Multiscale energy reduction of amine-based absorbent SO2 capture technology: Absorbent screening and process improvement

• An absorbent screening method was established with SO 2 absorption capacity ( α ) and desorption reaction heat ( Q des ) value as indicators, and then amine-based absorbents with low Q des can be screened out. • The total regeneration energy consumption ( Q tot ) distribution of the four absorbents (MDEA-H 2 O, EDA-H 2 SO 4 -H 2 O, PZ-H 2 SO 4 -H 2 O, and HEP-H 2 SO 4 -H 2 O) were calculated, and the result showed that the latent heat consumption ( Q lat ) was the main reason for the high Q tot of the SO 2 capture process. • Three improved processes (the rich-split, the lean-flash heat pump and the top-steam heat pump processes) were designed to recover the energy available in the SO 2 capture process. • The top-steam heat pump case greatly reduced the Q lat of the SO 2 capture process, and the top-steam heat pump process with the PZ-H 2 SO 4 -H 2 O absorbent was the most energy saving potential process for the flue gas SO 2 capture. The high total regeneration energy consumption ( Q tot ) limits the industrial application of amine-based absorbent SO 2 capture technology, and regeneration energy consumption can be divided into desorption reaction heat ( Q des ), latent heat consumption ( Q lat ) and sensible heat consumption. This work focused on developing an energy-efficient SO 2 capture technology through amine-based adsorbent screening and process improvement, in which desorption reaction heat, being the internal cause of high regeneration energy consumption, was only related to the type of adsorbent. An absorbent screening method was established with SO 2 absorption capacity ( α ) and desorption reaction heat values as indicators. The screening results showed the functional relationship of Q des - α for five organic diamines ethylenediamine (EDA), piperazine (PZ), N-hydroxyethylpiperazine (HEP), N, N'-dihydroxyethylpiperazine (DIHEP), and N-hydroxyethyl-N'-hydroxypropylpiperazine (HEHPP)): according to α EDA > α PZ > α HEHPP > α HEP > α DIHEP , Q des(EDA) > Q des(PZ) > Q des(HEHPP) > Q des(DIHEP) > Q des(HEP) . The latent heat consumption and sensible heat consumption were related to process configuration, and N-methyldiethanolamine (MDEA), EDA, PZ and HEP were screened as amine-based absorbers for process modeling. The energy analysis showed that the order for regeneration energy consumption of the four absorbents followed Q tot(MDEA) > Q tot(EDA) > Q tot(PZ) > Q tot(HEP) , and the energy distribution calculations showed that latent heat consumption had the largest proportion in regeneration energy consumption. Three improved processes (the rich-split, the lean-flash heat pump and the top-steam heat pump processes) were designed to recover the energy available in the system. Compared to the conventional process, the top-steam heat pump case could greatly reduce the regeneration energy consumption, and the Q tot values of the four absorbents (MDEA, EDA, PZ, and HEP) in the top-steam heat pump case were 4.28 GJ·t −1 SO 2 , 3.10 GJ·t −1 SO 2 , 3.13 GJ·t −1 SO 2 and 3.68 GJ·t −1 SO 2 , respectively. According to technical and economic analyses, the top-steam heat pump case under the PZ absorbent system had the most potential for the flue gas SO 2 capture process.