GB1585102A

GB1585102A - Metal vapourising furnace

Info

Publication number: GB1585102A
Application number: GB1387576A
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) METALVAPORISING 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 vaporising furnaces for such purposes as melting zinc, driving or drawing off zinc vapour and processing the vapour, for instance by condensation in a closed system to produce zinc powder or condensation in an open or oxidising system to produce zinc oxide.

Such a furnace may be used for vaporising metals other than zinc and for any utilisation of the metal vapour.

In general, the invention provides an improved form of bath or pot furnace with an immersion heater arranged to produce metal vapour.

According to the invention, the furnace 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, the bath and cover forming a metal chamber, a heatconductive 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, a passage or passages in the cover for direction of hot gas from a fuel burner into the vessel and for exhaust of hot gas from the vessel, the interior of the vessel forming a reversing baffle for the hot gas and being in closed communication with the passage or passages through the cover so that combustion gases do not enter the metal chamber, the space available for molten metal between part of the vessel and the wall of the bath being so limited as to provide a hot zone in which a metal vaporising temperature can be maintained and the metal chamber space above the metal level in the vicinity of the hot zone being closed except for a metal vapour outlet.

In a preferred construction, a closed space of the metal chamber above the metal level in the vicinity of the hot zone is defined by a heatinsulating refractory partition or baffle depending from the furnace cover into the bath to a lower level than the metal level.

The preferred construction may also include the heater vessel being arranged close to the wall at one part of the bath to provide a hot zone relatively remote from an inlet for metal to be melted and the closed space being defined by the adjoining cover and wall of the bath around the vessel and by the partition or baffle arranged between the vessel and the metal inlet.

For heat recuperation or temperature control of the metal vapour, the metal vapour outlet may be arranged in heat-exchange proximity with an air supply pipe or duct or with the passage in the cover through which the hot gas exhausts.

Preferably the furnace is heated by a heat recuperative fuel burner mounted as a selfcontained system in a passage through the furnace cover and the invention will be further described in this form.

However, other burner systems could be used and, in particular, there could be separate passages through the furnace cover for the burner, or the flame or gas therefrom, and for the exhaust gas.

A preferred embodiment of the invention, as applied to a furnace with a recuperative burner, will now be described with reference to the accompanying drawing which shows, somewhat diagrammatically, a vertical section through the furnace.

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, cupshaped refractory vessel 15 mounted on a plinth 16 on the bottom of the bath. 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 heat-exchanger 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 utilising a recuperative burner, any other system could be used for heating the vessel 15, utilising one or more passages through the furnace for admission and exhaust of combustion gases as a selfcontained system so as not to contaminate the metal vapour.

It will be appreciated that-the partition 11 in effect divides the space above the metal level in the bath into a hot area 26, for such purposes as maintenance 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 modified, in particular by omitting the pre-heated feed arrangement of the inlet 3 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 mouth 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 201119 and of Patent No. (Application No. 13873/76) Serial No.1585101.

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, the bath and cover forming a metal chamber, a 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, a passage or passages in the cover for direction of hot gas from a fuel burner into the vessel and for exhaust of hot gas from the vessel, the interior of the vessel forming a reversing baffle for the hot gas and being in closed communication with the passage or passages through the cover so that combustion gases do not enter the metal chamber, the space available for molten metal between part of the vessel and the wall of the bath being so limited as to provide a hot zone in which a metal vaporising temperature can be maintained and the metal chamber space above the metal level in the vicinity of the hot zone being closed except for a metal vapour outlet.

2. A furnace according to Claim 1, in which a closed space of the metal chamber above the metal level in the vicinity of the hot zone is defined by a heat-insulating refractory partition or baffle depending from the furnace cover into the bath to a lower level than the metal level.

3. A furnace according to Claim 2, in which the vessel is arranged close to the wall at one part of the bath to provide a hot zone relatively remote from an inlet for metal to be melted and the closed space is defined by the adjoining cover and wall of the bath around

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

Claims

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

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, cupshaped refractory vessel 15 mounted on a plinth 16 on the bottom of the bath. 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 heat-exchanger 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 utilising a recuperative burner, any other system could be used for heating the vessel 15, utilising one or more passages through the furnace for admission and exhaust of combustion gases as a selfcontained system so as not to contaminate the metal vapour.

It will be appreciated that-the partition 11 in effect divides the space above the metal level in the bath into a hot area 26, for such purposes as maintenance 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 modified, in particular by omitting the pre-heated feed arrangement of the inlet 3 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 mouth 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 201119 and of Patent No. (Application No. 13873/76) Serial No.1585101.

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, the bath and cover forming a metal chamber, a 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, a passage or passages in the cover for direction of hot gas from a fuel burner into the vessel and for exhaust of hot gas from the vessel, the interior of the vessel forming a reversing baffle for the hot gas and being in closed communication with the passage or passages through the cover so that combustion gases do not enter the metal chamber, the space available for molten metal between part of the vessel and the wall of the bath being so limited as to provide a hot zone in which a metal vaporising temperature can be maintained and the metal chamber space above the metal level in the vicinity of the hot zone being closed except for a metal vapour outlet.
2. A furnace according to Claim 1, in which a closed space of the metal chamber above the metal level in the vicinity of the hot zone is defined by a heat-insulating refractory partition or baffle depending from the furnace cover into the bath to a lower level than the metal level.
3. A furnace according to Claim 2, in which the vessel is arranged close to the wall at one part of the bath to provide a hot zone relatively remote from an inlet for metal to be melted and the closed space is defined by the adjoining cover and wall of the bath around

the vessel and by the partition or baffle arranged between the vessel and the metal inlet.
4. A furnace according to Claim 1, 2 or 3, in which the metal vapour outlet is arranged in heat-exchange proximity with an air or gas pipe, duct or passage through the cover.