US3578069A - Apparatus for firing carbon-containing products - Google Patents

Apparatus for firing carbon-containing products Download PDF

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Publication number
US3578069A
US3578069A US797738A US3578069DA US3578069A US 3578069 A US3578069 A US 3578069A US 797738 A US797738 A US 797738A US 3578069D A US3578069D A US 3578069DA US 3578069 A US3578069 A US 3578069A
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United States
Prior art keywords
furnace
products
temperature
installation
product
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Expired - Lifetime
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US797738A
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English (en)
Inventor
Paul Morel
Jean-Pierre Givry
Philippe Voisin
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Pechiney SA
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Pechiney SA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/06—Electrodes
    • H05B7/08—Electrodes non-consumable
    • H05B7/085—Electrodes non-consumable mainly consisting of carbon
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • 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

  • the method of heat transmission varies during the firing cycle. While at low temperature, heat transmission is effected primarily by convection. As the temperature rises transmission of heat by radiation occurs in increasing amounts until radiation becomes the predominate means of transmission during the cycle when the product to be fired reaches maximum temperature. On the other hand, the hot gases give up heat all along their path of travel, since, at any given instant, the partition walls will be at a lower temperature because of their having been swept over by gases which have traveled through a longer path after entry into the furnace.
  • the firing cycle is shifted from one chamber to another, with one chamber being removed from the cycle for purposes of loading and unloading, the admission of fresh air occurring at the inlet of the following chamber while the evacuation of burnt gases is effected from the outlet of the preceding chamber.
  • the first group of chambers is undergoing cooling with the fresh air introduced being progressively heated, in the next group of chambers equipped with burners, the baking is being completed, and with the last group of chambers being heated by the combustion gases from the chambers upon completion of the firing.
  • the gases issuing from the latter chambers are exhausted to the chimney from the outlet of the chamber preceding the one removed from the cycle.
  • the described arrangement of furnaces lacks flexibility in that any attempt to modify the temperature in any one chamber affects all of the others.
  • the fires are difficult to control with the result that such furnace arrangement is difficult to use for firing crude products having a high pitch content for graphetization.
  • the cycles are long, such as about 20 days, and, in addition, the products that are produced have very high porosity and excessive amounts of fissures.
  • the combustion air is passed therethrough in countercurrent flow with the products to be treated, the latter of which are loaded on trucks of refractory material and embedded in granulated coke or anthracite.
  • Burners are located in the central region of the furnace.
  • the products first engage the hot gases being discharged from the furnace before passing in front of the burners during which they are heated to maximum temperature and after which they travel through a cooling zone in heat-exchange relation with the fresh gases entering the furnace.
  • the radiation from the walls of the furnace obviously contribute to the heat exchange.
  • Such furnaces have disadvantages which arise from the presence of large amounts of inert refractory material such as the trucks and filling material which consume heat and which retard heat transmission thereby to limit the rate of the rise and fall of temperature. Further, at operating temperature of l,30 O to l,350 C., the refractory walls and trucks have relatively short life and require frequent replacement. In addition, the cost for loading and unloading of the trucks is excessive.
  • the products to be fired or baked, and embedded in a suitable filler material are stacked between the current supply heads.
  • the filling material not only protects the product from air oxidation and insulates the products from heat, but it provides resistance at the start while the product to be treated is electrically insulating and becomes conductive at temperatures of about 650 C.
  • Such furnaces are subject to serious disadvantages due to the difficulty of obtaining homogeneous distribution of product and filling material. This results in nonuniformity in electrical current with corresponding heterogeneous heat generation and temperature distribution. This effect is aggravated by the fact that the electrical conductivity of the product changes quickly from a very low value to a high value as the temperature passes through the range of 6000 to 650 C., thereby further to increase the concentration of current in superheated portions. Efforts have been made to obviate this disadvantage by limiting current density to permit heat conductivity to take effect for leveling out the temperature. The result is a longer firing period and decreased yield without material reduction in variation and quality of product secured. Again, a large mass of filling material is used with corresponding heat loss and increased costs for handling.
  • FIG. 1 is a diagrammatic view of an installation for carrying out the process of this invention.
  • FIG. 2 is a diagrammatic sectional view of a tunnel furnace representing the first element in the installation of FIG. 1.
  • the concept of this invention resides in the treatment of the product to be baked in the presence of a gas which is nonreactive to the carbon-containing product, with the treatment being subdivided into four phases, namely, a heating phase, a phase for release and combustion of volatiles, and, finally, a heating phase and a cooling phase.
  • the installation employed in the practice of this invention comprises a tunnel furnace having a cooling means and which is subdivided into two successive zones which provide the first two of the phases with the gas and the products to be fired being passed therethrough in countercurrent flow.
  • the tunnel furnace is followed by an airtight chamber equipped with electrical heating means for the generation of heat from within the interior of the product to be fired, such as by induction heating, with clips applied to the product for the passage of electrical current therethrough.
  • Pipes are provided at the junction between the zones of the tunnel furnace for connection to exhaust fans for exhausting the gases to a chimney and other pipes are provided toward the free end of the zone for the introduction of fresh air.
  • the carbon-containing products are obtained by firing a crude product formed of a mixture of coke and binder, and extruded or molded either under high pressure, such as up to 350 bars, or by vibration, or combinations thereof.
  • the product is characterized by internal stresses. Although the product experiences an expansion due to the expansion of the occluded air on emission from the extrusion die or release from a mold, mechanical stresses exist due to the pressure of the occluded air and the pressure gradient through the mass.
  • the binder undergoes a thermal evolution which causes it to pass through the conventional phases hereinafter referred to, the approximate limiting temperatures of each phase corresponding to a coil tar.
  • a nonevolutionary plastic phase covering the range of 100 to 250 C., the softened binder becomes increasingly more fluid but without the release of volatile materials.
  • the product becomes completely plastic and permits residual stresses, resulting from the shaping operations, to be released. in this phase, it is possible for cracking to occur along the fragile surfaces established during the extrusion or molding by a detachment of the stratified zones due to the pressure exerted by the occluded gases in the impermeable product.
  • a swelling phase covering the range of 250 to 450 C., the main portion of the volatile materials are released, accompanied by an expansion of the plastic mass of the product. This expansion is not accompanied by the formation of fissures or cracks because of the plasticity of the product. It is during this phase that the future macroporosity of the baked product is established.
  • resolidification phase In a resolidification phase, covering the range of 480 to 500 C., resolidification of the binder occurs very suddenly.
  • the resolidification temperature depends somewhat on the speed at which the temperature rises.
  • the temperature limits which are indicated correspond to increase in temperature at a rate greater than C. per hour.
  • a solid phase covering the range above 500 C., corresponds to the further treatment of the product which undergoes an evolution of its mechanical characteristics. These latter, which are slight at the start, reach their maximum at a temperature which, for pitch, is in the region of 750 C., after which the mechanical characteristics remain substantially constant.
  • the dangers of forming cracks in the product decrease as the temperature increases. They are practically nonexistent when the mass is heated without their being established over a wide temperature gradient.
  • the product to be baked can have a considerable volume.
  • the crude product does have a low thermal conductivity so that, if the heating takes place from the outside, a temperature gradient will exist through the cross section such that several baking phases may be present simultaneously in a single product.
  • the product can withstand fairly high stresses.
  • a critical zone still exists at a temperature corresponding to the coefficient of maximum contraction, i.e., about 750 C. in the case of pitch.
  • the installation shown in H6. 1 comprises a tunnel furnace subdivided into two zones 1 and 2.
  • the first zone I referred to as the heating zone
  • the products pass from the temperature I, to the temperature t and the gases passed from the temperature T to the temperature T
  • the second zone 2 referred to as the zone for release and combustion of the volatile materials
  • the products pass from the temperature 2 to the temperature i and the gases from the temperature T to the temperature T
  • the installation includes an enclosed chamber 30 provided with electrical heating means 32 and in which the products are brought from the temperature t to the temperature t., and a coding chamber 40 in which the products are cooled from a temperature to a temperature t
  • the tunnel furnace 10 receives fresh air through its outlet 13.
  • the air is immediately heated by the product undergoing baking and by the burners 21 to the temperature T;,.
  • a zone is thus established in which the temperature 1 of the product undergoing baking remains substantially constant. This enables the product to be homogenized before it enters the chamber 30.
  • the gases which exhaust from the tunnel furnace at the inlet end, at a temperature T, are directed in part through line 14 to a chimney ll and returned in part through line 15 to the furnace for the introduction through pipes 12 in regions situated on either side of the junction between the zones 1 and 2.
  • Cooling in chamber 40 can be effected by a water spray or by circulating an inert cool gas therethrough.
  • the travel of the products to be baked through the tunnel furnace can be effected by any known or conventional means, such as a continuous belt, trucks operating on a roller track and thrust means, or any other equivalent means capable of withstanding the temperature of the furnace.
  • the preheating zone 1 operates as an undercurrent-heat exchanger, while the combustion zone 2 operates as a reactor in which the energysource is composed partly of the heat contributed by the combustion of the volatile materials released from the product and bumed with the supply of air 12 and partly by the heat contributed by the burners 21.
  • the hydrogen takes up oxygen upon combustion to yield steam
  • the carbon takes up oxygen upon combustion to yield carbon monoxide thereby to provide nonreactive or a reducing hot gaseous atmosphere.
  • the presence of certain amounts of carbon dioxide does not present any inconvenience, especially in view of the inhibiting effect of the carbon monoxide.
  • the electrical heating chamber 30 insures a uniform rise in temperature through the cross section of the products up to about 1,200" C. in about 20 minutes.
  • a current density of at least amperes per square centimeter is employed, in the case of heating by the Joule effect.
  • heating by induction is to be preferred.
  • the products travel through the tunnel furnace 10 in the direction of the arrow 8 from the preheating zone 1 toward the combustion zone 2. From the outlet of the tunnel furnace, the products are introduced into the chamber 30 representing the electrical heating zone 3, and then into the cooling arrangement 40 which represents the cooling zone 4.
  • the hot gases circulate in the opposite direction through the tunnel furnace, as indicated by the arrow 9.
  • the tunnel fumace diagrammatically illustrated in FIG. 2 is identical with that of FIG. 1, but the circuit through which the gases travel outside the furnace 10 has been modified.
  • the gases exhausted from the furnace at the temperature T pass first to a fan 13, from which an amount of gas equal to the amount added by the combustion of the volatile products in zone 2 plus the amount of fresh air admitted to the inlet of the furnace, is directed to the chimney l1.
  • Excess gases are directed into the region on either side of the junction between zones v1 and 2, preferably after being reheated to a temperature of T in apreheater 14. In certain instances, reheating is unnecessary or might even be replaced by cooling. Valves 1S permit control of the distribution of the gases reintroduced into the furnace.
  • the electric heating chamber 30 has a length of 0.50 meters and the cooling arrangement 40 is formed of a fluidtight tank having a length of 0.5 meters and is provided with a water-sprinkling device.
  • the crude products introduced are formed of a mixture of petroleum coke with 1-7 percent coal tar, molded under a pressure of 325 bars.
  • the described furnace is intended for firing or baking three electrodes per hour in which the electrodes have a dimension of 40 83 50 centimeters, representing a total mass of 695 kg.
  • An installation for the firing or baking of carbon-containing products through four phases comprising heating, release and combustion of the volatile materials, final heating and cooling, with the heating taking place in a nonreactive atmo'sphere, said installation comprising a tunnel furnace having an outlet end and an inlet end and in which the tunnel furnace is divided into two zones corresponding to the first two of the phases, means for passage of the products and a nonreactive gas through the tunnel furnace in opposite directions, a fluidtight chamber provided with electrical means for releasing heat from the interior of the products to be fired, including members applied to the product for causing an electrical current to pass therein, and a cooling chamber after the electrical heating chamber, said products passing from the outlet of the tunnel furnace to the heating chamber and then to the cooling chamber.
  • An installation as claimed in claim 3 which includes means for diverting a part of the gas exhausted from the inlet end of the tunnel furnace to a chimney.
  • An installation as claimed in claim 1 which includes burners in the tunnel furnace adjacent the outlet end portion for combustion of air introduced into the furnace to heat the products and to inert the gas.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Tunnel Furnaces (AREA)
  • Furnace Details (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Chairs Characterized By Structure (AREA)
US797738A 1968-02-19 1969-02-10 Apparatus for firing carbon-containing products Expired - Lifetime US3578069A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR140302 1968-02-19

Publications (1)

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US3578069A true US3578069A (en) 1971-05-11

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US (1) US3578069A (de)
JP (1) JPS4810718B1 (de)
AT (1) AT289034B (de)
BE (1) BE728645A (de)
CA (1) CA936356A (de)
CH (1) CH495301A (de)
CS (1) CS177011B2 (de)
DE (1) DE1907984B2 (de)
ES (1) ES363768A1 (de)
FR (1) FR1573937A (de)
GB (1) GB1263527A (de)
IS (1) IS856B6 (de)
LU (1) LU58019A1 (de)
NL (1) NL6902551A (de)
NO (1) NO127682B (de)
OA (1) OA02998A (de)
SE (1) SE347956B (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4020273A (en) * 1975-11-26 1977-04-26 Celanese Corporation Vertical pyrolysis furnace for use in the production of carbon fibers
US4025610A (en) * 1973-12-15 1977-05-24 Nippon Kokan Kabushiki Kaisha Method and apparatus for denitrifying coke
EP0103130A2 (de) * 1982-08-18 1984-03-21 ALUSUISSE ITALIA S.p.A. Herstellungsverfahren von kohlenhaltigen Blöcken in einem Tunneltyp-Ofen
EP0172791A2 (de) * 1984-07-04 1986-02-26 ELETTROCARBONIUM S.p.A. Bauteil zur Wärmerückgewinnung der Abgase von Öfen mit beweglichen Herden zum Brennen und Tempern von kohlenstoffhaltigen Gegenständen
EP0176036A2 (de) * 1984-09-28 1986-04-02 ALUSUISSE ITALIA S.p.A. Verfahren zur Herstellung kohlenstoffhaltiger Körper
EP0186734A2 (de) * 1984-09-28 1986-07-09 ALUSUISSE ITALIA S.p.A. Verfahren zur Herstellung kohlenstoffhaltiger Körper

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51121013A (en) * 1975-04-16 1976-10-22 Shinagawa Refractories Co Method and apparatus for heatttreating carbon mold articles
US4417872A (en) * 1982-02-01 1983-11-29 Energy Research Corporation Heat treating
JPS6393847U (de) * 1986-12-05 1988-06-17

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2621218A (en) * 1951-06-06 1952-12-09 Dow Chemical Co Electric graphitizing furnace
US3474544A (en) * 1967-07-07 1969-10-28 Coe Mfg Co The Veneer dryer with plural treating zones

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2621218A (en) * 1951-06-06 1952-12-09 Dow Chemical Co Electric graphitizing furnace
US3474544A (en) * 1967-07-07 1969-10-28 Coe Mfg Co The Veneer dryer with plural treating zones

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025610A (en) * 1973-12-15 1977-05-24 Nippon Kokan Kabushiki Kaisha Method and apparatus for denitrifying coke
US4020273A (en) * 1975-11-26 1977-04-26 Celanese Corporation Vertical pyrolysis furnace for use in the production of carbon fibers
EP0103130A2 (de) * 1982-08-18 1984-03-21 ALUSUISSE ITALIA S.p.A. Herstellungsverfahren von kohlenhaltigen Blöcken in einem Tunneltyp-Ofen
EP0103130A3 (de) * 1982-08-18 1986-05-14 ALUSUISSE ITALIA S.p.A. Herstellungsverfahren von kohlenhaltigen Blöcken in einem Tunneltyp-Ofen
EP0172791A2 (de) * 1984-07-04 1986-02-26 ELETTROCARBONIUM S.p.A. Bauteil zur Wärmerückgewinnung der Abgase von Öfen mit beweglichen Herden zum Brennen und Tempern von kohlenstoffhaltigen Gegenständen
EP0172791A3 (en) * 1984-07-04 1987-05-13 Elettrocarbonium S.P.A. A unit for regenerating the heat produced by exhaust gases in movable hearth furnaces used for baking or rebaking carbonaceous materials
EP0176036A2 (de) * 1984-09-28 1986-04-02 ALUSUISSE ITALIA S.p.A. Verfahren zur Herstellung kohlenstoffhaltiger Körper
EP0186734A2 (de) * 1984-09-28 1986-07-09 ALUSUISSE ITALIA S.p.A. Verfahren zur Herstellung kohlenstoffhaltiger Körper
EP0176036A3 (en) * 1984-09-28 1987-01-21 Alusuisse Italia S.P.A. Method of producing carbonaceous bodies
EP0186734A3 (en) * 1984-09-28 1987-01-28 Alusuisse Italia S.P.A. Method of producing carbonaceous bodies

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Publication number Publication date
SE347956B (de) 1972-08-21
DE1907984A1 (de) 1970-03-05
GB1263527A (en) 1972-02-09
BE728645A (de) 1969-08-19
NO127682B (de) 1973-07-30
CA936356A (en) 1973-11-06
LU58019A1 (de) 1969-09-18
IS1828A7 (is) 1969-08-20
OA02998A (fr) 1970-12-15
CH495301A (fr) 1970-08-31
DE1907984B2 (de) 1970-03-05
CS177011B2 (de) 1977-07-29
AT289034B (de) 1971-03-25
ES363768A1 (es) 1971-03-16
IS856B6 (is) 1974-05-21
FR1573937A (de) 1969-07-11
JPS4810718B1 (de) 1973-04-06
NL6902551A (de) 1969-08-21

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