The CO2-H2O system. I. Experimental determination of volumetric propertiesat 400 degrees C, 10-100 MPa

Densities of pure CO2 and CO2-H2O mixtures were experimentally determined a t 400 degrees C, 10-100 MPa. The data were obtained with a custom-designed high-pressure, high-temperature vibrating-tube densimeter. Conservative est imates of accuracy are P, +/- 0.02 MPa, T, +/- 0.05 degrees C, and rho +/- 0.0005 to 0.0010 g.cm(-3) for low- and high-density mixtures, respectively. Excess molar volumes (V-ex) for mixtures are continuously positive, increa sing sharply from 0 MPa to maximum values near 30 MPa. Above 30 MPa, V-ex d ecreases rapidly with increasing pressure. Peak values for V-ex are large, representing up to 37% of total volume. The isobaric data (V-ex vs. X-CO2) are nearly symmetric at pressures below 10 MPa, but become strongly asymmet ric toward H2O with increasing pressure above 10 MPa. The highest degree of asymmetry coincides with P-T conditions at the critical isochore for pure H2O (similar to 29.2 MPa at 400 degrees C). With increasing pressure above 30 MPa, asymmetry of the isobaric data shifts toward CO2 Densities for pure CO(2)at 400 degrees C, 10-100 MPa, predicted by published equations of sta te are in fair to excellent agreement with our experimentally determined de nsities. Previously published density data for mixtures, and excess molar v olumes calculated from equations of state, are generally in poor agreement with our results. Copyright 0 1999 Elsevier Science Ltd.