The recovery of hydrogen (H2) form H2-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 H2 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 H2 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 H2 recovery from H2-containing gas mixtures, utilizing the hydrate-membrane coupling method. These findings hold promising prospects for practical application in the future.

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.

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.

水合物法回收油罐挥发气(VOCs)具有高效、低能耗和清洁无污染的优势.四丁基溴化铵(TBAB)和十二烷基硫酸钠(SDS)分别为常用的热力学促进剂和动力学促进剂.TBAB-SDS复配溶液中CH4水合物相平衡实验的结果表明,SDS的引入提高了TBAB溶液中CH4水合物的相平衡压力,表现出抑制水合物生成的效果.其抑制作用随着SDS和TBAB浓度的增加而增加,随着温度的升高而降低.该研究为水合物法回收VOCs提供基础实验数据并指导后续的方案设计.

Recovery of hydrogen from hydrogenation tail gas plays an increasingly important role as hydrogen is a clean and efficient energy source in petrochemical industry. Hydrate separation process is a high-efficiency and energy-saving hydrogen recovery technology. We are committed to the industrialization of hydrate separation process, and has completed a preliminary pilot test in Maoming Petrochemical Company. This work aims to conduct the process modeling and optimization of hydrate separation. The improved Chen-Guo model is used to simulate the mass transfer units (hydrate flash reactor, hydrate dissociation reactor), and the process simulation is realized by calling Excel in the Aspen Plus environment through the interface toolbox. After optimizing the key process operating parameters, the results show that decreasing flash temperature instead of increasing flash pressure can improve the energy utilization efficiency. Compared with the pilot test, the total energy consumption of optimization is reduced from 138.60 kW to 111.77 kW, saving 19.36% of energy consumption, and the energy consumption of optimization for rising hydrogen mole fraction by 1% per mol product gas is 2.277 kJ/mol, which is 15.88% lower than that of pilot test (2.707 kJ/mol). (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hydrogen-containing gases commonly used in industry often contain many light hydrocarbons. The change of light hydrocarbons composition will cause the transformation of hydrate structure, which is one of the important reasons for reducing the calculation precision of hydrate thermodynamic model. Therefore, for the light hydrocarbon mixed system, a new hydrate structure parameter（n i I ） is introduced into the core equation of Chen-Guo hydrate model, and its coefficients are obtained by fitting experimental data, which can be used to judge and calculate the sⅠ/sⅡ hydrate transition. On this basis, hydrogen in hydrogen-containing gas is regarded as an inert gas adsorbed only by small cavities（link cavities） of hydrate, and an improved model considering hydrate structural transition is proposed to improve the prediction accuracy of hydrogen-containing gas. The calculated results show that the average relative deviation of the improved model for different light hydrocarbon gases is reduced from about 5.6% to 2.1%, and for different hydrogen-containing gases is reduced from about 8% to 2.3%. The prediction accuracy of the model has been significantly improved, which can meet the requirements of engineering applications.

The study on phase behavior and physical properties ofnaturalgas has great significance for its safe exploitation and transportation.Consequently, we studied the phase equilibria of the methane + ethanegas mixture in this work. The hydrate formation conditions (gas-liquid-hydrateequilibria) of the methane + ethane gas mixture were measured firstin pure water. Then the gas solubility (gas-liquid equilibria)of the gas mixture in water was measured with/without hydrate. Finally,the bubble point and dew point (vapor-liquid equilibria) andthe hydrate formation conditions and gas solubility in the presenceof hydrate were calculated. The results show that before hydrate formation,the gas solubility in water decreases with temperature and increaseswith pressure. However, after hydrate formation, the gas solubilityincreases with temperature and decreases with pressure. The calculationmodels in this work have satisfactory accuracy for phase equilibriaprediction of the methane + ethane gas mixture. Therefore, it hasa good guiding significance for describing the phase behavior of naturalgas.

水合物法回收混空煤层气中的甲烷具有清洁高效和操作安全的优势.为了探究四丁基溴化铵(TBAB)和辛基-β-D-吡喃葡萄糖苷(OGP)两种促进剂的协同作用,完成了TBAB+OGP复配溶液中甲烷水的合物相平衡实验.结果表明,TBAB显著降低了甲烷水合物的生成压力,但是OGP的引入减弱了TBAB的热力学促进作用.其削弱作用随着OGP和TBAB浓度的增加而增加,随着温度的升高而降低.该研究为水合物法回收煤层气提供基础实验数据并指导后续的方案设计.

Accurate prediction of hydrate formation conditions is the basis of hydrate related research. The ChenGuo hydrate model could accurately predict the formation conditions of hydrates. However, the misjudgment of basic hydrates structure makes it unsatisfactory to calculate the system with sI and sII hydrates coexisting. Consequently, we proposed that sI and sII basic hydrates will be formed simultaneously under specific conditions. The structure composition of basic hydrates is influenced by three factors: structure induction, driving force of hydrate independent nucleation and composition of gas mixture. On this basis, we improved the Chen-Guo hydrate model by introducing new parameters and adjusted the true structure composition of basic hydrates. The calculation results show that the average absolute deviation of 201 sets of data can be reduced from 9.33% to 2.74%. The calculation precision of modified method is better than that of the original Chen-Guo hydrate model. (c) 2022 Elsevier Ltd. All rights reserved.

Recovery of hydrogen (H2) from H2-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 H2 concentration and H2 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. H2 and non-H2 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 (H2 fugacity and hydrocarbons fugacity). The results show that the coupling method could synchronously increase both the concentration and the recovery rate of H2 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.

Pipe plugging and cracking caused by gas hydrate blockage is the major problem in oil/gas flow assurance, especially in deep subsea pipelines. Thermodynamic inhibitors(THIs) are one of the effective methods to inhibit the formation of gas hydrate. This work evaluates the thermodynamic inhibition effect of D-sorbitol, a polyhydroxy compound, for both methane (CH4) and carbon dioxide (CO2) hydrates. The gas-liquid-hydrate equilibrium (GLHE) conditions for CH4 and CO2 were measured by the isothermal pressure search method in the presence of aqueous D-sorbitol solutions (1.00, 2.00, 3.00 mol%). The equilibrium pressure change (?P) and hydrate dissociation enthalpies (?Hdiss) were used to reflect the thermodynamic effects of D-sorbitol on CH4 and CO2 hydrates. The ?P data show that D-sorbitol has an obvious inhibition impact on CH4 and CO2 hydrates formation. Compared with deionized water system, CH4 hydrate GLHE pressure increased by 11.6, 25.0, 41.4%, while CO2 hydrate GLHE pressure increased by 10.1, 18.6, 32.7% in 1.00, 2.00, 3.00 mol% D-sorbitol solutions, respectively. The ?Hdiss data demonstrate that D-sorbitol does not participate in the formation of the hydrate crystal structure. Chen-Guo hydrate thermodynamic model and Wilson activity model were applied to predict the GLHE conditions of both CH4 and CO2 hydrates in the presence of D-sorbitol. The calculated results can well match the experimental values. The average relative deviations (ARD) between calculated and experimental data for CH4 and CO2 hydrate are less than 2.39% and 3.76%, respectively. D-sorbitol is a non-toxic and environmentfriendly compound. The results in this work indicate that D-sorbitol can be applied to flow assurance strategies for hydrate blockage prevention.