Modeling carbon dioxide capture from a supercritical power plant with ASPEN Plus.

It is likely that in the near future there will be some form of CO2 regulation present in the US. Coal fired power plants are the largest anthroporphic point sources of CO2 emissions and account for 51% of electricity generated in the US. Therefore it is highly probable that CO2 capture will need to be implemented at many U.S. coal fired power plants. ASPEN Plus was used to model the turbine cycle, boiler and the back-end CO2 capture process. A supercritical power plant burning PRB was modeled, and a MEA-H2O solution was used as the amine for the CO 2 capture unit. Four different versions of the power plant were modeled with different heat rate degradations and improvements. The net unit heat rate, without CO2 capture, increased 7.3% above design for the degraded power plant and decreased 5.13% below design for the refurbished power plant. With CO2 capture, the refurbished power plant produces approximately 80 megawatts more than the degraded unit and has a 16.1% lower net unit heat rate. It was found that the two improvements that provided the largest benefit to net power and net unit heat rate were installation of new turbine sections and implementation of two flue gas heat exchangers. The new steam turbines decreased net unit heat rate by 2.16% and the flue gas heat exchangers were able to achieve a reduction in net unit heat rate of 2.50%. One interesting trend noticed in this analysis is that the graphs of the specific reboiler duty were always parabolic in nature and a minimum specific reboiler duty could be associated with one CO2 removal value. This seems to suggest the potential for optimizing the operating conditions of the absorber and stripper based on a given flue gas composition and required CO2 removal level.