TECH TALK
Navigating the Complexities of Carbon Capture , Utilisation , and Storage ( CCUS )
As the world grapples with the pressing need to reduce carbon emissions and combat climate change , Carbon Capture , Utilisation , and Storage ( CCUS ) has emerged as a crucial technology . CCUS offers a pathway to mitigate the effects of carbon dioxide ( CO 2
) emissions by capturing the gas at its source , utilizing it in various industrial processes , or storing it deep underground . However , implementing CCUS on a large scale presents a myriad of challenges , particularly in the realm of materials science and engineering . Among these challenges , the development of reliable sealing solutions for CO 2 handling equipment , such as valves , is paramount .
By Patrick Stephen , Product Manager , High Performance Elastomers , and Andrew Douglas , Materials Engineering Group Manager , James Walker
Companies with experience and knowledge in the oil and gas sector now provide materials and expertise for CO 2 sealing applications and facing off against emissions . This article explores the challenges faced in CCUS , particularly related to valves , and highlights James Walker ’ s contributions to overcoming these obstacles .
The Growing Importance of CCUS
Carbon dioxide is ubiquitous in our daily lives , from the air we exhale to the fizz in our carbonated drinks . However , its accumulation in the atmosphere is a significant concern due to its central role in climate change . CCUS technologies aim to address this issue by capturing CO 2 from industrial processes or directly from the air and utilizing it in various ways , or securely storing it to prevent its release into the atmosphere .
The deployment of CCUS technologies is being driven by increasingly stringent climate goals and the need to decarbonize industries such as power generation , cement production , and chemical manufacturing . However , the scale and complexity of these operations introduce new challenges , particularly in the handling , transport , and storage of CO 2
.
Challenges in CO 2
Handling and
Storage
One of the most critical aspects of CCUS is ensuring the safe and efficient handling of
CO 2
, especially when it transitions between its different phases — gaseous , liquid , and supercritical . At relatively low temperatures and pressures ( around 31 ° C and 74 bar [ 1070 PSI ]), CO 2 enters a supercritical phase where it exhibits the properties of both a gas and a liquid . This phase change can have significant implications for the materials used in CCUS equipment , particularly seals .
Carrying out extensive RGD testing at James Walker .
Sealing Challenges in Valves for CO 2
Applications
Valves play a crucial role in controlling the flow of CO 2 in CCUS systems , making their reliability and performance vital to the overall success of the technology . However , sealing CO 2
, especially in its supercritical state , presents several unique challenges :
Rapid Gas Decompression ( RGD ): RGD is a well-known phenomenon in the oil and gas industry , where the rapid depressurization of a gas-saturated elastomer can cause catastrophic seal failure . In CCUS applications , the transition of supercritical
CO 2
( scCO 2
) back to a gaseous state , and the resulting volume increase , can trigger severe RGD damage , making it a significant concern for valve seals .
Swell and permeation : scCO 2 can cause significant swelling in certain elastomeric materials used in seals . The degree of swelling can vary even within elastomers of the same type , making material selection critical .
Leaching : the solvent properties of scCO 2 can result in the leaching of fillers and other components from elastomer compounds . This process can lead to a reduction in the seal ’ s mass and volume , adversely affecting its sealing performance and longevity .
Glass transition temperature ( Tg ) suppression : interestingly , scCO 2 can lower the glass transition temperature of some elastomers , potentially improving their low temperature sealing performance by a few degrees . This effect is inconsistent across all elastomers and must be carefully considered during material selection .
Despite these challenges and the known effects of CO 2 on elastomer seals , the industry lacks standardized testing protocols for validating these seals in CO 2 applications . Consequently , we must rely on ex-
28 Valve World Americas | October 2024 • www . valve-world-americas . net