Introduction to Carbon Capture - Introduction to Carbon Capture and Sequestration - page 155

6.5%

6.0%

11% CO 2
13% CO 2
15% CO 2

5.5%

5.0%

4.5%

4.0%

3.5%

3.0%

80% 84% 88% 92% 96% 100%

Percent of CO 2 captured

Figure 4.2.3 Energy requirement as a fraction of the energy produced
The energy penalty as a function of the percentage of CO 2 captured from the fl ue gas.
In this calculation the separation is carried out at 40ºC using different fl ue gas concen-
trations. Figure based on the calculations given in [4.5].

almost
pure N 2

mixture
N 2 /CO 2

almost
pure CO 2

compressed
pure CO 2

Figure 4.2.4 Separation and compression
Separation followed by compression of the capture stream.

Compression

Once the CO 2 is separated, the next step is to compress it to a pressure
at which it can be stored in geological formations (see Figure 4.2.4 ). The
pressure needs to be suffi ciently high to ensure that CO 2 is a supercritical
fl uid, so we use a reference pressure of 150 bar (148 atm). The energy