Experimental measurement and thermodynamic modelling of clathrate hydrate equilibria and salt solubility in aqueous ethylene glycol and electrolyte solutions

Methane hydrate phase equilibria for systems containing NaCl, KCl, and NH 4 Cl

“…The isochoric method is the conventional technique for measuring hydrate phase equilibria based on the variation of the system pressure with temperature while keeping the volume constant [1,[15][16][17][18][19][20][21]. The hydrate phase equilibrium condition is determined by the intersection of tangents of the cooling and heating curves in the temperature and pressure trace data, which means that the hydrate equilibrium conditions highly depend on the heating curve [15][16][17][18][19][20][21].…”

“…The hydrate phase equilibrium condition is determined by the intersection of tangents of the cooling and heating curves in the temperature and pressure trace data, which means that the hydrate equilibrium conditions highly depend on the heating curve [15][16][17][18][19][20][21]. Several studies have given considerably focus on the accurate measurements of hydrate phase equilibria through different heating paths, such as continuous and step-wise heating methods [15][16][17][18][19][20][21]. Investigations on the hydrate phase equilibria with continuous heating were studied by several groups [15,16], while Tohidi et al [17] used a step-wise heating method and reported less scattered and more accurate data for hydrate phase equilibria.…”

“…Therefore, Tohidi et al [18] suggested a less time-consuming technique with the step-wise method and reported that three equilibrium points from three step-wise heating are sufficient for obtaining clear data points for hydrate phase equilibria. In addition, they also measured the phase equilibrium conditions of pure gas hydrates as well as gas hydrates in the presence of inhibitors [19][20][21]. The concentration of aqueous salt solution in the system containing hydrate and salt solution continuously changes during the hydrate formation and dissociation processes.…”

Thermodynamic modeling of gas hydrate formation conditions in the presence of organic inhibitors, salts and their mixtures using UNIQUAC model

“…Chin et al [16] This work Nasrifar et al [10] Masoudi et al [17] Nasrifar and Moshfeghian [12] Javanmardi et al [13] Mohammadi and Tohidi [7] Chin et al [16] This work …”

“…By applying the COSMO-SAC activity model along with the PitzerDebye-Hückel model, Chin et al [16] predicted gas hydrate formation conditions of pure gases in the presence of alcohols, salts and their mixtures so that their modeling does not require any interaction parameter. On the other hand, in f-f approach, Masoudi et al [17,18] considered the critical properties of electrolytes so that the salts are treated as pseudo-components in the VPT EoS along with a NDD mixing rule. Mohammadi and Tohidi [19] combined the VPT EoS along with the NDD mixing rules and a modification of Debye-Hückel electrostatic term.…”