(386e) From Cradle to Burial: High Pressure Phase Equilibrium Behaviour of CO2 During CCS

The safe and efficient operation of the entire Carbon Capture and Sequestration chain requires a good understanding of the thermodynamics phase behaviour of CO2. Such information impacts anything from the efficiency of the capture technologies employed, the mechanical integrity of the high pressure pipeline system used for transporting CO2 to the likelihood of the escape of CO2 from geological sequestration sites.

Although significant progress has been made in the development of equations of state for predicting the phase behaviour, all of this work has so far been confined to either pure CO2 or hydrocarbon mixtures containing small amounts of CO2.

Little work on the efficacy of these equations of state for CO2 containing different types of impurities has been conducted. In practice, during CCS, depending on the capture technology, the presence of different impurities such as N2, NOx and SOx within the CO2 stream will be inevitable.

This paper reports data based on a comparison of the performance of the Peng Robinson against the Modified Peng Robinson equations of state in predicting the phase equilibrium behaviour of CO2 in the presence of impurities, especially around the critical region. This is the followed by an examination of the depressurisation thermodynamics trajectory of the CO2 mixture following accidental escape during its transportation to capture using a hypothetical 100 km long , 0.6 m i.d pipeline operating at 110 bara and 32 oC .