US3797993A - Tunnel kiln - Google Patents

Tunnel kiln Download PDF

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Publication number
US3797993A
US3797993A US00265304A US3797993DA US3797993A US 3797993 A US3797993 A US 3797993A US 00265304 A US00265304 A US 00265304A US 3797993D A US3797993D A US 3797993DA US 3797993 A US3797993 A US 3797993A
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United States
Prior art keywords
hollow block
block elements
elements
tunnel
kiln
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00265304A
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English (en)
Inventor
K Heldt
H Lappe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DEUTSCHE GOLD und SILBER SCHEIDEANSTALT DT
Evonik Operations GmbH
Original Assignee
Degussa GmbH
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Filing date
Publication date
Application filed by Degussa GmbH filed Critical Degussa GmbH
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Publication of US3797993A publication Critical patent/US3797993A/en
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Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
    • F27B9/20—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path
    • F27B9/24—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path being carried by a conveyor
    • F27B9/2461—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment the charge moving in a substantially straight path being carried by a conveyor the charge being suspended from the conveyor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/06—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated
    • F27B9/08—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated heated through chamber walls
    • F27B9/082—Muffle furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D1/00—Casings; Linings; Walls; Roofs
    • F27D1/04—Casings; Linings; Walls; Roofs characterised by the form, e.g. shape of the bricks or blocks used

Definitions

  • the invention relates to a flame heated tunnel furnace or kiln for the continuous firing or sintering of elongated ceramic molded articles suspended on an arch cover slidable over the upper shaft opening of the furnace.
  • a special problem in the heat treatment of elongated molded articles, such as tubes, bars or strips is presented in that whenever they are moved in a horizontal position through such kilns, they are inclined to distortion and bending even when they are supported in numerous places.
  • These molded articles are introduced into the kiln in a compressed or cast state for strengthening by means of sintering.
  • the strength of such articles at the same time essentially is based on their content of organic and inorganic binders.
  • the strengthening of the articles can be connected with a considerable shrinkage, the values of shrinkage amounting to between 5 and 25 percent of the original dimensions depending on the conditions of production and sintering.
  • the object of the invention is to create a flame heated tunnel kiln (or tunnel furnace) which does not have the disadvantages described and which as a result makes possible an operation free of disturbances while avoiding the accumulation of waste.
  • a flame heated tunnel kiln for the continuous firing or sintering of elongated ceramic molded articles arranged suspended on an arched cover slidable across the upper shaft opening of the kiln, which kiln is characterized by side walls separating the tunnel kiln in the area of the-firing zone from the flame zone.
  • the side walls are made of refractory hollow block elements constructed with thin walls toward the firing zone and open toward the fiame zone, the shape and arrangement of which prevent relative movements with reference to one another transversely to the kiln axis.
  • the burners are directed toward the openings of the hollow block elements.
  • I-Iot gas exhausts are removed by suction below a flow channel for cooling air bounding the upper tunnel chamber and opening toward it, whereby there is provided a gap for the inflow of outside air between the arched cover and the outside contour of the .flow channel for the cooling air which is adjusted to it.
  • the hollow block elements serving to form the side walls can be made of the conventional refractory materials, such as for example chamotte, sillimanite and sin tered corundum.
  • the side walls shut off the burner space from the actual kiln chamber. The flames or waste gases therefore cannot directly strike the material that is to be fired, as a result of which there is avoided any mechanical influencing of the material to be fired which is sensitive in its untreated state by strongly eddying flame gases.
  • the thickness of the side walls is dimensioned in such a way that a good heat transfer is maintained. Generally speaking, in the case of manufacture of hollow block elements from ceramic materials, material thicknesses between and 40 mm will be needed.
  • hollow block elements can be assembled beside one another or on top of one another into a connected wall, with the use of a fire resistant mortar adapted to the sintering temperature, it is also effective to stack the elements only loosely on top of one another because, as a result of that, they retain a free movability during thermal expansion.
  • the hollow block elements preferably are open at their top and undersides. In this way it will be possible for the flame gases, flowing into the lower wall element from the burners disposed, for example, in the lower part of the kiln, to flow upwards within a tower of elements located on top of one another and thus a temperature balance results between the lower and the upperparts of the kiln.
  • a considerable increase in the stability of the wall of the elements will be achieved by using elements, the shape and arrangement of which will prevent relative movements with reference to one another and especially in the direction transversely to the longitudinal axis of the kiln.
  • a particularly effective form of the invention provides for the assembly of hollow block elements with a wedge-shaped cross section within a horizontal row of elements in alternating head/tail orientation. Slippage to the inside toward the kiln space and to the outside toward the burner space will be reliably prevented by these wedge-shaped wall elements pointing in the opposite directions.
  • a further variation of the invention provides hollow block elements succeeding each other within a horizontal row of elements, which engage one another at their lateral contact surfaces in meshing or tongue and groove fashion.
  • every second hollow block element disposed within a horizontal row of elements also can at least partially overlap the adjacent elements with one of its overhung surfaces.
  • the burners leading to the hollow block elements opposite the apertures are adjusted best slantingly, preferably slanting upwards against the direction of movement of the material that is to be tired. This is advantageous in that a natural temperature gradient will appear as a result of the cooling waste gases, so'that the material to be fired is heated slowly.
  • the waste gases as is customary, are suctioned off by way of a collecting channel and are used mostly to preheat the combustion air.
  • Another object of theiinvention is to avoid the overheating of the arched cover closing the firing or sintering zone of the tunnel kiln on top. This object is achieved by suctioning off the hot waste gases prior to their reaching the arched cover. In the case of stacked but not cemented connection of wall elements, the hot gases will penetrate in small quantity through its joints, however, by sucking in cold air at the same time through the gap between the cover and the discharge channel for cooling air connected via an aperture with the upper tunnel space and being under vacuum as a result of an induced draught.
  • the discharge channel for the cooling air consists of elements made of refractory material connected at least at one end of the formed channel with an exhaust and assembled as a horizontal row, provided toward the tunnel space with at least one aperture and open on both sides in the longitudinal direction of the kiln.
  • the gap through which the cooling air is to flow from the outside can be connected with a source for compressed air.
  • FIG. 1 is a vertical sectional view through the firing zone of a tunnel kiln according to the invention
  • FIG. 2 is an enlarged fragmentary sectional view taken along the line 2 2 of FIG. 1;
  • FIG. 3 is an enlarged fragmentary sectional view taken along line 3 3 of FIG. 1;
  • FIG. 4 is a partial fragmentary sectional view similar to FIG. 2 showing another form of the hollow elements generally in the shape of a wedge;
  • FIG. 5 is a view similar to FIG. 4 of still another form of the hollow elements.
  • FIG. 6 is another view similar to FIG. 4 of still another form of the hollow elements.
  • the reference number 1 designates, generally, the kiln which includes a housing defined by a surrounding brick lining or wall 2.
  • the latter encloses a flame zone 3 which extends into a multiplicity of open ended hollow block elements 4, made of refractory ceramic raw materials, stacked one on top of the other to form a pair of partitions or side walls.
  • the flames are produced by burners 5.
  • Each of the hollow block elements 4 has an opening 6 and a wall 7 acting as a heat radiating surface.
  • the walls 7 provided by the elements 4 separate the flame zone 3 within the housing from a firing zone 8.
  • the cross section of wall 7 is dimensioned smaller than that of the remaining walls of the hollow body. These remaining walls are dimensioned in such a way that the lowest elements of the wall are able to support the weight of the elements piled on them.
  • wall 7 is 15 mm thick while the statically bearing walls have a thickness of 35 mm.
  • the discharge channel 11 for the cooling air constitutes the upper closure of the firing chamber.
  • the discharge channel 11 in the embodiment shown consists of elements made of refractory material formed and placed one beside the other in a horizontal row and provided with an aperture 12 to the tunnel chamber. One end of the channel is connected with a suction and the opposite end of the channel is closed.
  • the outside contour of the channel elements conforms to the inside contour of the arched cover 13 but is spaced at a distance relative to it to form a gap.
  • the arched cover is provided with an outside'insulation 14 which consists of individual meshing parts about 1 m long, disposed slidably by means of rollers running on rails on the uppermost side of the kiln in the direction of the tunnel chamber or firing zone. It closes the firing chamber over the entire length of the kiln. It serves as a so-called kiln car and it carries the material 15 which is to be treated and which is suspended downwards into the firing chamber.
  • the supports for the material that is to be treated are attached to the arch lid outside the heating chamber (not shown). They also can be attached in the heating chamber itself, i.e., on the underside of the arch lid.
  • the wall of hollow block elements 4 consists, according to FIG. 2, of elements of a generally wedge-shaped cross section, which have been joined inside a horizontal row of elements in an alternatinghead/tail orientation.
  • FIG. 3 shows the arrangement of the suction tubes for the hot gas above the hollow block elements.
  • each second hollow block element disposed within a horizontal row of elements partly overlaps with one of its contacting surfaces the adjacent elements, and thus ensures the total formation against displacement.
  • FIGS. 5 and 6 finally relate to hollow block elements 41 and 42 constructed to mesh with one-another, of which the FIG. 5 arrangement additionally shows the overlapping effect.
  • FIG. 6 shows a tongue and groove mesh.
  • the tunnel kiln 1 operates in the following manner;
  • the flame gases flowing from the burners 5 fill the flame zone 3, penetrating through the opening 6 into the hollow block element 4 and thereby heating the thin walls 7 of said elements.
  • the latter radiate the thermal energy onto the material 15 which is to be treated and which is guided slowly through the firing zone 8 suspended from the arch lid 13.
  • the hot gases diffused through the piled up wall, are removed from the kiln for the greater part by way of hot gas suctions.
  • the discharge channel 11 for the cooling air is connected with a suction fan and sucks in fresh air from the outside via aperture 12 through the gas between the kiln and the kiln cover 13. At the same time the latter is cooled effectively.
  • the tunnel kiln according to the invention has numerous advantages as compared to known shaft kilns operated discontinuously, of which there can be mentioned particularly:
  • a flame heated tunnel furnace for continuously firing or sintering elongated ceramic molded objects suspended on a movable arched cover over an upper shaft opening of the furnace
  • the improvement in combination therewith which comprises side walls dividing the furnace into a flame zone and a firing zone, said side walls including thin-walled fire resistant hollow block elements joined to one another and having a form and arrangement to prevent relative movement of each transversely to the furnace axis, openings in said hollow block elements forming part of said flame zone, burners in said flame zone, hot gas removal means for said firing zone adjacent the upper portion of said side walls, and a cool air flow channel means above said hot gas removal means defining with said arched cover gap means for the inflow of outer air.
  • a tunnel furnace according to claim 1 wherein said hollow block elements are arranged in a horizontal series one after the other and are interlocked on their alternating lateral surface of contact in tongue and groove fashion.
  • a tunnel furnace according to claim 1 wherein said hollow block elements are arranged in a horizontal series of elements, said elements having a free lying surface, every other block of said series having at least its free lying surface partially overlapping the next element.
  • hollow block elements include a plurality of horizontal series of hollow block elements, said hot gas removal means being disposed over the hollow block elements of the uppermost horizontal element series, said removal means comprising pipes joined to a collection conduit.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Tunnel Furnaces (AREA)
  • Furnace Details (AREA)
US00265304A 1971-07-07 1972-06-22 Tunnel kiln Expired - Lifetime US3797993A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2133762A DE2133762C3 (de) 1971-07-07 1971-07-07 Tunnelofen zum kontinuierlichen Brennen bzw. Sintern länglicher keramischer Formkörper

Publications (1)

Publication Number Publication Date
US3797993A true US3797993A (en) 1974-03-19

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US00265304A Expired - Lifetime US3797993A (en) 1971-07-07 1972-06-22 Tunnel kiln

Country Status (7)

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US (1) US3797993A (enExample)
JP (1) JPS5229764B1 (enExample)
DD (1) DD97050A5 (enExample)
DE (1) DE2133762C3 (enExample)
FR (1) FR2145152A5 (enExample)
GB (1) GB1395067A (enExample)
IT (1) IT954795B (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060082033A1 (en) * 1999-02-04 2006-04-20 Holger Hauptmann Process for the dimensionally-true sintering of ceramics
CN110657667A (zh) * 2019-09-11 2020-01-07 山西太钢工程技术有限公司 连续式加热炉、用于连续式加热炉的吊挂墙及其制造方法
US10945821B2 (en) 2015-08-03 2021-03-16 Amann Girrbach Ag Sintered blank for producing a dental prosthesis

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107505353A (zh) * 2017-09-27 2017-12-22 江苏建筑职业技术学院 一种寒区短隧道入口降温测定模型及其测试方法
CN116608695A (zh) * 2023-03-29 2023-08-18 鞍钢集团朝阳钢铁有限公司 一种烧结过程风箱自动控制的方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1039101A (en) * 1911-02-01 1912-09-24 Corliss Carbon Company Furnace.
US1611318A (en) * 1925-04-29 1926-12-21 Twin City Forge & Foundry Comp Furnace for heating tie-plate flanges

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1039101A (en) * 1911-02-01 1912-09-24 Corliss Carbon Company Furnace.
US1611318A (en) * 1925-04-29 1926-12-21 Twin City Forge & Foundry Comp Furnace for heating tie-plate flanges

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060082033A1 (en) * 1999-02-04 2006-04-20 Holger Hauptmann Process for the dimensionally-true sintering of ceramics
US10945821B2 (en) 2015-08-03 2021-03-16 Amann Girrbach Ag Sintered blank for producing a dental prosthesis
CN110657667A (zh) * 2019-09-11 2020-01-07 山西太钢工程技术有限公司 连续式加热炉、用于连续式加热炉的吊挂墙及其制造方法

Also Published As

Publication number Publication date
DE2133762C3 (de) 1975-10-23
FR2145152A5 (enExample) 1973-02-16
DE2133762B2 (de) 1975-03-13
IT954795B (it) 1973-09-15
DD97050A5 (enExample) 1973-04-12
GB1395067A (en) 1975-05-21
DE2133762A1 (de) 1973-01-25
JPS5229764B1 (enExample) 1977-08-04

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