Demonstration of 99% CO2 removal from coal flue gas by amine scrubbing

Abstract

A post-combustion CO2 capture campaign was conducted at the National Carbon Capture Center (NCCC) with 5 m PZ (piperazine) using the advanced flash stripper configuration. 68 steady-state runs were identified and 90% or to 99.1% CO2 removal was achieved with a 12 m of packing in the absorber. A 20% increase in solvent rate enhanced CO2 removal from 90% to 99% and the rich loading decreased from 0.40 to 0.38 mol CO2/mol alkalinity. With high removal, the temperature profile from modeling indicated there was a mass transfer pinch in the absorber, which means 12 m packing is more than needed even for 99% removal. The rich loading did not decrease significantly at high CO2 removal, therefore the energy cost for regeneration remained practically unchanged.The material balance around the absorber based on CO2 loaded calculated from density and viscosity closed within 2.3%. The rate-based Aspen Plus® model under-predicted the number of transfer units in the absorber by an average of 16%. This was caused by the difference between CO2 concentration measured by titration and calculated from density and viscosity.With the advanced flash stripper (AFS), the process heat duty was between 1.9 and 2.5 GJ/t CO2 and did not increase more than 5% at higher CO2 removal. Due to the fast reaction kinetics of PZ, the 12 m absorber was overdesigned for 99% CO2 removal and the rich loading was unchanged at high removal. Further, the superior design of the AFS recovered the latent heat of water vapor and minimized the energy consumption for solvent regeneration. Therefore, it is feasible to capture 99% of the CO2 from coal-fired flue gas with PZ scrubbing at a reasonable energy cost.