Combined cycle power plants with post-combustion CO2 capture: Energy analysis at part load conditions for different HRSG configurations

The part-load behaviour of combined cycle power plants (CCPP) equipped with post-combustion CO2 capture is analyzed. Different CCPP configurations are compared, including single-, dual- or triple-pressure level steam generators. The gas turbine is a single shaft unit using the variable guide vanes and fuel flow to control the load. The 90% CO2 capture is achieved using monoethanolamine (MEA 30% wt) as absorbent. In all configurations, the reboiler duty to regenerate the absorbent is partly covered by the hot water of the economizer. This economizer-reboiler loop allows to increase the plant efficiency as the possibility to extract more energy from the economizer results in lowering the steam extraction from the turbine. The dual-pressure level CCPP with CO2 capture gives the best efficiency at the design operation. As the load is reduced, the efficiency of the single-pressure plant becomes comparable to the efficiency of the dual pressure plant, due to the effective thermal integration between the heat recovery steam generator and the absorbent regeneration process. Hence, when CCPPs with CO2 capture operate at part-loads, a further benefit can be achieved with the single-pressure level plant, having it both design simplicity and low efficiency penalties for the CO2 capture. (C) 2016 Elsevier Ltd. All rights reserved.