Cryogenic distillation: a promising technology for carbon capture

Cryogenic distillation is subject to intense R&D works for CO2 capture in CCS facilities. A plant using this technology is under construction in China.

Carbon Capture and Storage (CCS) encompasses an integrated suite of technologies that can prevent large quantities of CO2 from being released in the atmosphere from the use of fossil fuels. The CCS chain consists of three parts: capturing the carbon dioxide, transporting it to a storage site via ship or pipeline, and either using it as a resource to create valuable products or services or storing it deep underground in geological formations.

CCS technologies – which can be applied in the industrial sector and for power generation – could play an important role in meeting energy and climate goals. In the IEA Sustainable Development Scenario, CCS accounts for 7% of the cumulative emission reductions needed globally by 2040. This implies a rapid scale-up of CCS deployment, from around 30 million tonnes (Mt) of CO2 currently captured each year to 2 300 Mt per year by 2040.[1]

As of 2019, there are 17 operating CCS installations in the world – including about 70% in North America – capturing 31.5Mt of CO2 per year, of which 3.7 Mt are stored geologically. Most of them being industrial and not power plants.[2]

Its uses cover a variety of industrial applications, outstanding abatement of CO2 from process or exhaust gases and in natural gas processing. In the former, depending on the technology, CO2 is separated from H2 (pre-combustion), N2 (post-combustion) and H2O (oxy-combustion, which burns hydrocarbons with pure O2), while in natural gas processing, CO2 is separated from CH4 and light hydrocarbons.[3]

CO2capture technologies are available in the market but are costly in general, and contribute to around 70–80% of the total cost of a full CCS system.[4]

The main CO2 separation technologies that can be applied to isolate the CO2 from the flue/fuel gas stream prior to transportation are absorption (the most mature process), adsorption, chemical looping, membrane separation, hydrate-based separation and cryogenic distillation.[4]

The cryogenic distillation process is the following: flue gas containing CO2 is cooled to desublimation temperature (-100 to -135°C) and then solidified. CO2 is separated from other light gases and compressed to a high pressure of 100 to200 times the atmospheric pressure. The amount of CO2 recovered can reach 90–95% of the flue gas. Since the distillation is conducted at extremely low temperature and high pressure, it is an energy intensive process estimated to be 600–660 kWh per tonne of CO2 recovered in liquid form. Several patented processes have been developed and research has mainly focused on cost optimization. CO2 is obtained as liquid with benefits in CO2 transport (no compressors needed, pumps used instead). It is appropriate for high CO2 content.[3] [4]. Cryogenic carbon capture technology is a relatively young technology but is being actively developed. Furthermore, cryogenic distillation has been adopted for many years in industry for CO2 recovery.[4]

There are actually very few large-scale CCS projects in operation using cryogenic distillation.[3] However, it should be noted that a facility using this technology is under construction at a fertiliser plant in Zibo City, Shangdong Province, China. Upon completion it is expected to capture 400 Mt of CO2 per year.[5]

[1] IEA, Carbon capture, utilization and storage. Available following this link.

[2] Global CCS Institute, Facilities Database. Available following this link

[3] de Queiroz Fernandes Araújo O. , Luiz de Mederos J. Carbon capture and storage technologies: present scenario and drivers of innovation. Current Opinion in Chemical Engineering, Aug. 2017. Available following this link.

[4] Leung D. Y. C. et al. An overview of current status of carbon dioxide capture and storage technologies. Renewable and Sustainable Energy Reviews , November 2014. Available following this link.  

[5] Asia Times, China aims to capture greenhouse gases. Available following this link