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A pressure swing hydrate-membrane coupled separation (PSHMS) process was designed, and process simulation was conducted using a combination of Aspen Plus and Excel. PSHMS achieves continuous, highly efficient, and stable production of qualified gaseous products without thermodynamic promoters of hydrate or circulating working fluids. In hydrogen separation from diesel hydrogenation tail gas, PSHMS exhibits lower energy consumption and higher efficiency compared to hydrate-based separation technologies. Sensitivity analyses of various design parameters within PSHMS were performed through simulation, the results indicate that low temperature, high initial pressure, and high water content are all advantageous for improving separation efficiency. The selection of feed rates needs to be determined comprehensively based on the design parameters. The optimized unit energy consumption of PSHMS is merely 46.41 kJ/mol, significantly lower than the 117.94 kJ/mol of hydrate-based separation technology. • Study of self-designed pressure swing hydrate-membrane coupled method (PSHMS). • The energy consumption of PSHMS is only 40% of that in hydrate-based separation method. • The operational approach of pressure swing separation mitigates hydrate blockage issues in pipelines. • Sensitivity analysis of design parameters in PSHMS was conducted. • Lower temperatures, higher pressures, and increased water content are conducive to effective performance. [ABSTRACT FROM AUTHOR]

• A novel hydrate-based gas separation model, namely the gas–water-hydrate three-phase flash model, was proposed. • The proposed model further considers the structural transitions of hydrates. • Four typical hydrate structure transformations are discussed through experiments. • The key parameters for calculating the degree of hydrate structural transitions were optimized. • The calculation results of the proposed model have an absolute average relative deviation of 8.00%. The study introduces a pioneering model for hydrate-based gas separation technology, which enhances the prediction method for the coexistence of multiple structure hydrates. The calculated results demonstrate strong agreement with 96 sets of experimental data, exhibiting a lower average relative deviation of 8.00 % compared to the traditional model's average relative deviation of 60.00 %. Furthermore, it offers a comprehensive discussion on the composition of hydrate structures in (H 2 + CH 4 + C 2 H 6 + C 3 H 8) during gas–water-hydrate equilibrium, providing a more precise depiction of hydrate structure evolution. Additional gas-hydrate equilibrium experiments were conducted for the (H 2 + CH 4 + C 2 H 6 + C 3 H 8) system to optimize the model parameters. The fitting goodness of the hydrate structure transformation formula (n i I - S i formula) is enhanced from 0.9162 to 0.9816. [ABSTRACT FROM AUTHOR]

• We synchronize gas hydration with membrane permeation to improve mass transfer for gas separation. • An accurate formula was developed to calculate the gas consumption during stable growth of hydrate. • We built a dynamic matching model to describe hydrate-membrane synergistic action. • We simulated the separation of H 2 -containing gas mixture by hydrate-membrane coupling method. • Simulation results indicate that the coupling method greatly improves the gas separation effect. The recovery of hydrogen (H 2) form H 2 -containing gas mixtures, such as petrochemical refinery tail gas, plays a important role in energy conservation and cost reduction. The hydrate-membrane coupling separation process has been demonstrated as a more efficient and energy-saving approach for H 2 recovery. This study aims to achieve the synergistic matching of hydration and permeation, so as to explore the underlying mechanisms of coupling and facilitate subsequent experimental studies. In this work, an effective method was developed to calculate the gas consumption rate during the stable growth stage of hydrates. Furthermore, a dynamic matching model of the hydrate-membrane coupling mechanism was employed to simulate the variations in the separation process using infinitesimal methods. The simulations indicate that the H 2 concentration of product gas and the feed gas treatment capacity of the coupling method outperform those of hydrate separation and membrane separation alone. Overall, this study provides valuable insights into an efficient and energy-saving method for H 2 recovery from H 2 -containing gas mixtures, utilizing the hydrate-membrane coupling method. These findings hold promising prospects for practical application in the future. [ABSTRACT FROM AUTHOR]

Recovery of hydrogen (H 2) from H 2 -containing gas mixtures has great significance for energy conservation, cost reduction and benefit increase. However, the common separation methods have the ubiquitous problem due to phase equilibrium principle and results in the conflict between H 2 concentration and H 2 recovery rate in the product gas. Consequently, an innovative conception of hydrate-membrane coupling approach is proposed in this work. In the separation process, hydration and membrane permeation two separation driving forces coexist to achieve the aim of strengthening mass transfer kinetics. H 2 and non-H 2 components (hydrocarbons) are synchronously and directionally selected by membrane and hydrate to improve different phase compositions. Therefore, the gas in feed side could keep relatively high two separation driving forces (H 2 fugacity and hydrocarbons fugacity). The results show that the coupling method could synchronously increase both the concentration and the recovery rate of H 2 in the product gas. At the same time, the volume and concentration of the hydrocarbons in hydrate both increases effectively. It indicates that hydrate and membrane separation methods support each other in the separation process. The hydrate-membrane coupling method fundamentally solves the issue of the decreasing driving force resulting from single separation method and phase equilibrium relationship. Fig. 1. The schematic diagram of directional separation of H 2 -containing gas mixture using hydrate-membrane coupling method. (a) Before separation. (b) After separation. [Display omitted] • We proposed a coupling separation mechanism based on coexistence of two mass transfer processes. • Hydrate-membrane coupling method was used to directionally separate H 2 -containing gas mixture. • The coupling separation method could synchronously increase the concentration and recovery of H 2. • Coupling separation method breaks through the constraint of single phase equilibrium relation. [ABSTRACT FROM AUTHOR]