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Toward electrochemical synthesis of cement-An electrolyzer-based process for decarbonating CaCO₃ while producing useful gas streams.

ABSTRACT: Cement production is currently the largest single industrial emitter of CO₂, accounting for ?8% (2.8 Gtons/y) of global CO₂ emissions. Deep decarbonization of cement manufacturing will require remediation of both the CO₂ emissions due to the decomposition of CaCO₃ to CaO and that due to combustion of fossil fuels (primarily coal) in calcining (?900 °C) and sintering (?1,450 °C). Here, we demonstrate 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. We show that the solid Ca(OH)₂ product readily decomposes and reacts with SiO₂ to form alite, the majority cementitious phase in Portland cement. 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.

SUBMITTER: Ellis LD

PROVIDER: S-EPMC7293631 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Toward electrochemical synthesis of cement-An electrolyzer-based process for decarbonating CaCO3 while producing useful gas streams.

Ellis Leah D LD Badel Andres F AF Chiang Miki L ML Park Richard J-Y RJ Chiang Yet-Ming YM

Proceedings of the National Academy of Sciences of the United States of America 20190916 23

Cement production is currently the largest single industrial emitter of CO2, accounting for ∼8% (2.8 Gtons/y) of global CO2 emissions. Deep decarbonization of cement manufacturing will require remediation of both the CO2 emissions due to the decomposition of CaCO3 to CaO and that due to combustion of fossil fuels (primarily coal) in calcining (∼900 °C) and sintering (∼1,450 °C). Here, we demonstrate an electrochemical process that uses neutral water el ...[more]

PMID: 31527245

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Project description:BackgroundIt is known that a part of natural gas is produced by biogenic degradation of organic matter, but the microbial pathways resulting in the formation of pressurized gas fields remain unknown. Autogeneration of biogas pressure of up to 20 bar has been shown to improve the quality of biogas to the level of biogenic natural gas as the fraction of CO2 decreased. Still, the pCO2 is higher compared to atmospheric digestion and this may affect the process in several ways. In this work, we investigated the effect of elevated pCO2 of up to 0.5 MPa on Gibbs free energy, microbial community composition and substrate utilization kinetics in autogenerative high-pressure digestion.ResultsIn this study, biogas pressure (up to 2.0 MPa) was batch-wise autogenerated for 268 days at 303 K in an 8-L bioreactor, resulting in a population dominated by archaeal Methanosaeta concilii, Methanobacterium formicicum and Mtb. beijingense and bacterial Kosmotoga-like (31% of total bacterial species), Propioniferax-like (25%) and Treponema-like (12%) species. Related microorganisms have also been detected in gas, oil and abandoned coal-bed reservoirs, where elevated pressure prevails. After 107 days autogeneration of biogas pressure up to 0.50 MPa of pCO2, propionate accumulated whilst CH4 formation declined. Alongside the Propioniferax-like organism, a putative propionate producer, increased in relative abundance in the period of propionate accumulation. Complementary experiments showed that specific propionate conversion rates decreased linearly from 30.3 mg g-1 VSadded day-1 by more than 90% to 2.2 mg g-1 VSadded day-1 after elevating pCO2 from 0.10 to 0.50 MPa. Neither thermodynamic limitations, especially due to elevated pH2, nor pH inhibition could sufficiently explain this phenomenon. The reduced propionate conversion could therefore be attributed to reversible CO2-toxicity.ConclusionsThe results of this study suggest a generic role of the detected bacterial and archaeal species in biogenic methane formation at elevated pressure. The propionate conversion rate and subsequent methane production rate were inhibited by up to 90% by the accumulating pCO2 up to 0.5 MPa in the pressure reactor, which opens opportunities for steering carboxylate production using reversible CO2-toxicity in mixed-culture microbial electrosynthesis and fermentation.Graphical abstractThe role of pCO2 in steering product formation in autogenerative high pressure digestion.

Dataset Information

Toward electrochemical synthesis of cement-An electrolyzer-based process for decarbonating CaCO₃ while producing useful gas streams.

Publications

Toward electrochemical synthesis of cement-An electrolyzer-based process for decarbonating CaCO<sub>3</sub> while producing useful gas streams.

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