Abstract
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. The sensor was intended for process control in future low-carbon footprint heavy process industries using renewable powered electro fuels (e.g. H2, NH3) or plasma torches as heat source. 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 A2Σ+ − X2Π2 electronic system had a strong temperature sensitivity at temperatures above 800 K. The fitting was made using the well-known NO molecular constants of the A2Σ+ − X2Π2 electronic system. To reduce the computational time, a library of the molecular spectra calculated at different temperatures was created. 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. 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.
Highlights
The necessity to reduce the CO2 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 technologies
We report the development of an online in situ UV absorption sensor for simultaneous diagnostics of nitrogen oxide (NO) concentration and temperature in hot process gases (T > 800 K)
The left and right sides of the equation equaled each other at an NO concentration of 2485 ppm which is within a few percent from NO concentration in the N2/NO mixture
Summary
The necessity to reduce the CO2 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. 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. In the hydrogen break through iron making technology (HYBRIT) initiative (http://www.hybritdevelopment.com/) and the CemZero project (https://energyindustryreview.com/construction/), the focus is to replace fossil fuels with electro fuels in iron, steel, and cement production. The electro fuels might be Considering 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. 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)
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