WO1998055426A1 - Production of heat-treated carbon bodies - Google Patents
Production of heat-treated carbon bodies Download PDFInfo
- Publication number
- WO1998055426A1 WO1998055426A1 PCT/US1997/009714 US9709714W WO9855426A1 WO 1998055426 A1 WO1998055426 A1 WO 1998055426A1 US 9709714 W US9709714 W US 9709714W WO 9855426 A1 WO9855426 A1 WO 9855426A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- green
- petroleum coke
- packing material
- blend
- calcined
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/12—Anodes
- C25C3/125—Anodes based on carbon
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
- C04B35/528—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components
- C04B35/532—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite obtained from carbonaceous particles with or without other non-organic components containing a carbonisable binder
Definitions
- prebaked carbon anodes are usually manufactured at the metal production facility in auxiliary facilities associated with the metal production itself.
- the manufacture of the prebaked carbon anodes generally proceeds by mixing crushed, calcined delayed petroleum coke, or in some instances, calcined fluid petroleum coke or calcined pitch coke, with remnants of earlier manufactured prebaked anodes and a binder, such as coal tar pitch, followed by shaping the green mixture into blocks and baking of the blocks to about 1150°C.
- baking removes volatile matter and improves the electrical conductivity of the anodes.
- Packing around the blocks with petroleum coke is required in order to support the anodes to prevent deformation and restrict oxidation while baking.
- the coke used for packing is generally recycled within the ring furnace for use in subsequent baking cycles.
- about 5 to 40 kilograms of packing material is consumed in the baking process and must be replenished to achieve the above-stated purposes.
- the calcined petroleum coke either the delayed or the fluid type, which is used as packing material in the ring furnace, must be purchased by the smelter from calcined coke manufacturers, who produce the calcined petroleum coke from green petroleum coke supplied by oil refineries. Green petroleum coke is produced by the refineries as part of the petroleum refining process and is routinely sold by them to calcined coke manufacturers for further processing and ultimate sale to industrial consumers, such as aluminum smelters. At the aluminum smelters, the calcined coke is used both as an anode constituent and as th* packing agent in the ring furnace.
- prebaked carbon anodes are produced in open-pit, ring furnaces and where the packing material utilized is either type of calcined coke, such coke undergoes multiple heat treatment processes, the first one involving its original manufacture from green coke by calcination, the latter ones are associated with the cyclical manufacture of prebaked carbon anodes.
- Calcination of green petroleum coke whether used for making of calcined delayed petroleum coke or calcined fluid petroleum coke, entails significant energy usage.
- the packing material utilized in the manufacture of prebaked anodes in open-pit, ring furnaces can entail the use of green (uncalcined) delayed petroleum coke or green fluid petroleum coke.
- either type of green petroleum coke may be substituted for calcined petroleum coke to correspondingly replenish the packing material regularly consumed in the open pits during the baking of the anodes.
- the green coke used in accordance with the invention can be either blended with the corresponding type of used calcined delayed petroleum coke or calcined fluid petroleum coke, which used cokes have been recovered from the ring furnace where they were employed as packing materials, or with the corresponding types of unused calcined petroleum cokes. Mixtures of the corresponding types of used and fresh calcined cokes can also be used in combination with the green coke utilized.
- the green petroleum coke employed in the packing material can be advantageously of a lower quality than typical electrode-grade calcined petroleum coke.
- the lower quality green petroleum coke may only be used in the packing material.
- An improved method for making prebaked carbon anodes in open-pit, ring furnaces.
- the method involves the preparation of green carbon anode blocks in the conventional manner, positioning the anode blocks in an open-pit, ring furnace; surrounding the anode blocks with particles of a carbonaceous material, the carbonaceous packing material being selected from a mixture of green petroleum coke (GPC) and calcined petroleum coke (CPC), or GPC and recycled calcined petroleum coke ( RPC) , or a mixture of GPC with both calcined petroleum coke (CPC) and RPC; and subjecting the anode blocks to a heat- reatment .
- GPC green petroleum coke
- CPC calcined petroleum coke
- RPC recycled calcined petroleum coke
- the carbonaceous packing material may be utilized in the ring furnace as a blend of GPC and CPC and/or RPC, or these individual packing materials may be placed in the ring furnace around the green anodes not as a blend but so that the total packing material utilized includes GPC and CPC and/or RPC.
- a major purpose of the improved method is to allow the prebaked anode producer to replenish his packing material inventory in the baking pits through the intermittent use of green petroleum coke rather than the calcined petroleum coke.
- the total quantity of green petroleum coke used from time to time in the packing material can be selected within a broad range. Depending on the characteristics of a particular baking furnace and the user's needs from about 1% to about 70% of the aforesaid blend can be green petroleum coke.
- the heat-treatment of the green anode blocks, with packing materials containing GPC is generally accomplished at temperatures averaging about 1150°C.
- Figure 1 shows the schematic view of a typical open-pit ring furnace
- Figure 2 shows a transverse cross-sectional view of an individual baking pit and two adjacent flues of an open-pit ring furnace containing the green anode blocks to be baked surrounded by carbonaceous packing material;
- Figure 3(a) shows the longitudinal cross-section of a fully packed baking pit
- Figure 3(b) shows the transverse cross-section of a fully-packed baking pit.
- a blend of packing material surrounds the lateral surfaces of the green anode blocks while the top surfaces of the blocks are covered by recycled calcined petroleum coke.
- This invention relates to a method for the manufacture of heat-treated carbon bodies. More particularly, this invention relates to an improved method for the manufacture of heat-treated carbon bodies in open-pit, ring furnaces.
- the improved method will be described in detail with respect to the manufacture of prebaked carbon electrodes for use in the electrolytic production of metals, and more specifically, the manufacture of carbon anodes for the electrolytic production of primary aluminum.
- the method of the present invention is capable of producing heat-treated carbon bodies, including graphite electrodes, which can be utilized in industries other than those engaged in the electrolytic production or smelting of metals.
- GPC green petroleum coke
- green fluid petroleum coke green fluid petroleum coke
- GPC green delayed coke
- calcined petroleum coke or "CPC” shall mean a particulate carbonaceous product which has been produced from green petroleum coke by calcining the green petroleum coke in a calcining facility at temperatures in excess of about 1100°C, generally within the range of 1150-1350°C;
- RPC Recycled petroleum coke
- used petroleum coke or "RPC” means a particulate carbonaceous product which has previously been used in the open-pit, ring furnace as packing material for the green carbon bodies to be baked.
- the RPC can be derived from calcined delayed petroleum coke, calcined fluid petroleum coke, or green petroleum coke, which GPC has previously undergone baking in the open-pit ring furnace while it has been used as part of the packing material.
- the packing agent utilized in the ring furnace contains either delayed coke derived packing material or fluid coke derived packing material but not a mixture of these two different types of cokes;
- green anode or “green anodes” mean anode blocks to be subjected to baking in an open-pit, ring furnace while surrounded with a carbonaceous, particulate packing material;
- volatiles mean volatile and combustible vapors evolved from either the green anodes or from GPC, for example, hydrogen, water, carbon oxides and other compounds, as may be determined by standard laboratory methods;
- butts mean the residues or remnants of baked anodes recovered from the electrolytic aluminum reduction process.
- the baked anodes to be used by aluminum smelters in the electrolytic production of primary aluminum are generally produced from a carbonaceous mixture. While most aluminum smelters have their own proprietary carbonaceous compositions used for the manufacture of prebaked anodes, generally these carbonaceous mixtures contain calcined delayed petroleum coke (CDC) and butts and a carbon-containing binder. Certain aluminum smelters are known to utilize alternative carbon materials in their anode production, including calcined fluid petroleum coke and calcined coal tar pitch coke, as well as CDC. Regardless of the differing anode mass compositions, the novel baking method of the invention may be applied to all of the existing anode masses.
- CDC delayed petroleum coke
- the novel baking method of the invention may be applied to all of the existing anode masses.
- the CDC and butts are sized to the desired particle size distribution, then this sized material is mixed with the binder, such as coal tar pitch or other suitable binders.
- the resulting mixture is then shaped to obtain the desired form and size, typically a block-like object. Shaping may be accomplished by pressing or vibrating the putty-like mass to form a green anode.
- the green anode block is then subjected to a baking step primarily to remove substantially all volatile materials from it and to render it more electrically conductive.
- the pit is charged with one or more green anodes and then these green anodes are surrounded, or packed, with the carbonaceous packing material in a manner to obtain a supportive, oxidation-resistant covering around the outer surfaces of the green anodes.
- a leveling layer of either RPC, CPC or a blend may be used between the pit bottom and the first anode block layer. In the event agglomeration is experienced in this leveling layer during baking, then in future leveling layers the blend ratio of GPC to RPC and/or CPC should be reduced.
- FIG. 2 An example of surrounding the green anodes with the packing agent is shown in Figure 2.
- the main reason for surrounding the outer surfaces of the green anodes with the carbonaceous packing material or agent is to prevent oxidation and distortion or warping of the green anodes but at the same time to provide a permeable avenue of escape for the volatilized compounds of the binder.
- These purposes are readily achieved by the method of the invention and at the same time significant energy saving is also realized through the use of green coke rather than calcined coke as a major constituent in the packing material .
- These aims could not be obtained through the use of the prior art open-pit, ring furnace anode baking method employing calcined petroleum coke.
- the packing material inventory in the pit is to be replenished from time to time and the replenishing agent contains a significant quantity of green petroleum coke or GPC, the balance being selected from calcined petroleum coke, recycled calcined coke, or mixtures of these.
- the GPC may be utilized to a level up to about 70%, this percentage being based on the total weight of the blend of packing material utilized in the baking of the green anodes.
- the quantity of GPC utilized in the method of the invention be maintained in the range of about 10% to about 60%, these percentages also being based on the weight of any GPC-containing blend employed as packing material in the green anode baking step.
- FIG. 3 shows the use of a blend containing GPC with other packing materials around the lateral faces of the green anode, while the top surface of the green anode is covered with a thick layer of calcined petroleum coke, recycled calcined coke or a mixture of these, without any GPC.
- the optimum quantity of GPC to be used in the blend is best established experimentally.
- the quantity utilized is largely influenced by the design and operating characteristics of the ring furnace, such as the draft in the furnace and the pitch content of the green anode. If the blend tends to agglomerate or stick to the anodes during the baking of the green anodes, or if anodes crack or distort significantly during baking, the level of GPC usage should be downwardly adjusted for subsequent applications of the blend. Notwithstanding the foregoing, the rate at which GPC can be utilized in most open-pit, ring furnaces and with most green anodes is up to about 70%, preferably within 10-60% by weight of the blend.
- the blend of GPC and RPC or fresh calcined petroleum coke is packed around the green anodes to a maximum height corresponding to approximately the top of the uppermost layer of the green anode stack to be baked.
- This arrangement is shown in Figure 3.
- the top surface of the top layer of green anodes is generally covered by either RPC, CPC or a mixture of these, taking into account that if CPC used in the packing is calcined fluid petroleum coke, then the RPC employed should have also been derived from CFC. Conversely, if the CPC is calcined delayed coke, then any RPC utilized in the packing should also be derived from CDC.
- calcined delayed petroleum coke In those open pit ring furnaces which use calcined delayed petroleum coke as packing material, the packing material utilized is commonly the same type of coke used to fabricate the green carbon bodies themselves.
- calcined delayed petroleum coke is characterized by two major factors, (a) a vanadium content which is generally less than about 400 ppm and (b) a sponge-like macroporosity. Due to these characteristics the calcined delayed coke is considered “high grade”. Delayed petroleum coke with a vanadium content in excess of about 400 ppm and/or having a macroporosity resembling those of spheres is considered "low grade".
- the low grade coke is seldom used as a filler material to make green carbon bodies, as the resultant prebaked carbon body exhibits an increased tendency to oxidize and/or crack at elevated temperatures. Consequently, manufacturers of carbon bodies have historically avoided the use of low grade coke as filler material in making green carbon bodies. Further, they have neither applied low grade delayed petroleum coke as open pit furnace packing material.
- the method of the invention allows the use of low grade green delayed petroleum coke to be used in the packing material blend, thereby providing additional advantages to the user.
- the anodes are subjected to the baking process.
- the ring furnace is operated so that the temperatures of the two fluewalls directly adjacent to a specific pit are elevated, over a number of days, from room temperature to an average temperature of about 1200°C to 1400°C.
- Heat is conducted from the flue walls through the packing material and into the green anode blocks thereby gradually raising the packing material and anode block temperatures over a time period, usually longer than one week, from ambient temperature to a desired target temperature.
- the target temperature is generally within the range from about 1100°C to 1200 °C and is measured at a representative point in the pit.
- the green anode and GPC volatiles generated during baking generally move laterally through the GPC blend to the fluewall, penetrate the fluewalls through pores and cracks in the refractory and are then burned and/or exhausted.
- the maximum temperature to which individual anodes rise varies depending on the specific locations of the anodes within the pit.
- the temperature distribution of the anodes and the packing material within a typical pit is part of the knowledge of the furnace operators. In most cases, the furnace is designed and operated so that all anodes in a typical pit are raised to at least 1050°C and the mean anode temperature is from about 1100°C to 1200°C. Since substantially all of the volatiles are removed from the GPC at temperatures between 250°C and 1000°C, wherever the GPC-containing blend is used in the baking pit, virtually complete removal of GPC volatiles is accomplished in the normal anode baking cycle where the minimum temperature of the pit is about 1050"C.
- the inventive method eliminates the need and associated costs for commercially calcining GPC for use in open-pit, ring baking furnaces as green anode packing material. Also, since in the method of the invention a low grade GPC may be utilized in the packing material, it inherently provides a reduced material cost basis.
- the time required for baking the green anodes in conventional open-pit, ring furnaces generally depends on the design of the ring furnace, for example its size and the flue arrangement, as well as on the mass of green anodes to be baked.
- the length of time required for baking anodes in the method of the invention, employing GPC in the packing material is about the same as the time required in the conventional, prior art green anode baking using open-pit, ring furnaces.
- a blend 4 of particulate packing material containing an approximate 50:50 by weight mixture of GPC and RPC, was then prepared and this blend 4 was introduced into space 2 provided between vertical refractory brick flue walls 4 and the anode stack 1. Packing was accomplished in such a manner as to provide a dense layer between the walls and the anode stack.
- the width of space 2 between the vertical refractory brick flue walls 3 and the green anode stack 1 was about 4 inches. With respect to Figure 3(a), the width of space 2b between the vertical refractory brick head wall 3b and the green anode stack 1 was about 8 inches.
- Blend 4 was applied to such a height in the pit until it was approximately level with the top horizontal surface of anode stack 1 without covering the top horizontal surface of anode stack 1.
- RPC was then placed on the top of anode stack 1 and also on the top surfaces of blend 4.
- the baking process of the anodes commenced.
- the representative temperature of the pit was slowly elevated to about 1100°C and the baking process was complete after about seven days. Subsequently, the section of baking pits was cooled and the RPC, blend 4 and the prebaked anodes were then removed from the pits.
- the prebaked anodes were tested and no abnormalities were observed in either the physical properties or in the performance of the anodes.
- the blend 4, utilized as packing material in the baking process acted like the conventionally used RPC or CPC and during the baking step, the GPC content of blend 4 had been substantially freed of its volatile content and the material had been successfully converted to a carbonaceous agent ready to be used as RPC in future baking operations.
- composition and types of the blends used in the method of the invention as packing materials can be varied within wide limits and the above example is considered as illustrative only without intending to limit the scope of the invention to the specific conditions described.
- the extent and scope of the present invention shall only be limited by the scope of the appended claims.
Abstract
Description
Claims
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1997/009714 WO1998055426A1 (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
BR9714742-7A BR9714742A (en) | 1997-06-04 | 1997-06-04 | Production process of thermally treated carbon bodies in peripheral pipeline open pit furnaces |
CA002291272A CA2291272A1 (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
EP97928845A EP0984907A1 (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
NZ500930A NZ500930A (en) | 1997-06-04 | 1997-06-04 | Heat treatment of carbon anodes in open pit with packing including green petroleum coke |
AU33006/97A AU3300697A (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
NO995856A NO995856L (en) | 1997-06-04 | 1999-11-30 | Process for the preparation of heat-treated carbon bodies |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1997/009714 WO1998055426A1 (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998055426A1 true WO1998055426A1 (en) | 1998-12-10 |
Family
ID=22261024
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1997/009714 WO1998055426A1 (en) | 1997-06-04 | 1997-06-04 | Production of heat-treated carbon bodies |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0984907A1 (en) |
AU (1) | AU3300697A (en) |
CA (1) | CA2291272A1 (en) |
WO (1) | WO1998055426A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2013187959A1 (en) | 2012-06-15 | 2013-12-19 | Fluor Technologies Corporation | Carbon baking heat recovery ring furnace |
WO2013187960A1 (en) | 2012-06-15 | 2013-12-19 | Fluor Technologies Corporation | Carbon baking oxygen preheat and heat recovery firing system |
CN112745123A (en) * | 2021-01-25 | 2021-05-04 | 焦作钧菲津材科技有限公司 | Preparation method of carbon material |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3975144A (en) * | 1975-03-11 | 1976-08-17 | Reynolds Metals Company | Cathode baking system |
US3998933A (en) * | 1974-09-16 | 1976-12-21 | Union Carbide Corporation | Coke particle filter for pitch fumes to form electrodes |
-
1997
- 1997-06-04 AU AU33006/97A patent/AU3300697A/en not_active Abandoned
- 1997-06-04 CA CA002291272A patent/CA2291272A1/en not_active Abandoned
- 1997-06-04 EP EP97928845A patent/EP0984907A1/en not_active Withdrawn
- 1997-06-04 WO PCT/US1997/009714 patent/WO1998055426A1/en not_active Application Discontinuation
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3998933A (en) * | 1974-09-16 | 1976-12-21 | Union Carbide Corporation | Coke particle filter for pitch fumes to form electrodes |
US3975144A (en) * | 1975-03-11 | 1976-08-17 | Reynolds Metals Company | Cathode baking system |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2013187959A1 (en) | 2012-06-15 | 2013-12-19 | Fluor Technologies Corporation | Carbon baking heat recovery ring furnace |
WO2013187960A1 (en) | 2012-06-15 | 2013-12-19 | Fluor Technologies Corporation | Carbon baking oxygen preheat and heat recovery firing system |
CN112745123A (en) * | 2021-01-25 | 2021-05-04 | 焦作钧菲津材科技有限公司 | Preparation method of carbon material |
Also Published As
Publication number | Publication date |
---|---|
AU3300697A (en) | 1998-12-21 |
EP0984907A1 (en) | 2000-03-15 |
CA2291272A1 (en) | 1998-12-10 |
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