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Serious issues regarding the scarcity of freshwater encouraged researchers to work on various methods for seawater desalination. Hydrate-based desalination (HBD) is a novel method that has received investigators’ attention due to its outstanding properties. According to the literature, refrigerant hydrates have great potential to be employed in the HBD process because of their highly moderate phase equilibrium. The main purpose of the current study is to investigate the influence of different concentrations of NaCl (0, 1, 3.5, 5, and 8 wt %) on the major kinetic parameters of R410a refrigerant hydrate formation in the presence and absence of cyclopentane with the concentration of 0.5 mol % as a coformer. The experiments were performed in a stirred laboratory reactor at an initial temperature of 278.15 K and initial pressures of 0.9 and 1 MPa. The measurements of induction time and mole of gas consumption show that NaCl increases the induction time and decreases the amount of gas consumption. However, the addition of 0.5 mol % cyclopentane decreases the induction time slightly and increases the final amount of gas consumed. Besides, despite the fact that cyclopentane decreases the initial rate of gas uptake, it could promote the amount of gas consumption during hydrate formation. The results of the water-to-hydrate conversion ratio illustrated that NaCl with concentrations up to 5 wt % exhibits an insignificant decrease of water-to-hydrate conversion, while 8 wt % NaCl decreases this parameter down to 51.48%. Moreover, the positive effect of cyclopentane on the growth stage was revealed by determination of the apparent rate constant of hydrate growth. This study provides useful data for designing and understanding the HBD process via R410a hydrate formation.

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The effects of addition of an ionic liquid to pure water as a physical absorbent and monoethanolamine (MEA) solutions as a chemical absorbent on carbon dioxide (CO2) absorption through hollow fiber membrane contactors were investigated using a 2D axisymmetric model. A numerical simulation was developed based on finite element method using computational fluid dynamics techniques. Liquid phase flowed in the tube side and gas mixture containing CO2 passed in the shell side of the membrane contactor in co-current and countercurrent modes. The simulation results are consistent with experimental data, and the root-mean-square error was calculated as 9 and 13% for pure water and 25 wt % for ionic liquid solution. The results showed that addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]­[BF4]) to the base fluids increases CO2 absorption in both physical and chemical absorbents. However, the effects of an ionic liquid in physical absorption is higher than that in chemical absorption. Addition of 10 wt % [Bmim]­[BF4] to 3.5 wt % MEA solution could increase the absorption rate by 12% in countercurrent flow compared to a 6 wt % MEA solution without [Bmim]­[BF4] despite lower MEA concentration. Also, the results indicate that reaction term in a chemical absorbent is more important in low liquid flow rates. It can also be found that addition of 25 and 50 wt % of [Bmim]­[BF4] to pure water can enhance absorption performance up to 30 and 75%.

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