A method for increasing slag temperature when smelting metal-containing minerals in an induction furnace

Abstract

The invention belongs to the field of metallurgy, and discloses a method for increasing the slag temperature when an induction furnace is used to smelt metal-containing minerals. During the induction furnace smelting process, when the induction furnace has a preset volume of molten metal, a graphite ring is placed in the induction furnace, and the graphite ring floats on the surface of the molten metal, and then the metal-containing minerals required for smelting metals are continuously added to the induction furnace. The invention adds a graphite ring to the melt in the induction furnace, utilizes the graphite ring to generate an induced current in a magnetic field, and enables the graphite ring to heat the slag using its own resistance and the Joule heat generated by the induced current, so that the slag temperature is increased.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy, and in particular relates to a method for increasing the slag temperature when an induction furnace is used to smelt metal-containing minerals. Background Art

[0002] Induction furnaces are mainly used for metal smelting. According to the power frequency used, they can be divided into three types: high-frequency induction furnaces, medium-frequency induction furnaces, and industrial-frequency induction furnaces. Induction furnaces use the principle of induction heating to melt metals. To achieve induction heating, two conditions must be met: first, alternating current must be passed through the induction coil. Second, the heated material in the induction coil must be conductive. If the heated material is non-conductive, an electrical conductor must be used as a heating element, and the heat generated by the conductor is used to indirectly heat the non-conductive material.

[0003] There are two types of crucible (furnace lining) materials for induction furnaces. One is non-conductive refractory materials, such as quartz refractory materials, magnesia spinel refractory materials and magnesia refractory materials. Such lining materials themselves are not conductive. If the material in the crucible is to be heated, the material in the crucible must be conductive. The other crucible material is conductive material, such as metal crucibles, graphite crucibles, etc. as lining materials. Such crucible materials themselves are conductive. Such materials can be heated by the principle of electromagnetic induction in the induction furnace. The heated crucible then indirectly heats the material in the crucible. Non-conductive materials can be melted in a crucible made of conductive materials.

[0004] Induction furnaces use electric heating, which has fast heating speed and low pollution. However, since it can only heat conductive materials, it is widely used in the smelting of metals with relatively small amounts of slag (such as steelmaking) or no smelting slag (such as smelting alloys and melting metals). It is less used in the extraction of metals from minerals that produce large amounts of smelting slag and high slag melting temperatures. The main reason for its less application is that a large amount of slag is produced during the smelting process of the induction furnace. Since the slag cannot be heated above the melting temperature of the slag, the slag viscosity is high. On the one hand, the high slag viscosity will cause the slag to adhere to the inner wall of the crucible and gradually accumulate and thicken. The slag accumulation on the inner wall of the crucible will cause "shelf material" to appear, making it impossible to add subsequent materials; secondly, the slag viscosity makes it difficult to separate the slag from the metal during the smelting process, and a large amount of metal exists in the slag, resulting in a low metal recovery rate. The reasons why the slag temperature is low when the induction furnace produces a large amount of metal smelting slag are: 1) Before the slag reaches the melting temperature, it is a non-conductor and no induced eddy current can be generated in the non-conductor. Therefore, the magnetic induction of the induction furnace cannot heat the slag; 2) The heat of the slag mainly comes from the heat transfer of the molten metal at the bottom of the induction furnace to the slag. The thermal conductivity of the slag is low. At the same time, the upper surface of the slag is in contact with the outside air and continuously dissipates heat to the air. Therefore, although the temperature of the molten metal at the bottom of the induction furnace is relatively high, the temperature of the slag covering the surface of the molten metal is still relatively low, and it is still difficult for the slag to reach the melting temperature.

[0005] If metal-containing minerals are used as raw materials and an induction furnace is used to smelt the metal in the minerals, it is necessary to consider how to increase the temperature of the smelting slag so that the temperature of the slag reaches above the melting temperature. When the slag temperature reaches above the melting temperature, the fluidity of the slag increases, and the slag becomes a conductor. The induced magnetic field generated by the induction furnace can heat the slag to ensure the smooth progress of the smelting process. In order to increase the temperature of the slag, the patent "A vortex stirring molten reduction ironmaking method (CN201610854514.2)" uses the process of heating molten iron to above 1450°C and continuously stirring the molten iron in the center during the ironmaking process using an induction furnace with iron-containing mineral raw materials, so that the molten iron forms a vortex with a height-to-diameter ratio of 0.5 to 2.5, and uses the vortex generated by the stirring of the molten iron to increase the heat transfer between the molten iron and the slag, so that the temperature of the smelting slag reaches above the melting temperature, so that the smelting slag has better fluidity and achieves better separation of slag and iron. However, stirring the high-temperature molten metal requires the agitator to be made of a material that can withstand high temperatures, and for the induction furnace, the structure of the induction furnace is complicated. Therefore, it is necessary to explore a more convenient method to increase the temperature of the smelting slag. Summary of the invention

[0006] Based on the problem that it is difficult to increase the temperature of slag generated when using an induction furnace to smelt metal-containing mineral raw materials, the present invention proposes a method for increasing the slag temperature when using an induction furnace to smelt metal-containing minerals. The present invention can solve the problems of low slag temperature, high slag viscosity, complex equipment, etc. when a large amount of slag is generated during the smelting of metal minerals in the existing induction furnace, so that the induction furnace can be used to smelt metal-containing minerals to produce metals.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems: A method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace comprises the following steps: During the induction furnace smelting process, when the induction furnace has a preset capacity of molten metal, a graphite ring is placed in the induction furnace, the graphite ring floats on the surface of the molten metal, and then metal-containing minerals required for smelting metal are continued to be added into the induction furnace.

[0008] Preferably, when the induction furnace needs to discharge molten metal and carry out the next smelting, the graphite ring is taken out, and then the induction furnace is first deslagging, and then the molten metal is released after the slag is discharged. When the molten metal is released, a preset volume of molten metal is retained in the induction furnace, and then the graphite ring is placed in the induction furnace, and the graphite ring floats on the surface of the molten metal. Then, materials required for smelting metal are continuously added into the induction furnace to carry out the next smelting.

[0009] Preferably, during the induction furnace smelting process, the induction furnace is in a reducing atmosphere.

[0010] Preferably, during the induction furnace smelting process, the induction furnace is in a vacuum environment.

[0011] Preferably, the metal-containing minerals smelted in the induction furnace include iron-containing minerals, lead-containing oxides or copper-containing oxides.

[0012] Preferably, the outer diameter of the graphite ring is 5-10 cm smaller than the inner diameter of the middle portion of the induction furnace crucible.

[0013] Preferably, the cross-sectional shape of the graphite ring is rectangular or circular.

[0014] Preferably, the cross-sectional area of ​​the graphite ring is not less than 9.42 cm 2 .

[0015] Preferably, when the graphite ring is placed in the induction furnace, the plane of the graphite ring is perpendicular to the vertical axis of the induction furnace.

[0016] Preferably, the preset volume of the molten metal is 0.3 to 0.4 times the volume of the induction furnace crucible, and the metal constituting the molten metal is the metal to be smelted and extracted from the metal-containing ore to be smelted.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The method of the present invention for increasing the slag temperature when the induction furnace is used to smelt metal-containing minerals is to utilize the conductivity of the graphite ring and its ability to generate induced potential and heat in a magnetic field, and place the graphite ring in the melt (including molten metal and slag) of the induction furnace. At this time, the graphite ring floats on the surface of the molten metal, and can heat the molten metal and slag at the same time, thereby increasing the temperature of the slag, and then realizing the induction furnace smelting of metal minerals that produce more smelting slag, and extracting the metal from the mineral. The method is simple and easy to implement. It can be seen that the present invention has well solved the problem in the prior art that a large amount of slag is generated when an induction furnace is used to smelt metal-containing raw materials, and the slag temperature is difficult to increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic structural diagram of an induction furnace when the method for increasing the slag temperature during smelting of metal-containing minerals in an induction furnace is implemented.

[0019] Figure 2 This is a smelting photo of the induction furnace smelting metal-containing minerals without adding graphite rings in an embodiment of the present invention.

[0020] Figure 3 This is a smelting photo of a metal-containing mineral smelted in an induction furnace after adding a graphite ring in an embodiment of the present invention.

[0021] In the figure, 1 is slag, 2 is graphite ring, 3 is molten metal, and 4 is induction furnace. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0023] See also Figure 1 The method of the present invention for increasing the slag temperature when an induction furnace is used to smelt metal-containing minerals is to place a graphite ring into the induction furnace during the induction furnace smelting process, and use the heat generated by the graphite ring to heat the slag on the surface of the molten metal in the induction furnace, thereby increasing the slag temperature.

[0024] The principle of the method of the present invention is that graphite is a conductor, and when the magnetic field generated by the induction furnace coil passes through the graphite, an induced potential is generated in the graphite. The graphite is made into a ring shape, and an induced current can be generated in the graphite ring. The induced current in the graphite ring and the resistance of the graphite ring can generate Joule heat, thereby making the graphite ring hot. The graphite ring contacts with the slag, and the heat released by the graphite ring can heat the slag, thereby increasing the temperature of the slag. In the above scheme of the present invention, since the graphite ring floats on the surface of the molten metal, the graphite ring is in contact with both the metal and the slag. When smelting metals that can dissolve carbon, the carbon content in the metal can be increased. For example, when smelting iron-containing minerals, the carbon content in the iron produced by smelting will increase; the graphite ring is consumed faster in an oxidizing atmosphere, so this method is suitable for smelting metals in a reducing atmosphere or a vacuum environment; when smelting metals that do not dissolve carbon, the effect of the carbon in the graphite ring on the increase of carbon in the metal can be ignored, such as smelting lead from raw materials containing lead oxides, smelting copper from materials containing copper oxides, etc.

[0025] In the above scheme of the present invention, the outer ring size of the graphite ring is 5-10 cm smaller than the inner diameter of the induction furnace crucible near the middle; the cross section of the graphite ring can be rectangular, circular or other arbitrary shapes. If there is a corner at the cross section, an arc is used for transition; the cross section area of ​​the graphite ring is not less than 9.42 cm 2 When placing the graphite ring, the plane of the graphite ring (i.e. the surface parallel to the radial direction) is placed in the furnace perpendicular to the vertical axis of the induction furnace.

[0026] Example In this embodiment, the iron-rich mineral obtained by magnetic separation of copper smelting slag is referred to as iron concentrate. The iron therein is smelted by an induction furnace. The composition of the iron concentrate is shown in Table 1 (the content is in percentage by mass): Table 1

[0027] Smelting raw materials ingredients: It can be obtained from the composition of the material (i.e. iron concentrate), which contains more SiO 2 During smelting, flux and carbonaceous reducing agent are added to the raw materials to form slag. During smelting, flux and carbonaceous reducing agent are added to the materials. The material ingredients are as follows: Iron-containing smelting slag ingredients Fe :n C =1:(1.1~1.3) (molar ratio); n SiO2 :n CaO =1:(1.1~1.2) (molar ratio), add 5% of the total mass of sodium carbonate, mix the materials thoroughly and use a ball press to press them into a rectangular block with a length × width × height = 30 × 30 × 20 mm. The induction furnace smelting is carried out in a medium frequency induction furnace with a crucible size of Φ400 × 500 mm, and the induction furnace lining material is quartz refractory material.

[0028] Graphite ring size: The outer diameter of the graphite ring is 390mm, the cross section of the graphite ring is circular, and the cross section diameter is 50mm.

[0029] Smelting process: First, add the scrap steel into the induction furnace, start the power of the induction furnace to start heating, and after the scrap steel is heated into liquid, the volume of the molten steel accounts for 0.3~0.4 times the volume of the crucible. Put a graphite ring into the molten steel, and then add the material pressed into a rectangular block into the induction furnace for smelting.

[0030] Without graphite ring, when the molten steel is heated to 1450℃, the slag temperature is up to 1150℃ (detected by fast micro thermocouple), see Figure 2 As the slag temperature is low, the slag is viscous and adheres to the furnace lining. As the smelting time increases, the amount of slag adhered to the surface of the molten steel gradually increases until the surface of the molten steel is completely occupied by the smelting slag ( Figure 2 The slag temperature in the darker areas is lower), which makes it impossible to continue feeding and the smelting process cannot continue.

[0031] When adding graphite ring, when molten steel is heated to 1450℃, refer to Figure 3 The slag has melted into liquid (detected by fast micro-thermocouple), the temperature is high and the fluidity is good (due to the high temperature in the induction furnace, it is impossible to Figure 2The operator can gradually add the rectangular blocks and continue smelting. When the molten steel and slag melt fill 3 / 4 of the crucible volume, take out the graphite ring, open the induction furnace tilting mechanism, first put the smelting slag on the upper part of the crucible into the slag pot, and then put the molten iron in the lower part of the crucible into the iron ladle. When releasing the iron, not all the molten iron can be released, and some molten iron is retained in the crucible. The amount of molten iron retained accounts for 0.3~0.4 times the volume of the crucible. After the molten iron is released, adjust the induction furnace to the smelting position, put the graphite ring in the crucible, and operate the second furnace.

[0032] It can be seen from the above scheme that the present invention can solve the problems of low slag temperature, high slag viscosity, complex equipment, etc. when a large amount of slag is generated during the smelting of metal minerals in the existing induction furnace, so that the induction furnace can be used to extract metals from minerals with large slag production.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace, characterized in that: The process includes the following: During the induction furnace smelting process, when the induction furnace has a preset capacity of molten metal, a graphite ring is placed in the induction furnace, the graphite ring floats on the surface of the molten metal, and then metal-containing minerals required for smelting metal are continued to be added into the induction furnace.

2. A method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: When the induction furnace needs to release molten metal and carry out the next smelting, the graphite ring is taken out, and then the induction furnace is first slaged, and then the molten metal is released after the slag is released. When releasing the molten metal, a preset capacity of molten metal is retained in the induction furnace, and then the graphite ring is put into the induction furnace. The graphite ring floats on the surface of the molten metal, and then the materials required for smelting metal are continued to be added into the induction furnace for the next smelting.

3. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: During the induction furnace smelting process, the induction furnace is in a reducing atmosphere.

4. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: During the induction furnace smelting process, the induction furnace is in a vacuum environment.

5. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: The metal-bearing ores smelted in the induction furnace include iron-bearing ores, lead-bearing oxides or copper-bearing oxides.

6. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: The outer diameter of the graphite ring is 5-10 cm smaller than the inner diameter of the middle position of the induction furnace crucible.

7. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: The cross-sectional shape of the graphite ring is rectangular or circular.

8. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: The cross-sectional area of ​​the graphite ring is not less than 9.42 cm 2 .

9. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: When placing the graphite ring into the induction furnace, make sure the plane of the graphite ring is perpendicular to the vertical axis of the induction furnace.

10. The method for increasing the slag temperature when smelting metal-containing minerals in an induction furnace according to claim 1, characterized in that: The preset volume of the molten metal is 0.3 to 0.4 times the volume of the induction furnace crucible, and the metal constituting the molten metal is the metal to be smelted and extracted from the metal-containing ore to be smelted.

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