基于酸度系数(pKa)模型的胺法SO2捕集过程多目标效能分析

筛选高SO₂吸收容量、低解吸能耗的吸收剂是提高胺基烟气SO₂捕集工艺应用潜力的重要途径。本研究采用SMD连续溶剂化模型和密度泛函理论在M05-2X/6-31G*基组水平上预测了5种有机二胺类物质的pK_a，基于预测的pK_a建立起吸收剂对SO₂吸收容量和解吸反应热的数学模型，以探讨有机二胺-酸-水三元体系吸收剂捕集SO₂过程中的效能关系。结果表明，数学模型符合工程精度要求。二胺的SO₂吸收容量和脱质子反应焓都随pK_a增大而增加，筛选有机胺吸收剂展现出对SO₂吸收容量和反应焓的多目标矛盾性特征；量化了5种二胺的SO₂循环吸收容量和解吸反应热的数值关系，在相同SO₂循环容量条件下，5种二胺中羟乙基哌嗪（HEP）的解吸热最小，HEP为有机二胺-酸-水三元体系中的一种潜力二胺类吸收剂。

Multi-objective capacity and heat analysis of amine-based SO2 capture process from acidity coefficient (pKa) model

The screening of absorbent with high SO₂ absorption capacity and low desorption energy consumption is important to improve the amine-based SO₂ capture process from flue gas. The pK_a values of five diamines were calculated using SMD continuous solvation model and density functional theory at the M05-2X/6-31G* base set level. Two mathematical models of SO₂ absorption capacity and desorption reaction heat of diamines were established based on the predicted pK_a values. The relationship of SO₂ absorption capacity and desorption reaction heat was discussed for the diamine-acid-water ternary absorbent system. The results showed that the mathematical model met the requirement of engineering precision. The SO₂ absorption capacity and deprotonation reaction enthalpy of diamines were increased with the increase of pK_a value. In the screening of organic diamine absorbents, the multi-objective contradictory characteristics of SO₂ absorption capacity and reaction enthalpy were revealed. The numerical relationship between SO₂ cyclic absorption capacity and desorption reaction heat of the five diamines was obtained. The desorption reaction heat of hydroxyethylpiperazine (HEP) was the smallest under the same SO₂ circulating capacity among the five diamines. So, HEP is a promising absorbent in organic diamine-acid-water ternary systems.