Development of a Potassium Carbonate-based Absorption Process with Crystallization-enabled High-pressure Stripping for CO₂ Capture: Vapor–liquid Equilibrium Behavior and CO₂ Stripping Performance of Carbonate/Bicarbonate Aqueous Systems

Abstract

A novel absorption-based post-combustion CO₂ capture process is being developed to reduce the energy use associated with CO₂ stripping and compression. The process features the use of a concentrated potassium carbonate/bicarbonate (PCB) aqueous solution as a solvent and high-pressure CO₂ stripping with a bicarbonate-dominant slurry enabled by crystallization of the CO₂-rich solution. Vapor–liquid equilibrium data under the typical stripping conditions of the process were measured and CO₂ stripping tests were performed under various pressures, temperatures, PCB concentrations, and CO₂ loading levels using a bench packed-bed stripping column. The results showed that CO₂ stripping with a highly concentrated, highly CO₂-loaded PCB solution/slurry at a high temperature was favored to attain a high stripping pressure and a low water vapor-to-CO₂ pressure ratio in the product gas stream. The total heat use measured for CO₂ stripping with the PCB system was up to three times lower than that of the benchmark 5 M monoethanolamine system under favorable conditions.