Experimental and modelling studies of the phase behaviour and transport properties of mixtures related to carbon capture and storage

Abstract

It is now widely accepted that anthropogenic CO2 emissions produced from the burning of fossil fuels are responsible for the apparent rapid rise in global temperatures recorded over the past century. Worldwide concerns over the threat of global warming have motivated the majority of industrialised countries into working to reduce carbon emissions. CO2 storage in depleted reservoirs and its application in Enhanced Oil/Gas Recovery (EOR) are among techniques being suggested for reducing the emission of this greenhouse gas. The main aim of this research is to develop a thermodynamic model from an accurate equation of state (EoS) for typical components of reservoir fluids and flue gases. The SAFT-VR Mie EoS was selected to study the phase behaviour and transport properties of mixtures related to carbon capture and storage (CCS). Four EoSs have been compared (PR, SRK, PC-SAFT and SAFT-VR Mie) by modelling density and vapour-liquid equilibria (VLE) data from the literature of 22 pure components and 108 binary systems of gases (CO2, H2S, N2, O2, Ar, CO and SO2), n-alkanes and aromatics. Isothermal vapour-liquid equilibrium of H2S - Ar binary system was determined experi-mentally at three temperatures from 273 to 323 K. Densities of five H2S binary systems (three CH4-H2S systems with 13, 18 and 28 % of acid gas, C2H6 - 34% H2S and C3H8 - 13% H2S) were measured continuously at 3 temperatures (253, 273 and 293 K) and at pressures up to 30MPa, using a vibrating tube densitometer, Anton Paar DMA 512. Following the same technique, the density of the ternary system 42% CO2, 40% CH4 and 18% H2S was measured at pressures ranging from 0.2 to 31.5 MPa and at 6 temperatures between 253 and 353 K. Three transport properties were modelled with SAFT-VR Mie and two models based on density predictions from the EoS. Density, viscosity and interfacial tension (IFT) of CO2-rich systems were calculated by the SAFT-EoS (density), TRAPP model (viscosity) and DGT (IFT), for system of interest to CCS. Densities and viscosities of a multicomponent mixture of 50% CO2, 40% CH4 and 10% of other impurities were measured at 5 temperatures between 283 and 423 K and at 2.5-150 MPa pressure range, using an Anton Paar densitometer and the capillary tube technique for viscosity measurements. These experimental data continued studying the impact of impurities on the viscosity and density of CO2-rich systems.