A method for reducing current surge during electrocalcination of graphitized cathodes

Abstract

This invention belongs to the field of electrocalcination technology, and specifically relates to a method for reducing current surge during electrocalcination of graphitized cathodes. The method includes the following steps: S1, laying and leveling the furnace bottom with filler coke; S2, laying insulating material on top of the filler material; S3, placing the calcined product flat on top of the insulating material and loading it into the furnace; S4, uniformly wrapping the calcined product and the surrounding area of ​​the adjusting block with insulating material; S5, inserting a flexible graphite pad into the gap between the adjusting block and the calcined product; S6, wrapping a layer of insulating material around the junction of the adjusting block, the flexible graphite pad, and the calcined product; S7, inserting insulating plates around the calcined product in three sections along its length; S8, energizing the graphitized product, and removing the insulating plates after energizing. This method does not affect the energization of the graphitization furnace, and effectively increases the furnace resistance by 1-2 mΩ, significantly reducing the instantaneous current surge during energization, which can be controlled to within 1000A.

Description

Technical Field

[0001] This invention belongs to the field of electrocalcination technology, and in particular relates to a method for reducing current surges during electrocalcination of graphitized cathodes. Background Technology

[0002] In the field of graphitized cathode electrocalcination, the primary side voltage is very high, often between 10KV and 35KV or even higher, while the secondary low-voltage side DC furnace resistance is very small, between 3-6mΩ or even lower. At the moment of power supply to the graphitization furnace, the primary side current is very high, sometimes even reaching 4000-8000A. This causes the reactive power of the power supply and distribution system to exceed the system safety value at the moment of power supply, and may even cause electrical accidents such as partial tripping of the power supply and distribution system and damage to rectifier transformers.

[0003] Currently, many graphitization manufacturers use transformers and frequency converters to adjust or change the capacity of capacitors and reactors in the power system to regulate voltage and current, which can improve the stability of the power system. However, in recent years, due to the increasing size of graphitization furnaces and the continuous increase in furnace loading, the cross-sectional area of ​​the products inside the furnace has increased, while the DC resistance on the secondary low-voltage side is lower than before, even less than 1mΩ. In addition, the capacity of the supporting rectifier transformers has also increased significantly. After the initial DC voltage on the secondary low-voltage side increases, under these circumstances, the excitation current generated by the power supply and distribution system at the moment of power supply to the graphitization furnace often exceeds the safety value set by the power distribution system. This not only causes the graphitization furnace to fail to be powered on, affecting the normal operation of the production system, but also poses potential system safety hazards. Under these circumstances, how to reduce the impact of the electrocalcining current of the graphitization cathode, ensure the normal power supply to the graphitization furnace, and maintain the stability of the power supply and distribution system has always been a research and development issue for graphitization electrocalcining enterprises. Summary of the Invention

[0004] To address the technical problems existing in the background art, the present invention provides a method for reducing current surges by electrocalcining a graphitized cathode.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for reducing current surges by electrocalcining a graphitized cathode includes the following steps: S1, use filler coke to lay the bottom material of the furnace and rake it flat; S2, Lay the insulating material on top of the base material; S3, Place the baked product flat on top of the insulating material and load it into the furnace; S4, wrap the baking product and the adjustment block evenly with insulating material; S5, Insert a flexible graphite pad into the gap between the adjusting block and the baked product; S6, wrap an insulating material around the junction of the adjusting block, the flexible graphite pad and the baked product to prevent coke from entering the gap; S7, the insulating plate is inserted around the roasted product in three sections along the length of the product, thereby dividing the furnace into multiple filling spaces; S8 supplies power to the graphitized product. After the power supply operation is completed, the insulating plate is pulled out immediately.

[0006] Furthermore, several calcined products and adjustment blocks constitute the furnace charge; after step S7, the furnace charge and the furnace head and tail electrodes are covered with filler material, and then the graphitized products are powered.

[0007] Furthermore, the filler material in the middle section of the furnace is mature coke with a resistivity ≥400uΩm; the filler material at both ends and at the furnace head and tail electrodes is raw coke or mixed coke.

[0008] Furthermore, several roasted products and adjusting blocks constitute the furnace material; after step S7, filler material is stacked at fixed intervals on the upper side of the furnace material, the filler material on the furnace material is coke with resistivity ≥400uΩm, then the graphitized products are powered, and after the power is supplied, the filler material is raked flat to completely cover the furnace material.

[0009] Furthermore, in step S8, after the insulating board is pulled out, the filling material is replenished according to the filling requirements.

[0010] Furthermore, the insulating material is kraft paper with a thickness of 0.5 mm, and its length and width vary according to the size of the baked product.

[0011] Furthermore, the insulation board is made of 20mm thick multi-layer wood core board, and its length and width vary according to the size of the baked product.

[0012] Furthermore, after power is supplied, fresh filler coke with high resistance should be used to fill the furnace head and tail in a timely manner.

[0013] The present invention has the following advantages and beneficial effects: In this invention, during the graphitization process, the cathode-baked product is wrapped with insulating material (kraft paper) to isolate it from the filler coke. At the furnace head and tail, the adjusting block is also isolated from the baked product using insulating material (kraft paper). Insulating material (insulating plates) is inserted around the product in three sections along its length. These measures reduce the conductive contact area between the baked product and the filler material inside the furnace, increasing furnace resistance. After power is supplied and the baked product temperature rises, the insulating material (insulating plates) is removed, and the high temperature burns off the insulating material (kraft paper) covering the baked product, without affecting subsequent normal power supply. This method can reduce the large current impact on the power supply system caused by the simultaneous electrification of the baked product and metallurgical coke during power supply. By insulating and wrapping the char blocks, controlling the resistivity of the filler coke, and processing them in sections, the furnace resistance is significantly improved and the impact current is reduced. The furnace resistance is effectively increased by 1-2 mΩ, and the impact current is significantly reduced during power supply. This achieves the effect of reducing the impact current and controlling the impact current to <1000A. Attached Figure Description

[0014] Figure 1 Side view of the effect of kraft paper wrapping on the graphitization furnace provided by the present invention. Figure 1 ; Figure 2 Side view of the effect of kraft paper wrapping on the graphitization furnace provided by the present invention. Figure 2 ; Figure 3 This is a top view of the calcined product, the adjusting block, and the flexible graphite pad, which are wrapped with insulating material according to the present invention. Figure 4 Side view of the graphitized filler coke and insulating plate effect provided by the present invention. Figure 1 ; Figure 5 Side view of the graphitized filler coke and insulating plate effect provided by the present invention. Figure 2 ; Figure 6 A top view of the graphitization furnace loading provided by the present invention; Figure 7 for Figure 6 Top view of the furnace after loading, inserting the insulating plate, and filling with coke; Figure 8 for Figure 7 A top view showing the coke filling completely covering the roasted products and adjustment blocks after the furnace is loaded into the middle section; Figure 9 for Figure 5 Top view; Icons: 1-furnace head electrode, 2-bottom material, 2a-cooked coke, 2b-raw coke or mixed coke, 2c-empty material section, 3-insulating material, 4-adjusting block, 5-roasted product, 6-partition, 7-flexible graphite pad, 7a-gap, 8-insulating board. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0016] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. Example 1 like Figures 1-4 , Figure 6-8 As shown, a method for reducing current surges through electrocalcination of a graphitized cathode includes the following steps: S1, use filler coke to lay bottom material 2 on the furnace bottom and rake it flat.

[0017] S2, lay the insulating material 3 on the top of the base material 2.

[0018] S3, place the baked product 5 flat on the top of the insulating material 3 and load it into the furnace. When the baked product 5 is arranged in multiple layers, the upper and lower layers are staggered.

[0019] S4, insulating material 3 is evenly wrapped around the roasted product 5 and the adjusting block 4 respectively, that is, each adjusting block 4 and each roasted product 5 needs to be completely wrapped with insulating material 3; the two at the very end of the furnace are the adjusting blocks 4, which are used to fill the gaps after the charcoal blocks are loaded into the furnace. This arrangement can reduce the conductive contact area between the roasted product 5 and the filler and adjusting block 4 in the furnace, thereby increasing the furnace resistance.

[0020] S5, a flexible graphite pad 7 is inserted at the gap 7a between the adjusting block 4 and the calcined product 5. The flexible graphite pad 7 serves to conduct electricity. Adjacent carbon blocks (calcined products 5 and calcined products 5, adjusting block 4 and calcined product 5) are connected because they need to conduct electricity as conductors. The flexible graphite pad 7 is made of graphite, which ensures conductivity while filling the gaps between the carbon blocks, ensuring complete contact between the carbon blocks and preventing them from burning. However, it is disposable. The insulating material 3 will be burned by the carbon blocks when the temperature rises.

[0021] S6. An insulating material 3 is wrapped around the junction of the adjusting block 4, the flexible graphite pad 7, and the roasted product 5 to prevent coke particles from entering the gap 7a. The insulating material 3 (kraft paper) has two functions at the adjusting block 4, the flexible graphite pad 7, and the roasted product 5: First, the kraft paper placed on the flexible graphite pad 7 between the blocks is to separate the carbon blocks, reduce the contact area, and increase furnace resistance; second, the kraft paper placed on top of the gap is to isolate the filling coke and prevent coke particles from falling into the gap, affecting subsequent power supply and causing safety risks.

[0022] S7, the insulating plate 8 is inserted around the roasted product 5 in three sections along the length of the product 5, thereby dividing the furnace into multiple filling spaces; this is used to distinguish the materials around the roasted product 5 and avoid current deviation; the insulating plate 8 is used to isolate the filling material before power is supplied, and the cross-sectional area of ​​the filling material (metallurgical coke) in the furnace is reduced when power is supplied, thus increasing the furnace resistance.

[0023] S8 supplies power to the graphitized product. After the power supply operation is completed, immediately remove the insulating plate 8.

[0024] The purpose of this method is to wrap the cathode-baked product 5 with insulating material 3 (kraft paper) during the graphitization process to isolate it from the filler coke. At the furnace head and tail, the adjusting block 4 is isolated from the product with insulating material 3 (kraft paper). The product 5 is divided into three sections along its length and is surrounded by insulating plates 8 to reduce the conductive contact area between the product 5 and the filler material in the furnace and increase the furnace resistance. After the product 5 is powered on and its temperature rises, the insulating plates 8 are pulled out and the insulating material 3 (kraft paper) wrapped around the product is burned off without affecting subsequent power supply.

[0025] Furthermore, several roasted products 5 and adjusting blocks 4 constitute the furnace charge; after step S7, the furnace charge and the furnace head and tail electrodes are covered with filler material, and then electricity is supplied to the graphitized products. Filler coke (metallurgical coke) is used to fill both sides of the furnace head electrode 1, and the filling thickness is greater than that of the furnace head electrode 1.

[0026] Furthermore, the filler material in the middle section of the furnace is calcined coke 2a with a resistivity ≥400uΩm; the filler material at both ends and at the furnace head and tail electrodes is raw coke or mixed coke 2b.

[0027] Furthermore, in step S8, after power supply is completed and the insulating plate 8 is pulled out, secondary material replenishment is completed according to the filler requirements.

[0028] Furthermore, the insulating material 3 is kraft paper with a thickness of 0.5 mm, and its length and width vary according to the size of the baked product 5.

[0029] Furthermore, the insulating board 8 is made of 20mm thick multi-layer wood core board, and its length and width vary according to the size of the baked product 5.

[0030] In this invention, one method of wrapping the roasted product 5 and the adjusting block 4 is as follows: Use filler coke to lay the bottom material 2 of the furnace and rake it flat. Cut kraft paper longer than the charcoal blocks by 30cm and place it on the bottom material 2, with a width exceeding the width of the charcoal blocks by at least 10cm. Install the adjusting block 4 and the roasted product 5 on the kraft paper according to the furnace loading requirements, corresponding to the cross-sectional area of ​​the roasted product 5. Insert kraft paper between the adjusting block 4 and the roasted product 5 to separate them. Load the subsequent roasted products 5 into the furnace according to the loading requirements, also laying kraft paper at the bottom. It is not necessary to insert kraft paper between roasted products 5, or depending on the furnace situation, some charcoal blocks can be separated by inserting kraft paper. The charcoal blocks at the furnace tail and the adjusting block 4 are handled in the same way as at the furnace head. After the bottom roasted product 5 is installed, cut kraft paper longer than the height + width + height dimensions of the roasted product 5 by 20cm and wrap the charcoal blocks perpendicular to the roasted product 5. The degree of wrapping for the top roasted product 5 is determined according to the situation.

[0031] Example 2 In this embodiment, the content of steps S1-S8 is the same as in the previous embodiment.

[0032] Furthermore, we will make optimizations to the design.

[0033] like Figure 5 , Figure 9 As shown, further, several roasted products 5 and adjusting blocks 4 constitute the furnace charge; after step S7, filler material is stacked at fixed intervals on the upper side of the furnace charge, the filler material on the furnace charge is coke 2a with resistivity ≥400uΩm, and there is an empty material section 2c between two adjacent coke 2a. Then, the graphitized products are powered on, and after the power is supplied, the filler material is raked flat to completely cover the furnace charge.

[0034] Furthermore, after power is supplied, fresh filler coke with high resistance should be used to fill the furnace head and tail in a timely manner to increase the resistance of the filler coke around the conductive electrodes. The resistivity of the filler coke in other positions should be controlled to be no less than 400 uΩm to avoid the filler coke from conducting electricity and causing current shunting.

[0035] The difference between Example 1 and Example 2 is: In Example 1, coke is first placed on top of the furnace charge (raw coke or mixed coke 2b on both sides, and cooked coke 2a in the middle), and then electricity is applied. In Example 2, electricity is applied first, and then the charge on top of the furnace charge is raked and covered. The operation sequences are reversed in both cases.

[0036] The implementation was tracked and recorded during the four-column furnace loading (maximum loading capacity, maximum energized cross-sectional area). The results showed that by insulating and wrapping the roasted product 5, controlling the resistivity of the filler coke, and processing it in sections, there was a significant effect on improving the furnace resistance and reducing the inrush current. It could effectively improve the furnace resistance by 1-2 mΩ, and significantly reduce the inrush current at the moment of power supply, thus achieving the effect of reducing the inrush current and controlling the inrush current to <1000A.

[0037] Please refer to the table below for details:

[0038] In the first case, without insulating paper and insulating board 8, after the roasted product 5 is loaded into the furnace, coke is added, the maximum current exceeds 2000A, and the furnace resistance is 0.78mΩ.

[0039] In the second case, only insulating material 3 is used. After the roasted product 5 is loaded into the furnace, coke is added. The maximum current exceeds 2000A, and the furnace resistance is 1.04mΩ.

[0040] In the third case, only the insulating board 8 is used. After the roasted product 5 is loaded into the furnace, coke is added. The current is less than 2000A, but still exceeds 1000A, and the furnace resistance is 1.26mΩ.

[0041] In the fourth case, when insulating material 3 and insulating board 8 are used, and coke is filled after the roasted product 5 is loaded into the furnace, the maximum current exceeds 1000A and the furnace resistance is 1.42mΩ. The effect is further improved, but it still does not meet the ideal requirements.

[0042] In the fifth case, the difference from the previous four cases is that the first four cases are energized only after the filling material is completed; while the fifth case is the opposite, the energizer is energized first, and the covering material is filled after the energizer is completed. The insulating paper and insulating board 8 are used in the same way, but the filling material is not covered first, and the energizer is energized first. In this method, the current is lower than 1000A, the lowest is 368A, and the furnace resistance is as high as 2.59mΩ.

[0043] In this invention, during the graphitization process, the cathode-baked product 5 is wrapped with insulating material 3 (kraft paper) to separate it from the filler coke. At the furnace head and tail, the adjusting block 4 is isolated from the product using insulating material 3 (kraft paper). The baking product 5 is divided into three sections along its length, and insulating plates 8 are inserted around the product to reduce the conductive contact area between the baking product 5 and the filler material in the furnace, thereby increasing the furnace resistance. After the temperature of the baking product 5 rises after power is supplied, the insulating material 3 (insulating plate 8) is pulled out, and the insulating material 3 (kraft paper) wrapped around the product is burned off without affecting subsequent power supply.

[0044] In this method, insulating material 3 (kraft paper) is used to separate the furnace material (adjusting block 4, roasted product 5) from the filler material (metallurgical coke), thereby reducing the impact of large current on the power supply and distribution system caused by the simultaneous electrification of roasted product 5 and metallurgical coke when power is supplied.

[0045] In this method, the insulating plate 8 is used to isolate the filling material before power is supplied, reduce the cross-sectional area of ​​the furnace to increase the furnace resistance when power is supplied, and pull out the insulating plate 8 or perform secondary material replenishment after power is supplied.

[0046] This method involves filling the furnace head and tail with fresh filler coke with higher resistance immediately after the furnace is loaded and powered on. This increases the resistance of the filler coke around the conductive electrodes. The resistivity of the filler coke in other positions is controlled to be no less than 400 μΩm to avoid the filler coke from conducting electricity and causing current shunting.

[0047] This method will not affect the power supply to the graphitization furnace. In addition, it can effectively increase the furnace resistance by 1-2 mΩ, and significantly reduce the instantaneous current surge during power supply, which can be controlled to within 1000A.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reducing current surge during electrocalcination of a graphitized cathode, characterized in that, Includes the following steps: S1, use filler coke to lay the bottom material of the furnace and rake it flat; S2, Lay the insulating material on top of the base material; S3, Place the baked product flat on top of the insulating material and load it into the furnace; S4, wrap the baking product and the adjustment block evenly with insulating material; S5, Insert a flexible graphite pad into the gap between the adjusting block and the baked product; S6, wrap an insulating material around the junction of the adjusting block, the flexible graphite pad and the baked product to prevent coke from entering the gap; S7, the insulating plate is inserted around the roasted product in three sections along the length of the product, thereby dividing the furnace into multiple filling spaces; S8 supplies power to the graphitized product. After the power supply operation is completed, the insulating plate is removed.

2. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 1, characterized in that: Several calcined products and adjustment blocks constitute the furnace charge; after step S7, the furnace charge and furnace head and tail electrodes are covered with filler material, and then electricity is supplied to the graphitized products.

3. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 2, characterized in that: The filler material in the middle section of the furnace is mature coke with a resistivity ≥400uΩm; the filler material at both ends and at the furnace head and tail electrodes is raw coke or mixed coke.

4. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 1, characterized in that: Several roasted products and adjusting blocks constitute the furnace material; after step S7, filler material is stacked at fixed intervals on the upper side of the furnace material, the filler material on the furnace material is coke with resistivity ≥400uΩm, then the graphitized products are powered, and after the power is supplied, the filler material is raked flat to completely cover the furnace material.

5. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 1, characterized in that: In step S8, after the insulating board is pulled out, the filling material is replenished according to the filling requirements.

6. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 1, characterized in that: The insulating material is kraft paper, 0.5 mm thick, with its length and width varying according to the dimensions of the baked product.

7. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 1, characterized in that: The insulation board is made of 20mm thick multi-layer wood core board, and its length and width vary according to the size of the baked product.

8. The method for reducing current surge by electrocalcining of graphitized cathode according to claim 4, characterized in that: After power is supplied, fresh filler coke with high resistance should be used to fill the furnace head and tail in a timely manner.

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