(713d) Advanced Stripper Configurations for CO2 Capture Using PZ and MEA

Authors: 
Lin, Y. J., University of Texas at Austin
Rochelle, G. T., The University of Texas at Austin
Madan, T., The University of Texas at Austin



For post-combustion CO2 capture, steam usage for lean solvent regeneration in the stripper and CO2 compression work are the main contributions to the energy requirement of the process.  Implementing CO2 capture incurs a 20–30% penalty of electricity output for a typical coal-fired power plant. Alternative stripper configurations could improve energy efficiency significantly compared to a simple stripper.  Loss of steam heat from the stripper is one of the reasons that CO2 capture by amine scrubbing is inefficient.  When the stripper is operated at 120–150 oC, water in the rich solvent is vaporized and emitted with CO2 from the top of stripper.  The relative amount of water vaporized to CO2 removed depends on solvent properties.  Solvents with different heat of absorption and tolerable operating temperature preventing dramatic thermal degradation decide how much stripping steam can be recovered.  In this work, PZ and MEA were both investigated.

The objective of this work is to investigate the improvement of rich exchanger bypass strategy applying a heat exchanger to recover steam heat from CO2 vapor by bypassing cold rich solvent.  Several advanced stripper configurations have been modeled and optimized using Aspen Plus®.  Equivalent work is used as an indicator of energy performance instead of only heat duty.  Rich exchanger bypass is applied to advanced stripper configurations including interheated stripper, stripper with warm rich bypass and flash stripper with warm rich bypass.  Also, 9 m MEA and 8 m PZ are both investigated. 

Compared to a simple stripper, the rich exchanger bypass configuration has 7.2% improvement of equivalent work for PZ and 3.7% for MEA.  The interheated stripper and stripper with warm rich bypass have similar energy performance with the lowest equivalent work.  The interheated stripper integrated with rich exchanger bypass has 8.7% improvement for PZ and 5.4% for MEA.  The stripper with warm rich bypass and rich exchanger bypass has 9.2% improvement for PZ and 5.5% for MEA.  A flash stripper with warm rich bypass and rich exchanger bypass configuration has 8.4% improvement for PZ and 4.4% for MEA.  Because the flash stripper can use a smaller solvent residence time at elevated temperature, it can be designed to operate at greater temperature and pressure, with further energy savings.