Abstract
Due 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.
Highlights
The strict regulations of nitrogen oxides (NOx) emissions induce the introduction of NOx control technologies to all industry levels
The results indicate that the addition of Farmatan in more than 1 wt. % delays the start of the setting
Because the chestnut tannin in Farmatan belongs to a group of hydrolysable tannins [16] same as the tannic acid, it can be stated that the delay in hydration in Farmatan samples is caused only by sugars
Summary
The strict regulations of nitrogen oxides (NOx) emissions induce the introduction of NOx control technologies to all industry levels. The flue gas contains SO3 and water These compounds react to form soluble ammonium salts, mainly ammonium bisulfate (NH4HSO4) and ammonium sulfate ((NH4)2SO4) [4]. Ammonia captured in the fly ash in the form of soluble salts could be released as an ammonium gas or could be leached to water. Tannins are a class of natural polyphenolic biomolecules that bind to and precipitate proteins and other organic compounds [8] They are found in a variety of plants, mainly in wood and fruits. As was mentioned above, during the preparation of AAC the ammonium gas is released from the SNCR fly ash which deteriorates the working space. The possibility of binding the ammonia into the insoluble compound using natural tannins is examined For this purpose, the extract from chestnut wood and pure tannic acid was used.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IOP Conference Series: Materials Science and Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
