Amine scrubbing is the most mature CO2 capture technology for fossil fuel power plants, but the energy use for CO2 regeneration and compression will be 20 to 25% of the power plant output. The objective of this work is to develop alternative stripper configurations that reduce the energy use of CO2 capture. The advanced stripper configurations were modeled and optimized using Aspen Plus. Total equivalent work was used as an indicator of overall energy performance accounting for reboiler duty, compression work, and pump work. The rich exchanger bypass recovers stripping steam heat by using an exchanger. To get better energy performance, this strategy was applied to advanced configurations including a reboiler-based stripper, an interheated stripper, and a flash stripper. Both 9 m monoethanolamine (MEA) and 8 m piperazine (PZ) were investigated. The best energy performance was obtained from the stripper with a warm rich bypass and a rich exchanger bypass, which provides 10% less equivalent work for PZ and 6% less for MEA compared to the simple stripper. A flash stripper with a warm rich bypass and rich exchanger bypass uses 9% less energy with PZ and 5% less with MEA. With the warm rich bypass and rich exchanger bypass, MEA can provide 8% less equivalent work at 135 °C with acceptable thermal degradation.

This study determines the energy benefit of advanced stripper configurations for 8 m PZ, 7 m MDEA/2 m PZ, and 5 m MDEA/5 m PZ. Three novel configurations were tested: (1) interheated stripper, (2) two-stage flash with cold rich bypass, and (3) two-stage flash with cold rich bypass and a low temperature adiabatic flash. Generally, increasing the complexity improved process performance, but in some cases the improvements were too marginal to justify the additional capital cost. Configuration 3 has the added benefit of removing entrained oxygen before feeding the solvent to the high temperature flash vessels, but its energy performance is very sensitive to operating conditions. This paper also describes the creation of a thermodynamic, hydraulic, and kinetic model in Aspen Plus ® that predicts experimental data for 8 m PZ, 7 m MDEA/2 m PZ, and 5 m MDEA/5 m PZ over operationally significant temperature and loading ranges. The next step in this work will include conducting techno-economic studies to quantify the capital and operating cost tradeoffs associated with these novel configurations.

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