a gas. Converting CO₂ to a dense phase enables the use of smaller pipelines and increases the amount of CO₂ that can be stored in reservoirs. In downstream applications, lube oil can become contam - inated through compressor wear, requiring filtration. It can also be carried over after the compressors, which can cause the CO₂ to become off-specification. Similarly, dehydration processes such as adsorbent-based dryers or glycol loops can require filtration and liquid/gas coalescence to prevent fouling of dryers and absorption loops, and to prevent carry- over of fines or glycol contaminants. After compression and dehydration stages, undesired contaminants such as water, lube oil, oxygen, and H₂S can be present in the CO₂, which pose a threat to the integrity of the pipelines. Hydrogen sulphide and oxygen are corro - sive, damaging the pipelines and, in the worst case, causing cracks. Trace water can react with CO₂, forming corrosive byproducts, and can also form hydrates, which produce pipeline blockages. As pipelines deteriorate, solid corrosion products and pipe scale formed through these reactions can be carried down - stream, plugging critical equipment needed for carbon cap - ture storage, such as control valves, metering stations, and high-pressure injection pumps. This increases maintenance costs and can require equipment replacement or unsched - uled downtime. Solid contaminants can also plug perme - able storage reservoir pore structures, requiring increased energy for CO₂ injection and even limiting the amount of available and accessible reservoir storage capacity. In selecting filters and separators for dense phase CO₂ applications, substantial care must be taken on which mate - rials are used, how filter sizing is performed, and what the filtration rating is. To fully protect reservoirs, the filter rating must be selected based on the reservoir permeability and approximate pore diameter. Regarding material choice, safe operation favours corrosion-resistant metallic materials or CO₂-stable plastics. Plastics must be carefully selected, as some materials may swell under contact with supercritical CO₂. Additionally, some polymers can mechanically fail by explosive decompression if there is a rapid pressure drop during upset conditions or routine maintenance after CO₂ has adsorbed and diffused into the polymer due to high- pressure operation. Conclusions Filtration and separation applications in solvent-based absorptive carbon capture are well-known from decades of gas processing technology with amine solvents. However, there are emerging requirements specific to carbon capture, such as low available pressure drops in pretreatment and high pressures in downstream CO₂ transport and storage. These requirements mean that new filters and separators tailored to the applications outlined in this article, as well as expert knowledge in material and product selection, are needed. By choosing the right purification product with the right material compatible with the application, both capital and operating expenses can be minimised by protecting critical equipment, meeting environmental specifications on contaminant levels, and keeping process efficiency high.
Gas out
Gas in
Water in
Figure 6 Pall high-efficiency liquid-gas coalescer
Acknowledgements Special thanks to Olivier Trifilieff, Ali Arshad, Joe Youberg, and Keith Webb for their contributions and review of this article. References 1 IEA, Transforming Industry through CCUS, 2019, www.iea.org/ reports/transforming-industry-through-ccus. 2 Moser et al, Solid particles as nuclei for aerosol formation and cause of emissions – Results from the post-combustion capture pilot plant at Niederaussem, 13th International Conference on Greenhouse Gas Control Technologies, Lausanne, Switzerland, 2016. 3 Raymond A, Levesque F, Lakhani H, Separations technologies to improve amine system reliability: A case study. Pall Corporation Scientific & Technical Report FCASRCSENa , 2008. 4 Mazari et al, Formation and Elimination of nitrosamines and nitramines in freshwaters involved in post-combustion carbon capture process. Journal of Environmental Chemical Engineering , Vol 7, Issue 3, 2019. Lara Heberle is the Global Technology Development Manager for Carbon Capture, Utilization, and Storage at Pall Corporation. She holds a BSc in engineering physics and mechanical engineering from the University of British Columbia, and a Doctorate in mechanical engineering, with a focus on fluid dynamics and a minor in thermal sciences from Cornell University. Email: lara_heberle@pall.com Julien Plumail is the Global Vertical Marketing Manager for Carbon Capture, Utilization, and Storage at Pall Corporation. He holds an MSc in engineering from the French Petroleum Institute, and an MBA from IESEG. Email: julien_plumail@ pall.com
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