Optical Analysis System Based on Binary Differential Absorption Intensity Reconstruction Combined with Discretization Variability Analysis: Parallel Temperature and Concentration Detection of NH₃, NO Mixtures

In industrial combustion, parallel measurements of ammonia (NH₃), nitric oxide (NO), and temperature are essential for analyzing and regulating the selective catalytic reduction (SCR) process. Although ultraviolet differential optical absorption spectroscopy (UV-DOAS) is regarded as an ideal measurement method, the simultaneous detection of NH₃, NO, and temperature has not been achieved due to the analytical complexities arising from spectral overlap. Therefore, an optical analysis system is proposed based on binary differential absorption intensity reconstruction combined with discretization variability analysis. First, considering the complexity of the mixed spectra of NH₃ and NO, we establish a spectral mapping transformation from the wavelength domain to the reconstructed domain, using NH₃ and NO as standard spectra, respectively. With the known mutual interference between NH₃ and NO, the absorption features of the two compounds are separated in the reconstructed domain by constructing specific Boolean screening matrices. Second, the law of temperature-induced discretization of the reconstructed spectra of NH₃ and NO is clarified, and the relationship between temperature and discretization is established within the reconstruction domain. Finally, we construct three-dimensional field maps of temperature, concentration, and reconstructed optical parameter (<i>ROP</i>) to measure NH₃, NO, and temperature simultaneously. The results indicate that the analysis system shows good parallel measurement accuracy, with Mean Relative Errors (MRE) of 3.9%, 3.5%, and 2.8% for NH₃ (0-50.0 ppm), NO (0-50.0 ppm), and temperature (290.15-773.15 K), respectively. To the best of our knowledge, the study is the first report on simultaneous measurements of NH₃, NO, and temperature using UV-DOAS.