NGCC and Hard-Coal Power Plant with CO2 Capture Based on Absorption

When integrating a power plant with post-combustion CO2 capture (e.g. chemical absorption) an efficiency penalty is induced on the joint process. The largest part of this penalty is related to lost power in the power plant steam turbine due to steam extraction used for solvent regeneration. In this work, a detailed integration study has been performed on a natural gas combined cycle (NGCC) and conventional steam power plant. The main task was to minimize the efficiency penalty by identifying the optimal extraction point and steam conditions. Alternative configurations within the capture process were investigated aiming at reducing the overall energy requirement of the capture process. GT PRO and STEAM PRO were used to model the NGCC and hard-coal plant, respectively, while UniSim® was used for capture process modeling. When including CO2 capture, results show an efficiency penalty 7%-points for the NGCC case (reduced from 58.3% to 51.2%), while the penalty of the coal-fired power plant was between 10.6%-points (reduced from 44.2% to 33.6%).Internal process modifications of the capture process indicated an overall energy saving potential of 11.4% when compared to the base case absorption process for the NGCC plant. The corresponding savings potential for the hard-coal plant was 12.1%. This improvement corresponded to an efficiency increase from 51.2% to 52.0% for the NGCC case, and 33.6% to 34.9% for the hard-coal case. Part-load simulations were performed in order to identify how the overall process was affected during part-load operation, with emphasis on parametric variations in the connecting points between the capture plant and power plant cycles.