JPS5837255B2 - Method and apparatus for homogenizing and fining glass - Google Patents

Abstract

1514317 Homogenizing or refining glass SAINT-GOBAIN INDUSTRIES 11 Aug 1975 [14 Aug 1974] 33381/75 Heading C1M Molten glass is homogenized and/or refined by heating the glass so that its viscosity is not more than 1000 poises, foaming the molten glass to a volume at least 1À5 times its original volume, and maintaining the viscosity at not more than 1000 poises until the foam collapses. Preferably the glass is foamed by a gas-generating agent (e.g. Na 2 SO 4 ), the molten glass being heated at at least 20‹C. per minute. The foaming may be aided by ultrasonic vibrations. Preferably, solid vitrifiable material in granular or agglomerated form is passed to inclined duct 14 via furnace 13, in each of which the material is melted by burners 20 and 21. Gases from burners 20. 21 pre-heat the solid material in heat exchanger 23. Furnace 13 and duct 14 are cooled through tubes 17. The molten material formed is passed to channel 1 formed of Pt-Rh alloy, and surrounded by alumina insulation material 12. 12a. The molten material is heated, by Pt-Rh electrode 2 (which may be water-cooled) and by Pt-Rh immersed resistance electrode 10, at at least 20‹C./minute so that the molten glass is foamed and collapses before being delivered through tube 6. In a preferred embodiment granules are heated to 1300‹C. in 6 minutes, from 1300‹C. to 1500‹C. at 30‹C./minute, and held at 1500‹C. for about 10 minutes. In an alternative embodiment (Figures 3 and 4, not shown) the channel is supplied with molybdenum electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the fining and/or homogenization of molten glass materials, specifically to obtaining molten glass having a quality that satisfies the requirements of the glass industry by a rapid and flexible method. This is related to p.

For example, this can reduce the time required to produce purified molten glass suitable as glass shaped article material from the material to be vitrified to as little as an hour.

Facilitates the homogenization and fining of glass, especially the removal of non-melting materials and air bubbles, which are generally the main factor limiting the production speed of industrially used glasses, which usually takes 24 hours or more. This is desirable.

The present invention involves homogenizing and/or refining the glass by bringing it to a temperature such that its viscosity does not exceed iooo poise and generating gas by decomposition of at least one gas generant present in the glass. The gas generation rate is such that gas is generated throughout the entire volume of the glass and the volume of the glass increases by a factor of at least 15, and the viscosity of the glass is then adjusted to such a rate that the gas evolution subsides and the gas The present invention provides a method characterized in that the value is maintained at a value not exceeding 1000 poise until a glass free of poise is obtained.

One or more gas generators are added to the glass material to be treated in order to effect foaming.
gent) or gasogenic foaming agent (gasogenic
foaming agents), ie substances that release gas at the required temperature, are mixed in.

In fact, for this purpose it is advantageous to use the usual clarifying agents, such as sodium sulfate;
This is because, as in the case of well-known glass manufacturing methods, optically good quality glass can be obtained.

Such fining agents also form air bubbles inside the glass at temperatures corresponding to the above-mentioned viscosities, whereas after most of the gas has been removed from the glass, the remaining air bubbles form during cooling of the glass ( This is reabsorbed.

It is desirable to achieve strong and complete foaming, which is generally achieved by rapid heating, distributed as evenly as possible throughout the material, giving a temperature rise rate of at least 20° C. per minute. Ru.

For this purpose, various heating means acting on the center of the glass lump,
For example, a submerged burner, an electric heater with a submerged resistor emitting Joule heat, or also high-frequency induction are optionally used.

In discontinuous melting plants, these powerful heating means ensure that the glass mass still contains a large proportion of solid or gaseous cell nuclei and a sufficient amount of blowing agent such that the volumetric expansion due to foaming is at least 15. The moment this condition is reached, the operation is started and the heating operation is continued until the expansion coefficient is at least 15, preferably 2 to 3 f.

In this case, the above temperature is maintained until the bubbles subside;
The required time is 15-20 minutes.

In a factory that carries out the special refined molten glass manufacturing method according to the present invention in a continuous manner, the glass gob is heated by the same heating means as in the case of the non-continuous method for the same amount of time as described above, but in this case, the glass gob is As the heat treatment flows along the flow path, the flow position and flow rate (thus the heating is adjusted accordingly).

In such continuous manufacturing plants, there is a
It is desirable to prevent the occurrence of flows from downstream to upstream.

This backflow is often of thermal origin and tends to cause mixing in the glass flow mass, resulting in uneven product.

To avoid this undesirable phenomenon, for example chicanes, weirs, constrictions or even waterfalls are provided along the heat treatment flow path of the glass gob, where gravity plays an important role in the movement of the material.

It is advantageous for the width of the groove through which the molten material flows to be small compared to its length, for example in a ratio of 1:5 or less.

The thickness of the material flowing through the groove is also an important parameter.

The thickness of the glass material flowing through the grooves in the examples described below is 4 to 7 CrfL.

For large devices, the side walls of the groove should be 10 to 20 mm thick, sufficient for the thickness of the material during expansion, and also to avoid backflow.
It is appropriate to rub at a height f of cm or more.

In order for the foaming to take place simultaneously over the entire thickness of the glass gob, it is advantageous for the glass gob to contain a large proportion of the nuclei that can lead to the above-mentioned foaming, such as solid particles of unfused material or small air bubbles.

For example, glass waste, especially colored ones, is suitable as the externally added core.

The process according to the invention requires that a gas-generating foaming agent, preferably foaming nuclei, be present in the glass mass to be treated, which is particularly good for molten glass produced in a very coarse state. This applies.

When small grains from calcium carbonate or dolomite with a particle size between 1 and 2 are added to the melt in a clarifier, they will completely dissolve and disappear after about 15 minutes, which is the duration of the foaming phase. It recognized.

Thus, in the case of the method of the present invention, it is not necessary to use high-quality bulk glass material, melting means with high heat outputs not normally used in the glazing industry can be used, and the process can be carried out in a rough manner. The residence time of the barbs is short and the same advantages as mentioned above are obtained.

In the glass manufacturing method according to the present invention, it is desirable to use the starting material to be vitrified after agglomeration treatment.

The effect of this agglomeration process is that the material to be vitrified is preheated prior to being melted.

This preheating advantageously provides intense heat transfer in a short period of time while keeping the material below the onset temperature.

This retains a significant portion of the unmelted material and air bubbles in the glass gob, which is useful for the next step of foaming.

This rapid heating of the agglomerated starting material can be achieved by various means, especially injected into the powdered material at a controlled temperature and at high velocity.

This is achieved by using high-temperature gas with a large heat exchange capacity.

The material granules are preferably introduced directly into the hot gas stream to maximize the velocity of the gas with respect to the material to be heated, and it is advantageous for the material to be heated to flow slowly in a thin layer. .

This can be achieved by injecting high-temperature gas in a direction substantially perpendicular to the slope on which the material particles fall.

The powder layer easily sticks to this inclined surface and is therefore brought very quickly (in about a few minutes) to the glass lump state described above, especially in the total foam process.
rm1ng treatment).

The surface on which the melting takes place in a thin layer may be the inner wall of a cyclone, a rotating drum equipped with a rake for removing the molten glass gob, or an inclined surface along which the glass gob flows as it takes its shape.

The flow velocity over this surface can be adjusted by the angle of the surface, the temperature which influences the viscosity of the molten mass, and thus the adhesion of the granular material to this surface or the direction and temperature of the gas jet.

Next, the present invention will be explained in detail with reference to the accompanying drawings Q with reference to embodiments.

FIG. 1 shows an embodiment of the device according to the invention.

In the groove 1, the molten glass material flows from the right to the left in the figure, and after foaming occurs during the flow, the homogenized and clarified molten glass is removed.

The cross-sectional view of the fining groove is shown in Figure 2.
It is made of platinum alloy sheet with a thickness of 0.7 mounds containing 0%.

The length of the clarification groove is 1.5m, and the width and depth are each 15m.
(It is m.

Terminal 2, which has one terminal at each end of the clearing groove, can adjust the voltage from O to 10 volts, and has an output of 25 tiles (maximum 250 OA).
Receives current supply from C generator 3.

Both terminals 2 have a thickness of 10 threads, a length of 20 cm, and a height of 10 Cr/
It is a plate made of l platinum/rhodium alloy.

Both terminal boards are equipped with circulating water (this equipment is not shown)
It is held between the two jaws 4 which are thus cooled, and a current lead wire 5 is fixed.

A conduit 6 for taking out the molten glass is attached to the bottom of the groove by welding, and a platinum/rhodium alloy resistance wire wound on an insulating tube covering the conduit 6 is heated thereby.

A valve with a platinum/rhodium alloy needle 8 (thus allowing the lower end of the conduit 6 to be progressively occluded).

In the trench, a barrier also made of platinum/rhodium alloy is welded to the soil wall of the trench upstream near the conduit 6, and 20 mm from the bottom of the trench.
The channel 9a is shaped so that the glass melt flows freely up to a height of 1.0 mm.

A resistor 10 made of a platinum/Rodium alloy plate is sunk in the other end of the groove.

This thickness is 0. 7 mm, width 20 cm. It is bent in a U-shape to approximately follow the internal profile of the groove.

The lower end of this resistor is drilled with regularly distributed holes, the dimensions of which reduce the width of the current passage by about 25%, localize the dissipated power, and reduce the size of the glass block. It is considered to help improve mixing during the foaming period.

An AC generator (voltage 2 to 3
Volts, adjustable: power 5) - Current is supplied from Figure 2-.

The refining groove 1 is surrounded by insulating walls 12 to 12a made of alternating alumina bricks and unsealed insulating bricks.

The unsealed insulating bricks serve to controllably leak heat to better control the temperature distribution in the material flowing along the grooves.

From its upper end, the fining channel 1 is fed with molten glass material formed in a melting furnace 13 through a conduit 14 with an inclined bed 15 .

The bottom of the melting furnace is also made sloped.

Below the bottom (15 and 16) a plurality of steel tubes 17 are arranged in one direction perpendicular to the plane of symmetry of the device.

These steel pipes 17 carry a coolant whose flow rate can be controlled to adjust the temperature at the bottom.

The conduit 14 and the ceiling walls 18 and 19 of the furnace 13 are each covered with insulating brick.

The furnace 13 and the conduit 14 are connected to a second one by a gas burner 20, one of which passes through the ceiling wall and points perpendicularly to the corresponding bottom.
There is a burner that penetrates the chimney bottom 22 of the furnace, and the flame flows into the chimney 2.
a gas burner 21 oriented towards the falling zone of the vitrifiable material particles introduced through 2 into the bottom 16;
heated by.

These burners are of a type known to be powerful, i.e. the gas injection velocity is used to deflagrate the fuel mixture.
A type of combustion engine is used in which the combustion speed is higher than the fragration velocity, and the flame is therefore delayed and burns in a combustion chamber formed by the ceiling wall.

These burners are supplied with a mixture of propane, air and/or oxygen, for example from a mixer (not shown);
Generates 600,000 calories per hour.

The high-temperature gas escapes from the bottom up through the chimney 22 and into the heat exchanger 23.
The glass material mixture flows countercurrently through the heat exchanger with the previously agglomerated glass material mixture falling by gravity.

The gases discharged from the heat exchanger and the gases discharged directly from the chimney 22 through the bypass 24 are sent to a cyclone to remove dust.

Gas is discharged from here by a ventilator 26.

The heat exchanger 23 is made of heat-resistant steel and, as shown in FIG. 1, is double walled with a powdered thermal edge material, such as diatomaceous material.

The agglomerated starting material to be vitrified is preheated in a heat exchanger 23 and then introduced into the furnace in a drum distributor 27.

In this case, the feed rate of the starting material to the furnace is regulated by the rotational speed of the furnace.

Next, melting and clarification operations of the above-mentioned homogenization and/or clarification apparatus will be explained using examples.

For this run, a ribbon compacted to a diameter of 7 mm by an extrusion press was used as the agglomerated starting material described above.

Example The composition of the materials to be vitrified to obtain 90 kg of glass products is as follows.

Sand (250 μm) 60 ky Calcium carbonate (100 μm) 8.5k9
Do07ite (<lim) 1 4.5
kg feldspar (500 μm) 5.5
kg dense carbonated soda 6.8
kg caustic soda solution (50% soda hydroxide) 20.
2kg powdered sodium sulfate 0. 9
The kg powder is dried by passing it through a ventilated electric oven at 250° C. and stored without taking up moisture, in which case no special precautions are required.

The grain powder is supplied from above to the heat exchanger 23 while being cold,
It flows down by gravity while being gradually heated, and the temperature rises to 500 to 600° C. near the drum type distributor 27.

At the same time, high-temperature gas mixed with the cold air that entered through the holes 28 and adjusted to 750°C is introduced into the heat exchanger.
There, after being cooled to 200° C., it is sucked into the cyclone 25.

The powder falls directly to the bottom of the furnace by means of a distributor 27 in a zone where the flames from each burner 21 are concentrated.

It then rapidly transforms into a molten glass mass that sticks to the furnace bottom and flows along it at an average speed of 10 CrrL/min.

The temperature of the molten mass reaches its target temperature of 1300° C. near the conduit bottom 15 and moves quickly due to the steep slope of the bottom 15.

Heating continues up to the entrance of the fining groove 1.

Corrosion phenomena (corrosion and erosion) on the bottoms (15 and 16) are negligible since the surface temperature of each bottom is limited to about 800° C. by circulating cooling liquid in each tube 17.

On the other hand, the temperature of the ceiling walls in these zones of the furnace is approximately 1450°C.

The molten glass that falls into the clarification groove 1 comes into contact with the groove bottom and side walls,
It also comes into contact with the submerged electric resistor 10 and is further rapidly heated by both conduction and convection, and the temperature reaches approximately 1530°C.
'C maintained.

For example, if the hourly glass supply is 52 kg, the amount of power dissipated from the channel walls is 20 KVA and that from the submerged resistor is 4 KVA.

While the molten mass passes near the electrical resistor 10, it is rapidly heated, resulting in foaming and therefore expansion, even though the thickness of the molten mass layer is approximately 4 crfL upstream of the immersed electrical resistor. On the other hand, on the downstream side, it becomes about 14CrI'L.

A sample was taken and inspected at the bottom of the trench immediately downstream of the immersed resistor 10, and it was found that the glass lump was completely foamed.

When the temperature downstream of resistor 10 is about 1520 DEG C., the flow distance is approximately constant over about 1 rrL - which corresponds to a flow time of about 15 minutes.

Then, at a flow distance of 10-15 cIrL, the bubbles subside rapidly and the glass mass assumes the appearance of completely clear glass in the vicinity of the barrier 9.

The temperature at this time is only about 1450°C.

The clarified glass passing under the barrier is removed through conduit 6, the flow rate of which is regulated by valve 8 so that the level of molten material in the channel remains approximately constant.

In the embodiment described above, the time required from the time the preheated powder material falls into the bottom 16 of the melting furnace until it is removed from the conduit 6 as clear glass is only about 3.
It's only 0 minutes.

It has been found that the apparatus described above can increase the production rate of clear glass by proportionally reducing the degree of foaming, without changing its dimensions.

In this case, the material to be vitrified is in the above-mentioned composition, with an amount of powdered sodium sulfate of 0.000 kg per 100 kg of glass to be produced. It was reduced to 7 kg.

Under these conditions, the initial height of the molten mass downstream of the submergence resistance 10 rose to 7 cIrt, but the highest liquid level after complete expansion remained at a height of 14 crIL.

This corresponds to an expansion index of 2.

Also, given the course of temperature rise and the composition of the material to be vitrified (in particular the sodium sulfate content), whether a discontinuous or continuous process is chosen, the necessary It was acknowledged that there was no substantial change in the duration of operation.

The Applicant has also observed that during the tests the foaming can be initiated or intensified by mechanical action, for example an ultrasonic generator.

By foaming the entire glass lump, it has been observed that the melting process is accelerated and the molten glass is clarified and homogenized, but these effects have not been known until now.

The foaming process can be applied to glasses of various strengths, thus providing significant savings in time and energy consumption and operational flexibility in the glass manufacturing process.

Tables 1 to 2 summarize production examples of five types of ordinary glasses produced by the method of the present invention.

Table 1 shows the analytical values of these glasses in terms of weight percentage of oxides.

Glass. No. 41 was obtained by melting in the above example.

Table 1 is a set of five weights of mixture materials to be vitrified suitable for the production of the various glasses shown in Table I.

Table (1) shows the processing characteristics of the material to be vitrified from mutual melting to complete melting.

Figures 3 and 4 show a refining crucible in which glass is heated by the Joule effect.

This crucible is equipped with molybdenum electrodes and has the advantage of being economical to operate, although it is not suitable for certain glasses, such as the lead glasses of Examples 3 and 4.

This crucible had a rectangular cross-section with an internal dimension of 25CrfL and consisted of a refractory groove 30 with a length of 2m.

The downstream part forms a constriction 31 with a raised bottom of about 5 CrIl and whose width is reduced to a few, so that no blind spots are created, so that the glass can pass through the distributor without forming stagnation zones. 33.

The bottom, side walls and ceiling walls (not shown) of this channel are an electrofused material based on alumina and zirconium oxide, similar to that commonly used in conventional glass melting furnaces.

The jacket 34 is made of brick, a lightweight refractory material, and serves as a thermal insulator.

The glass is heated while flowing along the groove, and this temperature regulation is achieved by electrodes E1 each consisting of plates 3crIl wide, arranged symmetrically and on both sides with respect to the axis of the groove, as shown in both figures. ~E6.

Each pair of electrodes is connected to a power source whose current can be adjusted independently.

The electrode is also made of molybdenum, and the leads to this electrode pass horizontally through the groove wall and are fixed exactly perpendicular to the electrode surface.

The thickness of the glass on the diffuser 33 is sufficient so that the electrodes are completely submerged, thereby preventing oxidation.

The current leads are protected by covering their hot paths with a reducing electric field, for example that of city gas.

The glass is allowed to pass freely around the electrodes along the bottom and side walls.

Thus, the flow from one electrode to the other causes active thermal convection, which suppresses the large longitudinal flow and favorably influences the homogenization of the molten material due to the flow in the transverse force direction: C.

This results in a uniform flow of glass gobs known as "piston flow".

Temperature measurements are taken at each point T1-T7.

Table 2 shows that the molten glass gob obtained by pre-melting the same composition and material under the same operating conditions as in the above-mentioned example was 1
Approximately 50 kg to point T1 of the crucible at 250-1300°C
The power supply amounts and temperature conditions applied when supplied at a flow rate of /hour are summarized.

The embodiments of the present invention are as follows.

1. 2. The method according to claim 1, wherein the glass generation rate is such that the volume of the glass is rubbed 2 to 3 times.

2. The method described in item 1 above, characterized in that the gas generating agent is dissolved in the glass material.

3. The gas generating agent is arsenic, antimony, sulfur f. = is a halogen-containing compound {the method described in item 2 above).

4. Claim 1 characterized in that the solubility of the gas forming the bubbles in the molten material increases as the temperature decreases.
and the method described in any one of the preceding items.

5. 2. A method as claimed in claim 1, characterized in that the molten mass is heated to said temperature at a rate of at least 20'C per minute.

6. The method as claimed in claim 1 and any one of the preceding claims, characterized in that the molten mass contains solid or gaseous foaming nuclei distributed throughout it.

7. 4. A method according to item 4, characterized in that the foaming nuclei are distributed throughout the molten mass at a density of at least 10 foaming nuclei per molten mass.

8. Item 6 or 7 above, wherein the glass material containing solid or gaseous foaming nuclei is produced by uniformly heating a solid glass material mixture and melting it at a rapid rate. The method described in.

9. 9. The method according to item 8, characterized in that the glass material mixture is rapidly melted by heating within 10 minutes.

10. The solid material to be vitrified contains part of its grains or agglomerates, and some of them segregate during heating.
9. The method described in item 8 or 9 above, characterized in that the method does not cause gregation.

11. A method according to item 10 above, characterized in that the material to be vitrified is melted to form a thickness of molten material having the thickness of the smallest dimension of the granules or nodules.

12. A method as claimed in claim 1 and any of the preceding claims, characterized in that the molten vitreous material flows along the groove without substantial backflow.

13 Diameter is 0. 5 to 1 cx, length 1 to 5 CT
l of granules with the following composition (weight for 90 kg of glass): Sand (250 μm) 60 kg Calcium carbonate (100 μm) 8.5 kg DoO? Ih (<
1mm. ) 1 4.5kg feldspar (50
0μm) 5.5ky high density (dense)
Carbonated soda 6. 8 kg caustic soda solution (50
%) 20.2kg powdered sodium sulfate
0. Approximately 6 kg of glass material mixture with 9 kg
Heat to 1300℃ per minute, then heat to 1300℃ at a rate of 30℃ per minute.
C. to 1500.degree. C. to expand the resulting glass gob as bubbles, and the temperature of the glass gob is maintained at 1500.degree. C. for about 10 minutes until separation of the refined glass is achieved. Range 1 and the fall of the above items 1 Q The method described above.

14. A method for homogenizing and/or clarifying a molten mass of glass material substantially as described above with respect to FIGS. 1 and 2 or 3 and 4 of the accompanying drawings.

15. A method for homogenizing and/or refining a molten mass of glass material substantially as described above for the Examples.

16, wherein the horizontal groove comprises molybdenum electrode(s) submerged in the molten material and used to allow electrical current to flow through the molten material, the electrodes being spaced apart along the sidewalls of the horizontal groove. An apparatus according to claim 2.

17. Apparatus for refining and/or homogenizing molten glass material substantially similar to that described above with respect to FIGS. 1 and 2 or 3 and 4 of the accompanying drawings.

18. ! 4? Claim 1 and Items 1 to 1 above
Gaffus clarified and/or homogenized by the method as defined in any one of clauses 5 or by the apparatus as defined in claim 2 and above in clause 16.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram including a partial vertical cross-sectional view of a facility equipped with the device according to the present invention, Fig. 2 is a cross-sectional view taken along the line n-■ of Fig. 1, and Fig. 3 is a schematic diagram of a modified embodiment. A partial plan view and FIG. 4 are longitudinal sectional views taken along the line IV-IV in FIG. 3. 1...Groove, 3...AC generator, 6...
...Conduit for taking out molten glass, 10...
Resistor, 1 2, 1 2a...Insulating wall, 13
... Blast furnace, 14 ... Conduit for molten glass material formed in the blast furnace, 23 ... Heat exchanger,
26... Ventilator.

Claims (1)

[Scope of Claims] 1. The glass is heated to such a temperature that its viscosity does not exceed 1000 poise and gas is generated by decomposition of at least one gas generating agent present in the glass, the glass is homogenized and ( or) in a method of fining, the rate of gas evolution is such that gas is evolved everywhere in the total volume of the glass and the volume of the glass increases by at least 1.5 times, and then the viscosity of the glass is adjusted to A method characterized by maintaining the value not exceeding 1000 poise until the bubbling subsides and a gas-free glass is completed. 2 Bringing the glass to a temperature such that its viscosity does not exceed iooo poise, generating gas by decomposition of at least one type of gas generating agent present in the glass, and controlling the rate of gas generation so that the gas covers the total volume of the glass. The rate is such that bubbles occur everywhere and the volume of the glass increases by at least 1.5 times, and then the viscosity of the glass is maintained at a value not exceeding 1000 poise until the bubbling subsides and a gas-free glass is obtained. a substantially horizontal, electrically heatable groove 1, 30, immersable in the vitreous material in said groove and raising the temperature of said vitreous material at a rate of at least 20°C per minute; electrical heating device 10, E1, E2 to obtain;
a device 13 for supplying the glass material to one end of the groove, the furnace comprising a furnace for initially melting a portion of the glass material to form a thin layer of the molten material; The furnace has a duct 14 with an inclined bottom 16, 17 and at least one fuel bar 20 arranged to emit a flame towards the inclined bottom p, the duct of the furnace containing granular or nodular material. The supply silo is connected to a feed silo which feeds the fraction of vitreous material by gravity, and at least one fuel burner 21 is connected to a supply silo which feeds the vitreous material by gravity, and at least one fuel burner 21 is arranged to provide a flame in the path of the drop of the vitreous material from the supply silo to the duct of the furnace. A device for homogenizing and fining glass, characterized in that it is directed at