CO₂ Capture Processes: Novel Approach to Benchmarking and Evaluation of Improvement Potentials

A consistent and transparent benchmarking methodology is required for comparison and ranking of different technologies for CO₂ capture, and also for evaluation of different means of integrating novel capture process units into power cycles. A novel benchmarking methodology is presented in this work where the difference between the thermodynamic maximum and the technology limited efficiencies quantifies the theoretical improvement potential and is a benchmark for the process. Additionally, the source(s) of this difference in efficiency can point to possible future directions for technology development. . The benchmarking methodology is applied to the three CO₂ capture routes – post-combustion, pre-combustion and oxy-combustion – using simplifying assumptions and with fuels of varying HC ratios. The first step of the benchmarking methodology is defining ideal reversible processes for CO₂ capture with no detailed process information. This enables determination of a consistent thermodynamic maximum efficiency of processes. Results show that apart from methane as fuel, where post-combustion has the lowest thermodynamics limited efficiency penalty, pre-combustion process routes have the lowest thermodynamics limited efficiency penalty, followed by post-combustion and then oxy-combustion. These results should not be seen as an attempt to rank the different capture routes, but rather as the thermodynamic limit for technological improvements.