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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 CO2from CO2/CH4gas 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 CO2by 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 CO2in 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 CO2in 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.

The environmental problems brought about by the drastic increase in CO2concentration are a great challenge that must be faced by mankind for sustainable development. Fortunately, research on CO2hydrates has provided new views to effectively address these challenges. However, the slow kinetics of CO2hydrate formation, unclear enhancement mechanisms, and high process costs have limited the practical application of hydrate-based carbon capture (HBCC) technology. In this work, we investigated the potential value of long-chain alkanes (n-decane) and Tween80 promoter (kinetics) in HBCC. We examined the key factors determining the promoter effect of long-chain alkanes and the synergistic effect of Tween80 with long-chain alkanes for the first time. The results showed that long-chain alkanes can play a facilitating or inhibiting role for the hydrate formation, depending on the state of the long-chain alkanes. The mechanism of long-chain alkanes to improve the kinetics of hydrate formation was mainly due to the hydrophobic effect and gas mass transfer. The addition of Tween 80 enhanced the stability of the system and promoted the gas mass transfer of long-chain alkanes, which could realize the kinetic enhancement under low-speed stirring conditions. This work helps to elucidate the mechanism of hydrocarbon compounds' influence on the kinetics of hydrate formation and provides a basis for their potential value for HBCC. It also provides some theoretical guidance for the use of inhibitors in the presence of hydrocarbon compounds.

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 high-pressure 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.