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

In this contribution, a generalized method for predicting gas hydrate formation conditions in the presence of aqueous solutions, HL1V calculations, is developed. Each phase is characterized separately. In this respect, the equation of Nasrifar et al. for calculating the activity of water in the presence of electrolytes and an alcohol is extended to water in various mixtures of electrolytes, alcohol and dissolved gas. An equation for calculating the activity of water in the presence of mixtures of electrolytes is also developed. These equations are then used to characterize the aqueous phase in HL1V calculations. The modified Patel-Teja equation of state is used to characterize the vapour phase and the statistical model of van der Waals and Platteeuw for the hydrate phase. The proposed model is then compared with experimental results and other available models. No adjustable or curve-fitting parameters are used. The agreement with experimental results is very good. The comparison with other models also indicates that the proposed model predicts incipient hydrate formation conditions as good as the other models and in most cases even better. (C) 2001 Academic Press.