Measurement and correlation of phase equilibria for water + hydrocarbon systems near the critical temperature and pressure of water

An experimental apparatus based on a flow method was constructed in order to measure the phase equilibria for water+hydrocarbon systems near and above the critical temperature of water in the high-pressure region. The phase equilibria were measured for the water+decane system at 573.2 K from 12.1 to 30.3 MPa and at 593.2 K from 15.4 to 25.1 MPa and for the water+toluene system at 553.2 K from 15.1 to 30.1 MPa and at 573.2 K from 17.2 to 30.5 MPa. The phase equilibria of the water+decane system at 573.2 and 593.2 K and of the water+toluene system at 553.2 and 573.2 K are correlated by a modified SRK (MSRK) equation of state, which is modified in the attractive term of the SRK equation of state to calculate well the saturated vapor pressures of many organic and inorganic compounds. An exponent-type mixing rule, which uses empirical exponential parameters showing deviations from random mixing, is applied to the energy parameter a, and a conventional mixing rule is applied to the size parameter b. Good correlation results are obtained.