Graphitization furnace

Abstract

The present disclosure provides a graphitization furnace belonging to the technical field of graphitization furnaces. The graphitization furnace includes a furnace body, an upper lining, an insulating lining, a lower lining, a positive electrode, and a negative electrode. The upper lining, the insulating lining, and the lower lining are attached to the inner wall of the furnace body. The upper lining, the insulating lining, and the lower lining are sequentially installed in contact with each other along a top-to-bottom direction. In addition, the upper lining, the insulating lining, and the lower lining are all installed with a first through hole that is essentially coaxial. The positive electrode is installed essentially vertically. The lower end of the positive electrode is installed on the upper lining. The negative electrode is installed essentially horizontally. The negative electrode is installed at its center with a second through hole for passing raw materials. The second through hole and the first through hole of the negative electrode are installed essentially coaxially. The negative electrode is installed at its center inside the lower lining.

Description

[Technical Field]

[0001] This disclosure claims priority based on a Chinese patent application filed on March 11, 2022, bearing application number 202210241349.9, for an invention entitled "Graphitization Furnace," the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to the technical field of graphitization furnaces, and more particularly to graphitization furnaces. [Background technology]

[0003] A graphitization furnace is a device that processes non-graphitic carbon materials, which have a structure in which hexagonal carbon atoms are deposited in a planar network of layers, at temperatures above 2000°C, thereby changing the physical conditions and transforming the non-graphitic carbon material into a graphitic carbon material, in which the graphite has a regular three-dimensional structure. Currently, graphitization technology both in China and abroad requires the use of electrical heating technology to achieve the regular three-dimensional structure of the graphite. Heating using electrical resistance is commonly used. Heating furnaces that use electrical resistance include the Acheson graphitization furnace, internal parallel graphitization furnace, and vertical graphitization furnace.

[0004] A vertical graphitization furnace has a positive electrode located at the top of the furnace body and a negative electrode located at the bottom of the furnace body. During current flow, a high-temperature region is formed between the positive and negative electrodes, causing the particulate raw material located between the positive and negative electrodes to reach a high temperature, which is maintained for a certain period of time. This results in graphitization of the raw material. While such graphitization furnaces are highly efficient in using thermal energy, have significant energy savings, and produce high-purity products, they are prone to short circuits between the positive and negative electrodes, posing a significant safety risk. Summary of the Invention [Problem to be solved by the invention]

[0005] In order to solve the above technical problems, a graphitization furnace is provided in which the graphitization process is stable and the safety risk of short-circuiting between the positive and negative electrodes is eliminated. [Means for solving the problem]

[0006] The present disclosure provides a graphitization furnace comprising: a furnace body; an upper lining, an insulating lining, and a lower lining, wherein the upper lining, the insulating lining, and the lower lining are all attached to the inner wall of the furnace body and are installed in that order from top to bottom, and the upper lining, the insulating lining, and the lower lining are all ring-shaped; and a positive electrode and a negative electrode, wherein the positive electrode is installed vertically, the lower end of the positive electrode is installed on the upper lining, and the negative electrode is installed horizontally, and a through-hole is formed in the center of the negative electrode for allowing raw materials to pass through, and the negative electrode is installed inside the lower lining. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a graphitization furnace configuration according to some embodiments of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing the upper lining in FIG. 1 in an expanded configuration. [Figure 3] FIG. 3 is a diagram illustrating the principle of erosion of the upper lining in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0008] In order to make those skilled in the art understand the present application in more detail, the technical solutions of the present application will be described in detail below based on specific embodiments with reference to the drawings.

[0009] 1 is a schematic diagram showing the configuration of a graphitization furnace according to some embodiments of the present disclosure. Referring to FIG. 1, the graphitization furnace according to the embodiments of the present disclosure includes a furnace body 1, an upper lining 2, an insulating lining 3, a lower lining 4, a positive electrode 5, and a negative electrode 6.

[0010] In some embodiments, the upper lining 2, the insulating lining 3, and the lower lining 4 may be attached to the inner wall of the furnace body 1. The upper lining 2, the insulating lining 3, and the lower lining 4 are installed in abutting contact with each other in a top-to-bottom order. The upper lining 2, the insulating lining 3, and the lower lining 4 each have a first through-hole that is coaxial with the first lining. The positive electrode 5 is installed essentially vertically. The lower end of the positive electrode 5 is installed on the upper lining 2. The negative electrode 6 is installed essentially horizontally. The negative electrode 6 has a second through-hole in its center for allowing raw materials to pass through. The second through-hole and the first through-hole are installed essentially coaxially. The negative electrode 6 is installed on the lower lining 4. In some embodiments, the center of the negative electrode 6 is installed inside the lower lining 4. Both ends of the negative electrode 6 may be inserted into or pass through the side walls of the lower lining 4.

[0011] In graphitization furnaces known to the applicant, raw materials are graphitized at high temperatures using heat generated by current flow between the positive electrode 5, raw materials, and negative electrode 6. The lining of the graphitization furnace is made of a carbon material to enhance corrosion resistance. During the high-temperature treatment, the lining also graphitizes. This makes the lining a conductor, forming a path between the positive electrode 5, lining, and negative electrode 6. However, since the raw materials have high electrical resistance, current does not flow through them, forming a short circuit between the positive electrode 5 and negative electrode 6, causing a safety hazard and adversely affecting the production of graphitized raw materials. In some embodiments of the present disclosure, an insulating lining 3 may be installed between the upper lining 2 and the lower lining 4. Even when the upper lining 2 and the lower lining 4 are graphitized during the high-temperature treatment, the installation of the insulating lining 3 prevents a gap between the upper lining 2 and the lower lining 4. disconnection This allows current to flow smoothly between the positive electrode 5, raw material, and negative electrode 6, promoting the graphitization process, saving electrical energy and ensuring a stable graphitization process. Possible embodiments of the present disclosure eliminate the risk of explosion or safety issues caused by a short circuit between the positive electrode 5 and negative electrode 6. The direction of current flow can be effectively controlled, concentrating energy and forming an artificial electric field, improving the temperature in the graphitization furnace and product quality.

[0012] In some embodiments, the thickness of the insulating lining 3 may be 30 to 200 mm to ensure the strength of the insulating lining 3. If the insulating lining 3 is too thin, it is susceptible to erosion, abrasion, or oxidation, and may even fail to provide insulation. On the other hand, if the insulating lining 3 is too thick, its high-temperature resistance deteriorates, it is susceptible to softening, its strength is low, and the furnace may collapse.

[0013] In some embodiments, the insulating lining 3 is made of a refractory material poured in. The refractory material is at least one of alumina bricks, zirconia bricks, corundum bricks, and clay bricks. These refractory materials mainly contain aluminum oxide, zirconia, etc., and have good insulating properties and a certain degree of corrosion resistance. Since the insulating lining 3 is located near the bottom, corrosive gases gather at the top, so corrosion is not significant there.

[0014] Referring to FIG. 1, in some embodiments, the lower end of the upper lining 2 is connected to the upper end surface of the insulating lining 3 , and the upper end of the lower lining 4 is connected to the lower end surface of the insulating lining 3 .

[0015] In some embodiments, the upper lining 2, the insulating lining 3 and the lower lining 4 all have the same inner diameter, so that the exhaust gases generated in the firebox can be sucked out.

[0016] In some embodiments, the graphitization furnace may include at least two support rods 7. One end of each support rod 7 is provided outside the graphitization furnace, and the other end is provided inside the graphitization furnace and connected to the anode 6. Only two support rods 7 may be provided, or multiple support rods 7 may be provided. Multiple support rods 7 may be provided radially around the central axis of the graphitization furnace. The support rods 7 are made of refractory material to support the anode 6.

[0017] In another embodiment, each support rod 7 has a groove formed at the other end, and the outer periphery of the negative electrode 6 is inserted into the groove of each support rod 7 .

[0018] In some embodiments, referring to FIGS. 2 and 3 , the upper lining 2 may include multiple refractory layers. The upper lining 2 may include multiple refractory layers arranged in a reticulated pattern on its inner surface. The refractory layers located around the same circumference may include multiple first refractory bricks 201 and second refractory bricks 202 spaced apart. The refractory layers located on the same generatrix may include multiple first refractory bricks 201 and second refractory bricks 202 spaced apart. The upper lining 2 includes at least one refractory layer along the radial direction. The first refractory brick has a refractoriness under load of 3200°C or higher. The second refractory brick has a higher oxidation temperature than the first refractory brick.

[0019] 2 and 3, the upper lining 2 may include one or more refractory layers that are stacked in order along the radial direction and extend along the circumferential direction and / or generatrix direction. At least one of the one or more refractory layers may include a plurality of first refractory bricks 201 and second refractory bricks 202 that are spaced apart. The upper lining 2 may include at least one refractory layer on the inner surface. The at least one refractory layer on the inner surface of the upper lining 2 may include a plurality of first refractory bricks 201 and second refractory bricks 202 that are spaced apart.

[0020] In some other embodiments, the single or multiple refractory layers stacked and installed along the radial direction of the upper lining 2 may include a first refractory brick 201 and a second refractory brick 202 installed alternately in the radial direction, or a second refractory brick 202 and a first refractory brick 201 installed alternately in the radial direction. The first refractory brick has a softening point under load of 3200°C or more, and the oxidation temperature of the second refractory brick is higher than the oxidation temperature of the first refractory brick.

[0021] In some embodiments, two types of refractory materials are generally used to construct graphitization furnaces. The first type has good corrosion resistance but good oxidation resistance. The second type has good oxidation resistance but poor corrosion resistance and is easily vaporized. When graphitizing raw materials in a graphitization furnace, corrosive hydrogen fluoride gas may be generated, and at the same time, air is also present in the raw carbon. Therefore, the hydrogen fluoride gas chemically reacts with the lining, corroding the lining. Furthermore, oxygen in the air undergoes an oxidation reaction with the lining, resulting in an ablation reaction and the formation of ash. Furthermore, during the graphitization process, the high-temperature region of the graphitization furnace reaches a high temperature of 2400°C, so the easily vaporized lining undergoes a physical vaporization reaction, becoming gas and being sucked out. Therefore, if a lining made of a refractory material with good corrosion resistance but poor oxidation resistance is used, it will be oxidized by the oxygen present in the graphitization process, causing an ablation reaction and the formation of ash, which will result in insufficient lining and adversely affect the service life of the graphitization furnace.If a lining made of a refractory material with good oxidation resistance but poor corrosion resistance and easy vaporization is used, it will be eroded by the corrosive hydrogen fluoride gas generated during the graphitization process, which will adversely affect the service life of the graphitization furnace.

[0022] A second refractory brick 202 with good oxidation resistance is constructed around a first refractory brick 201 with good corrosion resistance. Therefore, when the atmosphere in the high-temperature region of a graphitization furnace mainly contains corrosive hydrogen fluoride gas, an oxidation-abrasion reaction occurs between a small amount of oxygen and the corrosion-resistant first refractory brick 201. A chemical corrosion reaction occurs between the hydrogen fluoride and the surface of the second refractory brick 202 exposed to the fire, forming a depression 203 on the surface of the second refractory brick 202 exposed to the fire. The corrosion-resistant first refractory brick 201 is present on both side walls of the depression 203. Due to the negative pressure and the blocking role of the side walls of the depression 203, a large amount of hydrogen fluoride gas is sucked out of the depression 203, and only a small amount of hydrogen fluoride gas enters the depression 203, causing a chemical corrosion reaction with the second refractory brick 202 located at the bottom of the depression.

[0023] When the atmosphere in the high-temperature region of the graphitization furnace is primarily oxygen-containing, an oxidation-ablation reaction occurs between the first refractory brick 201 and the oxygen, forming a depression 203. Similarly, the depression 203 has second refractory bricks 202, which have oxidation-resistant properties, on all four side walls. Due to the negative pressure and the blocking role of the side walls of the depression 203, a large amount of oxygen is sucked out of the depression 203, and only a small amount of oxygen enters the depression 203, causing an oxidation-ablation reaction with the first refractory brick 201 located at the bottom of the depression, and also causing a high-temperature vaporization reaction. A small amount of hydrogen fluoride gas reacts with the second refractory brick 202 in a chemical corrosion reaction.

[0024] In other words, the first refractory bricks 201 placed around the second refractory bricks 202 can slow down the chemical corrosion rate of the second refractory bricks 202 placed in the center. The second refractory bricks 202 placed around the first refractory bricks 201 can slow down the oxidation and abrasion rate of the first refractory bricks 201 placed in the center. This can slow down the rate at which the lining is thinned, and extend the service life of the lining located in the high temperature region.

[0025] The first refractory brick 201 and the second refractory brick 202 may be considered as a single brick, or as a single brick constructed from multiple refractory bricks. The sizes of the first refractory brick 201 and the second refractory brick 202 may be freely selected depending on the size to be processed. For example, the first refractory brick 201 may be 50×50×20 mm in size, and the surface corresponding to the 50×20 mm size is the surface exposed to fire. If the processing size of the refractory brick is 50×50×10 mm, two refractory bricks may be gathered into the first refractory brick 201 having a size of 50×50×20 mm. Since the second refractory brick 202 is the same, its description will not be repeated here.

[0026] The first refractory brick 201 has abrasion resistance and a softening point under load of 3200°C or higher.

[0027] Since the oxidation temperature of the second refractory bricks 202 is higher than that of the first refractory bricks 201, the second refractory bricks 202 have better oxidation resistance than the first refractory bricks 201.

[0028] In some embodiments, the size of the surface exposed to fire of both the first refractory brick 201 and the second refractory brick 202 may be 100 to 500 x 100 to 500 mm.

[0029] The fire-exposed surface refers to the surface of the refractory brick that comes into contact with the atmosphere in the graphitization furnace. When the size of the fire-exposed surface of the first refractory brick 201 is relatively large, the depressions 203 corroded by oxidation also become relatively large. In the furnace, oxygen in the primarily oxidizing atmosphere is likely to come into contact with the fire-exposed surface of the depressions 203, reducing the effect of delaying oxidation. On the other hand, when the size of the fire-exposed surface of the first refractory brick 201 is too small, the time required for building is extended. Similarly, when the fire-exposed surface of the second refractory brick 202 is relatively large, the depressions 203 formed through a chemical corrosion reaction with hydrogen fluoride are relatively large, reducing the effect of delaying corrosion. Furthermore, when the fire-exposed surface of the second refractory brick 202 is too small, the time required for building is extended. In some embodiments, the size of the fire-exposed surface of the first refractory brick 201 may be similar to the size of the fire-exposed surface of the second refractory brick 202, thereby ensuring that the size of the brick gap between the first refractory brick 201 and the second refractory brick 202 is the same.

[0030] In some embodiments, the lining located in the high temperature zone may have a thickness of 50 to 500 mm. If the lining located in the high temperature zone is too thick, costs will increase. If the lining located in the high temperature zone is too thin, the graphitization furnace will have a shorter service life and will require more frequent rebuilds. The thickness of the lining located in the high temperature zone is actually the distance between the surfaces of the first refractory brick 201 and the second refractory brick 202 that are exposed to the fire and the surfaces of the first refractory brick 201 and the second refractory brick 202 that are opposite to the surfaces that are exposed to the fire.

[0031] In some embodiments, the first refractory brick 201 may include, but is not limited to, at least one of a blast furnace carbon brick, a graphite carbon brick, and a microporous composite carbon brick. Both the blast furnace carbon brick and the microporous composite carbon brick have uniform and excellent abrasion resistance, and their softening points under load are determined through a softening point test. The softening point under load, also known as the deformation temperature, is the temperature at which a refractory brick begins to deform under a constant pressure load with an increasing temperature. The softening point under load indicates the resistance capacity of a refractory brick when subjected to both high temperature and load, and indicates the structural strength of the refractory brick under the same operating conditions. The softening point under load also indicates the temperature at which a refractory brick begins to deform under a constant pressure load, at which point softening and obvious plastic deformation occur in the refractory brick. The higher the softening point under load, the better the abrasion resistance of the refractory brick.

[0032] Carbon bricks for blast furnaces are produced as follows: Electrically fired high-temperature anthracite is used as the main raw material, and additives are added to the main raw material, and asphalt is used as an adhesive. Once molded, the bricks are fired at high temperatures and then finished. Carbon bricks for blast furnaces have an ash content of less than 8%, compressive strength of more than 29.6 MPa, total porosity of less than 23%, and volume density of more than 1.5 g / cm. 3 , thermal conductivity >5.0w / (m·K) 3 The microporous composite carbon brick may adopt high strength graphite as disclosed in Chinese patent having disclosure number CN104477902A.

[0033] In some embodiments, the second refractory brick 202 may be at least one of, but is not limited to, an alumina brick, a mullite brick, a silicon brick, a corundum brick, a zirconia brick, and a silicon carbide brick.

[0034] The oxidation temperature of the second refractory brick refers to the temperature at which oxidation begins in an oxygen atmosphere. Generally, carbon-containing refractory bricks, such as the silicon carbide bricks mentioned above, are susceptible to oxidation. On the other hand, alumina bricks, mullite bricks, silicon bricks, corundum bricks, and zirconia bricks do not contain carbon and therefore are not susceptible to oxidation during use. Therefore, the oxidation temperatures of alumina bricks, mullite bricks, silicon bricks, corundum bricks, and zirconia bricks may be considered infinite.

[0035] Alumina bricks have a mass fraction of Al2O3 in the main components higher than 90%, and are made from bauxite or other raw materials with a relatively high aluminum oxide content through molding and firing. They have a refractoriness of over 1770°C and high thermal stability.

[0036] Mullite bricks are produced from high-aluminum refractory materials with mullite as the main crystalline phase and an aluminum oxide content of 65-75%, and bauxite clinker with a high aluminum content, which is then molded and fired. Mullite bricks have a high refractoriness of over 1790°C, a softening temperature under load of 1600-1700°C, and a compressive strength of 70-260 MPa at room temperature. They also have good thermal shock resistance. There are two types of mullite bricks: fired mullite bricks and electrofused mullite bricks.

[0037] Silicon bricks, as an acidic refractory material, have excellent resistance to corrosion by acidic clinker. Their softening point under load is high, at 1640-1670°C, and their volume remains relatively stable even when used at high temperatures for long periods of time. Silicon bricks contain 94% or more silicon oxide, and their softening point under load is 1620-1670°C. Silicon bricks do not deform even when used at high temperatures for long periods of time. Silicon bricks are made from natural silicon ore, and are slowly fired at 1350-1430°C in a reducing atmosphere with the addition of appropriate mineralizers. When heated to 1450°C, silicon bricks expand by 1.5-2.2% in volume. This expansion allows the gaps between silicon bricks to close, providing structures with good airtightness and structural strength.

[0038] Corundum bricks are refractory products with an aluminum oxide content greater than 90% and a crystalline phase primarily consisting of corundum. Corundum bricks have a compressive strength of over 340 MPa at room temperature, a softening point under load greater than 1700°C, excellent chemical stability, and good oxidation resistance. Zirconia bricks are heat-insulating refractory products made primarily from hollow zirconia spheres. Zirconia bricks are cubic zirconia, with 70% to 80% of the mineral phase being primarily crystalline, and have a refractoriness greater than 2400°C, a porosity of 55 to 60%, and a thermal conductivity of 0.23 to 0.35 w / (m·K).

[0039] Silicon carbide bricks are refractory materials made primarily from SiC, making them relatively stable against acidic clinker. The SiC content in silicon carbide bricks is 72-99%. Depending on the binder phase, silicon carbide bricks can be divided into clay-bonded, Si3N4-bonded, Sialon-bonded, β-SiC-bonded, Si2ON2-bonded, and recrystallized SiC products, all of which have relatively good oxidation resistance.

[0040] The graphitization furnace provided by the embodiments of the present disclosure has at least the following advantages: 1. The graphitization furnace is equipped with an insulating lining between the positive and negative electrodes. This insulating lining can effectively control the direction of current flow, concentrate energy, and help form an artificial electric field, thereby improving the temperature of the graphitization furnace and the quality of the product. Moreover, it can effectively prevent safety accidents caused by short circuits between the positive and negative electrodes during operation. 2. The upper lining, which is constructed of corrosion-resistant first refractory bricks and antioxidant second refractory bricks and has a staggered mesh pattern, can effectively delay the corrosion of the lining by the atmosphere inside the furnace, thereby reducing the frequency of rebuilding the lining located in the high-temperature area of ​​the graphitization furnace and extending the service life of the graphitization furnace lining.

[0041] Although preferred embodiments of the present application have been described, other variations and modifications of these embodiments will be apparent to those skilled in the art once they have grasped the basic inventive concept. Therefore, the appended claims should be interpreted to include the preferred embodiments and any variations or modifications that fall within the scope of the present application.

[0042] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application, and the present application intends to include such modifications and variations as long as they fall within the scope of the claims of the present application and their equivalents. [Explanation of symbols]

[0043] 1 Furnace body 2 Upper lining 201 First refractory brick 202 Secondary refractory brick 203 Depression 3. Insulating lining 4 Lower Lining 5 Positive electrode 6 negative electrode 7 Support rod

Claims

1. A furnace body, an upper lining, an insulating lining, and a lower lining, all of which are attached to the inner wall of the furnace body, are installed in contact with each other in a top-to-bottom direction, and have a first through hole formed coaxially therein; a positive electrode and a negative electrode, wherein the positive electrode is installed vertically, a lower end of the positive electrode is installed in the upper lining, the negative electrode is installed horizontally, a second through-hole is formed in the center of the negative electrode for allowing raw materials to pass through, the second through-hole and the first through-hole of the negative electrode are installed coaxially, and the negative electrode is installed inside the lower lining.

2. 2. The graphitization furnace according to claim 1, wherein the insulating lining has a thickness in the vertical direction of 30 to 200 mm.

3. the insulating lining is poured with refractory material; 2. The graphitization furnace according to claim 1, wherein the refractory material is any one of an alumina brick, a zirconia brick, a corundum brick, and a clay brick.

4. 2. The graphitization furnace according to claim 1, wherein the upper lining, the insulating lining, and the lower lining have the same inner diameter.

5. further comprising at least two support rods; 2. The graphitization furnace according to claim 1, wherein each of the support rods has one end provided outside the graphitization furnace and the other end provided inside the graphitization furnace and connected to the negative electrode.

6. 6. The graphitization furnace according to claim 5, wherein each of the support rods has a groove formed at the other end thereof, and the outer periphery of the negative electrode is inserted into the groove of each of the support rods.

7. the upper lining includes one or more refractory layers disposed on the inner surface in a radial direction in succession and extending in a circumferential direction and / or a generatrix direction; At least one refractory layer of the one or multiple refractory layers includes a plurality of first refractory bricks and second refractory bricks arranged alternately; 7. The graphitization furnace according to claim 1, wherein the first refractory brick has a softening point under load of 3200°C or higher, and the second refractory brick has an oxidation temperature higher than the oxidation temperature of the first refractory brick.

8. 8. The graphitization furnace according to claim 7, wherein the first refractory brick and the second refractory brick each have a surface exposed to fire of 100 to 500 mm x 100 to 500 mm.

9. 8. The graphitization furnace according to claim 7, wherein the first refractory brick is at least one of a blast furnace carbon brick, a graphite carbon brick, and a microporous composite carbon brick.

10. 8. The graphitization furnace according to claim 7, wherein the second refractory brick is at least one of an alumina brick, a mullite brick, a silicon brick, a corundum brick, a zirconia brick, and a silicon carbide brick.

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