Multiobjective Evaluation of Amine-Based Absorbents for SO 2 Capture Process Using the p K a Mathematical Model.

The screening of high-efficiency and low-energy consumption absorbents is critical for capturing SO ₂ . In this study, absorbents with better performance are screened based on mechanism, model, calculation, verification, and analysis methods. The acidity coefficient (p K _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 SO ₂ cyclic absorption capacity per amine (α _c ) in the amine-based SO ₂ 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, α _c and Q _des of the above five diamines are calculated and verified with the experimental data. The results show that α _c of the diamine changes with the increase in the p K _a value, and the increase in the p K _a value directly leads to changes in Q _des . The order of α _c 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 α _c and Q _des suggests that it is not advisable to simply pursue a higher α _c while ignoring Q _des . The compound quaternary system absorbent has a wider range of α _c than the single ternary absorbent, which is the direction of absorbent development. This study is expected to strengthen absorbent screening for the amine-based SO ₂ capture process from flue gas.
Competing Interests: The authors declare no competing financial interest.
(© 2022 The Authors. Published by American Chemical Society.)