Identification of the cost-optimal degree of CO2 capture: An optimisation study using dynamic process models

The capture of CO2 emissions from fossil-fuel fired power plants by CO2 capture using amine solvents is considered an attractive method with which to mitigate anthropogenic CO2 emissions whilst simultaneously ensuring availability of energy supply. However, these processes are capital intensive and impose large efficiency penalties on the power plants with which they are integrated. It is thus important to design and operate these systems in a life-time cost optimal fashion. In this work, we present the results of an optimisation study aimed at identifying the cost-optimal degree of CO2 capture using post-combustion amine-scrubbing integrated with a 660 MWe sub-critical coal fired power station. To address this question, we carry out an optimisation study using a dynamic, non-equilibrium model of an absorption process, explicitly considering the trade-off associated with the cost of emission of CO2 to atmosphere against the opportunity cost associated with reducing the electricity output of the power plant. We find that a 95% rate of CO2 capture appears to be optimal. Sensible heating of CO2 rich solvent was found to be a very important contribution to energy penalty associated with solvent regeneration, highlighting the need for efficient heat integration and waste heat utilisation. Capture-bypass options appear promising as a means to reduce first-mover disincentive in the context of the early stage deployment of CO2 capture infrastructure. Finally, access to electricity markets for decarbonised electricity, i.e., operation at relatively high capacity factors would appear to be important to justify investment in CO2 capture plant.

► Optimisation study in gPROMS using a dynamic, non-equilibrium model.
► Solvent regeneration OPEX the majority of total annual cost.
► Total annualised cost a function of CO2 capture level and carbon cost.
► Capture bypass at attractive option for reducing capital cost.