METHOD FOR PRODUCING GRAPHITE AND VERTICAL GRAPHITATION FURNACE

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The invention relates to a method for producing graphite in a vertical graphitization furnace with at least one process chamber that defines a heating zone, in which a) a temperature of 2,200 °C to 3,200 °C, in particular 2,700 °C to 3,200 °C, preferably 3,000 °C, is generated in the heating zone; b) particulate graphitable material is fed into the process chamber through an access point; c) graphitable material is conveyed through the heating zone of the process chamber, where it is graphitized to graphite; d) the graphite obtained is discharged from the process chamber through an outlet.

[0002] Furthermore, the invention relates to a vertical graphitization furnace with at least one process chamber that defines a heating zone, with a) a heating device by means of which a temperature of 2,200 °C to 3,200 °C, in particular of 3,000 °C, can be generated in the heating zone; b) a feed conveyor by means of which particulate graphitable material can be fed into the process chamber through an access point; wherein c) graphitable material can be conveyed through the heating zone of the process chamber, in which it is graphitized to graphite; d) a discharge conveyor is provided by means of which the graphite obtained can be discharged from the process chamber through an outlet. 2. Description of the state of the art

[0003] Graphitization of graphitable material takes place in an inert gas atmosphere. It is known to produce polycrystalline graphite, used for anode material, in batch processes in so-called Acheson furnaces, in which graphitable material is graphitized to graphite.

[0004] It is also known from EP 2 980 017 B1 to graphitize graphitable material with large particle diameters of over 3 mm to graphite in vertical graphitization furnaces of the type mentioned above. After this process, the graphite obtained, which has particles too large for use as anode material, must be crushed into graphite powder. From JP 20215 189 646 A and JP 2015 189 644 A, it is known to heat a process tube with a heating coil or with heating electrodes, respectively. SUMMARY OF THE INVENTION

[0005] The object of the invention is to provide a method and a vertical graphitization furnace of the type mentioned above, which are energy-efficient and enable a largely consistent and reproducible graphite quality.

[0006] This problem is solved in a process of the type mentioned above by the fact that e) the process chamber is housed in the interior of a process tube with a tube jacket made of graphite and the process tube is heated by means of an electric heating device due to the electrical resistance of the process tube in the area of ​​the heating zone and a material column is formed in the entire heating zone of a certain process chamber, wherein graphitable material, after being supplied through the access from above, trickles onto the material column through an inlet zone of the process chamber.

[0007] Here and in the following, a "specific" process space is referred to, where applicable. This is intended to express that, where there may be multiple process spaces of a furnace, a specific process space is being considered. This can, but does not necessarily have to, be a process space in which a different variant takes place, provided that these variants can occur simultaneously.

[0008] The variant referred to below as variant B allows a continuous process in a defined atmosphere.

[0009] For a consistently controllable process, it is advantageous if as much volume of graphitable material is supplied to a specific process space per unit of time as the volume of graphite is removed from this process space per unit of time.

[0010] The graphitable material can be fed continuously or intermittently into a specific process chamber, and graphite can be removed from this process chamber continuously or intermittently, with continuous feeding and removal being preferred. In an intermittent process, feeding and removal can occur simultaneously or at different times.

[0011] For a reproducible execution of the process, it is advantageous if the fill level of the material column is kept largely constant.

[0012] As mentioned above, a graphitization furnace with multiple process chambers can be used, with the multiple process chambers operating in parallel over time.

[0013] It is advantageous if the particles of the graphitable material have an average particle diameter greater than 5 µm and less than 3,000 µm, less than 2,500 µm, less than 2,000 µm, less than 1,500 µm, less than 1,000 µm or less than 500 µm, or that the particles of the graphitable material have an average particle diameter of 5 µm to 3,000 µm, of 500 µm to 2,000 µm or of 1,000 µm to 1,500 µm.

[0014] For efficient operation, it is advantageous to determine the temperature of the heating zone, particularly at the top of the heating zone, approximately in the middle of the heating zone, at the bottom of the heating zone, and / or at the material column of each existing process tube. This allows temperature fluctuations in the heating zone to be quickly addressed by controlling the heating system to compensate for undesirable temperature changes.

[0015] In the vertical graphitization furnace of the type mentioned above, the stated problem is solved by the fact that e) the process chamber is housed in the interior of a process tube with a tube jacket made of graphite and an electric heating device is provided with the aid of which the process tube can be heated in the area of ​​the heating zone due to the electrical resistance of the process tube, and the heating zone in at least one process chamber comprises a gravity heating zone and a stationary heating zone, which are arranged in such a way that a column of material is formed in the stationary heating zone and graphitable material, after being supplied through the access from above, can be poured through the gravity heating zone onto the column of material.

[0016] As explained above, it is advantageous if the graphitization furnace has several process chambers.

[0017] Furthermore, a temperature monitoring device is advantageous, by means of which the temperature of the heating zone can be determined, especially at the upper end of the heating zone and / or in approximately the middle of the heating zone and / or at the lower end of the heating zone and / or at the material column of each existing process tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. These show: Figure 1 shows a vertical graphitization furnace according to a first embodiment, in which graphitable material is guided as a column of material from top to bottom through a process chamber, illustrating a first type of process control; Figure 2 shows the vertical graphitization furnace according to Figure 1, illustrating a second type of process flow; Figure 3 a vertical graphitization furnace according to a second embodiment with two parallel process chambers; Figure 4 a modification of the embodiment of Figure 3 , in which the parallel process spaces are spaced apart from each other; Figure 5 a vertical graphitization furnace according to a third embodiment not in accordance with the invention with a conveying system for material containers in which graphitable material is located. DESCRIPTION OF PREFERRED EXAMPLES

[0019] Figure 1Figure 1 shows a vertical graphitization furnace 10, which is used to produce polycrystalline graphite 12 for anode material and is hereinafter referred to simply as furnace 10. The starting material for the production of the polycrystalline graphite 12 is particulate graphitable material 14. Graphitizable materials contain carbon, and graphitization involves the conversion of amorphous carbon to polycrystalline graphite. Examples of graphitable materials are lignite or bituminous coal, and possibly also plastics.

[0020] The particles of the graphitable material 14 preferably have a particle size of less than 3 mm. Preferably, the particles of the graphitable material 14 have an average particle diameter greater than 5 µm and less than 3,000 µm, less than 2,500 µm, less than 2,000 µm, less than 1,500 µm, less than 1,000 µm, or less than 500 µm. Alternatively, the particles can have an average particle diameter of 5 µm to 3,000 µm, 500 µm to 2,000 µm, or 1,000 µm to 1,500 µm.

[0021] The furnace 10 comprises a process tube 16 with a tube jacket 18 made of graphite, which in its interior 20 accommodates a process chamber 22, which defines a vertically arranged inlet zone 24 at the top, a vertically arranged outlet zone 26 at the bottom and a heating zone 28 arranged in between, in which the particles of the graphitable material 14 are graphitized to graphite 12.

[0022] Thus, the upper end 28a of the heating zone 28 is defined at the transition from the inlet zone 24 to the heating zone 28; the lower end 28b of the heating zone 28 is correspondingly defined at the transition from the heating zone 28 to the outlet zone 26. The interior space 20 or the process chamber 22 preferably has a circular cross-section. However, alternative cross-sections, for example elliptical, square, or rectangular, are also possible. As a rule, the outer casing 18 reflects the geometry of the cross-section of the interior space 20 or the process chamber 22 and has a corresponding outer cross-section; however, this can also be different.

[0023] The inlet zone 24 of the process tube 16 is connected at an inlet 30 to an outlet 32 ​​of a feed conveyor 34 for the graphitable material 14, the inlet 36 of which is fed from a material reservoir 38 containing the graphitable material 14. In the present embodiment, the feed conveyor 34 is configured to convey the graphitable material 14 as such and is designed for this purpose, in particular, as a screw conveyor, as is known per se. The outlet zone 24 of the process chamber 22 is correspondingly connected at an outlet 40 to an inlet 42 of a discharge conveyor 44, with which the produced graphite 12 is extracted from the outlet zone 26 and discharged. In the present embodiment, the discharge conveyor 44 is configured to convey the graphite 12 as such, for which purpose the discharge conveyor 44 is also designed as a screw conveyor.However, it is additionally cooled with the help of water cooling, as is also known in and of itself.

[0024] The feed conveyor 34 and the discharge conveyor 44 are designed to create a gas-tight connection to the process pipe 16, allowing conveying to take place even when exposed to the ambient atmosphere. Alternative conveying concepts are also possible, such as rotary valves, double-flap systems in conjunction with, for example, a conveyor belt or a vibrating feeder, or similar devices.

[0025] In the heating zone 28, the process chamber 16 is heated to approximately 2,200 °C to approximately 3,200 °C, preferably to approximately 3,000 °C, for the graphitization process by means of a heating device 46. This temperature is indicated in the figures only by the darker hatched area of ​​the process tube 16. In practice, the heating device 46 is an electric heating device. For example, the wall thickness of the process tube 16 is reduced in the heating zone 28, so that the process tube 16 heats up more effectively there due to the higher electrical resistance. The heating zone 28 is defined by a continuous section of the process chamber 22 in which essentially the same graphitization temperature prevails.

[0026] The process pipe 16 extends through a through-opening 48 in an upper ceiling wall 50 and through a through-opening 52 in a lower bottom wall 54 of an insulating housing 56, made of, for example, sheet steel, such that the process pipe 16 protrudes from the insulating housing 56 with an upper end section 16a pointing upwards and a lower end section 16b pointing downwards. On the inside of the ceiling wall 50 and the bottom wall 54, plate-shaped insulating elements 58, preferably made of graphite-hard felt, are arranged, each with an axially stepped opening 60 for the process pipe 16, defining a stepped surface 62. The respective area of ​​the stepped opening 60 with the smaller cross-section faces the ceiling wall 50 or the bottom wall 54 of the insulating housing 56, so that the stepped surfaces 62 face each other.The insulating elements 58 can be one-piece or formed by two plate-shaped elements having through-openings of different diameters, so that the stepped passage 60 is formed overall.

[0027] From the stepped surface 62 of the insulating element 58 on the ceiling wall 50 to the stepped surface 62 of the insulating element 58 on the floor wall 54, a protective housing 64 made of graphite, for example a protective tube, extends for the process pipe 16 in such a way that an annular space 66 is formed between the process pipe 16 and the protective housing 64, which is open at the top and bottom to the passage openings 48 and 52 of the ceiling wall 50 and the floor wall 54, respectively.

[0028] Radially adjacent to the protective housing 64, an insulating annular space 68 is formed, which is bounded by the protective housing 64, the insulating housing 56 and the insulating elements 58. In the present embodiment, this insulating annular space 68 is filled with soot.

[0029] The through-opening 48 of the ceiling wall 50 is covered by an upper connection cap 70. In the present embodiment, the upper end section 16a of the process pipe 16 extends through the upper connection cap 70, so that an upper connection annular space 72 is formed between the ceiling wall 50 of the insulation housing 56 and the access 30 of the process pipe 16; this is fluidically connected to the annular space 66 via the through-opening 48 and ceiling wall 50 and the passage 60 of the upper insulation element 58.

[0030] The through-opening 52 of the bottom wall 54 is covered by a lower connection cap 74. In the present embodiment, the lower end section 16b of the process pipe 16 extends through the lower connection cap 74, so that a lower connection annular space 76 is formed between the bottom wall 54 of the insulation housing 56 and the outlet 40 of the process pipe 16; this annular space 76 is fluidically connected to the annular space 66 via the through-opening 52 of the bottom wall 54 and the passage 60 of the lower insulation element 58.

[0031] At the upper and lower transitions between the insulation housing 56 and the terminal caps 70 and 74 respectively, a housing cooling device 78 is provided to protect the housing components, which is designed as water cooling, as is known in and of itself.

[0032] A gas space 80 is formed through the connecting annular spaces 72 and 76, the annular space 66 and the passages 60 of the insulating elements 58, which is part of a protective gas system 82.

[0033] The shielding gas system 82 further comprises a first shielding gas inlet connection 84.1 on the upper connection cap 70 and a second shielding gas inlet connection 84.2 on the lower connection cap 74, through which a shielding gas can be blown into the gas space 80.

[0034] Since the insulating elements 58 are porous and therefore gas-permeable, protective gas diffuses from the gas space 80 into the insulating elements 58 through the smaller cross-sectional openings 60 and further into the insulating annular space 68. A protective gas outlet connection 86 is provided on the top wall 50 of the insulating housing 56, allowing the protective gas to be vented. Additionally, a third protective gas inlet connection 84.3 is provided on the bottom wall 54 of the insulating housing 56, enabling the targeted injection of protective gas into the insulating annular space 66.

[0035] The protective gas surrounding the process tube 16 is necessary because the graphitization of the graphitable material 12 takes place under an inert gas atmosphere present in the process chamber 22. The same gas is generally used as the protective gas and the inert gas, so that the same type of gas is present on both sides of the tube jacket 18 of the process tube 16. However, different gases can also be used as the protective gas and the inert gas, in which case the protective gas must also be inert. For example, argon, nitrogen, or helium, or a mixture thereof, can be used as the protective gas and / or the inert gas.

[0036] To introduce inert gas into process chamber 22, the process pipe 16 is coupled at its lower end section 16b to an inert gas inlet connection 88, through which the inert gas can be blown into process chamber 22. The upper end section 16a of the process pipe 16 is connected to an exhaust gas outlet connection 90, so that gases produced during graphitization, mixed with inert gas, can be extracted as exhaust gas from process chamber 22. In this case, the furnace 10 is thus operated in a countercurrent process, in which the inert gas flows through process chamber 22 in the opposite direction to the direction of movement of the material in process chamber 22. Alternatively, the inert gas inlet connection 88 can be located at the upper end section 16a of the process pipe 16 and the exhaust gas outlet connection 90 at the lower end section 16b of the process pipe 16.In a further modification, an inert gas inlet and an exhaust gas outlet can be connected to process chamber 22 at both the top and bottom, so that graphitization can be carried out either in a counterflow or coflow process by switching accordingly. In each of these cases, the exhaust gas is subjected to a thermal afterburner, as is known in and of itself.

[0037] In a further modification, a gassing tube can lead downwards from an inert gas inlet connection 88 arranged at the upper end section 16a to just above the fill level 92 of the material column 94, so that inert gas is blown into the process chamber 22 above the material column 94.

[0038] For the sake of simplicity, components required for conveying protective gas, inert gas or exhaust gas, such as blowers, gas pumps and the like, and associated lines and control devices, are not shown separately.

[0039] Oven 10 is now operated as follows: Before initial commissioning, process chamber 22 and its atmosphere must first be purged of oxygen and moisture, particularly from any air present. For this purpose, process chamber 22 is purged with inert gas, and gas chamber 80 and insulation annular chamber 68 are purged with protective gas.

[0040] The heating device 46 is activated, and graphitable material 14 is fed into the process chamber 22 via the feed conveyor 34 up to a fill level 92. When the discharge conveyor 44 is then activated, it initially conveys incompletely converted material out of the process chamber 22 until graphite 12 obtained in the heating zone 28 reaches the discharge conveyor 44.

[0041] In the ongoing graphitization process, graphitable material 14 is continuously fed into process chamber 22 by the feed conveyor 34, and the graphite 12 obtained from it is continuously removed from process chamber 22 by the discharge conveyor 44. The volume of graphitable material 14 fed in per unit of time, for example per minute, is equal to the volume of graphite 12 removed per unit of time, i.e., potentially per minute, so that the fill level 92 in the process tube 92 remains largely constant. Thus, the furnace 10 is operated continuously with respect to the material supply.

[0042] In one modification, the furnace 10 is operated intermittently with respect to the overall material supply. In this case, graphitable material 14 is continuously fed into the process chamber 22 by the feed conveyor 34, and the graphite 12 obtained from it is simultaneously and continuously removed from the process chamber 22 by the discharge conveyor 44 when a material exchange process is carried out in which a certain volume of graphitable material 12 is removed and replaced by a corresponding volume of graphitable material 14.

[0043] In continuous furnace operation, the conveying speeds of the feed conveyor 34 and the discharge conveyor 44 are set such that the residence time of the graphitable material 14 in the heating zone 28 at approximately 3,000 °C is about 2 to 3 hours. During this time, graphite 12 may already be present in a lower region of the heating zone 28, which is no longer mixed with graphitable material.

[0044] At a temperature of approximately 2,700 °C in heating zone 28, the residence time of the graphitable material 14 can be approximately 10 to 20 hours.

[0045] Figure 1Figure 1 illustrates a process flow in which the fill level 92 in the process pipe 16 corresponds to the height level of the upper end 28a of the heating zone 28. In other words, a material column 94 is formed throughout the entire heating zone 28, extending downwards from the fill level 92 and also through the outlet zone 26 to the outlet 40 of the process pipe 16. The inlet zone 24, on the other hand, is traversed only by graphitable material 14, which, after being fed through the access point 30 into the process chamber 22, trickles down through the inlet zone 24 onto the material column 94 and then becomes part of the material column 94. The term "trickle" here is to be understood as a general term for the downward-falling material without reference to any technical parameters such as the flowability of bulk materials or the like.

[0046] Figure 2This illustrates an alternative method of operation in which the fill level 92 lies below the upper end 28a of the heating zone 28. The material column 94 is therefore not formed throughout the entire heating zone 28. Instead, a gravity heating zone 96 is formed between the material column 94, i.e., the fill level 92, and the upper end 28a of the heating zone 28. Graphitizable material 14 enters this zone from above through the inlet zone 24 and then trickles or falls through the gravity heating zone 94 onto the material column 94, becoming part of it. The gravity heating zone 94 is thus traversed by the graphitizable material 14 as it falls from top to bottom.

[0047] In the process described here, the falling heating zone 96 is a type of free-fall heating zone, which the graphitable material 14 traverses in free fall from top to bottom. The counterflow of the atmosphere in the process pipe 16 towards the exhaust gas outlet 90 can slow the fall of the graphitable material 14 particles compared to free fall, thereby increasing their residence time in the falling heating zone 96. In the modification mentioned above, where the exhaust gas outlet 90 is located at the bottom of the process pipe 16, the gas flow can consequently accelerate the fall of the graphitable material particles compared to free fall, thereby reducing their residence time in the falling heating zone 96.

[0048] In the case of modifications not specifically shown, inert gas can be selectively blown into the falling heating zone 96 in a countercurrent against or in a current in the direction of fall in order to selectively delay or accelerate the falling velocity of the particles of the graphitable material 14 in order to selectively adjust the residence time in the falling heating zone 96.

[0049] The area of ​​heating zone 28 in which the material column 94 is formed defines a stationary heating zone 98, which is encompassed by heating zone 28. The term "stationary" is used merely to clarify that the material column 94 is largely stationary, although it does change due to the material feed and discharge during the operation of the furnace 10. The temperature is at least largely the same in the downward-moving heating zone 94 and the stationary heating zone 98.

[0050] In the falling heating zone 94, the graphitable material 14 is already heated during the trickling process and reaches the material column 94 at a higher initial temperature than in the case of a material column 94 with a fill level 92 at the upper end 28a of the heating zone 28. As a result, material particles of the graphitable material 14 reach the temperature required for graphitization more quickly.

[0051] At the in Figure 2 In the variant shown, the falling heating zone 96 and the standing heating zone 98 each cover approximately 50% of the heating zone 28. In practice, effective graphitization was achieved in a furnace 10 in which the falling heating zone 96 covers between 10% and 60%, preferably between 20% and 55%, more preferably between 30% and 50%, in particular 30% or the illustrated 50% of the heating zone 28.

[0052] Figure 3Figure 1 shows a furnace 10 according to a second embodiment, in which two process tubes 16.1 and 16.2 extend through the insulation housing 56. This embodiment also illustrates further variations in which more than two process tubes 56 are present and extend through the insulation housing 56 accordingly.

[0053] In Figure 3 For the sake of simplicity, not all parts and components are marked with reference numerals; marked parts and components that correspond to the parts and components according to the Figure 1 and 2 Corresponding, are provided with the same reference numerals, whereby the belonging to the first process tube 16.1 or to the second process tube 16.2 is indicated, if applicable, by a corresponding index .1 or .2.

[0054] The protective housing 64 surrounds both process tubes 16.1, 16.2, but it is also possible that each process tube 16.1, 16.2 is assigned a separate protective housing 64.

[0055] Figure 3 It also shows that the process pipes 16.1 and 16.2 are in contact with each other; in a modification that is in Figure 4 As illustrated, the process tubes 16.1 and 16.2 can also be spaced apart from each other, so that soot is also arranged between the process tubes 16.1 and 16.2; the annular space 68 is modified accordingly. The surrounding housings and associated passages and openings are modified accordingly. Consequently, there are two protective housings 64 and annular spaces 66, as well as two upper terminal caps 70 and two lower terminal caps 74, without the fact that all components, which now appear in pairs, are not marked with reference numerals in the figure.

[0056] At the in Figure 3In the illustrated embodiment, each process tube 16.1, 16.2 is assigned a separate feed conveyor 34.1 or 34.2 and a separate discharge conveyor 44.1 or 44.2. In a modified version, there may also be only a single feed conveyor 34, which supplies both process tubes 16.1, 16.2 with material. Accordingly, there may also be only a single discharge conveyor 44, which receives and removes graphite 12 from both process tubes 16.1, 16.2.

[0057] If more than two process tubes 16 are present, a single feed conveyor 34 can supply only one, a pair, or groups of three or more process tubes 16, and optionally all process tubes 16, with graphitable material 14. Similarly, if there are more than two process tubes 16, a single discharge conveyor 44 can receive and discharge graphite 12 obtained from only one, a pair, or groups of three or more process tubes 16, and optionally from all process tubes 16.

[0058] If two process tubes 16.1, 16.2 are each assigned separate feed conveyors 34.1, 34.2 and separate discharge conveyors 44.1, 44.2, the process tubes 16.1, 16.2 can be fed with different graphitable materials 14 that require different residence times in the respective heating zone 28.1, 28.2 or a stationary heating zone 98, the latter being in Figure 3This is shown only using the stationary heating zone 98.2 at process tube 16.2 as an example. This illustrates that different process tubes 16.1, 16.2 can also be operated in different operating modes.

[0059] Regardless of the total number of process tubes 16, the heating zones 28.1, 28.2 can be the same length or different lengths for two different process tubes 16.1, 16.2. If the process tubes 16.1, 16.2 are each operated with a gravity heating zone 96, their lengths, and thus the respective length ratio of gravity heating zone 96 to vertical heating zone 98, can also differ.

[0060] Figure 5Figure 1 illustrates a third embodiment of the furnace 10, which is not according to the invention. In this embodiment, the graphitable material 14 is not introduced into the process chamber 22 as bulk or free-flowing material, but is conveyed through the process chamber 22 and through the heating zone 28 in a material container 100. In the present embodiment, the material containers 100, of which only three are designated by reference numerals, are crucibles 102 with a crucible lid 104. A conveying system 106 is arranged such that a material carrier 100 filled with graphitable material 14 can be conveyed through the inlet 30 into the process chamber 22, from there through the process chamber 22 to the outlet 40, and out of the process chamber 22 through the outlet 40.

[0061] For this purpose, the conveying system 106 comprises the feed conveyor 34 and the discharge conveyor 44, which in this embodiment are configured to convey material containers 100 containing material. The conveying system 106 also includes a process chamber conveyor 108, which is likewise configured to convey material containers 100 containing material in the process chamber 22, and which conveys the material containers 100 from the inlet 30 to the outlet 40.

[0062] Furthermore, in the present embodiment, the conveying system 106 is designed as a circulating conveying system and for this purpose includes a connecting conveyor 110, by means of which material containers 100 can be conveyed from the discharge conveyor 44 to the feed conveyor 34.

[0063] The feed conveyor 34 and the discharge conveyor 44 are designed here as rotary conveyors 112 and 114, respectively, each comprising a rotary element 116 and 118 that can be rotated about a respective vertical axis of rotation 120. The process chamber conveyor 108 and the connecting conveyor 110 are designed as linear conveyors 122 and 124, respectively, each with a push device 126 and a driven push element 128, here in the form of a push rod. In the process chamber conveyor 108, the push element 128 pushes a material container 100 after it enters the process chamber 22 in the inlet zone 24. This material container 100 then collides with the material container 100 below it, thereby pushing all material containers 100 in the process chamber 22 one position further along. For this to work, there is an empty space without material container 100 at exit 40 of process room 22 at this time.

[0064] When the material containers 100 pass through the heating zone 28 on their way through the process chamber 22, the graphitable material 14 is graphitized to graphite 12. A material container 100 at the outlet 40 therefore contains graphite 12. When a material container 100 reaches the outlet 40 of the process tube 16, a void is formed at the inlet 30, so that a material container 100 loaded with graphitable material 14 can be conveyed into the process chamber 22 by the feed conveyor 34. At the end of the conveying section of the connecting conveyor 110, a void is created on the feed conveyor 34, into which an empty material container 100 is then inserted by means of the connecting conveyor 110, which operates in the same way as the process chamber conveyor 108.Any resulting empty space at the inlet of the connecting conveyor 110 is filled with an empty material container 100 by the discharge conveyor 44 when it removes the material container 100 loaded with graphite 12 from the process pipe 16.

[0065] The feed conveyor 34 includes a filling station 130, which fills an empty material container 100 with graphitable material 14. The discharge conveyor 44 includes a discharge station 132, which removes graphite 12 from a material container 100. Suitable airlock systems are implemented to prevent contamination of the furnace atmosphere with foreign atmospheres.

[0066] In the Figure 5In the illustrated proportions, the rotary elements 116 and 118 are designed for four receiving positions for material containers 100, so that a rotation of 90° about the axis of rotation 120 is performed in each cycle. The filling station 130 is reached by an empty material container 100 one cycle before the inlet 30 of the process pipe 16, and the emptying station 132 is reached by a material container 100 filled with graphite 12 one cycle after the outlet 40 of the process pipe 16.

[0067] In process chamber 22, the material containers 100 are therefore conveyed intermittently to the described furnace 10. With a modification and a conveying system 106 designed for this purpose, the material containers 100 can also be conveyed continuously in process chamber 22.

[0068] In all the embodiments described above, the temperature in the heating zone 28 or the temperature of the material column 94 is monitored by a temperature monitoring device.

[0069] For this purpose, the temperature at the upper end 28a of the heating zone 28 and / or approximately in the middle of the heating zone 28 and / or at the lower end 28b of the heating zone 28 of each existing process tube 16 is determined.

[0070] Alternatively or additionally, a temperature measurement can also be taken from above at the fill level 92 of the material column 94.

[0071] The temperature measurements are preferably carried out with a pyrometer with a pyrometer tube, as is known per se, wherein the measuring end of the pyrometer tube is arranged at the respective measuring point. Preferably, the measurement is taken laterally on the heating device 46.

[0072] For the measurement at the heating zone 28, the pyrometer tube, for example, runs from the outside through the outer wall of the insulation housing 56, through the insulation annular space 66, and through the wall of the protective housing 64 into the annular space 66, up to the pipe jacket 18 of the process pipe 16. The associated pyrometer is positioned at the free end of the pyrometer tube on the outside of the protective housing 56. Preferably, the corresponding pyrometer tubes are arranged horizontally. The temperature determined in this way on the outside of the process pipe can be used to calculate the temperature

[0073] If a measurement is to be taken at the top of the material column 94 at level 92, a pyrometer tube extends from the top into the process tube 16 to just above level 92. The pyrometer tube then preferably runs vertically, and the pyrometer is accordingly positioned at the top of the pyrometer tube. However, a horizontal arrangement of the pyrometer tube is also possible. In this case, the pyrometer tube also penetrates the casing 18 of the process tube 16 and opens into the process chamber 22.

Claims

1. A process for producing graphite in a vertical graphitization furnace having at least one process space (22) which delimits a heating zone (28), in which a) a temperature of from 2200°C to 3200°C, in particular of from 2700°C to 3200°C, preferably of 3000°C, is generated in the heating zone (28); b) particulate graphitizable material (14) is fed through an entrance (30) into the process space (22); c) graphitizable material (14) is conveyed through the heating zone (28) of the process space (22), in which it is graphitized to give graphite; d) graphite (12) obtained is discharged from the process space (22) through an exit (40); characterized in that, e) the process space (22) is accommodated in the interior space (20) of a process tube (16) having a tube jacket (18) made of graphite, the process tube (16) is heated by means of an electrical heating device due to the electrical resistance of the process tube (16) in the region of the heating zone (28) and a column of material (94) is formed in the total heating zone (28) of a particular process space (22), with graphitizable material (14) which has been fed in through the entrance (30) trickling from the top through an inlet zone (24) of the process space (22) onto the column of material (94).

2. The process as claimed in claim 1, characterized in that the same volume of graphitizable material (14) is fed into a particular process space (22) per unit of time as the volume of graphite (12) which is discharged from this process space (22) per unit of time.

3. The process as claimed in claim 1 or 2, characterized in that the graphitizable material (14) is fed continuously or intermittently into a particular process space (22) and graphite (12) is discharged continuously or intermittently from this process space (22).

4. The process as claimed in any of claims 1 to 3, characterized in that a fill level (92) of the column of material (94) is kept constant.

5. The process as claimed in any of claims 1 to 4, characterized in that a graphitization furnace (10) which has a plurality of process spaces (22) and whose plurality of process spaces (22) are operated in parallel in time is used.

6. The process as claimed in any of claims 1 to 5, characterized in that the particles of the graphitizable material (14) have an average particle diameter of greater than 5 µm and less than 3000 µm, less than 2500 µm, less than 2000 µm, less than 1500 µm, less than 1000 µm or less than 500 µm, or in that the particles of the graphitizable material (14) have an average particle diameter of from 5 µm to 3000 µm, from 500 µm to 2000 µm or from 1000 µm to 1500 µm.

7. The process as claimed in any of claims 1 to 6, characterized in that the temperature of the heating zone (28) is determined, in particular at the upper end (28a) of the heating zone (28) and / or in approximately the middle of the heating zone (28) and / or at the lower end (28b) of the heating zone (28) and / or at the column of material (94) of each process tube (16) present.

8. A vertical graphitization furnace having at least one process space (22) which delimits a heating zone (28), comprising a) a heating device (46) by means of which a temperature of from 2200°C to 3200°C, in particular of 3000°C, can be generated in the heating zone (28); b) a feed conveyor (34) by means of which particulate graphitizable material (14) can be fed through an entrance (30) into the process space (22); where c) graphitizable material (14) can be conveyed through the heating zone (28) of the process space (22), in which it is graphitized to give graphite; d) an output conveyor (44) is present, by means of which graphite (12) obtained can be discharged from the process space (22) through an exit (40); characterized in that e) the process space (22) is accommodated in the interior space (20) of a process tube (16) having a tube jacket (18) made of graphite, and an electrical heating device is provided by means of which the process tube (16) can be heated due to the electrical resistance of the process tube (16) in the region of the heating zone (28), and the heating zone (28) in at least one process space (22) comprises a falling heating zone (96) and a standing heating zone (98) which are configured such that a column of material (94) is formed in the standing heating zone (98) and graphitizable material (14) which has been fed in through the entrance (30) can trickle from the top through the falling heating zone (96) onto the column of material (94)9. The vertical graphitization furnace as claimed in claim 8, characterized in that a plurality of process spaces (22) are present.

10. The vertical graphitization furnace as claimed in claim 8 or 9, characterized in that a temperature monitoring device is provided, by means of which it is possible to determine the temperature of the heating zone (28), in particular at the upper end (28a) of the heating zone (28) and / or in approximately the middle of the heating zone (28) and / or at the lower end (28b) of the heating zone (28) and / or at the column of material (94) of each process tube (16) present.