DE102017220655A1 - Process for producing a metallic melt in an oven - Google Patents

Abstract

The invention relates to a method 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 via a feed device (3) into the working space of the furnace (2 ) is supplied. In order to achieve an improved energy efficiency, a better protection of the furnace and a higher process stability, the invention provides that the material (4) fed in via the feed device (3) as it enters the working space of the furnace (2) by pneumatic (5) , mechanical (6) and / or magnetic (7) elements when passing through the feed device (3) is subjected to a targeted atomization.

Description

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 discloses the DE 696 22 587 T2 , Similar solutions show the JP 3291353 A , the JP 2000119720 A and the 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. An example is the production of FeCr in DC furnaces. 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. on 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. This can cause process disturbances.

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 the object of a method of the type mentioned in such a way that 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 of this object by the invention is characterized in that the material supplied via the feeding 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 feeding 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 can be provided that the gas jet is varied in its flow rate to achieve a defined level 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.

It is therefore particularly preferred that it is checked by detecting corresponding process parameters whether the process runs optimally and then the degree of atomization of the supplied material is influenced in the closed control loop in order 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.

• 1 schematisch einen Lichtbogenofen zum Aufschmelzen metallischen Materials, bei dem Material über eine Zuführvorrichtung dem Arbeitsraum des Ofens zugeführt wird, wobei ein erster Grad an Zerstäubung des zugeführten Materials vorliegt,
• 2 schematisch in der Darstellung nach 1 die Situation, wenn ein höherer Grad an Zerstäubung vorliegt,
• 3 schematisch in der Darstellung nach 1 die Situation, wenn ein noch höherer Grad an Zerstäubung vorliegt,
• 4 schematisch in der Darstellung nach 1 die Situation, wenn bei der Zufuhr von Material eine zu hohe lokale Kühlung vorliegt,
• 5 schematisch in der Darstellung nach 1 die Situation, wenn im Vergleich zu 4 ein höherer Grad an Zerstäubung vorliegt,
• 6 die Draufsicht auf einen Teil des Arbeitsraums des Ofens, wobei 2 unterschiedliche Ausbildungen bei der Zufuhr von Material angedeutet sind,
• 7 drei verschiedene Ausgestaltungen der Zuführvorrichtung, wobei mittels pneumatischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird,
• 8 in der Darstellung gemäß 7 drei weitere Ausgestaltungen der Zuführvorrichtung, wobei wiederum mittels pneumatischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird,
• 9 drei verschiedene Ausgestaltungen der Zuführvorrichtung, wobei mittels mechanischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird,
• 10 in der Darstellung gemäß 9 drei weitere Ausgestaltungen der Zuführvorrichtung, wobei wiederum mittels mechanischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird,
• 11 in der Darstellung gemäß 9 weitere Ausgestaltungen der Zuführvorrichtung, wobei wiederum mittels mechanischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird, und
• 12 drei verschiedene Ausgestaltungen der Zuführvorrichtung, wobei mittels magnetischer Elemente der Grad der Zerstäubung des zuzuführenden Materials beeinflusst wird.

In the drawings, embodiments of the invention are shown. Show it:

• 1 schematically an arc furnace for reflowing metallic material, wherein the 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,
• 2 schematically in the illustration after 1 the situation when there is a higher degree of atomization,
• 3 schematically in the illustration after 1 the situation when there is an even higher degree of atomization,
• 4 schematically in the illustration after 1 the situation when there is too much local cooling during the supply of material,
• 5 schematically in the illustration after 1 the situation when compared to 4 there is a higher degree of atomization,
• 6 the plan view of a part of the working space of the furnace, with 2 different Training in the supply of material are indicated,
• 7 three different embodiments of the feed device, wherein the degree of atomization of the material to be supplied is influenced by means of pneumatic elements,
• 8th in the illustration according to 7 three further embodiments of the feeder, which in turn is influenced by means of pneumatic elements, the degree of atomization of the material to be supplied,
• 9 three different embodiments of the delivery device, wherein the degree of atomization of the material to be supplied is influenced by means of mechanical elements,
• 10 in the illustration according to 9 three further embodiments of the delivery device, wherein again by means of mechanical elements, the degree of atomization of the material to be supplied is influenced,
• 11 in the illustration according to 9 Further embodiments of the feeder, which in turn is influenced by means of mechanical elements, the degree of atomization of the material to be supplied, and
• 12 three different embodiments of the feeding device, wherein by means of magnetic elements, the degree of atomization of the material to be supplied is influenced.

In 1 is a stove 2 represented in which by means of an electrode 9 an arc 8th produced and so melt 1 will be produced. From above, several feeding devices protrude into the oven cavity 3 , about the material to be melted 4 is supplied. Meets the material 4 via the feeders 3 to the bath of the melt 1 depends on the consistency of the material 4 a certain degree of atomization. The supply area of the material indicated here as a dust cone 4 As a result, in the area where the material 4 on the surface of the melt 1 occurs, some thermal insulation is given. By the in 1 shown arrows is indicated, as far as heat from the melt 1 goes up.

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

The degree of atomization is even higher, as it is 3 shows, therefore, there is an even larger dust cone. Now even less heat is released upwards (see arrows).

In the 4 and 5 is once again analogous to the 1 and 2 shown how the dust cone depends on the consistency of the material 4 results. Now, however, has been achieved by targeted measures that the size of the dust cone, ie the type and degree of atomization, has been specifically adjusted. This is in 6 to recognize how the supplied material 4 That's about the feeders 3 was fed to the surface of the bath of the melt 1 spreads. This can be circular or oval depending on the type and degree of atomization.

In the 7 to 12 The above measures are to be seen in detail, with which the degree of atomization of the supplied material 4 This is to be understood as meaning, in particular, a regulation such that the degree of atomization is influenced in such a way that certain process parameters are maintained within predetermined 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 7 you can see, as in the left part of the picture, first the material 4 without further action the feeder 3 happens. In the middle and right part of the picture you can see how about pneumatic elements 5 the degree of atomization is affected. For this purpose, gas (air, possibly also CO ₂ or H ₂ ) with a defined speed and a defined angle to the conveyor direction of the material 4 in the beam of the material 4 blown. Both the velocity of the gas and the direction under which the gas hits the jet of material 4 hits, can be varied. Thus, there is an effective influence on the degree of atomization.

In 8th Further possibilities are shown, such as by means of pneumatic elements, ie by adding the gas stream, the degree of atomization of the material 4 being affected. While the left part of the picture again the unaffected supply of material 4 is shown in the middle field in the end of the feeder 3 a gas jet from both sides (or even more sides) of the material 4 fed, so that a relatively large dust cone is generated. In the right part of the picture in 8th 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.

9 shows the use of mechanical elements 6 to influence the degree of Atomization of the material 4 , A variable height baffle can be positioned so that, depending on its height, the degree of atomization of the material 4 is varied. While the left part of the picture in 9 the unaffected supply of the material 4 shows, is said element 6 in the middle and in the right field once in the middle region of the extension of the feeder 3 and once in its lower part.

In 10 is a similar solution when using mechanical elements 6 to see, with these elements are designed here as baffles or baffles. By their positioning, alignment and shaping can in turn the degree of atomization of the material 4 to be influenced.

Similar is in 11 to recognize where a splitter is used as a mechanical element for controlling or regulating the atomization, with which the current or the flow of the material to be supplied is divided. The left and the middle part in 11 shows here the not yet influenced flow of the material 4 while the effect of said splitter 6 can be seen in the right part of the picture.

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

With the mentioned elements for influencing the flow or the flow of the material to be supplied 4 can targeted disturbed initially undisturbed flow and be achieved so that the supplied material atomized to the desired extent. For this purpose, 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 (baffle)

7

magnetic element

8th

Electric arc

9

electrode

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 69622587 T2
• JP 3291353 A [0002]
• JP 2000119720 A [0002]
• CN 203595403 U [0002]

Claims (11)

Method for producing a metallic 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 via a feed device (3) into the working space of the furnace (2), characterized in that the material (4) supplied via the feed device (3) as it enters the working space of the furnace (2) is controlled by pneumatic (5), mechanical (6) and / or magnetic (7) elements as it passes through the feed device (3 ) is subjected to a targeted atomization. Method according to Claim 1 , characterized in that the melting takes place by means of at least one arc (8). Method according to Claim 1 or 2 , characterized in that the supplied material (4) is deflected when passing through the feed device (3) by at least one gas jet. Method according to Claim 3 , characterized in that the gas jet is a steel of hydrogen and / or carbon dioxide. 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. 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. 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 guide plate (6). Method according to Claim 7 , characterized in that the position or the position of the at least one baffle (6) is changed in order to achieve a defined degree of atomization. Method according to Claim 7 , characterized in that the shape of the at least one baffle (6) is changed to achieve a defined degree of atomization. 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). Method according to one of Claims 1 to 10 , characterized in that the atomization in the closed loop is such that there is a defined degree of atomization during introduction of the material via the feed device (3).

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