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METHOD FOR RAPID VERIFICATION OF THE PRESENCE OF AMMONIUM SALTS IN FLY ASH AT A CONCRETE PLANT
Abstract
Requirements relating to the quality of the flue gases produced have become more and more stringent in recent years. This is why the electricity producers, especially those using coal-fired units, have been forced to introduce additional environmental technologies. However, most of the coal-fired power plants and waste incineration plants in the Czech and Slovak Republics are following the same path, in particular for economic reasons. They are introducing the selective non-catalytic reduction of nitrogen oxides (SNCR). This method is based on the reduction of nitrogen oxides by injecting a solution of urea or ammonia water into the combustion chamber of the combustion unit. The captured fly ash is thus in direct contact with the injected agent. Direct contact of the high-temperature fly ash with the injected medium results in increased amounts of ammonium salts in the fly ashes that have undergone the SNCR process. The ammonium salts contained in fly ash then react very quickly with alkaline substances, such as cement in a concrete mix, producing gaseous NH3. This gas is characterized by a very unpleasant odour. Therefore, when the fly ash is used the hygiene limits might beexceeded. Very often, but it is not clear whether the fly ash brought to the concrete plant has passed the SNCR mechanism or not. That is why a quick orientation method for detecting the presence of ammonium ions in fly ash was designed and verified. Based on the result of the analysis using this method, it is possible to decide at the concrete plant whether or not the fly ash will be admitted to the silo of the concrete plant. The article briefly describes the methodology of the analysis, highlighting the advantages of the proposed method.
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References6
Decree No. 415/2012 Coll. on the permissible level of air pollution and on the implementation of certain other provisions of the Air Protection Act.
Machac, P., Vavrova, J., What we know about the non-catalytic reduction of nitrogen oxides (in Czech), University of Chemistry and Technology Prague, Czech Republic, 2013.
Snop, R., The influence of SNRC technology from the perspective of the ash processor and distributor (in Czech), Ash in Construction 2015, Brno University of Technology, pp 189-195, 2015.
Government Regulation No. 361/2007 Coll., Which lays down the conditions for health protection at work - PART A List of chemical substances and their permissible exposure limits (PEL) and maximum permissible concentrations (MPC).
Sulc, R., Snop, R., Neruda, J., Skvara, F., Peterova, A., Report on the issue of fly ash after SNCR technology as an admixture in concrete, Prague, 2017.
Hela, R., Tazky, M., Influence of SNCR on the properties of fly ash in terms of its applicability to concrete, 24th International Conference Concrete Days 2017, Litomysl, Czech Republic, 2017.
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