Formation and Reduction of NO from the Combustion of the Fuels Used in the Sintering Process of Iron Ore in the Presence of Additives

Abstract

Iron and steel companies account for more than 10% of global emissions of NO. The iron ore sintering process represents more than 40% of the total emission of NO. At present, there is no economical and effective method of inhibiting NO emissions from sintering flue gas. Therefore, controlling the conditions of fuel combustion is highly required for the reduction of NO. The current research investigated the effects of adding different materials to anthracite coal and coke on the formation of NO. The addition of CaO and FeO decreased the conversion of nitrogen to NO during coke combustion. CaO was found to play a significant role in both the formation and reduction of NO. However, its was less effective in the case of coke, which suggested replacing anthracite coal with coke in the sintering process to decrease NO emission. Two mixing procedures of fuel and BOF slag were adopted with increasing BOF slag. NO was reduced in the combustion of fuels prepared by both uniform distribution and coating using BOF slag. In the uniform distributed sample, the highest addition of BOF slag (20?wt%) provided the highest NO reduction. In BOF slag-coating fuel, the slightest addition of BOF slag (5?wt%) provided the highest reduction of NO. The difference in each mixing procedure's combustion characteristics is the key to the proposed reduction mechanism of NO. As the amount of BOF slag increased in uniform distribution, more catalysts were available to reduce the NO formed. In the coated sample, two factors were considered: temperature and additional amount. With increasing temperature, the BOF slag started to melt and exposed the fuel surface to react with O2, resulting in a higher formation of NO. Based on that, 1000?��C was defined to be a suitable temperature for the coated sample. Besides, CaO and iron oxides work as catalysts for the formation of NO at 1000?��C; minor addition of BOF slag is advantageous. Graphical Abstract: The addition of BOF slag to fuel was done by two different mixing procedures; uniform distribution and coated fuel. Three additional amounts of BOF slag were used; 5, 10, and 20?wt%. Both mixing methods decreased the conversion of nitrogen to NO (XNO) above 1000?��C when compared to the fuel baseline. In the case of a uniformly distributed sample, the highest additional amount (20?wt%) promoted the highest reduction ratio, while in the coated sample, the lowest (5?wt%). The diagram expressed the XNO for the different layouts combusted at 1000?��C. [Figure not available: see fulltext.]. ? 2021, The Minerals, Metals & Materials Society.