Carbon capture and storage (CCS) is accepted by the international scientific community as the most viable short-term measure to limit CO2 emission in the atmosphere, avoiding reversible changes on the planet's climate. While CO2 capture and storage are of primary importance to allow a reduction of the carbon emission, viable and economically feasible CO2 transport solutions must be ensured to enable the CCS deployment. In particular, avoidance of leaks or failures within the entire transport chain is key to ensure that the effort of CO2 capture is not lost due to leakage during transportation.
The transport of dense or liquid CO2 represents a challenge for many of the materials which come in contact with it. Particularly, polymeric materials may undergo temporary or permanent changes in structure when exposed to CO2 and this can affect their performance. However, there are still significant knowledge gaps in how polymer materials are affected by dense phase CO2. The CO2 EPOC project focussed on closing these knowledge gaps by investigating the compatibility between polymeric materials and CO2 streams.
By considering the types of polymer materials used in existing oil and gas transport infrastructure, together with a review of polymer materials not used for oil and gas transport but which could be relevant for CO2 transport applications, a range of polymers (thermoplastic polymers and elastomers) were selected analysis in CO2 EPOC. These were characterised in lab conditions matching the conditions that would be experienced by the polymers in CO2 transport applications. Since some polymers can absorb significant amounts of CO2, causing swelling which results in changes in mechanical and barrier properties and the size and shape of polymer components, the effect of CO2 on these polymers was investigated. Transient effects which may occur in the polymers when they are exposed to CO2 transport application, such as volumetric swelling, CO2-induced plasticization (softening) and permeability were measured. Permanent effects which may occur in the polymers, such as permanent mass loss, changes in mechanical properties and crack damage were measured following exposure. Selected data from these tests were used to build fundamental models of how these polymers could perform in other temperature and pressure conditions, which may be relevant for different CO2 transport conditions.
Two PhD candidates have completed their doctorates in the CO2 EPOC project. 1 PhD thesis from the University of Oslo, focussed on the compatibility of CO2 with polymer materials based on experimental work. 1 PhD thesis from the University of Bologna, Italy, focussed on developing predictive models to describe the interaction of CO2 with polymer materials. In addition, 2 masters students from University of Bologna have completed their studies performing experimental work in the project.
Links to published results from the CO2 EPOC project, together with project newsletters are shared on the CO2 EPOC project website. The website includes links to recent publications and to excerpts two open webinars organised in CO2 EPOC. The project website is located here: https://www.sintef.no/en/projects/2020/co2-epoc/
Outcomes: The project has generated knowledge on how a range of polymers are affected by CO2. The use of polymers is necessary in gas transport, for example as seals to prevent leakage between metal components. The CO2 value chain is full of knowledge gaps that hinder the selection of polymers for these applications. The industrial partners need this knowledge in their practice of risk-assessing the re-use of existing oil and gas infrastructure for CO2 transport, or when designing new equipment. This knowledge is made public via series of publications as described in the dissemination plan. The project has also trained masters and doctoral students with advanced competence in this field.
The data generated in the CO2 EPOC project is of primary interest for engineers and technicians working within the CO2 transport field. The results enable a more educated selection of polymeric materials within the CO2 transport chain, which may also include the re-use of the current oil & gas infrastructure.
The fundamental models developed in the project may also be of interest outside the CCS (carbon capture and storage) field. The fundamental nature of the model allow it to be extended also to other technical areas, involving exposure of polymeric materials to gases under harsh conditions (high/low temperature, high pressure, presence of contaminants, continuous operations). Transport of natural gas or hydrogen can be two examples of other fields where the model results can be of interest.
Impacts: Safe, reliable and cost effective transport infrastructure is key for the full-scale deployment of CCS. Any losses of CO2 due to polymer seal leakage during gas transportation undermines the efforts used in capture. Therefore, results from the project help to enable safe and reliable (long-life and low leakage) operations, which will accelerate the implementation of CCS into society.
Sustainable and efficient deployment of carbon capture and storage (CCS) requires suitable and reliable solutions at all levels of the value chain. Demonstrations of capture and storage technologies developed in the last decades have already realised a TRL able to support a quick CCS deployment, but knowledge gaps still exist regarding which polymer materials may be safely and effectively used in the CO2 transport infrastructure (e.g., elastomeric seals, gaskets, pipe liners etc as leakage seals and protective barriers). Transport of supercritical CO2 by pipeline or transport of cryo-compressed CO2 by ship create very different, but both highly demanding environments. These environments have different effects on polymeric materials, and can lead to transient and permanent changes in the materials (such as stiffening, cracking, seal leakage and premature part failure), resulting in re-emission of the CO2 during transport.
The CO2-EPOC project aims to create knowledge on the compatibility between polymeric materials and CO2 streams to aid proper selection of polymer-based materials across the CO2 transport infrastructure (pipelines and ships) in order to avoid leakage and failure. Any losses during transport of the CO2 due to leakage greatly undermines the efforts spent on CO2 capture. The goal will be pursued by implementing a multilevel approach, spanning from experimental characterization of how representative polymers react to CO2 (including contaminants), to fundamental modelling to predict this behaviour in other application scenarios. Synergy between the levels will give improved understanding of the effect of CO2 on polymer materials, providing much needed knowledge for the design of efficient and reliable CO2 transport systems.
