Vacuum Regeneration of Amine Solvent for Post-Combustion Carbon Capture with Compression Train Integration

Abstract

The main aim of this study is the assessment of vacuum operating pressure for amine based solvent regeneration with respect to plant efficiency and economic in order to conclude about its industrial potential. The capture process considered is the conventional two columns configuration with MEA solvent. A regeneration pressure range from 0.06 to 2.5bar have been investigated. The thermal integration with the power plant has been performed on a new built, advanced supercritical power plant adapted for CO2 capture. Flue gases condensation heat and CO2 compression heat have been fully integrated in the steam cycle. Influence of stripper pressure on optimal lean loading ratio and columns basic design (height and diameter) have been investigated, with a focus on the influence of the CO2 compression heat integration strategy. Calculations of plant efficiency have been completed by simplified economical calculations for the levelized cost of electricity (LCOE) and avoided CO2 (LCCO2) in order to assess the industrial interest of stripper vacuum operation.Regarding plant efficiency the optimal pressure is at the minimum value: i.e. 0.06bar with a loss of efficiency of 7.6%pt. In the pressure range from 0.5bar (medium vacuum) to 2.5bar (standard stripper pressure), plant efficiency is quite stable with a minimum around atmospheric pressure with 9.4%pt loss of efficiency. Regarding plant economics the main impact of vacuum regeneration is not the cost of the larger stripper but the cost of the very large compressor needed to maintain vacuum condition. At very low pressure, absorber and stripper have the same operating temperature therefore the economizer is no longer needed. Coupled with the improved plant efficiency, the effect of pressure on cost of electricity and cost of avoided CO2 is very small. The expected gain for deep vacuum stripper is not large enough to justify pilot demonstration of such operating parameters.