Carbon dioxide CO2 capture and storage (CCS) is a key technology to facilitate the reduction of anthropogenic CO2 emission to the atmosphere. The transport of CO2 from the source of emission to the storage sites is likely realised with pipelines. Although there is the perception that CO2 transportation in pipelines does not impose a significant barrier, there is limited experience in the field as compared to transporting natural gas and a number of issues has already been identified that need to be understood before being able to manage the risks associated to the transportation of CO2. With these having been solved, there will be a need to develop recommendations and standards to be used for design and operation of CO2 pipelines.
EPRG launched a project to contribute to the understanding of specific issues related to the safety of steel pipes for anthropogenic CO2 transportation pipeline systems. The activity was partly funded by the Research Fund for Coal and Steel (RFCS).
A series of advanced and extensive experimental activities have been conducted to address specifically the following items:
- unstable fracture propagation control
- fracture initiation control
- corrosion and stress corrosion control
Special thoughts were given to define relevant mixtures of CO2 that reflect potential scenarios in this context, such as pre- and post-combustion as well as oxyfuel mixtures.
Fracture initiation was studied to confirm that CO2 does not pose any additional challenges in this context. The temperature of the expanding gas has an important impact on the properties of the surrounding material, and in turn on the resistance to fracture.
As CO2 is an especially demanding gas in terms of fracture propagation, crack arrestors and composite reinforced pipes were included in the full scale fracture propagation test line.
Several seminal results were achieved. Knowledge of hazard distances and inaccessible time regarding the area of release are of importance for the design and operation of pipelines. The studies identified the maximum dispersion distance of CO2 clouds and revealed that these could accurately be modelled with dedicated FE codes.
The analysis of the set of full scale propagation tests showed that more data is needed to identify a unique design formula for CO2 pipelines. For the time being, it is recommended conduct project-specific assessments accounting for individual sets of parameters.
Corrosion resistance of pipes and girth welds was studied for various concentrations of impurities (H2S, H2O, NOx , or SOx ). Concerning the stress corrosion tests, the results obtained in the project were very promising even if not enough to complete due to the limited statistics and the very small quantity of data in public literature.