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WO2005082797A1 - Methode pour eliminer des impuretes dans de l'etain fondu - Google Patents

Methode pour eliminer des impuretes dans de l'etain fondu Download PDF

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Publication number
WO2005082797A1
WO2005082797A1 PCT/GB2005/000702 GB2005000702W WO2005082797A1 WO 2005082797 A1 WO2005082797 A1 WO 2005082797A1 GB 2005000702 W GB2005000702 W GB 2005000702W WO 2005082797 A1 WO2005082797 A1 WO 2005082797A1
Authority
WO
WIPO (PCT)
Prior art keywords
tin
molten tin
molten
bath
sulphur
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.)
Ceased
Application number
PCT/GB2005/000702
Other languages
English (en)
Inventor
Paul Arthur Holmes
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.)
Pilkington Group Ltd
Original Assignee
Pilkington PLC
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
Priority claimed from GB0404330A external-priority patent/GB0404330D0/en
Priority claimed from GB0414906A external-priority patent/GB0414906D0/en
Application filed by Pilkington PLC filed Critical Pilkington PLC
Publication of WO2005082797A1 publication Critical patent/WO2005082797A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B18/00—Shaping glass in contact with the surface of a liquid
    • C03B18/02—Forming sheets
    • C03B18/18—Controlling or regulating the temperature of the float bath; Composition or purification of the float bath
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

  • the present invention relates to the manufacture of glass.
  • float glass refers to the glass in sheet or ribbon form which is manufactured by the float glass process, where batch materials are melted in a tank to form molten glass which is subsequently presented to a forming means (a bath containing a molten metal, commonly tin, upon which the molten glass floats) where the glass is formed into a solid ribbon.
  • ribbon refers to the uninterrupted strip of glass having major surfaces which are substantially parallel continually produced in the float glass process. On leaving the bath the ribbon is annealed (i:e. cooled in a controlled manner) and, normally, cut into sheets.
  • Oxygen may be present in the molten tin due to leakage of atmospheric air into the bath atmosphere caused by incomplete sealing of the bath, or by migrating from the glass ribbon. Sulphur is usually present by migrating from the glass ribbon. If oxygen or sulphur is present in the molten tin, tin sublimes as SnO or SnS at temperatures greater than 850°C and can deposit on the bath ceiling towards the (relatively) cold end of the bath ( ⁇ 600°C).
  • US3494755 discloses a method and apparatus which prevents tin drips from contacting the glass ribbon.
  • the apparatus comprises a collecting surface located towards the cold end of the bath and positioned between the ceiling and the ribbon. Tin drips from the ceiling deposit on the collecting surface and are returned to the bath.
  • GB2235447 discloses a method and apparatus similar to that of US3494755 in which the collecting surface is made from carbon fibre composite material having specific properties. Whilst these prior known methods appear to work well, the provision of additional apparatus above the ribbon is cumbersome and other methods of reducing yield loss from tin drip are desirable.
  • a method of removing oxygen and/or sulphur contamination from molten tin by treating the molten tin by a process of electrolysis not reliant on the addition of additive elements to the molten tin there is provided a method of treating molten tin used in float glass production to reduce the amount of oxygen and/or sulphur contamination therein, the method comprising the step of subjecting the molten tin to a process of electrolysis not reliant on addition of additive elements to the molten tin.
  • This method removes oxygen and/or sulphur from the molten tin which in turn reduces the volatilisation of SnO and/or SnS which causes tin drip.
  • the method is normally carried out without the addition of any additive element to the molten tin.
  • the contaminated tin is removed from the float bath in which it is contained, treated by a process of electrolysis and then returned to the bath.
  • a method of manufacturing float glass including the aforementioned method of removing oxygen and/or sulphur contaminants from molten tin used in the float bath.
  • the molten tin is in electrolytic contact with a cathode and a molten conductive salt connected to an anode.
  • Figure 1 is a schematic cross section through an apparatus used to demonstrate the electrolytic removal of sulphur from molten tin in accordance with the invention.
  • Figure 2 is a schematic plan view of part of the bath used in a float glass manufacturing operation, incorporating apparatus to treat the molten metal according to the present invention.
  • Figure 3 is a schematic side section of an electrolytic cell which includes a recessed channel electrode.
  • Figure 1 shows a tube reactor 1 constructed of InconelTM alloy, approximately 650mm in length, 110mm internal diameter with a 5mm wall thickness, with lid 2.
  • An O ring 3 provides a gas tight seal between reactor and lid, with a duct 4 around the neck of the reactor providing for water cooling of the O ring to protect it from overheating.
  • a graphite crucible 5 sits on a ceramic brick 14 at the base of the reactor and contains the layer of molten tin 6 to be purified and a layer of molten salt 7 electrolyte over the molten tin.
  • Graphite electrodes, an anode 8 and a cathode 9 extend through rubber bungs 10 in the InconelTM lid; the anode 8 terminates in the molten salt layer 7, while cathode 9 is shown insulated by a surrounding alumina sleeve 11 where it passes through the molten salt layer and terminating in the molten tin.
  • An inlet duct 12 and an outlet duct 13 are provided for circulation of inert atmosphere through the reactor. The apparatus was used to treat molten tin containing sulphur and oxygen contaminants removed from the float bath of a float glass manufacturing line.
  • a sample of molten tin was extracted from the tin bath of an operating float glass line into a fused silica tube of about 1cm internal diameter. The tin was allowed to cool to room temperature inside the tube and then removed and immediately cut into aliquots of approximately 1cm in length, discarding the end pieces.
  • molten salt electrolyte 7 A wide range of salt electrolytes are available, including calcium, strontium and barium chlorides. The important features are that the electrolytes should be molten at the temperature of electrolysis and should be dried rigorously to exclude water. As shown in Table 1, two electrolytes were used, pure calcium chloride (melting point 770°C) and a eutectic mixture of calcium and strontium chlorides (melting point 600°C).
  • the apparatus shown in Figure 1 was initially set up so that both carbon electrodes were immersed in the salt electrolyte but not touching the tin sample.
  • the InconelTM reactor was placed in a vertical furnace and brought to the required temperature. The reactor had been flushed out with dry argon and dry argon was passed through the apparatus via inlet duct 12 and outlet duct 13 during the entire procedure.
  • a eutectic mixture of calcium and strontium chlorides used as molten electrolyte was first subjected to a pre-electrolysis procedure to remove any water in the salt. At all times the voltage applied to the electrodes was kept well below that required to decompose the salt (approx. 3.2V).
  • the pre-electrolysis involved applying a voltage of 2N with both graphite electrodes dipping into the molten salt but not touching the molten tin surface. When the current had stabilised, the power was removed and the cathode lowered into contact with the molten tin (as shown in Figure 1), with the alumina sleeve preventing contact between the cathode and the electrolyte.
  • the voltage indicated in Table 1 was then applied between cathode dipping into the molten tin and anode dipping into the molten electrolyte.
  • the initial current flowing declined rapidly to a few hundred milliamps after 1 hour and remained fairly constant thereafter.
  • the voltage was applied for four hours before allowing the apparatus to cool to room temperature under the flow of dry argon.
  • FIG. 2 shows a bath 20 used in a process of manufacturing float glass.
  • the bath 20 contains molten tin 22 and a ribbon of glass 24 which floats on the molten tin 22.
  • An electrolysis apparatus, generally designated 26, is associated with the bath to remove contaminants from the molten tin contained in the bath.
  • a suitable electrolysis apparatus is disclosed in EP0272803, the disclosure of which is incorporated herein by reference.
  • the apparatus of EP0272803, known as a recessed channel electrode (RCE) allows for electrolysis of a flowing molten metal and thus contaminated molten tin from the bath can be removed therefrom and treated in an RCE and the treated tin can be subsequently returned to the bath.
  • RCE recessed channel electrode
  • the electrolytic cell shown in Figure 3 is similar to that disclosed in EP0272803 and has a cathode 30 associated with an anode 32 and a diaphragm 34.
  • the cathode 30 contains molten electrolyte 36 which may be a eutectic mixture of BaCl 2 and CaCl 2 whose melting point is about 600°C. Contaminated molten tin is removed from the bath and trickled through the channels of the cathode. Molten tin in the cathode is depicted as reference numeral 38.
  • the atomic oxygen and sulphur generated at the carbon anode can undergo further chemical reaction, for example to carbon dioxide and sulphur dioxide.
  • the result of this process is that the oxygen and sulphur contaminants are removed from the molten tin which is now returned to the bath.
  • the contaminated tin to be treated may be removed from any point along the bath from the hot end ( ⁇ 1000°C) to the cold end ( ⁇ 600°C).
  • the treated tin may need to be heated before it is returned to the bath to reduce the temperature gradient between the molten tin in the bath and the returning treated tin.
  • the invention has been specifically described with reference to embodiments in which the tin is removed from the float bath for purification, it will be appreciated that the invention is applicable to the treatment of tin within the float bath, e.g. in a pocket at the side of the bath as described in GB1025581, or even within the body of the bath, when, however, it may be necessary to provide means for removing oxygen and or sulphur impurities released by electrolysis from the bath.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

L'invention concerne des méthodes dans lesquelles des impuretés de soufre et/ou d'oxygène sont éliminées à partir d'étain fondu, de manière électrolytique. Cette méthode est utile pour réduire la contamination de l'étain fondu utilisé dans un bain de flottage d'un procédé de fabrication de verre : elle permet de réduire les défauts de la surface du verre provoqués par des 'taches' d'étain, et permet d'augmenter le rendement de verre. L'étain contaminé peut être traité à l'intérieur d'un bain de flottage, ou retiré du bain de flottage, électrolysé et renvoyé dans ce bain.
PCT/GB2005/000702 2004-02-27 2005-02-25 Methode pour eliminer des impuretes dans de l'etain fondu Ceased WO2005082797A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB0404330.3 2004-02-27
GB0404330A GB0404330D0 (en) 2004-02-27 2004-02-27 Improvements in or relating to the manufacture of glass
GB0414906A GB0414906D0 (en) 2004-07-02 2004-07-02 Improvements in or relating to the manufacture of glass
GB0414906.8 2004-07-02

Publications (1)

Publication Number Publication Date
WO2005082797A1 true WO2005082797A1 (fr) 2005-09-09

Family

ID=34913659

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2005/000702 Ceased WO2005082797A1 (fr) 2004-02-27 2005-02-25 Methode pour eliminer des impuretes dans de l'etain fondu

Country Status (1)

Country Link
WO (1) WO2005082797A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117720072A (zh) * 2023-12-15 2024-03-19 洛玻集团洛阳龙海电子玻璃有限公司 一种去除玻璃退火窑二氧化硫保护气体微量水的方法

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3480420A (en) * 1965-11-24 1969-11-25 Pilkington Brothers Ltd Process and apparatus for vacuum purification of the float glass bath
GB1187330A (en) * 1968-06-19 1970-04-08 Saratovspy Gnii Stekla Improvements relating to Manufacture of Sheet Glass
GB1216378A (en) * 1968-02-28 1970-12-23 Saratovsky Gnii Stekla Method of and apparatus for making sheet glass
FR2064389A7 (en) * 1969-10-17 1971-07-23 Glaverbel Float glass manufacture and chemical tough - ening
GB1336194A (en) * 1970-11-23 1973-11-07 Saratovsky Gnii Method of and apparatus for cleaning molten metal contaiminated with dross
GB1373087A (en) * 1970-12-09 1974-11-06 Nat Res Dev Purification of copper and tin
EP0286175A1 (fr) * 1987-04-01 1988-10-12 Shell Internationale Researchmaatschappij B.V. Procédé de production électrolytique de métaux
JP2000247658A (ja) * 1999-02-23 2000-09-12 Asahi Glass Co Ltd フロートガラスの製造方法

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3480420A (en) * 1965-11-24 1969-11-25 Pilkington Brothers Ltd Process and apparatus for vacuum purification of the float glass bath
GB1216378A (en) * 1968-02-28 1970-12-23 Saratovsky Gnii Stekla Method of and apparatus for making sheet glass
GB1187330A (en) * 1968-06-19 1970-04-08 Saratovspy Gnii Stekla Improvements relating to Manufacture of Sheet Glass
FR2064389A7 (en) * 1969-10-17 1971-07-23 Glaverbel Float glass manufacture and chemical tough - ening
GB1336194A (en) * 1970-11-23 1973-11-07 Saratovsky Gnii Method of and apparatus for cleaning molten metal contaiminated with dross
GB1373087A (en) * 1970-12-09 1974-11-06 Nat Res Dev Purification of copper and tin
EP0286175A1 (fr) * 1987-04-01 1988-10-12 Shell Internationale Researchmaatschappij B.V. Procédé de production électrolytique de métaux
JP2000247658A (ja) * 1999-02-23 2000-09-12 Asahi Glass Co Ltd フロートガラスの製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 12 3 January 2001 (2001-01-03) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117720072A (zh) * 2023-12-15 2024-03-19 洛玻集团洛阳龙海电子玻璃有限公司 一种去除玻璃退火窑二氧化硫保护气体微量水的方法

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