Mixed-Salt Process for Carbon Dioxide Separation | SRI International

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SRI's mixed salt unit

Mixed Salt Process for Carbon Dioxide Separation

SRI’s mixed salt process uses known solvents in a new way to dramatically improve the economics of carbon capture.

Coal-fired power plants and many industrial operations that burn fossil fuels produce carbon dioxide (CO2), a greenhouse gas. Finding cost-effective ways to recover carbon dioxide without creating new environmental concerns is a challenge faced by power plant operators.

SRI is developing a novel “mixed salt” technology based on off-the-shelf low-cost ammonia and potassium-based alkaline salts. These salts have a high loading capacity and readily react with CO2 to remove it from a mixed gas stream. In SRI’s low-energy regeneration process, the salts release the CO2 at high pressure and greater than 99 percent purity.

Other advantages of the process include low sensitivity to impurities; low process cost; stable low-cost and environmentally friendly solvents; low ammonia emissions; reduced water use; and faster CO2 absorption kinetics compared to leading aqueous ammonia-based technologies. 

SRI is building a unit capable of testing flue gas stream up to about 100 kW th to demonstrate that the process can capture CO2 at high efficiency (> 90%) and with very high CO2 loading (> 10 wt.%) in a process that requires less than 2 gigajoules of energy per metric ton of CO2 to regenerate the solvent. This goal is consistent with DOE program goals of 90% CO2 capture rate with 95% CO2 purity at a cost of $40/tonne or less of CO2 captured by 2025.

This material is based upon work supported by the Department of Energy under award number DE-FE0012959. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United Stated Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.