Developing a new equation of state for carbon capture and storage pipeline transport

As the development of more advanced capture and storage technologies continues along with gradual scale-up of demonstration projects, the imminent deployment of commercial-scale carbon capture and storage is becoming increasingly likely. The transport stage needs to undergo similar development as there is much that needs to be better understood. In particular, there is a need for an equation of state which can accurately describe the physical behaviour of mixtures of carbon dioxide with impurities during the transport stage of carbon capture and storage in a simple, effective way. Presented here is the early development of a new, analytic equation of state, specifically designed to be highly accurate within the window 0 to 30.9782 degrees C and up to 150 bar (the anticipated usual region of operation for carbon capture and storage pipelines). In this paper, the potential of the proposed equation of state is demonstrated with descriptions for the pressure (from which density can be directly calculated) and phase behaviour of pure CO2. Comparisons with the Peng-Robinson equation of state are made in order to demonstrate the potential of the model, which has both simplicity similar to that of the Peng-Robinson equation and accuracy similar to that of the Span-Wagner equation. Presently, it is found that inside this window, the maximum percentage error of the new equation in the description of pressure for the case of pure carbon dioxide is not more than approximately 2.53%, compared with 40.85% for the Peng-Robinson equation, whilst for the description of phase behaviour, it is not more than 2.41%, compared with 18.23% for the Peng-Robinson equation.