| Chemical absorption, a main technology for post-combustion CO2capture, is considered as the most promising technology for its mature in technology and don’t have to make big changes in existing power plant. But the economic problem should be solved before putting this technology into practice, especially the energy consuming for solvent regeneration. Convention amine-based solvents are limit in energy saving, so some researchers propose to take advantage of the phase changing phenomenon to decrease the regeneration energy. According to the preliminary study, the phase transition solvents could regenerate at a low temperature below100℃, which had a great energy saving potential. The thesis focused on the lipophilic amines which have liquild-liquild phase transition behavior, and studied it from several aspects such as the absorption and regeneration mechanism, activated amines, solvents screening and regeneration energy calculation.The distribution of CO2in solvents of DPA/DMCA/MCA during the absorption and desorption progress were studied. The experiment showed that CO2distribution and phase changing behavior are different in the tertiary amine DMCA and primary and secondary amines (DPA/MCA). This may be caused by their different reaction mechanism with CO2.The absorption and desorption characters of DMCA and MCA at different temperature were studied (absorption at15℃、25℃、35℃,desorption at70℃、80℃、90℃). The appropriate temperature for MCA is35℃for absorption and90℃for regeneration. However, as for DMCA, it is recommended to choose25℃for absorption and80℃for regeneration.Adding activator to tertiary amines which can easily forming two phases during desorption, aimed to improve the absorption rate while using the auto-extration mechanism. MCA, PZ, BDA, as the activators, were added to DMCA, DSBA and DEEA at different ratio. A comparative analysis revealed that the mixed solvent DMCA15%+MCA15%DSBA15%+MCA15%and DMCA25%+PZ5%show greater advantages in overall performance. Especially. DMCA15%+MCA15%has comparable absorption rate to the standard solvent30%Ethanolamine (MEA), and its cyclic net loading is69%higher than the30%MEA and cyclic net loading has a great increase from2.67to6.57mol/kgsolute.The experiment study of absorption and desorption at same concentration for20solvents were carried out (absorption at25℃, desorption at80℃). Through a comprehensive evaluation with the absorption rate、capacity、circle net loading and regeneration rate, the results showed that:3-Pipecoline and4-Pipecoline have faster reaction rate than N-Methylcyclohexylamine (MCA), circle net loading and regeneration rate is lower than MCA; no tertiary amine is better than DMCA in this work. Among multistage amines,1,4-diaminobutane and1-(2-aminoethyl) piperazine have fast absorption rate with big circle net loading and high regeneration rate.The regeneration energy of the phase changing solvents was calculated with a simplified model of the desorber. Regeneration energy of phase transition solvents studied in this work is41%lower than30%MEA. The novel phase transition solvent have a high circle loading and regenerate effectively at a low temperature of80℃, which lead to decrease the sensitive heat and the heat carried by regeneration mixed gases.This study shows that the phase transition solvents have high circle net loading with good absorption rate and have great energy saving potential. |
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