Comparison of Amine-Based Absorbents for Post-Combustion Carbon Capture

As a part of this work, we have performed a comparison of 4 amine-based absorbents using the process simulation software ProMax^® with TSWEET^®. Absorbents were compared at pulverized coal fired power plant flue gas conditions. The criteria for comparison of absorbents are the energy requirement and absorber and stripper dimensions for 90% CO₂ capture (separation + compression) from a 500 MW pulverized coal fired power plant which are loosely representative of the operating and capital cost respectively. Due to the large flow-rate (~1100 MMSCFD) of flue gas that must be processed by the separation system, use of 3 absorber/stripper trains is proposed. Separated CO₂ is compressed to a pipeline pressure of 8MPa using a 4 stage compressor train. The amine absorbents considered for comparison are monoethanolamine (MEA), diethanolamine (DEA), diglycolamine (DGA) and 2-amino-2-methyl-1-propanol (AMP). The parameters explored as a part of this study includes – absorbent concentration, lean absorbent entry temperature into the absorber column, stripper pressure. On the basis of our findings, we report that diglycolamine (DGA) and diethanolamine (DEA) are superior absorbents than monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP) for CO₂ capture. A higher stripper pressure reduces the overall energy requirement for CO₂ capture by decreasing the stripping steam requirement as well as reducing the compression costs. Figure 1 and Figure 2 are plots of change in stripper diameter and overall energy duty for CO₂ separation with change in the stripper pressure.

                                                                                                                                                     Figure 1: Stripper Diameter Vs. Stripper Pressure

                                                                                                                                             Figure 2: Energy Duty for CO₂ separation Vs. Stripper Pressure