Reactivity of alkaline lignite fly ashes towards CO2 in water

Back, M.; Kühn, Michael; Stanjek, H.; Peiffer, S.; CGS Centre for Geological Storage, Geoengineering Centres, GFZ Publication Database, Deutsches GeoForschungsZentrum; Environmental Geotechnique, Geoengineering Centres, GFZ Publication Database, Deutsches GeoForschungsZentrum

doi:10.1021/es702760v

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Reactivity of alkaline lignite fly ashes towards CO2 in water

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Back, M.
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Kühn, Michael
Deutsches GeoForschungsZentrum;

Stanjek, H.
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Peiffer, S.
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Back, M., Kühn, M., Stanjek, H., Peiffer, S. (2008): Reactivity of alkaline lignite fly ashes towards CO2 in water. - Environmental Science and Technology, 42, 12, 4520-4526.
https://doi.org/10.1021/es702760v

https://gfzpublic.gfz-potsdam.de/pubman/item/item_238202

Abstract

The reaction kinetics between alkaline lignite fly ashes and CO2 (pCO2=0.01-0.03MPa) were studied in a laboratory CO2 flow through reactor at 25-75 °C. The reaction is characterized by three phases that can be separated according to the predominating buffering systems and the rates of CO2 uptake. Phase I (pH>12, <30 min) is characterized by the dissolution of lime, the onset of calcite precipitation and a maximum uptake, the rate of which seems to be limited by dissolution of CO2. Phase II (pH<10.5, 10-60 min) is dominated by the carbonation reaction. CO2 uptake in phase III (pH < 8.3) is controlled by the dissolution of periclase (MgO) leading to the formation of dissolved magnesium-bicarbonate. Phase I could be significantly extended by increasing the solid-liquid ratios and temperature, respectively. At 75 °C the rate of calcite precipitation was doubled leading to the neutralization of approximately 0.23 kg CO2 per kg fly ash within 4.5 h, which corresponds to nearly 90 % of the total acid neutralizing capacity.