A method for calculating the liquid density for the CO2–H2O–NaCl system under CO2 storage condition

Abstract

A liquid density model for the H2O–CO2–NaCl ternary system is established, based on previous methods (Duan et al. Energy & Fuels 2008, 22, 1666–1674), and combined with a recent density model for H2O–NaCl binary solution (Mao and Duan. The Journal of Chemical Thermodynamics 2008, 40, 1046–1063). The applicable range of the model is 273–573 K, 0.001–1000 bar and 0–6 mol/kg NaCl concentration as well as CO2 concentrations from 0 up to saturated conditions. The model is accurate and its total error is within 0.5%. The applicable range totally covers conditions for geological storage of CO2. Therefore it is suited for simulation studies of CO2 geological storage, especially for fluid convection processes due to density differences. In order to facilitate the model application, a Matlab© program is provided which can be downloaded from our web page. Three examples are presented to demonstrate the model application. The first one is the calculation of pure water density varying with pressure at different temperature conditions. Second application is on the fluid density calculation under different CO2 saturations which is relevant for convection process simulation. The last application shows the total pressure change caused by temperature changes under isometric conditions.