EP-4735649-A1 - DIRECT REDUCED IRON PROCESSING

Abstract

A method and an apparatus for treating a hydrogen-reduced DRI that contains phosphorous in an induction furnace is disclosed. The method includes treating molten DRI by at least partially partitioning phosphorus in the DRI into a slag, with the molten DRI becoming an iron feedstock which is at least substantially alpha iron and has a lower phosphorus concentration, typically 0.03% or less by weight, that is suitable for use as a direct feed material for making steel, such as in an existing steelmaking apparatus, such as an EAF.

Inventors

• EVANS, TIMOTHY, JAMES

Assignees

• Technological Resources PTY. Limited

Dates

Publication Date

20260506

Application Date

20240726

Claims (20)

1. 1. A method for producing an iron feedstock having a phosphorous concentration suitable for directly forming steel in a steelmaking apparatus, typically of less than 0.03% by weight, from a hydrogen-reduced DRI having a higher phosphorous concentration using an electric induction furnace includes: (a) feeding a hydrogen-reduced feed DRI into a chamber in an induction furnace; (b) operating the induction furnace and melting the DRI via a magnetic field induced in the chamber and forming a molten DRI-containing bath; (c) forming a basic slag in the chamber that at least partially partitions phosphorus in molten DRI to the slag, with the molten DRI becoming a molten iron feedstock which is at least substantially alpha iron with a phosphorous concentration suitable for directly forming steel in the steelmaking apparatus, typically 0.03% or less by weight from the molten DRI; (d) removing, for example by tapping or raking, at least a part of the slag from the furnace; and (e) removing, for example by tapping, at least a part of the iron feedstock from the furnace at the same time or other times as removing the slag from the furnace.
2. 2. The method defined in claim 1 includes initially selecting and then controlling a slag composition during the method to be any suitable composition to facilitate partitioning phosphorus in the molten DRI to the slag.
3. 3. The method defined in claim 1 or claim 2 includes controlling a slag composition during the method to have a FeO concentration in a range of 5-20% by weight.
4. 4. The method defined in claim 3 includes controlling a slag composition during the method to have a FeO concentration below 10% by weight.
5. 5. The method defined in any one of the preceding claims includes controlling a slag composition during the method to have a CaO to SiO2 ratio of < 2.0.
6. 6. The method defined in any one of the preceding claims includes controlling a slag composition during the method to have a MgO to AI2O3 ratio of 0.4-0.6.
7. 7. The method defined in any one of the preceding claims includes maintaining a slag composition that comprises 5% by weight FeO, a CaO to SiCh ratio of 1.5, and a MgO to AI2O3 ratio of 0.5.
8. 8. The method defined in any one of the preceding claims includes maintaining the molten bath at a temperature of 1540°C.
9. 9. The method defined in any one of the preceding claims includes forming the molten bath at a temperature up to 20°C above a liquidus temperature of the alpha iron.
10. 10. The method defined in any one of the preceding claims includes forming the molten bath at a temperature up to 30°C above a liquidus temperature of the alpha iron.
11. 11. The method defined in any one of the preceding claims includes forming the molten bath at a temperature no more than 90°C above a liquidus temperature of the alpha iron.
12. 12. The method defined in any one of the preceding claims includes forming the molten bath at a temperature no more than 80°C above a liquidus temperature of the alpha iron.
13. 13. The method defined in any one of the preceding claims includes controlling the method so that at least 2/3 of the phosphorous in the feed DRI partitions to the slag.
14. 14. The method defined in any one of the preceding claims includes supplying the feed DRI to the furnace in a hot state at a temperature of at least at 400°C.
15. 15. The method defined in any one of the preceding claims includes supplying the feed DRI to the furnace as at least 97% metallised DRI.
16. 16. The method defined in any one of the preceding claims includes operating on a batch basis, with successive batches of the molten iron feedstock being formed in the method.
17. 17. The method defined in claim 16 includes forming a heel of molten iron feedstock in the furnace and then carrying out steps (a) to (e).
18. 18. The method defined in any one of the preceding claims includes removing the molten slag and the molten iron feedstock periodically after forming a full melt in the furnace.
19. 19. The method defined in any one of claims 1 to 17 includes removing the molten slag periodically before forming a full melt in the furnace to maintain the remaining slag in the furnace with desired properties and to ensure it remains fluid for tapping the slag.
20. 20. The method defined in any one of the preceding claims includes supplying the DRI into the furnace in a gradual manner, along with any required slag forming materials, and melting the DRI requiring bath temperatures well in excess of the liquidus temperature of the alpha iron.

Description

DIRECT REDUCED IRON PROCESSING TECHNICAL FIELD The invention relates to a method and an apparatus for processing hydrogen-reduced direct reduced iron (DRI) that contains phosphorous, for example in the form of phosphorus oxide(s), into a low phosphorus iron feedstock for steel production purposes. The invention relates particularly, although by no means exclusively, to a method and an apparatus for processing, for example batch processing, hydrogen-reduced direct reduced iron that contains phosphorous, for example in the form of phosphorus oxide(s) (as a residual after the DRI metallisation process), using an induction melting furnace that enables the processing of such DRI to produce an iron feedstock suitable for use in an existing steelmaking apparatus. Such an iron feedstock, for example while in a molten state, may be subsequently directly delivered to a steelmaking furnace or a metal refining station or other steelmaking apparatus as hot metal feed for conversion into steel of a desired grade, or alternatively cast into a solid iron feedstock for subsequent supply as a ‘cold’ iron feedstock to a separate or remote steelmaking apparatus. The term “steelmaking apparatus” as used herein describes facilities having fumace(s) for the production of steel such as (without being limited thereto) the following furnaces. a) Furnaces in which a bath of molten iron-containing carbon, as described herein, is fed and refined to steel by bulk oxidation of molten iron to FeO by oxygen injection into the molten bath, with back reaction reduction of FeO back to Fe by the conversion of carbon in the molten bath, thereby producing CO and ultimately producing a desired steel having a specified carbon content. Such furnaces typically are a basic oxygen furnace (BOF), also known as a LD converter (named after the Austrian town of Linz and district of Donawitz). Such furnaces are able to take about 20-30% of the metallic iron input as cold iron feedstock. b) Furnaces in which a predominantly ‘cold’ metallic iron input is melted using an electric arc to form a bath of steel, with the carbon concentration of the steel being adjusted to a required concentration once the molten bath is fully created in the furnace. Such a furnace typically is an electric arc furnace (EAF). These furnaces are usually fed with a majority of solid steel scrap, with a purer metallic iron component added as necessary to dilute any undesirable tramp elements arising from the source of scrap, such as tin and copper that cannot be removed in the steel making process. Such furnaces can use iron feedstock as the prime metallic iron input as an alternative to steel scrap. EAFs are used in some situations with ladle refining furnaces that make it possible to divide the steel melting operations, carried out in the EAFs, from those of treatment and refining to a final steel composition. The liquid steel produced by the EAF is poured into a ladle, which serves as a reactor for metallurgical operations at the treatment stations. The term “steel” is understood herein to mean an alloy of iron and carbon in which the amount of carbon is more than 0.008% and less than 2.06% by weight. While the term “steel” applies to alloys of iron and carbon in which the amount of carbon can be up to 2.06% by weight, normal grades of steel that are commercially produced rarely exceed 0.8% carbon. It is also to be noted that other alloying elements may be present, including by purposeful addition to produce steels for special purposes, e.g., like manganese spring steels. The term “iron-containing carbon” is understood herein to mean an alloy of iron and carbon in which the amount of carbon is 2.06% or greater by weight and less than 4.3% by weight in total. Such iron may have significant amounts of other elements within it as a function of the reduction/ smelting process that has led to the production of such iron. The term ‘alpha’ iron is understood herein to mean iron having 0.008% or less carbon by weight at room temperature and comprising a solid solution of carbon in pure iron. Such iron may have other trace elements as a function of the reduction process that has led to the production of such iron. The term “iron feedstock” is understood herein to mean ‘alpha’ iron as well as steel and in both cases is not limited by physical state, i.e., it may be liquid or solid. The term “hydrogen-reduced direct reduced iron” is understood herein to mean iron material produced from the reduction of iron ore by a hydrogen rich reducing agent(s) at temperatures below the bulk melting temperature of the solids having over 95% metallisation of iron within it. The term “hydrogen rich reducing agent(s)” is understood herein to mean a gas in which the reducing agent(s) comprises 90% or more hydrogen as the element that combines with oxygen from iron oxides in the iron ore. Such hydrogen will usually be in a form of H2 but does not exclude the use of a synthetic gas formed for example from N