Hydrate-based technologies possess great application potential in the industrial field, including gas storage, transportation, capture, and separation. However, the slow kinetics of hydrate formation hinders its commercial utility. The widespread use of porous media and surfactants in promoting the kinetics of hydrate formation has been accompanied by an increasing interest in understanding how they affect hydrate formation. In this paper, sodium dodecyl sulfate (SDS) was used to compound with three kinds of porous media (glass beads, inert alumina, and activated alumina), with average particle sizes of 1, 3, and 5 mm, to investigate the influence of particle sizes and kinds of porous media on hydrate formation. The results showed that the smaller the particle size of porous media, the more obvious the promotion effect is. Among the three complex systems, there is a significant induction period in the activated alumina system, and the average induction time is about 6 times that of the other systems. However, the formation rate and gas storage capacity of the hydrate are the highest in the activated alumina system. Abundant surface micropores and unique surface charge distribution are very important. Finally, different solution distributions in the reactor resulted in different hydrate distributions, and the nucleation location was vital for hydrate formation and occurrence. Hydrate shells were found to grow on the surface of activated alumina particles, which was not reported in previous studies. This study provides a new view for the study of hydrate morphologies in the complex system of porous media and surfactants.

The use of hydrate-based technologies for gas storage and transportation, carbon capture and sequestration, desalination, and cold energy utilization is gaining popularity. Unfortunately, the slow formation kinetics of hydrates constrains the development of these technologies. Nanofluids have received widespread attention as they can effectively improve the formation kinetics of hydrates. Accordingly, this review examines the history of nanofluid use in rapid hydrate formation as well as the mechanisms of action of various nanofluids. Furthermore, the performance of various nanofluids is fairly assessed, and their performance is compared to that of other systems. Finally, current nanofluid challenges and constraints are discussed, as well as future development recommendations.

Using a hollow fiber membrane contactor to absorb carbon dioxide from natural gas has been a widely studied decarbonization technology in recent years. In this study, 2-(tert-butylamino) ethanol (TBAE), as a new absorbent, was used in hollow fiber membrane contactors to separate CO 2 from CO 2 /CH 4 gas mixtures. A two-dimensional hollow fiber membrane contactor model was established using COMSOL Multiphysics. The changes of membrane specifications and operating conditions during the absorption of CO 2 by TBAE, ethanolamine (MEA), ethyl-ethanolamine (EEA), and ethylenediamine (EDA) were calculated and studied using parallel countercurrent flow, absorbent tube side, and gas shell side. The research results show that the decarbonization performance from large to small is MEA > TBAE > EDA > EEA. The removal rate increased with the increase of the inner diameter of the membrane, the flow rate of the absorbent, and the concentration of the absorbent. Increasing the gas flow rate and the volume fraction of CO 2 in the feed gas resulted in the decrease of the decarbonization rate, and the mass transfer rate increased with the increase of the absorbent flow rate and the volume fraction of CO 2 in the feed gas. The decarbonization effect similar to that of MEA can be achieved using the TBAE absorbent by changing the specification of the membrane, such as increasing the inner diameter of the membrane wire or increasing the concentration of the absorbent.

Hydrate is easily formed in deep-sea pipelines and brings serious flow assurance problems, so it is necessary to look for appropriate hydrate control strategies. In this work, the effects of the anionic surfactant sodium dodecyl sulfate (SDS) on hydrate growth and flow characteristics in the methane−water system were investigated under horizontal and tilted conditions using a highpressure flow loop, and the growth and plugging rules of hydrates in the SDS solution and the effects of different flow rates and tilt angles on hydrate induction time and plugging time were obtained. The experimental results show that hydrates can be easily deposited on the tube wall in the freshwater system. After the addition of SDS, the hydrate can hardly deposit on the wall, allowing the hydrate slurry to flow stably for a long time and a higher volume fraction. The volume fraction of hydrates in the freshwater system is plugged at less than 15%, while in the SDS solution, hydrate slurry can flow steadily for a longer time at more than 30% volume fraction. Although increasing the flow rate reduces the hydrate induction time, the plugging time is significantly prolonged. With the increase in the inclination angle of the loop, hydrate particles with larger particle sizes are more likely to appear, and the time until blockage is decreased. The flow rate in the loop decreases with increasing hydrate particle size. The sensitivity analysis of different influence factors was carried out by the linear regression coefficient method, and the initial flow rate has the most influence on the hydrate induction time, followed by the initial pressure, and the inclination angle has the least influence. This work provides insights into the flow characteristics of the hydrate in the SDS solution, which facilitates the flow assurance studies of hydrates in the gas−water system.

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