Development and evaluation of a novel hot carbonate absorption process with crystallization-enabled high pressure stripping for post-combustion CO ₂ capture

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 (K ₂CO ₃, PC) or sodium carbonate (Na ₂CO ₃, SC), as a solvent. The process integrates four major unit operations including CO2 absorption at elevated temperature (60-80°C), crystallization of bicarbonate from CO ₂-rich solution to recover the carbonate, CO ₂ stripping of bicarbonate slurry at high-pressure (up to 40 bar), and reclamation of a sulfate salt as the byproduct of sulfur dioxide (SO ₂) 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% CO ₂ 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 CO ₂ with the heat of bicarbonate crystallization included), a higher CO ₂ 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 CO ₂ absorption into the carbonate solutions at elevated concentrations and temperatures, while also investigating the role of promoters/catalysts in promoting the CO ₂ 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 CO ₂ capture process for coal-based power plants.