US3507637A - Method and apparatus for controlling the flow of the furnace gases - Google Patents

Description

Apnl 21, 1970 5. JAVAUX 3,507,637

METHOD AND APPARATUS FOR UONTROLLlNG THE FLOW OF THE FURNACE GASES I Filed May 4, 1966 4 Sheets-Sheet 1 FiG.1.

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OF THE FURNACE GASES- Filed May 1. 1966 4 Sheets-Sheet 5 FiG.5

INVENTOR Gustave Jovuux jg owwe 9 1101414 ATTORNEYS April 21, 1970 G. JAVAUX 3,507,637

METHOD AND APPARATUS FOP-CONTROLLING THE FLOW I OF THE FURNACE GASES Filed May 4, 1966 4 Sheets-Sheet 4.

INVENTOR Gust ove Jovcux 8 ha e ATTORNEYS United States Patent Int. Cl. cosh 5/00 US. Cl. 65-32 16 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for use in glassmaking in which a non-oxidizing atmosphere must be provided and maintained. At the openings of the furnace either within the openings or exteriorly thereof, currents of air are provided to cause aspiration of the protective gas in a direction exteriorly of the furnace. The aspiration of the protective gas outwardly through the openings prevents the entry of air into the furnace. The currents of air are caused to be in a direction at a right angle to the wall in which the opening is formed and in certain embodiments the means for providing the air current can be moved so that there can be easy access to the interior of the furnace through the opening.

The present invention relates generally to melting furnaces such as are used in the glass-making industry, and more particularly to a method'and apparatus for preventing the penetration of oxygen into such melting furnaces and especially into the working end thereof through openings in the furnace which communicate with the atmosphere surrounding the furnace.

Generally, in furnace installations for the making and treating of flat glass on a bath of molten metal, the molten metal must have a melting point which is comparatively low and for this reason, tin is the metal which is most frequently used. Unfortunately, this metal is extremely oxidizable and particularly in the liquid state and this represents an undesirable property since the oxide particles which are produced tend to float on the surface of the bath and adhere to the glass which results in glass of an inferior quality being produced.

Various proposals have been made for preventing the oxidizing of the molten metal with the process most frequently used being that of maintaining the molten tin within the furnace in an atmosphere which is free of oxygen and other oxidizing gases under the normal operating conditions of the furnace. For example, a nitrogen atmosphere containing a small percentage of hydrogen as a reducing gas is frequently used. Moreover, the oxygenfree atmosphere within the furnace is maintained under a slight excess pressure with respect to the atmosphere of the air surrounding the furnace for preventing the air from entering the furnace and contaminating the inside atmosphere since the furnace is not air tight.

In spite of such precautions, the bath of molten metal is still subjected to oxidization because it is not possible to have a furnace which is completely sealed. On the contrary, the furnace must be provided with openings for introducing the glass into the furnace and extracting it from the furnace and with other openings which, for example, serve for introducing tools into the furnace and for working such tools. Although the pressure inside the furnace is greater than the atmospheric pressure which surrounds the furnace, oxygen may still penetrate into the furnace through the openings and thus diffuse into the gaseous atmosphere within the furnace. Even when the "ice oxygen-free atmosphere within the furnace forms a uniform fiow out of the furnace, the speed of the flow must be such that the oxygen does not diffuse into this flow and thus enter the furnace.

It is readily apparent that the pressure within the furnace cannot be, in practice, maintained everywhere at a value which exceeds the atmospheric pressure outside of the furnace and therefore the flow of the oxygen-free gas, hereinafter referred to as neutral gas, emanating from the openings in the furnace is not sufficient to prevent the oxygen from entering the furnace as described above. Since the furnace or its working end is provided with openings having dimensions which vary considerably, the consumption, i.e., the outflow of the gas would be greater at the larger openings. For example, the opening through which the glass strip after having been treated by the molten metal bath passes when it leaves the furnace, is of a large size when compared with an opening in the wall of the furnace having a tool passing therethrough. Thus, the pressure of the oxygen-free atmosphere within the furnace or at its working end which slightly exceeds the surrounding atmospheric pressure must then be maintained at a value which is proportional to the largest opening. However, when considering the smaller openings, such pressure value is too high and effects a high speed neutral gas flow through such openings with a resultant excessive consumption of the neutral gas introduced into the furnace.

It is therefore an object of the present invention to provide for melting furnaces a method and apparatus which overcome the disadvantages of the prior art.

It is another object of the present invention to prevent oxygen from entering the non-oxidizing atmosphere within the furnace or the working end thereof through openings in the furnace.

It is a further object of the present invention to provide a suitable low pressure level for the non-oxidizing gas contained within the furnace and an acceptable consumption level for such gas.

In accordance with the present invention, a neutral gas flow emanating from the furnace is formed in the openings of the furnace by, in the region of these openings, blowing a gaseous fluid in a direction away from the furnace. The thus formed neutral gas flow is advantageously directed in a direction which is approximately perpendicular to the wall having the opening therein.

The arrangement for carrying out the process according to the present invention includes a device arranged for cooperation with the openings in the furnace for blowing a gaseous fluid in a diverging direction away from such opening. The gaseous fluid may advantageously be air, but may also be any suitable gas or steam. in accordance with the present invention, the blowing device comprises a system of pipes having holes therein so as to form jets for emitting the gaseous fluid. Generally, the system of pipes is arranged in a path corresponding approximately to the periphery of the opening and serves for partially obstructing the opening.

According to a preferred embodiment of the present invention, if the opening is of a comparatively large size, at least two concentric pipe systems are used so as to cover much of the opening. Moreover, an iron sheet member is advantageously used for closing the space existing between the pipe systems so as to provide the smallest possible opening which is still sufficient for permitting the passage of a tool or a glass strip. A similar result is obtained by replacing the sheet members and pipes with a box provided with a plurality of drilled holes, each of which form a jet.

The blowing device is generally placed within the opening, but it may be advantageously placed outside the opening at the working end of the furnace. This particularly applies to the opening through which a glass strip treated by the bath of molten metal is passed. In accordance with a preferred embodiment of the present invention, for a blowing device on the exterior of the furnace, the parts of the blowing device form the front portion of a boX which is open on the side facing the furnace and having side walls contacting the wall of the furnace surrounding the opening. It should be noted that such an opening is larger than the opening required for passage of the glass strip and must be of the size which is sufficient for introducing tools into the working end of the furnace.

In accordance with a feature of the present invention, the blowing arrangement includes a movable portion which may be removed from the opening so as to permit access to the working end of the furnace. The movable portion may, for example, be pivotably mounted so that it may be swung out of the opening. Also, the blowing arrangement is advantageously provided with guide members for directing the gaseous fluid toward the portion of the Opening which is not obstructed by the blowing arrangement.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a partial schematic view in longitudinal section of the working end of a melting furnace for treating fiat glass with a bath of molten metal.

FIGURE 2 is a cross-sectional view of the working end of the furnace having an opening through which the treated glass strip passes, which opening is provided with a blowing arrangement according to the present invention.

FIGURE 3 is an end view in the direction of the line 33 in FIGURE 2.

FIGURE 4 is an end view of a blowing arrangement according to the present invention which is positioned in a circular opening of relatively large size.

FIGURE 5 is a cross section taken along the line 5-5 of FIGURE 4.

FIGURE 6 shows another embodiment of a blowing arrangement according to the present invention.

FIGURE 7 is an end view of a blowing device for a small circular opening.

FIGURE 8 is an end view of a blowing arrangement according to the present invention for a rectangular opening, this view being taken in the direction of line 88 of FIGURE 9.

FIGURE 9 is a cross-sectional view taken along the line 99 of FIGURE 8.

Referring now to the drawings, there is shown in FIGURE 1 the working end of a melting furnace which is used in the glass-making industry. The furnace includes a bottom member 1, side walls 2, a front wall 3 and a crown 4. As shown, a bath of molten tin 5 is contained 'within the furnace and a glass strip 6 slides on this molten bath and is treated thereby. The treatment may, for example, be a heat polishing of the glass. The glass strip 6 is moved forward by means of rollers 7 and thus passes from the working end of the furnace through an opening 8 in the front wall 3 of the furnace. The walls of the furnace are provided with other openings such as indicated at 9 and 10 which are formed in the side walls 2. Auxiliary devices such as tools which for sake of clarity are not shown, are inserted into the furnace through such openings. As explained above, an oxygen-free atmosphere, generally containing nitrogen, and having a pressure which exceeds the atmospheric pressure surrounding the furnace is maintained within the working end of the furnace.

FIGURES 2 and 3 show the front wall 3 having the opening 8, in vertical section and in elevation, respectively. As shown, above the glass strip 6, the opening 8 is partially obstructed by a box-like structure including a top sheet member 11, side walls 12 and a blowing arrangement having a system of pipes 13, which system is in the shape of a frame and connected to a feed pipe 14, the pipes 13 being provided with orifices 15. The space enclosed by the thus formed frame is covered by a sheet member 16 such as an iron plate which is joined to the system of pipes 13. Sheet members 17 are mounted at the edge of the sheet 16 and extend perpendicularly from such sheet member for guiding the air emitted from the orifices 15 in a direction which is perpendicular to the wall 3 so as to concentrate the action of the air in front of the peripheral portion of the opening which is not obstructed by the blowing arrangement. The blowing arrangement is positioned so as to be in a vertical plane corresponding to the axis of the rollers 7 and is freely suspended by straps 18 connected to the sheet 11 so that the arrangement may be pivoted, for example, so as to provide access to the inside of the furnace. Below the roller 7 and in close proximity thereto, a system of pipes 19 which is connected to a feed pipe 20 is provided with openings 21 and is afiixed to the top edge of a sheet member 22, which member forms with the walls 12, 23 and a removable bottom member 24, a tank for collecting the impurities of the bath which are drawn from the melting furnace by the glass strip. As further shown in FIGURE 2, within this lower portion there is provided a damper 25 which swivels about the axis 26 and serves for closing the tank portion so that the bottom member 24 may be removed for discharging the impurities which have collected thereon.

The operation of the arrangement according to the present invention will be described in connection with FIGURES 4 and 5 which show another embodiment of the present invention for use with circular openings. As shown, there is provided a circular opening 9 in the side wall 2 of the furnace, this opening serves for introducing tools into the furnace and for maneuvering these tools. The opening 9 is generally closed by a door (not shown) and is only opened for working such tools or inserting the same into the furnace. During the interval in which it is open, two removable box-like air pressure members 27 formed in the shape of a half crown and connected to feed pipes 28, each box member having two semicircular concentric rows of orifices 29 and 30, are placed in front of the opening 9. Two box members in the shape of half crowns are preferably used rather than a single member since both members can be placed within the opening 9 without hindering the introduction of a tool 31 into the furnace, the working portion 32 of this tool being larger than the diameter of the handle. Thus, with such an arrangement the two box members 27 may be momentarily separated and then brought back into the desired operating position as soon as the portion 32 has passed through the opening. A crown formed from a single structure could obviously be used with the structure being joined to the handle of the tool 31. However, this type of construction would be less advantageous if the tool has to be replaced.

As shown in FIGURE 5, the air or any other suitable fluid under pressure is introduced into the boxes 27 through the feed lines 28 and is discharged through the orifices 29 and 30 so as to form jets 33 having a coneshaped dispersion pattern. Thus, an extremely smooth air flow is generated near the orifice 9, which flow is directed away from the furnace. The air flow produced by these jets creates a suction effect at the opening such that the oxygen-free atmosphere of the furnace tends to aspirate towards the exterior of the furnace in the form of a regular flow which is schematically represented by the arrows 34. For obtaining the most efficient operation, the

pressure of the air conveyed by the pipe 28 is adjusted to a value which is sufficient for the jets 33 to induce a neutral gas flow 34 at a speed which exceeds the speed at which oxygen diffuses into the nitrogen gas. Thus, the penetration of the oxygen into the furnace is prevented. It is readily apparent that the pressure depends upon the local conditions existing within the furnace and particularly on the shape and dimensions of the opening 9 and thus varies with the dimensions of the opening.

In FIGURE 6, there is shown another embodiment according to the present invention for use with circular openings. However, instead of the air boxes 27 as shown in FIGURE 4, two pairs of concentric semi-circular distributor pipes 35 and 36 having orifices 30 are provided. The outer semi-circular pipe is connected to a feed pipe 37 with the inner pipe 36 being fed by means of a pipe 37 which is also connected to the pipe 35. Each semicircular distributor pipe 35 is connected to the corresponding semi-circular pipe 36 by means of a sheet member 38 which encloses the area between the two concentrical pairs of semi-circular pipes. This type of construction is more simple and of lighter weight than the air box construction and also permits the air to be more regularly distributed when it is ejected from the orifices 30.

The air boxes or the concentrical systems of pipes as described above are generally used with openings of a large diameter. If the diameter of the openings is relatively small, a unique circular distributor pipe 39, as shown in FIGURE 7, having orifices 30 is preferably used. This device prevents the oxygen from penetrating into the furnace if the openings are of a relatively small size.

In FIGURES 8 and 9, there is shown another embodiment of the present invention which may be used with a rectangular opening such as the opening which is shown in FIGURE 1. In this opening two distributor pipes 40 and 41 each form two rows of orifices one row being above the other. As shown, the pipes are positioned in the opening 10 and are connected to feed pipes 42. The pipes form a rectangular frame, with sheet members 43 joining the pipes of each frame so as to provide a closed structure, these sheet members being Welded to the distributor pipes.

Thus, in accordance with the present invention oxygen is prevented from penetrating into the furnace or diffusing into the oxygen-free atmosphere since it is hindered by the air flow created outside of the furnace, which air fiow produces a suction efiectto aspirate a portion of the oxygen-free atmosphere'enclosed within the furnace. Also, as pointed out above, a neutral gas flow toward the exterior of the furnace is generated in the openings thereof and the speed of the flow exceeds the speed at which oxygen diffuses into the neutral gas.

In accordance with a feature of the present invention, the speed of the neutral gas fiow may be adjusted to any desired value irrespective of the size of the opening in the wall of the furnace. This is an important advantage which is not enjoyed by the prior art processes which maintain within the furnace or the working end thereof a pressure which is considerably greater than atmospheric. As such, the present invention permits the flow rate of the neutral gas passing through the openings in the furnace to vary with the size of the opening and thereby permits a suitable pressure level to be maintained within the furnace and the consumption of the neutral gas to be kept at a minimum.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.

What is claimed is:

1. A method for preventing air from pentrating into a melting furnace of the type used in the glass-making industry through an opening in the furnace which contains materials which are adversely affected by oxygen, comprising the steps of:

feeding a non-oxidizing gas into the interior of the furnace to provide an oxygen-free atmosphere within the furnace; and

blowing a gaseous fluid of any composition from the region of the opening in the furnace in a direction away from the furnace at a velocity to cause sufficient aspiration of non-oxidizing gas from within the furnace toward the exterior of the furnace and through the opening of the furnace to prevent oxygen from entering through such opening.

2. The method as defined in claim 1 and further comprising the step of guiding the flow of the gaseous fluid in a direction approximately perpendicular to the Wall having the opening therein.

3. The method as defined in claim 2 wherein the gaseous fluid is air.

4. The method as defined in claim 2 wherein the gaseous fluid is steam.

5. An arrangement for preventing air from penetrating into furnaces of the type used in the glass-making industry through openings within such furnaces which are to contain materials which are adversely affected by oxygen, comprising, in combination:

a section of a furnace having an opening formed through the wall thereof;

means for feeding a non-oxidizing gas into the interior of the furnace; and

means positioned in the region of such opening for blowing a gaseous fluid at a velocity and in a direction outwardly of said furnace to cause sufficient aspiration of such non-oxidizing gas through the opening as to prevent oxygen from entering through such opening.

6. An arrangement as defined in claim 5 wherein said blowing means includes at least one pipe having orifices therein for ejecting the gaseous fluid through such orifices.

7. An arrangement as defined in claim 5 wherein said blowing means includes a box-shaped member having orifices in at least one wall thereof for ejecting the gaseous fluid.

8. An arrangement as defined in claim 6 and further including a plurality of pipes which form a pipe system and sheet members are afiixed to said pipes for enclosing the area between said pipes so as to obstruct the portion of the opening which is not obstructed by the pipe system.

9. An arrangement as defined in claim 5 wherein said blowing means is positioned within the opening in the furnace section.

10. An arrangement as defined in claim 5 wherein said blowing means is positioned on the exterior of the furnace section.

11. An arrangement as defined in claim 5 wherein at least one portion of said blowing means is provided with a shape that corresponds to the opening with which it cooperates.

12. An arrangement as defined in claim 5 and further comprising a box-like structure mounted on the exterior of the furnace section having an opening therethrough, said blowing means forming at least a portion of the front part of said structure, said structure being open on the side facing the furnace section and having members extending from the front part thereof for contacting the wall of the furnace section, so as to completely surround the opening in the furnace section.

13. An arrangement as defined in claim 12 wherein at least a portion of said blowing means is movable in a direction in which it can be removed from the opening with which it cooperates.

14. An arrangement as defined in claim 13, further comprising guide sheet members extending from said blowing means in a direction perpendicular to the wall of the furnace section and mounted on the side of said blowing means which is opposite the portion of the opening which is not obstructed by said blowing means.

15. A method as defined in claim 1 wherein the gaseous fiuid is discharged from within the opening or exteriorly of the opening directly in a direction approximately at a right angle to the wall having the opening therein.

16. An arrangement as defined in claim 5 wherein said blowing means is arranged within the opening or exteriorly of the opening and for directly discharging the gaseous fluid in a direction approximately at a right angle to the wall having the opening therein.

8 References Cited UNITED STATES PATENTS 3,248,197 4/1966 Michalik et al 65182 3,351,451 11/1967 Barradell-Smith et al. 65-99 ARTHUR D. KELLOGG, Primary Examiner US. Cl. X.R.

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