ReuseThis article is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND) licence. This licence only allows you to download this work and share it with others as long as you credit the authors, but you can't change the article in any way or use it commercially. More information and the full terms of the licence here: https://creativecommons.org/licenses/ Selective non-catalytic reduction -Fe-based additive 1 hybrid technology 2 Syed Sheraz Daood*, Thomas S. Yelland, William Nimmo 3 Energy Engineering Group, Energy 2050, Department of Mechanical Engineering, University of 4 Sheffield, Sheffield, S10 2TN, UK. 5 HIGHLIGHTS 6  A Fe-based additive altered performance of selective non-catalytic reduction. 7  Pseudo-catalytic activity provides active sites for ammonia to reduce NO. 8  This interaction led to greater NO reduction and greater ammonia utilisation. 9  This is an economically viable opportunity for full-scale coal combustion plants. 10 ABSTRACT 11Fe-based additives can be used to improve coal combustion and reduce NO x emissions; further to 12 this, iron oxide (Fe 2 O 3 ) has been found to interact with ammonia. Therefore, it is critically 13 imperative to understand and assess the impact of the Fe-based additive on the use of ammonia 14 based selective non-catalytic reduction (SNCR) and to evaluate the economic feasibility of such 15 a combination for full-scale use. Experiments were performed using a 100 kWth down fired-16 combustion test facility burning pulverised coal over three Fe-based additive concentrations, 17 2 while the ammonia input was varied between normalised stoichiometric ratios 0-3. This study 18 finds evidence of an interaction between the Fe-based additive and SNCR. The interaction leads 19 to greater ammonia utilisation and an increased NO x reduction due to the SNCR of >10%. The 20 interaction is theorised to be pseudo-catalytic with the fuel additive providing an active site for 21 ammonia to reduce NO. Using Carnegie Mellon University's 'Integrated Environmental Control 22Model' (IECM), this has been shown to create an economically viable opportunity to increase 23 SNCR effectiveness. 24 KEYWORDS 25 SNCR, NOx, coal, additive, ammonia, Fe 26 NOMENCLATURE 27 AFR -Ammonia flow rate (ml/min) 28 NH 3 -Ammonia utilisation efficiency 29 NO initial -The concentration of NO in the flue gas prior to ammonia injection (ppm) 30 NSR -Normalised stoichiometric ratio 31 Q -Volumetric flow rate of air (ml/min) 32

This study presents an investigation into the impact of varied burner staging environments on an oxy-fuel flame and the rate of the NO formation and destruction processes. The experimental data was extracted from the use of a 250 kWth down-fired combustion test facility with a scaled-down model of an industrial low-NOx burner (LNB). Two oxy-coal combustion regimes were investigated by varying a fixed flow of oxidant between the secondary and tertiary registers, so as to impact the stoichiometry in the fuel-rich region and flame structure, and using various NO recycling regimes, to test the impact of these different burner configurations on NO reburning. The data was collected by monitoring key emissions in the flue gas and in the flame, as well as temperatures throughout the furnace and the unburned carbon content of the ash. A detailed investigation encompassing the impact of secondary oxidant proportion for different oxidants on NO emissions, together with the quantification of recycled NO destruction, is discussed. This investigation finds that 85 % to 2 95 % of the recycled NO is destroyed at a range of burner configurations using OF 27 and OF 30 at 170 kWth. In addition to this, NO formation and carbon burnout are found to be significantly affected with changing burner configurations. Further to this, OF 30 flames appear to be more sensitive to burner configuration than OF 27 flames with regards to both NO formation and destruction, possibly due to the decreased density of the OF 30 oxidant. Radial profiles of two burner configurations at OF 27 and OF 30, as well as an axial profile of two burner configurations at OF 30, are analysed. The profiles appear to show that burner staging aids in controlling the products of NO reburning, hence maximising the destruction of recycled NO.

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