Note: Descriptions are shown in the official language in which they were submitted.
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GLASS MELTING APPARATUS AND METHOD
BACKGROUND OF THE INVENTION
This invention relates to certain improvements in
apparatus and methods for melting glass. More
particularly, this invention relates to apparatus and
methods which control the location of the "hot spot," i.e.
area of highest temperature in the liquid pool of melting
or molten glass in a glass melter so as to control the wear
out of various melter and discharge elements thereby
reducing the number of shutdowns needed for replacement or
rebuild purposes. Still further, this invention relates to
unique methods and apparatus for venting corrosive
volatiles from the system.
Melters of various shapes and sizes which present
glass batch (usually in powdered ingredient form, with or
without cullet) often by floating the batch material as a
relatively thick layer on top of a molten pool of glass
being heated and melted beneath the batch, and thereafter
distributing the molten glass from the pool through a
discharge port in a side wall of the melter to a
conditioning zone (conditioner), and thereafter to a
forehearth array or other working area, are well known in
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the art. Exemplary of such systems are conventional, in
line combinations of a melter, conditioner, and forehearth
used to distribute molten glass to an array of spinners for
making fiberglass batts of insulation. Other uses for such
combinations are, of course, known, and the art, as a
whole, is generally represented by the following prior art
references:
U.S. Patent No. 3,498,779 4,365,987
3,897,234 4,812,372
4,001,001 4,994,099
4,017,294 5,194,081
4,023,950 5,616,994
Generally speaking,
the art of glass making accepted the
problem of multiple shutdowns due to the fact that the
various elements in conventional melters, except in very
unusual and unpredictable situations, wore out at different
times. In this respect, it is characteristic in the prior
art construction of melters to employ a cylindrical or
rectangular tank-like configuration in which the side and
bottom walls are formed of refractory material such as Cr,
Al-Zr-Si, or Al/Cr based compositions whose corrosion rate
usually increases with increased temperatures. Adding to
this problem is the fact that in such configurations one or
more discharge ports are either required or desired at
different locations within the tank, e.g. in the bottom
wall and in at least one location in the side wall of the
tank. Because the temperature of the glass can, and often
does, differ markedly between a "hot spot" volume in the
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molten glass, usually in the center of the tank near the
bottom wall, and the remaining molten glass volume, e.g. at
the side walls, melter parts in the cooler areas wear out
less rapidly than parts located in or proximal the "hot
spot."
In a typical example of this problem, the melting tank
is provided in its bottom wall with a discharge port for
draining the tank and a side discharge port for
distributing the molten glass to a conditioning zone. Such
discharge ports, whether in the bottom or side walls, are
normally formed of molybdenum or an alloy thereof which is
relatively corrosion resistant and thus is reasonably able
to withstand the high temperatures experienced in the
melter over a given period of time. Unfortunately, like
the refractory wall material, these molybdenum based ports
have a corrosion rate which increases with temperature.
In many melters it has also been conventional to cool
the walls by various techniques such as with a water-cooled
shell surrounding the melter. Such cooling of the bottom
and side walls, despite inherent currents of flow in the
molten glass, tend to isolate the "hot spot" and set up the
temperature differentials as discussed above, which then
lead to the differences in wear out rates of the various
parts and the need for expensive, time consuming, multiple
shutdowns otherwise unnecessary if all the parts were to
wear out at substantially the same time.
In a typical prior art melter, for example, usually of
a circular, cylindrical bottom, side wall configuration,
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the furnace is open topped, side and bottom wall cooled,
and is provided with electrodes to melt the batch material.
These electrodes are usually located in the melter either
above the batch or in the molten pool of glass itself,
often near the bottom or inserted through the batch.
Powdered batch material is then "floated" on top of the
melting glass beneath it, usually by a conventional,
metered batch delivery system located above the melt area
and fed by gravity continuously to the batch layer as its
underneath surface melts into the molten volume of glass
beneath it. It is, of course, within this molten glass
volume beneath the batch layer that the aforesaid "hot
spot" forms.
While convection currents created in the melting glass
serve to equalize, somewhat, the temperature of the molten
glass pool, it is very often an inherent characteristic of
such melters, particularly where bottom entry electrodes
are employed, that the bottom center of the melter is where
the "hot spot" forms. For example, a typical "hot spot"
may be from about 3150 -3250 F. By contrast, the side
walls will only then be, particularly if water-cooled, at
a significantly lower temperature, e.g. about 2500 -2700 F.
Even if water-cooled, in certain instances, the bottom wall
will be so close to the "hot spot" that its temperature in
a localized area will, for all intents and purposes, be
that of the "hot spot," thus differing from other areas of
the bottom wall, as well as the side wall and discharge
port in the side wall. Since the drainage port is
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conventionally located in the center of the bottom wall,
and thus at or proximal the usual "hot spot" location, its
corrosion rate differs markedly from that of the side
discharge port and side walls.
As exemplified by the above typical melter
arrangement, multiple melter shutdowns may thus become
necessary. For example, the discharge drain port and/or
bottom wall may have to be replaced, while the side walls
and side discharge port remain in acceptable operating
condition, only to have to replace one or more of these two
latter parts at a later time in a second shutdown, while
the replaced bottom wall and/or drain discharge port are
not yet worn sufficiently to economically justify their
replacement.
In short, it would constitute a considerable advance
in the art of glass melting if a technique were developed
which could control the location of the aforesaid "hot
spot" in a glass melter so as to displace it (locate it)
away from the refractory walls and metallic discharge port
tubes (side and bottom) such that all of the elements in
the melter subject to corrosion and wear out therefrom were
to wear out at substantially the same time.
The term "at substantially the same time," as used
herein, means that the elements which are the subject of
corrosive wear out are in such a condition at the time that
one element is in the most advanced condition of wear out,
that it is economically justifiable to replace all the
elements, rather than to go through another shutdown to
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replace a less worn out element when it completely wears
out later in time.
Signi f icant
advance toward reaching this goal and solving this prior
art problem was achieved, based upon the acceptance of the
inherent location of the "hot spot" in the melter. By the
use of a unique discharge port concept located in the side
wall of the melter, a sufficient distance away from the
"hot spot," coupled optionally with side and bottom wall
cooling means, the side discharge ports and side walls
could justifiably be replaced at the same time. In
addition, in certain embodiments, by relying on convection
currents and sufficient bottom wall cooling, the bottom
wall and bottom discharge drain theoretically could, at
times, be controlled to wear out at substantially the same
time as the side wall and side discharge port. Despite
this significant advance in the art, it has now been found
that the "hot spot" (i.e. volume of highest temperature)
often exists, in certain furnaces, inherently too close to
the bottom and/or side walls of the melter tank and that
circulation currents, even with wall cooling, are
insufficient to keep the wear out rate of the bottom wall
and bottom discharge orifice truly substantially equal to
that of the side walls and side discharge orifice. Thus
there continues to be a need in the art for a still further
improvement which creates an even more equalized wear out
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rate among the essential parts in the melter (e.g. the
refractory melter lining which makes up the melter walls,
side and bottom, and the various discharge ports in these
walls.
There is yet another problem which the art of glass
melting has had to face. In many glass melting operations,
such as in melting glass ultimately used to make fiberglass
insulation, it is necessary to employ batch ingredients
which create highly corrosive volatiles during the melting
and/or conditioning operation. These volatiles often end
up in the atmosphere above the glass and can thus rapidly
corrode walls, orifices and heater elements if not
effectively exhausted from the system. Such volatiles are
well known and include, for example, various sodium and
borate compounds.
In melting systems which do not employ, or need not
employ, the highly advantageous technique during glass
melting of floating batch material in a relatively thick
layer (e.g. about 3"-4", or at times as high as 10") on top
of the molten glass, the corrosive volatiles can usually be
exhausted during melting by exhausting them from the melter
itself. However, when the more desirable batch technique
of floating the batch on top of a molten pool of glass is
employed, the volatiles do not readily escape through the
batch, but rather are only released in the conditioner when
the molten glass is then freed from the batch material
being on top of it. This, then, gives rise to the need for
a new technique for effectively eliminating corrosive
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volatiles from the glass in the conditioner, particularly
before they reach the forehearth.
It is a purpose of this invention to fulfill the above
needs in the art, as well as other needs which will become
apparent to the skilled artisan once given the following
disclosure.
SUMMARY OF THE INVENTION
Generally speaking, this invention fulfills at least
one of the above-described needs in the art by providing
both a method and an apparatus for melting glass which
controls the location of the "hot spot" so as to locate it
within the melt at a sufficient distance from the side and
bottom walls, as well as any discharge orifice therein, so
LhaL Lhe discharge orifices and walls (bottom and side) may
be replaced at substantially the same time.
In one embodiment of this invention this is
accomplished by providing in a melter for melting glass
from batch material therein in which the batch material is
floated on top of a pool of molten glass and the batch is
melted by heating means so located as to form a finite
volume of molten glass within the pool of molten glass,
which finite volume is at a temperature substantially
higher than the remainder of the molten glass within said
pool, the melter including a side wall and a bottom wall
and a discharge port located within at least one of the
walls, the improvement comprising wherein:
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the heating means are so located as to create
this finite volume of substantially higher temperature at
a spaced distance from the walls and any side discharge
orifice located in the walls whereby the walls and any side
discharge orifice wear out at substantially the same time
during melting of glass in the melter.
In certain preferred embodiments of this invention the
heating means comprises a plurality of electrodes in a
generally circular array located within the molten pool
beneath the batch material floating thereon, and including
a retaining structure for each electrode extending above
the batch, which retaining structure includes an adjustment
mechanism for adjusting the depth to which the electrode is
inserted into the molten pool, and also, preferably, for
adjusting the horizontal location of each electrode within
the pool, as well. By adjustment of the electrode array
both horizontally and vertically within the pool, the
optimal location for the inevitable "hot spot" can be
achieved for any particular size and/or configuration of
melter tank (furnace) extant to optimize the goal of
achieving substantially the same wear out time of the
various melter parts.
In certain preferred embodiments, in this respect, the
melter may be one of an open top type, with a water-cooled
jacket or shell, whose batch feed, optionally, may be a
simple tube located above and in the center of the
electrode array. In still further preferred embodiments,
the melter is a cylindrical tank with a side discharge port.
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A
particularly advantageous electrode array, in this respect,
consists essentially of six electrodes equally spaced in a
circular pattern about the center of the cylindrical tank,
the radius of the circle being about one-third the radius
of the inside diameter of the tank.
This invention further includes within its scope
certain unique methods for melting glass. Generally
speaking, in this respect, this invention includes in the
method of inelting glass in a melter which includes a bottom
wall, a side wall and at least one discharge port located
in a said wall and comprised of a corrosion resistant
material whose corrosion rate increases with temperature,
the steps comprising, forming a molten pool of glass within
the melter, floating batch material on top of the molten
pool, melting the batch material so as to add further
molten glass to the pool, discharging molten glass from the
melter through a discharge port, and during the melting of
the glass batch material, creating within the pool a finite
volume of molten glass which is at a significantly higher
temperature than the remainder of the molten glass within
the pool, the improvement which comprises forming the
finite volume of the higher temperature molten glass at a
location sufficiently removed from the walls and the
discharge port such that the walls and discharge port wear
out at substantially the same time.
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This invention further includes within its scope
certain unique apparatus and methods for exhausting
corrosion causing volatiles from the overall system before
they reach the forehearth, thus fulfilling yet other needs
in the art.
Generally speaking, the unique apparatus as
contemplated herein for exhausting volatiles during glass
melting and distribution includes, in the combination of a
walled melter, a walled conditioning system having at least
one heating element extending through an orifice in a wall
thereof and a forehearth, said melter being connected in
molten glass flow communication with said conditioning
system through a discharge port located in a wall of the
melter at a first end of the conditioning system and the
opposite end of the conditioning system being connected in
molten glass flow communication with the'forehearth, the
improvement comprising at least one removable heating
element extending through the orifice in a wall of the
conditioning system and exhaust means proximal the orifice
for exhausting corrosive volatiles from above the molten
glass in the conditioning system through the orifice when
the removable heating element is removed therefrom.
In certain preferred embodiments of this invention the
melter, conditioning system and forehearth are all located
in substantially the same horizontal plane. In certain
other preferred embodiments, of course, this invention
employs as its melter the aforesaid unique melter which
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controls Lhe "hot spot" so Lhat its various elements wear
out at substantially the same time.
Still further, and generally speaking, the unique
methods associated with this novel exhaust technique
include in the method of melting, conditioning and
distributing molten glass wherein the method includes the
steps of providing in serial flow communication, a melter,
a walled conditioner and a forehearth array, melting glass
in the melter, delivering molten glass from the melter to
Lhe condiLioner, providing aL least one heaLing means
located in an orifice in a wall of the conditioner,
delivering the molten glass from the conditioner to the
forehearth and distributing the molten glass from the
forehearth, wherein the method further includes the step of
removing a substantial portion of the corrosive volatiles
from the atmosphere above the glass before they reach the
forehearth, the improvement comprising, removing at least
one of the heating means from its respective orifice
thereby providing an open orifice in a wall of thc
conditioner, providing an exhaust means in exhaust
functioning communication with respect to the open orifice,
and exhausting corrosive volatiles from the conditioner
through the open orifice.
In certain preferred embodiments the method as above
set forth further includes the step of providing batch
material on top of the molten glass in the melter.
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This invention will now be described with respect to
certain embodiments thereof accompanied by various
illustrations wherein:
IN THE DRAWINGS
Figure 1 is a partial side sectional view of one
embodiment of this invention.
Figure lA is a partial top view of the embodiment of
Figure 1, with the molten glass and batch only partially
shown so as to illustrate the inside bottom wall of the
melter.
Figure 2 is a partial side sectional view of the
embodiment of Figure 1.
Figure 3 is a schematic outline of the current pattern
among the electrodes in the embodiment of Figure 1.
Figure 4 is a partial side sectional view of the side
discharge port and vent chamber of the embodiment of Figure
l.
Figure 5 is an end sectional view of the cooling means
and side discharge tube of Figure 1.
Figure 6 is a side sectional view of a conditioner
cooling means used in the practice of an embodiment of this
invention.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
With reference initially to Figure 1, there is
illustrated therein an apparatus for melting glass
according to this invention. The apparatus as illustrated
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includes a melter 1, a conditioner 3, and, as partially
shown, a forehearth 5. Forehearth 5 is conventional and,
for example, may be of the type provided with multiple
orifices along its elongated bottom wall (not shown for
convenience) for distributing molten, conditioned glass at
an appropriate temperature to a conventional spinner array
for making fiberglass insulation batts (also not shown for
convenience). Orifice 7, as illustrated, is an air-cooled
drain orifice in this embodiment used to drain the system
during shutdown, the distribution orifices leading to
fiberglass spinners being further downstream.
In the embodiment of Figure 1 the three zones of
operation, i.e. melter 1, conditioner 3, and forehearth 5
are preferably all located in substantially the same
horizontal plane. This eliminates a known use of the
location of the forehearth on a level (e.g. on a separate
floor of the plant) below the conditioner, called the "drop
area", which heretofore was advantageously used to exhaust
volatiles from the system. In this way, the need to build
into the plant facility a separate level or floor is
eliminated and its considerable cost saved. However, this
eliminates the aforesaid advantageous drop area between the
exit end of conditioner 3 and entrance end 6 of forehearth
5 which was used to vent (exhaust) corrosive volatiles.
This, in turn, gives rise to the unique venting system of
this invention discussed above and described more fully
below.
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Turning now to a more detailed description of melter
1, attention is directed, in addition to Fig. 1, to Figs.
1A, 2 and 3. The mechanism illustrated is one embodiment
of a mechanism as contemplated by this invention for
selecting the location of, and controlling the size of,
"hot spot" 9 created in molten glass pool 11 during the
melting operation. As illustrated schematically in Figs.
1, 1A, and 3 in dotted lines, by using an array of heating
electrodes 13, and here preferably six, arranged in a
substantially circular fashion below the layer of batch
material 15 floating on pool 11, "hot spot" 9 is generally
confined to a finite, generally hexagonal or circular
cylindrically shaped volume of glass below batch 15, whose
central vertical axis "C" corresponds with the central
vertical axis of cylindrical melter tank 1. Figure 3 is a
schematic whose full lines illustrate the theoretical paths
of heating current extending among the electrodes and whose
dotted lines illustrate a top view of "hot spot" 9.
Melter 1 is of a conventional tank-like, cylindrical
construction having conventional side wall 19, and bottom
wall 23, each lined with refractory linings 21 and 25,
respectively. Such refractory linings 21 and 25 may be
formed of conventionally used refractory material such as
a chromium based material which is known for iLs corrosion
resistance, but whose corrosion rate increases with
temperature. In a typical example, lining 21 may be 90% or
more by weight Cr, while linings 19, 23, and 25 may have
less Cr, e.g. about 30-5011 by weight. Melter 1 further
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includes in conventional fashion drain discharge port 31
located centrally of melter 1. Discharge port 31 is
conventionally formed of a corrosion resistant metallic
tube 33 inserted through an orifice in shell 29, bed
material 35, wall 23 and liner 25. Port 31 is principally
used for draining glass from melter 1 preparatory to
shutdown.
As further illustrated in Fig. 1, but better shown in
Fig. 2, batch material 15 is floated on pool 11 of molten
glass such that the underside surface of batch material 15
is constantly being melted while the batch layer is being
added to as it is consumed by a conventional metered batch
system whose exit end tube is shown at 37. As best
illustrated in Figs. 1, 1A, powdered batch 15 is fed by
gravity to the substantial center of the circle having a
radius R, whose circumference is subscribed by the location
of the six electrodes 13 as points on the circle and whose
center is contiguous vertical axis "C".
As best illustrated in Fig. 2, the depth "D" of molten
pool 11 is the distance from the inner surface of lining 25
to the under surface of batch material layer 15. Distance
"D" varies, of course, given the drainage slope in the
bottom wall structure of melter tank 1. As shown in Fig.
1A, in one embodiment of such a melter 1, radius R, may be
about 7-8 feet, radius R1, about 1/, -'/a of R2 , e.g. about 2-3
feet, while depth "D" at the side wall 19 may be about 13-
15 inches and the thickness "T" of the powdered to semi-
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molten batch layer may be about 3-5 inches or more (e.g.
up to 1011).
With further reference to Fig. 1 and Fig. 4 more
particularly, melter 1 is provided with a side discharge
port generally at 39 for distributing molten glass from
pool 11 to conditioner 3. In preferred embodiments of this
invention side discharge port 39 is constructed
as
illustrated here, discharge port 39 includes a corrosion
resistant metallic tube 41 (e.g. of molybdenum or an alloy
thereof and usually of the same metal which makes up drain
tube 33) extending through the side wall structure of tank
1 in flow communication with the entrance end of
conditioner 3. As shown in Figs. 1 and 5, tube 91 is
thicker at its top than bottom circumference, and is cooled
by circulating water or other fluid through surrounding
shell 43 in the direction of the arrows (Fig. 5).
The purpose of making the top of tube 41 thicker is
because, for some reason not fully understood, and despite
the fact that tube 41 is fully submerged in molten glass
theoretically protecting it throughout its circumference
from oxidation, the top of tube 41 wears out more rapidly
than its bottom portion. Thus it has been found in
practice to be advantageous for longer wear life to, for
exainple, with a discharge tube of about 6 inches (O.D.),
use a 4 inch (ID) orifice created by a% inch offset from
center. While not fully understood, this uneven wear
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pattern may be explainable by the phenomenon known as
"upward drilling" in a refractory material as it is
corroded by corrosive materials in the glass.
Conditioner 3 is principally used to lower the glass
exiting melter 1 to an appropriate temperature for
distribution to the forehearth. For example, in a typical
operation, glass "G" may exit side discharge tube 41 at a
temperature of about 2560 r, and be lowered to about 2230
(e.g. a drop of greater than 200 F) as it enters forehearth
5 beneath submerged block (dam) 45 which functions along
with dam 47 to isolate molten glass in conditioner 3 from
glass in forehearth 5 during shutdown. Dam 45 further
serves to isolate the relatively volatile free atmosphere
of forehearth 5 from the atmosphere of conditioner 3. In
a similar manner, of course, dam 49 isolates molten glass
in conditioner 3 from melter 1 and exhaust area "E"
(described below) during a shutdown. Drain port 51 is
provided in bottom wall 53 (which may be water-cooled) to
drain glass from conditioner 3 prior to shutdown or when
otherwise needed.
Provided in top wall 55 of conditioner 3 is a cooling
baffle structure 57 (more than one can be optionally added,
if desired) for circulating cooling water or air
therethrough. Baffle 57 is a unique concept to this
invention. Without baffle(s) 57, there would be formed a
stream of higher temperature glass on the surface of flow,
potentially causing lower glass to crystallize. Baffle(s)
57 divert hot glass downwardly, thereby preventing this
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problem from occurring and creating better homogeniety of
temperature in the glass and a lack of stagnant glass in
the bottom of conditioner 3.
In addition, top wall 55 is provided with removable
burners 59a-e located in their respective orifices
extending through wall 55. During start-up of the system,
in conventional fashion, burners 59a-e are employed to heat
the refractory walls so that molten glass flowing from
melter 1 and exiting tube 41 will remain molten, and
continue to flow through conditioner 3, rather than
solidify when it contacts the refractory walls.
After start-up and filling conditioner 3 to the depth
desired with molten glass (not shown for convenience), the
molten glass must then be cooled to the required exit
temperature as aforesaid. For this purpose, one or more of
the removable burners 59a-e are removed (thus vacating
their respective orifice 60a, b, c, d, or e) and replaced
by water-cooled tubes such as a cooling tube 61 shown in
Fig. 6, which is inserted into a vacated orifice made open
by removal of a burner 59 therefrom. As shown in Fig. 6,
cooling tube 61 is a simple rectangular or circular shell
63 (depending on the conforming shape of the vacated
orifice it is inserted in). Shell 63 has located in its
wall, water outlet port 65. Within shell 63 there is
located an internal tube 67 for providing cooling water (or
other fluid) to shell 63 in the direction of the arrows.
Cooling tubes 61 are metallic and may be made of a
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corrosion resistant metal such as molybdenum, if desired.
Tubes 61 can be provided with a simple mechanism for
controlling their depth of emersion into the molten glass.
This, in turn, can be used to ultimately control the outlet
temperature of the glass at the entrance 6 of forehearth S.
In this respect, orifice 64 is used for a thermocouple (not
shown) to sense the temperature of the glass that is
entering forehearth 5.
To cool the glass, cooling air may be used instead of,
or alternatively with, cooling tubes 61. For example, in
a typical operation which cools the molten glass from about
2560 F to 2230 F in conditioner 3, orifice 59a may have
cooling air blown through it, as may orifice 59e. This
also forces an atmosphere changeover to continuously rid
the atmosphere of volatiles. Then, cooling tubes 61 may be
inserted into orifices 59b and c. This leaves orifice 59d
open for use in a unique exhaust system as contemplated by
this invention and as described below. It is understood,
of course, that orifices 59a-e may have other combinations
of air flow and/or cooling tubes employed, including all
cooling tubes 61 or all cooling air flow if desired. It
is, however, an important feature of a preferred embodiment
of this invention that at least one of these vacated
orifices, preferably either orifice 59d or 59e, and most
preferably 59d, be employed to exhaust corrosive volatiles
from the atmosphere above the molten glass in conditioner
3.
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As illustrated in Fig. 1 in phantom dotted lines, an
exhaust system 69 is provided at orifice 59d which may be
turned on after burner 59d is removed, thus exhausting
volatiles from conditioner 3 before they reach forehearth
5. As a further part of a preferred exhaust system, a
further permanent exhaust port 71 is provided at the
initial entrance end of area "E" in conditioner 3 where an
initial portion of the volatiles may first be removed from
the atmosphere above the molten glass immediately as it
exits side discharge tube 41.
Turning now, more particularly, to the electrode
melting apparatus illustrated in Figs. 1-3, there is
presented a unique apparatus and method for controlling the
size and location of "hot spot" 9 which can otherwise be so
detrimental to wear out, and which, if not controlled, can
cause unnecessary multiple shutdowns of the system as
described above.
In the melting configuration as illustrated there are
provided six conventional electrode melters 13 which are
conventionally water-cooled by entrance line 73 and exit
line 75. Other configurations using lesser numbers of, or
more, electrodes may be used. Electrode 13, including its
current-carrying shaft 79, may be formed of molybdenum as
is the actual electrode melter portion 81. Water-cooled
shell 77 may be formed of stainless steel. As illustrated
schematically in Fig. 2 and more realistically in Fig. 1,
electrode portion 81 is immersed in the molten glass 11 to
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the depth required, while molybdenum shaft 79 is
protectively cooled by cooling shell 77.
Electrode 13 is supported by horizontal shaft 83 which
carries electric current and the cooling water to and from
the electrode. In turn, shaft 83 is connected to an
adjusting mechanism 85 which includes a central shaft 87
which retains, in vertical position, outer shaft 89.
Rotating mechanism 91 allows shafts 89, and thus shaft 83
attached thereto, to be angularly adjusted in the
horizontal plane by rotating the shaft on ball bearing 93
and securing the shaft at the desired angle by a
conventional locking mechanism 95 when the desired angle is
reached.
In addition to this horizontal adjustment, the
vertical position of electrode 13 within molten pool 11 is
accomplished by gear rachet mechanism 97 which, via screw
threaded rod 99 attached to shaft (sleeve) 89, slidable in
retaining tube 101, may be activated to vertically adjust
the height of shaft 83 above melter 1 and thus that of
electrode 13 with respect to pool 11. Protective bellows
103 extends between slidable shaft 89 and upper nonslidable
shaft 105 to which rachet mechanism 97 is attached, to
protect that portion of shaft 87 on which shaft 89 slides
during vertical adjustment, from dust and other
contamination.
As can be seen, the adjusting mechanism 85 provides an
effective mechanism for adjusting both the horizontal and
vertical positions of each electrode 13 with respect to the
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molten bath. Since it is the electrode array which
ultimately defines and limits the finite volume of "hot
spot" 9 (e.g. typically at 3150 F-3250 F), the unique
apparatus illustrated here presents, by its precise
adjustability, the ability to control the location, size
and, indeed, in certain instances, the general shape of the
"hot spot" 9. Thus, by proper adjustment, the "hot spot"
may be controlled at a preselected location within melter
1 (i.e. within pool 11) sufficiently removed from the
sensitive refractory and metallic parts, so that these
elements wear out at substantially the same time, thus
minimizing the number of shutdowns needed for repair.
In a typical operation of the above-described system,
electrodes 13 are adjusted so as to be equally spaced (as
illustrated in Fig. 1A) about vertical axis "C" of tank 1.
Electrode melter portion 81 of each electrode 13 may be
approximately 6 inches in diameter and about 6;4 inches in
height and may be operated at about 4000 amps. Given a
side height "D" within the aforesaid range, and a radius R,
of about 8 feet and a radius R1 of about 3 feet, with an
adjusted depth of abouL 9-12 inches between Lhe boLtom of
electrodes 13 and the top surface of bottom wall liner 25
for each of the six electrodes employed in the array as
shown, a "hot spot" 9 as illustrated in Figs. 1, 1A is
sufficiently controlled and confined to a finite volume
within the electrode array such that the "hot spot",
usually at about 3150 F-3250 F is substantially removed
from the refractory walls and discharge ports, while such
23
CA 02283020 1999-09-22
walls and ports are located nearest the coolest glass as
cooled by the cooling water in cooling shell 29 and as
affected by glass flow currents shown by the circulating
arrows in Fig. 1. In this way, and by proper adjustment of
the electrode array for any given configuration of melting
tank, arrived at by routine experimentation well within the
skill of the artisan once given this disclosure, a unique
technique for substantially equalizing wear out of the
melting tank parts may be accomplished, thus minimizing the
nuinber of shutdowns required for replacement of parts.
Once given the above disclosure, many other features,
modifications and improvements will become apparent to the
skilled artisan. Such features, modifications and
improvements are, therefore, considered a part of this
invention, the scope of which is to be determined by the
following claims:
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