EP0790474A1 - Toit refroidit pour fours ou poches à arc - Google Patents

Toit refroidit pour fours ou poches à arc Download PDF

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Publication number
EP0790474A1
EP0790474A1 EP97101864A EP97101864A EP0790474A1 EP 0790474 A1 EP0790474 A1 EP 0790474A1 EP 97101864 A EP97101864 A EP 97101864A EP 97101864 A EP97101864 A EP 97101864A EP 0790474 A1 EP0790474 A1 EP 0790474A1
Authority
EP
European Patent Office
Prior art keywords
roof
cooled roof
cooled
section
conduit
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.)
Withdrawn
Application number
EP97101864A
Other languages
German (de)
English (en)
Inventor
Milorad Pavlicevic
Gianni Gensini
Angelico Della Negra
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.)
Danieli and C Officine Meccaniche SpA
Original Assignee
Danieli and C Officine Meccaniche SpA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Danieli and C Officine Meccaniche SpA filed Critical Danieli and C Officine Meccaniche SpA
Publication of EP0790474A1 publication Critical patent/EP0790474A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F27D1/18—Door frames; Doors, lids, removable covers
    • F27D1/1808—Removable covers
    • F27D1/1816—Removable covers specially adapted for arc 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
    • F27D1/14—Supports for linings
    • F27D1/141—Anchors therefor

Definitions

  • This invention concerns a cooled roof for electric arc furnaces and for ladle furnaces as set forth in the main claim.
  • the cooled roof according to the invention is applied as a cover in electric arc furnaces and in ladle furnaces used to melt metallic alloys, both ferrous and non-ferrous.
  • Electric arc furnaces are composed of a sheet cylinder lined on the inside at the lower part with refractory material and closed at the upper part by a roof.
  • the roof includes a water cooling system.
  • the coefficient of heat exchange of the roof is substantially constant along the radial generatrix of the roof, and consequently the whole roof has to be designed in such a way as to ensure a coefficient of heat exchange relative to the most critical, central area.
  • the cooling system is oversized.
  • US-A-4.815.096 teaches a cooling system including sprays which cooperate with the outer face of the roof, the sprayed water flowing on the outer face and being collected in the outer peripheral area of the roof.
  • This system has the disadvantage that the greatest flow of water is in the outer peripheral area, where the least heat flow is required.
  • conduits under pressure may be circular or helical rings, or of another shape.
  • roofs known to the state of the art which are composed of autonomous panels in contiguous segments, each panel including its own autonomous cooling system.
  • the system of cooling conduits associated with each panel is shaped like a coil, and comprises a high number of curves which considerably increase losses in the water load.
  • the purpose of the invention is to provide a cooled roof for electric arc furnaces and ladle furnaces which has a low water consumption and a low operating pressure of the cooling water, and yet at the same time ensures a high level of operational safety.
  • the cooled roof according to the invention guarantees at all times and at all points the substantial removal of the desired heat flow, preventing local over-heating which could lead to the cooling conduits breaking.
  • the roof according to the invention does not require the melting process to be stopped even in the event that, for reasons such as localised heat overload or localised heat strain, there is a breakage in one of the conduits for the circulation of the cooling water.
  • the cooled roof according to the invention includes a coefficient of heat exchange which can be varied in a radial direction in such a way as to guarantee an optimum flow of heat exchange which is coherent with the requirements of the roof.
  • the coefficient of heat exchange is at least double that of standard panels known to the state of the art.
  • the roof according to the invention is composed of a plurality of adjacent and autonomous panels, of a reduced size, each of which has at least a longitudinal conduit through which the cooling water flows, and a coefficient of heat exchange which increases radially as it goes from the outer periphery of the roof towards the central area of the roof where the electrodes are inserted.
  • the development of the heat coefficient is a function of the development of the heat flow, generated by the melting furnace, which is to be removed, in such a way as to ensure optimum conditions of heat exchange at every point of the furnace.
  • the cooling water flows lengthwise in the conduits associated with each panel, therefore in a radial direction with respect to the furnace, and at a speed which increases as it passes from the peripheral area towards the central area of the roof.
  • the cooling water flows in a radial direction in each panel and at a speed which decreases as it goes from the centre towards the periphery.
  • the transverse transit section for the cooling water inside the conduits associated with the panels decreases as it goes from the periphery towards the central area of the roof.
  • This reduction in the section of the conduits from the periphery to the centre of the roof can be from 25% to 50%.
  • the increase in the speed of the water, and consequently in the coefficient of heat exchange, going from the outer diameter of the roof to the inner diameter near the electrodes, can reach 250% or even more of the speed and the coefficient of heat exchange at the outer diameter of the roof.
  • the cooling water works at low pressure, with a reduced overpressure, so that, even in the event of a breakage in the conduit, the quantity of water entering the furnace is slight, and it evaporates before it comes into contact with the molten metal without causing sudden increases in pressure, and thus the melting process does not need to be stopped.
  • the pressure inside the conduits is between 1 and 5 bar, and the fall in pressure of the water inside each panel is less than 1.5 bar.
  • the conduits through which the water passes include inner partition means which define at least a lower section for the water to pass through, facing towards the inside of the furnace.
  • these partition means define two sections inside the conduits, respectively a lower section, facing towards the inside of the furnace, and an upper section, facing towards the outside.
  • These partition means include a variable section which increases according to the increase in the section of the conduits with which they are associated.
  • At least the area of the lower section through which the water flows and which faces towards the inside of the furnace is reduced as it goes from the periphery towards the centre of the roof, in such a way as to increase the speed of flow of the water passing through.
  • the section of the conduits can be circular, elliptical, oval, sickle-shaped or any other shape suitable for the purpose, the sections always increasing, in cross section, as they go from the centre towards the periphery of the roof.
  • the panels which make up the cooled roof according to the invention have at their lower part means to anchor the layers of waste which is progressively formed; these anchor means are made advantageously of copper, or of copper lined with iron, so as to ensure the efficient and correct anchoring of a desired layer of waste on the face of the panels which faces towards the inside of the furnace.
  • This layer of waste protects the cooling panels from heat stresses and mechanical stresses which may occur inside the furnace.
  • the anchor means may be associated directly with the panels, in an intermediate position or at the point where contiguous panels join, or they may be inserted directly between adjacent panels.
  • the cooled roof according to the invention is equipped with one or more burners, for example of the type using oxymethane, suitable to create a protective screen of natural gas in the area immediately underneath the roof itself.
  • This natural gas reacts with the atmosphere of the furnace to produce a layer of carbon-based powders which are deposited on and attach themselves to the lower part of the roof.
  • the carbon powders come into contact with oxygen, react and burn, thus maintaining the temperature of the whole inner surface of the roof and therefore making it possible to have a roof which is already prepared, so that it does not require a transitional step or reconditioning step when the melting cycle is restarted.
  • the cooled roof 10, applied to an electric arc furnace or ladle furnace, is composed of a plurality of panels 11 side by side and autonomous.
  • Each of these panels 11 includes at least a lengthwise conduit 12 through which the cooling water passes, where the water is made to circulate lengthwise in a radial direction.
  • each panel 11 includes three conduits 12 associated at one end to the same inlet water collector 13 and, at the other end, to the same outlet water collector 14.
  • the water flows from the centre towards the periphery of the roof 10 at a decreasing speed.
  • each conduit 12 varies along the longitudinal axis of the panel 11, from the periphery to the centre of the roof 10, narrowing in a ratio, advantageously but not necessarily progressively, which may be even more than 2.5.
  • variable section of these conduits 12 may be achieved with conduits which have cross sections of a different shape.
  • Fig.4 shows the cross section of a conduit 12 with a sickle-shaped section which widens as it goes towards the periphery of the cooled roof 10.
  • substantially conventional pipes are used which have inside them partition means 17 which extend lengthwise so as to define at least a lower section 12a for the passage of the water.
  • the partition means 17 are composed of an intermediate plate 11), suitably shaped, which defines a lower section 12a and an upper section 12b through which the water passes.
  • At least the lower section 12a narrows in section as it goes towards the central area of the roof 10.
  • the water in the lower section 12a is made to flow at a speed of between 0.8 and 1.5 metres per second in correspondence with the outer diameter of the roof 10, and at a speed of between 2 and 4 metres per second in correspondence with the inner diameter of the roof 10, while the water in the upper section 12b is still, or flows at a reduced speed, for example less than 1 metre per second.
  • the upper section 12b is empty and the water flows only in the lower section 12a which faces inside the furnace.
  • the partition means 17 are composed of a solid body 217, of a shape which mates with the section of the conduit 12 and associated solidly to its upper inner face in such a way as to define only one lower section 12a where the cooling water circulates.
  • the conduits 12 may have a cross section of any desired shape, for example elliptical or oval (Figs. 7a, 7b, 7c), or substantially circular (Figs. 27d, 7e), provided the cross section narrows as it goes towards the centre of the roof 10.
  • Figs. 4, 5 and 6 show conduits 12 with a sickle-shaped section, composed of two convex walls, respectively the lower wall 15a and the upper wall 15b, welded lengthwise at the sides so as to define a transit conduit 12 which narrows longitudinally in section as it goes from the outer periphery towards the centre of the roof 10.
  • the conduit 12 has an elliptical or oval section
  • the partition means 17 are composed of a convex metal plate 117 which is associated at its ends with the inner wall of the conduit 12.
  • the partition means 17 are composed of a hollow body 317, in this case elliptical in section, which is associated with the inner upper wall of the conduit 12.
  • the inner part of the hollow body 317 defines, in this case, the upper section 12b filled with air or water passing through at low speed.
  • the partition means 17 are composed of a solid body 217, elliptical in section, which is associated with the inner upper wall of the conduit 12.
  • the oval or elliptical section shown in Figs.7a to 7c has optimum characteristics of heat exchange, due to a substantially homogenous heat field over the whole wall where heat exchange takes place.
  • the lower wall 15a is thicker than the upper wall 15b so as to prevent localised over-heating caused by any possible sprays of liquid metal.
  • Figs.7d and 7e show conduits 12 with a circular section which narrows as it goes towards the centre of the roof 10, and where the partition means 17 are composed respectively of a hollow cylindrical body 317 and a solid cylindrical body 217.
  • the partition means 17 are composed of a wall 117, substantially U-shaped so as to define an upper section 12b and a lower section 12a through which the cooling water passes.
  • the lower section 12a through which the cooling water flows is substantially shaped like a circular sickle, and has given excellent results in terms of heat exchange.
  • the lower section 12a through which the cooling water flows is substantially shaped like a circular segment.
  • the cooled roof 10 has at its lower part anchor means 16 onto which a layer of waste 18 is progressively anchored.
  • Figs.5, 6 and 6a show anchor means 16 composed of a plurality of fins 19 arranged offset and facing sideways alternatively from opposite sides.
  • the fins 19 are inserted between one conduit 12 and the contiguous one.
  • the anchor means 16 are composed of a plurality of T-shaped fins 119.
  • These fins 119 can be made completely of copper, or of copper lined with iron as shown on the right of Fig.8.
  • the lower wall 15a of the panels 11, which faces towards the inner part of the furnace, may be undulated, and the upper wall 15b, which faces towards the outer part of the furnace, substantially plane (Fig.9).
  • the lower wall 15a is substantially plane while the upper wall 15b is undulated.
  • the upper wall 15b is normally spot welded to the lower wall 15a, for example by means of flash welding or some other type of welding, at the points referenced as 25 in Fig.10.
  • Figs.11 to 14 show a variant where the roof 10 is equipped with a plurality of burners 20, in this case substantially distributed on a circumference outside the circumference which circumscribes the electrode 21.
  • the seatings for the burners 20 are obtained between the conduits 12 where the cooling water for the roof 10 circulates.
  • the burners 20 are fed, in this case, by an oxygen feed conduit 22 and a methane feed conduit 23.
  • the burners 20 are suitable to deliver a flow of natural gas which, during the working cycle of the furnace, leads to the formation of a protective shield, made of particles of carbon dust and of waste, for the lower part of the roof 10.
  • This protective shield keeps the roof 10 from over-heating and prevents even partial cooling of the atmosphere inside the furnace.
  • the gas is made to flow from the burners 20 when the temperature of the scrap has reached between about 850°C and 1100°C with a delivery flow of about 45-65 Nm 3 per hour.
  • Figs. 13 and 14 show two possible uses where, respectively, the conduits 12 are circular and include inner partition means 17 (Fig.13), and have a circular sickle section (Fig.14).

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Furnace Housings, Linings, Walls, And Ceilings (AREA)
EP97101864A 1996-02-13 1997-02-06 Toit refroidit pour fours ou poches à arc Withdrawn EP0790474A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITUD960018 1996-02-13
IT000018A ITUD960018A1 (it) 1996-02-13 1996-02-13 Volta raffreddata per forni elettrici ad arco e per forni siviera

Publications (1)

Publication Number Publication Date
EP0790474A1 true EP0790474A1 (fr) 1997-08-20

Family

ID=11422019

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97101864A Withdrawn EP0790474A1 (fr) 1996-02-13 1997-02-06 Toit refroidit pour fours ou poches à arc

Country Status (4)

Country Link
EP (1) EP0790474A1 (fr)
KR (1) KR970062639A (fr)
BR (1) BR9700229A (fr)
IT (1) ITUD960018A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10121139A1 (de) * 2001-04-30 2002-10-31 Sms Demag Ag Kühlelement zur Kühlung von Wänden von Schachtöfen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2420108A1 (fr) * 1978-03-17 1979-10-12 Inst Ochistke Tekhn Refroidisseur de four a cuve
FR2445942A1 (fr) * 1979-01-04 1980-08-01 Clesid Sa Panneau pour four electrique
FR2476823A1 (fr) * 1980-02-22 1981-08-28 Clesid Sa Voute perfectionnee pour four electrique a arc
EP0063549A1 (fr) * 1981-04-14 1982-10-27 DANIELI & C. OFFICINE MECCANICHE S.p.A. Couvercle refroidi pour fours électriques
DE4007662C1 (fr) * 1990-03-10 1991-05-23 Juenger + Graeter Gmbh & Co. Feuerfestbau, 6830 Schwetzingen, De
US5426664A (en) * 1994-02-08 1995-06-20 Nu-Core, Inc. Water cooled copper panel for a furnace and method of manufacturing same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2420108A1 (fr) * 1978-03-17 1979-10-12 Inst Ochistke Tekhn Refroidisseur de four a cuve
FR2445942A1 (fr) * 1979-01-04 1980-08-01 Clesid Sa Panneau pour four electrique
FR2476823A1 (fr) * 1980-02-22 1981-08-28 Clesid Sa Voute perfectionnee pour four electrique a arc
EP0063549A1 (fr) * 1981-04-14 1982-10-27 DANIELI & C. OFFICINE MECCANICHE S.p.A. Couvercle refroidi pour fours électriques
DE4007662C1 (fr) * 1990-03-10 1991-05-23 Juenger + Graeter Gmbh & Co. Feuerfestbau, 6830 Schwetzingen, De
US5426664A (en) * 1994-02-08 1995-06-20 Nu-Core, Inc. Water cooled copper panel for a furnace and method of manufacturing same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10121139A1 (de) * 2001-04-30 2002-10-31 Sms Demag Ag Kühlelement zur Kühlung von Wänden von Schachtöfen

Also Published As

Publication number Publication date
KR970062639A (ko) 1997-09-12
ITUD960018A0 (fr) 1996-02-13
ITUD960018A1 (it) 1997-08-14
BR9700229A (pt) 1998-06-30

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