Development of a Novel Carbonate Absorption Process with Crystallization-Enabled High Pressure Stripping for Post-Combustion CO2 Capture: Kinetic Study of Bicarbonate Salt Crystallization

Development of a Novel Carbonate Absorption Process with Crystallization-Enabled High Pressure Stripping for Post-Combustion CO₂ Capture: Kinetic Study of Bicarbonate Salt Crystallization

Qing Ye^1,2, Manoranjan Sahu², Yongqi Lu² and Xinlei Wang¹

1 Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign

2 Illinois State Geological Survey, University of Illinois at Urbana-Champaign

  

A novel absorption process with high pressure stripping is being developed at our group for the post-combustion CO₂ capture application. The process employs a carbonate salt aqueous solution, such as potassium carbonate (PC), as a solvent. The CO₂ absorption operates at elevated temperature and the bicarbonate in the CO₂ rich solution from the absorber is crystalized in a separate cooling-crystallizer. Slurry of bicarbonate crystals is used in the stripper for CO₂ stripping at high pressure. Compared to conventional mono-ethanol-amine (MEA) processes, the carbonate-based process consumes less stripping heat and CO₂ compression work. A preliminary techno-economic analysis reveals that the energy use of the novel process is 40-50% less than that of its MEA counterpart.

Crystallization of the bicarbonate from the CO₂-rich PC solution is a key step in the carbonate-based process. Kinetic studies of the bicarbonate crystallization were performed under continuous mix suspension, mixed product removal (MSMPR) mode using an automated calorimetric reactor system. Parametric tests were conducted to investigate the effect of the PC concentration, CO₂ loading, addition of absorption promoter, temperature, residence time, stirring speed, seeding, etc. on the kinetics of the crystallization and morphology of crystal products. Crystal solids were characterized by particle size distribution (PSD), turbidity, SEM, and XRD analysis techniques. Kinetic data, such as the nucleation rate constant, size-dependent growth rate constant, and agglomeration/breakage factor, were obtained by fitting the differential PSD data under various operating conditions.

This presentation will provide a summary of the results from the crystallization kinetic study and discuss their implications for the crystallizer design.