Energy Savings Potential through Waste Heat Recovery from Flue Gas for Post Combustion Co2 Capture

Flue gas from a plant using fossil fuels contains CO2. Thus power/process plants using fossil fuels contribute to climate change if CO2 in flue gas is not captured. The process of CO2 capture from flue gas is called „postcombustion‟ CO2 capture. Existing plants may be retrofitted with this process to minimize CO2 emission. Amine solutions are mostly used for this process to scrub the flue gas. Amine based CO2 capture involves two-stage process. In absorber column flue gas containing CO2 is scrubbed by amine solution to produce CO2-rich solution which is subsequently stripped off absorbed CO2 by heating in a stripper column. The inlet flue gas to the absorber column must be ~40 0 C and hence needs cooling. On the other hand, subsequent stripping process needs significant heating. Thus process of post-combustion CO2 capture has an energy penalty which reduces the overall efficiency of the plant. In this paper, waste heat recovered from the flue gas during its cooling before being introduced to the absorber is proposed to be utilized for partial supplement in subsequent heating in stripper. System layouts have been conceptualized and ASPEN Plus ® simulation results for three improved layouts are discussed for energy savings with respect to a base case process. It shows that significant energy savings potential exist by improved process conceptualization.