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Abstract

The process for CO2 removal from flue gases was modeled with RateFrac. It consists of an absorber, a stripper, and a cross heat exchanger. The solvent used in the model contains about 30 wt % monoethanolamine (MEA) in water. MEA reacts with CO2 in the packed absorber. The finite reaction rate requires a kinetic characterization. The RateFrac absorber model was integrated with a FORTRAN user kinetic subroutine to make the model consistent with the interface pseudo-first-order model and with a regressed Electrolyte-NRTL equilibrium model. It was adjusted with laboratory wetted wall column data and field data from a commercial plant. Sensitivity analyses were performed on process variables to find operating conditions at low steam requirement. Many variables strongly affect the process performance, but an overall optimization shows that there are no economical ways to reduce the steam requirements by more than 10%. The reboiler duty can be reduced from that of a base case representing current industrial operating conditions, by 5% if acids are added to the solvent, by 10% if the absorber height is increased by 20%, and by 4% if the absorber is intercooled with a duty of one-third of the reboiler duty. The power plant lost work is affected by varying stripper pressure, but not significantly, so any convenient pressure can be chosen to operate the stripper.