(92b) DECAB: A New Process for Post Combustion Capture of CO2

Contribution AIChE meeting

DECAB: a new process for post combustion capture of CO₂

E.L.V. Goetheer, E. Kimball and E.
Sanchez Fernandez

This work describes the conceptual design of a novel
separation process for CO₂ removal from flue gas based on precipitating
solvents. The process here described (DECAB) is an enhanced CO₂
absorption based on the Le Chatelier's principle,
which states that reaction equilibrium can be shifted by removing one of the
constituents in the reaction. Depending on the type of amine different species
are predominantly formed. In the case of primary amines carbamate
is predominantly formed according to the equilibrium reaction (1).

                    (1)

In reaction (1), the equilibrium can be shifted to the
formation of carbamate (R-NHCOO^-) by
removing the protonated amine (R-NH₃⁺)
from the reaction medium. This will result in a higher absorption capacity. For
this purpose an amino acid species has been selected. Amino acids react with CO₂
in principle in the same way as alkanol amines ([5]).

(2)

A conceptual design of this process has been developed based
on literature data, thermodynamic principles and a limited number of
experiments. The Figure below shows a block diagram that includes the main
steps / functions of the process. The flue gas needs to be contacted with the solvent
(absorption block). The CO₂ reacts with the solvent, as in reaction
(2) resulting in a slurry that contains the carbamate
and the precipitated amino acid.
Crystals
are dissolved (crystal dissolution block) and then the solvent is regenerated
(Regeneration block) and the resulting CO₂ product is compressed.

 Block diagram showing the structure of the
process

As solvent example, the potassium salt of taurine was selected. The strategy followed is based on the
compilation and determination of the key properties and parameters that govern
the absorption and regeneration of the solvent. Then, the performance of the
process is evaluated with the aid of short cut design methods. Results show
that the key advantages of this process are environmental friendliness (no
emissions to the air) and low energy consumption related to a lower vapor
pressure of the solvent and higher net loading than conventional processes. The
design developed allows for future economic evaluation and assessment of
options that will further lead to benefits over conventional processes.