In this work, we report the development of an online in situ UV absorption sensor for simultaneous diagnostics of NO concentration and temperature in hot process gases ( T > 800 K). That would allow process control in terms of efficiency and NO x emissions, the latter using primary (e.g., burner optimization) or secondary (e.g., flue gas cleaning) methods.
Ĭonsidering the limited experience of the heavy process industry with electro fuels, fast simultaneous in situ monitoring of NO concentration and temperature at different parts of the process would be advantageous. The plasma discharge can also generate a lot of NO x. For example, in pilot-scale experiments comparing different renewable alternatives to fossil fuels in straight-grate induration machines, it was found that H 2 combustion results in much higher NO x emissions than fossil oil combustion. Unfortunately, the electro fuels might be a source of significant NO x emissions. An important precondition for the replacement of fossil fuels is that the combustion/heating performance of the sustainable system would be the same and that the release of pollutants, such as NO x, would be kept low. For example, in the hydrogen break through iron making technology (HYBRIT) initiative ( ) and the CemZero project ( ), the focus is to replace fossil fuels with electro fuels in iron, steel, and cement production. The replacement of fossil fuels in heavy process industries’ combustion processes with electro fuels (plasma torch, hydrogen) is considered a potentially attractive approach in Sweden due to the large amount of renewable electricity production from hydro and wind power. The necessity to reduce the CO 2 emissions, together with the depletion of fossil fuels, has forced the developers of high-temperature energy conversion equipment to look for alternative fuels and new (or moderated) technologies.
Based on comparison with conventional measurement methods, the accuracy of the developed sensor was within 15% for NO and about 40 K for T, clearly showing the potential for fast in situ diagnostics in hot process gases. The fitting of an experimental spectrum representing the convolution of the instrument line function of the spectrometer with the molecular spectra was performed using the pre-calculated library spectra. To reduce the computational time, a library of the molecular spectra calculated at different temperatures was created. The fitting was made using the well-known NO molecular constants of the A 2Σ + − X 2 Π 2 electronic system. Due to excitation of molecular vibration, the shape of the selected NO feature, including (0, 0), (1, 1), and (2, 2) vibrational transitions of the A 2Σ + − X 2 Π 2 electronic system had a strong temperature sensitivity at temperatures above 800 K. H 2, NH 3) or plasma torches as heat source. The sensor was intended for process control in future low-carbon footprint heavy process industries using renewable powered electro fuels (e.g. A new fast sensor for simultaneous high temperature diagnostics (above 800 K) of nitrogen oxide (NO) concentration and gas temperature ( T) was developed based on the spectral fitting of low-resolution NO UV absorption near 226 nm.
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