WO1998058088A1

WO1998058088A1 - Process and metallurgical vessel for feeding a valuable substance into a molten bath

Info

Publication number: WO1998058088A1
Application number: PCT/AT1998/000133
Authority: WO
Inventors: Norbert Ramaseder; Leopold Werner Kepplinger; Eva-Maria Kern; Hermann Schubert
Original assignee: Voest-Alpine Industrieanlagenbau Gmbh; SCHUBERT, Renate
Priority date: 1997-06-16
Filing date: 1998-05-26
Publication date: 1998-12-23
Also published as: AT405188B; ATA104097A

Abstract

A process is disclosed for feeding a valuable substance (4), either in the form of particles, in particular in the form of dust, or in a liquid form, into a molten bath (2), in particular a steel molten bath, contained in a metallurgical vessel (1), while generating a bath stirring motion (8) by means of at least one molten bath stirring device (9). The valuable substance (4) is fed into the molten bath (2) by means of at least one feeding device (5) independent of the molten bath stirring device (9) in a region of the molten bath (2) in which a bath stirring motion (8) is generated with a component directed downwards or, when the valuable substance (4) is fed below the surface (6) of the molten bath, such as, for example, in the lower region of the molten bath (2), with a component approximately parallel to the bottom region (12) of the metallurgical vessel (1).

Description

METHOD AND METALLURGICAL VESSEL FOR PUTTING A RECOVERY MATERIAL INTO A MELTING BATH

The invention relates to a method for introducing a valuable substance, either in particulate form, in particular in the form of dust, or in liquid form, into a molten bath located in a metallurgical vessel, in particular into a molten steel bath, in which a bath stirring movement is generated by means of at least one molten bath stirring device is, as well as a metallurgical vessel for performing the method.

From EP-B-0 579 591 it is known to introduce filter dust into a metallurgical vessel by means of hollow electrodes or by means of under-bath showers, the filter dust - when using hollow electrodes - being inflated onto the melt located in the metallurgical vessel or onto the foam slag lying on the melt or - when using under-bath nozzles - push the melt through from bottom to top. The disadvantage of this known method is to be seen in the fact that the filter dust is only inflated onto the melt or passes through it rapidly from bottom to top, which results in little or no interaction of the introduced material with the melt. This is disadvantageous if there is to be an intensive interaction of the introduced material with the melt, be it for energetic or metallurgical reasons

The object of the invention is to introduce a valuable substance into the molten bath in such a way that the valuable substance fully takes effect in the molten bath. In particular, the energy content of the valuable substance should be used as completely as possible directly in the molten bath. For example, the valuable substance carbon should be able to be used as an energy carrier by being in solution as completely as possible. If desired, the recyclable material should also have a metallurgical effect directly in the melt.

This object is achieved according to the invention in that the valuable substance is introduced into the melt pool by means of at least one introduction device which is provided independently of the melt pool resting device, in an area of the melt pool in which a bath stirring movement with a downward movement or, when the valuable substance is introduced, below the melt pool Surface, such as in the lower region of the melting bath, is generated with a movement component directed approximately parallel to the base region of the metallurgical vessel. This results in an increase in the distance of the valuable material in the molten pool compared to the purely static case, i.e. without moving the molten pool, and thus a maximization of the residence time of the valuable material in the molten pool as well as a - by taking the valuable material with the bath stirring movement Optimization of the interaction of the material with the molten pool. This makes it possible in a simple manner to double the length of time that the valuable substance remains in the molten bath or to extend it further.

Carbon-containing materials, in particular shredder light fraction, plastic waste and / or plastic-containing residues, and / or iron oxide-containing materials and / or alloying elements and / or non-metallic feedstocks, in particular slag formers, and / or liquid carbon carriers are preferably used as the valuable material.

When introducing a valuable substance by means of hollow electrodes, as known from the prior art, in particular when introducing light shredder fraction, the hollow electrodes can very easily become clogged.

EP-B-0 521 844 discloses blowing shredder waste into the high-temperature melting zone of a scrap-melting reactor and using it energetically by burning. However, the shredder waste is blown directly into the scrap to be melted and therefore does not come into contact with the melt, or comes into contact with it only slightly, which results in a slight interaction of the material introduced with the melt.

DE-A-32 12 534 discloses a process for the gasification of household waste and similar wastes in an iron melt, in which the wastes are pressed into the iron melt below the surface thereof. A disadvantage of this method is the low interaction with the melt pool due to the short residence time of the introduced material in the melt pool.

In contrast to this, the procedure according to the invention, for example when introducing carbon-containing materials, e.g. Shredder light fraction and / or plastic waste, due to the increased residence time in the melt pool for maximum energy utilization of the valuable material when it is completely implemented directly in the melt pool.

The method according to the invention further ensures that when carbon-containing materials are introduced as the valuable material, the carbon dissolves, which means that it can be used, if necessary, metallurgically. The temperature of the molten bath and the residence time can be selected so that graphite is formed in the molten bath. It is essential here that the material introduced must find the greatest possible path length in the weld pool. This path length (and thus the length of stay in the melt) depending on the insertion angle, medium, flow rate, pressure and on the movement of the weld pool in the area of the insertion device.

The method according to the invention also has the consequence that no organically bound carbon gets into the furnace space, but is already converted to CO in the molten bath. This prevents the formation of dioxins and furans in the exhaust gas from the melting unit.

The valuable substance is particularly advantageously introduced into the molten bath in finely dispersed form. As a result of the additional lengthening of the residence time in the molten pool, there is a particularly intensive and efficient interaction of the valuable substance with the molten pool

From DE-A-44 26 929 a method for recycling plastic waste and / or plastic-containing residues in a steel melting unit is known, in which, however, the materials to be recycled are first mixed together, compacted and provided with a plastic coating and in this state the high-temperature zone of the steel melting unit are disadvantageous here that the materials to be used are added in large batches, which, in contrast to the procedure according to the invention, results in a less efficient implementation of the materials in the melting unit.

According to the invention, the valuable substance is preferably introduced with a movement component in the direction of the bath stirring movement generated in the insertion area. The bath stirring movement is advantageously supported by the pumped medium for the valuable substance.

According to a preferred embodiment of the method according to the invention, the valuable material is introduced into the molten bath through at least one under bath opening arranged in the side wall of the metallurgical vessel at at least one point at which a bath stirring movement is generated with a horizontal and / or downward movement component of the molten bath the material introduced into the molten bath is initially conveyed approximately parallel to the side wall of the metallurgical vessel and preferably downwards, thereby maximizing the length of time in the molten bath.

According to a further preferred embodiment, the valuable substance is introduced into the weld pool through at least one bottom opening at at least one point at which one Bath stirring movement is generated with a movement component of the melting bath oriented approximately parallel to the bottom region of the metallurgical vessel. The residence time of the introduced material is also increased compared to the case in which the melting bath is not moved and the introduced material rises vertically upwards.

According to a further preferred embodiment, the valuable material is introduced into the molten pool from at least one lance from at least one lance, preferably a wear lance, at which a bath stirring movement with a downward movement component of the molten bath is generated pulled the weld pool

The bath stirring movement is advantageously produced by direct current flow in the weld pool, preferably by means of an arc which is formed on at least one electrode directed onto the surface of the bath, a bath movement downward being generated by the current flow from the electrode into the bath. The valuable substance is advantageously introduced into an area between electrodes directed at the surface of the molten bath

According to a further preferred embodiment, the bath stirring movement is generated by induction. Here, the valuable substance is introduced into the downward flow of the molten bath formed thereby.

CO resulting from the reaction of the valuable substance in the melt pool is expediently afterburned above the melt pool, the heat generated thereby being able to be used as additional energy for heating the melt pool

A metallurgical vessel for carrying out the method according to the invention, with a vessel space receiving a molten bath, with at least one molten bath resting device and with at least one introduction device for a valuable substance, either in particle form, in particular in the form of dust, or in liquid form, is characterized in this way that the introduction device for the valuable substance is structurally separated from the melting bath resting device and is arranged at a point on the metallurgical vessel or in the vessel space in the area of which the melting bath is either directed downwards or, when the valuable substance is introduced, below the surface of the melting bath, such as in the lower region of the melting bath, has a movement component directed approximately parallel to the base region of the metallurgical vessel The introduction device for the valuable substance advantageously has an orifice pointing in the direction of the bath stirring movement. This makes it easier to take the introduced recyclable material with the bath stirring movement or is supported by a conveying medium for the recyclable material.

According to a preferred embodiment, the introduction device for the valuable material is designed as at least one under bath opening, preferably as an under bath nozzle, which is arranged in the side wall of the metallurgical vessel. A nozzle suitable as an underbath nozzle is known, for example, from DE-C-42 38 020.

According to a further preferred embodiment of the metallurgical vessel according to the invention, the introduction device for the valuable material is designed as at least one bottom opening, preferably as a bottom nozzle, or according to yet another embodiment as at least one lance from above, preferably as a wear lance.

The molten bath stirring device is expediently designed as at least one electrode directed towards the molten bath surface. The lance for introducing the valuable substance is preferably arranged between electrodes directed onto the surface of the molten bath.

According to a further expedient embodiment, the melt bath stirring device is designed as an induction coil which generates a bath stirring movement directed downward. According to a still further preferred embodiment, the molten bath stirring device is designed as an induction coil which generates a bath stirring movement about a vertical axis.

The invention is explained in more detail below with reference to several exemplary embodiments shown in the drawing, with FIGS. 1 to 3 illustrating preferred exemplary embodiments of the method according to the invention or of the metallurgical vessel according to the invention.

1 shows a metallurgical vessel 1, for example an electric arc furnace (EAF), for holding a melting bath 2, in the example shown a steel melting bath. The metallurgical vessel 1 is provided with a refractory lining 3. A valuable substance F4 is introduced into the molten bath 2 by means of an introduction device 5, which is designed as an under bath nozzle 7 arranged below the molten bath surface 6.

Shredder light fraction (SLF) is introduced as recyclable material 4; however, other carbon-containing materials, in particular comminuted materials, can equally be used Plastic waste and / or plastic-containing residues, iron oxide-containing materials, in particular metallurgical dust, and alloying elements, for example chromium, titanium, tungsten, nickel, cobalt, vanadium, molybdenum and others, as well as non-metallic feedstocks, in particular fluxing agents and slag formers, for example lime, and liquid carbon carriers are introduced .

In the melt pool 2, a bath stirring movement 8 is generated by means of a melt bath stirring device 9, which in the exemplary embodiment shown in FIG. 1 is designed as an induction coil 10, the bath stirring movement 8 being directed downwards along the side wall 11 of the metallurgical vessel 1 and in the bottom region 12 of the metallurgical vessel 1 is directed approximately parallel to the bottom region 12. It is important here that the bath stirring movement 8 is directed downward in the region of the mouth 13 of the lower bath nozzle 7. As a result, the valuable substance 4 is taken downwards, thereby maximizing its path and thus its length of stay in the molten bath 2. In the example shown, the length of stay is more than doubled.

The path of the recyclable material 4 introduced into the molten bath 2 is indicated in FIG. 1 by arrow 14. To facilitate the taking of the valuable material 4 with the bath stirring movement 8, the mouth 13 of the lower bath nozzle 7 is in the direction of the bath stirring movement 8 generated in the insertion area 15, i.e. also directed downwards.

The residence time of the shredder light fraction used in this exemplary embodiment as recyclable material 4 in the molten bath 2 is extended so far that the carbon introduced with the shredder light fraction dissolves. The temperature of the melt pool 2 and the residence time are chosen so that graphite formation in the melt pool 2 is possible.

The light shredder fraction is advantageously introduced into the molten bath 2 in finely dispersed form. In finely dispersed form, there is an additional extension of the residence time in the melt pool 2 and thus a particularly intensive interaction of the shredder light fraction with the melt pool 2, as well as their optimal use of energy.

The gas formed during the reaction of the shredder light fraction in the melt pool 2, which mainly consists of CO, is afterburned by oxygen, which is introduced by means of nozzles not shown, above the melt pool surface 6 in the vessel space 16 to CO ₂ . The heat generated here can advantageously be used as additional energy for heating the melting bath 2. According to the embodiment shown in FIG. 2, a metallurgical vessel 1 is equipped with a floor nozzle 17 provided in the floor area 12 for introducing a valuable material 4 - in this example again a shredder light fraction. A bath stirring movement 8 is generated such that the movement component 8a in the area of the mouth 18 of the floor nozzle 17 is directed approximately parallel to the floor area 12 of the metallurgical vessel 1. The upward movement of the recyclable material 4 is deflected sideways, as illustrated by the arrows 14 in FIG. 2. This measure also leads to an optimization, ie an extension, of the residence time of the valuable substance 4 in the molten bath 2, in particular if the valuable substance 4 is introduced into the molten bath 2 in finely dispersed form. A conveying device 19 indicated in FIG. 2 serves to convey the valuable substance 4 in finely dispersed form.

In the embodiment shown in FIG. 3, the valuable material 4 is introduced into the molten bath 2 by means of a lance 20, for example a wear lance, in the vicinity 21 of the electrode 22 which is directed towards the molten bath surface 6. Starting from the electrode 22, a downward bath stirring movement 8 is generated by the arc 23. The material 4 introduced by means of the lance 20 is first pulled downward by the bath stirring movement 8 - as can be seen by the arrows 14 - and continues to follow the circulating movement of the melting bath 2 indicated by 8b. This maximizes the residence time of the material 4 in the melting bath 2.

The method according to the invention or the metallurgical vessel 1 according to the invention is in no way limited to the embodiments shown in FIGS. 1 to 3. For example, it is also possible to generate a bath stirring movement 8 about a vertical axis of the metallurgical vessel 1, which also leads to an increase in the residence time of the valuable substance 4 in the molten bath 2 when the valuable substance 4 is introduced below the molten bath surface 6.

Claims

Claims:

1. A method for introducing a valuable substance (4), either in particle form, in particular in the form of dusts, or in liquid form, into a molten bath (2) located in a metallurgical vessel (1), in particular into a molten steel bath, in which a bath stirring movement (8) is generated by means of at least one melt bath stirring device (9), characterized in that the valuable substance (4) into the melt bath (2) by means of at least one introduction device (5) provided independently of the melt bath stirring device (9) into an area of the molten bath (2) is introduced in which a bath stirring movement (8) with a downward or, when introducing the valuable substance (4) below the molten bath surface (6), such as in the lower region of the melting bath (2), with a movement component directed approximately parallel to the base region (12) of the metallurgical vessel (1).

2. The method according to claim 1, characterized in that as a valuable material (4) carbon-containing materials, in particular shredder light fraction, plastic waste and / or plastic-containing residues, and / or iron oxide-containing materials and / or alloying elements and / or non-metallic feedstocks, in particular slag formers, and / or liquid carbon carriers are used.

3. The method according to claim 1 or 2, characterized in that the valuable substance (4) is introduced in finely dispersed form.

4. The method according to one or more of claims 1 to 3, characterized in that the valuable substance (4) is introduced with a movement component in the direction of the bath stirring movement (8) generated in the introduction region (15).

5. The method according to one or more of claims 1 to 4, characterized in that the valuable material (4) through at least one in the side wall (11) of the metallurgical vessel (1) arranged under bath opening in the molten bath (2) introduced at at least one point on which a bath stirring movement (8) with a horizontal and / or downward movement component of the molten bath (2) is generated.

6. The method according to one or more of claims 1 to 5, characterized in that the valuable substance (4) is introduced through at least one bottom opening into the molten bath (2) at at least one point at which a bath stirring movement (8) with an approximately movement component of the melting bath (2) directed parallel to the base region (12) of the metallurgical vessel (1) is generated.

7. The method according to one or more of claims 1 to 6, characterized in that the valuable substance (4) by at least one lance (20), preferably a wear lance, is introduced from above into the weld pool (2) at at least one point which generates a bath stirring movement (8) with a downward movement component of the molten bath (2).

8. The method according to one or more of claims 1 to 7, characterized in that the bath stirring movement (8) by direct current flow in the molten bath (2), preferably by means of an arc (23) which is at least one on the molten bath surface (6 ) directed electrode (22) is formed, is generated.

9. The method according to one or more of claims 1 to 8, characterized in that the bath stirring movement (8) is generated by induction.

10. The method according to one or more of claims 1 to 9, characterized in that by reaction of the valuable substance (4) in the melt pool (2) resulting CO above the melt surface (6) in the vessel space (16) is afterburned.

11. Metallurgical vessel (1) for performing the method according to one or more of claims 1 to 10, with a vessel (16) receiving a molten bath (2), with at least one molten bath stirring device (9) and with at least one introduction device (5 ) for a valuable substance (4), either in particle form, in particular in the form of dusts, or in liquid form, characterized in that the introduction device (5) for the valuable substance (4) is structurally separated from the melt bath stirring device (9) and is arranged at a point on the metallurgical vessel (1) or in the vessel space (16), in the area of which the molten pool (2) either faces downwards or, when the valuable substance (4) is introduced, below the molten pool surface (6), such as in the lower region of the melting bath (2), has a movement component directed approximately parallel to the base region (12) of the metallurgical vessel (1).

12. Metallurgical vessel (1) according to claim 11, characterized in that the introducing device (5) for the valuable substance (4) has a mouth (13, 18, 24) pointing in the direction of the bath stirring movement (8).

13. Metallurgical vessel (1) according to claim 11 or 12, characterized in that the introduction device (5) for the valuable substance (4) is designed as at least one under bath opening, preferably as an under bath nozzle (7), which in the side wall (11) of the metallurgical vessel (1) is arranged.

14. Metallurgical vessel (1) according to one or more of claims 11 to 13, characterized in that the introduction device (5) for the valuable substance (4) is designed as at least one bottom opening, preferably as a bottom nozzle (17).

15. Metallurgical vessel (1) according to one or more of claims 11 to 14, characterized in that the introduction device (5) for the valuable substance (4) is designed as at least one lance (20), preferably as a wear lance.

16. Metallurgical vessel (1) according to one or more of claims 11 to 15, characterized in that the molten bath stirring device (9) is designed as at least one electrode (22) directed towards the molten bath surface (6).

17. Metallurgical vessel (1) according to claim 15 or 16, characterized in that the lance (20) between the molten bath surface (6) directed electrodes (22) is arranged.

18. Metallurgical vessel (1) according to one or more of claims 11 to 17, characterized in that the melt pool stirring device (9) is designed as an induction coil (10) which generates a downward movement of the melt pool (2).

19. Metallurgical vessel (1) according to one or more of claims 11 to 17, characterized in that the molten bath stirring device (9) is designed as an induction coil (10) which generates a bath stirring movement (8) about a vertical axis.