Method for producing liquid pig iron from a DRI product

Abstract

A method for producing liquid pig iron comprises: i) providing a DRI product with an iron content of at least 75.0 wt. %, a carbon content of at least 0.10 wt. % and a content of acidic and basic slag components, comprising CaO, SiO.sub.2, MgO and Al.sub.2O.sub.3 of max. 15.0 wt. %; ii) supplying the DRI product, adding slag formers, into an electrically operated smelting unit; iii) optionally supplying further iron and/or carbon components into the electrically operated smelting unit; iv) smelting the DRI product and optionally the further iron and/or carbon components in the presence of the slag formers, so that a liquid pig iron phase and a liquid slag phase are formed; v) adjusting the slag phase such that it has a basicity of (CaO+MgO/SiO.sub.2) from 0.95 to 1.5; vi) tapping the liquid pig iron phase; and vii) tapping and granulating the slag phase.

Claims

1.-21. (canceled)

22. A method for producing liquid pig iron, comprising: i) providing a directly reduced iron product (1) (DRI product) with an iron content of at least 75.0 wt. %, a carbon content of at least 0.10 wt. %, and a content of acidic and basic slag components, selected from the group consisting of CaO, SiO.sub.2, MgO and Al.sub.2O.sub.3, of max. 15.0 wt. %; ii) supplying the DRI product (1) and slag formers (2) into an electrically operated smelting unit (3); iii) optionally supplying further iron and/or carbon components (5) into the electrically operated smelting (3) unit; iv) smelting the DRI product (1) and optionally the further iron and/or carbon components (5) in presence of the slag formers (2), so that a liquid pig iron phase (6) and a liquid slag phase (7) are formed; v) adjusting the slag phase (7) such that it has a basicity of (CaO+MgO/SiO.sub.2) from 0.95 to 1.5; vi) tapping the liquid pig iron phase (6); and vii) tapping and granulating the slag phase (7).

23. The method according to claim 22, wherein the slag phase (7) is adjusted such that it has a basicity of (CaO+MgO/SiO.sub.2) from 1.0 to 1.25.

24. The method according to claim 22, wherein the slag phase (7) is adjusted such that it has a viscosity of 0.30 to 0.50 Pa*s.

25. The method according to claim 22, wherein the slag phase (7) is tapped at a tapping temperature in the range from 1300° C. to 1600° C.

26. The method according to claim 22, wherein the slag formers (2) are selected from the group consisting of CaO, SiO.sub.2, MgO, Al.sub.2O.sub.3, and mixed oxides thereof.

27. The method according to claim 22, wherein the slag formers (2) in accordance with step ii) are supplied up to a fraction of max. 10.0 wt. %, based on an amount of the DRI product.

28. The method according to claim 22, wherein the iron and/or carbon components (5) in accordance with step iii) are supplied up to a fraction of max. 20.0 wt. %, based on an amount of the DRI product.

29. The method according to claim 22, wherein granulation is carried out as wet or dry granulation.

30. The method according to claim 22, wherein supplying the slag formers (2) is carried out automatically via a process model integrated into a plant automation system, and wherein a quantity of the slag formers (2) is calculated by the process model and determined as a function of process parameters.

31. The method according to claim 22, wherein the directly reduced iron product (1) is supplied to the smelting unit (3) in hot form as HDRI product, in cold form as CDRI product, in hot briquette form as HBI product and/or in particulate form with an average particle diameter of max. 10.0 mm.

32. The method according to claim 22, wherein the liquid pig iron phase (6) formed in accordance with step iv) is carburized to a carbon content of at least 2.50 wt. %.

33. The method according to claim 22, wherein the DRI product (1) and/or the slag formers (2) are supplied to the smelting unit (3) from a thermally insulated bunker reservoir (15).

34. The method according to claim 22, wherein the DRI product (1) is produced in a direct reduction plant (11) and is supplied to the smelting unit (3) and/or a bunker reservoir (15) under a protective gas atmosphere via a conveying device (14).

35. A granulated slag obtained by the method according to claim 22, comprising: 35.0-40.0 wt. % SiO.sub.2, 30.0-43.0 wt. % CaO, 8.0-12.0 wt. % Al.sub.2O.sub.3, 4.0-12.0 wt. %- MgO, along with unavoidable impurities comprising iron (Fe), MnO.sub.2 and/or sulfur (S).

36. The granulated slag according to claim 35, wherein a total content of SiO.sub.2, CaO and MgO amounts to at least 70.0 wt. %.

37. The granulated slag according to claim 35, comprising a vitreous solidification fraction of at least 95.0 wt. %, and a total iron content of max. 1.0 wt. %.

38. The granulated slag according to any claim 35, having an eluate allocation value of 0 or 1.

39. A plant (10) for producing liquid pig iron, comprising: a direct reduction plant (11) for producing a directly reduced iron product (1); an electrically operated smelting unit (3) in which the directly reduced iron product (1) can be smelted; and a conveying device (14) via which the directly reduced iron product (1) can be transported from the direct reduction plant (11) to the smelting unit (3).

40. The plant (10) according to claim 39, wherein the smelting unit (3) is an electric arc furnace (EAF), a submerged arc furnace (SAF), or an induction furnace (IF).

41. The plant (10) according to claim 39, wherein the conveying device (14) is a metal conveyor belt with a protective gas atmosphere.

42. The plant (10) according to claim 39, further comprising a thermally insulated bunker reservoir (15).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 shows a schematic view of a flow chart on the basis of which the method for producing liquid pig iron is explained,

[0055] FIG. 2 shows a highly simplified schematic view of a plant in accordance with a first embodiment, and

[0056] FIG. 3 shows a highly simplified schematic view of a plant in accordance with a second embodiment.

DETAILED DESCRIPTION

[0057] In accordance with FIG. 1, the method for producing liquid pig iron is explained in a possible embodiment on the basis of a flow chart.

[0058] For the production of liquid pig iron, a directly reduced iron product 1 (DRI product) is initially provided, which, in the embodiment shown here, has an iron content of 80.0 wt. %, a carbon content of 3.0 wt. % and a content of acidic and basic slag constituents selected from the group comprising CaO, SiO.sub.2, MgO and Al.sub.2O.sub.3 of not more than 12.0 wt. % in total and is present in the form of a hot DRI product with a temperature of approximately 750-800° C.

[0059] For example, the DRI product 1 can be produced as part of a low-CO.sub.2 steelmaking process in a direct reduction plant 11, as shown in FIGS. 2 and 3.

[0060] In the next step, the DRI product 1 is supplied to an electrically operated smelting unit 3, adding slag formers 2. In the embodiment shown in the present case, the slag formers 2 are selected from the group comprising CaO, SiO.sub.2, MgO and Al.sub.2O.sub.3 and are added to the smelting unit 3 in an amount of up to 10.0 wt. %, based on the amount of DRI product supplied. In the present case, the smelting unit 3 is designed in the form of an electric arc furnace (EAF) and comprises at least one electrode 4, such as, for example, a carbon electrode.

[0061] The process shown in FIG. 1 can in principle be carried out with a mass fraction of 100% of the DRI product based on a batch charge. However, in the embodiment shown, further iron and/or carbon components 5 are added to the smelting unit 3 in the form of coal and steel scrap. In the present example, the mass fraction of the iron and carbon components 5 amounts to 20.0 wt. %, based on the amount of DRI product supplied.

[0062] The mixture of DRI product 1, slag former 2, and iron and carbon components 5 is then melted with the aid of electric current, such that a liquid pig iron phase 6 and a liquid slag phase 7 are formed.

[0063] By adding the slag formers 5, the slag phase 7 is adjusted such that, in the embodiment shown here, it has a basicity B3 of (CaO+MgO/SiO.sub.2) from 0.95 to 1.25 along with a viscosity of 0.30 to 0.50 Pa*s. To the extent that such slag parameters are achieved, the slag phase 7 is tapped at a tapping temperature in the range from 1350° C. to 1550° C. and then granulated. In a final step, the liquid pig iron phase 6 is tapped off and supplied, for example, to a converter steel mill for further processing.

[0064] The tapped pig iron phase 6 has the following composition in wt. %: [0065] Carbon content 3.50, [0066] Silicon 0.3, [0067] Manganese 0.50, [0068] Residual iron along with unavoidable impurities of sulfur and phosphorus of max. 0.04 each.

[0069] The tapped slag phase 7 is processed via wet granulation into a granulated slag 8, which has the following composition in wt. %: [0070] SiO.sub.2 45.0, [0071] CaO 40.0 [0072] Al.sub.2O.sub.3 8.0, [0073] MgO 5.0, [0074] along with unavoidable impurities comprising iron, MnO.sub.2 and sulfur (S) a total of less than 2.0.

[0075] The granulated slag is characterized by having a vitreous solidification fraction of 95.0 wt. % and a total iron (Fe) content of less than 1.0 wt. %.

[0076] FIG. 2 shows a highly simplified schematic view of a plant 10 in accordance with a first embodiment.

[0077] The plant 10 for producing liquid pig iron comprises a direct reduction plant 11 for producing the directly reduced iron product 1. The direct reduction plant 11 comprises a first upper part, which forms a reduction shaft 12, and a second lower part, which forms a cooling section 13. Conventional reformer gas based on natural gas, coke gas or other metallurgical gases along with hydrogen-enriched reformer gas with a maximum hydrogen content of up to 100% can be used as the reduction gas. The hydrogen required is advantageously produced from green electricity in a CO.sub.2-neutral manner.

[0078] The DRI product 1 produced in the present direct reduction plant 11 can have a variable carbon content depending on the hydrogen content in the reduction gas. In order to have a pig iron-like analysis, the carbon content can be raised by selective injection of natural gas for cooling purposes in the lower cooling section 13.

[0079] Furthermore, the plant 10 comprises an electrically operated smelting unit 3, in which the directly reduced iron product 1 (DRI product) can be smelted, along with a conveying device 14, via which the directly reduced iron product 1 can be transported from the direct reduction plant 11 to the smelting unit 3.

[0080] In the present case, the smelting unit 3 is designed in the form of an electric arc furnace (EAF).

[0081] The DRI product 1 produced in the direct reduction plant 11 can be supplied directly to the smelting unit 3 via the conveying device 14, which in the present case is designed in the form of a metal conveyor belt and has a protective gas atmosphere, as this is shown based on the dashed line. Preferably, the DRI product 1 is initially supplied via the conveying device 14 to a thermally insulated bunker reservoir 15 under a protective gas atmosphere, from which it is then supplied, preferably automatically, to the smelting unit 3.

[0082] FIG. 3 shows a highly simplified schematic view of the plant 10 in a second embodiment. In contrast to the embodiment shown in FIG. 2, the smelting unit 3 is designed in the form of a submerged arc furnace (SAF). This process is characterized by the presence of a foamed slag phase 16, which surrounds the electrode 4, in the smelting unit 3.

LIST OF REFERENCE SIGNS

[0083] 1 Directly reduced iron product/DRI product

[0084] 2 Slag former

[0085] 3 Smelting unit

[0086] 4 Electrode

[0087] 5 Iron and/or carbon components

[0088] 6 Liquid pig iron phase

[0089] 7 Liquid slag phase

[0090] 8 Granulated slag

[0091] 10 Plant

[0092] 11 Direct reduction plant

[0093] 12 Reduction shaft

[0094] 13 Cooling section

[0095] 14 Conveying device

[0096] 15 Bunker reservoir

[0097] 16 Foam slag