Adsorption - Introduction to Carbon Capture and Sequestration - page 239

Sweep gas

Adsorption Regeneration heat

N 2

Adsorption Regeneration Sweep gas

N 2

lower T higher T

Normal P Lower P

Flue gas

cool

Flue gas CO 2

CO 2

CO 2

CO 2

40º C 40º C

T final

T final

p CO 2

p CO 2

0.14 atm 1.0 atm 0.07 atm 0.14 atm

CO 2 adsorption CO 2 desorption CO 2 desorption CO 2 adsorption

(a) (b)

Figure 6.2.3. Temperature and pressure swing adsorption
(a) In temperature swing adsorption , we make use of differences in adsorption at dif-
ferent temperatures. The adsorption step is done at a lower temperature (1 atm,
40ºC, 14% CO 2 ) compared to the desorption step. The isotherms give the equilib-
rium concentrations at adsorption and desorption conditions. The working capacity
is the amount of CO 2 that is removed in one cycle.
(b) In pressure swing adsorption , we make use of differences in adsorption at different
pressures. The adsorption step is done at a higher pressure (1 atm, 40ºC, 14% CO 2 )
compared to the desorption step. The isotherms give the equilibrium concentrations
at adsorption and desorption conditions. The working capacity is the amount of CO 2
that is removed in one cycle.

Question 6.2.1 Working capacity

Do the following changes of the operating conditions decrease or increase
the working capacity?
1. Decrease the fl ue gas temperature.
2. Increase the fl ue gas pressure.
3. Decrease the pressure at desorption. (How would we do this in
practice?)