Effect of FeO in the slag and silicon in the metal on the desulfurization of hot metal
- PDF / 381,830 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 47 Downloads / 198 Views
I.
INTRODUCTION
THE desulfurization of hot metal is a vital part of the steelmaking process since sulfur in many steel products is detrimental. In general, desulfurizing hot metal is more economical than desulfurizing steel, and about 90 pct of the metal produced in the iron blast furnace is desulfurized before it is sent to be processed in a steelmaking furnace. A common practice is the injection of a desulfurizing reagent through a lance. During injection, there are two sites at which sulfur is removed from the metal. Sulfur is removed by the reagent particles that are injected and rise in the metal bath and also by the slag that accumulates at the top of the metal. These reaction sites can be studied independently and are referred to as the transitory (rising particles) and the permanent contact (top slag) reactions. It has been shown that when the same amount of slag is either simply added to the top of the metal or injected, the sulfur content of the metal reaches the equilibrium amount at about the same time after the slag is introduced.[1,2] The present study will focus only on the top slag reaction as results obtained from these findings can be used to predict the behavior during the injection desulfurization process. A subsequent publication will utilize the basis of the model presented here to demonstrate the effect of FeO in the slag and silicon in the metal on desulfurization in actual industrial practice. Although hot metal desulfurization is a mature process, the effects of FeO in the slag have never been quantitatively assessed. The FeO present in the desulfurizing unit originates from two main sources. The first source is slag carried over from the iron blast furnace and the second is hot metal oxidized during tapping from the blast furnace and during transportation to the desulfurization station. The presence of FeO in the slag during desulfurization hinders both the thermodynamics and kinetics of the desulfurization process. P.K. IWAMASA, formerly Graduate Student, Department of Materials Science and Engineering, Carnegie Mellon University, is Research Associate, BHP Research, New South Wales 2287, Australia. R.J. FRUEHAN, Professor, is with the Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213. Manuscript submitted October 5, 1995. METALLURGICAL AND MATERIALS TRANSACTIONS B
This can be demonstrated in the definition of the sulfur partition ratio, LS, a measure of the thermodynamic ability of a slag to contain sulfur.[3] LS 5
(pct S) fC 5 S S [pct S] hOK2
[1]
where (pct S) 5 weight percent of sulfur in the slag; [pct S] 5 weight percent of sulfur in the metal; fS 5 activity coefficient of sulfur in metal relative to the 1 wt pct standard state; CS 5 sulfide capacity of the slag (as defined by Richardson and Withers[5]); hO 5 Oxygen potential of the system; and K2 5 equilibrium constant for the slag and gas equilibrium: 1 1 S2 (g) 1 O 5 O2 (g) 1 S 2 2
[2]
FeO in the slag effects the sulfur partition ratio by controlling the oxygen potential at
Data Loading...
