Numerical Analysis of Slag Transfer in the IronArc Process
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ron and steel is integral to modern society, but is also a significant contributor to the global production of CO2 : The steelmaking business accounts for 7 to 9 pct of the direct annual emissions from use of fossil fuel, a majority of which come from the blast furnace.[1] This is not sustainable and must be addressed if steel is to have a future in society. The emissions from the steelmaking process must be reduced without compromising the quality of the steel or the production capacity. Many novel processes utilizing natural gas or hydrogen for reduction have been proposed as alternatives to the blast furnace process and are currently being developed, but their indistrial use is still limited.[1, 2] JONAS L. SVANTESSON, MIKAEL ERSSON, and PA¨R G. JO¨NSSON are with the KTH Royal Insitute of Technology, Brinellva¨gen 23, Stockholm, Sweden. Contact e-mail: [email protected] MATEJ IMRIS is with ScanArc Plasma Technologies AB, Va¨rnava¨gen 11, Hofors, Sweden. Manuscript submitted February 3, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
The reduction of iron oxide to liquid iron requires energy and a reduction agent to remove the chemically bound oxygen from the iron oxide. Energy is required to heat the material to the reaction temperature as well as to supply the heat consumed by the endothermic reactions associated with reduction. Traditionally, a significant part of the energy is supplied as heat from the combustion of coke, as done in the blast furnace. To reduce the emissions of the blast furnace, this heat can instead be supplied by electric energy from electric arcs or heated gases. If the electricity used for heating is produced in a renewable way the total emissions of the process would be reduced. This is the inspiration for the development of the IronArc process. By utilizing electric arcs to superheat gas in a plasma generator (PG), energy can be supplied to metallurgical processes without using combustion of coke or hydrocarbons. If this is combined with the addition of hydrocarbons from liquid natural gas (LNG) or liquid petroleum gas (LPG), the reduction of iron ore can be done with significantly lower CO2 emissions. Previous studies of this process by Bo¨lke et al. by use of computational fluid dynamics simulations (CFD) and water-modeling found promising results.[3]
Currently, there exists a functioning pilot size plant of the IronArc process. However, to further prove the functionality of the process, a larger demonstration-scale reactor is planned. The demonstration-scale plant will feature a two-reactor approach to facilitate a continuous process. The first reactor is a melting reactor where iron ore will be added and heated using several PGs. In this reactor, hydrocarbons are added to reduce the Fe2 O3 and Fe3 O4 to FeO. Some gangue elements are also expected, which in combination with the remaining FeO will form a slag consisting of approximately 90 pct FeO, 5 pct SiO2 ; and 5 pct CaO. This slag is then transferred to the second reactor where the final reduction takes place with the addition of carbo
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