The screening of
high-efficiency and low-energy consumption absorbents
is critical for capturing SO2. In this study, absorbents
with better performance are screened based on mechanism, model, calculation,
verification, and analysis methods. The acidity coefficient (pK
a) values of ethylenediamine (EDA), piperazine
(PZ), 1-(2-hydroxyethyl)piperazine (HEP), 1,4-bis(2-hydroxyethyl)piperazine
(DIHEP), and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)piperazine (HEHPP)
are calculated by quantum chemical methods. A mathematical model of
the SO2 cyclic absorption capacity per amine (αc) in the amine-based SO2 capture process is built
based on the electroneutrality of the solution. Another model of desorption
reaction heat (Q
des) is also built based
on the van’t Hoff equation. Correspondingly, αc and Q
des of the above five diamines
are calculated and verified with the experimental data. The results
show that αc of the diamine changes with the increase
in the pK
a value, and the increase in
the pK
a value directly leads to changes
in Q
des. The order of αc of the above five diamines is EDA > PZ > HEHPP > HEP >
DIHEP, and
the order of Q
des is EDA > PZ >
HEHPP
> DIHEP > HEP. The multiobjective analysis between αc and Q
des suggests that it is
not advisable
to simply pursue a higher αc while ignoring Q
des. The compound quaternary system absorbent
has a wider range of αc than the single ternary absorbent,
which is the direction of absorbent development. This study is expected
to strengthen absorbent screening for the amine-based SO2 capture process from flue gas.
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