Phase equilibrium measurements for semi-clathrate hydrates of the (CO2+N2+tetra-n-butylammonium bromide) aqueous solution systems: Part 2

Equilibrium pressures for dissociation of the carbon dioxide (CO2)+ nitrogen (N-2)+ tetra-n-butylammonium bromide (TBAB) + semi-clathrate (sc) hydrates have been experimentally measured to determine the stability regions and dissociation conditions of mixed CO2 + N-2 + TBAB semi-clathrate hydrates. Semi-clathrates have been formed with the addition of TBAB aqueous solutions with mass fractions of (0.05 and 0.30). The relative molar fractions of CO2 in the feed gas were (0.151, 0.399, and 0.749). Hydrate dissociation conditions have been measured using an isochoric pressure search method in the 275.1-291.0 K temperature range and 0.67-19.07 MPa pressure range. The obtained experimental clathrate hydrate dissociation data have been compared with the predictions of two thermodynamic models, namely CSMGem and HWHYD, available in open literature. Finally, the thermodynamic promotion effects of TBAB in aqueous solutions are discussed in terms of hydrate dissociation pressures and temperatures and consequently the most favorable operating conditions are proposed. (C) 2012 Elsevier B.V. All rights reserved.