Absorption - Introduction to Carbon Capture and Sequestration - page 208

exhaust capture

steam Q in

Q out

flue gas

Figure 5.6.1 Simple absorption process
In an absorption process a solvent is cycled between the absorber, where it captures
the CO 2 , and in the stripper where the CO 2 is released through heating by steam from
a power plant.

heat , which is the heat required to increase the temperature of the sol-
vent to the desorption conditions, and the heat of desorption , which is
the negative of the heat of absorption . It is useful to normalize the heat
per kg CO 2 , q tot :

QQ +

sen des

q = ,

tot

∆ σ

CO

2

where ∆σ CO 2 is the amount of CO 2 removed in an absorption/desorption

cycle, which is often referred to as the working capacity of the material.
The sensible heat is related to the heat capacity ( C p ) of the solvent:

Q sen = C p m abs ( T des − T abs ),

where m abs is the total amount of solvent and T des , T abs are the tempera-
ture of the solvent in the stripper and absorber, respectively. The desorp-
tion heat is the negative of the heat of absorption:

Q des = ∆ h CO 2 ∆σ CO 2 + ∆ h N 2 ∆σ N 2 ,

where h N 2 are the heats of desorption of CO 2 and N 2 , respec-

tively. In most calculations, we will assume that the absorption of N 2 is

∆ h CO 2 and ∆