CO2 originating from capture processes is generally not pure and can contain impurities such as N2, H2, CO, water, SO2, NO2, Ar (i.e., annex gases). The presence of these impurities leads to challenging engineering, flow assurance issues, as well as an increase in the significant processing costs. The presence of water may result in ice and/or gas hydrate formation and cause blockage. Furthermore, the gaseous CO2-rich stream is generally compressed to be transported as liquid in order to avoid two-phase flow and increase the density of the system. The presence of the above impurities will also change the physical properties of the stream, i.e., the system’s bubble point pressure and viscosity, hence affecting the compression requirement. Furthermore in the majority of feasibility studies of CO2 injection, the effects of these impurities have been overlooked or completely ignored.
The aim of this proposal is to investigate the phase behaviour of carbon dioxide in the presence of impurities such as N2, O2, H2, CH4, SO2, SO3, NO, NO2, CO, H2O and sometimes H2S with particular emphasis on low temperature conditions as well as developing a general phase behaviour/equilibrium predictive model. The work programme will be an integrated experimental and modelling study focusing on the effect impurities on the phase behaviour (VLE, solubility in saline water, hydrate, solid formation) and fluid properties (density, viscosity) of CO2-rich mixtures.
The aim of the proposed project is to investigate the phase behaviour of CO2-rich stream. The specific objectives are as follows:
- To identify the gap in the phase behaviour (VLE, solubility in saline water, and hydrate stability data) and fluid properties (viscosity and density) for CO2-impurities systems (N2/O2/CO/H2/H2S/SO3/NO/NO2/CH4),
- To determine the hydrate stability as a function of pressure, temperature and water content for the above systems.
- To determine the dehydration requirements of CO2 and of representative multicomponent systems over a wide range of pressure and temperature.
- To quantify the effect of these impurities on the viscosity and density of CO2 over a wide range of pressure and temperature conditions.
- To explore the effects of the above impurities on the solubility of CO2 rich systems in water and brine.
- To develop/tune predictive tools to predict the phase behaviour (including solubility), hydrate stability and dehydration requirement for CO2 rich systems.