JP2021046608A - Method for manufacturing molten iron by electric furnace - Google Patents

Abstract

To provide a method for melting a cold iron source in an electric furnace and manufacturing a molten iron which manufactures a molten iron in an electric power consumption rate lower than a conventional method without using a special facility and an expensive heat source.SOLUTION: A method for preheating a cold iron source by passing exhaust gas generated in a melting chamber 1 through a preheating chamber 2 to which the cold iron source is supplied in an electric furnace provided with the melting chamber 1 for melting the cold iron source by arc heating and the preheating chamber 2 for preheating the cold iron source supplied to the melting chamber 1, supplying the preheated cold iron source to the melting chamber 1, melting the supplied cold iron source in the melting chamber 1 and obtaining a molten iron includes: mixing waste oil with the cold iron source; and preheating the cold iron source mixed with the waste oil in the preheating chamber 2. Since heat can be applied to the cold iron source and the molten iron side by the waste oil mixed with the cold iron source, an electric power consumption rate for melting the cold iron source and obtaining the molten iron can be reduced.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing molten iron by melting a cold iron source in an electric furnace.

In an electric furnace, molten iron is produced by melting a cold iron source such as scrap with arc heat, but a large amount of electric power is consumed to generate arc heat. Conventionally, in order to reduce power consumption in an electric furnace, a method of preheating a cold iron source before melting with a burner using fossil fuel, a method of preheating a cold iron source with high-temperature exhaust gas generated during melting, A method such as blowing coke as an auxiliary heat source is adopted.

For example, Patent Document 1 discloses a technique of heating (preheating) a cold iron source with a burner called a combustion assist burner in a melting chamber to promote heating and melting of the cold iron source.
Further, in Patent Document 2, as a method of preheating the cold iron source with the high temperature exhaust gas generated during melting, the preheating chamber of the cold iron source is connected to the upper part of the melting chamber, and the high temperature exhaust gas generated in the melting chamber is used. , A method is shown in which the cold iron source is preheated by passing it through a preheating chamber filled with the cold iron source so that the preheated cold iron source is supplied to the melting chamber. Further, in the method of Patent Document 2, coke is blown into the melting chamber and used as an auxiliary heat source.

Japanese Unexamined Patent Publication No. 63-93816 Japanese Unexamined Patent Publication No. 10-292990

The method of Patent Document 1 is effective for heating a cold iron source existing in a cold spot in a melting chamber, but is not sufficient as a method for preheating the entire cold iron source, and consumes power in an electric furnace. No significant effect can be expected on suppression. In addition, since it costs equipment costs to install fuel and oxygen pipes for the burner to install the combustion auxiliary burner, the equipment configuration should be such that the preheating effect of the cold iron source by the combustion auxiliary burner can be sufficiently obtained. Requires a large amount of equipment costs.
On the other hand, the method of preheating the cold iron source with the furnace exhaust gas as described in Patent Document 2 is advantageous in that the exhaust gas is used as an energy source, but this alone is not sufficient to significantly reduce the electric power intensity. It is enough. The same applies to the method of using the coke blowing described in the same document together.

Therefore, an object of the present invention is lower than that of the conventional method in a method of solving the above-mentioned problems of the prior art and melting a cold iron source in an electric furnace to produce molten iron without using special equipment. The purpose is to provide a method capable of producing molten iron on an electric power basis.

As a result of repeated studies on a method capable of solving the above problems, the present inventors have found that in a method of preheating a cold iron source with furnace exhaust gas (high temperature exhaust gas generated in a melting chamber of an electric furnace) in a preheating chamber. By mixing waste oil with a cold iron source and preheating the cold iron source mixed with this waste oil in a preheating chamber, heat can be added to the cold iron source and molten iron by utilizing the calorific value of the waste oil. It was found that the power intensity can be effectively reduced.
The present invention has been made based on such findings, and the gist of the present invention is as follows.

[1] In an electric furnace equipped with a melting chamber (1) for melting a cold iron source by arc heating and a preheating chamber (2) for preheating the cold iron source supplied to the melting chamber (1), the melting chamber. The exhaust gas generated in (1) is preheated by passing through the preheating chamber (2) to which the cold iron source is supplied, and the preheated cold iron source is supplied to the melting chamber (1). It is a method of obtaining molten iron by melting in the melting chamber (1).
A method for producing molten iron by an electric furnace, which comprises mixing waste oil with a cold iron source and preheating the cold iron source mixed with the waste oil in a preheating chamber (2).
[2] In the production method of the above [1], the cold iron source is preheated in a state of being filled in the preheating chamber (2), and the preheated cold iron source is sequentially supplied to the melting chamber (1). A method for producing molten iron using an electric furnace.

[3] In the manufacturing method of the above [2], a preheating chamber (2) is provided in the upper part of the melting chamber (1) at a position away from the arc heating portion so as to communicate with the melting chamber (1), and the preheating chamber (2) is provided. In producing molten iron in an electric furnace having a cold iron source inlet (20) at the top of the chamber (2).
The cold iron source charged into the preheating chamber (2) from the cold iron source charging inlet (20) is filled in the space portion (1a) of the preheating chamber (2) and the melting chamber (1) below it. A method for producing molten iron by an electric furnace, wherein the cold iron source of the space portion (1a) is sequentially extruded to the arc heating portion side.
[4] In the production method of the above [3], a method for producing molten iron by an electric furnace, wherein the cold iron source of the space portion (1a) is sequentially extruded to the arc heating portion side by the extruder (3).

[5] In the production method of the above [1], the cold iron source is preheated while being transferred by the transfer means (17) in the preheating chamber (2), and the preheated cold iron source is transferred from the transfer means (17) to the melting chamber. A method for producing molten iron by an electric furnace, which is characterized in that the iron is sequentially supplied to (1).
[6] In any of the above-mentioned production methods [1] to [5], electricity is characterized by mixing waste oil having a calorific value of 2 Mcal or more and 50 Mcal or less per ton of a cold iron source with a cold iron source. A method for producing molten iron in a furnace.
[7] In any of the above-mentioned production methods [1] to [6], the waste oil mixed with the cold iron source is molten iron produced by an electric furnace, which contains water and / or solid content together with oil. Manufacturing method.

[8] In the production method of the above [7], a method for producing molten iron by an electric furnace, wherein the waste oil containing solid content is oil-containing sludge.
[9] In any of the above-mentioned production methods [1] to [6], the waste oil mixed with the cold iron source removes a part of the water from the used lubricant in the rolling process of the metal material or the used lubricant. A method for producing molten iron by an electric furnace, which is characterized by being separated and removed.
[10] In any of the above-mentioned production methods [1] to [9], production of molten iron by an electric furnace is characterized in that the temperature of the exhaust gas when exhausted from the preheating chamber (2) is 400 ° C. or higher. Method.

[11] In an electric furnace equipped with a melting chamber (1) for melting a cold iron source by arc heating and a preheating chamber (2) for preheating the cold iron source supplied to the melting chamber (1), the melting chamber. The exhaust gas generated in (1) is preheated by passing through the preheating chamber (2) to which the cold iron source is supplied, and the preheated cold iron source is supplied to the melting chamber (1). When melting in the melting chamber (1) to obtain molten iron
A method for treating waste oil, which comprises mixing waste oil with a cold iron source and preheating the cold iron source mixed with the waste oil in a preheating chamber (2).

[12] The method for treating waste oil according to the above [11], wherein the waste oil mixed with the cold iron source is waste oil containing water and / or solid content together with oil.
[13] The method for treating waste oil according to the above [12], wherein the waste oil containing solid content is oil-containing sludge.
[14] In the treatment method of the above [11], the waste oil mixed with the cold iron source is the used lubricant in the rolling process of the metal material or a part of water is separated and removed from the used lubricant. A method for treating waste oil, which is characterized by.

According to the present invention, in a method of preheating a cold iron source with furnace exhaust gas (high temperature exhaust gas generated in a melting chamber of an electric furnace) in a preheating chamber, waste oil is mixed with the cold iron source, and the waste oil is mixed with the cold iron. By preheating the source in the preheating chamber, heat can be added to the cold iron source and molten iron by using the calorific value of the waste oil, so the power source is lower than the conventional method without using special equipment. Molten iron can be produced at low cost in units.
Further, according to this method, waste oil containing a large amount of water or waste oil containing solids such as oil-containing sludge can be used as it is, so that the waste oil can be used as a material without any special treatment. The burden of treating and disposing of waste oil can be reduced.

Explanatory drawing schematically showing one embodiment of the present invention in a state where an electric furnace is vertically crossed Explanatory drawing schematically showing another embodiment of the present invention in a state where an electric furnace is vertically crossed.

The method for producing molten iron based on the present invention is in an electric furnace provided with a melting chamber 1 for melting a cold iron source by arc heating and a preheating chamber 2 for preheating the cold iron source supplied to the melting chamber 1. The exhaust gas generated in the melting chamber 1 is preheated by passing the exhaust gas generated in the melting chamber 1 through the preheating chamber 2 to which the cold iron source is supplied, and the preheated cold iron source is supplied to the melting chamber 1 to supply the preheated cold iron source to the melting chamber 1. It is a method of obtaining molten iron by melting with. Conventionally, as such a molten iron manufacturing process, there are various types different in the installation form and structure of the preheating chamber, the preheating form of the cold iron source in the preheating chamber, or the method of moving the cold iron source from the preheating chamber to the melting chamber. In such a molten iron production process, waste oil is mixed with a cold iron source, and the cold iron source mixed with the waste oil is preheated in the preheating chamber 2.

The temperature of the exhaust gas that is generated in the melting chamber 1 of the electric furnace and then guided to the preheating chamber 2 is usually about 400 to 1000 ° C., and the waste oil mixed in the cold iron source heats the exhaust gas in the preheating chamber 2. By being heated by, (i) part or all of the waste oil is burned in the preheating chamber 2 to become a preheating source for the cold iron source, and (ii) the waste oil not burned in the preheating chamber 2 is melted. It is considered that the room 1 serves as an auxiliary heat source, and even if the above (i) does not occur, the above (ii) always occurs. Therefore, the waste oil mixed with the cold iron source heats the cold iron source and / or the molten iron. Can be added, so that the power intensity for melting the cold iron source can be reduced.

Here, in the present invention, mixing waste oil with a cold iron source means that the waste oil is added to the cold iron source and the waste oil adheres to the cold iron source. In this case, it is sufficient that the waste oil adheres to the cold iron source when the cold iron source is charged into the preheating chamber 2. Therefore, the timing of adhering the waste oil to the cold iron source may be any of before charging into the preheating chamber 2, at the time of charging into the preheating chamber 2, and after charging into the preheating chamber 2, and they may be appropriately combined. You may. Specific timings for adding waste oil to the cold iron source include, for example, adding it at the cold iron source storage site, adding it with a dedicated mixing (addition) facility, or putting it in a transport container such as a supply bucket. It may be added, added at the time of charging into the preheating chamber 2, added after charging into the preheating chamber 2, or the like, or may be combined as appropriate. However, from a work point of view, it is convenient to add waste oil while the cold iron source is placed in a transport container such as a supply bucket.

The cold iron source to be melted in the present invention usually includes, but is not limited to, own waste generated from a steel mill, scrap generated from the market, and pig iron obtained by solidifying hot metal. Examples of own scrap generated from steelworks include non-stationary parts (parts generated at the start of casting and parts generated at the end of casting) of slabs cast by continuous casting or ingot formation, and rolling of steel materials such as steel strips. In addition, scraps generated from the market include, but are not limited to, construction steel materials (H-shaped steel, etc.), automobile steel materials, and recycled materials such as cans. Pig iron obtained by solidifying hot metal is pig iron obtained by using iron ore, coke, or the like as raw materials in a blast furnace or other blast furnace.

In the present invention, there is no particular limitation on the type and properties of waste oil (non-new oil) mixed with the cold iron source, and the waste oil contains oil that can be a heat source in the electric furnace (preheating chamber 2 and / or melting chamber 1). If it is, it may contain a large amount of components other than oil (moisture, solids, etc.). Even if the waste oil contains a large amount of water, there is no problem because the water evaporates in the preheating chamber 2 (there is no risk of steam explosion), and the solid content (iron and other inorganic components) contained in the waste oil is There is no problem because it is finally melted and becomes a part of molten iron or molten slag.
There are various forms of waste oil, but most of them contain a large amount of components other than oil (moisture, solids, etc.), and the oil deteriorates under the usage environment, so the initial function is In many cases, these waste oils have been treated as industrial waste or landfilled. The present invention can be used without any problem even with such waste oil, and therefore has an advantage that the burden of treating and disposing of the waste oil can be reduced.

For example, in the rolling process of a steel manufacturing process, a large amount of oil-containing lubricant is used to lubricate a material to be rolled (such as a steel strip) and a rolling roll. This lubricant is circulated and reused, but if it deteriorates due to heat generated during rolling or if the generated iron is mixed with oxidized scale, it will not be able to perform its original function. Therefore, the lubricant used for a certain period of time (used lubricant) is recovered and replaced with a new lubricant. Most of this used lubricant is water, and the oil content is about several percent. In the present invention, such a used lubricant having a low oil content may be used as it is and mixed with a cold iron source as waste oil, or a part of water may be separated and removed by using an oil-water separator or the like to separate and remove the oil content. It may be used after increasing the ratio (for example, about several tens of mass%). Increasing the proportion of oil in this way is advantageous in reducing the power intensity. Further, the solid content of the used lubricant may be separated as oil-containing sludge by solid-liquid separation, and this oil-containing sludge may be used as waste oil. Usually, this oil-containing sludge contains solids and oils such as scales in which iron is oxidized and inorganic particles (for example, sand) derived from dust, and further contains water.

Further, for example, the lubricant used in the engine of a large machine has a high calorific value containing almost no water, and the used lubricant can be used as a fuel as a substitute for heavy oil after removing impurities. Sometimes used, it is called recycled heavy oil. In the present invention, such a used lubricant having a high calorific value may be used and mixed with a cold iron source as waste oil. However, in this case, it is desirable to weigh the cost of waste oil with a high calorific value such as recycled heavy oil and the cost of electric power.
In addition to the lubricants listed above, there are waste oils generated from various uses, and these waste oils can be used in the present invention.

The mixing amount (addition amount) of waste oil with respect to the cold iron source may be appropriately determined according to the heat applied to the cold iron source and molten iron depending on the oil content of the waste oil, but usually, 1 ton of cold iron source is used with respect to the cold iron source. It is preferable to mix waste oil having a calorific value of 2 Mcal or more and 50 Mcal or less per unit. If the calorific value of the waste oil mixed with the cold iron source per ton of the cold iron source is less than 2 Mcal, it may not be possible to sufficiently add heat to the cold iron source or molten iron, while if it exceeds 50 Mcal, it becomes waste oil. Since the amount of water contained is also large, the amount of heat is used to evaporate the water, and there is a risk that the heat will not reach the original purpose of heating the cold iron source or molten iron.
Therefore, it is preferable to determine the amount of waste oil added according to the unit calorific value of the waste oil used so as to satisfy such conditions.

For example, when recycled heavy oil is used as waste oil, assuming that the calorific value of the regenerated heavy oil is about 10,000 kcal / kg and the required calorific value per ton of the cold iron source is 10 Mcal, 1 kg per ton of the cold iron source. Recycled heavy oil is required.
Further, when a waste oil obtained by separating and removing a part of water and a solid content from the used lubricating oil in the rolling process of a steel mill (water content is about 55 mass%) is used, the calorific value of this waste oil is about about 55 mass%. Assuming that the calorific value is 4000 kcal / kg and the required calorific value per ton of cold iron source is 10 Mcal, 2.5 kg of waste oil is required per ton of cold iron source.

Further, as described above, in the present invention, waste oil containing a large amount of water or waste oil containing solids such as oil-containing sludge can be used as it is, so that the waste oil can be used as a material without any special treatment. it can. Therefore, it can be said that the method of the present invention is a method capable of treating and disposing of waste oil, which has been treated and disposed of at a high cost (for example, industrial waste treatment and landfill disposal), at low cost. From this point of view, the waste oil used in the present invention is preferably waste oil containing water and / or solid content together with oil, and in particular, a used lubricant in the rolling process of a metal material such as a steel plate. Waste oil such as the above is used as it is, or a part of the water content is separated and removed by applying a relatively simple treatment to the used lubricant (if necessary, the solid content is separated and removed by solid-liquid separation. ) Etc. are preferred. Examples of such waste oil include waste oil containing an oil content of about 5 to 98 mass%, preferably about 15 to 70 mass%, and the balance of which is water and unavoidable impurities (solid content, etc.).

The temperature of the exhaust gas generated in the melting chamber 1 and introduced into the preheating chamber 2 is about 400 to 1000 ° C., but in the present invention, the exhaust gas temperature when the exhaust gas is exhausted from the preheating chamber 2 is set to 400 ° C. or higher. Is preferable. If the temperature of the exhaust gas when exhausted from the preheating chamber 2 is less than 400 ° C., the supply amount of waste oil (oil content) may be insufficient, or the combustion of waste oil (oil content) may be insufficient. Further, the exhaust gas discharged from the electric furnace needs to be reheated by a burner outside the furnace as a measure against dioxins, but if the exhaust gas temperature when exhausted from the preheating chamber 2 is less than 400 ° C., gas heating is required. Burner fuel costs are high.
The exhaust gas temperature when exhausted from the preheating chamber 2 is, for example, the supply speed of the cold iron source into the preheating chamber 2, the amount of waste oil added to the cold iron source, the water content of the waste oil, and the suction of the exhaust gas to the outside of the furnace. It can be managed by adjusting the speed and so on. Therefore, a thermometer is provided at the exhaust port of the preheating chamber 2 to measure the exhaust gas temperature, and based on this exhaust gas temperature, the supply speed of the cold iron source into the preheating chamber 2 and the amount of waste oil added to the cold iron source. , It is preferable to control the exhaust gas temperature by adjusting one or more of the water content of the waste oil, the suction rate of the exhaust gas to the outside of the furnace, and the like.

As mentioned earlier, there are various types of molten iron manufacturing methods (manufacturing processes) in which the cold iron source is preheated by flowing the exhaust gas generated in the melting chamber 1 to the preheating chamber 2. For example. Regarding the preheating form of the cold iron source in the preheating chamber 2, there are the following different types.
(A) The cold iron source is preheated in a state of being filled in the preheating chamber 2 (usually in a state of being filled in the height direction), and the preheated cold iron source is sequentially supplied to the melting chamber 1. This is a method for producing molten iron. For example, a cold iron source charged into the preheating chamber 2 from above is filled in the preheating chamber 2 in the height direction, and the filled cold iron source sequentially descends in the preheating chamber 2. At the same time, it is preheated by the exhaust gas passing through the preheating chamber 2, and after that, it is sequentially charged into the melting chamber 1 from the lower side of the preheating chamber 2.
(A) A molten iron production method in which a cold iron source is preheated while being transferred by a transfer means 17 in the preheating chamber 2, and the preheated cold iron source is sequentially supplied from the transfer means 17 to the melting chamber 1. For example, while the cold iron source is transferred by the transfer means 17 (belt conveyor or the like) in the horizontal preheating chamber 2, it is preheated by the exhaust gas passing through the preheating chamber 2, and then the melting chamber 1 is transferred from the end of the transfer means 17. Will be charged in sequence.

FIG. 1 is an explanatory view schematically showing an embodiment of the present invention in a state in which an electric furnace is vertically crossed. This embodiment relates to the above-mentioned type (a) type of molten iron production method.
The electric furnace includes a melting chamber 1 for melting the cold iron source by arc heating, and a preheating chamber 2 for preheating the cold iron source supplied to the melting chamber 1.
The upper part of the melting chamber 1 is covered with a furnace lid 4 having a water-cooled structure that can be opened and closed. A plurality of electrodes 5 are inserted from above through the furnace lid 4 in the substantially central portion of the melting chamber 1, and an arc heating unit A that melts the cold iron source by blowing an arc between these electrodes 5 is configured. Will be done. Normally, the electrode 5 is made of graphite or the like and can move up and down.

A shaft-shaped preheating chamber 2 is provided in the upper part of the melting chamber 1 at a position away from the arc heating portion A so as to communicate with the melting chamber 1, and a cold iron source that can be opened and closed is provided in the upper part of the preheating chamber 2. The entrance 20 is provided. Further, an exhaust port 21 is provided on the upper side of the preheating chamber 2, and an exhaust duct 6 is connected to the exhaust port 21. The exhaust duct 6 is connected to a suction blower (not shown), and the high-temperature exhaust gas generated in the melting chamber 1 flows into the preheating chamber 2 by suction by the suction blower, passes through the preheating chamber 2, and then passes through the preheating chamber 2, and then the exhaust duct 6. Exhaust from 6. A dust collector (not shown) is provided in the middle of the exhaust duct 6.

A bottom-opening type supply bucket 13 suspended from the traveling carriage 16 can be moved above the preheating chamber 2, and a cold iron source is moved into the preheating chamber 2 from the supply bucket 13 through the cold iron source charging inlet 20. x is charged.
The melting chamber 1 faces a space portion 1a below the preheating chamber 2, and a pusher 3 (pusher) for pushing out the cold iron source x filled in the space portion 1a toward the arc heating portion A by the electrode 5. ) Is provided. The extruder 3 is provided so as to be able to advance and retreat in the arc heating portion A (toward the center of the furnace in this embodiment) through the side wall of the melting chamber 1, and is driven by a driving device (not shown), and a space is provided at the tip thereof. The cold iron source x in the portion 1a is pushed out to the arc heating portion A side.
For example, unlike the electric furnace shown in Patent Document 2, the cold iron source in the space portion 1a due to the weight of the cold iron source x filled in the preheating chamber 2 and the space portion 1a without providing the extruder 3. x may be naturally extruded to the arc heating portion A side.

An oxygen blowing lance 7 and a carbonaceous material blowing lance 8 are inserted into the melting chamber 1 from above through the furnace lid 4.
From the carbon material blowing lance 8, a carbon material made of one or more kinds such as coke, char, coal, charcoal, and graphite is blown into the molten slag s using air, nitrogen, or the like as a transport gas. Further, oxygen is supplied (injected) from the oxygen blowing lance 7, and the molten slag is pushed away by this oxygen, and oxygen is blown into the molten iron m.
An oxygen-containing gas (for example, a mixed gas of pure oxygen and air) may be blown from the oxygen blowing lance 7 instead of pure oxygen.

In the melting chamber 1, a hot water outlet 11 is provided on the bottom of the furnace opposite to the side where the preheating chamber 2 is provided, and a slag outlet 12 is provided on the side wall above the hot water outlet 11. The hot water outlet 11 and the slag outlet 12 are closed by a filling sand or mud agent filled inside, a hot water outlet 14 that presses the mud agent on the outside, and a slag door 15.
A combustion assist burner 9 is provided at a position substantially directly above the hot water outlet 11 so as to penetrate the furnace lid 4 and be inserted into the melting chamber 1 from above. The combustion assisting burner 9 burns fossil fuels such as heavy oil, kerosene, pulverized coal, propane gas, and natural gas from the combustion supporting gas (oxygen, air, or oxygen-enriched air) in the melting chamber 1. For example, when the molten iron m is discharged from the hot water, an undissolved cold iron source may remain, and in such a case, the combustion assisting burner 9 can help the melting of the cold iron source.
The inner wall of the electric furnace 1 is made of a refractory material, and the furnace wall 10 of the melting chamber 1 has a water-cooled structure.

In the operation of the electric furnace of the present embodiment (manufacturing of molten iron), the arc heating portion A is formed by a plurality of electrodes 5 in the melting chamber 1, and the cold iron source x is melted by using this as a main heat source. Further, the charcoal material is blown into the molten slag s from the charcoal material blowing lance 8 and used as an auxiliary heat source. On the other hand, oxygen is blown into the molten iron m from the oxygen blowing lance 7, and the molten iron is decarburized to a predetermined carbon amount by the oxygen. Further, in order to dissolve the undissolved cold iron source x, a combustion assisting burner 9 is used as needed.

The cold iron source x, which is a raw material for molten iron, is charged into the electric furnace using the supply bucket 13. The cold iron source x is temporarily stored in the scrap storage area for each type, and the cold iron source x of a predetermined type and mass ratio is mixed according to the type of molten iron to be manufactured, and put into the supply bucket 13. Be done. The supply bucket 13 containing the cold iron source x is moved directly above the preheating chamber 2 by the traveling carriage 16, and the cold iron source x is preheated from the supply bucket 13 through the open cold iron source charging inlet 20. Charge in room 2. As shown in FIG. 1, the cold iron source x charged from the cold iron source charging inlet 20 is in a state of being filled in the space portion 1a of the preheating chamber 2 and the melting chamber 1 below the preheating chamber 2.

As for the timing of adding (mixing) waste oil to the cold iron source x, the waste oil is added to the cold iron source x before being charged into the supply bucket 13, and the waste oil is added to the cold iron source x put in the supply bucket 13. It may be added, or waste oil may be added when the cold iron source x is charged into the preheating chamber 2, but as mentioned above, from the viewpoint of work, it is put in the supply bucket 13. It is convenient to add waste oil to the cold iron source x.
A solid organic substance (for example, plastic, rubber, biomass, etc.) may be mixed in the cold iron source x charged into the electric furnace (preheating chamber 2).

The high-temperature exhaust gas generated when the cold iron source x is melted in the melting chamber 1 as described above flows into the preheating chamber 2 by suction of the exhaust gas as described above, rises in the preheating chamber 2, and then exhausted. It is exhausted from the mouth 21. In the case of the present embodiment, the temperature of the exhaust gas flowing in the preheating chamber 2 is about 400 to 1000 ° C., and the waste oil mixed in the cold iron source x is heated by the heat of the exhaust gas in the preheating chamber 2. Part or all of the waste oil burns to serve as a preheating source for the cold iron source x, and the waste oil that has not burned in the preheating chamber 2 serves as an auxiliary heat source in the melting chamber 1. As a result, the heat of combustion of waste oil can be added to the cold iron source x and / or the molten iron m, and the electric power intensity for melting the cold iron source x can be reduced.
Further, since the cold iron source x stays in the preheating chamber 2 for a certain period of time, even if the waste oil mixed in the cold iron source x contains a large amount of water, the water content is almost evaporated in the preheating chamber 2 and substantially. It will not be brought into the melting chamber 1. Further, even if the waste oil contains solid content (iron and other inorganic components), the solid content is finally dissolved and becomes a part of molten iron m or molten slag s.

According to the progress of melting of the cold iron source x in the arc heating portion A in the melting chamber 1, the cold iron source x filled in the space portion 1a of the melting chamber 1 is sequentially pushed to the arc heating portion A side by the extruder 3. Extrude to. Along with this, the cold iron source x filled in the preheating chamber 2 gradually drops, and accordingly, the cold iron source x (cold iron source x mixed with waste oil) is introduced into the preheating chamber 2 by the supply bucket 13. Charge and repeat this. When the melting of the cold iron source x progresses and a predetermined amount (1 charge) of molten iron is accumulated in the melting chamber 1, the cold iron source x is filled in the space portion 1a of the preheating chamber 2 and the melting chamber 1. While maintaining the hot water, molten iron m is discharged from the hot water outlet 11, and molten slag s is discharged from the slag outlet 12.
At the start of operation of the electric furnace, in order to uniformly charge the cold iron source into the melting chamber 1, with the furnace lid 4 open, in the space of the melting chamber 2 on the opposite side of the preheating chamber 2. A cold iron source or a charcoal material may be charged, or a hot metal may be charged into the melting chamber 1 at the time of charging the cold iron source. This hot metal can be charged into the melting chamber 1 by a supply ladle (not shown) or a hot metal gutter (not shown) leading to the melting chamber 1.

FIG. 2 is an explanatory view schematically showing another embodiment of the present invention in a state in which an electric furnace is vertically crossed. This embodiment relates to the method for producing molten iron of the type (a) described above.
The electric furnace used in this embodiment has the same structure and function as that of the first embodiment in FIG. 1, but a horizontal (horizontal) preheating chamber 2 is provided on the side of the melting chamber 1. It communicates with the melting chamber 1.
One end of the preheating chamber 2 communicates with the melting chamber 1, and an exhaust port 21 is provided on the other end side, and an exhaust duct 6 is connected to the exhaust port 21. Similar to the embodiment of FIG. 1, the exhaust duct 6 is connected to a suction blower (not shown), and the high-temperature exhaust gas generated in the melting chamber 1 flows into the preheating chamber 2 by suction by the suction blower, and the preheating chamber 2 After passing through, the exhaust duct 6 is exhausted. A dust collector (not shown) is provided in the middle of the exhaust duct 6.

A transfer means 17 (transfer device) such as a belt conveyor is arranged in the preheating chamber 2 along the longitudinal direction thereof, and the cold iron source x supplied into the preheating chamber 2 is transferred by the transfer means 17. , It is preheated by the exhaust gas flowing through the preheating chamber 2.
The transfer means 17 of the present embodiment extends to the outside of the preheating chamber 2, and the cold iron source x is charged on the transfer means 17 outside the preheating chamber 2 and transferred into the preheating chamber 2. is there. The preheating chamber inlet 22 where the cold iron source x enters the preheating chamber 2 is usually gas-sealed by an air curtain, a seal damper, or the like in order to prevent the exhaust gas in the preheating chamber 2 from leaking to the outside. Not shown) is done.
As the transfer means 17, for example, a conveyor device such as a belt conveyor, a walking beam, a walking hearth, or the like can be used.
The preheating chamber 2 is a space surrounded by a furnace wall including the bottom portion, but in FIG. 2 (schematic diagram), the illustration of the bottom portion of the preheating chamber 2 is omitted for convenience.

A bottom-opening type supply bucket 13 suspended from the traveling carriage 16 can be moved above the start end side of the transfer means 17 located outside the preheating chamber 2, and from the supply bucket 13 onto the transfer means 17. Cold iron source x is charged into.
Since other configurations are the same as those of the embodiment of FIG. 1, the same reference numerals are given and detailed description thereof will be omitted.
In the present embodiment, the transfer means 17 is extended to the outside of the preheating chamber 2, and the cold iron source x is charged on the transfer means 17 outside the preheating chamber 2 and transferred into the preheating chamber 2. However, the transfer means 17 is provided only in the preheating chamber 2, and the cold iron source is provided in the preheating chamber 2, and the cold iron source is provided on the transfer means 17 in the preheating chamber 2 from the cold iron source inlet. You may try to charge x. In this case, in order to prevent the exhaust gas in the preheating chamber 2 from leaking from the cold iron source charging inlet, the cold iron source charging inlet is usually gas-sealed by an air curtain, a seal damper, or the like.

In the present embodiment, the high-temperature exhaust gas generated in the melting chamber 1 flows into the preheating chamber 2 by suction of the exhaust gas as described above, passes through the preheating chamber 2, and then is exhausted from the exhaust port 21. The cold iron source x charged onto the transfer means 17 from the supply bucket 13 is transferred by the transfer means 17 and enters the preheating chamber 2, and then flows through the preheating chamber 2 while being transferred in the preheating chamber 2. Preheated with exhaust gas. Then, the cold iron source x preheated in the preheating chamber 2 in this way is directly introduced into the melting chamber 1 (the space portion 1a on the side of the arc heating portion A) from the end of the transfer means 17.
As for the timing of adding (mixing) waste oil to the cold iron source x, the waste oil is added to the cold iron source x before being charged into the supply bucket 13, and the waste oil is added to the cold iron source x put in the supply bucket 13. It may be added, or waste oil may be added when the cold iron source x is charged onto the transfer means 17, but as described above, from the viewpoint of work, it is put in the supply bucket 13. It is convenient to add waste oil to the cold iron source x.
The operation method / conditions and the action / effect (such as the action / effect of the waste oil mixed in the cold iron source x) of the present embodiment other than those described above are the same as those of the embodiment of FIG.

There are two types of electric furnaces, a DC type and an AC type. Since the electric furnace of the present embodiment is an AC type, it has an electrode 5 as described above. On the other hand, when the electric furnace is a direct current type, electrodes are present at the bottom and the top of the furnace, and an arc is blown between the electrodes to melt the cold iron source. The present invention can also be applied to the production of molten iron by such a DC type electric furnace.
Further, according to the present invention, as long as the method is to guide the exhaust gas generated in the melting chamber 1 to the preheating chamber 2 to preheat the cold iron source x, there is no limitation on the type of electric furnace used, and various types of electric furnaces can be used. It can be applied to the method for producing molten iron used.
Further, as the method for producing molten iron of the type (a) described above, for example, it can be applied to a method for producing molten iron using an electric furnace in which the melting chamber does not have an extruder (see Patent Document 2). Further, as the method for producing molten iron of the type (a) described above, for example, an electric furnace in which the preheating chamber 2 is composed of a rotary kiln (inclined cylindrical furnace body) and the preheating chamber 2 itself also serves as a transfer means 17 (transfer mechanism). It can also be applied to a method for producing molten iron using.

In an electric furnace facility provided with a melting chamber 1 and a preheating chamber 2 as shown in FIG. 1, the cold iron source x was melted to produce molten iron. The equipment specifications of this electric furnace equipment are shown below.
Molten iron capacity of melting chamber: 130 tons Electric power: AC 50Hz
Transformer capacity: 75MVA
Number of electrodes: 3

As the cold iron source x, as mentioned above, a mixture of own scraps generated from the steelworks, scraps generated from the market, and pig iron obtained by solidifying hot metal was used.
From the cold iron source charging inlet 20 at the upper part of the preheating chamber 2, about 10 tons of cold iron source x was charged into the preheating chamber 2 each time by the supply bucket 13. Since the molten iron capacity of the melting chamber 1 is 130 tons, the molten iron capacity of the melting chamber 1 is obtained by repeating the charging of the cold iron source x into the preheating chamber 2 by the supply bucket 13 13 times at predetermined intervals. 130 tons of molten iron was produced. A thermocouple was placed at the exhaust port 21 of the preheating chamber 2 and the exhaust gas temperature was measured.
In the example of the invention, waste oil was added to the cold iron source x placed in the supply bucket 13. The following waste oil was used as the waste oil to be added to the cold iron source x.
Waste oil A: Solid content is separated and removed from the used lubricating oil in the rolling process of the steelworks by solid-liquid separation, and part of the water is separated and removed using an oil-water separator (total calorific value 4830 kcal / kg).
Waste oil B: Recycled heavy oil (total calorific value 9770 kcal / kg) from which impurities have been removed from the used lubricating oil of the engine of large machinery.

Table 1 shows the production conditions and electric power intensity of molten iron in the invention examples and comparative examples.
The comparative example is a production example in which waste oil is not mixed (added) with the cold iron source x, but the production conditions are the same as those of the invention example except for the production example.
In Invention Example 1, waste oil B (total calorific value 9770 kcal / kg) was used as the waste oil to be mixed with the cold iron source x, and waste oil having a calorific value of 2 Mcal per ton of the cold iron source was mixed with the cold iron source x. .. The power intensity of the first invention example was 344 kWh / t, which was 2 kWh / t less than that of the comparative example. The exhaust gas temperature at the time of exhaust from the preheating chamber was 428 ° C.

In Invention Example 2, waste oil A (total calorific value of 4830 kcal / kg) was used as the waste oil to be mixed with the cold iron source x, and waste oil having a calorific value of 10 Mcal per ton of the cold iron source was mixed with the cold iron source x. .. The electric power intensity of the second invention example 2 was 337 kWh / t, which was 9 kWh / t less than that of the comparative example. The exhaust gas temperature at the time of exhaust from the preheating chamber was 607 ° C.
Also in Invention Example 3, waste oil A (total calorific value 4830 kcal / kg) was used as the waste oil to be mixed with the cold iron source x, and waste oil having a calorific value of 50 Mcal per ton of the cold iron source was mixed with the cold iron source x. .. The electric power intensity of the third invention example was 339 kWh / t, which was 7 kWh / t less than that of the comparative example. The exhaust gas temperature at the time of exhaust from the preheating chamber was 545 ° C.

1 Melting chamber 1a Space part 2 Preheating chamber 3 Extruder 4 Furnace lid 5 Electrode 6 Exhaust duct 7 Oxygen blowing lance 8 Charcoal blowing lance 9 Auxiliary burner 10 Furnace wall 11 Hot water outlet 12 Outlet outlet 13 Supply bucket 14 Hot water outlet 15 Exit door 16 Traveling trolley 17 Transportation means 20 Cold iron source equipment entrance 21 Exhaust port 22 Preheating room entrance
x cold iron source
m molten iron
s Molten slag A arc heating part

Claims (14)

In an electric furnace provided with a melting chamber (1) for melting the cold iron source by arc heating and a preheating chamber (2) for preheating the cold iron source supplied to the melting chamber (1), the melting chamber (1) The cold iron source is preheated by passing the exhaust gas generated in the above through the preheating chamber (2) to which the cold iron source is supplied, and the preheated cold iron source is supplied to the melting chamber (1) to be supplied to the melting chamber (1). It is a method of obtaining molten iron by melting in 1).
A method for producing molten iron by an electric furnace, which comprises mixing waste oil with a cold iron source and preheating the cold iron source mixed with the waste oil in a preheating chamber (2). The first aspect of the present invention, wherein the cold iron source is preheated while being filled in the preheating chamber (2), and the preheated cold iron source is sequentially supplied to the melting chamber (1). A method for producing molten iron using an electric furnace. A preheating chamber (2) is provided in the upper part of the melting chamber (1) at a position away from the arc heating part so as to communicate with the melting chamber (1), and a cold iron source charging inlet is provided in the upper part of the preheating chamber (2). In producing molten iron in an electric furnace having (20),
The cold iron source charged into the preheating chamber (2) from the cold iron source charging inlet (20) is filled in the space portion (1a) of the preheating chamber (2) and the melting chamber (1) below it. The method for producing molten iron by an electric furnace according to claim 2, wherein the cold iron source of the space portion (1a) is sequentially extruded to the arc heating portion side. The method for producing molten iron by an electric furnace according to claim 3, wherein the cold iron source of the space portion (1a) is sequentially extruded to the arc heating portion side by the extruder (3). The cold iron source is preheated while being transferred by the transfer means (17) in the preheating chamber (2), and the preheated cold iron source is sequentially supplied from the transfer means (17) to the melting chamber (1). The method for producing molten iron by an electric furnace according to claim 1. The method for producing molten iron by an electric furnace according to any one of claims 1 to 5, wherein waste oil having a calorific value of 2 Mcal or more and 50 Mcal or less per ton of the cold iron source is mixed with the cold iron source. The method for producing molten iron by an electric furnace according to any one of claims 1 to 6, wherein the waste oil to be mixed with the cold iron source is waste oil containing water and / or solid content together with oil. The method for producing molten iron by an electric furnace according to claim 7, wherein the waste oil containing a solid content is oil-containing sludge. Any of claims 1 to 6, wherein the waste oil to be mixed with the cold iron source is a used lubricant in the rolling process of a metal material or a part of water is separated and removed from the used lubricant. The method for producing molten iron by the electric furnace described in 1. The method for producing molten iron by an electric furnace according to any one of claims 1 to 9, wherein the temperature of the exhaust gas when exhausted from the preheating chamber (2) is 400 ° C. or higher. In an electric furnace provided with a melting chamber (1) for melting the cold iron source by arc heating and a preheating chamber (2) for preheating the cold iron source supplied to the melting chamber (1), the melting chamber (1) The cold iron source is preheated by passing the exhaust gas generated in the above through the preheating chamber (2) to which the cold iron source is supplied, and the preheated cold iron source is supplied to the melting chamber (1) to be supplied to the melting chamber (1). When melting in 1) to obtain molten iron
A method for treating waste oil, which comprises mixing waste oil with a cold iron source and preheating the cold iron source mixed with the waste oil in a preheating chamber (2). The method for treating waste oil according to claim 11, wherein the waste oil mixed with the cold iron source is waste oil containing water and / or solid content together with oil. The method for treating waste oil according to claim 12, wherein the waste oil containing solid content is oil-containing sludge. The waste oil according to claim 11, wherein the waste oil mixed with the cold iron source is a used lubricant in the rolling process of a metal material or a waste oil obtained by separating and removing a part of water from the used lubricant. Processing method.

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