Cryogenic carbon capture technologies

Cryogenic carbon capture is in the early stages of development, however, several projects have achieved a Technology Readiness Level (TRL) of 6, for applications such as blue hydrogen production. 

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




[1] IEA (2021), About CCUS, IEA, Paris 

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

[3] Cryocap™ Carbon Capture Technology. 

[4] Cryocap™ H2 – Cryogenic CO2 Separation. 

[5] Geler le CO2 pour le capter : la technologie de la start-up Revcoo fait ses preuves.