Phase-change absorption for SO2 capture by a novel aqueous BHEP/ether solution
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.
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维普
