Selection of MDEA based phase change absorbers and carbon dioxide capture performance
To achieve the purpose of rapid screening of phase change absorbent,a new phase change absorbent-MDEA/polyethylene glycol dimethyl ether(NHD)/H2O was quickly screened with N-methyl diethanolamine(MDEA)as the main absorbent,organic solvent as the phase separation accelerator and water as the solvent,guided by the theory of Hansen solubility parameter.The thermal stability of the phase change absorbent was tested by thermogravimetric analysis(TGA),and the CO2 absorption and desorption performance of the phase change absorbent was investigated by CO2 absorption and desorption experiments,as well as the recycling ability.1HNMR was used to test the distribution of the substances before and after the phase change.The results show that MDEA/NHD/H2O phase change absorb-ent has the highest thermal stability compared with 30％ethanolamine(MEA)absorbent and MDEA/n-butanol/H2O phase change ab-sorbent reported in the literature.NHD as a phase separation accelerator can promote the dissolution of CO2 in the phase transition absorb-ent,MDEA/NHD/H2O phase transition absorbent liquid-liquid phase separation requires the coexistence of NHD and H2O.At the ab-sorption temperature of 25 ℃,the MDEA/NHD/H2O phase change absorbent with a mass ratio of 3∶5∶2 has the highest CO2 absorp-tion capacity of 1.069 5 mol/L.The phase change absorbent developed in this paper can reduce the volume of desorption liquid sent to the desorption unit to 42％.The CO2 desorption efficiency reached 98.96％at a desorption temperature of 90 ℃.The total CO2 cycling capaci-ty of MDEA/NHD/H2O phase change absorbent with a mass ratio of 3∶5∶2 was 9.260 4 mol/L after 10 cycles of absorption at 25 ℃ and thermal desorption at 90 ℃.Compared with 30％MEA absorbent,30％MDEA absorbent and MDEA/n-butanol/H2O phase change absorbent,it has the highest CO2 cycling capacity.The 1HNMR test results showed that the upper liquid phase of the phase change ab-sorbent was mainly composed of NHD,which was a CO2-lean phase.The lower liquid phase is mainly composed of MDEA and MDEAH+,which is a CO2-rich phase.
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