CO₂ Dynamics

Transport of CO₂ in pipelines is a key technology to enable large scale CO₂ capture and storage (CCS). CO₂ Dynamics contains several flow model formulations and thermodynamic equation of states in order to be able to simulate CO₂ pipe flow under various conditions and fluid compositions. In particular, the robust numerical methods handle fast transients, discontinuities and wide or narrow phase envelopes. This tool may be used to study depressurization and distribution of state variables like temperature. CO₂ Dynamics has an interface to Thermopack for access to thermodynamic property models. Examples of engineering applications are pipeline design, estimation of how much CO₂ is flowing, the lowest occurring temperatures and running fractures.

Validation

CO₂ Dynamics has been validated against various experimental data. An example is depicted in the figure below for the depressurization of a 200 m pipe, where one end of the pipe was opened to the atmosphere while the other remained closed. As a consequence, temperature and pressure starts falling in the pipe.

The temperature calculated with CO₂ Dynamics was compared to experimental data from DNV GL. at a point 5 meter from the closed end of the pipe. Two different heat-transfer models were used ('C' denotes Colburn and 'GW' denotes Gungor-Winterton). In this case, the Colburn heat-transfer correlation gives better results. The reason for the large difference is the occurrence of solid CO₂ (dry ice). This can be seen as a kink in the experimental data (and in our calculation) at time about 40 s. The Gungor–Winterton correlation gives too high heat transfer, such that the CO₂ does not enter into the area where solid CO₂ is formed. As can be seen, the solid CO₂ contributes to keeping the temperature low.

This calculation shows that CO₂ flow and depressurization models must be able to account for the formation of solid CO₂. Secondly, it is important to model the heat transfer through the pipe wall to the surroundings.

Further reading:

• CO₂ transport
• #SINTEFblog: Flow of CO₂ in pipes