March 2025, Vol. 252, No. 3
Guest Perspective
Advancing CO₂ Transport Infrastructure
Antonio Lucci, Global Energy Transition Strategic Streams director, RINA
(P&GJ) — The global push for net-zero carbon emissions is intensifying and with it, the need for robust carbon capture, utilization and storage (CCUS) solutions.
Safe and efficient transport of carbon dioxide (CO2) is going to be essential for CCUS to meet its potential and that requires developing a strong infrastructure, using innovative technologies together with clearly defined regulatory frameworks.
A critical component of CCUS is the transport of carbon dioxide (CO2), a process requiring sophisticated infrastructure capable of addressing the chemical, thermodynamic and regulatory challenges unique to this greenhouse gas.
Developing infrastructure to transport CO2 requires not only innovation in pipeline materials and monitoring systems, but it also requires a deep understanding of how impurities and operating conditions affect transport efficiency and safety.
Organizations such as RINA are at the forefront of addressing these challenges through comprehensive research, testing and collaboration with industry stakeholders and regulators.
The transportation of CO2 differs significantly from other gases, such as natural gas, due to its unique physical and chemical properties. CO2 is most efficiently transported in its dense-phase form, a state achieved under high pressure and relatively moderate temperatures.
However, dense-phase CO2 presents thermodynamic and flow properties that can impact the integrity of pipeline materials, making it more prone to experiencing challenges such as corrosion and stress cracking. When combined with the presence of impurities like water, hydrogen sulfide (H2S) and nitrogen oxides (NOₓ), there is significant increase in the risk to pipeline integrity.
Water content, even in trace amounts, is a particular problem in CO2 streams. It reacts with CO2 to form carbonic acid, which significantly accelerates corrosion, especially in high-pressure environments typical of dense-phase transport. Impurities such as H2S and sulfur dioxide (SO2) also exacerbate corrosion by forming other aggressive acidic compounds.
This requires tight controls on impurity levels and robust pipeline material selection. Laboratory studies have provided critical insights into these challenges. For example, testing on a 20-year-old offshore natural gas pipeline revealed how existing materials and coatings perform under dense-phase CO2 conditions.
Such studies have identified specific coatings and corrosion-resistant materials that can withstand the combination of high pressure, high acidity and fluctuating temperature common in CO2 transport.
Another technical challenge lies in the effect of impurities on the thermodynamic behavior of CO2. Unlike natural gas, CO2 undergoes significant changes in phase behavior, depending on the pressure and temperature, and these properties can be further altered by impurities, such as methane (CH₄), nitrogen (N₂) and SO₂.
For instance, the presence of impurities shifts CO2’s critical pressure and temperature, increasing the likelihood of two-phase flow (the simultaneous existence of gas and liquid phases).
Two-phase flow can lead to increased operational costs, equipment wear and safety risks, due to the instability it introduces to pipeline flow dynamics. To address this, validated thermo-dynamics models predict the behavior of CO2 mixtures under various conditions.
These models guide decisions on operational parameters, such as the optimal temperature and pressure ranges, and they inform pipeline design to mitigate the risks associated with phase changes.
Repurposing existing pipelines for CO2 transport can be an attractive option due to its cost-effectiveness and sustainability. However, such pipelines — originally designed for natural gas — must undergo rigorous evaluation to ensure their suitability for dense-phase CO2.
Pipeline materials, including welds, coatings and seals, need to be assessed to understand how they respond to the unique properties of CO2. Older infrastructure often exhibits material degradation, which may be further exacerbated when exposed to CO2 streams containing impurities.
Detailed lifecycle assessments and techno-economic analyses are used to evaluate the feasibility of retrofitting natural gas pipelines. These assessments consider factors such as environmental impact, operational safety and the cost of retrofitting versus building new infrastructure.
Moreover, retrofitting pipelines for CO2 transport often requires significant material upgrades. For instance, the use of corrosion-resistant alloys or polymer-based linings can mitigate risks posed by impurities. Offshore pipelines face additional challenges, such as marine corrosion, fluctuating pressures and the need for continuous monitoring.
To address these, the industry has collaborated to develop frameworks for assessing and improving the integrity of existing pipelines. These frameworks include experimental tests that simulate the conditions pipelines would face during CO2 transport, providing operators with data to make informed decisions on retrofitting.
Pulse of CO2
A critical aspect of CO2 transport infrastructure is ensuring safety through advanced leak detection and emergency response systems. Unlike natural gas, which is lighter than air and disperses upward, CO2 is heavier than air and can accumulate in low-lying areas, posing significant risks of asphyxiation to humans and animals.
Detecting leaks in CO2 pipelines is therefore paramount. Modern leak detection systems incorporate real-time sensors to monitor changes in pressure, temperature and flow within the pipeline.
In addition to real-time monitoring, computational models have been developed to simulate CO2 dispersion in the event of a leak. These models account for variables such as terrain, pipeline pressure and weather conditions, enabling operators to predict the extent and direction of a potential leak.
This information is vital for emergency response planning and minimizing the environmental and safety impacts of leaks. Field tests have validated these models, ensuring their accuracy in real-world scenarios. Coupled with robust public communication strategies, these technologies foster trust and understanding of CO2 transport systems among communities.
Managing impurities within CO2 streams is another technical focus area. Research has shown that impurities such as CH4, N2 and SO2 not only impact pipeline materials but also increase operational challenges.
For instance, free water in the CO2 stream can lead to hydrate formation, which causes blockages and operational downtime. Studies have demonstrated that adhering to strict impurity limits is essential for maintaining pipeline integrity and operational efficiency. Collaborative efforts, such as workshops and technical gap analyses, have further been instrumental in identifying impurity thresholds and informing industry standards.
Workshops organized by bodies such as the U.S. Department of Energy have highlighted research gaps and set priorities for future research, development and demonstration (RD&D). These initiatives include technical analyses, regulatory input, and the development of centralized data repositories.
These repositories enable industry stakeholders to share knowledge, refine modelling tools, and accelerate the deployment of CO2 transport systems. By fostering collaboration, the industry can ensure that infrastructure development aligns with broader decarbonization strategies.
Conclusion
The path to robust CO2 transport infrastructure is not without its challenges, but ongoing research and innovation are paving the way for solutions that prioritize safety, efficiency and sustainability.
The work of organizations like RINA is instrumental in addressing the technical barriers to CO2 transport, from material advancements and impurity management to enhanced monitoring systems. As the energy transition gains momentum, these efforts will play a pivotal role in enabling regions worldwide to achieve net-zero emissions, while ensuring public safety and environmental health.
RINA engineering consultancy specializes in the challenges of CO2 pipeline integrity, infrastructure repurposing and leak detection, as well as the increasingly collaborative work being carried out worldwide to address these issues.
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