GB1585101A

GB1585101A - Metal melting furnace

Info

Publication number: GB1585101A
Application number: GB1387376A
Authority: GB
Original assignee: Morganite Thermal Designs Ltd
Current assignee: Morganite Thermal Designs Ltd
Priority date: 1977-07-06
Filing date: 1977-07-06
Publication date: 1981-02-25

Description

(54) METAL MELTING FURNACE (71) We, MORGANITE THERMAL DESIGNS LIMITED of Norton Works, Woodbury Lane, Norton, Worcester, WR5 2PU, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to metal melting and holding furnaces and will be described as applied to a metal vaporising furnace, such as for the production of zinc powder or zinc oxide, although the invention is applicable to other purposes, such as bale-out furnaces.

It has been proposed to provide a metalmelting furnace comprising a refractory bath with an opening at the top for insertion of an immersion heater consisting of a closed vessel, of graphite for example, suspended from the lower end of a vertically movable gas-burner apparatus, which can be lowered into and raised from the bath, the burner directing flame and hot gas in to the closed graphite vessel for reversal of flow therein and exhaust of the combustion gases through the burner apparatus for recuperation of heat therefrom.

The present invention also provides a furnace with an immersion heater enclosing a heat-recuperating burner but of simple con struction, not requiring elaborate vertically movable burner apparatus, and of good thermal efficiency.

A furnace according to the invention comprises a refractory bath, to hold molten metal up to a given level, a refractory cover over the bath and spaced above the metal level, a cup shaped heat-conductive refractory vessel supported in the bath in an upright position and spaced inwardly from the wall of the bath, so that molten metal can surround the vessel in the bath, the vessel having an upwardly directed mouth closed by cover means defin ing a passage having an outlet leading down wardly into the mouth of the vessel, and a fuel burner in the passage, for directing hot gas into the vessel, the inner surface of the vessel forming a reversing baffle for hot gas, the mouth of the vessel surrounding the out let from the passage in the cover means and the burner having a surrounding clearance in the passage so that reverse flow of hot gas from the vessel can pass upwardly around the burner for heat-recuperative, contra-flow, heatexchange with air supply to the burner.

With a furnace according to the invention, the immersion heater vessel can be a standard crucible, of a size and type to suit requirements, and provision for raising the burner, from or with the furnace cover, need only be means for attaching lifting gear for use on installation or replacement of the crucible.

The invention is illustrated by way of example on the accompanying drawing which shows, somewhat diagrammatically, a vertical section through a metal-vaporising furnace in accordance with the invention.

The furnace illustrated comprises a bath consisting of a casing 1, which may be of metal or brickwork, having an intermediate lining 2, of a refractory, thermally insulating material such as diatomaceous brick, and an inner lining 3, of a refractory material resistant to molten metal such as a cast refractory.

The bath has a sloping end forming an inlet 4 through which are fed billets 5 of metal, such as zinc, to be melted, a flap 6 being provided to close the inlet.

The top of the bath is closed, except for a metal vapour outlet 7 and a vent 8, by a cover 9 having a refractory lining 10. A refractory partition or baffle 11 depends into the bath from the cover lining 10 down to below a normal molten metal level X - X so as to close off the metal inlet 4 and fume vent 8 from the space above the metal level from which metal vapour can pass to the outlet 7. A part 9A of the cover is hinged to form an inspection door.

Near the metal vapour outlet 7, the cover embodies an annular refractory block 12 which provides a passage 13 in which is mounted a gas-air burner 14. The burner is directed downwardly, through the outlet from the passage, into a clay-graphite, cup-shaped refractory vessel 15 mounted on a plinth 16 on the bottom of the bath. As mentioned above, the vessel 15 may be a standard crucible.

The vessel 15 is of such size that it has a surrounding clearance from the wall of the bath, to provide space for molten metal, and the mouth of the vessel closes, with an interposed refractory sealing gasket 17, against the block 12 around the outlet from the passage 13.

The burner.14 is supplied with gas, through a pipe 18, and with air through a pipe 19 and the hollow wall 20 of a heat-exchanger 21 which surrounds the burner 14 and provides, extending from a clearance 22 around the burner in the passage 13, an exhaust duct 23 for hot gas to pass, to an outlet 24, in contraflow heat-exchange with the air supply through the hollow wall 20. This arrangement of a burner in a heatexchanger is a known kind of recuperative burner and gives good thermal efficiency.

The exhaust outlet 24 is shown as an annular jacket around the metal vapour outlet 7 and this is an optional arrangement according to requirements for control of temperature through the outlet 7.

The vessel 15, having a high thermal conductivity, becomes heated by the products of fuel combustion, emitted from the burner 14, impinging centrally at the base of the vessel which acts as a reversing baffle to return hot gas upwardly through the clearance 22 in the passage 13. The vessel 15, sealed at its mouth against the block 12, thus forms a completely enclosed immersion heater.

At the end of the bath below the metal vapour outlet 7, the vessel 15 is arranged relatively close to the bath lining 3 so as to form a hot zone 25 in which a metal vaporising temperature can be maintained for the production of metal vapour to pass through the outlet 7 to processing equipment.

For example the vapour of zinc is condensed in a closed system to produce zinc powder or an open or oxidising system to produce zinc oxide.

Although the invention has been described and illustrated as applied to a vaporising furnace, it. may be applied to other bath or pot furnaces, such as a bale-out furnace in which there is provided, instead of the outlet 7, an opening for insertion of a spoon ladle.

It will be appreciated that the partition 11 in effect divides that the space above the level in the bath into a hot area 26, for such purppses as rnaintenance of a bath atmospheric temperature above a metal melting or vapour point, and a less hot area 27, for metal feeding and other purposes requiring access without undue heat loss.

Also, the furnace illustrated could be modi fied, in particular by omitting the pre-heated feed arrangement of the inlet 4 and vent 8, the furnace bath being designed for example for direct or batch charging, and the metal vapour outlet leading directly from the furnace, without any heat-exchange provision, as indicated in broken lines at 28.

In a further modification, the rim of the mouth of the vessel 15 could extend through the furnace cover 9, with a surrounding outer collar or other seal, and the cover means closing the mount of the vessel, corresponding to the block 12, could be made as part of a vessel and burner assembly instead of as part of the furnace cover.

Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of Patent No. 1 201 119 and of Patent No. (Application No. 13875/76) (Serial No. 1585102).

WHAT WE CLAIM IS: 1. A furnace comprising a refractory bath, to hold molten metal up to a given level, a refractory cover over the bath and spaced above the metal level, a cup-shaped heat-conductive refractory vessel supported in the bath in an upright position and spaced inwardly from the wall of the bath, so that molten metal can surround the vessel in the bath, the vessel having an upwardly-directed mouth closed by cover means defining a passage having an outlet leading downwardly into the mouth of the vessel, and a fuel burner in the passage, for directing hot gas into the vessel, the inner surface of the vessel forming a reversing baffle for hot gas, the mouth of the vessel surrounding the outlet from the passage in the cover means and the burner having a surrounding clearance in the passage so that reverse flow of hot gas from the vessel can pass upwardly around the burner for heat-recuperative, contra-flow, heat-exchange with air supply to the burner.

2. A furnace according to Claim 1, in which the refractory cover has a refractory partition or baffle depending into the bath down to below the normal molten metal level so as to divide the space above the metal level in the bath into a hot area adjacent to the vessel and a less hot area.

3. A furnace according to claim 1 or 2, in which the cover means closing the mouth of the vessel comprises an annular refractory block in which the burner is mounted.

4. A furnace according to Claim 1,2 or 3, in which a metal vapour outlet from the bath is jacketed by a burner exhaust gas outlet.

5. A metal-vaporising furnace substan tially as described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

mouth of the vessel closes, with an interposed refractory sealing gasket 17, against the block

12 around the outlet from the passage 13.

The burner.14 is supplied with gas, through a pipe 18, and with air through a pipe 19 and the hollow wall 20 of a heat-exchanger 21 which surrounds the burner 14 and provides, extending from a clearance 22 around the burner in the passage 13, an exhaust duct 23 for hot gas to pass, to an outlet 24, in contraflow heat-exchange with the air supply through the hollow wall 20. This arrangement of a burner in a heatexchanger is a known kind of recuperative burner and gives good thermal efficiency.

The exhaust outlet 24 is shown as an annular jacket around the metal vapour outlet 7 and this is an optional arrangement according to requirements for control of temperature through the outlet 7.

The vessel 15, having a high thermal conductivity, becomes heated by the products of fuel combustion, emitted from the burner 14, impinging centrally at the base of the vessel which acts as a reversing baffle to return hot gas upwardly through the clearance 22 in the passage 13. The vessel 15, sealed at its mouth against the block 12, thus forms a completely enclosed immersion heater.

At the end of the bath below the metal vapour outlet 7, the vessel 15 is arranged relatively close to the bath lining 3 so as to form a hot zone 25 in which a metal vaporising temperature can be maintained for the production of metal vapour to pass through the outlet 7 to processing equipment.

For example the vapour of zinc is condensed in a closed system to produce zinc powder or an open or oxidising system to produce zinc oxide.

Although the invention has been described and illustrated as applied to a vaporising furnace, it. may be applied to other bath or pot furnaces, such as a bale-out furnace in which there is provided, instead of the outlet 7, an opening for insertion of a spoon ladle.

It will be appreciated that the partition 11 in effect divides that the space above the level in the bath into a hot area 26, for such purppses as rnaintenance of a bath atmospheric temperature above a metal melting or vapour point, and a less hot area 27, for metal feeding and other purposes requiring access without undue heat loss.

Also, the furnace illustrated could be modi fied, in particular by omitting the pre-heated feed arrangement of the inlet 4 and vent 8, the furnace bath being designed for example for direct or batch charging, and the metal vapour outlet leading directly from the furnace, without any heat-exchange provision, as indicated in broken lines at 28.

In a further modification, the rim of the mouth of the vessel 15 could extend through the furnace cover 9, with a surrounding outer collar or other seal, and the cover means closing the mount of the vessel, corresponding to the block 12, could be made as part of a vessel and burner assembly instead of as part of the furnace cover.

Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of Patent No. 1 201 119 and of Patent No. (Application No. 13875/76) (Serial No. 1585102).

WHAT WE CLAIM IS: 1. A furnace comprising a refractory bath, to hold molten metal up to a given level, a refractory cover over the bath and spaced above the metal level, a cup-shaped heat-conductive refractory vessel supported in the bath in an upright position and spaced inwardly from the wall of the bath, so that molten metal can surround the vessel in the bath, the vessel having an upwardly-directed mouth closed by cover means defining a passage having an outlet leading downwardly into the mouth of the vessel, and a fuel burner in the passage, for directing hot gas into the vessel, the inner surface of the vessel forming a reversing baffle for hot gas, the mouth of the vessel surrounding the outlet from the passage in the cover means and the burner having a surrounding clearance in the passage so that reverse flow of hot gas from the vessel can pass upwardly around the burner for heat-recuperative, contra-flow, heat-exchange with air supply to the burner.
2. A furnace according to Claim 1, in which the refractory cover has a refractory partition or baffle depending into the bath down to below the normal molten metal level so as to divide the space above the metal level in the bath into a hot area adjacent to the vessel and a less hot area.
3. A furnace according to claim 1 or 2, in which the cover means closing the mouth of the vessel comprises an annular refractory block in which the burner is mounted.
4. A furnace according to Claim 1,2 or 3, in which a metal vapour outlet from the bath is jacketed by a burner exhaust gas outlet.
5. A metal-vaporising furnace substan tially as described with reference to the accompanying drawing.