Bench-Scale Development of a Hot Carbonate Absorption Process with Crystallization-Enabled High Pressure Stripping for Post-Combustion CO2 Capture
Project No.: DE-FE0004360

The University of Illinois at Urbana-Champaign will evaluate the Hot Carbonate Absorption Process (Hot-CAP) process with crystallization-enabled high pressure stripping.  The Hot-CAP is an absorption-based, post-combustion CO2 technology that uses a carbonate salt (K2CO3 or Na2CO3) as a solvent. The process integrates a high temperature (70-80°C) CO2 absorption column, a slurry-based high pressure (up to 40atm) CO2 stripping column, a crystallization unit to separate bicarbonate and recover the carbonate solvent, and a reclaimer to recover CaSO4 as the byproduct of the SO2 removal.

Schematic diagram of the proposed Hot-CAP process
Schematic diagram of the proposed Hot-CAP process (click to enlarge)

A preliminary techno-economic evaluation shows that energy use with the Hot-CAP is about half that of a conventional MEA process. In a typical MEA process there are three components of heat:  the heat of reaction, the sensible heat, and the stripping heat. The Hot-CAP reduces all three heat components. Because the bicarbonate slurry comes from the crystallizer, the stripping process is decoupled with, and thus independent of, the absorption process. The carbonate solution has a smaller heat of absorption than the MEA. With the inclusion of the heat of crystallization, the overall heat of reaction ranges between 7 and 17 kcal/mol CO2 compared to 21 kcal/mol CO2 for MEA. In addition, the use of the bicarbonate slurry results in a significant increase in the working capacity of the solvent. A higher working capacity reduces the energy required to heat the slurry, or the sensible heat. Finally, since the carbonate salt does not degrade at a high regeneration temperature, the Hot-CAP can be operated at higher pressures. A higher stripping pressure reduces the stripping heat as well as the compression work.

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  • For further information on this project, contact the NETL Project Manager, Andrew Jones.