Mineralization with Capture Integration

The presentation will highlight some key developments in mineralization R&D and how these have influenced our research at ETH Zurich. We started back in 2001 by looking into the far-from-equilibrium dissolution kinetics of the typical San Carlos olivine, which back than was the precursor material of choice. Today, we are using heat-treated serpentine, to pursue the vision of a widespread, additive-free mineralization process with capture integration.

Why widespread? Hundreds of gigawatts of new coal-fired capacity are being planned as we speak, but conventional CO₂ storage by underground injection is heavily opposed - if not banned by law as in some European countries. Hence, when CO₂ mineralization is recognized as the only alternative that guarantees permanent storage, we shall be ready to offer a process that starts from an abundant precursor material.

Why additive-free? Chemicals that promote capture and/or the dissolution/carbonation reaction need to be 100% regenerated, to prevent a potentially negative impact on the environment and a loss of commercial value of the product. At industrial scale, however, such a specification will be hardly realized.

Why capture integration? An energy and cost efficient mineralization process needs to fix CO₂ at the same time while capturing it from the flue gas. Without the help of additives, capture integration is possible only if the precursor material is reactive enough to release magnesium or calcium under lean CO₂ pressure (pCO₂) conditions.

We have shown that thermally activated serpentine can be carbonated in a double-step process that combines a low-level pCO₂-swing with a temperature swing. Serpentine minerals are the world’s most abundant mineralization precursor, and the process yields a pure magnesium carbonate that may prove valuable as a substitute for raw materials in various industries.

While our results have convinced us that there are promising opportunities in this direction, we are not ready to make bold statements about the projected performance of such a process. The presentation will point out challenges related to capture integration in general and in particular to our process; for instance regarding the pre-treatment energy, the water balance, the magnesium to CO₂ ratio of the product, etc. Finally, it will explore out-of-the-box ideas on how some of these issues might be addressed in the future, e.g. by exploiting heat-storage cycles in a concentrated-solar power plant for the thermal pre-treatment of the serpentine.