Adsorption - Introduction to Carbon Capture and Sequestration - page 245

Figure 6.3.2 Adsorption bed and breakthrough times
The fl ue gas enters the left of the column. The blue lines give the CO 2 concentration in
the fl ue gas as a function of its position in the bed at different time increments after the
bed has been regenerated. As soon as the CO 2 front reaches the right side of the bed
we reach the breakthrough, and the material needs to be regenerated again.

1

0

t b

t

1

0

t b

t

Figure 6.3.3 Experimental breakthrough curves
The concentration of an adsorbed species (like CO 2 ) at the outlet is divided by the concentra-
tion at the inlet c 0 as a function of time. Initially the concentration at the outlet is close to zero
because all molecules are being adsorbed in the bed. After some time, the bed is becoming
saturated and the concentration will increase until it equals the concentration coming in. If
we have ideal adsorption, this profi le is a step function. Non-ideal fl ow and diffusion limita-
tions cause deviations from the ideal behavior. This non-ideal behavior decreases the effi -
ciency of our bed, as we get too high a concentration of CO 2 earlier.