Prediction of equilibrium conditions for gas hydrate formation in the mixtures of both electrolytes and alcohol

A model for prediction of gas hydrate formation conditions in aqueous solutions containing electrolytes and/or alcohol

“…This model can be solved for dissociation pressure of hydrates at a given temperature or for hydrate formation temperature at a given dissociation pressure. There are, however, models that are generally solved for temperature, e.g., the models of Nasrifar et al (17,18) and Javanmardi et al (13) Therefore, when these models are used to compare with the proposed model, the average of absolute temperature difference (a.a.t.d.) is applied as a measure of statistical errors.…”

“…Among the six mixtures containing CaCl 2 , the proposed model predicts the methane hydrate-forming temperatures better than EB for four mixtures. Table 2 contains the a.a.t.d.s of the proposed model, Nasrifar et al (17) (NMM), EB and JMM for the prediction of gas hydrate-forming temperatures in different aqueous solutions. For prediction of propane hydrate in the presence of aqueous mixed electrolyte solutions, it was found that for 31 experimental data points, the proposed model with an a.a.t.d.…”

“…He observed this maximum at T = 277.2 K and 10.2 mass per cent NaCl solution. Figure 4 illustrates Table 2 also compares the ability of the proposed model with Nasrifar et al, (17) NMM, for the prediction of hydrate forming temperatures of a natural gas in mixed electrolyte and methanol solutions noting in equation (9) a w,gas is equal to 1. The average of a.a.t.d.s for the proposed model for 52 data points is 1.11 K in comparison with 1.46 K for NMM.…”

“…Nasrifar et al (17) derived a simple equation in which, for an aqueous solution containing electrolytes and an alcohol, the activity of water is calculated by:…”

“…However, when the gas hydrate former is a highly soluble gas such as CO 2 that can effectively alter the water activity, the models of Englezos (14) and Tse and Bishnoi (15) are of great importance for the prediction of CO 2 hydrate-forming conditions in the presence of electrolytes. Finally, if both electrolytes and an alcohol are present, the models of Yousif and Young (16) and Nasrifar et al (17,18) can be used to predict incipient hydrate formation conditions. Each of the above models is specific for the prediction of hydrate formation conditions in different aqueous solutions and the use of them for out of their range of applicability may result in large errors.…”