Gaurav Sant, Pritzker Professor of Sustainability and Founding Director of the Institute for Carbon Management, and Fabian Rosner, Assistant Professor of Civil and Environmental Engineering at the University of California, Los Angeles, presented a webinar for NEU on the decarbonization of the cement product.
Limestone (calcite, CaCO3) is an abundant, reactive, and cost-effective source of calcium oxide (CaO) for cement and lime production. However, the thermochemical decomposition of limestone (~ 800 °C, 1 bar) to produce lime (CaO) results in substantial carbon dioxide (CO2(g)) emissions and energy use. Sant and Rosner discussed a pathway to use CaCO3 as a Ca-source to make hydrated lime (portlandite, Ca(OH)2; a precursor for cement clinker production) at ambient conditions (p,T) – while suppressing CO2(g) emissions – via an aqueous flow electrolysis/pH-swing process that co-produces hydrogen (H2(g)), and oxygen (O2(g)).
The Zero CArbon Lime (ZeroCAL) process includes three steps: (Step 1) chelator promoted dissolution of CaCO3, and the complexation of Ca-cations under slightly basic (> pH 9) conditions, (Step 2a) Ca-enrichment and separation using nanofiltration (NF) that allows the separation of the Ca-EDTA complex from the accompanying bicarbonate (HCO3–) species, (Step 2b) acidity-promoted decomplexation of Ca from EDTA which allows near-complete chelator recovery and the formation of a Ca-enriched feed solution, and (Step 3) the rapid precipitation of Ca(OH)2 from the Ca-enriched feed solution using electrolytically produced alkalinity. These reactions are conducted in a seawater matrix yielding co-products including hydrochloric acid (HCl), and sodium bicarbonate (NaHCO3). Careful analysis of the reaction stoichiometries and energy balances indicates that around 1.35 t of CaCO3, 1.09 t of water, 0.79 t of sodium chloride (NaCl), and ~ 2.5 MWh of net electrical energy are needed to produce 1 t of Ca(OH)2, with significant opportunity for process intensification. This concept has major implications for decarbonizing cement clinker production within a paradigm that emphasizes the use of existing cement plants and electrification of industrial operations.
Gaurav is a Professor and the Pritzker Endowed Chair in Sustainability at the Samueli School of Engineering at the University of California, Los Angeles (UCLA). He holds faculty appointments in the Departments of Civil and Environmental Engineering, Materials Science and Engineering, and the California Nanosystems Institute. Gaurav has published over 200 publications and has an h-index of 55. He is also the Director of UCLA's Institute for Carbon Management (ICM): a cross-campus technology translation institute. Gaurav is the Co-Founder of Equatic Inc., the Grand Prize Winner of the Temasek Foundation’s 2021 Liveability Challenge, the Co-Founder of Concrete-AI Inc., the Co-Founder of Nextli Technologies Inc., and the Founder of CarbonBuilt Inc., a Grand Prize Winner of the 2021 NRG COSIA Carbon XPRIZE. Gaurav has served as an expert providing: a) testimony to the U.S. Senate, U.S. House of Representatives, and the California State Senate, and b) strategic consulting, core R&D, and innovation support to Fortune500 corporations, government agencies, foundations, and industry organizations globally. Gaurav earned his B.S. (2006), M.S. (2007), and Ph.D. (2009) from Purdue University.
Fabian Rosner is an Assistant Professor of Civil and Environmental Engineering at the University of California, Los Angeles. His research focuses on renewable energy and chemical technologies. Fabian leads research efforts in carbon capture – point source capture and direct air capture – CO2 utilization, and electrochemical conversion technologies. Before joining UCLA, Fabian was a postdoctoral fellow at Lawrence Berkeley National Laboratory. He holds a Ph.D. and M.S. in Mechanical and Aerospace Engineering, with specialization in thermal sciences, from the University of California, Irvine. He also earned M.S. and B.S. degrees in Chemical Engineering, specializing in chemical process engineering, from the Technical University of Munich in Germany.
For questions or to learn more about ZeroCAL, contact NEU.