THE WATER-CONTENT OF ETHANE, PROPANE AND THEIR MIXTURES IN EQUILIBRIUM WITH LIQUID WATER OR HYDRATES

Experimental results for the water content are reported for the ethane -rich phase in the liquid and gaseous states in equilibrium with hydra tes for pressures of 360 psia (2.483 MPa) and 500 psia (3.448 MPa), an d at temperatures from -27.5-degrees-F (-33.1-degrees-C) to 50.9-degre es-F (10.5-degrees-C), as well as in the three-phase coexistence non-h ydrate conditions at pressures ranging from 500 psia (3.448 MPa) to 70 0 psia (4.828 MPa) and temperature from 60-degrees-F (15.6-degrees-C) to 89-degrees-F (31.7-degrees-C), respectively. Also included are the water content measurements of the propane-rich phase in equilibrium wi th hydrates covering temperatures from -35.5-degrees-F (-37.5-degrees- C) to 37.4-degrees-F (3.0-degrees-C) at a constant pressure of 159 psi a (1.097 MPa). Above the hydrate region the experimental conditions ra nge from 48-degrees-F (8.9-degrees-C) to 80-degrees-F (26.7-degrees-C) and pressures of 90 psia (0.621 MPa) to 130 psia (0.897 MPa). Isobari c water content data at 600 psia (4.138 MPa) for the liquid hydrocarbo n-rich phase are reported for four ethane-propane mixtures containing 30.5, 50.0, 75.0 and 89.5 mol% ethane with the remainder propane, in e quilibrium with liquid water or hydrate at temperatures ranging from - 0.4-degrees-F (-18-degrees-C) to 77-degrees-F (25-degrees-C). The wate r content data for two binary systems, ethane-water and propane-water, and four ternary systems, ethane-propane-water mixtures, have been us ed to estimate the equilibrium conditions for three-phase coexistence: (liquid water-liquid hydrocarbon-hydrate I or II, liquid hydrocarbon- hydrate I-hydrate II), and for a quadruple point (liquid water-liquid hydrocarbon-hydrate I-hydrate II). Equilibrium constants for water in the hydrocarbon-rich phases, i.e. the ratio of mole fraction of water in the gaseous hydrocarbon-rich phase to that of water in the liquid h ydrocarbon-rich phase, are graphically presented along the three-phase coexistence locus, and along the non-hydrate conditions for the ethan e-water and the propane-water systems.