A question that is often asked is 'What to do with the CO2 after it has been captured?' Small quantities of essentially pure CO2 can be used for industrial applications including carbonated beverages but, at the scale required for significantly reducing atmospheric CO2 emissions, the two main options for CO2 capture are (a) using CO2 for Enhanced Oil Recovery (EOR) or (b) permanent sequestration. For these applications, it is necessary to compress CO2 to about 150 bar. Multiple compressor stages with inter-stage cooling are necessary to reach this minimum miscible pressure for EOR.
Typical Schematic of CO2 Compression Process
CO2 is first compressed through about three stages of compression, intercooling, and liquid knockout. It then goes through a dehydration step. The CO2 dehydration step of the carbon sequestration process is critical because the moisture content will affect the material of the CO2 pipeline as well as operational issues with hydrate formation.
The CO2 then enters a fourth stage where it is compressed to supercritical conditions. It is then cooled in an aftercooler but no knockout is required since it is dry and in a dense phase.
The supercritical CO2 then enters a multistage CO2 pump/compressor and is discharged at the appropriate delivery pressure.
KBR delivered the CO2 Compression, CO2 Dehydration, and the CO2 Pipeline for the In Salah project in Algeria.