Water/CO2 System at High Pressure and Temperature Conditions: Measurement and Modeling of Density in Equilibrium Liquid and Vapor Phases

Abstract

Abstract Accurate density description of saturated liquid and vapor (L-V) phases for the water-CO2 system is important in many fields of engineering and science such as CO2 sequestration, supercritical fluids-based extraction and purification processes, and CO2- related enhanced oil recovery methods. There are only a few studies, mostly dedicated to low pressure and temperature conditions, on densities of equilibrium liquid and vapor phases for this system. Due to paucity of experimental data at high pressure and high temperature conditions, a series of experiments have been performed to measure the density of both liquid and vapor phases of water/CO2 system from 382 K to 478 K and pressures from 3.48 MPa to 129 MPa. In order to measure the mass of water and volume of gas in the vapor phase, in each experiment the vapor phase of an LV equilibrium system is transferred to an equilibrium flash separator equipped with a desiccant and a gasometer. The gas volume is converted to density based on the ideal behavior of gases at standard conditions. The density of the liquid phase is directly measured by a densitometer. In addition, a "Two-fluid Model" consisting of the Cubic-Plus-Association equation of state (CPA EOS) and the Henry's law is implemented in phase equilibrium modeling of this system to predict the density of both phases. A comparison between our experimental data, literature data and the results of the model shows the reliability of this model for density prediction of L-V phases of water-CO2 system over a wide range of pressure and temperature conditions.