Compression and cooling

DESCRIPTION

CO₂ compression involves the exclusive use of compressors and coolers to deliver CO₂ in either the gas phase or supercritical phase at the inlet of the pipeline.¹ It is done in multiple stages of cooling and compression. The CO₂ can be compressed to the desired pressure for gas-phase transport using either single-stage or multi-stage compression systems, depending on efficiency and pressure requirements. For dense-phase transport, the process involves three compression stages, during which CO₂ is compressed to 80 bar and cooled to 30 °C. The resulting supercritical CO₂ is then pumped to the final pressure of 110 bar, as shown in the figure.² When the temperature drops below the critical temperature of CO₂, the transported supercritical CO₂ would transition to a dense phase during pipeline transport, especially in offshore sequestration. The main advantage is the use of easily accessible cooling water rather than a refrigeration cycle required in the liquefaction process.

REMOVED COMPONENTS

• Water is removed as condensate after every compression and subsequent cooling stage.

FUNCTION IN CCU VALUE CHAIN

• The compression approach allows CO₂ transportation at ambient temperatures.²
• Gaseous CO₂ may be compressed up to 80 bar and then pumped to pressures up to 150 bar after cooling to obtain a supercritical liquid state.²

LIMITATIONS

• CO₂ compressors are responsible for a large portion of the capital and operating cost of any CCS system.³
• They require expensive stainless steel construction to accommodate CO₂ in the presence of water vapor.³

ENERGY

Electricity is consumed by the compressors and the dense CO₂ pump.

CONSUMABLES

Cooling water is used to cool the CO₂ stream after each compression stage. It is generally recycled and not consumed.

COSTS

The cost of CO₂ compression can vary significantly depending upon the feed and output pressures, which require different numbers of compression stages, often contributing to a significant portion of the overall cost of carbon capture and storage (CCS) systems. The cost for compression up to 110 bar (supercritical) ranges from €13 – €15 per tonne CO₂, depending on the CO₂ concentration of captured CO₂ (93 vol.% vs 97 vol.%) and annual capture capacity (4 vs 1 MtCO₂/yr).⁵ Other sources report the cost to be in the range of €96 - €12* per tonne CO₂.

*CAPTIN project: 1.67 MtCO₂/yr

TECHNOLOGY PROVIDERS

• CO₂ compressors by Atlas Copco, Sweden.
• CO₂ compression systems by Linde, Ireland.
• CO₂ compression systems by Baker Hughes, USA.
• CO₂ compressors by MAN Energy Solutions, Germany.
• CO₂ compressors by Siemens-Energy, Germany.

ALTERNATIVE TECHNOLOGIES

Liquefaction: CO₂ is first compressed to lower pressures (7-15 bar) and then liquefied for transportation. It requires a refrigeration system and is more suitable for ship transport.

CONTACT INFO

Mohammed Khan (mohammednazeer.khan@vito.be)

Miet Van Dael (miet.vandael@vito.be)

ACKNOWLEDGEMENT

This infosheet was prepared as part of the MAP-IT CCU project funded by VLAIO (grant no. HBC.2023.0544).

REFERENCES

1.    Dlamini G, Remiezowicz E, Ness K, et al. Carbon dioxide conditioning pathways for pipeline transport. In: International Conference on Greenhouse Gas Control Technologies, GHGT-16. ; 2022:7.

2.    Anantharaman R, Bolland O, Booth N, et al. DECARBit: European Best Practice Guidelines for Assessment of CO2 Capture Technologies. Norwegian University of Science and Technology; 2011. Accessed November 3, 2018. https://www.sintef.no/globalassets/project/decarbit/d-1-4-3_euro_bp_guid_for_ass_co2_cap_tech_280211.pdf

3.    Powermag. Capturing CO2: Gas Compression vs. Liquefaction. June 1, 2009. Accessed October 29, 2024. https://www.powermag.com/capturing-co2-gas-compression-vs-liquefaction/

4.    Bilsbak V. Conditioning of CO2 Coming from a CO2 Capture Process for Transport and Storage Purposes. Norwegian University of Science and Technology; 2009. http://www.diva-portal.org/smash/get/diva2:348870/FULLTEXT01.pdf

5.    Abbas Z, Mezher T, Abu-Zahra MRM. CO2 purification. Part II: Techno-economic evaluation of oxygen and water deep removal processes. Int J Greenh Gas Control. 2013;16:335-341.

6.    ZEP. The cost of subsurface storage of CO2. February 3, 2020. Accessed October 29, 2024. https://zeroemissionsplatform.eu/co2-storage-cost/