Post‐combustion CO 2 capture: chemical absorption processes in coal‐fired steam power plants

The integration of a post‐combustion CO 2 capture unit in a coal‐fired steam power plant leads to a reduction in net power output, where the largest contributors to the power loss are the heat requirement for the regeneration of the chemical solvent in the desorber of the CO 2 capture unit (approx. 2/3) and the auxiliary power demand of the CO 2 compressor (approx. 1/4). In this review, the layout of the overall process is explained and the interaction of the three sub‐processes power plant, CO 2 capture process and CO 2 compressor is discussed. The optimization of process parameters of the CO 2 capture unit – such as solution flow rate and reboiler temperature – is intricate due to the complex interaction of the sub‐processes. It is shown that although the heat requirement for solvent regeneration has the largest impact on the power output of the overall process, the optimal process parameters that lead to the lowest possible heat requirement of the capture unit do not necessarily coincide with the optimal process parameters that make for the most energy efficient operation of the overall process. Therefore, when optimizing process parameters of CO 2 absorption processes in power plants, one should focus on the minimization of the overall power loss instead of solely reducing the heat requirement for solvent regeneration. The described coherences are illustrated by the results of process simulations based on detailed models of a post‐combustion CO 2 capture unit using 7 m (30 wt.‐%) monoethanolamine (MEA), of a supercritical, hard‐coal‐fired steam power plant and of a six‐stage, intercooled CO 2 compressor. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd