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A Study of Scrap Heating By Burners. Part I: Experiments
KAMALESH MANDAL and GORDON A. IRONS
A furnace, approximately 1 m3 in capacity, was built to measure the eciency of heat transfer from a propane-oxygen burner to dierent types of industrial steel scrap. Supplementary measurements were undertaken to measure the scrap density, size, and void fraction to insure complete combustion of the propane and to measure the extent of scrap oxidation. Local values of temperature in the scrap bed were measured along with the exit temperature of the o gas. The o gas temperature was a direct measurement of the overall eciency of heating. It was found that smaller and denser scrap was heated more eectively. Congurations that increased the path length of the gas also increased the eciency of heating. In Part II, a mathematical model is developed to compare with the measured temperatures.
DOI: 10.1007/s11663-012-9751-2 The Minerals, Metals & Materials Society and ASM International 2012
I. INTRODUCTION
IN developed countries with ample steel scrap, electric arc furnace (EAF) steelmaking has increased rapidly over the basic oxygen furnace (BOF) steelmaking; over the last decade, EAF steelmaking has increased from 49 to 61 pct of total crude steel production in North America.[1] The
performance of EAF units has improved with a number of new technologies. One of these is the use of oxy-fuel burners to assist electrical heating, which has become standard equipment. The rst use of burners was to melt the scrap at the slag door where arc heating is ineective, but it was quickly realized that productivity could be increased by more burner power. Generally, there are at least three burners positioned in the cold spots between electrodes.[2] Using burners, typical productivity increases are in the range of 5 to 20 pct, as reported by dierent investigators.[35]
Despite the importance of burners, there is little information on the eciency of the heat transfer between the combustion gas and the steel scrap in the furnace. Better understanding of heat transfer phenomena between the combustion gas and the steel scrap could improve the process, for example, by determining the time at which the heating eciency drops to uneconomical levels or by determining the best scrap size and density to charge near the burners. The present...