Discussion on essential points in Chinese and foreign standards for CO₂ pipeline design

Objective Carbon capture, utilization, and storage (CCUS) have gained significant attention due to their direct role in reducing carbon emissions. As a crucial element within the CCUS framework, the construction of CO₂ pipelines has consequently experienced rapid development. To ensure the overall safety of pipeline systems during construction and operation, it is crucial to conduct a thorough analysis of the relevant provisions contained in specifications pertaining to the design of CO₂ pipelines.

Methods This study investigated and reviewed the development history and current status of major Chinese and foreign standards applicable to CO₂ pipelines, with a specific focus on essential aspects and key points that require attention, including pipe selection, CO₂ dehydration, valve chamber placement, as well as pipeline venting, drying, sealing, and storage.

Results This study yields the following results. To accommodate the unique characteristics of CO₂, the selected pipe should be suitable for the transmission phase of CO₂ and capable of withstanding low-temperature impacts that may occur during the decompression process. The spacing and location of valve chambers along CO₂ pipelines shall be designed, taking into account factors such as the pipeline route, and locations of relief and venting facilities. Proper precautions should be taken to address potential threats to personnel health and the environment, especially in dense-phase/supercritical CO₂ relief and venting conditions, which generally involve low temperatures and potential accumulation in low-lying areas. Careful consideration should be given when routing CO₂ pipelines to avoid passing through high-lying sides of densely populated areas. Effective dehydration of CO₂ gas sources is crucial as a primary control measure against internal corrosion, a major failure mode of CO₂ pipelines. Given the weak acidity of CO₂ when dissolved in water and its propensity to form hydrates, strict moisture control is essential during the drying process in pipelines. In the absence of immediate commissioning, CO₂ pipelines should be filled with nitrogen and sealed to maintain a gauge pressure ranging from 0.05 to 0.07 MPa.

Conclusion China is currently in the early stage of developing standards for the CO₂ pipeline sector, and numerous wellestablished foreign standards can serve as valuable references. Additionally, conducting experimental research on CO₂ pipeline leakage is urgently needed to gather more data, which will enhance the references available for the design, construction, and formulation of CO₂ pipeline standards in China.