NO753958L - - Google Patents

Description

Title: Method and apparatus for production

of glass melt.

.The invention relates to improved method dg- apparatus for manufacturing? of molten glass mixed with several constituents- Previously has

such glass melts produced by a composition of the materials to be included in the smelting being poured into a glass melter or furnace, after which heat is supplied in sufficient quantity to. the components of the composition must react with each other and form one

mass of molten constituents. It is then homogenized or refined. obtained melt in the melting apparatus to give the desired melt composition

In the case of mass sealing of glass products (production or preparation of molten glass is appropriately a continuous process,

as the melting equipment includes a container for the components of the melt,

and which are supplied, materials to be included in the composition, at a rate which depends on the withdrawal of molten glass from the container. While the melted components are in the melter, they will further react with each other to form homogenized,

molten glass of the desired composition. A typical stay

for these components in a melting vessel that emits 150 tonnes of molten glass per day, amounts to between 24 and 48 hours or longer o. The temperature of the molten components must be kept at a sufficiently low level for the desired reaction to take place with the added components. Molten components that become volatile at temperatures below the established operating temperature for the smelter are removed as well as flue gases. In order to obtain an appropriate molten glass composition for forming, the supplied composition must therefore be compensated for that part of the constituents that is lost through evaporation during the time the material is in the melter.

Repeated glass melting processes therefore limit the molten glass composition to those that only contain components that can survive in the defc environment found in the present glass melting devices. In connection with currently known processes for the production of molten glass with special properties or, shaping possibilities, it is necessary to add to the melting furnace all the components that must be present in the finally obtained glass melt in order for the aforementioned properties or characteristic data to be obtained. The presence of such components in the smelter is, however, in many cases not humane due to the components' volatility, corrosive properties and environmental impact.

Molten glass compositions which are suitable for glass fiber production' thus contain e.g. usually volatile constituents such as isoroxide (B2O.J), fluorine (Fg) and sodium borate (Na20.xB20.j). These components will not only evaporate or change to a volatile phase at the smelter's operating temperature, but the presence of these components in the melting container will also result in a shorter life span for this container due to chemical attack on refractory material.

The invention relates to an improved method for the production of glass melt whose components can be divided into two or more groups in such a way that each group contains components with the same reactive properties. This separation can be carried out on the basis of the vaporization temperature of the constituents or another common gassing property, e.g. corrosive properties or catalytic action'. Classification criteria for a group do not necessarily mean that the constituents in the group are excluded from other groups. If, for example, the present constituents are classified in accordance with evaporation temperature, the temperature interval for a given constituent group can extend into the temperature interval of the nearest lying higher or lower group.Two component groups can therefore comprise one common component.

If the principles of the invention are carried out in connection with the production of a molten glass composition which is suitable for being made into fibres, and which contains silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), calcium oxide (CaO), boron oxide (B 2 O 3 ), fluorine (F^) and sodium oxide (NagO), two material groups can be identified.-. The

particular volatile constituents, namely B 2 O 3 , F 2 and Na 2 O ..x B 2 O 3 are conveniently grouped together as a volatile dxyd group. The remaining components SiO,,, Al 2 O 3 , Na 2 O and CaO can be grouped together as a relatively unvolatile group. In this grouping of components, the non-volatile group will be recognized as soda glass, which is a common glass composition in the glass industry.

In accordance with the method for producing a meltable, fibrable glass composition containing the above-mentioned constituents, the relatively small "volatile group of constituents is conveniently prepared as molten bfisis glass in a glass-melting furnace of the continuous furnace type which is common within the glass manufacturing industry. To this relatively low-volatile, molten base glass composition is then added the so-called volatile constituents--"the group as a molten composition or as a mixture, of solid additive materials. The volatile constituent group can be introduced into the molten ^asis glass composition" on which as .

preferably a suitable location downstream of the melting area for the small

"volatile constituent group. The volatile constituent group is infected

suitably in the base glass sraél immediately downstream of the outlet channel from the base glass melter, whereby advantage is taken of the base glass's output temperature and remaining varrae content. However, the volatile component group can also be supplied directly in the channel area of the base glass melter or at any other appropriate or otherwise advantageous location along the pre-hardener

distribution channel,

In connection with the method of the invention, it will therefore no longer be necessary to mix all the desired components in

a glass composition in a common glass melter that receives all ... constituents in the form of solid additive materials. A less aggressive composition of such materials can be composed especially for melting in the main melter without the need for the restrictions that have previously been conditioned by the molten glass composition that is ultimately to be achieved. Glass melt can now be modified to a significant degree downstream of the glass's main melting area, whereby a molten glass composition with different properties or different forming conditions is achieved.

The invention will now be explained in more detail with reference to,

the attached drawings, on which:

Fig.- 1 shows a typical process for forming glass fibers according to

to the invention;

Fig. 2 is a perspective sketch showing the general structure,

of a preferred prehardener as a mixing device for carrying out the invention;

Fig. 3 schematically shows a horizontal section of a mixing device"

in the form of such a fortress; Fig. 4 shows a vertical section along the line 4-4 in fig. 3 and indicates the flow pattern for the glass melt, and Fig'.. 5 shows a cross-section along line 5-5 in fig. 3 sets. in the upstream direction in the forehearth*

Although the following review will primarily be concerned with

with two common fibrable glass melt compositions, namely one for glass wool manufacture and the other for glass fiber textiles, it will be realized that many other glass compositions, whether fibrable or not, can be prepared in a similar manner. in the frame,

of the broad principles of the invention.

A normal glass melt for the production of glass wool insulation has, apart from residual materials, the following composition:

The primary volatile component in the just-mentioned glass-.; composition is sodium borate, which is formed by reaction between Na20 and B2°3*With ^ensYn-to the presence of sodium borate, the molten glass composition can be written as; . I. With regard to the invention, the components can be classified into two melting groups according to the following table:

° Sodium borate components Group I (non-volatile components)

Group II (volatile constituents)

The composition in group I can be identified as soda ash, which is almost reminiscent of melt compositions for rolled glass, which, in itself, are unsuitable for insulating rolls, although they are fibrable to a certain extent. This group is, however, less aggressive during manufacture.. than the total ■jlass composition for insulating roll, as it is indicated& above. The composition in group II is, however, very volatile and corrosive. I. according to the present invention prepares or is produced using the components i

group I a composite base melt in a continuous glass melting unit of a commonly occurring type within the glassmaking industry. The sodium bicarbonate components according to group II are then introduced into the molten base glass composition of the materials in group I, either as a melt or in the form of a solid raw material composition.

As the volatile components in group II only make up 11% by weight of the total glass composition, they can be melted down in a considerably smaller melting unit and at a significantly lower operating temperature. There will thus be significantly lower sodium borate loss by evaporation, which greatly facilitates the task of removing contaminants.

Since the sdclaKvar.tsglass in accordance with group I is approximately half-

as corrosive as the total glass wool composition is, it can be expected to extend approximately 100% of the life of the refractory material.

As a further example can. it mention© that a . common fibrable glass composition for fiberglass textile production is as follows:

The volatiles of interest in this composite glass melt are B 2 O 3 , F 2 and Na 2 O. In the same way as in the example for glass wool, two different melting groups can also be distinguished in this file trap: .- * Group II (volatile components) With such grouping, the particularly volatile bestsuid parts can be grouped. II, which represents 8% by weight of the total fiberizable glass melt, is prepared or prepared separately' in a small melter and added to the base glass melt to achieve similar advantages, as discussed in connection with. above-mentioned production of glass wool"' Further advantages can, however, be obtained by converting the molten base glass composition in accordance with group I with the aim of obtaining an autectic composition in the CaO / Al^ O^ SiO 2 system according to the following table:

With the remaining amounts of these components added to group: II, this gets the following composition:

By selective grouping of the components in the molten textile glass, an autectic base glass composition is thus achieved, which lowers the operating temperature of the main melter. This group formation also makes it possible to use less expensive raw material, e.g. colemanite, as a partial source for which the need for more expensive . barium acid decreases.

In fig. 1-5 shows preferred apparatus for introducing the molten additive composition to the base glass melt as well as for homogenizing it. the resulting mixture to obtain the final desired composite glass melt.

In fig. 1 shows a typical apparatus for the production of glass fibers 1 according to the invention. A continuous electric glass sweXter 10 is supplied with raw material for composition of the base glass melt through a transverse magazine 11. Molten base glass is withdrawn from ■ the melter 10 and made to flow through a pre-hardener 12.

Downstream of the smelter 10 and inside. in the forehearth 12 it is arranged

a mixing&one for molten glass and which includes spiral stirrers

15 and 16.. No, more detailed description of the mixing zone and

The operation of the stirrers will be given later in the inspection. The synthetic additive composition is prepared or manufactured in a separate

melting device 20 and is introduced into the mixing zone through an appropriate supply line 21, By means of combined mixing and

purape action of the pm stirrers 15 and 16, the molten additive* composition is mixed into and homogenized with the base melt to produce the final composition of molten glass. This final glass composition is then fed through a distributor 17 to the glass fiber forming locations 22 and 23.

Fig. 2 shows 1 projection of the mixing zone in the pre-heater with the stirrers

■ I. S and 16 omitted to show the structure and orientation more clearly

ay. the stirrers s bl andi ngg>l okers 13 and 14..Gener ell ts set currents

.the molten.glass from the upper left part to the lower right part i

fig. 2, as indicated by the arrow 30. The mixing blocks 13 and 14 are of identical design, the only difference between the two

blocks consist in their orientation in the forehard channel.. To avoid unnecessary mention, only the construction of the block 13 will be described, with regard to pi. that the block 14 is of the same design apart from its orientation and working function, which will be described in more detail below'.

The block 13 extends across the preharden channel with its upstream side 31 acting as a barrier or dam to the flow of molten base glass. with a

; slot 34, which together with the floor of the pre-heater channel forms a rectangular passage that extends in the longitudinal direction of the channel and opens onto the block's downstream side 35.

■ The mixing rig block 14, which has the same structure as the block 13, is located downstream of the block 13 and has its slot 34a facing upstream and arranged straight out of the slot 34 in the block 13. Between the mixing blocks 13 and 14 there extends gussets 361 and 36r with slanted sides 371 and 37r which slope downwards from the side walls of the forehearth to its floor, cg thereby together with the oaffitG: floor form a flow channel which forms a connection between the slot 34 in the block 13 and the slot 34a in the block 14»• In fig. 3 and 4, it is shown respectively. a horizontal and a vertical section' through the mixing blocks 13 and 14 with each agitator 43

and 44 off screw type located inside the blocks. The stirrers 43 ptj

44 comprises a screw band arranged around a rotatable. driven center shaft, as indicated by the arrows in fig. 3 and which is driven by means of a suitable drive device, e.g. an electric gear rotor (not shown). The mixing block 13 which is arranged in the upstream direction acts as a dam with regard to the flowing base ice glass melt and caused that the base glass can flow over the top of the block and into the area of influence of the stirrer 43. Immediately upstream of the stirrer 43, the molten additive composition is introduced into the liquid base glass melt through a conduit 21, the glass flowing over the upstream portion of the mixing block. preferably below the surface of the base glass melt flowing therein, as shown.

The agitator 43 mixes the molten base glass" and the additive melt while simultaneously pumping the mixture downwards through the mixing hopper 13, and then discharges the mixture downstream from the slot 34. the block 34, this slot serving as the inlet port to the block 14. As indicated<y>sd arrow 45 in Fig. 4, part of the smehfce emitted through the slot 34 will flow upwards and be sucked back into the mixing block 13 thereby again to be passed through the agitator 43.

The part of the molten mixture which is channeled to the slot 34a

is then further mixed as it pumps upwards through the block 14 under the influence of the agitator 44/. * The mixture which is emitted by flowing out over the top surface of the block 14 is the fully assembled glass melt. A part of the molten glass emitted at the top of the block 14, however, escapes upstream, while as will be seen from the arrow 46, a major part of this flow is returned to the inlet port 34a of the block 14, in order to be fed again through this flow block, while a smaller portion of the flow continues upstream as indicated by arrow 48, and is returned through mixing block 13. The remainder of the composite melt, marked by arrow 47, will flow downstream to distribution hearth 17. The reversing flow £tree,. as indicated by the arrows

45, 46 and 48, provides a natural flowing front or dam at the top of the mixing block 13, as indicated by line 50. Upstream of this flowing front 50 is new base glass.

Such a flowing front 50 means that the flow of unmixed base glass melt is directed through the mixing block 13, whereby a so-called "flow short circuit" is prevented from occurring. - Alternatively, a real dam can be provided at the top of the block 13 to thereby ensure that any flow of unmixed base glass melt takes place through the block 13.

When practicing the invention's improved method for producing

position of composite glass melts, a new degree of freedom is achieved with

.considering the composition of the glass melts. Not only special basic glass types can be combined to improve the overall economy in glass production, but also extremely volatile components, such as e.g. water.,, can now be included in the molten glass composition. '

Finally, it must be emphasized that even though the given examples constitute practical embodiments of the invention, the invention is

in no way limited to the design details shown, as numerous modifications can be made without exceeding the scope of the invention, as defined in the subsequent patent claims.

Claims (1)

1. Procedure for the production of glass melt, characterized in that: a) the glass composition to be included in the smelting is divided into a base part and an additive part, b) the base part is melted to produce a base melt,• c) the base melt is made to flow as a stream of molten glass, d) the additive part is added to the liquid stream of loose base glass in sufficient quantity to change the properties of the base glass to the desired extent, and e) the additive part is brought to a homogeneous mixture with the core of molten base glass. 2. Method as stated in claim 1, characterized by . that the base glass composition consists of autectic glass composition. ' 3. Procedure as set forth in claim 1, characterized " in that the raw materials for base-. the glass part is mainly free of volatile components, while the raw materials for the glass part are made up of a composition that includes volatile components. 4. Method as stated in claim-3, characterized in that the composition containing volatile components is in the melt phase.. 5. Method as stated in claims 1 - 4-, for the production of molten fibrable glass, characterized in that: a) the raw materials for the base part are given the following composition: b) the base glass melt is caused to flow from a melter into a preharden channel, c) the additive part is added to the base glass melt as it flows through the prehardener, and given the following composition: d) the additive part is mixed homogeneously in the base glass melt. 6.' Method as stated in claims 1 - 4, for the production of fibrable glass melt, characterized by: ta) the raw materials for the base glass melt are given <:> the following composition b) the molten base glass is caused to flow from a slattern into a prehardening channel, c) the additive part is added to the base glass melt while it flows through the pre-hardener, and is given the following composition: 7. Procedure as specified in claim 6, •can be effective in that the additive is in the melt phase.. 8. Method as specified in claim 5, characterized in that the base glass melt has the following composition: while the additive part has the following composition: 9o Procedure for the production of glass melt with prior, specific Composition, characterized by that? a) a melt composed of part of the desired glass composition is produced^ b) the molten part of the total composition is brought to ..flow in an area for receiving an additive part. of the desired glass composition, c) said additive part for the desired glass composition is introduced into the molten part of the composition, d) the additive portion of the tempered glass composition is mixed carefully with the melted part of the composition to form a melted tea mixture of a different composition and with different properties.. 10, Method as stated in claim 9, characterized in that steps c and d are repeated until the "desired glass composition is achieved. 11. Procedure for the production of glass melt with the desired composition, k a.' r -acts in ser.t in that: a) a raw material sheet is produced which contains a relatively small volatile component of the desired glass composition, b) the mixture of raw materials is heated until a molten mass is formed, c) the remaining, more volatile component, of the desired glass composition is processed separately and then introduced into said melt mass,' . d) the volatile component is carefully planted with the melt to melt a glass composition of a different character than the less volatile component. 12. Process for the production of glass melt of the desired composition as stated, in claim 11, characterized in that the treatment of the volatile component comprises heating said part before it is mixed with the molten mass. 13o The method as stated in claim 12, characterized in that the volatile component heated to a molten state. 14. Process for the production of glass melt with components that have different melting temperatures, characterized in that: a) a raw material mixture is produced which contains the components with a relatively high melting point, b) the high melting raw material mixture is heated to form. of a molten mass, and c} the remaining, more; volatile components are processed separately and mixed in the molten mass to form glass melt of the desired composition sentence"'' . - 15. Method for the production of glass melt with a blown composition, character-1 in that a raw material part is produced which contains the components of the composition with a relatively high melting temperature, after which this high-temperature part is heated to a molten state, while the low-temperature components of the composition are mixed the smelter thereby producing a molten mass of the desired composition, and. which differ significantly from the combined shares. f. 16. Method for mixing additive components into a stream of molten glass flowing through a pre-heater, characterized by: a) the flow of molten glass is delimited in the pre-heater and directed into a mechanical mixing areaj. b) the additive components are added to the molten glass stream, c) the additive components and the molten glass are mixed and stirred in the mechanical mixing area by means of pushing stirring forces, d) the produced mixture is caused to flow into a reservoir formed by the pre-hardening boundary and a portion of the pre-hardening conduit extending downstream of the restriction to terminate in another pre-hardening boundary, below which the reservoir network communicates with the mechanical mixing area, e) part of the produced mixture is returned from the magazine to the mechanical mixing area to be passed through this again and mixed with freshly received material, f) a further part of the produced mixture is caused to flow from the magazine into another mechanical mixing area, g) the mixture is further mixed and stirred in this other mixing area by means of pushing stirring forces and h) the molten mixture is caused to flow from the second . mixing area, during which a portion of the mixture is returned to the container and the remaining portion is caused to flow down the stream for the second prehardener boundary as a homogenized, molten glass mixture. 17...Apparatus for iblancling additive components in a stream of molten glass, characterized by ai: glass melter; a forecourt channel extending from the smelter; two-t.andem blocks extending like dams across.'the channel's width and with a lower height than the working level for smelting! glass in the channel, the idea being that each such block is equipped with a cylindrical passage from the block's top surface to the channel floor and in connection with a passage in the channel's longitudinal direction cg which extends sog from the cylindrical passage to an opening in a block surface across the channel; a stirring device of screw type and placed inside the cylindrical passage in each block, the tandem blocks being oriented such that the longitudinal passage of the upstream block opens towards the transverse surface of the downstream block, and the longitudinal passage of the downstream block opens towards the transverse surface of the upstream block, so that the longitudinal passenger openings face each other; while the respective spiral converters are operated in such a way that the upstream the stirrer pumps molten glass which flows over the block's upper surface downwards through the block for 5 is emitted in the hot flow direction from the block, and the downstream stirrer mixes and pumps molten glass upwards - through its assigned block to be inherited from the block's upper face' . 18. Apparatus as specified in claim 17, vessel acts in, for example, by a line device for introducing additive component upstream of the spiral stirrer which pumps down.