JP7107336B2 - Manufacturing method of molten iron by electric furnace - Google Patents

Description

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

In electric furnaces, molten iron is produced by melting cold iron sources 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 electric furnaces, there are methods of preheating the cold iron source before melting with a burner using fossil fuel, etc., preheating the 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 Literature 1 discloses a technique of heating (preheating) a cold iron source with a burner called an auxiliary 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 a cold iron source with high-temperature exhaust gas generated during melting, a preheating chamber for the cold iron source is connected to the upper part of the melting chamber, and high-temperature exhaust gas generated in the melting chamber is heated. , preheating the cold iron source by passing it through a preheating chamber filled with the cold iron source and supplying the preheated cold iron source to the melting chamber. Further, in the method of Patent Document 2, coke is also blown into the melting chamber and used as an auxiliary heat source.

JP-A-63-93816 JP-A-10-292990

The method of Patent Document 1 is effective for heating a cold iron source existing in a cold spot or the like in a melting chamber, but it cannot be said to be sufficient as a method for preheating the entire cold iron source, and power consumption in an electric furnace is reduced. No significant effect on suppression can be expected. In addition, since installation of an auxiliary burner requires equipment costs for installing fuel and oxygen piping for the burner, the facility configuration should be such that the auxiliary burner can sufficiently preheat the cold iron source. requires a large equipment cost.
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 enough to significantly reduce the power consumption rate. It is enough. In addition, the same applies to the method in which coke is blown in combination, which is described in the same document.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and to provide a method for producing molten iron by melting a cold iron source in an electric furnace, without using special equipment and at a lower cost than the conventional method. To provide a method capable of producing molten iron with a specific electric power consumption.

As a result of repeated studies on a method capable of solving the above problems, the inventors of the present invention have found that in a method of preheating a cold iron source in a preheating chamber using furnace exhaust gas (high-temperature exhaust gas generated in a melting chamber of an electric furnace), By mixing the cold iron source with waste oil 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 the molten iron using the calorific value of the waste oil. It was found that the power consumption rate can be effectively reduced by
The present invention was made based on such findings, and has the following gist.

[1] 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 exhaust gas generated in (1) is passed through a preheating chamber (2) supplied with a cold iron source to preheat the cold iron source, and the preheated cold iron source is supplied to the melting chamber (1), A method of obtaining molten iron by melting in a melting chamber (1), comprising:
A method for producing molten iron by an electric furnace, characterized by mixing a cold iron source with waste oil and preheating the cold iron source mixed with the waste oil in a preheating chamber (2).
[2] In the manufacturing method of [1] above, 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 by an electric furnace, characterized by:

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

[5] In the manufacturing method of [1] above, 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. (1) A method for producing molten iron by an electric furnace, characterized in that the molten iron is sequentially supplied.
[6] In the production method of any one of [1] to [5] above, the cold iron source is mixed with waste oil having a calorific value of 2 Mcal or more and 50 Mcal or less per 1 ton of the cold iron source. A method of producing molten iron in a furnace.
[7] In the manufacturing method of any one of [1] to [6] above, the waste oil mixed with the cold iron source is waste oil containing oil and/or water and/or solids. manufacturing method.

[8] The method for producing molten iron using an electric furnace in the above [7], wherein the waste oil containing solids is oil-containing sludge.
[9] In the manufacturing method of any one of [1] to [6] above, the waste oil mixed with the cold iron source is used lubricant in the rolling process of metal materials or partially removes water from the used lubricant. A method for producing molten iron using an electric furnace, wherein the molten iron is separated and removed.
[10] Production of molten iron using an electric furnace, wherein the temperature of the exhaust gas discharged from the preheating chamber (2) is 400°C or higher in the production method of any one of [1] to [9] above. Method.

[11] 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 exhaust gas generated in (1) is passed through a preheating chamber (2) supplied with a cold iron source to preheat the cold iron source, and the preheated cold iron source is supplied to the melting chamber (1), When obtaining molten iron by melting in the melting chamber (1),
A method for treating waste oil, characterized by mixing a cold iron source with waste oil and preheating the cold iron source mixed with the waste oil in a preheating chamber (2).

[12] The method of treating waste oil according to [11] above, wherein the waste oil to be mixed with the cold iron source is waste oil containing oil and/or water and/or solids.
[13] The method for treating waste oil according to the above [12], wherein the waste oil containing solids is oil-containing sludge.
[14] In the treatment method of [11] above, the waste oil mixed with the cold iron source is used lubricant in the rolling process of metal materials, or part of the water is separated and removed from the used lubricant. A method for treating waste oil, 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, the cold iron source is mixed with waste oil, and the cold iron mixed with the waste oil is By preheating the source in the preheating chamber, the calorific value of the waste oil can be used to add heat to the source of cold iron and molten iron. Molten iron can be manufactured at a low cost per unit.
In addition, according to this method, waste oil containing solids such as waste oil containing a large amount of water and oil-containing sludge can be used as it is, so that waste oil can be recycled without 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 in which the electric furnace is longitudinally cross-sectioned. Explanatory drawing schematically showing another embodiment of the present invention in a state in which the electric furnace is longitudinally cross-sectioned.

The manufacturing method of molten iron on which the present invention is based is performed 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 cold iron source is preheated by passing the exhaust gas generated in the melting chamber 1 through a preheating chamber 2 supplied with the cold iron source, and the preheated cold iron source is supplied to the melting chamber 1. It is a method of obtaining molten iron by melting at Conventionally, there are various types of molten iron production processes, such as the installation form and structure of the preheating chamber, the preheating form of the cold iron source in the preheating chamber, and the method of moving the cold iron source from the preheating chamber to the melting chamber. However, according to the method of the present invention, in such a molten iron manufacturing process, waste oil is mixed with a cold iron source, and the cold iron source mixed with this waste oil is preheated in the preheating chamber 2 .

After being generated in the melting chamber 1 of the electric furnace, the temperature of the exhaust gas that is led to the preheating chamber 2 is usually about 400 to 1000° C. The waste oil mixed with the cold iron source heats the exhaust gas in the preheating chamber 2. (i) part or all of the waste oil burns in the preheating chamber 2 to serve as a preheating source for the cold iron source; It is considered that the chamber 1 serves as an auxiliary heat source, and even if the above (i) does not occur, the above (ii) will always occur, so the waste oil mixed with the cold iron source will heat the cold iron source and / or the molten iron. can be added, so that the power consumption rate for melting the cold iron source can be reduced.

Here, mixing the cold iron source with the waste oil in the present invention means that the cold iron source is added with the waste oil so that the cold iron source adheres to the waste oil. 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 attaching the waste oil to the cold iron source may be before charging into the preheating chamber 2, at the time of charging into the preheating chamber 2, or after charging into the preheating chamber 2, or any suitable combination thereof. may Specific timings for adding waste oil to the cold iron source include, for example, adding at the place where the cold iron source is stored, adding at a dedicated mixing (addition) facility, and adding it in a transportation container such as a supply bucket. It may be added, added at the time of charging into the preheating chamber 2, or added after charging into the preheating chamber 2, or may be combined as appropriate. However, from the viewpoint of work, it is convenient to add the waste oil while the cold iron source is placed in a transport container such as a supply bucket.

Cold iron sources to be melted in the present invention include, but are not limited to, in-house scrap generated from ironworks, scrap generated from the market, and pig iron obtained by solidifying hot metal. Examples of in-house scrap generated from steelworks include unsteady parts of slabs cast by continuous casting or ingot casting (parts generated at the start of casting and parts generated at the end of casting), rolling of steel materials such as steel strips, etc. In addition, scrap generated in the market includes, but is not limited to, recycled materials such as construction steel (H-beam, etc.), automobile steel, and cans. Pig iron obtained by solidifying molten pig iron is obtained by tapping and solidifying molten pig iron obtained from raw materials such as iron ore and coke in a blast furnace such as a blast furnace.

In the present invention, there are no particular restrictions on the type or properties of the waste oil (oil that is not new) mixed with the cold iron source, and it contains oil that can serve as a heat source in the electric furnace (preheating chamber 2 and/or melting chamber 1). If so, it may contain a large amount of components other than oil (moisture, solid content, 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). There is no problem because it will eventually be melted and become part of the molten iron or molten slag.
There are various forms of waste oil, but most of them contain a large amount of non-oil components (water, solid content, etc.), or the oil content deteriorates in the usage environment and loses its original function. In many cases, these waste oils have been disposed of as industrial waste or landfilled. The present invention can use such waste oil without any problem, and therefore has the advantage of reducing the burden of treatment and disposal of waste oil.

For example, in the rolling process of the steel manufacturing process, a large amount of oil-containing lubricant is used to lubricate the material to be rolled (steel strip, etc.) and the rolling rolls. This lubricant is circulated and reused, but if it deteriorates due to the heat generated during rolling, or if it gets mixed with scale that is oxidized iron content, it will not be able to perform its original function. Therefore, lubricant that has been used for a certain period of time (spent lubricant) is collected and replaced with 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 with little oil content may be used as it is and mixed with the cold iron source as waste oil, or a part of the water content may be separated and removed using an oil-water separation agent or the like, and the oil content may be removed. You may use it after raising a ratio (for example, about several tens mass%). Increasing the oil content in this manner is advantageous in terms of reducing the power consumption rate. Alternatively, 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. Normally, this oil-containing sludge contains solids such as iron-oxidized scales and inorganic particles derived from garbage (for example, sand) and oil, and further contains water.

In addition, for example, lubricants used in engines of large machinery contain little water and have a high calorific value. It is sometimes used and is called recycled heavy oil. In the present invention, such a used lubricant having a high calorific value may be used and mixed with the cold iron source as waste oil. However, in this case, it is desirable to balance the cost of waste oil with a high calorific value such as recycled heavy oil against the cost of electric power.
In addition to the lubricants mentioned above, there are waste oils generated from various uses, and these waste oils can be used in the present invention.

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

For example, when recycled heavy oil is used as waste oil, the calorific value of this recycled heavy oil is about 10000 kcal/kg, and the required calorific value per ton of cold iron source is 10 Mcal. Recycled heavy oil is required.
In addition, when using as waste oil (water content is about 55 mass%) obtained by separating and removing part of the water and solid content from used lubricating oil in the rolling process of steel mills, the calorific value of this waste oil is about Assuming that it 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.

In addition, as described above, in the present invention, waste oil containing a solid content such as waste oil containing a large amount of water or oil-containing sludge can be used as it is, so that the waste oil can be recycled without special treatment. can. For this reason, the method of the present invention can be said to be a method that can treat and dispose of waste oil at low cost, which has conventionally been treated and disposed of at high cost (for example, industrial waste treatment and landfill disposal). And from such a point of view, the waste oil used in the present invention is preferably a waste oil containing water and / or solids along with oil, especially used lubricants in the rolling process of metal materials such as steel plates. Waste oil such as is used as it is, or a part of the moisture is separated and removed by adding a relatively simple treatment to the used lubricant (If necessary, the solid content is separated and removed by solid-liquid separation ) and the like are preferably used. Examples of such waste oil include waste oil containing about 5 to 98 mass %, preferably about 15 to 70 mass % of oil, with the balance being water and unavoidable impurities (such as solids).

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. is preferred. If the temperature of the exhaust gas when discharged from the preheating chamber 2 is less than 400° C., there is a possibility that the amount of waste oil (oil content) supplied is insufficient or the combustion of waste oil (oil content) is insufficient. In addition, the exhaust gas discharged from the electric furnace needs to be reheated by a burner outside the furnace for dioxin countermeasures. Higher burner fuel costs.
The exhaust gas temperature when exhausted from the preheating chamber 2 depends on, 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 or the like. For this reason, a thermometer is provided at the exhaust port of the preheating chamber 2 to measure the temperature of the exhaust gas. , the water content of the waste oil, the speed of sucking the exhaust gas out of the furnace, and the like, to control the temperature of the exhaust gas.

As described above, 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 into the preheating chamber 2. For example, Regarding the preheating form of the cold iron source in the preheating chamber 2, there are different types as follows.
(a) The cold iron source is preheated in a state filled in the preheating chamber 2 (usually filled in the height direction), and the preheated cold iron source is sequentially supplied to the melting chamber 1. It is a method of manufacturing molten iron. For example, a cold iron source introduced into the preheating chamber 2 from above is filled in the preheating chamber 2 in the height direction, and the filled cold iron source descends in the preheating chamber 2 sequentially. While being preheated by the exhaust gas passing through the preheating chamber 2 , they are then sequentially charged into the melting chamber 1 from the lower side of the preheating chamber 2 .
(a) A molten iron production method in which 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, For example, the cold iron source is preheated by the exhaust gas passing through the preheating chamber 2 while being transferred by the transfer means 17 (such as a belt conveyor) in the horizontal preheating chamber 2 , and then is transferred from the end of the transfer means 17 to the melting chamber 1 . are sequentially inserted into the

FIG. 1 is an explanatory view schematically showing one embodiment of the present invention in a longitudinally sectioned state of an electric furnace. This embodiment relates to the method for manufacturing molten iron of type (a) above.
The electric furnace comprises 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 upper part of the melting chamber 1 is covered with a water-cooled furnace lid 4 that can be opened and closed. Approximately at the center of the melting chamber 1, a plurality of electrodes 5 are inserted from above through the furnace lid 4, and an arc heating section A is formed in which the cold iron source is melted by firing an arc between these electrodes 5. be done. The electrode 5 is usually made of graphite or the like and is vertically movable.

A shaft-shaped preheating chamber 2 is provided in the upper part of the melting chamber 1 away from the arc heating part A so as to communicate with the melting chamber 1, and an openable and closable cold iron source is provided in the upper part of the preheating chamber 2. A loading port 20 is provided. An exhaust port 21 is provided in the upper portion of the preheating chamber 2 , and the exhaust duct 6 is connected to the exhaust port 21 . This 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 this suction blower. 6 is exhausted. A dust collector (not shown) is provided in the middle of the exhaust duct 6 .

Above the preheating chamber 2, a bottom-opening supply bucket 13 suspended from a traveling carriage 16 can be moved. x is loaded.
In the melting chamber 1, an extruder 3 (pusher ) is provided. The extruder 3 penetrates the side wall of the melting chamber 1 and is provided so as to be able to advance and retreat in the direction of the arc heating section A (in this embodiment, toward the center of the furnace). The cold iron source x in the portion 1a is pushed out to the arc heating portion A side.
For example, like the electric furnace shown in Patent Document 2, without providing the extruder 3, the cold iron source in the space portion 1a is driven by the weight of the cold iron source x filled in the preheating chamber 2 and the space portion 1a. The x may be naturally pushed out to the arc heating portion A side.

An oxygen blowing lance 7 and a carbon 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, carbon material made of one or more kinds of coke, char, coal, charcoal, graphite, etc. is blown into the molten slag s using air, nitrogen, or the like as a carrier gas. Further, oxygen is supplied (injected) from the oxygen blowing lance 7, and the molten slag is pushed away by the oxygen, and the oxygen is blown into the molten iron m.
From the oxygen blowing lance 7, instead of pure oxygen, an oxygen-containing gas (for example, a mixed gas of pure oxygen and air) may be blown.

In the melting chamber 1, a melt outlet 11 is provided at the bottom of the furnace opposite to the side where the preheating chamber 2 is provided, and a slag outlet 12 is provided at the upper side wall. The hot water outlet 11 and the slag outlet 12 are closed by a filling sand or mud agent filled inside, and a hot water outlet door 14 and a slag outlet door 15 which hold them from the outside.
A support burner 9 is provided at a position almost directly above the tapping port 11 and inserted into the melting chamber 1 through the furnace lid 4 from above. The auxiliary burner 9 burns a fossil fuel such as heavy oil, kerosene, pulverized coal, propane gas, or natural gas in the melting chamber 1 with a combustion-supporting gas (oxygen, air, or oxygen-enriched air). For example, when the molten iron m is tapped, an unmelted cold iron source may remain. In such a case, the auxiliary burner 9 can help melt 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 (manufacture of molten iron) of the present embodiment, the arc heating section A is configured by a plurality of electrodes 5 in the melting chamber 1, and the cold iron source x is melted using this as the main heat source. Also, carbon material is blown into the molten slag s from a carbon 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 oxygen decarburizes the molten iron to a predetermined carbon content. Further, in order to melt the unmelted cold iron source x, an auxiliary burner 9 is used as needed.

A cold iron source x, which is a raw material of molten iron, is charged into the electric furnace using a supply bucket 13 . The cold iron source x is temporarily placed in a scrap storage place according to type, and from among them, a predetermined type and mass ratio of the cold iron source x are mixed according to the steel grade of the 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 by the traveling carriage 16 directly above the preheating chamber 2, and the cold iron source x is preheated from the supply bucket 13 through the opened cold iron source loading port 20. Charge into chamber 2. The cold iron source x charged from the cold iron source inlet 20 fills the space 1a of the preheating chamber 2 and the melting chamber 1 below it, as shown in FIG.

The timing of adding (mixing) the waste oil to the cold iron source x is as follows. Either adding waste oil or adding waste oil when charging the cold iron source x into the preheating chamber 2 may be used. It is convenient to add waste oil to the obtained cold iron source x.
The cold iron source x charged into the electric furnace (preheating chamber 2) may contain solid organic substances (for example, plastic, rubber, biomass, etc.).

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 due to the suction of the exhaust gas as described above, rises in the preheating chamber 2, and then is exhausted. It is exhausted from the port 21 . In the case of this embodiment, the temperature of the exhaust gas flowing into the preheating chamber 2 is about 400 to 1000° C., and the waste oil mixed with the cold iron source x is heated in the preheating chamber 2 by the heat of the exhaust gas. A part or all of the waste oil is burned to serve as a preheating source for the cold iron source x, and the waste oil not burned in the preheating chamber 2 serves as an auxiliary heat source in the melting chamber 1. As a result, the combustion heat of the waste oil can be added to the cold iron source x and/or the molten iron m, and the power unit consumption for melting the cold iron source x can be reduced.
In addition, since the cold iron source x stays in the preheating chamber 2 for a certain period of time, even if the waste oil mixed with the cold iron source x contains a large amount of water, most of the water evaporates in the preheating chamber 2. It is not brought into the melting chamber 1. Moreover, even if the waste oil contains solids (iron and other inorganic components), the solids are finally dissolved and become part of molten iron m or molten slag s.

In accordance with the progress of melting of the cold iron source x in the arc heating section 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 section A side by the extruder 3. push out to Along with this, the cold iron source x filled in the preheating chamber 2 descends in sequence, and accordingly, the cold iron source x (cold iron source x mixed with waste oil) is supplied to the preheating chamber 2 by the supply bucket 13 . Insert and repeat. When the melting of the cold iron source x progresses and a predetermined amount (for one charge) of molten iron accumulates in the melting chamber 1, the cold iron source x fills the preheating chamber 2 and the space 1a of the melting chamber 1. While maintaining, the molten iron m is discharged from the tapping port 11, and the molten slag s is tapped from the tapping port 12. - 特許庁
At the start of the 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, A cold iron source or a carbonaceous material may be charged, and 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 through a feeding ladle (not shown) or a hot metal trough (not shown) leading to the melting chamber 1 .

FIG. 2 is an explanatory view schematically showing another embodiment of the present invention in a longitudinally sectioned state of an electric furnace. This embodiment relates to the molten iron production method of type (a) described above.
In the electric furnace used in this embodiment, the structure and functions of the melting chamber 1 are the same as in the embodiment of FIG. It communicates with the melting chamber 1 .
One end of the preheating chamber 2 communicates with the melting chamber 1 , and the other end thereof is provided with an exhaust port 21 to which the exhaust duct 6 is connected. As in 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 due to suction by the suction blower. After passing through, it is exhausted from the exhaust duct 6. 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 its longitudinal direction, and the cold iron source x supplied into the preheating chamber 2 is transferred by the transfer means 17. , is preheated by the exhaust gas flowing through the preheating chamber 2 .
The transfer means 17 of this embodiment extends to the outside of the preheating chamber 2, and the cold iron source x is loaded onto the transfer means 17 outside the preheating chamber 2 and transferred into the preheating chamber 2. be. At the preheating chamber inlet 22 through which the cold iron source x enters the preheating chamber 2, a gas seal (see Fig. not shown) is performed.
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.
Although the preheating chamber 2 is a space surrounded by furnace walls including the bottom, the bottom of the preheating chamber 2 is omitted in FIG. 2 (schematic diagram) for the sake of convenience.

Above the starting end of the transfer means 17 located outside the preheating chamber 2, a bottom-opening type supply bucket 13 suspended from a traveling carriage 16 can be moved. is charged with cold iron source x.
Since other configurations are the same as those of the embodiment of FIG. 1, the same reference numerals are given and detailed description thereof is omitted.
In this embodiment, the transfer means 17 extends outside the preheating chamber 2 so that the cold iron source x is loaded onto 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 a cold iron source charging port is provided in the preheating chamber 2, and the cold iron source is transferred from the cold iron source charging port onto the transfer means 17 in the preheating chamber 2. x may be inserted. In this case, in order to prevent the exhaust gas in the preheating chamber 2 from leaking from the cold iron source charging port, the cold iron source charging port is normally gas-sealed by an air curtain, a seal damper, or the like.

In this embodiment, 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 is exhausted from the exhaust port 21 . The cold iron source x charged from the supply bucket 13 onto the transfer means 17 is transferred by the transfer means 17 and enters the preheating chamber 2, and then flows through the preheating chamber 2 while being transferred inside the preheating chamber 2. Preheated with exhaust gas. Then, the cold iron source x preheated in the preheating chamber 2 in this way is put into the melting chamber 1 (the space portion 1a on the side of the arc heating section A) from the end of the transfer means 17 as it is.
The timing of adding (mixing) the waste oil to the cold iron source x is as follows. It may be added, or the waste oil may be added when charging the cold iron source x onto the transfer means 17. It is convenient to add waste oil to the obtained cold iron source x.
The operating method/conditions and effects of this embodiment other than those described above (such as the effects of waste oil mixed with the cold iron source x) are the same as those of the embodiment shown in FIG.

There are two types of electric furnaces: a DC type and an AC type. Since the electric furnace of this embodiment is an AC type, it has the electrodes 5 as described above. On the other hand, when the electric furnace is of the DC type, there are electrodes at the bottom and 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 using such a DC electric furnace.
In addition, the present invention does not limit the type of electric furnace to be used as long as it is a method of preheating the cold iron source x by guiding the exhaust gas generated in the melting chamber 1 to the preheating chamber 2, and various types of electric furnaces can be used. It can be applied to the manufacturing method of molten iron used.
In addition, as the method for manufacturing molten iron of type (a) described above, for example, it can also be applied to a method for manufacturing molten iron using an electric furnace in which the melting chamber does not have an extruder (see Patent Document 2). In addition, as the method for manufacturing molten iron of the type (a) described above, for example, the preheating chamber 2 is configured by a rotary kiln (an inclined cylindrical furnace body), and the preheating chamber 2 itself serves as a transfer means 17 (transfer mechanism). It can also be applied to a method for producing molten iron using

Molten iron was produced by melting a cold iron source x in an electric furnace facility equipped with a melting chamber 1 and a preheating chamber 2 as shown in FIG. The equipment specifications of this electric furnace equipment are shown below.
Molten iron capacity of melting chamber: 130 tons Power: AC 50Hz
Transformer capacity: 75MVA
Number of electrodes: 3

As the cold iron source x, as mentioned above, a suitable mixture of in-house waste generated from ironworks, scrap generated from the city, and pig iron solidified from hot metal was used.
About 10 tons of cold iron source x was charged into the preheating chamber 2 from the cold iron source inlet 20 at the top of the preheating chamber 2 by the supply bucket 13 at one time. Since the molten iron capacity of the melting chamber 1 is 130 tons, the molten iron capacity of the melting chamber 1 is Produced 130 tons of molten iron. A thermocouple was placed at the exhaust port 21 of the preheating chamber 2 to measure the exhaust gas temperature.
In the invention example, waste oil was added to the cold iron source x placed in the supply bucket 13 . As the waste oil added to the cold iron source x, the following was used.
Waste oil A: Solid content is separated and removed from used lubricating oil in the rolling process of steel mills by solid-liquid separation, and a part of water is separated and removed using an oil-water separating agent (total calorific value: 4830 kcal/kg).
Waste oil B: Recycled heavy oil (total calorific value 9770 kcal/kg) obtained by removing impurities from used lubricating oil of engines of large machinery

Table 1 shows the manufacturing conditions of molten iron and the electric power consumption in the invention examples and comparative examples.
A comparative example is a production example in which waste oil was not mixed (added) to the cold iron source x, but otherwise the production conditions were the same as those of the invention 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 the cold iron source x was mixed with waste oil having a calorific value of 2 Mcal per 1 ton of the cold iron source. . The electric power unit consumption of Invention Example 1 was 344 kWh/t, which was 2 kWh/t lower than that of the comparative example. Further, the exhaust gas temperature when exhausted from the preheating chamber was 428°C.

In Invention Example 2, 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 the cold iron source x was mixed with waste oil having a calorific value of 10 Mcal per 1 ton of the cold iron source. . The electric power unit consumption of Invention Example 2 was 337 kWh/t, which was 9 kWh/t lower than that of the comparative example. Further, the exhaust gas temperature at the time of exhaust from the preheating chamber was 607°C.
In Invention Example 3, waste oil A (total calorific value 4830 kcal/kg) was used as the waste oil to be mixed with cold iron source x, and waste oil with a calorific value of 50 Mcal per ton of cold iron source was mixed with cold iron source x. . The electric power unit consumption of Invention Example 3 was 339 kWh/t, which was 7 kWh/t lower than that of the comparative example. Further, the exhaust gas temperature when exhausted from the preheating chamber was 545°C.

1 Melting Chamber 1a Spatial Part 2 Preheating Chamber 3 Extruder 4 Furnace Lid 5 Electrode 6 Exhaust Duct 7 Oxygen Injection Lance 8 Carbon Material Injection Lance 9 Support Burner 10 Furnace Wall 11 Tapping Port 12 Tapping Port 13 Supply Bucket 14 Tapping Door 15 Door for slag discharge 16 Traveling carriage 17 Transfer means 20 Cold iron source charging port 21 Exhaust port 22 Preheating chamber entrance
x cold iron source
m molten iron
s Molten slag A Arc heating part

Claims (14)

A melting chamber (1) in an electric furnace comprising 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 is passed through the preheating chamber (2) supplied with the cold iron source to preheat the cold iron source, the preheated cold iron source is supplied to the melting chamber (1), and the melting chamber ( A method of obtaining molten iron by melting in 1),
A method for producing molten iron by an electric furnace, characterized in that waste oil is added to a cold iron source to adhere it, and the cold iron source with the waste oil attached is preheated in a preheating chamber (2). 2. A cold iron source according to claim 1, characterized in that 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 of producing molten iron using an electric furnace. A preheating chamber (2) is provided in the upper part of the melting chamber (1) away from the arc heating part so as to communicate with the melting chamber (1), and a cold iron source charging port is provided in the upper part of the preheating chamber (2). When 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 port (20) is filled in the preheating chamber (2) and the space portion (1a) of the melting chamber (1) below it. 3. The method for producing molten iron by an electric furnace according to claim 2, wherein the cold iron source in the space portion (1a) is pushed out sequentially toward the arc heating section. 4. The method for producing molten iron by an electric furnace according to claim 3, wherein the cold iron source in the space portion (1a) is sequentially extruded toward the arc heating section by an 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 the electric furnace according to claim 1, characterized in that: The method for producing molten iron by an electric furnace according to any one of claims 1 to 5, wherein the cold iron source is mixed with waste oil having a calorific value of 2 Mcal or more and 50 Mcal or less per 1 ton of the cold iron source. 7. The method for producing molten iron by an electric furnace according to any one of claims 1 to 6, wherein the waste oil added to and attached to the cold iron source is waste oil containing water and/or solids along with oil. 8. The method for producing molten iron by an electric furnace according to claim 7, wherein the waste oil containing solids is oil-containing sludge. Claims 1 to 6, characterized in that the waste oil added to and adhered to the cold iron source is a used lubricant in the rolling process of metal materials or a product obtained by separating and removing part of the water from the used lubricant. The method for producing molten iron by the electric furnace according to any one of 1. The method for producing molten iron by an electric furnace according to any one of claims 1 to 9, characterized in that the temperature of the exhaust gas when discharged from the preheating chamber (2) is 400°C or higher. A melting chamber (1) in an electric furnace comprising 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 is passed through the preheating chamber (2) supplied with the cold iron source to preheat the cold iron source, the preheated cold iron source is supplied to the melting chamber (1), and the melting chamber ( When melting in 1) to obtain molten iron,
A method for treating waste oil, characterized by adding waste oil to a cold iron source so that it adheres thereto, and preheating the cold iron source with the waste oil adhered thereon in a preheating chamber (2). 12. The method for treating waste oil according to claim 11, wherein the waste oil to be added to and adhered to the cold iron source is waste oil containing oil and/or water and/or solids. 13. The method for treating waste oil according to claim 12, wherein the waste oil containing solids is oil-containing sludge. 12. The waste oil that is added to and attached to the cold iron source is a used lubricant in the rolling process of metal materials or a product obtained by separating and removing part of the water from the used lubricant. waste oil disposal method.

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