(498d) Chemical Engineering in Cement Decarbonization

Cement is the binding agent in concrete, the most widely used material on Earth after water. Cement production accounts for 7.5% of global CO2 emissions due to (1) the use of CO₂-bearing limestone (CaCO₃) as a feed rock and (2) high process energy requirements. Brimstone has developed a breakthrough, deeply decarbonized process to co-produce ordinary portland cement (OPC) and supplementary cementitious material (SCM) by using carbon-free calcium silicate rocks instead of limestone. Brimstone is the first company to make OPC that meets the ASTM C150 standard without using limestone as a feed rock. The Brimstone process involves leaching of calcium silicate rocks instead of CO₂-bearing limestone, purification of the resulting brine to selectively recover a calcium-containing product, and thermal treatment to create OPC and regenerate the leaching agent. Brimstone is currently scaling its industrial process to deliver deeply decarbonized industry-standard cement and SCM at competitive market prices without the need for carbon capture technologies.

Chemical engineering has a critical role in the successful scale-up of the Brimstone process. This is illustrated through the development of the leaching reactor. Development of a suitable compositional model for the feed rock enabled accurate capture of the leaching reaction exotherm. Kinetic models allowed for translation of batch laboratory data to a large-scale, continuous commercial reactor. Thermodynamic models of electrolytes were tuned to accurately represent the solubility of the various metal salts in the post-leach brine. Process development unifies this information into a process model that establishes the foundation for scale-up to pilot, demonstration, and commercial plants.