Stabilization of the ammonia in SNCR fly ash - the influence of tannins presence on the preparation of an autoclaved aerated concrete
Date
2019-08-14
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Mark
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IOP Publishing
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Abstract
Thanks to the legislative regulations on NOx emissions, a selective non-catalytic
reduction (SNCR) technology had been introduced to a coal combustion process in power
plants. The valuable by-product, fly ash, contains ammonia in the form of soluble salts, e.g.
NH4HSO4 and (NH4)2SO4. After mixing SNCR fly ash with cement, thanks to the rise of pH,
the toxic ammonia releases and contaminates the working area, so the presence of these salts is
undesirable in an autoclaved aerated concrete (AAC) manufacturing process. A possible
solution is the conversion of soluble ammonium salts to an insoluble form. Tannins are a class
of polyphenolic biomolecules, which react with the ammonium ions to form insoluble
compounds. The AAC samples were mixed using SNCR fly ash and two different ammonium
binding additives - pure tannic acid and the cost-effective animal food supplement containing
chestnut tannins. The influence of additives on the hydration process of the starting mixture
was studied by isoperibolic calorimetry. The results suggest that the cost-effective source of
tannins retards the hydration. The presence of insoluble compounds was studied by the infrared
spectroscopy.
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Citation
IOP Conference Series: Materials Science and Engineering. 2019, vol. 583, issue 1, p. 1-8.
https://iopscience.iop.org/article/10.1088/1757-899X/583/1/012020
https://iopscience.iop.org/article/10.1088/1757-899X/583/1/012020
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Peer-reviewed
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en