Multiobjective Evaluation of Amine-Based Absorbents for SO(2) Capture Process Using the pK(a) Mathematical Model

[Image: see text] 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 (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 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 pK(a) value, and the increase in the pK(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.