JPH06128616A - Method and device for supplying granular substance supporting iron into metallurgical furnace - Google Patents

Abstract

PURPOSE: To decrease the number of opening and closing times of a furnace cap and to produce molten steel with good productivity at an excellent furnace working rate and raw material yield by using a supply pipe which is freely advanceable and retreatable at a specific angle into and out of a furnace at the time of supplying a granular ion raw material into the arc furnace for steel making.

CONSTITUTION: Molten steel is produced by forming an arc 22 between the molten slag 20 on the molten iron 18 within the hermetic type arc furnace 10 consisting of a roof (furnace cap) 14 and a crucible part 16 and having three graphite electrodes 32, thereby heating and refining the raw materials in the furnace. The prereduced iron ores or the like as the raw materials are fed from a conduit 62 via a storage device 58 to a screw supplying machine 40 and are supplied in a deposited form 52 onto the molten slag 20 in the furnace from the front end in the state inclining at an angle of 10 to 45° from the horizontal to prevent the erosion of the front end of the supplying machine 40 by the heat of the arc. At the time of supplying the molten pig iron to the arc furnace 10 or discharging the molten slag 20 in the furnace, the supplying machine 40 is retreated to the position outside 45 the furnace by an air cylinder 44 and thereafter the supply of the pig iron or the slag discharge is executed by opening the furnace cap 14 and, therefore, the number of times thereof is decreased and the working rate of the furnace is improved.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a technique for supplying iron-bearing substances to a steelmaking metallurgical furnace, and in particular, for example, pre-reduced iron ore ingots, pre-reduced iron ore pellets, TECHNICAL FIELD The present invention relates to a method and apparatus for adding particles carrying iron, such as direct reduced iron (DRI), also called sponge iron, scrap, etc., into an electric steelmaking furnace.

[0002]

BACKGROUND OF THE INVENTION The harsh and severe operating conditions of steelmaking furnaces, the problems inherent in high temperatures and processed molten metals, and the enormous production rates, make the furnace demand for steel as well as solid or liquid forms of metallic iron fillings. It makes it difficult to propose an efficient method and apparatus for charging the various additives necessary for refining molten iron to obtain the desired composition and properties.

The present invention is referred to herein as an electric arc furnace (EA).
Although described as applied to the feeding of DRI to F), it will be understood that the invention can be modified to readily be applied to other types of furnaces and materials.

Many EAF delivery methods have been proposed and tested for many years. In the early days of electric arc steelmaking, such furnaces were essentially filled with scrap using large buckets. The furnace was opened by oscillating away from the furnace roof and electrodes, and the bucket was placed on the furnace with a head crane, and the scrap was thrown into the furnace by opening the bottom of the bucket.

Due to the large amount of scrap, when the first charge melts, the furnace must be reopened and the second charge must be added to the furnace. When this second filling melts,
The furnace needs to be opened and filled a third time.

This method has a number of drawbacks, in particular a considerable amount of energy is lost due to radiation from the roof, the electrodes and the metal bath at each release, and the furnace for each bucket of scrap or pre-reducing material. The productivity of the furnace was very limited because of the working time required to open and fill.

In recent years, many improvements have been made to the EAF steelmaking practice, and as a result, productivity has increased considerably. These improvements include the use of ultra high power for the furnace, which optimizes the overall melting operation of the furnace and the refining and submetallurgical operations are carried out in separate ladle furnaces.

The continuous filling of scrap or pre-reduced material further increased the productivity of EAF. The iron bearing material is continuously added to the furnace while the first charge is molten to avoid crane working time.

Many methods have been proposed for continuously filling the EAF. These can be classified into three general categories: One method is to feed iron particles to the EAF by dropping them through holes in the roof of the EAF. An example of this method is described in J. G. Shibakin (Sib
akin) et al., U.S. Pat. No. 3,472,650. Shivakin teaches a method of continuously feeding separated iron-bearing material to an electric arc furnace where the iron-bearing material is fed through a hole in the furnace roof using a suitable chute. Let it fall. One object of the invention is to stabilize the electric arc by balancing the filling rate with the power level provided to the furnace.

M. J. Udy U.S. Pat. No. 2,805,930 is similar to Shivaquin, but its main purpose is to shield the furnace wall with the iron-bearing particles that are to be melted. For this purpose, iron-bearing particles are dropped from an opening in the roof of the furnace near the furnace wall.

This method of feeding the EAF has serious drawbacks. For example, the yield of molten iron produced from the fill is affected by the fact that the iron-bearing particles carry and carry the gas generated in the furnace. This iron loss will be up to about 1%. This loading problem is even more significant due to the widespread use of pollution control devices for the treatment of EAF smoke, since all these gases are drawn into the treatment equipment and the resulting stronger gas flow inside the EAF. It is starting to become a thing. Also,
Fine particles that tend to float on the slag furnace due to their lightness make it difficult to penetrate the slag layer and reach the molten bath.

A method of feeding iron-bearing material through the walls of the EAF has also been proposed for the primary purpose of filling the material near the arc while avoiding the problems associated with feeding the material through the roof near the electrodes. Was there.

An example of a supply for this type of EAF is R.S. E. Pellegrini et al. U.S. Pat. No. 3,
462,538, J. Celada No. 3,681,049, and C.I. R. Kuzel
No. 2,657,990, and G.L. A. Canadian Patent No. 847,45 to Raeder et al.
No. 4 is disclosed.

The Pellegrini patent EAFs sponge iron particles
A method and apparatus for continuous filling therein is described, in which sponge iron particles are injected by providing the furnace with sufficient energy to push them near the electrodes.

The Cerada patent discloses a similar system for injecting sponge iron particles into a furnace using a centrifugal slinger consisting of a drive belt and a play. Sponge iron particles are injected near the arc. 4 cerada patents
Also shown in the figure is another means for practicing his invention, namely a fill tube for accelerating the particles with a compressed fluid such as gas, air or water vapor.

The Kusel patent describes a delivery system similar to that described in the Celada patent.

The Radar patent also describes a feed system in which iron-bearing particles are injected into the furnace by blowing air through an opening in the furnace wall.

It has also been proposed to feed the EAF through the wall and near the surface of the liquid metal or usually the slag covering the liquid metal. An example of such a method is
G. J. Stock US Pat. No. 1,33
No. 8,881. The Stock patent discloses a method of feeding an electric furnace using a feed groove through which an iron charge is extruded into the furnace by a piston driven by a crank wheel. The crank wheels are rotated by an electric motor, and the motor speed is adjusted to balance the input of electrical energy with the amount of material to be melted for the general purpose of maintaining a constant temperature in the furnace. ing.

A system similar to the Stock patent but for the production of calcium carbide is described in W. B. Rogats (Rog
atz) in U.S. Pat. No. 1,422,135. The Rogats patent discloses a method for feeding a substance into an electric furnace, preferably horizontally, through an opening in a furnace wall and onto a molten substance in the furnace, the piston feeding the substance into the furnace. Forced injection causes the material to be widely distributed across the surface of the molten material. The piston is manufactured from carbon and operates in a similar manner to the device shown by the Stock patent.

Harwell US Pat. No. 4,225,745 describes a method of directly filling small particles of iron and steel into molten metal in an arc furnace. The Harwell patent teaches a method of filling iron oxide, such as mill scale, directly into the bath through a subdivision pipe. The bath is manufactured in a furnace in a conventional manner by filling the appropriate material through the top of the furnace.

The furnace has a feed chute that enters the furnace well below the normal full metal level. A feed chamber is provided for adding large amounts of iron or steel small particles to the feed chute. A piston pushes the particles into the melting furnace. It will be appreciated that the Harwell patent's filling system is very similar to the stock patent, but with different level positions in the furnace.

At column 4, lines 22-29, the Harwell patent states that a screw feed is possible, but he does not teach such a use due to possible freezing. Even his own feeding system with carbon-containing pellets (due to the high temperatures that would occur) does not teach the use. In contrast, the present invention is well suited to feed pellets of any carbon content, as the pellets are fed to the top of the bath rather than directly into the molten metal bath.

Direct feed screws are not suitable because the molten metal may solidify in the feed chute due to the freezing problem described by the Harwell patent. In the present invention, Applicants uniquely propose that only the slag will contact the feeder tip. Since it is known that solid slag is not as strong as iron or steel, direct feed screw conveyors can be used in such a way that they offer many advantages, which makes the present invention very useful.

Another category of feeding system is the actual use of screw type feeders. These examples are
R. A. US Pat. No. 1,421,185 to Driscoll, both E.I. G. T. Gustafsson No. 1,871,848
And No. 1,902,638.

The Doriskor patent shows a screw-type feeder in an electric furnace which is placed on a molten metal bath for feeding powdered fuel. However, the iron-bearing material is dropped separately from the top of the furnace roof. Details of the joint operation of the fuel supply and the furnace are not shown,
It can be deduced from the drawing that the furnace is fixed and the feeder is fixedly connected to the furnace wall.

The Gustavson patent discloses a method of melting metal in an electric furnace in which the metallic material is continuously fed to the furnace during the heating process.

The Gustavson patent also teaches a method of feeding sponge iron to the furnace, and he is also aware of the problem of floating sponge iron in the slag layer. However, the method he proposes to overcome this problem does not increase the density of the material and applies a reliable power to the material in the direction of the molten bath by the feeder.

Although the Gustavson patent does not disclose the use of screw type feeders, they are not directed to the molten bath and are employed to apply downward force to the material to replenish gravity. It is understood that it is not. The operation of the Gustavson feeder is the same as dropping it from the top. These screws do not force the material out of the hopper but in a defined direction directly into the molten bath and / or through the slag layer. The screw type feeder is L. D. Areax US Pat. No. 4,872,90
It is also shown in No. 7 for filling a molten extrudate and a piece of metal that is resistant to the molten metal object and consists of a distribution conduit immersed in the molten metal bath into the molten bath. Teaching methods and apparatus. Although the supply system of the Areaux patent is described as generally applicable to any metal, he states in column 13, lines 23-30 that the invention is non-magnetic, such as brass, aluminum, aluminum alloys, etc. It notes that it is used in connection with metal scrap. It will be appreciated that it is difficult to fabricate this type of feeder soaked in molten steel. For this reason, the Areaux patent has applied his system to iron and the above metals other than steel.

It will be appreciated that the prior art does not disclose a DRI delivery system for a metallurgical furnace which provides the advantages of the invention described herein.

[0030]

Accordingly, one object of the present invention is to provide a method and apparatus for feeding an iron-bearing material to an EAF such that the productivity of the EAF is increased. Is.

Another object of the present invention is to provide a method and apparatus for feeding the iron bearing material to the furnace near the slag layer covering the metal bath in the furnace.

Another object of the present invention is to send the iron-bearing material into the pneumatic transport system and to allow all fines and debris produced in the pneumatic transport device to be fed into the EAF. It is an object of the present invention to provide a method and an apparatus in which the overall operation can be performed economically.

Other objects of the invention will be in part apparent and in part pointed out hereinafter.

[0034]

A molten iron holding vessel having a wall extending above the molten iron, preferably a screw type feeder installed outside the vessel, the feeder passing through the interior of the vessel. A feed port in the wall that is formed so that it is positioned at a height above the molten iron such that molten material does not exit the furnace through the port during normal furnace operation and operation. The mold feeder is extended from a retracted position outside the container to an advantageously adjustable extension position inside the container, thereby filling the iron-bearing particles near but slightly above the molten iron. The object and advantages of the present invention are generally obtained by providing a method and an apparatus for feeding iron-bearing particles into an electric arc furnace, the method comprising: Particle is slur Exactly extruded into the molten iron through the bed, and preferably producing a deposit of material extruding just above the slag layer, and even in the hottest zone of the furnace, extruded against the arc of the feeder. The tip is shielded and protected from excessive heat. Advantageously, at least a portion of the tip of the feeder extends into the slag layer and feeds adjacent and near the upper surface of the metal bath.

The present invention will be described here for reference.
It is particularly useful to use the novel pneumatic delivery system described in our co-worker US patent application Ser. No. 07/526189, filed May 18, 1990.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, numeral 10 generally indicates an electric arc furnace having a wall portion 12, a roof 14 and a crucible portion 16, the bottom of which is usually covered by a slag layer 20. It is adapted to hold a molten iron bath 18 which is An internal volume 2 for the wall 12 to enclose the filler material being melted and to contain the gas emitted during the emission of the arc 22 and the melting and refining process.
4 is forming. Normally, this wall section is formed by the refractory laminated water-cooled panel 13 and saves refractory material previously used rather than cooling.

The roof 14 has openings for free movement and adjustment of the electrodes 32, which are typically arranged in a triangle in a furnace operating with varying current supplies. Three electrodes and one electrode in the DC furnace. The other openings 34 and 36 allow smoke to be extracted and the iron-bearing material to be continuously fed through the roof.

The screw-type feeder 40 is installed outside the furnace 10 and it is supported by the structure 42. On the structure 42, the feeder 40 is moved from the retracted position 46, symbolized by a dotted line, outside the furnace, to the operating position 48 by actuating means such as an air cylinder 44. The retractable characteristic of this feeder 40 is EAF
It is very useful in the operating environment because the feeder 4
This allows for free slag removal and free movement and work of the furnace for steel injection without the risk of damaging the zero. The solid slag is not very solid and can be destroyed by the normal force of the feeder, so that the slag can strike the tip of the feeder without problems. However, contact with molten iron should be avoided and this is why the operating position of the feeder 40 must be selectively adjusted.

In order to precisely impart a force to the iron-bearing material in the direction of the molten bath and into the bath, the feeder 40 is level in the furnace through an opening 50 in the wall 12. In contrast, it is applied at an angle within the range of 10-45 °. The addition of the feeder 40 at an angle with respect to the horizontal contributes to an important feature of the invention: the iron bearing material is fed very close to the molten iron bath while the molten iron is at the same time the EAF operation. It prevents the furnace from overflowing.
The ability of the iron-bearing material to be arranged to extend downwards in the slag bed substantially reduces the loss of fine particles in the gas leaving the furnace and increases its productivity. This feature is generally associated with brittle materials such as DRI, which is also referred to as sponge iron, which is being transported to a molten store by a conveyor belt, by a crane operating bucket that is filled by gravity, or more recently by an air system. It becomes even more important when handling. That is,
The initial treatment of DRI and subsequent handling destroys some of the particles and partially breaks them, thereby producing fines.

Deposits 52 of iron-bearing material generally form with DRI and plunge into the slag layer and at the same time overflow onto the slag layer 20, causing the tip of the feeder 40 to radiate from the arc 22. Protected from overheating. The retention of this deposit 52 also prevents fine particles of the iron-bearing material from being carried by the gas and smoke out of the furnace through the openings 34 and the collection tubes 56.

The iron-bearing material, such as DRI, is transferred by a suitable conduit 62 to a funnel or reservoir 58 and then via chute 60 into feeder 40, which chute 60 and it. The funnel or reservoir 58 may or may not be connected to the conduit 62 and the feeder 40 is retracted to the non-operating position 46 outside the EAF. During maintenance of the feeder 40, the conduit 62 may be repositioned to provide the opening 36 as an ad-hoc means of continuous feeding to the EAF.

Referring now to FIG. 2, which shows a diagram of the structure of a screw-type feeder, the numeral 40 generally indicates the feeder, which is associated with a feed tube 60 near the upper end below. It includes an angled cylindrical housing 72. A shaft 76 is rotatably installed in the housing 72. The shaft has a screw-type spiral blade 78 which pushes particulate matter received from the chute 60 through the feeder 40 to the lower discharge end and which is supported by bearings 80 and 82. . The bearing 80 is located within the housing at a sufficient distance from the lower end facing the EAF interior so that it is protected from the heat of the furnace. Housing 7
2 and the lower end of the shaft 76 and the screw blade 78 can advantageously be made of a metal, all of which is more heat resistant compared to the rest of the feeder. The lower bearing 80 may be omitted in some applications.

Shaft 76 is driven by drive means 84, such as a high torque air motor and a suitable speed reducer, and engages the shaft through coupling device 86 in a manner well known in the art.

The housing 72 is cooled by the circulation of a fluid, such as water, which descends beneath the inner surface of 72 away from the inlet 92 through the passageway 90 and away from the lower tip to the lower tip. , 72 away
Directly below the outer surface of the and up, and exit through exit 94. Radiation from the furnace during operation and high temperature (450 ° C-
An expansion connection 96 is provided to allow expansion of the housing 72 due to temperature increase caused by radiation from the iron-bearing material during filling.

From the above it is clear that the feeder for the metallurgical furnace added to the present invention provides several of the above advantages. The structure of the feeder allows the iron-bearing material to be added accurately through the conduit to a point very close to the molten iron bath without the loss of the iron equipment, thereby increasing the overall productivity of the furnace. Increase. The exact extrusion that the screw-type feeder applies to the material extrudes it in the direction of the molten bath, causing the particles to penetrate the slag layer and also the arc of the furnace, which is the highest temperature zone, It makes the operation more efficient and adjustable. Fines and small particles tend to concentrate in the lower part of the feeder and they are protected from gas flow inside the furnace by relatively large particles, thus contributing to an increase in the overall yield of the furnace. There is. Due to the retractability of the feeder, it is placed very close to the top surface of the iron bath, even if the furnace level fluctuates during operation of the furnace, and the furnace is operated for deslagging or for injection of molten iron. When allowed to act, it acts to protect it from contact with the molten iron. In a broad aspect of the invention, the screw feeder 40 may be replaced by an extruded rod, such as in US Pat. No. 1,422,135, in which case power is used in addition to gravity to remove particles. It has been modified to extrude downwards into the slag layer.

It should be understood, of course, that the embodiments of the invention described herein are illustrative, and those skilled in the art in these illustrative embodiments do not depart from the scope of the invention. Obviously many modifications can be made.

[Brief description of drawings]

FIG. 1 shows a partial schematic view of the general arrangement of an electric arc furnace shown in vertical cross section and includes a preferred embodiment of the invention in the form of a screw-type feeder for DRI.

FIG. 2 shows a more detailed schematic view of the screw feeder, which is also in vertical section, showing its main characteristics and the cooperation of its parts for the purposes of the invention.

[Explanation of symbols]

 10 arc furnace 12 wall 13 fireproof laminated water-cooled panel 14 roof 16 pot part 18 molten iron bath 20 slag layer 22 arc 24 inner layer 32 electrode 40 screw type feeder 42 structure 44 air cylinder 52 deposit 56 collection pipe 58 storage 60 Chute 62 Conduit 72 Housing 76 Shaft 78 Screw-type spiral blade 80 Bearing 84 Driving means 90 Passage 92 Inlet 94 Outlet 96 Expansion connection

Claims (8)

[Claims] 1. A metallurgical furnace of the type containing a bath of liquid iron and a layer of slag covering the bath and having an upper side wall above the slag for containing gas, radiant heat, etc. In a method of feeding iron-bearing particulate matter, a bath of molten iron and an upper slag layer is produced in a furnace, and the lower distributor end of the extending feeder is provided with a hole in the upper side wall of the furnace. Through a slag layer at least adjacent to an operating position adjacent to the slag layer, the iron-bearing particulate matter is extruded by a feeder into the slag layer in the direction of the molten iron bath, and the charge is melted in the furnace. Method for feeding iron-bearing particulate matter in a metallurgical furnace characterized by the steps of continuously charging iron-bearing particles into molten iron through a feeder at approximately the same rate . 2. The furnace is an electric arc furnace, the iron-bearing material is sponge iron, and for at least partially protecting the feeder from the liquid metal in the furnace and the heat radiated by the arc. 2. A method according to claim 1, characterized in that a deposit of particulate material bearing iron is produced and held in the front of the feeder. 3. The feeder is a screw feeder and it keeps the dispensing end of the feeder always above the liquid iron bath and at least adjacent to the slag bed during feeding, which is the varying level of the molten bath. Method according to claim 2, characterized in that it is adjustably arranged in the furnace in relation to. 4. The method according to claim 3, characterized in that the dispensing end of the feeder is at least partially immersed in the slag layer during the feeding of the iron-bearing particulate material to the bath. 5. A generally cylindrical housing, a shaft rotatably mounted within the housing and having a screw-type spiral blade for pushing particulate matter through a feeder to a lower discharge end. Driving means for rotating the shaft in the feeder, as well as pushing the discharge end of the feeder at a varying distance above and sufficiently close to the level of the molten iron bath to push the substance through the slag layer into the bath. And comprising an actuating means for retracting the feeder from an operating position inside the furnace to a non-operating position outside the furnace, so that in the latter position the feeder does not interfere with normal operation of the furnace and other operating tasks. And a mold containing a bath of liquid iron and a layer of slag covering the bath, the axis being inclined with respect to the horizontal at an angle sufficient to reliably push the particles into the slag layer. For supplying iron-bearing particulate matter into a metallurgical furnace of. 6. Device according to claim 5, characterized in that the axis is inclined at least 10 ° with respect to the horizontal. 7. Device according to claim 5, characterized in that the axis is inclined at 30 ° -45 ° with respect to the horizontal. 8. A device according to claim 6, characterized in that the lower discharge part of the housing has a water cooling jacket.