A novel Hot Carbonate Absorption Process with Crystallization-Enabled High Pressure Stripping (Hot-CAP) is being developed at the University of Illinois at Urbana-Champaign to overcome the energy use disadvantage of the monoethanolamine (MEA)-based processes. The Hot-CAP uses a carbonate salt, such as potassium carbonate (K2CO3, PC) or sodium carbonate (Na2CO3, SC), as a solvent. The process integrates four major unit operations including CO2 absorption at elevated temperature (60-80°C), crystallization of bicarbonate from CO2-rich solution to recover the carbonate, CO2 stripping of bicarbonate slurry at high-pressure (up to 40 bar), and reclamation of a sulfate salt as the byproduct of sulfur dioxide (SO2) removal.
Process feasibility studies were performed for these four major unit operations based on vapor-liquid equilibrium, solid solubility, and kinetic data that are available in the literature. Preliminary results show that to achieve 90% CO2 removal, the energy use of the Hot-CAP is about 40-50% less than that of its MEA counterpart due to a low heat of absorption (7-17 kcal/mol CO2 with the heat of bicarbonate crystallization included), a higher CO2 working capacity (1-1.5 times higher than MEA), and reduced compression work (>50% lower than the MEA processes). Process engineering data for these unit operations specific to the Hot-CAP condition will be experimentally obtained, and current efforts are focused on measuring the kinetic data of CO2 absorption into the carbonate solutions at elevated concentrations and temperatures, while also investigating the role of promoters/catalysts in promoting the CO2 absorption rate. This presentation will provide a summary of the results from the process feasibility analysis and the absorption kinetics study, which are the initial tasks in a three-year, DOE-funded research project focused on the development of an advanced solvent-based CO2 capture process for coal-based power plants.