METHOD FOR PRODUCING LIQUID PIG IRON

Abstract

A method for producing liquid pig iron (1), includes reducing iron-oxide-containing feed materials (2) to form a partially reduced first iron product (3) in a first reduction system (4), introducing the partially reduced first iron product (3), a first oxygen-containing gas (9, 9a), and a first carbon carrier (10) into a melter gasifier (11), introducing a second gaseous and/or liquid carbon carrier (13) and a second oxygen-containing gas (9b) into a mixing region (18) within the melter gasifier (11) above the fixed bed of the melter gasifier, mixing the second gaseous and/or liquid carbon carrier (13) with the second oxygen-containing gas (9b) in the mixing region (18), wherein the combustion air ratio is set in the range of 0.2 to 0.4, preferably between 0.3 and 0.35, in order to achieve partial oxidation of the second gaseous or liquid carbon carrier (13) within the mixing region (18), and mixing the gas resulting from the partial oxidation from the mixing region (18) with the gas in the remaining volume within the melter gasifier (11).

Claims

1. A method for producing liquid pig iron, comprising: reducing iron-oxide-containing feed materials to form a partially reduced first iron product in a first reduction system by means of a reducing gas; drawing off the reducing gas consumed in the reduction as top gas or offgas; introducing the partially reduced first iron product, a first oxygen-containing gas and a first carbon carrier into a melter gasifier; gasifying the carbon carriers with the oxygen-containing gas and melting the partially reduced first iron product to form the liquid pig iron while producing the reducing gas in the melter gasifier; introducing at least a partial amount of the reducing gas into the first reduction system by means of a reducing gas line, introducing a second gaseous and/or liquid carbon carrier and also a second oxygen-containing gas into a mixing region within the melter gasifier above the fixed bed thereof; mixing the second gaseous and/or liquid carbon carrier with the second oxygen-containing gas in the mixing region, the combustion air ratio being set in the range of 0.2 to 0.45, to achieve partial oxidation of the second gaseous or liquid carbon carrier within the mixing region; and mixing the gas resulting from the partial oxidation from the mixing region with the gas in the remaining volume within the melter gasifier.

2. The method as claimed in claim 1, further comprising the second oxygen-containing gas is oxygen of technical purity with an O.sub.2 content of at least 90%.

3. The method as claimed in claim 1, wherein the mixing of the second gaseous and/or liquid carbon carrier with the second oxygen-containing gas takes place only by the pressure and direction of the second gaseous and/or liquid carbon carrier and the second oxygen-containing gas when they are introduced.

4. The method as claimed in claim 1, further comprising the mixing of the gas resulting from the partial oxidation from the mixing region with the gas in the remaining volume within the melter gasifier takes place only by the pressure and direction when the second carbon carrier and the second oxygen-containing gas are introduced.

5. The method as claimed in claim 1, further comprising the mixing region is at least partially surrounded by the reducing gas that is in the melter gasifier.

6. The method as claimed in claim 1, further comprising the mixing region is at least partially spatially separate from the remaining volume within the melter gasifier.

7. The method as claimed in claim 1, further comprising the mixing region is at least partially formed by an outwardly directed protrusion of the inner wall of the melter gasifier.

8. The method as claimed in claim 1, further comprising the mixing region is above the fixed bed of the melter gasifier and is in a temperature range of 1000-1100? C.

9. The method as claimed in claim 1, further comprising at least one mixing region is 1-2 m above the fixed bed of the melter gasifier.

10. The method as claimed in claim 1, further comprising, for use when a gaseous second carbon carrier, more than 100 m.sup.3 of the second carbon carrier are fed to the melter gasifier per ton of pig iron.

11. The method as claimed in claim 1, wherein the top gas or offgas is at least partially introduced into a second reduction system, which is formed as a direct reduction shaft or as a fluidized bed and in which further iron-oxide-containing feed materials are reduced to form a partially reduced second iron product.

12. A melter gasifier for carrying out the method as claimed in claim 1, comprising: a melter gasifier; an iron product feed line for introducing the partially reduced first iron product; a media feed line for introducing a first oxygen-containing gas and a feed line for introducing a first carbon carrier into the melter gasifier; at least one carbon carrier line for introducing a second gaseous and/or liquid carbon carrier; at least one media feed line for introducing a second oxygen-containing gas into a mixing region within the melter gasifier and above a fixed bed of the melter gasifier, the mixing region being at least partially formed by an outwardly directed protrusion of the inner wall of the melter gasifier.

13. The melter gasifier as claimed in claim 12, further comprising: the melter gasifier has a dome and a conical region adjoining the dome; and the protrusion is within 50-100%, of the height of the conical region.

14. The melter gasifier as claimed in claim 13, wherein a lower part of the dome is formed as a cylindrical region, and the protrusion is within the cylindrical region.

15. A method for producing liquid pig iron, comprising: reducing iron-oxide-containing feed materials to form a partially reduced first iron product in a first reduction system by means of a reducing gas; drawing off the reducing gas consumed in the reduction as top gas or offgas, introducing the partially reduced first iron product, a first oxygen-containing gas and a first carbon carrier into a melter gasifier; gasifying the carbon carriers with the oxygen-containing gas and melting the partially reduced first iron product to form the liquid pig iron while producing the reducing gas in the melter gasifier; introducing at least a partial amount of the reducing gas into the first reduction system by means of a reducing gas line; introducing a second gaseous and/or liquid carbon carrier and also a second oxygen-containing gas into a mixing region within the melter gasifier above the fixed bed thereof; mixing the second gaseous and/or liquid carbon carrier with the second oxygen-containing gas in the mixing region, the combustion air ratio being set in the range of 0.3 to 0.35, to achieve partial oxidation of the second gaseous or liquid carbon carrier within the mixing region; and mixing the gas resulting from the partial oxidation from the mixing region with the gas in the remaining volume within the melter gasifier.

16. The method as claimed in claim 1, further comprising the mixing region is above the fixed bed of the melter gasifier and is in a temperature range of around 1050? C.

17. The method as claimed in claim 1, wherein the top gas or offgas is at least partially introduced into a second reduction system, which is formed as a direct reduction shaft or as a fluidized bed and in which further iron-oxide-containing feed materials are reduced to form a partially reduced iron sponge.

18. The melter gasifier as claimed in claim 12, further comprising: the melter gasifier has a dome and a conical region adjoining to the dome; and the protrusion is within 50-75%, of the height of the conical region.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] The invention is explained in more detail below on the basis of the figures, which are schematic and given by way of example.

[0045] FIG. 1 shows an integrated plant according to the invention comprising a melter gasifier and first and second reduction systems,

[0046] FIG. 2 shows the melter gasifier from FIG. 1, with a first embodiment of the mixing region,

[0047] FIG. 3 shows the melter gasifier from FIG. 1, with a second embodiment of the mixing region provided by a protrusion in the form of a tube.

DESCRIPTION OF EMBODIMENTS

[0048] FIG. 1 shows a system for carrying out the method according to the invention for producing liquid pig iron 1 designed as a Corex? integrated direct reduction system. The iron-oxide-containing feed materials 2 are fed to a first reduction system 4, a Corex? reduction shaft with a fixed bed, by way of a feed line 20 for supplying iron-oxide-containing feed materials 2.

[0049] The iron-oxide-containing feed materials 2 are reduced by means of a reducing gas 5 to form a partially reduced first iron product 3 (FIG. 2), which is subsequently introduced by way of one or more iron product feed lines 22 opening out into a melter gasifier 11 and into the melter gasifier 11. Within the context of the present text, the iron product 3 comprises iron both in an oxidized, for example oxidic, form and in a reduced, that is metallic, form. In the iron product 3, the iron may take both forms. This is then referred to for example as pre-reduced iron carrier material, which though not yet finally reduced completely in comparison with a metallic form, is however already reduced more in comparison with a previous state. It may also take only one of the two forms. In the case of Corex?, the iron product 3 is for example hot, so-called direct reduced iron (DRI) or corresponding iron carrier material with a metalization, which means it is not yet considered to be DRI. In the case of the Corex? process, the iron product 3 is discharged from the reduction shaft of the first reduction system 4 charged with hot reducing gas 5 and is transported by means of gravitational force into the melter gasifier 11 by way of one or more chutes, and if appropriate distributor flaps. For example, a number of chutes may be provided, distributed over the circumference of the dome of the melter gasifier 11.

[0050] In addition, solid carbon carriers as the first carbon carrier 10, in the form of lump coal and/or agglomerated fine coal and/or coal-containing briquettes, are introduced into the melter gasifier 11 by way of a feed line 23, and first oxygen-containing gas 9, 9a is introduced by way of media feed lines 24. The charging of the first carbon carrier 10 and partially reduced iron product 3 into the melter gasifier 11 generally takes place separately from one another. The first carbon carrier 10 is for example supplied from a storage container for carbon-containing material by way of screw conveyors to a distributing device, which is mounted centrally in the dome of the melter gasifier 11 and by which the first carbon carrier 10 is distributed over the cross section of the melter gasifier 11 during the input into the melter gasifier 11, see in this respect FIGS. 2 and 3.

[0051] The carbon carriers 10, and if appropriate the fine coal 14, introduced into the melter gasifier 11 are gasified by means of the oxygen-containing gas 9a (FIG. 2) producing the reducing gas 5. This produces a gas mixture, which consists mainly of CO and H.sub.2.

[0052] The reducing gas 5 is introduced into the first reduction system 4 by way of the reducing gas line 12, preceded by dedusting in a dedusting device 26. The separated dust is returned to the melter gasifier 11, to be specific, by means of one or more dust burners 17.

[0053] The first iron product 3 introduced into the melter gasifier 11 is melted by the heat produced during the gasification of the carbon carriers 10 to form the liquid pig iron 1. The hot metal smelted in the melter gasifier 11 and the slag are drawn off.

[0054] The reducing gas consumed during the reduction of the iron-oxide-containing feed materials 2 is referred to as top gas 6 and is drawn off as export gas from the first reduction system 4 by way of an export gas line 19 and cleaned there by means of wet scrubbers 32. The export gas may be compressed in a compressor 33, subsequently subjected to CO.sub.2 removal 21 and heating 31 and be introduced into a second reduction system 7 for producing a partially reduced second iron product 8, in particular direct reduced iron (DRI) in the form of iron sponge. For this second reduction system 7 there is consequently no need for a system specifically for producing reducing gas, for example a reformer, since this process takes place in the melter gasifier 11.

[0055] After leaving the melter gasifier 11, part of the reducing gas 5 may be further cleaned in a wet scrubber 27, cooled and mixed in with the export gas 6.

[0056] The melter gasifier 11 receives introduction elements of three types opening out into the melter gasifier 11, which are formed as an oxygen nozzle 15, as a dust burner 17 and as a mixing region 18, and which however may in each case also be multiply present. On the outside, with respect to the melter gasifier 11, the introduction elements are connected to the media feed lines 24 for the second oxygen-containing gas 9b. There is at least one carbon carrier line 25, by means of which the second carbon carrier 13, which may be liquid and/or gaseous, is introduced into the melter gasifier 11. If the second carbon carrier is gaseous, there may additionally also be in each case a carbon carrier line 25 opening out into the reducing gas line 12.

[0057] A second carbon carrier 13 in liquid and/or in gas form, for example coke oven gas or natural gas, is fed to the melter gasifier 11 by way of the carbon carrier line 25, which opens out into the mixing region 18.

[0058] Coke oven gas has a typical composition of

65 percent by volume hydrogen (H.sub.2),
2.5 percent by volume nitrogen (N.sub.2),
6 percent by volume carbon monoxide (CO),
22 percent by volume methane (CH.sub.4),
3 percent by volume other hydrocarbons (C.sub.nH.sub.m),
1.5 percent by volume carbon dioxide (CO.sub.2).

[0059] The carbon carrier line 25 may in this case be connected to a coking plant.

[0060] Natural gas has a typical composition of

75-99 percent by volume methane,
1-15 percent by volume ethane,
1-10 percent by volume propane.

[0061] In addition, hydrogen sulfide, nitrogen and carbon dioxide may be contained.

[0062] The second carbon carrier 13 and second oxygen-containing gas 9b in the form of oxygen of technical purity are introduced into the mixing region 18, which is provided just above the fixed bed of the melter gasifier 11 in the interior thereof, here at the same height as the dust burner 17, under the dome. The mixing region 18 is not separated here from the remaining interior space of the melter gasifier 11 by internal components, such as separating walls. During the operation of the melter gasifier 11, the mixing region 18 is evident by the reaction zone (flame), which is produced when there is complete oxidation of a small part (less than 25%) of the second carbon carrier 13 to form carbon dioxide CO.sub.2 and water H.sub.2O. The media feed line 24 for the second oxygen-containing gas 9b and the carbon carrier line 25 open out into the mixing region 18. The two lines may form an acute angle with one another, so that the second oxygen-containing gas 9b and the second carbon carrier 13 move toward one another within the mixing region 18 and as a result are mixed. There may also be a number of nozzles provided for each of the two media 9b, 13, arranged such that there is a swirling of the two media 9b, 13 when they enter the mixing region 18 through the nozzles.

[0063] The mixing of the second carbon carrier 13 and the second oxygen-containing gas 9b in the mixing region 18 causes a partial oxidation, that is the hydrocarbons of the second carbon carrier 13 are predominantly converted into carbon monoxide CO and hydrogen H.sub.2. In a small part (less than 25%), the oxygen of the oxygen-containing gas 9b and the hydrocarbons are completely oxidized in the mixing region 18 to form carbon dioxide CO.sub.2 and water H.sub.2O. This produces a flame with a flame temperature of more than 1000? C., to be specific approximately between 1150 and 1500? C., whereby there is a sufficiently high temperature for the conversion into reducing gas.

[0064] The small part (less than 10%) of hydrocarbons of the second carbon carrier 13 that are not broken down, or are broken down only to smaller hydrocarbons, in the mixing region 18 can then be broken down further in the remaining volume within the melter gasifier 11 by dust particles that are present in any case and act as a catalyst, also containing inter alia metallic iron.

[0065] A number of such mixing regions 18 may of course be provided, for example a number of mixing regions 18 at the same height and distributed over the circumference of the melter gasifier 11, a number of mixing regions 18 one above the other, or a number of mixing regions one above the other and distributed over the circumference.

[0066] In FIG. 2, the melter gasifier 11 from FIG. 1 is shown by itself. A first carbon carrier 10 in the form of coal (solid lines) is introduced into the melter gasifier 11 through the middle outlet in the dome 30, into which the feed line 23 opens out. The first carbon carrier 10 is in this case supplied by a distributing device (not shown), which is mounted centrally in the dome of the melter gasifier 11 and by which the first carbon carrier 10 is distributed over the cross section of the melter gasifier 11.

[0067] The iron product 3 from the reduction shaft of the first reduction system 4, to be specific, the product is direct reduced iron DRI, is transported by means of gravitational force into the melter gasifier 11 by way of one or more iron product feed lines 22 formed as chutes. There is a plurality of such chutes distributed over the circumference of the dome 30 of the melter gasifier 11.

[0068] Iron product 3 and carbon carriers 10 fall down through the dome 30 into the conical region 29 of the melter gasifier 11 and form there the fixed bed 34, which here fills the conical region 29 to approximately halfway. There is however also the possibility of extending the lower part of the dome 30 in the form of a cylinder and shortening the conical region 29. In this case, the conical region 29 could even be completely filled with the fixed bed 34. The passage of the carbon carrier line 25 and the media feed line 24 or of the piece of line that is shown, and consequently also the mixing region 18, would then he arranged in the extended lower cylindrical region of the dome 30. In the center of the fixed bed 34, below the surface thereof, there is a reaction-free zone, which is referred to as the dead man 35.

[0069] Both the second carbon carrier 13 and the second oxygen-containing gas 9b are passed here through the wall of the conical region 29 by means of a piece of line that represents a continuation or unification of the carbon carrier line 25 and the media feed line 24. The carbon carrier 13 and the second oxygen-containing gas 9b may be mixed already in this piece of line. They may however also be carried separately in this piece of line (for instance in concentric pipes) and only mix in an end region of the piece of line, which is formed for example as a nozzle, or only after the end of the piece of line in the interior of the melter gasifier 11. In any case, the (further) mixing of the carbon carrier 13 and the second oxygen-containing gas 9b and a partial oxidation take place in the mixing region 18, which adjoins the piece of line shown.

[0070] The passage of the carbon carrier line 25 and the media feed line 24 or the piece of line shown lies here approximately between 50-75% of the height of the conical region 29 (measured from the bottom) of the melter gasifier 11. Consequently, the mixing region 18 is also at approximately between 50-75% of the height of the conical region 29. Depending on the embodiment, the arrangement may also lie above 75% of the conical region 29 or in the lower part of the dome 30, for instance if the lower part of the dome 30 is formed as a cylindrical region.

[0071] Shown in FIG. 3 is a variant of the design for the mixing region 18 in the form of a protrusion, which is formed here by a cylindrical tube 28. Otherwise, the construction of the melter gasifier 11 and of the Corex? plant are the same as FIG. 1 and FIG. 2.

[0072] The cylindrical tube 28 has been inserted into a corresponding opening in the melter gasifier 11 and finishes flush with the inner wall of the melter gasifier 11, that is, it does not protrude into the volume within the melter gasifier 11. The media feed line 24 for the second oxygen-containing gas 9b and the carbon carrier line 25 for the second carbon carrier 13 both open out into the mixing region 18, which on the one hand is formed by the tube 28 itself, on the other hand also protrudes into the remaining volume of the melter gasifier 11. Undisturbed mixing of the second oxygen-containing gas 9b and the second carbon carrier 13 can take place within the tube 28. The energy for the partial oxidation within the tube 28 in this case likewise is provided by the partial oxidation of the second carbon carrier 13, the losses being kept down by an appropriate refractory lining of the tube 28.

[0073] In order to ensure that the mixing region 18 extends as far as possible into the interior of the melter gasifier 11, and consequently the heat losses in the mixing region 18 can be kept down, the longitudinal axis of the tube 28 may be aligned normal to the tangential plane of the inner wall of the melter gasifier 11. In FIG. 3, the tube 28 is aligned approximately horizontally.

[0074] The diameter of the tube 28 is generally a multiple of the diameter of a media feed line 24 or of a carbon carrier line 25 or of a dust burner 17 or of the outlet opening of an oxygen nozzle 15.

[0075] In order to be able to convert more of the second carbon carrier 13, a number of tubes 28 per melter gasifier 11 may be provided. In this case, the tubes 28 and the associated mixing regions 18 may be distributed over the circumference and/or the height of the melter gasifier 11, as explained in the case of FIG. 1.

[0076] The two lines 24, 25 may again form an acute angle with one another, so that the second oxygen-carrying gas 9b and the second carbon carrier 13 move toward one another within the mixing region 18, in particular within the tube 28, and as a result are mixed. There may also be a number of nozzles provided for each of the two media 9b, 13, arranged such that there is a swirling of the two media 9b, 13 when they enter the mixing region 18, in particular the tube 28, through the nozzles.

[0077] Both for mixing regions 18 without a protrusion and for mixing regions 18 with a protrusion, they are preferably arranged 1-2 m above the fixed bed 34. As shown in FIGS. 2 and 3, the mixing region or regions 18 may for example be under the dome 30 of the melter gasifier 11 in the conical region 29 of the melter gasifier 11 or in the lower part of the cylindrically extended dome 30. The conical region 29 is the frustoconically upwardly widening part of the melter gasifier 11, to which the approximately hemispherical dome 30 adjoins.

[0078] If instead of the Corex? plant a Finex? plant is used, after the last of the three to four fluidized bed reactors, in which the pre-reduction of the fine ore takes place, a partial stream of the offgas is removed as export gas, and otherwise used as in FIG. 1. As in the case of the Corex? plant, part of the surplus gas from the melter gasifier 11 may also be added to the export gas.

LIST OF DESIGNATIONS

[0079] 1 liquid pig iron [0080] 2 iron-oxide-containing feed materials [0081] 3 partially reduced first iron product [0082] 4 first reduction system [0083] 5 reducing gas [0084] 6 top gas [0085] 7 second reduction system [0086] 8 partially reduced second iron product [0087] 9 oxygen-containing gas [0088] 9a first oxygen-containing gas [0089] 9b second oxygen-containing gas [0090] 10 first carbon carrier [0091] 11 melter gasifier [0092] 12 reducing gas line [0093] 13 second carbon carrier [0094] 14 fine coal [0095] 15 oxygen nozzle [0096] 16 dust [0097] 17 dust burner [0098] 18 mixing region [0099] 19 export gas line [0100] 20 feed line for supplying iron-oxide-containing feed materials [0101] 21 CO.sub.2 removal [0102] 22 iron product feed line [0103] 23 feed line for the first carbon carrier 10 [0104] 24 media feed line [0105] 25 carbon carrier line [0106] 26 dedusting device [0107] 27 wet scrubber [0108] 28 protrusion (tube) [0109] 29 conical region of the melter gasifier 11 [0110] 30 dome of the melter gasifier 11 [0111] 31 heating [0112] 32 wet scrubber for top gas [0113] 33 compressor [0114] 34 fixed bed [0115] 35 dead man