is closely related to the gas-liquid interface force, the hydrophilicity/hydrophobicity of the promoter, the ionization degree of liquid, and the electrostatic field of the system. Among the four most common promoters, tetrahydrofuran (THF) has the highest efficiency in promoting methane (CH4) hydrate formation. Therefore, this study provides a scientific direction and basis for the development of high efficient hydrate formation promoters, which can effectively weaken the hydrogen bond of weakly hydrogen bonded water and promote the conversion of weakly hydrogen bonded water to strongly hydrogen bonded water.

Kinetic evaluation of hydrate-based coalbed methane recovery process promoted by structure II thermodynamic promoters and amino acids

Coalbed methane recovery is crucial to coal mine safety, greenhouse gas emission reduction and economic benefits. Gas hydrate technology can be employed to separate CH4 from the N2-rich coal mine gas. To enhance hydrate formation kinetics, separation performance and CH4 recovery, we examined the synergistic effect of structure II (sII) hydrate promoters and amino acids on hydrate formation of 30 mol% CH4/70 mol% N2 mixture, involving three thermodynamic promoters (tetrahydrofuran (THF), cyclopentane (CP) and propane) and four amino acids (l-cysteine, l-methionine, l-tryptophan and l-lysine). Amino acids exhibited extraordinary promotion effects on the propane system with over 10 times improvement in kinetics. CP-amino acid systems excelled in separation performance by enriching CH4 content from 30 mol% to 70 mol%. THF-amino acid systems showed moderate performance on kinetics and separation but achieved the highest CH4 recovery up to 50.27%. The impacts of amino acids were system-dependent: they did not alter the hydrate growth pattern of the THF system but completely changed the hydrate morphology of CP and propane systems. Two possible mechanisms were discussed including interfacial tension alteration and hydrophobicity of amino acids. These insights would provide a basis for further optimizing the hydrate process promoted by sII promoters and amino acids for applications including coalbed methane recovery and beyond.

Promising Hydrate Formation Promoters Based on Sodium Sulfosuccinates of Polyols

The use of natural gas as an energy source is increasing significantly due to its low greenhouse gas emissions. However, the common methods of natural gas storage and transportation, such as liquefied or compressed natural gas, are limited in their applications because they require extreme conditions. Gas hydrate technology can be a promising alternative to conventional approaches, as artificially synthesized hydrates provide an economical, environmentally friendly, and safe medium to store energy. Nevertheless, the low rate of hydrate formation is a critical problem that hinders the industrial application of this technology. Therefore, chemical promoters are being developed to accelerate the kinetics of gas hydrate formation. In this paper, the effect of new sodium sulfosuccinate compounds, synthesized based on glycerol and pentaerythritol, on methane hydrate formation was studied. Experiments under dynamic conditions using high-pressure autoclaves demonstrated that the conversion of water-to-hydrate forms increased from 62 ± 5% in pure water to 86 ± 4% for the best promoter at concentration 500 ppm. In addition, the rate of hydrate formation increases 2–4 times for different concentrations. Moreover, none of the synthesized reagents formed foam, compared to sodium dodecyl sulfate, in which the foam rate was 3.7 ± 0.2. The obtained reagents showed good promotional properties and did not form foam, which makes them promising promoters for gas hydrate technology.

Metal–Organic Frameworks and Gas Hydrate Synergy: A Pandora’s Box of Unanswered Questions and Revelations

Recent research on the role of nanomaterials in gas hydrate science and a few review papers have highlighted the positive synergies between gas hydrates and metal–organic frameworks (MOFs) for gas separation and storage. Metal–organic frameworks consist of metal nodes and organic linkers connected by coordination bonds to form programmable modular structures that are symmetric and have tunable properties. Metal–organic frameworks, also known as microporous or nanoporous materials, provide a large pore volume and surface area suitable for capturing, separating and storing gases through physisorption mechanisms. However, water and water interactions within the nanopores, open metal sites, coordination bonds and surface make metal–organic framework usage in water-based technologies an exciting research topic. Water-based gas hydrate technology could be potential technology that can take advantage of MOF tunable properties, such as a large surface area and a high pore volume, to improve its efficiency and formation mechanism. For the authors of this review, the synergy of MOFs and gas hydrates resembles a Pandora’s box of unanswered questions and revelations. Therefore, this review examines the current state of the art, including present research on gas storage and separation using gas hydrates in the presence of a MOF. In addition, critical technical aspects, such as the water stability of MOFs, the nano confinement effect and water properties in the nanopores, are presented to stimulate critical thinking among scientists in hydrate research to fully exploit the synergies between MOFs and hydrates. This review ends with the authors’ opinion on potential research areas, unanswered questions and practical implications and prospects.

Technology readiness level of gas hydrate technologies

AbstractGas or clathrate hydrates are non‐stoichiometric crystalline materials known primarily for the operational and safety problems they pose during hydrocarbon processing as well as a potential source of unconventional natural gas. Gas hydrates also have a variety of other applications, mostly representing opportunities for technology development such as gas separations and seawater desalination. This dual nature of gas hydrates is best represented by the two faces of a Janus particle. Although the research on the various gas hydrate‐based technologies has been reviewed, the focus has been on the phase equilibrium and kinetic data needed for process design. On the other hand, the status of the technologies in terms of their commercialization has not been methodically assessed. In this work, we employ the nine‐level technology readiness level (TRL) tool to classify the various technologies that are based on gas hydrate crystallization. A brief review of the current status of the technologies is presented first, followed by the status of each one on the TRL scale.

Study on improving gas storage capacity of fixed bed filled with wet activated carbon

Gas hydrate technology is a new gas storage method developed in recent years and has great application potential. Due to the slow formation kinetics of hydrate and the low actual gas storage density, it is a promising method to prepare the fixed bed filled with wet porous materials to inducing adsorption-hydration coupling effect, so as to improve the gas storage efficiency. In this study, various additives including THF, TBAB and diesel oil were added to the water-bearing activated carbon fixed bed to improve its gas storage capacity. Our experimental results show that the addition of THF or TBAB can significantly promote the gas storage performance of the bed. At the optimum concentration of THF (7.5 wt%), the gas storage density of bed (Sb) and gas storage capacity of hydrate (Sw) were 128.66 V/Vb and 194.26 V/Vw, which are 2.89 times and 3.07 times higher than those of wet activated carbon fixed bed without additives, respectively. When 5 wt% TBAB was added, the Sb and Sw were increased by 1.86 times and 1.87 times, respectively. Moreover, using diesel to establish gas channels in the fixed bed to improve the gas mass transfer between the bulk gas phase and the fixed bed can also significantly improve the gas storage performance of the bed. When the oil-carbon ratio (Ro) is 0.5, the Sb and Sw are 97.97 V/Vb and 172.77 V/Vw, respectively. However, further increasing the amount of diesel oil will not significantly improve the gas storage density of the bed due to the volume increase of the bed caused by the addition of diesel. When both diesel oil and THF are added to the water-containing fixed bed, the effect will be not significantly better than that of the bed with diesel oil or THF alone because the two accelerators compete with each other. Finally, the gas release and decomposition speed of the water-bearing fixed bed with / without 7.5 wt%THF are investigated. The results show that the final gas recovery of the bed with 7.5 wt% THF could reach 95.01 %, indicating a good application prospect.

Effects of carbon nanotube on methane hydrate formation by molecular dynamics simulation

The development of gas hydrate technology is beneficial to achieve efficient storage and transportation of methane. The formation of methane hydrate in the presence of single and multiple CNTs was simulated by molecular dynamics applying NPT and NVE ensemble in this study. The cage identification method was applied to detect the number of simulated generated cages. Due to their unique tubular structure, high specific surface area, excellent thermal conductivity and their own activity, the addition of CNTs promoted the formation of hydrates, increased the generation rate and the number of generations, and reduced the nucleation time compared to the pure water system. Triple CNTs showed the best promotion effect under NVE ensemble, and the order of promotion was double CNTs (1.8 wt%) > single CNT (0.9 wt%) > triple CNTs (2.7 wt%) under NPT ensemble. The results show that CNTs facilitate the growth of methane hydrate and the promotion effect varies with concentration and temperature, which provides a functional microcosmic implication for future studies on methane storage and transportation.

Editorial: Gas hydrate and hydrate technology for greenhouse gas mitigation

Editorial: Gas hydrate and hydrate technology for greenhouse gas mitigation