Natural gas as a relatively clean substitute for coal in the MIDREX process for producing direct reduced iron

Abstract

Since in steel production Direct Reduced Iron (DRI) is the main furnace feed, especially for Electric Arc Furnaces (EAFs), its production is among the concerns of the steel industry. The reduction process, which involves converting iron oxide into DRI using reducing gases, has garnered significant attention in recent years, primarily due to its substantial pollution potential and environmental footprint. The current study delves into the environmental impacts of DRI production using natural gas and the Midrex method within a candidate steel facility located in Iran, with the goal of understanding the hotspots within the factory. The processes and major factors influencing the environmental effects of DRI production have been determined. In addition, the environmental effects of producing DRI using coal have been investigated, and a thorough comparison is made between the two methods. For this purpose, the SimaPro software was used, along with the Ecoinvent database and the IMPACT2002+ evaluation method. The required data for analysis was acquired from the mean performance of plants in a period of one year, and the functional unit was chosen as one ton of produced DRI (also known as Sponge Iron). According to the results, non-renewable energy consumption, respiratory inorganics emissions, and global warming impact ranked as the most significant issues, respectively, making up 87.5 % of the total environmental effects. Among the processes, DRI production had the greatest effect (62.8 %), followed by iron oxide production with a contribution of 37.8 %. While this study does not consider the impact of output waste streams, elaboration on the results suggested potential improvements for greener production, including fuel and material replacement, and process optimization.