The density of the H2–CO2–CH4–CO–H2O system
in the supercritical
region of water is significant for analyzing the gasification process
of organic substances in the supercritical water. We report density
measurements of the quinary system by the isochoric method at 722–930
K and 15.4–30.3 MPa. The upper limit of the expanded uncertainty
at 95% confidence for temperature is 0.2 K. The upper limits of the
expanded relative uncertainties at 95% confidence for pressure and
density are 0.0006 and 0.0125, respectively. The density data were
compared with those predicted using the GERG-2008 equation of state.
The absolute relative deviations between the calculated and experimental
densities are not more than 1.79%. Furthermore, the excess volume
of the quinary system decreases monotonically with the increase of
temperature in the isochoric process at 722–930 K. The thermal
expansion coefficients of the quinary system were also determined.