Electrochemical production of cement
Researchers recently demonstrated an electrochemical process that uses neutral water electrolysis to produce a pH gradient in which CaCO3 is decarbonated at low pH and Ca(OH)2 is precipitated at high pH, concurrently producing a high-purity O2/CO2 gas mixture (1:2 molar ratio at stoichiometric operation) at the anode and H2 at the cathode. They show that the solid Ca(OH)2 product readily decomposes and reacts with SiO2 to form alite, the majority cementitious phase in Portland cement.
Use of the produced hydrogen as fuel
Electrochemical calcination produces concentrated gas streams from which CO2 may be readily separated and sequestered, H2 and/or O2 may be used to generate electric power via fuel cells or combustors, O2 may be used as a component of oxyfuel in the cement kiln to improve efficiency and lower CO2 emissions, or the output gases may be used for other value-added processes such as liquid fuel production.
Analysis shows that if the hydrogen produced by the reactor were combusted to heat the high-temperature kiln, the electrochemical cement process could be powered solely by renewable electricity.
The study is published in: Proceedings of the National Academy of Sciences of the United States of America (PNAS), September 16, 2019.