Cryogenic carbon capture technologies

According to the IEA (International Energy Agency), carbon capture, utilisation and storage (CCUS) refers to a suite of technologies that can play a key role in meeting global energy and climate goals. CCUS involves the capture of CO₂ from industrial facilities that use either fossil fuels or biomass for fuel. The CO₂ can also be captured directly from the atmosphere. ^[1] 

 

Chemical absorption using amine-based solvents is the most mature carbon capture technology. ^{[1, 2]} However, the large volumes of solvent that are used require significant thermal energy for regeneration. ^[2] The physical separation of CO₂ is another mature technology currently commercialised in natural gas processing and ethanol, methanol and hydrogen production. Among other processes, physical separation of CO₂ can be achieved using low temperature technologies. Cryogenic carbon capture relies on phase change, thus separating the CO₂ from the gas in the form of a liquid or solid. ^[2] 

 

Cryogenic carbon capture for low-carbon hydrogen production: Cryocap technology by Air Liquide 

 
For low-carbon hydrogen production using fossil fuels (called “blue hydrogen”), cryogenic carbon capture technology is essential to reduce CO₂ emissions. High-purity hydrogen of 90–98% can be attained in large-scale hydrogen production plants through cryogenic distillation. The principle used here is based on the partial condensation of the impurities in the off-gas generated during hydrogen production at low temperatures. ^[2] 

 

Air Liquide, an IIR member, has developed a solution for CO₂ capture called Cryocap.  Cryocap™ can been adapted to a variety of Air Liquide’s technologies such as the capture of CO₂ from hydrogen production (Cryocap™ H₂) or from other industries (such as refining, steel or cement) concentrated flue gases (Cryocap™ FG) or from Oxy Combustion power stations (Cryocap™ Oxy). ^[3] 

Used to capture CO₂ in hydrogen production plants, Cryocap™ H₂ involves compressing and drying off-gas from the production process and sending it to a cryogenic unit. Partial condensation and distillation techniques are then applied to separate the CO₂ from other components. As a result, a pure and pressurized CO₂ flow is produced by the cold box. Non-condensed gases are recycled through a membrane system to recover H₂ and further CO₂, and any residual gas is sent to burners in the reformer furnace. Finally, the resulting CO₂ product is compressed to supercritical pressure or liquefied, and stored in liquid storage. ^[4] 

The installation in Port-Jérôme, France, represents the first industrial deployment of the Cryocap™ H₂ technology and has been operated by Air Liquide since 2015. ^[3] There was a reported increase in hydrogen recovery, with more than 97% of CO₂ from the syngas being captured. 

 

Improving the energy efficiency of cryogenic carbon capture

 

According to a review article, current carbon capture technologies have reported varying costs depending on the application, e.g., USD 40–60/tonne CO₂ for the power sector and USD 200/tonne CO₂ for the cement sector. The authors reported that the energy consumption varied between 2.4 to 5.2 GJ/tCO₂ for cryogenic technologies, and 2.3 to 9.2 GJ/tCO₂ for absorption technologies. ^[2] 

 

Revcoo, a French start-up, has demonstrated a CO₂ capture technology that could be more energy-efficient than currently available solutions. ^[5] Their process includes extracting nitrogen from the flue gas, liquefying it at -196°C, then using the liquefied nitrogen to freeze only part of the CO₂ in a desublimator. The cold energy from 30% of the CO₂ at a solid state is used to liquify the rest of the CO₂. In a nutshell, the energy released by the CO₂ as it passes from the solid and liquid phases to the gas phase is fed back into the circuit. 

The Revcoo engineers estimated that for a gas stream with a 20% CO₂ concentration, their process requires 350 kWh (about 1.26 GJ) of electricity to capture one tonne of CO₂. This rises to 550-600 kWh (about 2 GJ) for a 10% CO₂ concentration.  

 

 

For more information on cryogenic carbon capture technologies, a review article was published in the Journal of Carbon Research. 

 

 

Sources

[1] IEA (2021), About CCUS, IEA, Paris https://www.iea.org/reports/about-ccus 

[2] Font-Palma, C., Cann, D., & Udemu, C. (2021). Review of cryogenic carbon capture innovations and their potential applications. C, 7(3), 58. https://doi.org/10.3390/c7030058 

[3] Cryocap™ Carbon Capture Technology. https://www.engineering-airliquide.com/fr/cryocaptm-carbon-capture-technology-way-reduce-carbon-footprint 

[4] Cryocap™ H2 – Cryogenic CO2 Separation. https://www.engineering-airliquide.com/cryocap-h2-cryogenic-co2-separation 

[5] Geler le CO2 pour le capter : la technologie de la start-up Revcoo fait ses preuves. https://www.usinenouvelle.com/article/geler-le-co2-pour-le-capter-la-technologie-de-la-start-up-revcoo-fait-ses-preuves.N1804907