DE102007009495B4 - Drossbox - Google Patents

Abstract

Drossbox (10) comprising a housing of an upper housing part (11) and a lower housing part (12) and with a lifting device located in the housing with rollers (16) for horizontal transport of a in a Floatbadgehäuse (1) produced glass sheet (6), characterized in that a device (20) for introducing a gas is provided which comprises at least one gas injector (21) arranged in the interior (11) of the throttle box (10) and a gas supply device (30) to which the gas injector (21) is connected and whose Gas delivery rate is 200 to 400 m ³ (i.N.) / H.

Description

The The invention relates to a Drossbox according to the preamble of the claim 1.

The production of flat glass by the float process, known as float glass, has been known since the last century and is essentially based on the fundamental intellectual property rights of Pilkington ( US Pat. No. 3,083,551 A DE 147 19 50 A ).

At the Float method leaves one liquid glass, which is brought about by means of a gutter from the working trough, on a bath of molten metal, generally tin flow. Of the Volume flow of the glass is over a movable slider regulated, with its setting under other things, the glass thickness is set. In the flow direction of Glases seen behind the slider is the pouring lip, from which the molten glass flows continuously to the metal bath, where the Glass melt is formed into a dimensionally stable glass ribbon and stiffens. Subsequently, will the solidified glass ribbon removed from the metal bath. This is behind the Floatbadwanne arranged a lifting device.

The Float glasses made in this way, usually a thickness of less than 1.5 mm are used as thin glass substrates, among others used for the production of flat screens, z. B. of plasma screens (PDP = Plasma Display Panel), field emission screens (FED = Field Emission Display), TFT liquid crystal displays (TFT = Thin Film Transistor), STN Liquid Crystal Monitors (STN = Super Twisted Nematic), plasma-assisted liquid crystal displays (PALC Plasma Assisted Liquid Crystal), electro-luminescence displays (EL) and the like or for the production of thin-film solar cells.

at The flat screens will vary depending on the type of display two glass panes either a thin layer of a liquid crystal compound introduced or it will be on the front and back of the back or front disc each applied dielectric layers, from which cells are formed in which phosphors are housed.

It Here it is important that the layer thickness of the liquid crystal layer or the thickness of the dielectric layer is strictly adhered to, especially with large ones Dimensions of a screen no annoying color distortions or similarity deviations occur. As the layer thicknesses, currently about 30 microns, getting smaller and the screens always grow, This condition is becoming increasingly important.

Even though Float glass is ideally suited for display applications due to its fire-polished surface is, it is in today's required large substrate formats with edge lengths from above 1800 mm not yet possible Display glass to produce the float process, the differences in thickness below 50 μm lie.

The Floatbadvorrichtung essentially comprises the Floatbadwanne with Bottom wall and tub side walls, in which the molten metal is located, the float bath roof (Roof) as well as the side walls (Side ceilings), which are attached to the roof. Between the side walls of the Badger and the tub side walls are sidewall boxes with openings provided, z. B. for the implementation of Top-scooters.

The Floatbadvorrichtung thus has a box-shaped Floatbadgehäuse, which is in a production hall. Before the float bath device are other facilities for the production of molten glass and behind the Floatbadvorrichtung are facilities for processing arranged the produced glass ribbon.

the Floatbadgehäuse is the so-called Drossbox downstream, the device for lifting of the glass ribbon from the float bath has. This device for Lifting the glass strip usually includes rollers for horizontal Transporting the glass band, also referred to as a lift-out scooter become. Furthermore, this Drossbox also serves as a lock chamber, because the discharge opening the Floatbadgehäuses at the same time also the entrance opening the throttle box is.

at the known Floatbadvorrichtungen is in the Floatbadkammer a Forming gas, which usually consists of nitrogen and hydrogen, introduced. In the Floatbadkammer is by continuous gas supply with a given throughput an overpressure uphold an influx of oxygen-containing gas from the outside space into the float bath chamber to prevent. Oxygen in the float bath leads to tin oxidations considerable disadvantages for the surface quality of the product to be produced Glass ribbon.

Due to the overpressure in the Floatbadkammer the forming gas flows, inter alia, through the discharge in Floatbadgehäuse in the Drossbox. In order to avoid gas losses, various solutions have been developed in the past to seal the discharge opening. The DE 27 16 174 A ; DE 18 04 295 C and the DE 1 909 921 A , which represent only a selection of a variety of fonts, deal with appropriate Abdichtmaßnahmen in the region of the discharge, z. B. in the form of curtains.

For additional sealing it is from the GB 1 017 753 A it is known to arrange a tube at the lower end of the dividing wall between the float bath and the Drossbox, from which protective gas flows onto the glass ribbon and subsequently in the feed direction of the glass ribbon.

The outflow of Formiergas from the Floatbadgehäuse in the Drossbox has the Another disadvantage that located in the Formiergasatmosphäre tin and tin oxide containing particles because of the large amount to be covered Distance to the discharge opening Increased on the glass ribbon surface can knock down, where they have surface defects cause. To an outflow the Formiergasatmosphäre on the At least reduce Drossbox, in the side walls of the Floatbadgehäuses Suction pipes (so-called venting-out facilities) mounted over the the Formiergasatmosphäre is sucked in a controlled manner. This ensures, on the one hand, that the tin and tin oxide containing in the Formiergasatmosphäre Particles early be detected and removed and on the other hand, the gas content, the over the discharge into the Drossbox, reduced. Here, the amount of gas supplied and the extracted gas volume are consistent, so that the desired pressure inside the Floatbadgehäuses guaranteed is. Gas losses over the Drossbox are still inevitable and can not Completely be prevented.

task The invention is therefore to provide a Drossbox with which the surface defects the glass ribbon to be reduced.

The object is achieved by a Drossbox, which is characterized in that a device is provided for introducing a gas comprising at least one arranged in the interior of the Drossbox gas injector and a gas supply device to which the gas injector is connected and their gas delivery rate preferably 200-400 m is ³ (i.N.) / h.

In order to it is ensured that the desired overpressure of the order of magnitude of 0.03 mbar to 0.06 mbar the float bath atmosphere can be adjusted.

Preferably is at least in the upper housing part the Drossbox in the space above the rollers at least one gas injector arranged. If the room in the upper part of the housing is divided into zones, is at least in the zone that is near the Floatbadgehäuse at least a gas injector arranged.

According to one another embodiment also in the lower housing part at least in the space between the rollers at least one gas injector be arranged. Preferably, by the in the lower housing part arranged gas injectors pure nitrogen introduced what the Advantage is that the scrapers of the rollers are spared. The Presence of hydrogen in this area has the disadvantage that the scrapers, which are usually made of graphite, due can burn off the high temperatures. Insofar is by the Also, introduce nitrogenous or pure nitrogen gas Inert gas for the scrapers introduced.

Of the Gas injector comprises a tube extending parallel to the rollers with gas outlet openings. This tube is usually mounted in the side wall of the Drossbox and led out there, where the connection to the gas supply device takes place.

Preferably both pipe ends are connected to the gas supply device. This means that the tubes are over the entire width of the Drossbox extend from one side wall to the opposite side wall. By causing the introduction from both sides into the pipe, becomes the incoming one Gas more evenly in the Drossbox distributed. It is advantageous if the tube in divided into two chambers. The symmetrical introduction of the gas in the Drossbox is thereby further improved.

The Gas inlet device is preferably to a gas heating device connected to bring the gas to the desired temperature, so that no tensions in the glass ribbon can occur.

Preferably the gas heating device comprises a cooling device of the end-side Floatbadwand. In this cooling device, is introduced into the likewise inert gas-containing gas, the Gas due to the cooling effect heated and thus can turn for the introduction into the Drossbox be used. As the temperature of the cooling device leaving Gas is at about 150-200 ° C, It is recommended that this already preheated gas another gas heating supply, to the desired Temperature of 700-800 ° C to reach.

The float bath apparatus comprises a float bath housing and a downstream restrictor box wherein there is an atmospheric pressure P _F in the float bath housing and an atmospheric pressure P _D in the restrictor box, where P _D > P _F. The atmospheric pressure P _D is 0.03 to 0.06 mbar above the atmospheric pressure P _F within the Floatbadgehäuses. The method for producing flat glass provides to introduce into the Drossbox an inert gas-containing, oxygen-free gas and in the Drossbox an overpressure set against the atmosphere in Floatbadgehäuse.

through of the inert gas-containing gas with overpressure across from the Floatbadgehäuse will the outflow the Formiergasatmosphäre from the Floatbadgehäuse at least reduced, whereby the Formiergasatmosphäre above the in Floatbadgehäuse provided suction devices (venting-out device) sucked becomes. Harmful particles such as tin or tin oxide particles which are in the float bath atmosphere when used can enrich a tin bath, are accordingly only a short time in the atmosphere and will therefore faster removed. The quality of the glass band becomes clear with this measure improved.

While so far about 60% of the float bath atmosphere got into the Drossbox, this value could be reduced to about half become.

One Another advantage is that no sealing measures to Floatbadgehäuse and the Drossbox are required.

In The throttle box is set to a pressure of 0.03 mbar to 0.06 mbar over the atmospheric pressure the Floatbadgehäuses lies. In particular, a pressure is set by 0.04 to 0.05 mbar over the atmospheric pressure Floatbadgehäuses lies.

It has been shown that a slight overpressure is sufficient to the Proportion of the float bath atmosphere, the over the Drossbox flows out, to less than half to reduce the amount that usually flows out. The surface defects of the glass band go back to the same extent.

The upper limit of 0.06 mbar overpressure compared to the float bath atmosphere should preferably not be exceeded, so that not too much inert gas-containing gas flows into the Floatbadgehäuse, in particular, if this is pure nitrogen. The Formiergasatmosphäre located in Floatbadgehäuse usually has a hydrogen content of about 12 to 15 vol.%, Which is necessary for the reduction of the oxygen in the Floatbadatmosphäre. Although there is no danger that the surface of the glass ribbon is affected by the influx of gas from the Drossbox in the float bath, because this gas contains no harmful particles, but on the other hand, by the incoming gas, especially if it is pure nitrogen, the H ₂ content is reduced, so that the proportion of bound oxygen also decreases.

It has been shown to be at an overpressure that is below the value of 0.06 mbar, this effect is negligible.

In At least two zones of the Drossbox can set different overpressures become. Here, in the Floatbadgehäuse facing the Drossbox the largest overpressure set become.

The Zones of the Drossbox are preferably through curtains above the rollers separated. If multiple zones are provided, the overpressure becomes from zone to zone, starting with the zone, the float bath tub adjacent, gradually reduced. The gas consumption is through This measure reduced.

each Inert gas is for the introduction into the Drossbox suitable. Nitrogen is preferred because of the good availability.

It a gas mixture can be introduced, consisting of nitrogen and hydrogen consists. The addition of hydrogen has the advantage that possibly in the Drossbox is bound to oxygenating water, the subsequently evaporated inside the Drossbox.

The composition of this gas mixture may correspond to the forming gas, which is also introduced into the Floatbadgehäuse. Accordingly, the hydrogen content is preferably less than 20% by volume. Such a gas mixture flowing into the float bath housing has the advantage that the H ₂ content in the float bath housing is not reduced.

200 m ³ (i.N.) / h to 400 m ³ (i.N.) / h of gas can be introduced into the Drossbox. Particularly preferred is a gas amount of 250 m ³ (i.N.) / h to 350 m ³ (i.N) / h.

The m ³ (i.N) designation denotes a standard cubic meter, which is specified in DIN 1343. A standard cubic meter is the quantity corresponding to one cubic meter of gas at a pressure of 1.01325 bar, a relative humidity of 0% (dry gas) and a temperature of 0 ° C.

It a gas heated to a temperature of 600 ° C to 700 ° C may be introduced. The preheating has the advantage of being in contact with the gas in the glass ribbon no tensions due to temperature differences arise and the glass does not break. In this respect, it is advantageous the gas temperature to match the glass ribbon temperature within the Drossbox.

Another advantage is that at these temperatures, the gas volume increased by a multiple compared to the gas volume at 0 ° C, so that to produce the desired Overpressure only a correspondingly small amount of gas is needed.

For the cooling of the Exit area of the float bath housing, in particular, the exit lip at the end of the float bath tub is preferably also used a gas. This gas usually heats up to 150 ° -200 ° C. This Gas can for the introduction a the Drossbox be used. Possibly. becomes the gas preheated before discharge, if the recirculated gas does not have the required temperature. That way is it is possible save corresponding gas quantities.

The Process is particularly suitable for the production of borosilicate glasses, alkali-free glasses, Alumosilikatgläsern, Alumolithiumsilikatgläsern and Precursor glasses for glass ceramic.

Particularly suitable is the method for producing borosilicate glass, z. For fire protection applications, having a composition of (all of the following in terms of weight percent based on oxide):
SiO ₂ 70-85, B ₂ O ₃ 7-13, Na ₂ O + K ₂ O + Li ₂ O 3-8, MgO + CaO + SrO 0-3, Al ₂ O ₃ 2-7,
for the preparation of alkali-free alumino (boro) silicate glass with a composition of
SiO ₂ 50-70, B ₂ O ₃ ≤15, Al ₂ O ₃ 10-25, MgO 0-10, CaO 0-12, SrO 0-12, BaO 0-15, with MgO + CaO + SiO + BaO 8 -26, ZnO 0-10, ZrO ₂ 0-5, TiO ₂ 0-5, SnO ₂ 0-2,
z. B. for the production of display glass, in particular with a composition of
SiO ₂ > 55-65, B ₂ O ₃ 5-11, Al ₂ O ₃ > 14-25, MgO 0-8, CaO 0-8, SrO 0-8, BaO ≤ 10 with MgO + CaO + SrO + BaO 8-21, ZnO 0-5, ZrO ₂ 0-2, TiO ₂ 0-3, SnO ₂ 0-2,
in particular SiO ₂ > 58-65, B ₂ O ₃ > 6-10.5, Al ₂ O ₃ > 14-25, MgO 0 - <3, CaO 0-9, BaO> 3-8 with MgO + CaO + BaO 8-18, ZnO 0 - <2, As ₂ O ₃ -free, Sb ₂ O ₃ -free,
preferably Zn oxide, Ce oxide, Zr oxide, Ti oxide free

It is also particularly suitable for the production of various green glasses for glass-ceramic, such. B. with
SiO ₂ 55-69, Al ₂ O ₃ 19-25, Li ₂ O 3-5, Na ₂ O 0-1.5, K ₂ O 0-1.5, Σ Na ₂ O + K ₂ O 0.2 -2, MgO 0.1-2.2, CaO 0-15, SrO 0-1.5, BaO 0-2.5, Σ MgO + CaO + SrO + BaO below 6, ZnO 0-1.5, TiO ₂ 1-5, ZrO ₂ 1-2.5, SnO ₂ 0 to less than 1, Σ TiO ₂ + SrO + SnO _{2 2} 2.5-5, P ₂ O ₅ 0-3
or a glass-ceramic precursor glass having a composition of
SiO ₂ 55-75, Al ₂ O ₃ 15-30, Li ₂ O 2.5-6, Σ Na ₂ O + K ₂ O less than 6, Σ MgO + CaO + SrO + BaO less than 6, B ₂ O ₃ 0 to less than 4, ΣTiO ₂ + ZrO ₂ less than 2
or a glass-ceramic precursor glass having a composition of
SiO ₂ 60-72, Al ₂ O ₃ 18-28, Li ₂ O 3-6, Σ Na ₂ O + K ₂ O 0.2-2, Σ MgO + CaO + SrO + BaO less than 6, ZnO 0-1 , 5, B ₂ O ₃ 0 to less than 4, SnO 0.1-1.5, ΣTiO ₂ + ZrO ₂ less than 2, P ₂ O ₅ 0-3, F 0-2.

exemplary embodiments The invention will be explained in more detail with reference to the drawings. It demonstrate:

1 a section through a Floatbadgehäuse and a Drossbox,

2 a section along the line II-II through the in 1 shown throttle box,

3 an enlarged view of the transition region between Floatbadwanne and Drossbox and

4 a plan view of the in the 3 shown cooling device with utilities.

In the 1 is a float bath housing 1 shown schematically, in which a Floatbadkammer 2 is arranged. Inside the float bath enclosure 1 there is a Formiergasatmosphäre with the pressure P _F. In the lower area is the Floatbadwanne 3 with the metal bath 4 , which usually consists of liquid tin. In the left part of the Floatbadgehäuses 1 becomes the glass melt 5 on the metal bath 4 infused and there to a glass ribbon 6 formed, the Floatbadende through the discharge opening 7 in a so-called Drossbox 10 is introduced. Inside the Drossbox 10 there are rollers 16 which are also known as lift-out scooters. By means of these rollers 16 becomes the partially solidified glass ribbon 6 from the metal bath 4 lifted and fed to other processing stations (not shown).

The Drossbox consists of an upper housing part 11 and a lower housing part 12 , The room above the glass band 6 is in the illustration shown here in 3 zones 14a , b, c split. The separation of the individual zones 14a , b, c takes place by means of curtains 15 coming from the upper housing part 11 hang down and a slight distance in cm range to the glass ribbon 6 exhibit. As a result, a sealing effect is achieved, which largely prevents the outflow of gas from one to the adjacent zone.

In the lower housing part 12 are the rollers 16 with their scrapers underneath 17 , These scrapers also subdivide zones in the lower area that do not necessarily have to match the zones in the upper housing part.

Both in the upper housing part 11 as well as in the lower housing part 12 are gas injectors 21 arranged, being in each zone 14a , b, c only one gas injector is shown for reasons of clarity. In the lower area there are two gasin projectors 21 in the area between the rollers 16 ,

These gas injectors 17 are part of a gas inlet device 20 schematically in the 2 is shown.

The 2 shows a section along the line II-II through the in 1 shown Drossbox 10 , This gas injectors 21 extend across the Drossbox 10 and consist essentially of a tube with gas outlet openings 22 , In the 2 are both above the glass band 6 as well as under the glass band in each case a gas injector 21 shown. These gas injectors 21 are via supply lines 23 to a gas supply device 30 connected, which promotes the required amount of gas into the gas injectors, so that within the Drossbox 10 an overpressure relative to the Floatbadgehäuse can be generated. The pressure P _D within the Drossbox 10 is about 0.3 to 06 mbar above the atmospheric pressure P _F Floatbadgehäuses.

The gas supply device 30 is a gas heater 31 upstream, with the gas tank 32 communicates. About the gas heater 31 the gas is heated to a temperature of 600-700 ° C.

In the 3 is the end of the float bath tub 3 shown enlarged. The end-side end wall 8th is with a cooling device 40 equipped in the 4 can be seen schematically in a sectional view. It is a kind of metal bag into which gas is introduced.

In the in 4 As shown, this cooling device consists 40 from two chambers, in the bottom gas from a gas tank 32 is initiated. Within the bag labyrinth-like passages are provided, so that the gas has a sufficiently large residence time to the end wall 8th to cool and to warm up on this occasion accordingly. The heated gas flows via lines 41 to the gas heater 31 where the already preheated gas is brought to the final temperature of 600-700 ° C. Thereafter, the gas enters the gas supply device described above 30 and is over the supply lines 23 the gas injectors 21 fed.

1

Floatbadgehäuse

2

Floatbadkammer

3

Floatbadwanne

4

metal

5

molten glass

6

glass tape

7

discharge

8th

end-side bulkhead

10

Drossbox

11

upper housing part

12

lower housing part

13

inner space

14a, b, c

Zone

15

curtain

16

roller

17

Abstreiter

20

Gaseinleiteinrichtung

21

injector

22

Gas ride opening

23

feed

30

Gas supply means

31

Gasaufheizeinrichtung

32

gas tank

40

cooling device

41

management

Claims (8)

Drossbox ( 10 ) with a housing from an upper housing part ( 11 ) and a housing lower part ( 12 ) and with an in-housing lifting device with rollers ( 16 ) for horizontal transport of a in a Floatbadgehäuse ( 1 ) produced glass ribbon ( 6 ), characterized in that a device ( 20 ) is provided for introducing a gas, the at least one in the interior ( 11 ) of the Drossbox ( 10 ) arranged gas injector ( 21 ) and a gas supply device ( 30 ) to which the gas injector ( 21 ) and whose gas delivery rate is 200 to 400 m ³ (i.N.) / h. Drossbox according to claim 1, characterized in that at least in the upper housing part ( 11 ) in the space above the rollers ( 16 ) at least one gas injector ( 21 ) is arranged. Drossbox according to one of claims 1 or 2, characterized in that in the lower housing part ( 12 ) at least in the space between the rollers ( 16 ) at least one gas injector ( 21 ) is arranged. Drossbox according to one of claims 1 to 3, characterized in that the gas injector ( 21 ) parallel to the rollers ( 16 ) extending tube with gas outlet openings ( 22 ). Drossbox according to claim 4, characterized in that both pipe ends of the gas injector ( 21 ) with the gas supply device ( 30 ) are connected. Drossbox according to claim 5, characterized that the tube is divided into two chambers. Drossbox according to one of claims 1 to 6, characterized in that the introduction device ( 20 ) to a gas heating device ( 31 ) is sen. Drossbox according to claim 7, characterized in that the gas heating device ( 31 ) a cooling device ( 40 ) of the end Floatbadwand ( 8th ).