The development and validation of a rapid, in situ method of the determination of NH3 in solid by-products of the combustion process

Abstract

This article presents the following: the developed apparatus and a rapid, in situ (industrial) method of the determination of NH3 in fly ash and gypsum and the application of the method to real samples. Ammonia is released from the fly ash sample by means of the thermal method in 500–600 °C, using a specially designed 500 W electric tubular furnace. The NH3 is determined by means of a Tunable Diode Laser Spectroscope (TDLS). The range of the method is from 0.18 to 375 μg NH3 and the duration of a single analysis is from 2 to 20 min (depending on the concentration of ammonia in the sample). The constructed system is mobile and it can be used for in situ measurements in industrial conditions. The method can be used both to optimize the operation of DeNOx systems (high NH3 concentration in fly ash) and to measure the level of ammonia in the product (NH3 concentration below 100 mg/kg). The method that was developed has been validated and the uncertainty of the method was estimated in accordance with EURACHM guidelines. The paper describes the use of the developed method to optimize the SCR system operation and reduce ammonia slip in fly ash and flue gas.