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1. Microscopic insights on clathrate hydrate growth from non-equilibrium molecular dynamics simulations

   https://doi.org/10.1016/j.jcis.2023.06.032  

   Phan, Anh; Stamatakis, Michail; Koh, Carolyn A.; Striolo, Alberto (November 2023, Journal of Colloid and Interface Science)

   Clathrate hydrates form and grow at interfaces. Understanding the relevant molecular processes is crucial for developing hydrate-based technologies. Many computational studies focus on hydrate growth within the aqueous phase using the ‘direct coexistence method’, which is limited in its ability to investigate hydrate film growth at hydrocarbon-water interfaces. To overcome this shortcoming, a new simulation setup is presented here, which allows us to study the growth of a methane hydrate nucleus in a system where oil–water, hydrate-water, and hydrate-oil interfaces are all simultaneously present, thereby mimicking experimental setups. Using this setup, hydrate growth is studied here under the influence of two additives, a polyvinylcaprolactam oligomer and sodium dodecyl sulfate, at varying concentrations. Our results confirm that hydrate films grow along the oil–water interface, in general agreement with visual experimental observations; growth, albeit slower, also occurs at the hydrate-water interface, the interface most often interrogated via simulations. The results obtained demonstrate that the additives present within curved interfaces control the solubility of methane in the aqueous phase, which correlates with hydrate growth rate. Building on our simulation insights, we suggest that by combining data for the potential of mean force profile for methane transport across the oil–water interface and for the average free energy required to perturb a flat interface, it is possible to predict the performance of additives used to control hydrate growth. These insights could be helpful to achieve optimal methane storage in hydrates, one of many applications which are attracting significant fundamental and applied interests. 

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2. Mechanisms underlying foam-based electronucleation of hydrates

   Acharya, P; Lin, D; Bahadur, V (June 2018, Proceedings of the 2018 International Conference on Nanochannels, Microchannels and Minichannels)

   Nucleation of clathrate hydrates at low temperatures is constrained by very long induction (wait) times, which can range from hours to days. Electronucleation (application of an electrical potential difference across the hydrate forming solution) can significantly reduce the induction time. This work studies the use of porous open-cell foams of various materials as electronucleation electrodes. Experiments with tetrahydrofuran (THF) hydrates reveal that aluminum and carbon foam electrodes can enable voltage-dependent nucleation, with induction times dependent on the ionization tendency of the foam material. Furthermore, we observe a non-trivial dependence of the electronucleation parameters such as induction time and the recalescence temperature on the water:THF molar ratio. This study further corroborates previously developed hypotheses which associated rapid hydrate nucleation with the formation of metal-ion coordination compounds. Overall, this work studies various aspects of electronucleation with aluminum and carbon foams. 

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3. Techno-Economic Modeling of CO2 Hydrate Slurry Formation for Carbon Sequestration

   https://doi.org/10.1115/ES2024-130772  

   Bhati, Awan; Bahadur, Vaibhav (July 2024, American Society of Mechanical Engineers)

   Abstract Significant carbon sequestration capacity (up to 10 Gigatons/yr) will be needed by 2050 to limit the Earth’s temperature rise to < 1.5 °C. The current worldwide capacity is ∼40MT/yr, which highlights the need for the development of new and scalable sequestration approaches. One novel technology for long-term sequestration of CO2 is the deposition of CO2 hydrates (ice-like solids made with water and CO2) on the seabed (under marine sediments or with artificial sealing). This involves rapid formation of CO2 hydrate slurries in a bubble column reactor (BCR) by bubbling CO2 gas at high flow rates in a BCR with the unreacted CO2 being recirculated; this approach is being pioneered by the present research group. This study utilizes recent experimental results on ultra-fast hydrate formation to conduct a techno-economic analysis of the hydrate slurry-making process. All analysis is conducted for a 1 Megaton/yr sequestration project, which is expected to run for 30 years. Our analysis shows that the total cost of hydrate slurry production is $16.2/ton. Such projects would require an initial investment of $74M, and the energy requirement will be 641 MWh/day. Contributions of each part of the process to the total cost are identified. Our results show that gas recirculation in a BCR contributes minimally (0.04%) to the overall energy requirement. Furthermore, the cost of BCR is only 0.3% of the total investment cost. This suggests that a low conversion of gas into hydrates in each pass of the BCR is not detrimental from a techno-economic standpoint. The findings of this study set the stage for more detailed analysis of hydrates-based sequestration, which is essential to add this technology to the existing bank of established carbon sequestration solutions. 

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4. Analysis of Electrochemical Capture of CO2 From Oceanwater Coupled With Hydrates-Based Seabed Sequestration

   https://doi.org/10.1115/ES2024-132209  

   Hamalian, Mark; Bhati, Awan; Bahadur, Vaibhav (July 2024, American Society of Mechanical Engineers)

   Abstract Novel energy efficient and scalable carbon capture and sequestration technologies are critical to meeting the goals of the Paris Agreement. In this study, we present a first-order system-level assessment of an integrated carbon capture and carbon sequestration plant that couples electrochemical CO2 capture from oceanwater with co-located long-term carbon sequestration as CO2 hydrates (ice-like solids) on the seabed. Separate recent experimental results associated with electrochemical capture and hydrate formation form the basis for this energetics-focused analysis, which evaluates power consumption of all the key components associated with capture and sequestration. Hydrates can be formed from both pure water as well as seawater, and the implications of including a desalination plant to provide pure water for hydrate formation are studied. All analysis is conducted for a 1 plant which captures and sequesters 1 megaton CO2 annually. Our results indicate the carbon capture will consume significantly more energy than carbon sequestration despite the use of a low-energy consuming electrochemical technique. From a sequestration standpoint, there are clear benefits to forming hydrates at high pressures, since the elevated formation rates reduce the number of hydrate formation reactors significantly. It is also seen that the addition of a desalination plant to provide pure water for hydrate formation (which speeds up hydrate formation) will not affect the energetics of the overall process significantly; however the CAPEX and operational aspects of including a desalination plant need to be analyzed in greater detail. Overall, this study seeds a novel CCS concept which can be deployed via decommissioned oil-gas platforms to capture CO2 from surface oceanwater and store CO2 right below on the seabed after appropriate sealing (artificial or natural). 

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5. Creeping Gas Hydrate Slides

   https://doi.org/10.14379/iodp.proc.372A.2019  

   Pecher, I.A.; Barnes, P.M.; LeVay, L.J. (May 2019, Proceedings of the International Ocean Discovery Program)

   null (Ed.)

   International Ocean Discovery Program (IODP) Expedition 372 combined two research topics: actively deforming gas hydrate–bearing landslides (IODP Proposal 841-APL) and slow slip events on subduction faults (IODP Proposal 781A-Full). This expedition included a coring and logging-while-drilling (LWD) program for Proposal 841-APL and a LWD program for Proposal 781A-Full. The coring and observatory placement for Proposal 781A-Full were completed during Expedition 375. The Expedition 372A Proceedings volume focuses only on the results related to Proposal 841-APL. The results of the Hikurangi margin drilling are found in the Expedition 372B/375 Proceedings volume. Gas hydrates have long been suspected of being involved in seafloor failure. Not much evidence, however, has been found to date for gas hydrate–related submarine landslides. Solid, ice-like gas hydrate in sediment pores is generally thought to increase seafloor strength, which is confirmed by a number of laboratory measurements. Dissociation of gas hydrate to water and overpressured gas, on the other hand, may weaken and destabilize sediments, potentially causing submarine landslides. The Tuaheni Landslide Complex (TLC) on the Hikurangi margin shows evidence for active, creeping deformation. Intriguingly, the landward edge of creeping coincides with the pinch-out of the base of gas hydrate stability on the seafloor. We therefore proposed that gas hydrate may be involved in creep-like deformation and presented several hypotheses that may link gas hydrates to slow deformation. Alternatively, creeping may not be related to gas hydrates but instead be caused by repeated pressure pulses or linked to earthquake-related liquefaction. Plans for Expedition 372A included a coring and LWD program to test our landslide hypotheses. Because of weather-related downtime, the gas hydrate–related program was reduced and we focused on a set of experiments at Site U1517 in the creeping part of the TLC. We conducted a LWD and coring program to 205 m below the seafloor through the TLC and the gas hydrate stability zone, followed by temperature and pressure tool deployments. 

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