Adsorption - Introduction to Carbon Capture and Sequestration - page 237

precisely what we are being asked to do with our adsorbent in the regen-
eration step. One solution is to use a fl uidized bed, based on the idea that
by fl owing a gas through a powder, it will behave like a liquid. Such a
fl uidized bed allows us to bring the fl ow of solid particles from the bottom
of the column to the top. Once the particles reach the top, they can fl ow
to the bottom through gravity, adsorbing the CO 2 gas that fl ows upwards
on their way down. When the particles get to the bottom, they are regen-
erated and ready to enter the adsorption section. Figure 6.2.2 shows a
possible implementation of this process.
An alternative to moving the solid is to continuously change the posi-
tion in which we introduce the fl ue gas and the purge gas. In this way we
mimic the movement of the solvent using a well-designed system of

Clean gas

Adsorption
section

Tray

Flue
gas

CO 2

Gas lift line

Steam for
heating

Preheating tube
D esorption
tube

desorbent

desorbent

Desorption
section

extract

N 2

feed

Steam for
desorption rotary

valve

rafinate

Recovered
solvent
Condensate

adsorption
column

flue gas

Adsorbent
carrier gas

(a) (b)

Figure 6.2.2 Fluidized and simulated moving bed
(a) In the top part of the fl uidized bed the fl ue gas is injected and the adsorption process
takes place, and in the bottom part the solid adsorbent is regenerated. In this bed,
there is a continuous fl ow of solid material; the central tube takes the regenerated
materials from the bottom using a carrier gas and they get injected at the top.
(b) In a simulated moving bed , the often problematic movement of the solid material is
avoided by a system of intelligent valves. The valves are rotating in such a way that dif-
ferent parts of the columns are adsorbing while other parts are being regenerated.