Pipeline CO2mmissioning: The First Step is the Hardest

Abstract The first introduction of carbon dioxide (CO2) into a new carbon capture and storage (CCS) pipeline is one of the most onerous operations over the asset lifecycle. The emergence of CCS hubs and terminals introduce additional technical challenges for CO2 system operation due to varying CO2 source and composition. The paper addresses a key operation which is a known risk for these emerging projects and provides valuable mitigation insights based on real project design experience. The objective of this paper is to share insights from CCS project initial start-up planning case studies to educate on systems risks and mitigation measures related to this operation. The case studies show that adequately designing for first fill operational flexibility has a first order impact on the pipeline design, and therefore has the potential to result in cost growth if not accounted for early in design. The initial pressure drop from a source of higher-pressure CO2 to an initially lower pipeline pressure can result in very low transient operating temperatures as the CO2 phase changes and expands to lower pressure gas, giving rise to risks to mechanical integrity of the pipeline and risk of water dropout leading to wet CO2 corrosion risks. As the pipeline is then subsequently pressurized, the conversion of lower density gaseous CO2 to higher density liquid CO2 can be an unexpected constraint to commissioning schedule estimates, taking an order of magnitude longer than simple linear predictions might estimate. This paper presents case studies around these challenges, example methods of assessment for predicting these behaviors, and examples of the design and operational levers available to the project design team to plan around these challenges for successful pipeline commissioning. The case studies and example assessment methods presented in this paper consider: The impact that the source of CO2 has, comparing liquid CO2 from vessel transport conditions vs CO2 sourced directly from an emitter. The impact of fluid impurities, comparing a CO2-rich fluid (96 mol% CO2) to a pure CO2 fluid. Dehydration requirements of first fill. The effectiveness that heating the CO2 or sourcing the CO2 from a higher temperature source has on mitigating low temperatures. The effectiveness of increasing the initial pipeline pressure through an initial partial pressurization with dry air or nitrogen. Constraints that may occur due to repurposing an existing hydrocarbon pipeline as compared to a new greenfield pipeline.