WORK PACKAGE 2: PHASE AND DEW POINT DETERMINATION AND MODELLING

LEADER: DR T. DRAGE

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One of the main constraints on the design and specification of a CO2 pipeline system containing impurities from power plant is the lack of experimental data describing the phase behaviour of the CO2 stream and also the solubility limits for water in that stream. Knowledge of the CO2 behaviour is critically required for accurate pipeline hydraulic and fracture propagation modelling and for the specification of the drying requirements of the CO2.

In this work package, phase determination and solubility experiments will be conducted by an interdisciplinary team at Nottingham involving the Chemistry, Mathematics and Chemical Engineering Schools in three sub-work packages. University of Nottingham is a world-leader in conducting experiments of this nature and details of the expertise and facilities that will be utilised in this work package are detailed in the Appendix. However, an overview of the methodology to be adopted is provided in the following sections.

WP2.1 – Precise Gas-Liquid Phase Boundary and Thermodynamic Property Measurements (Prof M. Poliakoff)

Pipeline hydraulic and fracture propagation modelling requires the calculation of fluid properties using appropriate equations of state. There is no consensus in the literature regarding the equation of state that should be used for the design of CO2 pipelines and also limited experimental data on which to verify the most appropriate equation to use and to validate the hydraulic and fracture models.

In WP2.1, the detailed experiments required to define the phase boundaries for binary and ternary mixtures at pressures and temperatures relevant to CCS will be conducted. The requirements for these experiments will be determined from the output of WP1 and also agreed with the WP leaders of WP3 and WP6 who will use these results in the models.

In addition, property measurements such as density, entropy and viscosity will be made in this task. This data is critical for the verification of pipeline hydraulic models (WP3) in particular, but will also benefit the wider CCS research community, for example, in the modelling of the movement of CO2 in rock formations.

WP2.2 Modelling of High Pressure CO2 Phase Behaviour (Dr R. Graham)

As mentioned previously, one of the major outputs of this work package will be the experimental data on which to verify the most appropriate equation of state for CCS applications. Therefore in this work package existing equations of state will be tested against the experimental data generated within the project and the results used to improve the prediction of high pressure CO2 phase behaviour. The output of this WP will be utilised in the hydraulic and fracture models utilised in WP3 and WP6.

WP2.3 – Determining Conditions Needed to Avoid Liquid-Liquid Separation or the Formation of a Water-rich Phase (Prof M. Poliakoff)

In the transport of high concentrations of CO2 it is critical that free water is not allowed to form in the pipeline and therefore the amount of water present in the CO2 stream must not exceed the solubility limit under the prevailing conditions of temperature and pressure. The presence of impurities changes the solubility limits and therefore the drying requirements for the transported CO2. This task aims to determine the changes in water solubility with changes in impurities in the CO2 using dew point experiments to determine the required specifications for drying CO2 and the conditions under which free water may form in the pipeline. The results of this work will define the test environments of WP4 and WP5.