Efficiency and flexibility potential of Calcium Looping CO2 Capture

The Calcium Looping (CaL) is a proven technology for efficient post combustion CO2 capture from fossil fuel fired power plants. The technology is applied in Dual Fluidized Bed (DFB) systems and offers CO2 capture rates of 90 % and above with low electric efficiency penalty. Early process feasibility studies for Calcium Looping were performed to identify the process potential by means of simplified process simulations based on assumptions and experimental data from lab scale. Now, existing experimental data from pilot scale investigations provide a substantial data base for reliable calculation of process efficiency and efficiency penalty for CO2 capture. Therefore the results of parametric investigations at pilot scale were incorporated into the simulations and new findings like the process improvement potential by natural flue gas water vapor considered. Moreover, the process simulation model was extended with a flue gas recycle for a more realistic process design and a CO2 capture model to predict CO2 capture efficiencies based on the operated process parameters. These novelties were used to identify optimum process operating points and further process optimization potential and process efficiency penalty calculated, considering expenditures for oxygen production by an air separation unit and CO2 compression for storage. The process simulation model is capable to be used as a design tool for process scale-up. Besides efficiency improvement, load flexibility is a major challenge for CCS plants of the future. In the second part of this publication, concepts to increase load flexibility of Calcium Looping CO2 capture systems are presented. For small size power plants up to 200 MWel or industrial CCS plants a turbulent carbonator design with a bottom link to the sorbent calciner represents an interesting option for highest plant flexibility. Both, a fast fluidized carbonator and a turbulent carbonator design was tested at IFK with high capture efficiency and flexibility in operation. (C) 2014 The Authors. Published by Elsevier Ltd.