Electrolytic cement clinker precursor production sustained through orthogonalization of ion vectors†

Abstract

Electrochemical reactors can reduce the carbon intensity of cement production by using electricity to convert limestone (CaCO₃) into Ca(OH)₂, which can be converted into cement clinker by reacting with silica (SiO₂) at high temperatures. A key challenge with electrochemical reactors is that the deposition of solid Ca(OH)₂ at the membrane leads to unacceptably low energy efficiencies. To address this challenge, we connected the electrochemical reactor used for limestone calcination (“cement electrolyser”) to a distinctive chemical reactor (“calcium reactor”) so that Ca(OH)₂ forms in the calcium reactor instead of within the electrochemical reactor. In this tandem system, the cement electrolyser generates H⁺ and OH⁻ in the respective chemical and cathode compartments. The H⁺ then reacts with CaCO₃ to release Ca²⁺, which is diverted into the calcium reactor to react with the OH⁻ to form Ca(OH)₂. We fabricated a composite membrane to selectively block the transport of Ca²⁺ into the cathode compartment. Charge balance in the cement electrolyser was enabled with monovalent ions (e.g., K⁺) as the positive charge carrier. This orthogonalized ion management was validated by operando imaging. The tandem reactor enabled the electrolysis process to operate for 50 hours at 100 mA cm⁻² without any voltage increase, which represents a meaningful step forward for electrochemical cement clinker precursor production.