CO2 transport–Depressurization, heat transfer and impurities

Abstract Detailed knowledge on depressurization, heat transfer and impurities in CO2 pipelines has shown to be important for safe and cost effective design of CCS chains. The aim of this paper is to present the latest results on the modelling and experimental verification of these aspects. A newly developed CO2 module in the flow engineering software OLGA from SPT Group has been used to model experimental results on depressurization, which is a two-phase transient flow with evaporation and Joule-Thomson cooling. A visual comparison of model and experiments in PT-diagrams showed that the new CO2 module in OLGA captures the depressurization behaviour reasonably well, but still has room for improvement. Heat transfer coefficients for heat transfer from aqueous surroundings to cold CO2 in a pipeline segment was measured in a dedicated rig. A thin layer of ice formation was observed on the bottom of the pipeline. The overall heat transfer coefficient at the experimental conditions has been calculated to be 45.0 W/m2K, where the outer heat transfer coefficient was 162.3 W/m2K, and the inner heat transfer coefficient 166.2 W/m2K. 46 Experiments and modelling of H2O solubility in vapour and liquid CO2 were performed for verifying the VLHE-behaviour at low H2O concentrations down to −50 °C. Hydrafact’s model HWHyd 2.2 model predicted the experimental result with average 8.2% deviation. Hence, the model can be used for setting hydrate formation limited H2O specifications in transport of pure CO2.