JPH08302412A - Steel scrap melting furnace and its melting method - Google Patents

Abstract

PURPOSE: To provide a steel scrap melting furnace capable of charging the raw materials such as the scrap and the iron ore into a furnace through a tube by connecting and piercing a raw material charging tube which is pierced from the outside of the furnace to the inside of the furnace, and provided with small gradient at the tip part in the range corresponding to the nose, the shoulder, and the belly. CONSTITUTION: In a top-blown or a top and bottom-blown steel scrap melting furnace 1, a scrap charging tube 5 which is inclined diagonally upward is arranged on a belly, a nose, or a shoulder while it is extended into the melting furnace 1. The scrap 7 can be pre-heated or melted preliminarily in the molten slag 3, the scattering of the slag splash and the cooling of the slag is eliminated when the raw materials are charged, and the efficient scrap melting can be realized to improve the productivity without providing the disturbance of the slag surface through the slag layer of high temperature to fluctuate the secondary combustion ratio or the heat gaining efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel scrap melting furnace and a melting method which are excellent in secondary combustion rate and heat deposition efficiency.

[0002]

2. Description of the Related Art In recent years, it has become a technical subject to efficiently produce molten metal by recycling solid metal raw materials such as scrap due to resource and environmental problems. There are various kinds of metal scraps, but as a method for obtaining molten iron by using steel scrap, which has a large amount of generation, conventionally, most has been carried out in an electric furnace. However, the electric furnace consumes a large amount of electric power for melting and refining scrap, and therefore, the melting cost increases in a country with a significantly high electric power price such as Japan, which is not preferable. Therefore, as a method for economically melting and refining scrap without using an electric furnace, there is a method for melting and refining scrap using inexpensive carbonaceous materials by utilizing the surplus production capacity of a converter having a high acid transfer capacity. It has come to be considered.

Under such circumstances, generally, by utilizing the existing upper-bottom-blown composite blowing converter, the increase in equipment can be suppressed to a low level, and at the same time, the fire species charged in the furnace together with scrap can be used. After igniting, a method of melting and refining while charging carbonaceous material as a heat source from above the furnace at the time of blowing from the top and bottom is proposed. When scrap is melted using this top-blown or top-blown converter, the raw material for the carbonaceous materials and scrap is usually put into the slag by extending the scrap feeding pipe from the furnace shoulder or above the furnace. It is the actual situation that the method of doing is done.

[0004]

As described above, when the raw material is charged from the furnace shoulder or on the furnace, splash of molten slag is generated when the charged raw material is dropped, and the FeO-containing slag is deposited on the refractory surface of the furnace inner wall. Adhesion may cause refractory wear, or part of the slag in the furnace may be cooled when the raw material is charged, resulting in temperature unevenness and flow unevenness, disturbing the slag surface and causing gas flow and reaction in the furnace. There is a problem that the steady state is disrupted and the scrap or iron ore penetrates the slag layer where it heats.

[0005]

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive studies by the inventors, as a result, the raw material was introduced from the outside of the furnace to the inside of the furnace, and the tip end of which had a gentle inclination. The pipe is connected and penetrated in a range corresponding to the furnace mouth, the furnace shoulder, and the furnace belly, and at least a part of the charging hole at the tip of the charging pipe is arranged so as to be in contact with the molten metal bath, the molten slag layer, or both. By doing so, it is possible to reduce the throwing and dropping speed of the scrap as much as possible, and at the same time, allow the scrap to stay for a long time near the heat supply source, which can prevent the splash of molten slag and prevent the molten slag layer and molten slag. Steel that can suppress the disturbance of the molten metal bath interface, can also prevent the temperature unevenness and flow unevenness of the molten slag, and can prevent the secondary combustion rate and heat deposition efficiency from decreasing or fluctuating. Clap melting furnace and to provide the dissolution method.

The gist of the invention is as follows: (1) In a top-blown or top-blown-blown steel scrap melting furnace, a scrap charging pipe inclined obliquely upward to the furnace belly, furnace mouth, or furnace shoulder is used in the furnace of the melting furnace. Steel scrap melting furnace characterized by being installed up to (2) In a top-blown or top-blown steel scrap melting furnace, a scrap charging pipe inclined obliquely upward is arranged in the furnace belly. (3) The scrap input pipe has two or more types of inclination angles with respect to the horizontal plane, and the inclination angle is smaller as the tip of the scrap input pipe on the side in contact with the slag is closer (1) or (2) The steel scrap melting furnace as described above.

(4) In the top-blown or top-bottomed steel scrap melting method, the melting furnace described in any one of (1) to (3) is used to add carbonaceous material to form scrap while forming slag. When melting, the molten slag is introduced into a part or all of the connection part between the scrap charging pipe and the melting furnace, and the steel scrap charged into the scrap charging pipe by the molten slag is retained to scrap in the molten slag. A steel scrap melting method characterized by accelerating preheating and melting of steel scrap.

[0008]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic sectional view of a steel scrap melting furnace according to the present invention. As shown in FIG. 1, the melting furnace 1 is, for example, a top-blown melting furnace lined with a refractory material or a panel having a water-cooled structure, and includes an oxygen top-blown lance 2. If the melting furnace is an electric furnace, the oxygen top-blown lance 2 serves as an electrode. Therefore, in the case of oxygen top blowing refining, oxygen gas is blown from the oxygen top blowing lance 2 onto the molten slag 3 on the molten metal 4.

On the other hand, the scrap 7 is loaded into the furnace abdomen through the scrap charging pipe 5 which is inclined obliquely upward. In this case, a pusher 8 or a belt conveyor is connected to the scrap input pipe 5, and the scraper 8 is loaded into the scrap input pipe. Further, the upward inclination angle θ at the connecting portion between the scrap charging pipe 5 and the melting furnace 1 arranged obliquely upward in the furnace belly is set within the range of 3 to 85 °. If the angle is less than 3 °, the slipping speed of the scrap in the charging pipe 5 becomes too slow and the scrap is clogged in the charging pipe 5, or the melt flowing from the melting furnace 1 into the charging pipe 5 flows in and out. The slag is not replaced smoothly, part of the molten slag stays and cools, and even after the scrap is melted or melted in the charging pipe 5, it naturally moves to the melting furnace 1 side along the inclination angle. No longer
Problems such as fusion will occur. Conversely, the tilt angle θ
If it exceeds 85 ° by increasing too much, there is not much difference between the scrap movement / falling speed (collision energy to the molten slag layer) when the scrap is charged from directly above the melting furnace 1, and the hardening of the present invention can be performed. I can not expect it.

[0010] Further, although one type of inclination angle θ may be inexpensive as a capital investment cost, the viewpoint of securing the retention time at the tip of the charging pipe 5 (the portion where the molten slag exists) and the charging pipe 5
Taking into consideration the operational problems such as scrap fusion and clogging at the rear end (the part where the molten slag is not present), the inclination angle θ ₁ at the tip of the charging pipe 5 and the inclination angle θ _{2 at the} rear of the charging pipe 5 are θ ₁ <Θ ₂ is preferable. Conversely, reducing the injection tube 5 the rear of the inclination angle theta _2, can be ensured scrap residence time here, it is possible to sufficiently secure the scrap preheating time and temperature due to high temperature gas, the conventional most feeding pipe theta ₁ > Θ ₂ . Therefore, the above θ ₁ <θ
₂ satisfies the inclination angle theta ₂ of the further inclination angle theta ₃ site at the rear of the feeding pipe 5 rear adding at least one, theta _2> theta
Good as ₃ . Of course, the tilt angles are gradually changed to θ ₁ , θ ₂ ,
Instead of providing θ ₃ , a curved surface having at least one type of curvature may be used.

With such a structure, the molten slag from the melting furnace is introduced into and discharged from a part or all of the connecting portion 6 between the scrap charging pipe 5 and the melting furnace 1, and the molten slag is introduced into the tip portion thereof. Steel scrap is introduced into the scrap input pipe 5 from the side opposite to the connecting portion, and the steel scrap is retained in the scrap input pipe 5 by the flowing molten slag, whereby the scrap is preheated in the molten slag.
The molten, melted, and further melted metal is heated and agitated by the fluidized slag so as to drop into the molten metal bath in the melting furnace at any time, and is accumulated in the melting furnace 1. Further, a gas blowing tuyere 9 may be provided above the scrap feeding pipe 5 to blow hot gas or a gas such as CO, LPG or O ₂ which becomes a combustion gas to heat the gas, and the gas blowing tuyere 9 Carbonaceous material may be added at the same time as the higher temperature gas. That is, the connection portion of the scrap charging pipe 5 or the charging hole 6 is extended to the vicinity of the combustion point of the top-blown oxygen and fossil fuel, the high temperature gas and the slag are mixed with stirring, and the mixture is introduced into the scrap charging pipe from the charging hole. Always flow in and out. In this way, the steel scrap is preheated, melted and melted at the tip of the scrap feeding pipe to enhance productivity.

Regarding the composition of the molten slag introduced to the tip portion of the scrap charging pipe 5, the combustion heat at the combustion point (hereinafter referred to as the fire point) between the top-blown oxygen and the carbonaceous material is supplied to the molten metal bath in the melting furnace 1 and charged. A heat transfer medium is required to transfer heat to the scrap retained in the pipe 5, which may be conventional carbonaceous material (such as char) or granular iron (Fe-C-based or FeO), but if possible, granular It is preferable to coexist both iron and carbonaceous material. If only granular iron is used, it will eventually be oxidized into FeO, the thermal conductivity will decrease, and the charging pipe 5 and the melting furnace 1 will
This is because the refractory on the inner wall is worn away and the thermal conductivity is low with carbon material alone.
This is because it is possible to secure a good heat medium with high thermal conductivity while preventing decarburization.

The reason why it is preferable that at least a part of the charging hole at the tip of the charging pipe 5 is in contact with the molten slag layer, the molten slag-molten metal interface or the molten metal bath is When it is arranged in the slag layer, the high temperature oxidizing gas does not directly flow into the charging pipe 5,
This is because the inner wall can be protected, and the scrap heating efficiency is better if the scrap is retained in the molten slag at high temperature and brought into direct contact with it. When slag and gas at the same temperature are compared, molten slag is more efficient in consideration of the contact time with scrap.

At a position where there is no slag in the charging pipe 5,
As for the method of preheating scrap, the method of using high temperature exhaust gas generated in the melting furnace 1 is the most energy-saving. Therefore, if the upper side of the charging hole of the charging pipe 5 is taken out from the molten slag layer, high temperature exhaust gas flows in from the upper side of the charging hole, and there is molten slag in the lower side of the charging hole and heat can be directly applied to scrap. Becomes The lower side of the charging hole 6 is below the molten slag layer, that is, the molten slag-molten metal interface or the molten metal bath is used when molten and liquefied scrap is dropped from the charging hole 6 and flows into the melting furnace 1. If it is cooled by another molten slag, carbonaceous material, or low temperature gas such as unburned oxygen again, it causes heat loss and should be avoided. Therefore, the molten metal bath should be introduced below the charging hole 6. Is preferred.

FIG. 2 is a schematic sectional view of a melting furnace showing another embodiment according to the present invention. FIG. 2 shows a melting furnace 1 similar to FIG.
Is equipped with an oxygen top blowing lance 2, and oxygen gas is blown onto the molten slag 3 on the molten metal 4 from the oxygen top blowing lance 2. Charcoal materials such as coal and coke and scrap 7 are charged into the furnace belly through a scrap charging pipe 5 inclined obliquely upward. The upper side of the charging hole at the tip of the charging pipe 5 was arranged above the upper surface of the slag layer, and the lower side of the charging hole 6 was arranged inside the molten slag layer 3. In this case, a pusher 8'is provided below the scrap input pipe 5, and scraps and the like are loaded into the scrap input pipe using this pusher 8 '. Further, oxygen gas is blown from the gas blowing tuyere 9 arranged in the scrap feeding pipe 5 in the same manner as in the melting furnace to preheat and melt the scrap and the molten slag 3.

[0016]

[Example] The lower end of the scrap feeding pipe inlet was located 0.5 m above the lower surface of the slag layer, and the upper end of the scrap feeding pipe inlet was located 0.5 m above the upper surface of the slag layer. The melting operation was performed with the slag layer having a thickness of 1.5 m. High-temperature exhaust gas of 1850 ° C generated in the furnace was introduced into the inlet of the scrap feeding pipe, and this scrap was preheated to 1300 ° C or higher at the portion where the slag and the high temperature gas mixed in from the inlet of the connection part were preheated and then fed into the furnace. . Part of it melted by preheating and carburizing to become a liquid and flowed in. As a result, the production speed was improved from the conventional 100 t / h to 150 t / h. By arranging the scrap charging pipe connected to the melting furnace in this way, it is possible to preheat and melt the scrap by the molten slag in the scrap charging pipe, thereby improving the productivity.

[0017]

As described above, the raw materials such as scrap and iron ore are introduced into the melting furnace through the scrap introducing pipe connected to the melting furnace according to the present invention, so that they are introduced from the conventional shoulder and the furnace. FeO can be manufactured in advance in the scrap layer as compared with the above, and there is no scattering of slag droplets and slag cooling when the raw material is dropped,
Moreover, it penetrates the hot slag layer and disturbs the slag surface,
Scrap can be efficiently melted without changing the secondary combustion rate and the heat deposition efficiency, and productivity can be improved, which is an extremely excellent industrial effect.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a steel scrap melting furnace according to the present invention,

FIG. 2 is a schematic sectional view of a melting furnace showing another embodiment according to the present invention.

[Explanation of symbols]

 1 Melting furnace 2 Oxygen top blowing lance 3 Molten slag 4 Molten metal 5 Scrap charging pipe 6 Charging hole 7 Scrap 8, 8'pusher 9 Gas blowing tuyere

Claims (4)

[Claims] 1. In a top-blown or top-blown-blown steel scrap melting furnace, a scrap charging pipe inclined obliquely upward is installed at the furnace belly, furnace mouth or furnace shoulder so as to extend into the furnace of the melting furnace. And steel scrap melting furnace. 2. A steel scrap melting furnace in a top-blown or bottom-blown steel scrap melting furnace, wherein a scrap charging pipe inclined obliquely upward is disposed in a furnace belly. 3. The scrap input pipe has two or more kinds of inclination angles with respect to a horizontal plane, and the inclination angle is smaller as the scrap input pipe is closer to the tip of the scrap input pipe on the side in contact with the slag. The steel scrap melting furnace according to 1 or 2. 4. In a method for melting top-blown or bottom-blown steel scrap, carbon material is added using the melting furnace according to any one of claims 1 to 3 to melt scrap while forming slag. At this time, molten slag is introduced into a part or all of the connection part between the scrap input pipe and the melting furnace, and the steel scrap injected into the scrap input pipe is retained by the molten slag to preheat the scrap in the molten slag. , A method for melting steel scrap, characterized by accelerating the melting.