Post-combustion CO2 capture from a natural gas combined cycle by CaO/CaCO3 looping

CaO/CaCO3 looping has been evaluated as a potential alternative to MEA for post-combustion CO2 capture from natural gas fired combined cycles (NGCC). CaO/CaCO3 looping has the advantage that there are no emissions of potentially toxic chemical residues and by-products to the environment. A steady-state heat and mass balance model was set up and solved using model parameters from the literature. Post-combustion capture with CaO/CaCO3 looping requires heat supply at high temperature in the calciner and is provided through internal combustion of natural gas with oxygen. Process simulations of six different configurations for the entire NGCC with post-combustion capture resulted in net thermal efficiency in the range 45.6-48.1%, given the process assumptions made and a CO2 capture rate in the range of 90.3-91.3%. These figures should be compared to 49.5% for the NGCC reference case with MEA-based capture. The resulting purity of captured CO2 is lower for CaO/CaCO3 looping due to presence of excess oxygen and inert nitrogen and argon. Increased CO2 purity can, however, be obtained through higher O-2 purity, however at the cost of higher air separation unit energy penalty. It is believed that further process integration and optimisation may enable further increase of the process efficiency for CO2 capture with CaO/CaCO3 looping. Moreover, another benchmarking approach of interest would be to perform a comparative life-cycle assessment (LCA) study to benchmark the environmental impact of CaO/CaCO3 looping with that of MEA scrubbing. (c) 2012 Elsevier Ltd. All rights reserved.