Abstract:

Due to the high energy consumption in SO₂ capture by organic amine solution, a novel liquid-liquid phase-change absorbent composed of N,N'-bis(2-hydroxyethyl) piperazine (BHEP) organic amine, diethylene glycol diethyl ether (DEGDEE) and water was developed. The absorption-desorption performance and phase-change mechanism were also investigated. There was a significant polarity difference between nonpolar ether and the polar ammonium salts formed by the reaction of BHEP and SO₂. Consequently, the phase-change occurred when the ammonium salts separated from the nonpolar ether. The content of DEGDEE in the upper phase was higher than 97%, while the contents of BHEP, SO₂, and H₂O were lower than 1%. Therefore, the upper phase could be directly recycled. Over 99% of BHEP and SO₂ were concentrated in the lower phase. Accordingly, only the SO₂-rich phase went to the stripper for the thermal regeneration, and thus the energy consumption could be effectively reduced. The higher the content of BHEP or DEGDEE, the easier the phase separation, and the smaller the proportion of the lower phase volume and the DEGDEE distribution rate. In addition, the content of both distribution rates of SO₂ and BHEP had almost unaffected. However, when the concentrations of both SO₂ and BHEP were too high, DEGDEE was immiscible with BHEP before SO₂ scrubbing. The physical absorption of SO₂ by DEGDEE resulted in an enhancement of the absorption capacity for SO₂ by BHEP. Moreover, the cyclic absorption capacity and desorption rate with the mixture of 15% BHEP+20% DEGDEE+65% H₂O were increased by 6.43% and 10.59%, respectively, and the energy consumption was decreased by 13.69%, as compared to a 15% BHEP solution. All the results showed that the biphasic solvent proposed had a promising prospects for sulfur dioxide capture.

Key words: liquid-liquid phase-change, piperazine-based organic amine, ether, SO₂ capture, absorption, desorption

摘要：

针对有机胺湿法烟气脱硫过程能耗高的问题，本文开发了一种新型的N,N′-双(2-羟乙基)哌嗪有机胺（BHEP）/二乙二醇二乙醚（DEGDEE）水系液-液相变吸收剂，并研究其吸收解吸SO₂性能及相变机理。结果表明，BHEP与二氧化硫（SO₂）反应生成了极性较强的铵盐，与非极性醚差异较大，产生盐析效应而导致其分相。上相中DEGDEE的浓度很高，质量分数大于97%，胺、SO₂和水的质量分数低于1%，可直接循环使用；约有99%以上的胺和SO₂富集在下相，只需对下相解吸，从而大大地降低了能耗。有机胺BHEP和DEGDEE的浓度越高，越易发生相变，下相体积占比和DEGDEE分配率越小，SO₂和BHEP的分配率几乎不受影响；两者浓度太高时还会发生吸收前分相。DEGDEE对SO₂的物理吸收使体系的吸收能力提高，在质量分数15% BHEP水溶液中加入质量分数20%的DEGDEE后，循环吸收容量和解吸率分别提高了6.43%和10.59%，能耗降低了13.69%，该相变吸收剂具有较好的应用前景。

关键词: 液-液相变, 哌嗪类有机胺, 醚, SO₂捕集, 吸收, 解吸