Due to the fast-growing concern abo

Due to the fast-growing concern about global warming,
which can be attributed primarily to the elevated CO2 level
in the atmosphere (Kondili and Kaldellis 2007; RomanLeshkov et al. 2007), the United Nations promoted the
Kyoto Protocol (1997) with the objective of reducing
greenhouse gases by 5.2% on the basis of the emission in
1990, and more than 170 countries have ratified the
protocol (Gutierrez et al. 2008). Various CO2 mitigation
strategies have been investigated, which can be generally
classified into two categories: (1) chemical reaction-based
approaches and (2) biological CO2 mitigation. A popular
chemical reaction-based CO2 mitigation approach is achieved
by cyclic carbonation/de-carbonation reactions in which
gaseous CO2 reacts with solid metal oxide (represented by
MO) to yield metal carbonate (MCO3; Gupta and Fan 2002).
The reaction can be represented by Eq. 1.
MO þ CO2 ! MCO3 ð1Þ
Once the metal oxide reaches its ultimate conversion,
metal carbonate can be thermally regenerated to metal
oxide and CO2 by heating the metal carbonate beyond its
calcination temperature. The calcination reaction can be
represented by Eq. 2. An actual installation of this chemical
reaction-based CO2 separation process in a fossil-fuel-fired
utility would consist of a carbonation reactor and a
regeneration reactor. Lime, with CaO being the primary
component, is probably the most popular solid adsorbent
for chemical reaction-based CO2 mitigation due to its
relatively low costs (Cooper and Alley 1994).
MCO3 ! MO þ CO2 ð2Þ
Another gas-absorption process for the separation of
carbon dioxide from a gas mixture is washing with aqueous
amine solution (Resnik et al. 2004), among which monoethanolamine (Bonenfant et al.) is the most widely
employed (Blauwhoff et al. 1984). Packed bed or plate
columns have been investigated to facilitate the contact of
a liquid adsorbent with the gas stream (Krumdieck et al.
2008; Lin et al. 2003). CO2 desorption and, therefore, the
regeneration of monoethanolamine could be performed by
heating the product solution to facilitate the reverse reaction. Water vapor in the regenerated CO2 could be easily
separated by condensation. CO2 fixation and desorption
reactions can be represented by Eqs. 3 and 4, respectively