Adsorption - Introduction to Carbon Capture and Sequestration - page 250

Section 4
Adsorption costs
As in absorption, the costs of adsorption processes involve two main
components. The fi rst one is the capital cost of the equipment. As we
have seen in the previous section, the size of the equipment is set by
the breakthrough curves. The cost of the adsorbent also factors into the
capital cost. This is more diffi cult to estimate, as adsorption processes
for carbon capture are still in a very early stage of development. In par-
ticular, if we use a novel material it is very diffi cult to reliably estimate
its future cost in a large-scale operation. Many of the new materials are
currently synthesized in laboratories only on a very small scale. One
really has to ask the question whether anything in the process would
prevent us from scaling up the synthesis, say to supply the adsorbent
to equip 50% of all power plants with a carbon capture adsorption
process containing this material. A bottleneck for such a scale-up could
be the abundance of certain elements; if the global employment of our
favorite absorbent would require, say, 300% of the world reserve of this
element, one would arrive at a very expensive process. The second
component is the operational cost. This cost will be dominated by the
energy requirement. Similarly, as in absorption processes, the energy
requirements are dominated by the compression work and the energy
required to regenerate the adsorbent.
Parasitic energy
As we saw in Section 5.2, we can operate our adsorber using tempera-
ture or pressure swing, or a combination of the two. These different
process confi gurations rely on the difference between adsorption and
desorption conditions to capture (and then release) CO 2 , and they can
vary in their methods of gas-solid contact and heat transfer. These
important factors do not affect performance under equilibrium condi-
tions, hence we will focus on equilibrium process thermodynamics for
our energy analysis. The thermal energy requirement of the process is the
sum of the sensible heat needed to heat the adsorption bed to the pro-
cess temperature required to desorb CO 2 ( Q sen ), and the energy needed