Ammonia Measurement Investigation Using Quantum Cascade Laser and Two Different Fourier Transform Infrared Spectroscopy Methods 2020-01-0365

Most diesel engine exhausts have been fitted with SCR (Selective Catalyst Reduction) in order to reduce NO_X (Oxides of Nitrogen) by using NH₃ (ammonia). However, both NO_X and NH₃ have been classified as compounds hazardous for the environment and human health. If the reaction between NO_X and NH₃ is unbalanced during treatment, it can lead to either NO_X or NH₃ being released into the environment. Accurate measurement is thus necessary. QCL (Quantum Cascade Laser) and FTIR (Fourier Transform InfraRed) are two methods that have been used to measure NH₃ and NO_X directly in diesel engine exhausts. However, only a few studies have compared those two methods of NH₃ measurement, mainly from diesel engine exhausts. The aim of this paper is to compare the QCL and 2 different FTIR specifications for NH₃ measurement directly from diesel engine exhausts under well-controlled laboratory conditions. Researchers have found that as NH₃ is reactive, it is absorbed inside the exhaust pipe if the probe location is some distance away from the SCR. The results reported here contradict this and show that the probe location has only a small impact on NH₃ measurement inside the exhaust pipe. Furthermore, both instruments gave comparable results with the necessary regulatory precision. The outcome from this paper will have an impact on the discipline of NH₃ measurement and industry in the way NH₃ from diesel engines is measured.