Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-03-15
2001-03-06
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S501000, C075S502000, C075S561000, C075S567000, C420S029000, C420S031000
Reexamination Certificate
active
06197088
ABSTRACT:
BACKGROUND OF THE INVENTION
In the smelting and production of liquid iron, the ironmaking system normally consists of iron oxide and a carbonaceous fuel processed by hot air or oxygen blowing at elevated temperatures. The carbon from the fuel forms carbon monoxide (CO) which serves as the reductant for the iron oxide. In addition, the carbonaceous fuel supplies elemental carbon with is soluble in the liquid iron and is commonly the source of sulfur in the reduction system. This sulfur, during ironmaking, is generally in the gaseous form of hydrogen sulfide (H
2
S) with minor amounts of carbonyl sulfide (COS). These gaseous forms of sulfur are highly soluble in the liquid iron. At ironmaking temperatures of 1500° C., up to 36.5% of the sulfur by weight is soluble in the liquid iron with a series of liquid solutions from pure iron to a composition higher in sulfur than iron sulfide (FeS). In these compositions of iron sulfide there is a eutectic composition at 31% sulfur having a melting temperature of 988° C. Therefore throughout the smelting process, conducted above the eutectic temperature level, hot metallic or liquid iron has a high affinity for and is a strong absorber of gaseous sulfur.
Any appreciable level of sulfur in the liquid iron typically destroys the malleable metallic properties of the solidified iron for subsequent forming and utilization. In fact, a sulfur content of as little as 0.1% in the liquid iron can ruin the iron for subsequent refining, casting and steelmaking. With high gaseous sulfur concentrations emanating from the carbonaceous fuel in the liquid iron-reducing gas system, the sulfur content of the iron can easily exceed the 0.1% sulfur limit, and are often found to exceed 1.0% in the liquid iron.
Without control of sulfur in the liquid iron, high concentrations of sulfur in the reducing gases cannot be tolerated, thus limiting the ironmaking process to low sulfur iron ores and low sulfur fuels. Therefore what is needed is a method of maintaining the desired low sulfur levels in the liquid iron even in the presence of high sulfur gases, thereby enabling the production of liquid iron utilizing high sulfur carbonaceous fuels (i.e., petroleum coke, low ash high sulfur coals). The present invention provides such a method.
SUMMARY OF THE INVENTION
In accordance with the invention, it has been found that by adhering to specific smelting parameters, the sulfur in the liquid iron can be controlled and a low sulfur liquid iron can be produced in which the sulfur content is less than 0.1% and is preferably less than or equal to 0.02%. The low sulfur content is achieved even in the presence of high sulfur concentrations in the reducing gases and without the introduction of lime or limestone.
According to one aspect of the invention, liquid iron in the fusion zone of a smelting system is saturated with carbon, thereby desulfurizing the liquid iron without adding lime or limestone to the fusion zone. The carbon saturation level is at least 4.5% carbon by weight. At 4.5%, carbon is highly soluble in liquid iron and a low melting eutectic of ferrite and iron carbide (Fe
3
C-cementite) is formed at 1130° C. The high carbon levels in the iron reject the sulfur dissolved in the liquid iron and maintain a satisfactory low level of sulfur (i.e., less than 0.1%) even in the presence of sulfur rich reducing gases.
According to another aspect of the invention, the desulfurization of the liquid iron can be enhanced by elevating the tapping temperatures to temperatures in excess of 1465° C., and preferably of at least 1490° C. Additionally, the desulfurization process can be supplemented by the presence of significant levels of silicon and/or manganese, both of which are highly soluble in the liquid iron. In a least one embodiment of the invention, the silicon levels in the fusion zone are maintained at greater than 0.3% and preferably greater than 0.5%. Manganese can be substituted for, or used in addition to, the silicon. Preferably the manganese level in the fusion zone is maintained at a level of greater than 0.3% and more preferably greater than 0.5%.
According to another aspect of the invention, in order to achieve sulfur concentrations in the liquid iron of below 0.04%, the combined carbon, silicon, and manganese levels in the liquid iron in the fusion zone are at least 5.0%, and preferably greater than 5.2%. Higher carbon levels and higher combined levels of carbon, silicon, and manganese produce residual sulfur levels in the liquid iron of 0.02% or less. In at least one embodiment, the combined concentration of silicon and manganese is at least 1.0%.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
REFERENCES:
patent: 3850615 (1974-11-01), Reeves
patent: 4070181 (1978-01-01), Widell
patent: 4073642 (1978-02-01), Collin et al.
patent: 4317677 (1982-03-01), Weber et al.
patent: 4389042 (1983-06-01), Wynne
patent: 4396421 (1983-08-01), Stift et al.
patent: 4409023 (1983-10-01), Weber et al.
patent: 4448402 (1984-05-01), Weber et al.
patent: 4504043 (1985-03-01), Yamaoka et al.
patent: 4542889 (1985-09-01), Vuletic
patent: 4543123 (1985-09-01), Vuletic
patent: 4564389 (1986-01-01), Yamaoka et al.
patent: 4566904 (1986-01-01), von Bogdandy et al.
patent: 4588437 (1986-05-01), Kepplinger et al.
patent: 4605205 (1986-08-01), Langner et al.
patent: 4673432 (1987-06-01), Hauk
patent: 4708736 (1987-11-01), Hauk et al.
patent: 4725308 (1988-02-01), Kepplinger
patent: 4728360 (1988-03-01), Hauk et al.
patent: 4755219 (1988-07-01), Hauk
patent: 4784689 (1988-11-01), Vuletic
patent: 4793855 (1988-12-01), Hauk
patent: 4793857 (1988-12-01), Vuletic
patent: 4805880 (1989-02-01), Hauk et al.
patent: 4806154 (1989-02-01), Hauk
patent: 4806158 (1989-02-01), Hirsch et al.
patent: 4822411 (1989-04-01), Standler et al.
patent: 4846449 (1989-07-01), Hauk et al.
patent: 4849015 (1989-07-01), Fassbinder et al.
patent: 4850574 (1989-07-01), Vuletic
patent: 4854967 (1989-08-01), Hauk
patent: 4857284 (1989-08-01), Hauk
patent: 4861369 (1989-08-01), von Bogdandy et al.
patent: 4865626 (1989-09-01), Papst et al.
patent: 4874427 (1989-10-01), Hamada et al.
patent: 4878943 (1989-11-01), Kepplinger
patent: 4889323 (1989-12-01), Pusch et al.
patent: 4891062 (1990-01-01), Vuletic
patent: 4895593 (1990-01-01), Sulzbacher et al.
patent: 4897179 (1990-01-01), Mori et al.
patent: 4898366 (1990-02-01), Vuletic
patent: 4913733 (1990-04-01), Hauk
patent: 4946498 (1990-08-01), Weber
patent: 4955587 (1990-09-01), Sulzbacher
patent: 4957545 (1990-09-01), Hikosaka et al.
patent: 4958808 (1990-09-01), Hauk
patent: 4978387 (1990-12-01), Kepplinger
patent: 5043011 (1991-08-01), Hauk
patent: 5259864 (1993-11-01), Greenwalt
patent: 5259865 (1993-11-01), Greenwalt
patent: 5320676 (1994-06-01), Greenwalt
patent: 5338336 (1994-08-01), Greenwalt
patent: 5354356 (1994-10-01), Greenwalt
patent: 5380352 (1995-01-01), Greenwalt
patent: 5397376 (1995-03-01), Greenwalt
patent: 5413662 (1995-05-01), Greenwalt
patent: 5470375 (1995-11-01), Greenwalt
patent: 5558696 (1996-09-01), Greenwalt
patent: 5630862 (1997-05-01), Greenwalt
patent: 468950 A2 (1991-01-01), None
Fleichtner, et al., “The Corex Process,” Skillings' Mining Review, pp. 20-27 (Jan. 14, 1989).
Lemperle, et al., “Co-Generation with Corex®,” Presented During 1991 AISE Annual Convention, Pittsburgh, Pennsylvania (Sep. 1991).
COREX° Brochure—Hot News From COREX°, No. 2 (Sep. 1991).
Andrews Melvyn
Bechtel Group Inc.
Townsend and Townsend / and Crew LLP
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