CN217110400U - Bottom electrode structure of direct current arc furnace - Google Patents

Abstract

The application discloses direct current arc furnace bottom electrode structure, bottom electrode structure include that the vertical interval of several installs in the metal conducting element of stove bottom, metal conducting element between the whole refractory material that fills in interval, the bottom of interval is filled by thermal-insulated insulation material, and the middle part is filled with bottom electrode ramming mass, the upper portion at interval is filled by electrically conductive refractory material. By adopting the conductive refractory material, the metal bottom anode is changed into the composite bottom anode which combines metal and the conductive refractory material, and the irreparable metal bottom anode is changed into the bottom anode which can be repaired in a cold state and a hot state, thereby greatly prolonging the service life of the bottom anode, improving the operation rate of the electric furnace steelmaking, reducing the steelmaking cost and improving the utilization rate of equipment. On the other hand, the heat dissipation is obviously reduced by adopting the bottom layer of heat-insulating refractory material, so that the bottom electrode is not required to be cooled by air, and the safety and the energy-saving effect are improved.

Description

Bottom electrode structure of direct current arc furnace

Technical Field

The invention relates to the technical field of direct current electric arc furnaces, in particular to a direct current electric arc furnace bottom anode, and specifically relates to a direct current electric arc furnace bottom electrode structure and application thereof.

Background

To date, there are four types of dc arc furnaces:

(1) ABB type: the whole furnace bottom is built by conductive magnesia carbon materials. This structure has the following undesirable consequences: a) the ideal state is that the current is uniformly distributed on the bottom of the furnace, which is difficult to realize in practice. During construction and use, especially after hot patching, the furnace bottom is difficult to achieve uniform thickness and consistent density. In addition, the current has the characteristic of low resistance channel, thereby causing the current density distribution at the bottom of the electric furnace to be uneven. At the center of the furnace bottom (right under the graphite cathode) and at a place with small resistance, the calorific value (calorific value Q ═ V2/R) is large, and the current density is large, so that local overheating is caused, and high-temperature redox reaction of MgO + C ═ mg (g) + co (g) is caused, and local erosion is too fast; b) the temperature in the foot around the bath decreases, forming the so-called cold spot, which is proven by practice; c) the whole furnace bottom is built by using the conductive refractory materials, the heat conduction is fast, the temperature of the furnace bottom is high, and particularly, the central part is easy to overheat. Air cooling of the bottom electrode area is required and energy consumption is high. The furnace has the advantages of capability of cold-state and hot-state repair, and long service life of the bottom electrode.

(2) Clecim type: 1-4 conductive metal rods are arranged in the center of the furnace bottom, the outer ends of the steel rods are cooled by water, the steel rods are sleeved by prefabricated refractory bricks, and the rest part of the furnace bottom is made of non-conductive magnesium-calcium dry materials. This structure has the following disadvantages: a) the current is only concentrated in the center of the furnace bottom, so that the center of the furnace bottom is overheated, molten steel flows quickly, and the electrode part of the furnace bottom cannot be repaired thermally, so that the service life of the bottom electrode is short and is generally only 500-1500 heats. There are also many production stops to maintain; b) the cold spots are more likely to appear under the furnace wall foot. In short-flow electric arc furnace steelmaking, because the tapping temperature is lower, the phenomenon that scrap steel under the furnace wall still does not melt during tapping is often caused, the steelmaking time is prolonged, and the uniformity of temperature and components is reduced; c) this poses a safety risk because the steel bar needs to be water cooled. The irreparable defect that the service life of the bottom electrode is low and the steel leakage risk is high is the most prominent defect.

(3) Type MAN-GHH and (4) VOEST-ALPINE, with metal contact pins and steel plates distributed on the bottom of the furnace, respectively. The distribution of current at the furnace bottom is better than that of Clecim. However, due to the characteristic of the current shortcut (low resistance path), in fact, the current density distribution of the hearth of the structure is still high in the center and low outwards, and the electric arc burns in the center of the molten pool, so that the wall foot far away from the burning point of the electric arc still has a cold spot, and a hot spot also appears in the corresponding center (which is better than the Clecim type); the other disadvantage is that the bottom electrode of the structure can not be hot-repaired, so the service life is shorter and is only 500-1200 heat level. As compared with the MANs-GHH type and VOEST-ALPINE type bottom anodes, eddy current phenomenon is improved well because the VOEST-ALPINE type is a thin metal sheet and does not easily generate induced current. Therefore, the bottom electrode is less likely to generate heat and has a smaller melting depth. Thus, of these two bottom electrodes, the VOEST-ALPINE type should be better.

The applicant has noticed that the patent "bottom electrode of a direct current electric arc furnace" related to the present application (application No.: 201410425489.7). The bottom electrode of the patent is a metal rod at the lower part, a graphite block at the middle part and a magnesia carbon brick at the upper part. Magnesia and graphite ramming mass are used between the magnesia carbon brick and the graphite block. This patent proves to be difficult to implement successfully from the following points. 1) No indication is made as to whether the upper magnesia carbon brick is conductive. This is part of the electrode and requires not only electrical conductivity but also a sufficiently low resistivity. Otherwise, even if the magnesia carbon brick is conductive, the magnesia carbon brick can not normally operate as long as the conductivity is insufficient; 2) the magnesia-carbon brick and the graphite block are made of magnesia and graphite, and no generation is caused. Also whether this material is conductive, or just conductive, and whether the conductivity meets the requirements as an electrode, is not a trade-off. The electrode material can not be used as an electrode material, or the normal operation of the direct current electric furnace can not be ensured at all, even the direct current electric furnace can not be operated; 3) under the condition that bulk materials consisting of magnesia carbon bricks, magnesia and graphite cannot operate, the bulk materials are either not conductive or have weak conductivity and can be broken down at any time, so that the graphite block is exposed in molten steel, the graphite block is quickly dissolved in the molten steel, a large pit is formed under an electrode, the temperature of a furnace bottom is overhigh, and safety accidents can occur at any time; 4) whether the graphite block and the metal rod form firm static fit or not and the thermal expansion difference between the graphite block and the metal rod is large can cause large interface resistance, so that the furnace bottom generates heat, the electrode loss is too fast, and the service life is short. In summary, such dc arc furnace bottom anodes either fail to operate or, if they do, can result in excessive bottom anode wear, excessive furnace bottom temperatures and short life spans.

To date, all four types of dc arc furnace bottom electrodes have not been concerned with maintaining temperature. Because the bottom anode is an electrical conductor and is also a thermal conductor. This results in rapid heat dissipation from the bottom electrode and excessive temperature in the bottom electrode can. To solve this problem, forced cooling measures are taken. Such as air cooling, water spray cooling, copper cold jacket water cooling, and the like. This not only increases the energy consumption, but also brings the hidden danger for the safety simultaneously.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a heat preservation type direct current arc furnace bottom electrode structure which can prolong the service life of a bottom electrode and can carry out hot repair and cold repair simultaneously.

In order to achieve the above object, the bottom electrode structure of the direct current arc furnace of the present invention is as follows:

the utility model provides a direct current electric arc furnace bottom electrode structure, bottom electrode structure be compound end anode structure, bottom electrode structure include that the vertical interval of several installs the metal conductive element at the bottom of the furnace, the whole refractory material that fills in interval between the metal conductive element, the bottom at interval is filled by thermal-insulated insulation material, and the middle part is filled with bottom electrode ramming mass, the upper portion at interval is filled by electrically conductive refractory material.

Preferably, the metal conductive element is a steel sheet or a steel needle and the combination of the steel sheet and the steel needle, and the height of the metal conductive element is greater than 2/3 of the thickness of the furnace bottom.

Preferably, the overall height of the interval filled by the heat insulation material is less than or equal to 150mm and is not more than 25% of the thickness of the furnace bottom.

Preferably, the bottom electrode ramming material is a dry type alkaline fire-resistant ramming material, and the thickness of the bottom electrode ramming material is more than or equal to 40-60% of the thickness of the furnace bottom.

Preferably, the refractory raw material is formed by combining a plurality of magnesia, corundum, magnesia-alumina spinel, graphite, metal aluminum powder or silicon powder.

Preferably, the contact area (m) between the conductive refractory material and the metal conductive element ² ) The current intensity (KA) is not less than 0.054 multiplied.

Preferably, the performance parameters of the heat insulation material are as follows: the resistivity is more than or equal to 5 multiplied by 104 omega, the heat conductivity coefficient is less than or equal to 0.3w/(mk), and the refractoriness is more than or equal to 1790 ℃.

Preferably, a conductive repairing material can be laid on the top of the metal conductive element.

The bottom electrode of the direct current arc furnace is mainly used for steel making, non-ferrous metal smelting and ferroalloy submerged arc furnaces.

The beneficial effect of this application does: the application discloses direct current electric arc furnace bottom electrode structure, even in hot operation production process, when meetting the condition such as end anode erosion fast and lead to stove bottom temperature too high, can go out clean molten steel, with oxygen rifle sweep clean end anode upper surface behind the slag, with the hot repair material drop into end anode above can, this hot feed supplement will be under hot condition self-leveling to the carbonization, with original incomplete end anode firmly combine together. The process is only 20-50 min, and then the charging and steelmaking can be carried out. Therefore, the hot patching can be carried out by using the conductive hot patching material at any time according to specific conditions; when the furnace such as a steel tapping hole, a slag changing line and the like is cooled down, the bottom anode can be simultaneously cold repaired. After the furnace is cooled down, the steel slag on the surface of the bottom anode is cleaned, and is tamped and thickened by a conductive magnesium (calcium) carbon tamping material to reach the original thickness so as to maintain the length of the bottom anode and the temperature of the furnace bottom at a safe operation level.

The electrode structure at the bottom of the direct current arc furnace is additionally provided with a heat preservation part. The high thermal conductivity characteristic of the electrically conductive metal element is eliminated. Here, it is preferable that the thickness of the heat insulating layer is within a range of 10 to 150 mm. Thus, the water-cooled or air-cooled furnace bottom electrode is not needed, and the safety and the energy conservation are ensured.

Drawings

FIG. 1 is a front sectional view of a DC arc furnace bottom electrode structure of the present application.

The electric furnace comprises a graphite electrode 1, an electric furnace shell 2, a conductive repairing material 3, a magnesia-carbon brick lining 4, a permanent layer 5, a magnesia-calcium ramming material 6, a conductive refractory material 7, a metal electrode 8, a bottom electrode periphery magnesia brick 9, a heat insulation material 10 and a bottom electrode ramming material 11.

Detailed Description

In order to make the technical means, creation features, achievement purposes and functions of the present invention easy to understand, the present invention will be further explained with reference to the accompanying drawings and the detailed description thereof.

The first embodiment is as follows:

for a 40t steel needle type direct current electric arc furnace, after 86 metal anode steel needles 8 with the diameter of 45mm are installed, 100mm thick heat insulation bulk materials are rammed to serve as heat insulation materials 10, and then 300mm thick dry magnesium-calcium ramming materials are rammed to serve as bottom electrode ramming materials 11. It is to be noted that in order to densify the bottom electrode ramming mass 11, the thickness of each charge must not be greater than 100mm, the ramming operation is carried out using special vibrating ramming equipment. Then adding a magnesia carbon conductive ramming material as a conductive refractory material 7 for construction, wherein the coincidence thickness of the magnesia carbon conductive ramming material and the steel needle is 400 mm. The construction method of ramming is the same as that of the dry magnesium-calcium ramming material. Must be compacted. This is important not only for corrosion resistance but also for electrical conductivity. Then, a magnesia-carbon brick lining 4 is built, and the periphery and the slope of the electric furnace are rammed by using a dry magnesia-calcia ramming material. Thus, the steel can be made by adding steel-making raw materials and supplying power. Under the condition that the bottom electrode copper plate is naturally cooled (without air cooling), the temperature of the outer surface of the furnace bottom can be 240 ℃, after the furnace is operated for a certain number of times, the furnace is also repaired in a hot state, the condition is good, and the electric furnace is in a normal operation state.

Example two:

for a 120t direct current electric arc furnace, after a metal anode steel sheet 8 (distributed similarly to a spider web) is installed, a heat insulation bulk material with the thickness of 120mm is rammed to be used as a heat insulation material 10, and then a dry magnesium-calcium ramming material 6 with the thickness of 500mm is rammed. It is worth noting that for densification, each charge must not exceed a thickness of 100mm, and is rammed using special vibrating ramming equipment. And then adding a conductive refractory material 7 (specifically a magnesium-carbon conductive ramming material) for construction, wherein the superposition thickness of the magnesium-carbon conductive ramming material and the steel sheet is 300mm, and the magnesium-carbon ramming material is rammed above the steel sheet by 180 mm. The construction method of the ramming is the same as that of the dry-type magnesium-calcium ramming material. Must be compacted. This is important not only for corrosion resistance but also for electrical conductivity. Then, a magnesia-carbon brick lining 4 is built, and the periphery and the slope of the electric furnace are rammed by using a dry magnesia-calcia ramming material. Thus, the steel can be made by adding steel-making raw materials and supplying power. Under the condition that the bottom electrode copper plate is naturally cooled, the temperature of the outer surface of the bottom of the furnace can be 215 ℃, and the temperature of the surface of the side wall can be below 250 ℃, so that the electric furnace can normally run.

Table 1: the results produced by the examples are shown in the following table

The comparative examples 1 and 2 are common direct current electric arc furnaces, respectively, a steel needle and a steel sheet are used as bottom electrodes, an upper conductive refractory material and a bottom heat-insulating material are not provided, hot repair and cold repair cannot be performed, the electrodes need to be replaced by blowing out, heat insulation is not provided at the bottom, the temperature of the bottom is too high, a large amount of heat loss is caused, air cooling is needed at the bottom, a large amount of electric quantity is consumed, the heat-insulating material is used in the examples 1 and 2, the temperature of the bottom is obviously reduced, and therefore the electric quantity required for cooling is obviously reduced.

Metal electrode8 and the conductive refractory 7 ² ) The current intensity (KA) is not less than 0.054 multiplied by the voltage, so that the bottom electrode can be effectively prevented from heating, and the safe operation can be realized. The conductive refractory material 7 is a magnesium (calcium) carbon ramming mass, and the performances after carbonization are as follows: resistivity is less than or equal to 9 multiplied by 10 ^-4 Omega.m, volume density not less than 2.8g/cm ³ The compressive strength is more than or equal to 20MPa, and the MgO + CaO + C is more than or equal to 85 percent, and the cold ramming agent is mainly used for cold ramming construction to prolong the service life of the bottom electrode. The conductive repairing material 3 is a magnesium (calcium) carbon hot repairing material and is characterized in that the performance after carbonization is as follows: resistivity is less than or equal to 4 multiplied by 10 ^-3 Omega.m, volume density not less than 2.2g/cm ³ The compressive strength is more than or equal to 12MPa, and the MgO + CaO + C is more than or equal to 85 percent, and the material is mainly used for hot-state feeding and repairing, can be thermally self-leveled when being fed in a steel-making hot state, fills the pits and recesses seriously eroded, lengthens the bottom electrode in the hot state, and prolongs the service life of the bottom electrode under the condition of non-stop production.

The utility model provides a direct current electric arc furnace stove bottom electrode's structure is with electrically conductive bottom electrode ramming mass 11 and the electrically conductive refractory material 7 of resistant erosion (be fine and close magnesium calcium matter dry-type material) filling the clearance between electrically conductive steel needle or the steel sheet to ramming densify, play thermal-insulated and resistant erosion's effect, protected positive pole steel sheet and steel needle simultaneously, this bed of material thickness is decided by the power supply strength, generally for 40~60% of whole stove bottom thickness. And then the gap between the upper furnace bottom and the steel sheet or the steel needle is filled and beaten by conductive magnesium (calcium) carbon ramming mass. The lower part of the bottom electrode is conducted by a steel needle or a steel sheet, the middle part of the bottom electrode is conducted by a mixed type of the conductive magnesia carbon ramming material and the steel needle or the steel sheet, and the conductive magnesia carbon ramming material and the metal steel sheet or the steel sheet are compactly combined because of the bulk plastic ramming material, so that the interface resistance is very low. The magnesia carbon ramming mass is arranged on the upper part for conducting electricity. The bottom electrode of the direct current electric arc furnace can be subjected to cold repair by using the conductive refractory material 7, and can also be subjected to hot repair by using the conductive repair material 3 at any time, so that the service life of the bottom electrode is controllable like an alternating current electric furnace, and the furnace shutdown and the equipment operation rate are not influenced by the bottom electrode. Meanwhile, the unit consumption of refractory materials can be reduced, and the method has important significance for reducing cost and improving safety. Particularly, the bottom electrode is introduced with a high-quality heat-insulating material, so that air cooling or water cooling equipment is omitted, and a good energy-saving effect is brought.

The specific operation method is that in the hot operation process, namely in the production process, when the temperature of the furnace bottom is overhigh under the conditions of fast corrosion of the bottom anode and the like, the molten steel can be discharged completely, after the steel slag on the upper surface of the bottom anode is swept and cleaned by an oxygen gun, the hot repairing material is thrown onto the bottom anode, and the hot repairing material can automatically level and carbonize under the hot condition and is firmly combined with the original residual bottom anode. The process is only 20-50 min. Then the charging and steelmaking can be carried out. Therefore, the hot patching can be carried out by using the conductive hot patching material at any time according to specific conditions;

when the furnace such as a steel tapping hole, a slag changing line and the like is cooled down, the bottom anode can be simultaneously cold repaired. After the furnace is cooled down, the steel slag on the surface of the bottom anode is cleaned, and is tamped by using a conductive magnesia carbon ramming material to reach the original thickness so as to maintain the length of the bottom anode and the temperature of the furnace bottom at a safe operation level.

The conductive refractory material is adopted, so that the metal type bottom anode is changed into a composite bottom anode combining metal and the conductive refractory material. Therefore, the irreparable metal bottom anode is changed into the bottom anode which can be repaired in a cold state and a hot state, and the service life of the bottom anode is greatly prolonged. Thus, the operation rate of the electric furnace steel making is improved, the steel making cost is reduced and the utilization rate of equipment is improved. Through the design of heat preservation of the bottom anode, air cooling and water cooling equipment can be omitted, and the temperature of the furnace shell and the heat dissipation capacity are obviously reduced. Has good effects on energy conservation, environmental protection, cost reduction and efficiency improvement.

In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The description is thus to be regarded as illustrative instead of limiting.

Claims (7)

1. The utility model provides a direct current electric arc furnace bottom electrode structure, characterized in that, bottom electrode structure be compound bottom anode structure, bottom electrode structure include that the vertical interval of several installs in the metal conductive element (8) of stove bottom, metal conductive element (8) between the whole refractory material that is filled of interval, the bottom of interval is filled by thermal-insulated insulation material (10), and the middle part is filled with bottom electrode ramming mass (11), the upper portion of interval is filled by electrically conductive refractory material (7).

2. A dc arc furnace bottom electrode structure as claimed in claim 1, wherein said metallic conductive member (8) is a steel sheet or a steel needle and a combination thereof, and the height of said metallic conductive member (8) is greater than 2/3 of the thickness of said furnace bottom.

3. The bottom electrode structure of a DC arc furnace according to claim 1, wherein the overall height of the space filled with said thermal insulation material (10) is not more than 150mm and not more than 25% of the thickness of said furnace bottom.

4. The structure of the bottom electrode of the direct current arc furnace according to claim 1, characterized in that the bottom electrode ramming mass (11) is a dry type alkaline refractory ramming mass, and the thickness of the bottom electrode ramming mass is more than or equal to 40-60% of the thickness of the bottom electrode.

5. A DC arc furnace bottom electrode structure according to claim 1, characterized in that the contact area (m) between said conductive refractory material (7) and said metallic conductive element (8) ² ) The current intensity (KA) is not less than 0.054 multiplied.

6. A dc arc furnace bottom electrode structure according to claim 3, characterized in that said thermal insulation material (10) has the following performance parameters: the resistivity is more than or equal to 5 multiplied by 104 omega, the heat conductivity coefficient is less than or equal to 0.3w/(mk), and the refractoriness is more than or equal to 1790 ℃.

7. A DC arc furnace bottom electrode structure according to any of claims 1-6, characterized in that the top of the metal conductive element is further laid with conductive repair material (3).

Images