WO2019096808A1

WO2019096808A1 - Method for producing a metal melt in a furnace

Info

Publication number: WO2019096808A1
Application number: PCT/EP2018/081137
Authority: WO
Inventors: Harmen Johannes Oterdoom; Erwan FLOCH; Adriaan Scheltema BEDUIN; Christian Kempe; Andreas Liedtke; Ralf NÖRTHEMANN
Original assignee: Sms Group Gmbh
Priority date: 2017-11-20
Filing date: 2018-11-14
Publication date: 2019-05-23
Also published as: DE102017220655A1

Abstract

The invention relates to a method for producing a metal melt (1) in a furnace (2), in which metallic material is melted in the working space of the furnace (2), wherein material to be melted is fed into the working space of the furnace (2) by way of a feeding device (3). In order to achieve improved energy efficiency, better protection of the furnace and greater process stability, the invention provides that, when it enters the working space of the furnace (2), the material (4) fed in by way of the feeding device (3) is subjected to a specific atomization by pneumatic (5), mechanical (6) and/or magnetic (7) elements as it passes the feeding device (3).

Description

Process for producing a metallic melt in an oven

The invention relates to a method for producing a metallic melt in an oven, in which metallic material is melted in the working space of the furnace, wherein material to be melted is fed via a feed device into the working space of the furnace.

A generic method disclosed in DE 696 22 587 T2. Similar solutions are shown in JP 3291353 A, JP 2000119720 A and CN 203595403 U.

In prior art charging systems in an oven of the type mentioned, the material to be melted falls through the feeder directly into the bottom area of the furnace. As an example, the production of FeCr in

Called DC stoves. This sometimes results in insufficient mixing with hot gas. In addition, the degree of atomization depends on the condition of the delivered material, d. H. the fineness of the granular material supplied.

On the other hand, in the production of FeNi, it may happen that the material supplied is so fine that it forms too large a dust cloud, whereby too much material is conveyed back out of the furnace, in particular with the furnace exhaust gas.

In general, the higher the load on the oven, the less material is added to the oven by the introduction of the process. However, the presence of too low a degree of atomization of the supplied material is just as harmful as too high a degree of the same. The material to be introduced (fine ore) often has a consistency such as dust or sand, whereby the amount of the material to be introduced is process-related. The amount that is discharged through the exhaust gas from the oven must be adjusted accordingly in the oven. In previously known solutions, therefore, there is often no adequate balance for the reflow process in the oven.

Furthermore, little attention is given to the question of whether and in what way the degree of atomization has an effect on the energy efficiency of the process. If too much material comes in a limited area, it may be that the material does not dissolve sufficiently in the melt and then does not react sufficiently, but rather builds up or sinks too low in the bath. Flierdurch process disturbances can occur. However, too high a degree of atomization has procedural disadvantages. In particular, then relatively much material can be discharged through the furnace gases again. Caking or sintering can take place in the furnace area, in particular in the area of the side walls and the ceiling area. The material can also spread too much and thus lead to less effective cooling in the middle area of the bath.

This can cause damage to the oven due to excessive radiation. Furthermore, the degree of preheating is difficult to influence and energy efficiency is therefore generally not optimal.

The proportion of material entering the bath should be large enough to produce a cooling effect, but not so large that the material can no longer be absorbed by the process. The invention is therefore based on the object, a method of the type mentioned in such a way that an improved energy efficiency is possible. Furthermore, the protection of the furnace should be improved. Finally, it should be achieved that the process stability of the process is increased. It is also important to achieve a favorable balance between the electrical energy input and its use for the melting of the estate.

The solution to this problem by the invention is characterized in that the material fed in via the feed device is subjected to targeted atomization on entering the working space of the furnace by pneumatic, mechanical and / or magnetic elements when passing through the feed device.

The melting is preferably carried out by means of at least one arc.

The supplied material is deflected according to a first embodiment of the invention when passing through the feed device by at least one gas jet. The gas jet can be a jet of hydrogen and / or carbon dioxide. It is also possible to use a gas jet of carbon monoxide (CO), a mixture of carbon monoxide and hydrogen (CO + H ₂ ), recirculated furnace gas, a gas from other process stages in the plant, and an inert gas such as argon (Ar). , If you work in a closed furnace with a gas mixture of carbon monoxide and hydrogen, the recycling of the gas is particularly easy to accomplish. For controlling or regulating the atomization it can be provided that the gas jet is changed in its flow velocity in order to achieve a defined degree of atomization. Furthermore, it can be provided for this purpose that the gas jet is changed in its angle of incidence to the flow of the supplied material in order to achieve a defined degree of atomization. Another embodiment of the invention provides that the supplied material is deflected when passing through the feed device by at least one baffle. In this case, the position or the position of the at least one baffle can be changed in order to achieve a defined degree of atomization. Alternatively or additionally, the shape of the at least one baffle can be changed in order to achieve a defined degree of atomization.

A further embodiment of the invention provides that the supplied material is deflected by at least one magnet when passing through the feed device.

In all the cases mentioned, the atomization can take place in the closed loop in such a way that there is a defined degree of atomization during the introduction of the material via the feed device.

The feeder is thus designed according to the present invention in a special way to influence the degree of atomization of the supplied material can. The measures or elements provided for this purpose can be mechanical, pneumatic or magnetic.

The invention relates primarily to a feed system for an oven with an open bath, in which a certain amount of dust is required to protect the melt metallurgical vessel. The proposed method makes it possible to produce a certain degree of atomization and thus to influence or control the process and in particular the flow of material.

Particular preference is therefore provided that is checked by detecting corresponding process parameters, if the process runs optimally and then in the closed loop the degree of atomization of the supplied material is influenced to keep predetermined parameters in the optimum range. In this case, as the measured variable that provides information about the process state, in particular the exhaust gas temperature from the furnace can be detected, for which purpose suitable thermocouples are integrated in the furnace (in particular in its side wall or ceiling) in order to constantly record the current temperature.

Advantageously, it is thus possible to achieve improved protection of the system against radiation. Energy efficiency is thereby increased equally. It is also advantageous that prereduction or preheating can take place in an improved manner.

A further advantage is that the thermal load on the ceiling and the side wall of the furnace can be reduced. Furthermore, it is advantageous that a lower gas generation takes place in the bath, since a prereduction can take place, which leads to lower instabilities in the bath. There is thus a lower risk of boiling up or eruptions. An advantageous further improvement can be achieved in that the furnace is formed with a height which is greater than is usually the case. Thus, the introduced material has a longer fall path, resulting in an improved interaction between the means for atomization and the introduced Good.

The use of technologies known per se, such as the continuous temperature measurement of the slag bath surfaces, the temperature measurement by infrared or thermal imaging camera and the automatic image processing (by "pixel analyzes", "color analyzes", etc.) can also be an automatic control or regulation be installed, in which the degree of atomization is kept at a predetermined value. In the drawings, embodiments of the invention are shown. Show it:

1 schematically shows an electric arc furnace for melting metallic material, in which material is supplied via a feed device to the working space of the furnace, wherein a first degree of atomization of the supplied material is present,

FIG. 2 is a schematic representation of the situation according to FIG. 1, when there is a higher degree of atomization, FIG.

3 schematically in the illustration according to FIG. 1 the situation when there is an even higher degree of atomization; FIG. 4 schematically in the representation according to FIG. 1 the situation when there is too much local cooling during the supply of material;

FIG. 5 is a schematic representation of the situation according to FIG. 1, when there is a higher degree of atomization in comparison with FIG. 4, FIG.

6 shows the plan view of a part of the working space of the furnace, wherein 2 different configurations are indicated in the supply of material, Fig. 7 shows three different embodiments of the feeding device, wherein the degree of atomization of the material to be supplied is influenced by means of pneumatic elements,

8 shows in the illustration according to FIG. 7 three further embodiments of the feeding device, again influencing the degree of atomization of the material to be supplied by means of pneumatic elements, 9 three different embodiments of the feeding device, wherein the degree of atomization of the material to be supplied is influenced by means of mechanical elements,

Fig. 10 in the illustration of Figure 9 three further embodiments of the feeder, which in turn by means of mechanical elements, the degree of atomization of the material to be supplied is influenced, Fig. 11 in the illustration of Figure 9 further embodiments of the supply device, again by means of mechanical Elements of the degree of atomization of the material to be supplied is influenced, and

Fig. 12 shows three different embodiments of the feeding device, wherein by means of magnetic elements, the degree of atomization of the supplied

Material is affected.

FIG. 1 shows a furnace 2 in which an arc 8 is generated by means of an electrode 9 and melt 1 is thus produced. From the top, several supply devices 3 project into the furnace chamber, via which material 4 to be melted is supplied. If the material 4 impinges on the bath of the melt 1 via the feed devices 3, there is a certain degree of atomization depending on the consistency of the material 4. The indicated here as a dust cone feed region of the material 4 has the consequence that in the area in which the material 4 occurs on the surface of the melt 1, a certain amount of thermal insulation is given. The arrows shown in FIG. 1 indicate how heat from the melt 1 rises upwards.

In Figure 2, the situation is outlined when due to the consistency of the material 4, which is supplied via the feeders 3, a higher degree Atomization is present. The dust cone here is larger. Consequently, there is also less radiation of heat upwards (see arrows).

If the degree of atomization is still higher, as shown in FIG. 3, an even larger dust cone is consequently present. Now even less heat is released upwards (see arrows).

In Figures 4 and 5 is again analogous to Figures 1 and 2 shown how the dust cone depending on the consistency of the material 4 results Now, however, has been achieved by targeted measures that the size of the dust cone, d. H. the type and degree of atomization, was targeted. By way of example, it can be seen in FIG. 6 how the supplied material 4, which was supplied via the feed devices 3, spreads on the surface of the bath of the melt 1. This can be circular or oval depending on the type and degree of atomization.

FIGS. 7 to 12 show in detail the measures mentioned with which the degree of atomization of the supplied material 4 is influenced, by which is meant, in particular, a regulation such that the degree of atomization is influenced such that certain process parameters be complied with within specified limits. In this case, in particular, the temperature in the furnace chamber is thought of, which can be detected and then regulated by the degree of atomization so that a predetermined value is maintained.

In FIG. 7 it can be seen how, in the left partial image, first the material 4 passes through the feeding device 3 without any further measures. In the middle and right part of the picture you can see how pneumatic elements 5 influence the degree of atomization. For this purpose, gas (air, optionally also CO2 or H ₂ ) with a defined speed and a defined angle to the conveyor direction of the material 4 is blown into the jet of the material 4. Both the speed of the gas as well as the direction under which the gas impinges on the beam of the material 4, can be varied. Thus, there is an effective influence on the degree of atomization. In Figure 8 further possibilities are shown how by means of pneumatic elements, ie by adding the gas stream, the degree of atomization of the material 4 is influenced. While the left partial image in turn shows the non-influenced supply of the material 4, in the central partial image in the end region of the supply device 3, a gas jet is supplied from both sides (or from even more sides) to the material 4, so that a relatively large dust cone is produced becomes. In the right-hand part of Figure 8, the addition of the gas takes place essentially in the conveyor direction in the upper region of the feed device 3, so that the degree of atomization is lower. Figure 9 shows the use of mechanical elements 6 to influence the degree of atomization of the material 4. A variable in the fleas stowage element can be positioned so that depending on its fleas, the degree of atomization of the material 4 is varied. While the left partial image in FIG. 9 shows the unaffected supply of the material 4, said element 6 in the middle and right partial image is located once in the middle region of the extension of the delivery device 3 and once in its lower region.

FIG. 10 shows a similar solution when mechanical elements 6 are used, these elements being designed here as baffles or baffles. By their positioning, alignment and shaping again the degree of atomization of the material 4 can be influenced.

The same can be seen in FIG. 11, where a splitter, with which the current or the flow of the material to be supplied is divided, is used as the mechanical element for controlling the atomization. The left and the middle partial image in FIG. 11 show the ones that have not yet been influenced Flow of the material 4, while the effect of said splitter 6 can be seen in the right panel.

Finally, Figure 12 shows the use of magnetic elements 7 for influencing the flow of material 4 through the feeder 3 and thus the degree of atomization of the material 4. However, this presupposes that the conveyed material 4 reacts to magnetic forces.

With the mentioned elements for influencing the flow or the flow of the material 4 to be supplied, a first undisturbed flow can be selectively disturbed and achieved in such a way that the material to be supplied atomizes to the desired extent. In addition, said elements are to be arranged at suitable positions within the flow path of the material to be supplied. The active control of the degree of atomization of the introduced into the process via the feeder in the working space of the furnace material therefore has various advantages:

It can come to no excessive local overload of the furnace with supplied material, which can cause instabilities of the process, excessive cooling or deposits of the material.

More efficient heat exchange between the furnace gases and the feed material is possible, resulting in lower energy requirements per tonne of product, thus increasing energy efficiency.

Reducing the gas temperature in the furnace also reduces the costs that would otherwise be incurred for the cooling of the gas behind the furnace. For this purpose, a correspondingly lower equipment is required. The side walls and ceiling area of the oven are better protected by improved atomization and are less exposed to radiation.

LIST OF REFERENCE NUMBERS

1 melt

2 oven

3 feeder

4 supplied material

5 pneumatic element

6 mechanical element (guide plate) 7 magnetic element

8 arc

9 electrode

Claims

claims:

1. A process for producing a metallic melt (1) in an oven (2), in which metallic material in the working space of the furnace (2) is melted, wherein material to be melted fed via a feed device (3) in the working space of the furnace (2) characterized in that the material (4) fed in via the feed device (3) as it enters the working chamber of the furnace (2) is controlled by pneumatic (5), mechanical (6) and / or magnetic (7) elements as it passes through the feeding device (3) is subjected to a targeted atomization.

2. The method according to claim 1, characterized in that the melting takes place by means of at least one arc (8).

3. The method according to claim 1 or 2, characterized in that the supplied material (4) when passing through the feed device (3) is deflected by at least one gas jet.

4. The method according to claim 3, characterized in that the gas jet is a steel of hydrogen and / or carbon dioxide.

5. The method according to claim 3 or 4, characterized in that the gas jet is changed in its flow rate in order to achieve a defined degree of atomization.

6. The method according to claim 3 or 4, characterized in that the gas jet is changed in its angle of incidence to the flow of the supplied material in order to achieve a defined degree of atomization.

7. The method according to claim 1 or 2, characterized in that the supplied material is deflected when passing through the feed device (3) by at least one baffle (6).

8. The method according to claim 7, characterized in that the position or the position of the at least one guide plate (6) is changed in order to achieve a defined degree of atomization.

9. The method according to claim 7, characterized in that the shape of the at least one guide plate (6) is changed in order to achieve a defined degree of atomization.

10. The method according to claim 1 or 2, characterized in that the supplied material is deflected when passing through the feed device by at least one magnet (7).

11. The method according to any one of claims 1 to 10, characterized in that the atomization in the closed loop is such that a defined degree of atomization during introduction of the material via the feed device (3) is present.