Results demonstrating techniques for enhancing electrochemical reactions involving iron oxide in slags and C in liquid i
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I. INTRODUCTION
ANNUAL world production of crude steel is approximately 800 million metric tons.[1] Smelting and refining of iron and steel consume large amounts of energy and produce significant quantities of solid wastes and greenhouse gases. Globally, it is one of the most energy-intensive industries. During the production of one metric ton of steel, typically 24 GJ of energy is consumed,[2] and 50 to 200 kg of slag[3] and 2 metric tons of greenhouse gases are produced.[4] The total amount of slag produced and discarded worldwide as a result of steelmaking is very large, approximately 10 million metric tons annually in the United States alone.[2] This slag cannot be reused extensively in the steelmaking furnace, as it causes the level of impurities to rise.[5] Also, in most processes, steelmaking slag is not passed on to the ladle, since this decreases the efficiency of deoxidizers used in the ladle.[3] Due to their high lime and ferrous oxide content, steelmaking slags tend to be unstable and require additional processing before they can be recycled as construction fill materials. The iron units contained in discarded slag as iron oxides also represent a source of yield loss for steelmaking processes. Discarded basic oxygen steelmaking slags containing 20 to 25 wt pct iron,[2] can represent a yield loss of 40 to 50 kg per ton of metal produced. The iron oxide content of electric furnace steelmaking slags varies widely depending on the particular operation; however, iron loss to the slag generally accounts for a yield loss of 10 to 35 kg per ton of metal produced. This work is aimed at developing methods UDAY B. PAL, Professor, is with the Department of Manufacturing Engineering, Boston University, Boston, MA 02446. Contact e-mail: [email protected] SCOTT A. MacDONALD, Engineer, is with Ibis Technology, Danvers, MA 01923. DAVID W. WOOLLEY, Research Associate, is with Saint-Gobain Ceramics & Plastics Inc., Northboro, MA 01532. ADAM C. POWELL, Assistant Professor, is with the Department of Materials Science and Engineering, MIT, Cambridge, MA 02139. Manuscript submitted October 31, 2002. METALLURGICAL AND MATERIALS TRANSACTIONS B
for enhancing the rate and extent of reaction involving iron oxide in slag and carbon in liquid iron. Either applied to existing technologies or integrated into an entirely new process, the techniques described in this article can be used to reduce the iron oxide content and the total amount of slag that is discarded. The kinetics of the slag-metal reaction between FeO dissolved in slag and carbon in liquid iron were studied. This reaction removes carbon from the liquid iron, and reduces the iron oxide content in the slag. Increasing the rate of this reaction and similar slag-metal reactions will increase the yield of iron and alloying elements, improve the efficiency of deoxidizers, and decrease refining time and waste generation. Improved understanding and control of the rate of such slag-metal reactions may allow for greater flexibility in raw-material and fuel options and improve process
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