Cask with filament for graphitizing carbon materials

Abstract

A system for graphitizing carbon powder comprises a cask having a cask body made of carbonaceous material and a binder, the cask body having a cavity. The system further includes a filament made of carbonaceous material and a binder, the filament being positioned within the cavity and aligned with the cask body.

Description

Technical Field

[0001] This application claims the priority of U.S. Provisional Patent Application No. 63 / 460,516, entitled "Filamented Cask For Graphitization Of Carbon Material", filed on April 19, 2023, the entire content of which is incorporated herein by reference.

[0002] This disclosure relates to casks for graphitizing carbon materials, and more particularly to such casks having filaments.

Background Art

[0003] The graphitization of carbon materials generally involves heating a starting material or payload material, such as amorphous carbon, to a predetermined temperature over a predetermined time period. During the graphitization process, the carbon atoms rearrange, resulting in crystal growth and a decrease in the interlayer spacing to produce graphite. In some cases, the payload material is heated to a temperature of about 2,000°C to 3,000°C or higher in order to effect sufficient graphitization.

[0004] In an Acheson-type graphitization furnace for graphitizing carbon, the payload material is first placed inside a cask. The cask is then placed within a conductive packing material, such as loose coke particles. An electric current is passed through the conductive packing material to heat the cask. Thereby, the cask and the payload material are heated from the outside to the inside by the heat radiated from the packing material. However, Acheson graphitization furnaces require long cycle times and high energy usage.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a vertical graphitization furnace or process (also known as a vertical graphitization furnace / process) for graphitizing carbon materials, the payload material is placed in a cask. An electric current is then passed through the cask and / or the payload material to heat it to a desired temperature over a specified period of time. However, because the payload material is not particularly conductive, heating it to the desired temperature can be difficult and time-consuming. [Means for solving the problem]

[0006] In one embodiment, the present invention is a system for graphitizing carbon powder, the system comprising a cask having a cask body made of a carbonaceous material and a binder, the cask body having a cavity. The system further comprises a filament made of a carbonaceous material and a binder, the filament being positioned within the cavity and aligned with the cask body. [Brief explanation of the drawing]

[0007] [Figure 1] This is an exploded perspective cross-sectional view of a cask with a filament. [Figure 2] This is a front perspective view of a series of casks connected together and positioned within a frame. [Figure 3] This figure shows the cask in Figure 2, which is placed within a layer of loose material. [Figure 4] Figure 1 is a side cross-sectional view of the cask, with the payload material placed inside and adjacent to two other casks. [Figure 5] Figure 1 is a circuit diagram showing the flow of current through the cask towards the cask. [Figure 6] This is an exploded perspective cross-sectional view of another embodiment of a cask having a filament. [Figure 7] Figure 6 shows a side cross-sectional view of the cask with the payload material placed inside. [Figure 8] Figure 6 is a circuit diagram showing the flow of current through the cask towards the cask. [Figure 9]This is an exploded perspective cross-sectional view of another embodiment of a cask having a filament. [Figure 10] Figure 9 shows a side cross-sectional view of the cask with the payload material placed inside. [Figure 11] Figure 10 is a circuit diagram showing the flow of current through the cask towards the cask. [Figure 12] This is a side cross-sectional view of yet another embodiment of a cask having a filament in which the payload material is placed. [Figure 13] Figure 12 is a circuit diagram showing the flow of current through the cask towards the cask. [Figure 14] Figure 12 shows the cask adjacent to two other similar casks. [Figure 15] This is a side cross-sectional view of a cask containing a filament with a partial filament inside. [Figure 16] This is a side cross-sectional view of two adjacent casks having a shared plug. [Figure 17] This is a side cross-sectional view of a cask with floating filaments. [Figure 18] Another side cross-section of a cask with floating filaments. [Figure 19] Another side cross-section of a cask with floating filaments. [Modes for carrying out the invention]

[0008] Referring to Figures 1 and 4, a cask 10 is shown having a cask body 12 and a filament 14 disposed therein. The cask body 12 may be generally cylindrical / hollow, and in the illustrated embodiment it is generally cylindrical with a circular cross-section. However, the cask body 12 may have other shapes or external forms, such as a generally elliptical, square, rectangular, or other shape in cross-section. Similarly, the filament 14 may be solid and generally cylindrical as shown, and in the illustrated embodiment it has a circular cross-section. However, the filament 14 may have other shapes or external forms, such as a generally elliptical, square, rectangular, or other shape in cross-section. Also, as will be described in detail below, the filament 14 may, in some cases, be hollow itself and contain a partial filament.

[0009] The cask body 12 and / or filament 14 can be made from the same or similar materials used to form graphite electrodes for electric arc furnaces, and thus in some cases the cask body 12 can be considered a hollow graphite electrode. Thus, the cask body 12 and / or filament 14 can be substantially or primarily made from a solid material containing carbon and / or made primarily from carbon by weight and / or volume ratio, and / or a carbonaceous material, and / or graphite such as coke (e.g. needle coke), calcined petroleum coke, calcined anthracite graphitized mixture, and a binder, e.g., pitch, coal tar pitch, or petroleum pitch which is molded, calcined, impregnated, graphitized, and machined. The cask body 12 and / or filament 14 can, in some cases, with a load of 20 A / cm², while maintaining their shape and dimensional properties. 2 Current densities exceeding, or in other cases, 30 or 35 A / cm². 2 It may be possible to handle current densities exceeding this limit.

[0010] The cask body 12 and / or filament 14 may be heated to a temperature of at least about 2,000°C in some cases, or at least about 2,800°C in other cases, or at least about 3,000°C in yet another case, or at least about 3,200°C in yet another case, while maintaining their shape and dimensional properties and conductivity. U.S. Patent No. 10,237,928, which is incorporated herein by reference in its entirety, discloses an electrode and a method for manufacturing that electrode, and the materials and methods thereof can be used to manufacture the cask body 12 and / or filament 14 described herein.

[0011] The cask body 12 may include side walls 16 defining an inner cavity 18 and a pair of open ends 20a, 20b facing opposite each other. The cask 10 may have a pair of plugs 22a, 22b, each plug 22a, 22b being coupled to the cask body 12 and configured to cover the associated open ends 20a, 20b. In detail, in the illustrated embodiment, each plug 22a, 22b is a generally cylindrical component and has threaded outer surfaces 24a, 24b configured to screw into corresponding threaded inner surfaces 26a, 26b located at each open end 20a, 20b of the cask body 12. Each plug 22a, 22b may be made from the same material as the cask body 12 and / or filament 14 described above.

[0012] The filament 14 can include a pair of end portions 28a, 28b facing opposite each other, and each plug 22a, 22b is configured to engage with the associated end portions 28a, 28b of the filament 14, whereby the filament 14 can be concentrically suspended inside the cask body 12. Specifically, each plug 22a, 22b can have plug recesses 30a, 30b configured to closely receive therein the associated end portions 28a, 28b of the filament 14. In this way, the filament 14 can extend over the full length or substantially the full length of the cask body 12 (e.g., in some cases at least about 80% of the length of the cask body 12, or in another case at least about 90% of the length of the cask body 12, or in yet another case at least about 95% of the length of the cask body 12), and be completely spaced from the side wall 16 of the cask body 12 along the length of the filament 14 and in some cases can be suspended therein.

[0013] Thus, in some cases, when the cask 10 is empty as shown in FIG. 1, there is no material or component extending radially from the side wall 16 of the cask body 12 to the filament 14 (except for the plugs 22a, 22b located at each axial end of the cask body 12), which maximizes the use of the space of the inner cavity 18 inside the cask body 12, allows the filament 14 to expand / contract relatively freely along its axial length to reduce thermal stress, and can control the flow of current entering and leaving the filament 14. Thus, the filament 14 can be a component separate from / separable from the cask body 12 that can be removed from the cask body (without causing damage / destruction to the cask body 12 or its parts) for inspection, repair and / or replacement.

[0014] The filament 14 can be made relatively small to ensure sufficient space for accommodating the powder / payload material 19 in the inner cavity 18. The filament 14 can occupy less than 40% of the volume of the inner cavity 18 in some cases, less than 20% in other cases, more than 1% of the volume of the inner cavity 18 in other cases, and more than 5% in other cases. In some cases, the filament 14 does not extend through or axially beyond the axial end surface of the cask body 12, and does not extend through or axially beyond each plug 22a, 22b. Instead, the filament 14 is entirely disposed / contained within the cask body 12 and entirely disposed within the inner cavity 18.

[0015] The cask 10 can be used for graphitizing a payload material 19 such as carbon powder in a vertical graphitization process. For example, the cask 10 can be used in conjunction with an adjacent cask 10 or an auxiliary cask 10 that is electrically coupled to this cask 10. A series of casks 10 can be coupled to each other end-to-end or arranged adjacent to each other in this way to form a cask row 32 as shown in FIGS. 2 and 4. Two or more cask rows 32 can be arranged (side by side, and / or vertically, etc.) as shown in FIG. 2 or in other suitable configurations and disposed within a gantry 38. The cask row 32 can be coupled to and / or disposed within a frame 34 having two bars 36 facing each other on opposite sides of each other, and the bars 36 are located at both ends of the cask row 32 (only one bar 36 is shown in FIG. 2). At least one of the bars 36 is axially movable towards the other bar 36, thereby compressing the cask 10 / cask row 32, absorbing tolerances, ensuring a strong mechanical and / or electrical connection, and reducing the contact resistance between various components within the cask row 32.

[0016] In some cases, each cask 10 is pressed directly against an adjacent cask 10, if any, as shown on the right side of Figure 4 (see also Figure 14). In other cases, a conductive, compressible external spacer 29, for example made from flexible graphite in some cases, is placed between two adjacent casks 10, as shown on the left side of Figure 4. The spacer 29 can provide relief of mechanical stress (e.g., from expansion of the cask 10) while maintaining the current flowing through the cask 10. As shown in Figure 3, the cask row 32 can be covered with a layer of loose material 40 for insulation and shielding from atmospheric oxygen to provide a graphitization system 42. The casks 10 / cask row 32 / filaments 14 can be oriented in some cases horizontally or approximately horizontally with respect to a gravity reference frame (e.g., so that their respective central axes are aligned in that manner), but can also be in different orientations, including being oriented vertically (see Figures 17-19), obliquely, etc., if necessary.

[0017] Each hollow cask 10 can be filled with a starting payload material 19, which is a carbon powder material, for example, a carbon powder that, when graphitized, can be used as an active anode material in batteries such as lithium-ion batteries. The payload material 19 can be almost any form of carbon material, in which case it has an average / median particle size of about 1 micrometer to about 100 micrometers. The timing and graphitization process of the payload material 19 can be influenced by various properties of the payload material 19, including density, thermal conductivity, resistivity, carbon yield, and particle size setting. The density and thermal conductivity of the starting payload material 19 strongly affect its heating rate, which may be taken into consideration when designing the cask 10 and filament 14. The electrical resistivity of the starting payload material 19 also affects its heating rate and the overall resistivity of the system. The carbon yield of the starting payload material 19 strongly affects the generation of volatile products that may occur during the graphitization process and is a factor in the environmental performance and safety of the system. Finally, the particle size of the payload material 19 strongly influences all of the above factors through various mechanisms.

[0018] As the payload material 19 is fed into each cask 10 and the cask 10 is closed, current flows through the cask body 12, the filament 14, and, as far as possible, through the payload material 19. However, as a practical matter, the current flowing through the payload material 19 may be relatively low, especially at the beginning of the graphitization process, which is reflected by the high resistance shown in the circuit diagrams of Figures 5, 8, 11, and 13. As a result, the cask body 12 and the filament 14 are resistively heated due to the current flowing through them, transferring heat from the cask body 12 radially inward into the payload material 19 and from the filament 14 radially outward into the payload material 19, thereby increasing the temperature of the payload material 19 and causing it to graphitize. In this embodiment, the payload material 19 may remain largely stationary / in a fixed position during the graphitization process, and more specifically, the payload material 19 does not move along the length of the cask 10 from one open end 20a to the other open end 20b or toward the other open end 20b.

[0019] The cask body 12 and filament 14 can be heated to achieve a predetermined temperature within the payload material 19 over a predetermined period of time. The payload material 19 may be heated to a target temperature of at least about 2,000°C in some cases, or at least about 2,800°C in other cases, or at least about 3,000°C in other cases, or at least about 3,200°C in yet other cases, or may be desired to reach the target temperature, and the target temperature may be maintained over a holding period of at least about 1 hour in some cases, or at least about 3 hours in other cases, or at least about 24 hours in yet other cases. The target temperature may be maintained over a holding period of less than about 24 hours in some cases, or less than about 6 hours in other cases, or less than about 2 hours in other cases, or less than about 0.5 hours in yet other cases. The system 42 can generally bring about graphitization of the payload material 19 faster than conventional Acheson furnaces.

[0020] In one example, the starting payload material 19 is heated to a temperature exceeding 2,900°C for a minimum of 10 hours, and in another example, the payload material 19 is heated to a minimum of 3,200°C for a minimum of 0.5 to 4 hours. If the payload material 19 is to be used as graphite anode powder after graphitization (e.g., in lithium-ion batteries), it may be desirable that the payload material 19 be heated sufficiently to induce graphite crystallization, which leads to a low d-spacing between graphite layer planes. For example, in one case, this d-spacing is desired to be below 3.363 angstroms, and in another case, below 3.360 angstroms. If system 42 is used to graphitize carbon, the finished payload product may be graphite powder having a particle size distribution of D10 5-20 μm; D50 10-30 μm; D90 20-40 μm, a Dmax of 90 μm, and an average / median particle size of 10-30 μm.

[0021] As described above, the payload material 19 can be relatively heat-insulating and insulating. Therefore, the limiting factor determining how quickly the payload material 19 can be graphitized is the amount of time required for the coldest part of the payload material 19 (for example, generally the part of the payload material 19 furthest from the heat source) to reach the desired temperature over the desired period of time. Thus, the presence of the filament 14, which may be located in the center of each cask 10 / payload material 19, significantly reduces the processing time required to raise the entire payload material 19 to a temperature high enough to graphitize it.

[0022] In the embodiments of Figures 1, 4, and 5, each plug 22a, 22b has recesses 30a, 30b at its axially inner end, and each recess 30a, 30b is sized to closely accommodate the ends 28a, 28b of the filament 14. In this embodiment, each plug 22a, 22b has a cylindrical outer threaded surface 24a, 24b (for example, the threads are radially aligned). The cask body 12 has two corresponding cylindrical inner threaded surfaces 26a, 26b at each end facing opposite each other, which are configured to screw-engage with the outer threaded surfaces 24a, 24b of the associated plugs 22a, 22. Furthermore, when the plugs 22a and 22b are screwed into place, they seal the inner cavity 18 of the cask body 12 and compress the filament 14 in the axial direction, ensuring that the filament 14 is held in place and ensuring good mechanical and electrical contact between the filament 14 and the associated plugs 22a and 22b.

[0023] In this embodiment, each recess 30a, 30b is relatively smooth and unthreaded, but is sized to tightly accommodate the ends 28a, 28b of the filament 14 to provide good mechanical contact with the filament and reduce electrical resistance. Thus, in some cases, each recess 30a, 30b is sized to have a diameter, surface area, and / or circumference that is in some cases at least about -1%, and in other cases about -0.1%, of the corresponding diameter and / or surface area and / or circumference (circumference) of the relevant ends 28a, 28b of the filament 14. In this way, when one or both of the plugs 22a, 22b are screwed into the cask body 12, a solid mechanical and electrical contact is established between the cask body 12 and the plugs 22a, 22b, and between the plugs 22a, 22b and the filament 14. The embodiments in Figures 1, 4, and 5 are also relatively easy to manufacture and use.

[0024] In some cases, if necessary, internal spacers 31 (Figure 4), made from the same material and having the same properties as spacer 29 outlined above, may be placed within each recess 30a, 30b. The internal spacers 31 may be physically and / or electrically positioned between the filament 14 and the associated plugs 22a, 22b. The internal spacers 31 may be compressible to accommodate any imperfect tolerances / fits between plugs 22a, 22b and the filament 14. While spacers 31 are shown at each end 28a, 28b of the filament 14, it should be understood that spacers 31 may be used at only one end 28a, 28b, or not at either end. It should also be noted that additional spacers 31 may be used at virtually any contact surface between the graphite components of the cask 10, if necessary. Such spacers may also be used at the ends of the filament 14 in the embodiments described below, but are not specifically shown / referenced in the drawings.

[0025] Figure 5 is a circuit diagram showing the flow of current through the cask, toward the cask in Figure 4. Higher resistance components / connections are visually represented as larger resistance elements. As can be seen, moving from left to right in Figure 5, the spacer 29 provides a moderately large amount of resistance, which is usually desirable to minimize. For the portion of the spacer 29 that is in direct contact with the cask body 12 (e.g., the radially outer portion of the spacer 29), as shown by the top line in Figure 5, the current then flows through the axially adjacent end of the cask body 12, providing a moderately small amount of resistance. Some current may flow through the contact between the cask body 12 and the powder / payload material 19 into the powder / payload material 19, providing a relatively small amount of resistance.

[0026] In the uppermost line of Figure 5, the current flows through the middle portion of the cask body 12, providing a moderately small amount of resistance. Further downstream (relative to the current flow in this particular explanatory example), some of the current may flow through the contact between the cask body 12 and the powder / payload material 19, providing a relatively small amount of resistance. Finally, in the uppermost line of Figure 5, the current flows through the downstream end of the cask body 12, providing a moderately small amount of resistance.

[0027] As shown by the central line in Figure 5, the powder / payload material 19 provides relatively high resistance, at least at the beginning of the graphitization process, due to the intrinsic properties of the powder 19.

[0028] Starting from the left of the bottom line in Figure 5 (upstream relative to the current flow in this particular explanatory example), for the current flowing through plug 22a, a small amount of resistance is provided at the point of contact between the cask 12 and the cylindrical threaded surfaces 24a, 26a of plug 22a in Figures 1 and 4. The current then flows through plug 22a, which provides a moderately small amount of resistance due to the material from which plug 22a is made and the orientation of those materials. The current then flows through the contact between plug 22a and spacer 31, and the contact between spacer 31 and filament 14, which provides a relatively small amount of resistance. The current then flows through filament 14 and also through powder / payload material 19 (through the moderately low resistance provided between filament 14 and powder / payload material 19). Filament 14 provides a moderately high resistance. Needless to say, as outlined above, the current passing through the filament 14 heats the filament 14 by Joule heating, and in turn, the heat radiated from the filament 14 outwards heats the payload material 19.

[0029] After the current flows through the filament 14 along the bottom line in Figure 5, some of the current may flow into and out of the powder / payload material 19 through the moderately low contact resistance provided between the filament 14 and the powder 19. The current encounters relatively small resistance at the intersection of the filament 14 and the spacer 31, and between the spacer 31 and the plug 22b. The current then flows through the plug 22b, which provides moderately small resistance. The current then encounters relatively small resistance at the point of contact between the threaded surface 24b of the plug 22b and the threaded surface 26b of the cask body 12. Finally, the current flows into the adjacent cask 10 shown on the right in Figure 4.

[0030] In some cases, each resistive component in the system 42 (e.g., each resistive component shown in some cases by the resistance symbol in Figure 5 (or Figure 8, Figure 11 or Figure 13), and / or other resistive components or configurations not explicitly shown), excluding the resistance provided by the filament 14, the cask body 12, and the payload material 19 (which are desired to provide relatively high resistance and / or be heated), provides, in some cases, less than 0.5%, or in other cases less than 1%, of 1) the total resistance of the system 42 during operation, and / or 2) the Joule heating of the system 42 during operation. In some cases, each resistive component in the system 42, together (again, excluding the resistance provided by the filament 14, the cask body 12, and the payload material 19), provides, in some cases, less than 10%, or in other cases less than 5%, or in other cases less than 3%, of 1) the total resistance of the system 42 during operation, and / or 2) the Joule heating of the system 42 during operation. Conversely, in some cases, the filament 14, the cask body 12, and the payload material 19 provide, in some cases, at least 90%, in other cases at least 95%, or in yet another case at least about 97%, of 1) the total resistance of the system 42 during operation, and / or 2) the Joule heating of the system 42 during operation. These parameters may be applicable in some cases at the beginning of the graphitization process, and / or in other cases at the end of the graphitization process, and / or at any or all intermediate stages.

[0031] In the embodiments shown in Figures 6 to 8, the outer threaded surface 24a of the plug 22a is conical (for example, the threads are aligned in a radially angled plane). The threaded surface 26a of the cask body 12 is correspondingly conical and configured to screw-engage with the outer threaded surface 24a of the plug 22a. In this embodiment, the threaded surfaces 24a and 26a are angled radially inward as they advance from the outer axial surface in the axial inward direction, so that the plug 22a can be screwed into the cask body 12 from the outside, making assembly easy. The tapered threaded surfaces 24a and 26a provide increased mechanical contact between the plug 22a and the cask body 12, which reduces electrical contact resistance, and the tapered nature of the threaded surfaces 24a and 26a can also better handle compressive loads and better distribute compressive loads.

[0032] Furthermore, in this particular embodiment, the end 28a of the filament 14 has or removes the form of a conical outer threaded surface, and the corresponding recess 30a of the plug 22a has a conical inner threaded surface 30a configured to screw-engage with the threaded end 28a. In this embodiment, the threaded surfaces 28a, 30a are angled radially outward as they advance axially inward from the outer axial surface, so that the filament 14 can be screwed into the recess 30a from the inside of the cask body 12, making assembly easier. The tapered threaded surfaces 28a, 30a provide increased mechanical contact between the filament 14 and the plug 22a, which reduces electrical contact resistance, better handles compressive loads, and better distributes compressive loads. Also in this embodiment, the recess 30a extends across the entire thickness of the associated plug 22a.

[0033] In this embodiment, the outer threaded surface 24b of the other plug 22b is cylindrical, and the corresponding threaded surface 26b of the open end 20b of the cask body 12 is also cylindrical. Also, as shown, the end 28b of the filament 14 and the plug recess 30b are not threaded, resulting in an asymmetrical design for the cask 10. However, if necessary, the threaded surfaces 24b / 26b can be conical threaded surfaces, and / or the end 28b and plug recess 30b can be cylindrical threaded surfaces. It should also be understood that the threaded surfaces 28a / 30a and / or threaded surfaces 24a / 26a in the embodiments of Figures 6-8 can be cylindrical threaded surfaces if necessary, instead of conical threaded surfaces. In general, conical threaded surfaces can provide lower electrical resistance compared to cylindrical threaded surfaces, and / or can better handle compressive loads and distribute compressive loads more favorably. However, conical threaded surfaces can be more difficult to machine and may be more difficult to screw into mating threaded surfaces.

[0034] In the embodiments shown in Figures 9 to 11, each plug 22a, 22b has a conical outer threaded surface 24a, 24b configured to screw onto the corresponding conical threaded surface 26a, 26b of the cask body 12. In this embodiment, the plug 22b / recess 30b also includes a cylindrical inner threaded surface 44 located axially outward, which extends at least partially over its thickness. The cask 10 further includes an insert 46 in the form of a solid disc or the like, which has an outer threaded surface 48 configured to screw into the threaded surface 44 of the plug 22b / recess 30b. The insert 46 can be made from the same material as the cask body 12, filament 14 and / or plugs 22a, 22b described above.

[0035] When the insert 46 is screwed into place, it engages with the end 28b of the filament 14, compressing the filament 14 in the axial direction. Thus, in this embodiment, the compression applied to the filament 14 can be independent of the axial positioning of the plugs 22a, 22b within the open ends 20a, 20b of the cask 10, and the cask 10 can be sealed without excessively or insufficiently compressing the filament 14. If necessary, the recess 30a of the other plug 22a may have a corresponding threaded surface that accommodates another insert (not shown).

[0036] It should be noted that the plugs 22a, 22b and / or inserts 46 tend to conduct electricity primarily radially due to their "puck" shape, and therefore the plugs 22a, 22b and / or inserts 46 can be configured to have low electrical resistance and / or thermal expansion coefficients, particularly radially. In contrast, the cask body 12 and / or filament 14 tend to conduct electricity primarily axially because they are relatively long objects that extend primarily axially. Therefore, the cask body 12 and / or filament 14 can be configured to have low electrical resistance and / or thermal expansion coefficients, particularly axially. The relative resistivity and other properties of the cask body 12 and filament 14 can also be selected to minimize the temperature gradient, maximize the rate and energy efficiency of graphitization, and improve the safety and stability of the system 42 and the process.

[0037] The electrical resistivity of the materials of the cask 10 / cask body 12 / filament 14 may, in some cases, be greater than about 2 microohms and / or less than about 20 microohms, and may be selected to properly balance current and power within the constraints of a typical rectifier system supplying current to the cask 10. Compared to metals, the resistivity of the cask 10 / cask body 12 / filament 14 is relatively high, and therefore requires higher voltage and lower current to maintain a given level of Joule heating. When used in high-voltage, high-current rectifier systems, the range of resistivity of the cask 10 / cask body 12 / filament 14 may also be appropriately matched. The resistivity of the cask body 12 and filament 14 may not be desired to be the same, but instead may be selected so that the Joule heating of the cask body 12 and filament 14 remains constant throughout the heating cycle. For example, if the side wall 16 of the cask body 12 is 3 inches thick and 24 inches in diameter, and the filament 14 has a diameter of 6 inches, then the cask-filament ratio of resistivity may be desired to be 1:1 to 1:2.

[0038] The coefficients of thermal expansion of the cask body 10 / cask body 12 / filament 14 may be desirable to be approximately the same in order to reduce thermal stress within the system 42. The cask 10 / cask body 12 / filament 14 should be made of a material that is strong enough to support itself without breaking or being damaged when in a lateral cantilever configuration at rest.

[0039] In the embodiments shown in Figures 1 and 4-11, the filament 14 and plugs 22a, 22b may be configured such that when the plugs 22a, 22b are screwed to the cask body 12 with the filament 14 placed between them and compressed, the axial outer ends of each plug 22a, 22b are recessed axially with respect to the corresponding end face 50 of the cask body 12, providing an "inset" configuration and resulting in a gap 51 directly between adjacent casks 10, as shown in Figure 4. In this case, the current flows first through the cask body 12, then through the plugs 22a, 22b and / or inserts 46, and then through the filament 14. This embodiment can be used in situations where the filament 14 has a higher electrical resistivity than the cask body 12, and the relatively low current flowing through the filament 14 can lead to a relatively high temperature / heating. Thus, the recess / inset design in Figures 1 and 4-11 provides a mechanism for controlling the current distribution through the cask 10. Furthermore, the recessed / inset configuration reduces the compressive force applied to the plugs 22a and 22b, which allows the plugs 22a and 22b to be made from lower-strength, less expensive materials, and may also extend the lifespan of the plugs 22a and 22b.

[0040] In an alternative embodiment, as shown in Figures 12 to 14, the filament 14 and plugs 22a, 22b are configured such that when the plugs 22a, 22b are screw-coupled to the cask body 12 with the filament 14 between them and compressed, the axial outer ends of each plug 22a, 22b protrude axially beyond the corresponding end face 50 of the cask body 12, providing an "outset" configuration. This configuration can provide a direct electrical connection between the plugs 22a and 22b, thereby reducing resistance within the system 42 and reducing heat loss, which can help provide more effective heating of the payload material 19.

[0041] In some cases, as shown in Figure 15, the filament 14 may, if necessary, be hollow itself and include a partial filament 14a placed inside. In this case, the filament 14 may act as a second cask body providing a second cavity 18a to increase the yield of the cask 10 and be filled with payload material 19. The partial filament 14a may be made from the same material as the filament 14 and may be placed and held inside the filament 14 in any of the methods described and illustrated herein in relation to the filament 14, or in other methods as necessary.

[0042] In yet another embodiment, as shown in Figure 16, one or each of the plugs 22a, 22b (plug 22b in the embodiment shown) may have sufficient axial length so that 22b can be accommodated simultaneously at the open ends 20a, 20b of two adjacent casks 10, and may have sufficient threads on its outer surface 24b. Thus, in addition to closing the open ends 20a, 20b of two related casks 10, plug 22b can also connect two adjacent casks 10 to each other. Plug 22b thus acts as a double threaded joint, and this configuration can help provide electrical conductivity between adjacent casks 10. The position, dimensions, and other characteristics of spacers 29, 31 may also be adjusted as needed to control the resistance and other characteristics of the system 42, as well as the current flowing through each cask 10.

[0043] Figure 17 discloses an alternative embodiment in which the filaments 14 are spaced apart axially and do not directly contact one or each of the plugs 22a, 22b. In this case, the plugs 22a, 22b do not need to include recesses 30a, 30b, and the plugs 22a, 22b and the filaments 14 do not need to have threaded surfaces. Instead, a pad 52 or portion 52 of graphitized powder is positioned axially between the filaments 14 and the plugs 22a, 22b, in direct contact with the filaments 14 and the plugs 22a, 22b, thereby electrically coupling the filaments 14 and the plugs 22a, 22b.

[0044] Each pad 52 can, in some cases, be made from a graphitized material having the same properties as the powder 19 / payload material 19 outlined above after graphitization. The pad 52 may be more conductive than the powder 19 / payload material, at least before graphitization of the powder 19 / payload material. However, the pad 52 can be made from almost any carbon material, which may be in the form of loose, powdered, and / or granular and / or flakes, such as coke or graphite, which may, in some cases, contain calendered expanded graphite flakes of a given thickness, and the material may, in some cases, be compressed to form the pad 52 into a cylindrical shape that can maintain its dimensions when there is no surrounding support structure.

[0045] Each pad 52 may have a thickness of, in some cases, more than 1% and in other cases more than 5% of the axial length of the cask 10 / cask body 12, and / or, in some cases less than 25% and in other cases less than 15% of the length of the cask 10 / cask body 12. In the embodiment of Figure 17, each pad 52 covers the entire surface area of ​​the associated plugs 22a, 22b at its axial outer end, matching the surface area / diameter / effective diameter of the axial inner surface of the associated adjacent plugs 22a, 22b (for example, each pad 52 has a surface area and / or diameter (or effective diameter)). Also, Figure 17 shows the axial ends 28a, 28b of the filaments 14 in contact with the end surface of the pad 52, but the axial ends 28a, 28b of the filaments 14 may be at least partially "embedded" in one or both of the pads 52 such that at least a portion of the curved outer surface of each filament 14 also contacts each pad 52.

[0046] To form the cask configuration of Figure 17, a cask body 12 having a stopper 22a may be provided arranged in a longitudinal configuration as shown. The bottom pad 52 can then be formed by placing the pad material 52 into the cavity 18 and the bottom pad material 52 on top of the stopper 22a. The bottom pad material 52 can be placed loosely into the cavity 18 and then compacted, or, in other cases, pre-compacted pad material 52 can be placed as a unit at the bottom of the cavity 18. The filament 14 can then be placed in the center of the cavity 18 on top of the bottom pad 52. The payload material 19 can then be placed around the filament 14 to fill the cavity 18. The top pad 52 can then be formed by placing the top pad material 52 into the cavity 18, on top of the filament 14 and the payload material 19. The stopper 22b can then be joined to the cask body 12 and fixed in place.

[0047] Therefore, in the embodiment of Figure 17, unlike the embodiments of Figures 1 and 4-16, it can be seen that the filament 14 does not directly contact the plugs 22a, 22b, and / or is not constrained by them, and / or is not housed within them, and / or is not directly mechanically coupled to them. Thus, the filament 14 in the embodiment of Figure 17 can be considered a “floating” filament 14. The buoyancy of the filament 14 allows the payload material 19 to support and position the filament 14 without thread contact and without applying pressure or compression to the filament 14. This simplifies the installation and removal of the filament 14, for example, because it does not require screwing in and unscrewing the filament 14. It also simplifies the loading and unloading of the payload material 19, as the filament 14 can be easily removed to provide full access to the payload material 19. Furthermore, it eliminates the concentration of stress applied to the root of the threaded surface. It also simplifies the formation / manufacturing of the cask body 12 because machining work is reduced. Finally, unlike threaded designs, the filaments cannot be placed in an unsupported cantilever configuration, which could result in damage to the filaments 14 and / or the plugs 22a, 22b (for example, when the cask 10 is in a horizontal configuration with no payload material 19 inside the cask 10).

[0048] On the other hand, the threaded embodiment can offer advantages over the floating filament embodiment. In detail, the threaded connection can provide lower resistance compared to the use of pad 52, which can reduce the amount of internal heating (e.g., reduce heat loss). Also, the threaded filament design provides fixed shape dimensions, which eliminates any undesirable positioning of the filament. The use of threaded and unthreaded embodiments provides choices to optimize the alignment, stability, and performance of the system.

[0049] As described above, in the embodiment of Figure 17, each pad 52 extends to the entire diameter / surface area of ​​the associated plugs 22a, 22b. In an alternative embodiment, as shown in Figure 18, the pad 52 extends to less than the entire diameter / surface area of ​​the associated plugs 22a, 22b. More specifically, in the embodiment of Figure 18, each pad 52 covers the entire surface area of ​​the axial end surface of the filament 14 (for example, each pad 52 has a diameter (or effective diameter) at its axial inner end that matches that of the axial outer end surface of the filament 14). In this case, the payload material 19 extends to one or each of the plugs 22a, 22b and is in direct contact with the plugs. As can be seen, in the embodiment of Figure 18, the pad 52 can have a longer axial length compared to the pad 52 in Figure 17. The larger cross-sectional area provided by the pad 52 in Figure 17 provides a low-resistance path for current to flow from the plugs 22a, 22b to the filament 14, directly through the pad 52 / filament 14 contact and / or through the payload material 19 / filament 14 contact. The smaller cross-sectional area provided by the pad 52 in Figure 18 can be somewhat compensated for by extending its axial length, which allows more current to enter the pad 52 radially through the payload material 19, providing a low-resistance connection with the filament 14.

[0050] The embodiment in Figure 18 can process a larger amount of payload material 19 compared to the embodiment in Figure 17. However, conversely, the embodiment in Figure 18 may not provide as effective heating of the filament 14 as the embodiment in Figure 17.

[0051] The embodiment in Figure 18 may be more complex to load / assemble than the embodiment in Figure 17 and may require the use of a sleeve to hold the payload material in place. Specifically, to form the cask 10 of Figure 18, a cask body 12 having a plug 22a may be provided arranged in a longitudinal configuration as shown. A sleeve (not shown) having a diameter matching the diameters of the pad 52 and filament 14 can then be inserted into the cavity 18. The bottom pad 52 can then be formed by placing the pad 52 material into the sleeve and compacting the pad material if necessary. The filament 14 can then be placed on top of the bottom pad 52 within the sleeve. The top pad 52 can then be formed by placing the top pad 52 material into the sleeve and compacting the material if necessary. The payload material 19 can then be placed around the sleeve, filling the remaining space within the cavity 18. The sleeve can then be removed and the plug 22b can be coupled to the cask body 12 and secured in place, resulting in the configuration shown in Figure 18.

[0052] In another embodiment shown in Figure 19, the upper and lower pads 52 are omitted, and instead, payload materials 19a, 19b are positioned next to the ends 28a, 28b of the filament 14 and directly axially between the filament 14 and the plugs 22a, 22b. The use of a floating filament 14 without pads 52 and the use of payload materials 19 instead may result in reduced performance due to the lower conductivity of the payload materials 19 compared to the pads 52, but such embodiments are easier to implement and reduce the types and quantities of different materials that must be stored in the field.

[0053] The cask 10 and configuration disclosed herein can provide low contact resistance between the plugs 22a, 22b and the cask body 12, and between the plugs 22a, 22b and the filament 14, ensuring that both (functionally and / or physically) equivalent conductive structures (cask body 12 and filament 14) have approximately the same current density during use / operation. Furthermore, the contact surfaces between the cask body 12 and the plugs 22a, 22b (and between the plugs 22a, 22b and the filament 14) can be designed to provide good mechanical and electrical contact and reduce electrical resistance, thereby improving performance and reducing hot spots caused by high contact resistance. Finally, the various designs disclosed herein provide a robust system that is easy to assemble and disassemble, which can be useful since the cask 10 is typically designed to be inserted and removed many times over its service life.

[0054] Although the present invention has been described in detail with reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A system for graphitizing carbon powder, wherein the system includes a cask. The aforementioned cask, A cask body made of carbonaceous material and binder, comprising a cask body having a cavity, A filament made from a carbonaceous material and a binder, wherein the filament is configured to be placed in the cavity and aligned with the cask body, and A system that includes these features.

2. The system according to claim 1, wherein the system is configured for vertical graphitization of graphite powder, and both the cask body and the filament have an electrical resistivity of about 2 microohms to about 20 microohms and are capable of withstanding a temperature of at least about 2000 degrees Celsius, and the carbonaceous material of the cask body is coke, and the carbonaceous material of the filament is coke.

3. The system according to claim 1, wherein the cask body is generally cylindrical, the filament extends over at least about 80% of the length of the cask body, the filament is aligned with the central axis of the cask body, the filament is spaced apart from the side walls of the cask body, the filament is removable from the cask body, and the filament does not extend axially beyond the cask body.

4. The system according to claim 1, wherein the cask includes a pair of plugs at each end thereof, each plug configured to be coupled to a relevant open end of the cask body and cover the open end, and each plug configured to be electrically coupled to a relevant end of the filament.

5. The system according to claim 4, wherein at least one stopper has a cylindrical outer threaded surface, and the cask body includes a cylindrical inner threaded surface configured to screw-engage with the outer threaded surface of the at least one stopper.

6. The system according to claim 4, wherein at least one stopper has a conical outer threaded surface, and the cask body includes a conical inner threaded surface configured to screw-engage with the outer threaded surface of the at least one stopper.

7. The system according to claim 4, wherein each plug is configured to be screw-coupled to the cask body, and the filament and at least one plug are configured such that when the at least one plug is screw-coupled to the cask body with the filament compressed between them, the axial outer end of the at least one plug extends axially beyond the relevant end face of the cask body.

8. The system according to claim 4, wherein each stopper is configured to be screw-connected to the cask body, and the filament and at least one stopper are configured such that when the at least one stopper is screw-connected to the cask body with the filament compressed between them, the axial outer end of the at least one stopper is recessed axially with respect to the corresponding end face of the cask body.

9. The system according to claim 4, wherein each stopper is configured to be screw-connected to the cask body, and at least one stopper includes a recess configured to tightly accommodate the associated end of the filament.

10. The system according to claim 9, wherein the recess of the at least one stopper is not threaded.

11. The system according to claim 9, wherein the recess of the at least one plug has an inner threaded surface configured to screw-engage with the threaded outer surface of the filament.

12. The system according to claim 9, wherein the recess of the at least one stopper extends over the entire thickness of the at least one stopper.

13. The system according to claim 12, further comprising an insert configured to be screw-inserted into the recess of at least one stopper and to engage with the associated end of the filament when the recess accommodates the associated end of the filament.

14. The system according to claim 1, wherein the filament has a cavity inside, and the system further comprises a partial filament made of a carbonaceous material and a binder, the partial filament being aligned with the filament, positioned within the cavity of the filament, and generally spaced apart from the filament.

15. The system according to claim 1, wherein the cask includes at least one stopper, the at least one stopper is configured to be screw-coupled to a related end of the cask body, and the stopper is also configured to be screw-coupled to an adjacent end of the cask body at the same time.

16. The system according to claim 1, further comprising an auxiliary cask axially aligned with the cask and electrically communicating with the cask, wherein the cask and the auxiliary cask are in direct contact with each other and are compressed together axially, the cask and the auxiliary cask are arranged in a layer of thermally insulating bulk material, and the cask is filled with a loose or powdery amorphous carbon payload material.

17. The system according to claim 1, wherein the cask comprises a pair of plugs at each end thereof, each plug configured to be coupled to a corresponding open end of the cask body and cover the open end, and the filaments are spaced apart from each plug.

18. The system according to claim 17, further comprising a pair of pads, each pad positioned between the cask and associated adjacent plugs and in contact with them.

19. The system according to claim 18, wherein each pad is made of a carbonaceous material.

20. The system according to claim 18, wherein each pad has a surface area at its axial outer end that corresponds to the surface area of ​​the axial inner surface of the associated plug.

21. The system according to claim 18, wherein each pad has a surface area at its axial inner end that corresponds to the surface area of ​​the relevant axial end surface of the filament.

22. The system according to claim 17, wherein the cask is filled with an amorphous carbon payload material in loose or powder form, and the payload material is directly axially positioned between the filaments and each stopper.

23. A system for use in graphitizing carbon powder, wherein the system comprises a cask. The aforementioned cask, A cask body made of carbonaceous material and binder, comprising a cask body having a cavity, A filament made from a carbonaceous material and a binder, wherein the filament is configured to be placed in the cavity and aligned with the cask body, A pair of plugs at each end of the cask body, each plug configured to be coupled to the relevant open end of the cask body and cover the open end, and each plug configured to be electrically coupled to the relevant end of the filament, and A system that includes these features.

24. A step of accessing a cask, the cask having a cask body made of a carbonaceous material and a binder, wherein the cask body has an inner cavity, the cask contains a filament made of a carbonaceous material and a binder, and the filament is positioned within the inner cavity; The steps include: introducing a loose or powdered amorphous carbon payload material into the inner cavity; The steps include: passing an electric current through the cask body and the filament for a predetermined time in order to heat the cask body, the filament and the payload material sufficiently to cause graphitization of the payload material; Methods that include...

25. The method according to claim 24, wherein during the flow step, the filament, the cask body, and the payload material together provide at least 90% of the Joule heating of the cask.

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