U.S. patent application number 13/901800 was filed with the patent office on 2013-10-03 for monolithic float glass forming chamber and method of construction.
This patent application is currently assigned to VIDRIO PLANO DE MEXICO, S.A. DE C.V.. The applicant listed for this patent is Rafael AVALOS-GUZM N, Hugo Jaime HERRERA-CAMPOS, Felipe PACHECO-SALINAS, Alberto SOL S-OBA, Humberto VALDES-CARRILLO. Invention is credited to Rafael AVALOS-GUZM N, Hugo Jaime HERRERA-CAMPOS, Felipe PACHECO-SALINAS, Alberto SOL S-OBA, Humberto VALDES-CARRILLO.
Application Number | 20130255320 13/901800 |
Document ID | / |
Family ID | 43496107 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130255320 |
Kind Code |
A1 |
AVALOS-GUZM N; Rafael ; et
al. |
October 3, 2013 |
MONOLITHIC FLOAT GLASS FORMING CHAMBER AND METHOD OF
CONSTRUCTION
Abstract
The present invention is related to a monolithic float glass
forming chamber and its method of construction. The forming chamber
being of the type that includes a bottom wall; side walls and a
roof wall to form an elongated chamber, the elongated chamber
including a forming section and a cooling section for a desired
thickness and ribbon width of molten glass, wherein each type of
wall comprises: a first refractory structure with a mixture of a
castable and pumpable refractory material and an insulation
material; and a second refractory structure with a castable and
pumpable refractory material, the first and second refractory
structures being formed at the same construction site.
Inventors: |
AVALOS-GUZM N; Rafael;
(Nuevo Leon, MX) ; VALDES-CARRILLO; Humberto;
(Coahuila, MX) ; PACHECO-SALINAS; Felipe; (Nuevo
Leon, MX) ; SOL S-OBA; Alberto; (Nuevo Leon, MX)
; HERRERA-CAMPOS; Hugo Jaime; (Nuevo Leon, MX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AVALOS-GUZM N; Rafael
VALDES-CARRILLO; Humberto
PACHECO-SALINAS; Felipe
SOL S-OBA; Alberto
HERRERA-CAMPOS; Hugo Jaime |
Nuevo Leon
Coahuila
Nuevo Leon
Nuevo Leon
Nuevo Leon |
|
MX
MX
MX
MX
MX |
|
|
Assignee: |
VIDRIO PLANO DE MEXICO, S.A. DE
C.V.
Nuevo Leon
MX
|
Family ID: |
43496107 |
Appl. No.: |
13/901800 |
Filed: |
May 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12462039 |
Jul 27, 2009 |
8464555 |
|
|
13901800 |
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Current U.S.
Class: |
65/182.5 |
Current CPC
Class: |
C04B 2235/3201 20130101;
C04B 2235/3418 20130101; C04B 2235/3208 20130101; C04B 2235/3272
20130101; C04B 35/043 20130101; C04B 35/66 20130101; C04B 2235/9692
20130101; C04B 2235/3232 20130101; C04B 35/18 20130101; C04B
2235/3217 20130101; C04B 2235/96 20130101; C03B 18/16 20130101 |
Class at
Publication: |
65/182.5 |
International
Class: |
C03B 18/16 20060101
C03B018/16 |
Claims
1-16. (canceled)
17. A monolithic float glass forming chamber, said forming chamber
being of the type that includes a bottom wall; side walls and a
roof wall to form an elongated chamber, said elongated chamber
including a forming section and a cooling section for a desired
thickness and ribbon width of molten glass, wherein each type of
wall comprises: a first refractory structure with a mixture of a
castable and pumpable refractory material and an insulation
material; and a second refractory structure with a castable and
pumpable refractory material, said first and second refractory
structures are formed on the construction site.
18. The monolithic float glass forming chamber as claimed in claim
17, wherein the first and second refractory structures are carried
out by the sol-gel process.
19. The monolithic float glass forming chamber as claimed in claim
17, wherein the mixture of the pumpable and castable material and
the insulation material comprises from about 40 to from about 90%
of Al.sub.20.sub.3 and an additive as carlita, thermolita, perlita,
verelite or a mixture of the same.
20. The monolithic float glass forming chamber as claimed in claim
17, wherein the castable and pumpable refractory material
comprising from about 40 to about 65% by weight of Al.sub.20.sub.3;
from about 55 to about 30% by weight of Si0.sub.2; 3.5% by weight
of a mixture of Ti0.sub.2 and Fe.sub.20.sub.3 and CaO; and 0.5% by
weight of Na.sub.20.
21. The monolithic float glass forming chamber as claimed in claim
17, wherein the mixture of the pumpable and castable material and
the insulation material comprises from about 40 to about 65% by
weight of Al.sub.20.sub.3; from about 55 to about 30% by weight of
Si0.sub.2; 3.5% by weight of a mixture of Ti0.sub.2 and
Fe.sub.20.sub.3 and CaO; and 0.5% by weight of Na.sub.20 and an
additive as carlita, thermolita, perlita, verelite or a mixture of
the same.
22. The monolithic float glass forming chamber as claimed in claim
17, wherein the monolithic float glass forming chamber includes a
bottom refractory wall; and, a roof refractory wall.
23. The monolithic float glass forming chamber as claimed in claim
22, wherein the bottom refractory wall comprises: a first bottom
wall and side walls, said side walls being separated one of the
other on two lateral sides of the first bottom wall, said first
bottom wall and side walls being manufactured with a mixture of the
castable refractory material and an insulation material on a casing
having bottom and side walls; and, a second bottom wall and second
side walls manufactured of the castable refractory material on said
first bottom wall.
24. The monolithic float glass forming chamber as claimed in claim
23, wherein the second side walls and second bottom wall includes:
a gap between the second side walls and second bottom wall to
prevent gases diffusion to cause bubble faults in the glass
production.
25. The monolithic float glass forming chamber as claimed in claim
23, further includes metallic anchors which are welded at the
bottom and side walls of the casing to maintain fixed the first
bottom wall, the first side walls, the second bottom wall and
second side walls.
26. The monolithic float glass forming chamber as claimed in claim
23, further includes: a ceramic cushion material placed between
said side walls of the casing and the side walls of the first
bottom wall to provide a gap for the thermal expansion of the
refractory walls at the working temperatures.
27. The monolithic float glass forming chamber as claimed in claim
22 wherein the roof refractory wall comprises: a first roof
refractory wall manufactured of the castable refractory material,
said first roof refractory wall including first side walls to each
side of the first roof refractory wall; a sheet of metal layer on
the upper surface of the first roof refractory wall to prevents
diffusion and escape of gases from the float glass forming chamber
to the atmosphere; a second roof refractory wall manufactured with
a mixture of the castable refractory material and the insulation
material, said second roof refractory wall being placed on the
upper surface of the sheet of metal layer, said second roof
refractory wall including second side walls to each side of the
second roof refractory wall; wherein the first roof refractory
wall, the sheet of metal layer and the second roof refractory wall
includes hollow spaces to install heating or atmosphere supply
elements to control the operation of the chamber.
28. The monolithic float glass forming chamber as claimed in claim
22 wherein the bottom refractory wall; and the roof refractory wall
further includes: sealing means between said main bottom refractory
wall and the roof refractory wall, to provide access to an internal
part of the monolithic float glass forming chamber.
29. The method for the construction of a monolithic float glass
forming chamber as claimed in claim 13, wherein the roof refractory
wall further includes; providing removable sealing means to said
roof refractory wall, to provide access to the internal monolithic
float bath refractory structure.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is referred to a monolithic float
glass forming chamber and more specifically to a monolithic glass
forming chamber and a method for the construction of the same using
castable and pumpable refractory to form monolithic refractory
structures by sol-gel process on site of construction.
[0003] 2. Description of the Related Art
[0004] The recently developed sol-gel refractory technology, have
had its mayor and more widely application in the field of
metallurgical processes, like repairing and constructing linings
for molten metal containers and incinerators kilns.
[0005] In a research made on related art in present subject, has
shown that the application of such sol-gel refractory technology to
the glass manufacturing processes is relatively limited and mainly
focused towards the repair of some wear areas in the refractory
structures of the glass melting furnaces. Even more specifically,
none reference was found related with the application of such
sol-gel refractory technology for the construction of the
refractories for a float glass forming chamber.
[0006] In order to have a better understanding of the importance of
the method for the construction of the refractories structures for
the whole glass forming chamber, the following is an explanation
about the development of knowledge and skills that have been
applied trough the time in this part of the process for the glass
manufacture.
[0007] Since the beginning of the application of the float process
for the flat glass production about 50 years ago, the improvement
in the knowledge and skills in different concurrent specialties,
have resulted in very important advances incorporated in systems,
materials and methods in order to improve the process control and
the quality of the glass produced, besides increasing the length of
campaigns of the production units having now a day targets for 14
or more years of continuous operation.
[0008] In the case of the refractory materials that form part as
elements for the operation or compose within a float bath structure
in the float process for manufacturing flat glass better
compositions and better qualities have been developed to support
the particular conditions that prevail inside the forming chamber
and with glass contact positions. Also to meet such requirements
and overcome or solve different type of problems aroused through
the time in refractory materials located in each section of the
float bath. For example for the refractories used in canal, lip,
tweel and bottom blocking, different methods to manufacture had
been developed and the same tendency has being observed for the
roof tiles refractories assembly. Some examples are included in the
next references in order to explain the diversity and complexity of
such changes and developments incorporated in refractory materials
for the float glass process.
[0009] At the hot end of the float process, were the molten glass
coming from the melting process is continuously poured trough the
canal and lip into the float bath as it is explained in U.S. Pat.
No. 3,220,816, showing a method for delivering molten glass on the
molten tin in a controlled way and failing freely from the spout
lip to form a steady shape of glass flowing from the point of
contact of such glass with the surface of molten tin the glass
thereon by spreading laterally and flowing both backward and
forward.
[0010] To control the flow rate of glass entering the float bath
have been used a refractory element called tweel located in the
canal and before the lip, as is illustrated in U.S. Pat. No.
3,445,217, which states the use of a tweel formed by two different
refractories, one of them of a selected as glass wear-resistant
refractory forming the lower part in the glass contact section such
as fused cast zirconia, alumina or corundum material, and for the
upper portion of the tweel formed by a refractory material selected
for its mechanical strength and also for its resistance to thermal
shock such as the use of pre-fired fire clay bonded calcined
kyanite or sillimanite.
[0011] The U.S. Pat. No. 3,508,902 states the use of a refractory
shape named as a wetback tile which is contacted by the rearward
flow of the delivered flow of molten glass. It is stated by this
method that the main function of such wet back tile is to divide
the backward flow and direct the same backward flow of molten glass
outward each side so that it each flow may join the forward flowing
portion of the glass, helping to maintain a controlled and steady
flow and conducting certain kind of faults like bubbles and
inclusions coming from the area of the canal lip towards the edges
were do not affect the saleable section of glass ribbon.
[0012] In U.S. Pat. No. 4,099,950 it is stated the use of fused
silica as refractory material to conform both the tweel and the wet
back tile. The use of such material is considered an improvement in
order to avoid the presence any fine seeds attributable to
glass-refractory contact with tweel and wet back tile also prevents
possible presence of reams or non homogeneities fine lines with
different composition to that of the forming glass and coming from
the wear of the tweel.
[0013] In the case of refractories that constitute the roof of the
float forming chamber, also several improvements have been
incorporated through the time for example, in U.S. Pat. No.
4,311,508 using a castable refractory material and an arrangement
of anchors to support the roof refractory from the top in the
outside and to give a nearly flat and horizontal surface in the
interior of the roof. In the process for construction of such
structure are used forms made of metal or wood to support the
castable refractory while this hardens. Such refractory roof
structure considered to be nearly monolithic due to the fact that
contains small length of joints helps to prevent formation of
condensates from the atmosphere of the bath, reducing with this,
risks of drippings and also consequently reduce glass production
losses by this cause. Besides it is considered with this
arrangement to reduce the formation of cracks compared with the
conventional float roof design formed by interlocked refractory
tiles. As it can be seen this design still requires the use of an
arrangement of anchors to support the roof structure from the
outside.
[0014] Another important invention related with design and method
for construct the bath roof refractory is explained in U.S. Pat.
No. 4,340,412. It is stated the advantage of use a simplified roof
structure having a reduced number of vertically extending joints
and openings formed by relatively large refractory tiles made by
precasting refractory cement material giving pieces with a flat and
horizontal surface in the interior and suspended from the top by an
external metallic hanger arrangement. Such reduction in joint helps
to reduce the formation and dripping of condensed volatiles which
contaminates the glass ribbon and tend to cause production losses.
This in conjunction with the use of horizontal electrical heating
elements adapted from the side walls of the chamber so that no
openings through the roof structure need be provided for heating
elements.
[0015] In the case of the refractory bottom blocks which are a used
as a common practice in the float glass process. Such blocks made
of fireclay pre-fired in dimension generally 150 to 300 cm in
thickness and varying dimensions up to 50 to 70 cm in the side in
preferably in rectangular shapes several changes and improvements
in methods, material compositions and properties have been
incorporated trough the time in order to overcome or solve
different type of problems.
[0016] In U.S. Pat. No. 4,233,047, it is stated a procedure for hot
and in situ repair of delaminated float bath bottom refractory
blocks using blocks as inserts of high alumina with similar shape
to that of the delaminated section of clay block and containing
such high alumina repair insert block interconnected drills filled
with tungsten rods giving to such repair insert block a greater
density than the density of tin. This repair insert block will sink
and may be placed into the hole formed by the lost delaminated
block. This procedure for hot and in situ repair can avoid mayor
costs involved in the case to stop the process for a cold repair.
This procedure helps to prevent risks of glass faults as bottom
surface bubbles, risks of tin leakage due to tin attack to the
metal casing and other benefits as disclosed in same patent.
[0017] Another example of problem related with the use of blocks
and consequently extensive presence of joints in the bottom
refractory structure is explained in U.S. Pat. No. 4,036,626 in
which teaches a method for preventing tin leaks in a float bath
using metallic seals. Such metallic seal made of thin sheets of a
metal which can be located in the lower part of bottom blocks
joints and such metal sheet when in contact with molten tin, when
tin penetrates between block joints can form an alloy with higher
density and higher melting point than tin and by this way can seal
any point of penetration of tin through joints of bottom blocks
[0018] And related with procedures to manufacture or to build the
refractory structures required for the float bath process in the
forming chamber, one important factor that determines the design
and methods up to now used for such purpose is the fact that
refractories require to have their properties prior to their
installation in the structure, specially for the refractory bottom
blocks and for the refractory bath roof, the shapes require to have
a great accuracy in properties and dimensions in order to avoid
problems in their behavior during operation at working conditions.
As it is established in the method of construction for the float
glass forming chamber of the present application, the main
properties and design requirements for such refractory structures
can be obtained and improved by casting the same refractory
structures on site and making use of a relatively new toll applied
for the production of refractory materials called sol-gel
refractory technology. We have found that the refractory materials
obtained by this new technology provide several advantages for the
construction of float glass forming chambers and eliminating
several problems found in the past. With the method of the present
application it is possible to construct refractory structures for
the float glass forming chamber using the casting technique and the
new sol-gel refractory technology eventually in three parts; that
is, the bath bottom refractory section, the side wall refractory
section and the bath roof refractory section.
[0019] The bath bottom refractory section and the side wall
refractory sections are made by casting the refractory composition
to form a monolithic structure. This allows having the refractory
structure with eventually cero expansion joints exposed to molten
tin on which the glass floats to be formed.
[0020] In the case of the bath roof refractory section, the method
of construction, also allows to have a monolithic refractory
structure with flexible access for maintenance of electric heating
elements necessary to have a better control for the glass forming
process.
[0021] The development of the sol-gel refractory technology can be
derived for example with U.S. Pat. No. 5,900,382. In such patent it
is stated the use of aqueous silica sol to form a binder in
conjunction with phosphate and magnesia as accelerator for the
process to gel. Such refractory binder found to be very useful to
obtain refractories materials with wide compositions like alumina,
zirconia, mullite and also alumina silicates that can harden and
have good properties after short time of drying at room temperature
and without requirement of firing as it is the common practice for
mayor types of refractory materials.
[0022] The sol-gel refractory technology has had mayor application
in the metallurgical processes for the production of iron and
steel. In these processes the sol-gel refractory technology is
applied for the repair and construction of refractories linings as
it is stated in U.S. Pat. No. 5,632,937. In such patent it is
explained a method for applying a refractory lining directly inside
a metallic vessel with reduced access for the installation of molds
prefabricated and instead of this, such forms or molds are
assembled inside the metallic vessel and the refractory lining is
formed using a castable refractory compositions prepared also in
situ. Such castable refractory compositions are cast between the
forms and the metallic vessel giving the required refractory lining
after allowing hardening. Such method to apply the refractory
linings has been proved to reduce the costs and time of such
operation and can be applicable also to other kind waste
incinerators and rotary kilns.
[0023] More recently, some applications of the sol-gel refractory
technology for the glass manufacture process have been done as it
is stated by in U.S. Pat. No. 7,176,153. Such patent describes the
method for repair a glass melting furnace using colloidal silica
refractories and containing mixtures with alumina, zirconia and
silica compositions with a silica binder. This method for the
application of such colloidal silica refractories is by means of
casting, pumping, or shotcreting and mainly directed for the repair
of wear parts of glass melting furnaces whether using cast blocks
previously prepared or applying directly onto the wear section of
the refractory structure and mainly located in contact with molten
glass, that is the bottom and side wall refractories of the glass
melting furnace. Such invention, states that similar repairs can be
done on other parts of the glass melting furnace apart from the
bottom and side wall refractories and using same colloidal silica
refractories containing mixtures of alumina, zirconia and silica
compositions with a silica binder.
[0024] As it was stated, in the search carried out on the related
art, no applications of the sol-gel refractory technology have been
found to the construction of the refractories used in the forming
chamber for the float glass manufacturing processes.
SUMMARY OF THE INVENTION
[0025] Thus, one objective of the present invention is to provide a
monolithic float glass forming chamber and method of construction,
using refractory materials obtained by sol-gel refractory
technology.
[0026] A main objective of the present invention is to provide a
monolithic float glass forming chamber and method of construction,
wherein the main refractory structures can be constructed on site
by the casting technique in three parts; these are; the bath bottom
refractory section, the side wall refractory section and the bath
roof refractory section. The bath bottom refractory section and the
side wall refractory section being made by casting the refractory
composition to form monolithic refractory structures. This allows
having the refractory structure with eventually cero expansion
joints exposed to molten tin on which the glass floats to be
formed.
[0027] Is other objective of the present invention to provide a
monolithic float glass forming chamber and method of construction
which in case of the bath roof refractory section allows to have a
monolithic refractory structure with flexible access for
maintenance of electric heating elements necessary for the glass
process.
[0028] An additional objective of the present invention is to
provide a monolithic float glass forming chamber and method of
construction which allows repairing exclusively damaged points in
terms of areas and thickness of the refractory sections at the end
of campaigns in an easier way and with lower costs using the same
procedure and same composition of material instead of removing
whole blocks as it is required in traditional procedure.
[0029] Is another objective of the present invention to provide a
monolithic float glass forming chamber and method of construction
that uses for the construction of the refractory structure, a new
refractory material commercially available in the market by
companies like Magneco Metrel, Inc. The material selected for this
method has been the Metpump IPSX G which have proved to have
acceptable properties for use in float baths in contact with molten
tin and bath atmosphere and have the next chemical composition;
approximately 60/65% Al.sub.2O.sub.3, 30/35% SiO.sub.2, 3.5%
(TiO.sub.2+Fe.sub.2O.sub.3+CaO) and 0.5% Na.sub.2O. Another
compositions evaluated which gave also good results have as main
component 40, 50 and 90% Al.sub.2O.sub.3. This type of material
have been developed using the sol-gel technology, giving a
colloidal silica refractory structure, which have several important
properties, like low porosity, low thermal expansion, low gas
permeability, high homogeneity, high hot strength, etc.
[0030] Other objective of the present invention is to provide a
monolithic float glass forming chamber and method of construction
that avoids the need for the refractory to be previously fired for
use at high temperatures and can be easily cast to have the
required shapes directly on site of the construction.
[0031] These and others objectives and advantages of the monolithic
float glass melting forming chamber and method of construction of
the present invention can be viewed by the experts in the area in
the following detailed description of the preferred embodiments of
the invention, which will be placed within the scope of the
invention claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1, is a plan view showing the principal sections of a
monolithic float glass forming chamber for the float glass
manufacturing process;
[0033] FIG. 2 is a cross section of the float glass forming chamber
in the zone for heating and cooling equipment of the forming
section of the chamber; and,
[0034] FIGS. 3 and 4, shows schematic views of the construction of
metal anchors to fix the bottom refractory structure to the bottom
metal casing.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The monolithic float glass forming chamber and method of
construction using castable and pumpable refractory to form
monolithic refractory structures by sol-gel process on site of
construction will be described below making reference to the
specific embodiments of the same and to the drawings enclosed as
figures, where the same signs refer to the same parts of the shown
figures.
[0036] Making reference particular to the FIG. 1 is a plan view
showing the principal sections of float glass forming chamber for
the manufacture glass plates which consists of a forming section
(A) and a cooling section (B). The molten glass flows entering the
bath to float on molten tin at the hot end (C), through of a zone
for heating and cooling equipment (D and E) and where forced to a
exit end (F) by mechanical equipment wherein a glass ribbon is
forced whether pulling or retaining it in order to have the
required thickness profile and where also simultaneously it is
required to control the glass temperature whether removing heat
using a series of water cooled steel pipes or adding heat using a
system of electric heating elements.
[0037] The FIG. 2 is a cross section of the float glass forming
chamber in the zone for heating and cooling equipment of the
forming section of the float bath structure, which will be now
described. As can be of the FIG. 2, the structure of the refractory
construction made by the method of the present invention comprises:
a bottom casing (1) which is a thick plate of steel that supports
and contents the refractory assembly, in conjunction with the
sidewall casing (2) also made with steel plate. To the bottom
casing (1) and side wall casing (2) are welded a system of metal
anchors (3) made of steel cold rolled and small rounded steel
plates (SP) as shown with more detailed in FIGS. 3 and 4. The first
layer of refractory material is composed of an insulation material
(5) which is a pumpable and castable refractory material that has
the next properties after solidified or hardens; a low heat
transfer coefficient, low density and also low thermal expansion.
The main layer of refractory is composed of the bottom refractory
(6) and the main side wall refractory (8). Between these two
sections of refractories is left a perimeter bottom expansion gap
(7), whose main purpose is to provide a refractory discontinuity to
avoid any risk of bubble generation by gas diffusion. Such main
layers of refractory are made of a castable refractory material
with specific characteristics and properties in terms of porosity,
gas permeability, thermal expansion and chemical composition, these
characteristics and the method to produce such refractory structure
are proved to allow the material to perform in a superior way in
terms of durability at the extreme working conditions like high
temperatures, molten tin attack and alkali chemical attack, thermal
changes, etc. together with a consistence stable behavior to allow
a minimum affectation to the quality of the glass ribbon due to
bubble generation by refractory porosity and gas permeability.
Between the side wall casing (2) and the cast refractory insulation
material (5) is a layer of ceramic cushion material (4), which
provides a necessary gap for the thermal expansion of the
refractory system at the working temperatures.
[0038] In the roof refractory, it is considered the use of a side
support columns (9) made of steel where are supported the side
structure support (10) also made of steel to support the roof
refractory assembly. The inner refractory section is formed by the
roof refractory (11), made of a castable refractory material with
specific characteristics and properties in terms of porosity, gas
permeability, thermal expansion and chemical composition, these
characteristics and the method to produce such refractory structure
are proved to allow the material to perform satisfactory in terms
of durability at the specific working conditions like temperatures,
gases atmosphere and including presence of alkalis in the vapor
phase, thermal changes, etc. On top of such main layer of
refractory, it is located the insulation refractory material (13),
which is also a castable refractory material and that after
solidified has properties like; low heat transfer coefficient, low
density and also low thermal expansion. Through the two layers of
refractory materials are left enough accesses to install the
electric heating modules (14) that supply the required energy for
the temperature control to form the glass ribbon. Such electric
heating modules (14) have the advantage that can be replaced when
it is necessary, for example by breakage or chemical degradation.
Also through of the two layers of refractory, are left accesses for
the atmosphere supply or pyrometers (15). Such accesses are used
whether for supply atmosphere (a mixture of nitrogen and hydrogen)
or to install supports for pyrometers at desired positions in order
to allow the measurements of temperature of glass ribbon for the
process control. Between the side structure support (10) and the
main side refractory (8), it is the side sealing (12), formed by
metal boxes filled with insulation material and that can be
removable when necessary to provide access and windows to the
internal process through all the perimeter of the float bath.
[0039] Under the process of the present invention the refractory
sections can be made by the casting technique eventually in two
parts, that is the bath bottom refractory section and the roof
refractory section
[0040] In the case of the bath bottom refractory section and in
order to understand in a better way the present invention it is
important to explain the following. Traditionally in the
construction of float baths has been required the use of big size
refractory blocks to be installed in the bottom structure to
contain the liquid tin and to give the stable and controlled
thermal and mechanical support for the continuous glass ribbon
which is processed at temperatures from 1,100.degree. C. at the hot
end (C) to the 600.degree. C. at the exit end (F). The fact of use
molten tin for the float glass process, influence in several ways
the engineering of the design. One very important aspect is the big
difference in density between tin (7.3 gr/cm.sup.3) and common
refractories (around 2.5 gr/cm.sup.3) for the glass process. This
big difference in densities requires assuring to maintain the
bottom refractories in their position and to avoid the strong force
of buoyancy, besides to reduce at the minimum as possible the
length of extension of joints between refractory blocks because
such joints can act as potential sources for bath bubble faults and
other type of problems.
[0041] Under the method of the present invention the construction
of the bath bottom refractory is made eventually in one piece and
without none joint area. To obtain this, the next steps are
performed.
[0042] A system of metal anchors (3) is welded to the bottom and
side wall casings (1) and (2), to maintain fixed the refractory
basement. Such metal anchors are made with rolls %'' diameter and
flat rounded plates of 4 in. diameter and 1/4 in. of thickness.
Such metal anchors are welded prior to the casting of refractory
materials. Important factors in the design of anchors are to
consider the use of a low expansion steel and high resistance to
oxidation like for example a 309 or 310 stainless steel. Also
important is to avoid acute shapes and instead have curved shapes
and edges to minimize tendency to cracks generation to refractory
structure.
[0043] The insulation refractory material (5) is formed by casting
a castable refractory mixture in a composition for example from 40
to 50% Al.sub.2O.sub.3 and any of the next additives as carlita,
thermolita, perlita or verelite, which can supply insulation
properties to the refractory structure formed by sol gel process
with good mechanical and thermal properties. The insulation
refractory material mixed with the insulation additive can be
formed in a required thickness that can be from 10 to 20 cm. By
means of common hand vibrators bars is assured to get the desired
density of such castable mixture, removing excess of trapped air
and to avoid cavities. Firstable it is formed the bottom part and
after can be formed the sidewall insulation by the help of a wall
of contention using metal plates to give the required space to form
by casting the complementary refractory material.
[0044] In a similar way, the main bottom refractory (6) and main
side refractory (8) layers are formed by casting a castable
refractory mixture and in a required thickness, preferably from
about 10 to about 20 cm. By means of common hand vibrators bars is
allowed to get the desired density of such castable mixture,
removing excess of trapped air and to avoid cavities. Firstable it
is formed the bottom part and after is formed the main sidewall
refractory by means of a wall of contention using metal plates as
forms or moulds to give the required space to form by casting the
complementary refractory material and also to leave the perimeter
expansion gap (7) which its main purpose is to prevent gases
diffusion to cause bubble faults in the glass production.
[0045] Once the main bottom refractory layer is formed, the upper
surface is polished by means of a floor rotary polishing machine,
to eliminate possible imperfections like roughness, and to have a
desired flat and smooth surface.
[0046] On the other hand to construct the bath roof refractory
section using the method of the present invention, the next main
steps are performed.
[0047] To a side metal support columns (9) are fixed the metal side
structure support (10) for support the roof refractory (11) and the
insulation refractory material (13)
[0048] Firstly, a metallic or wood structure is formed, which
contains the shape of the roof refractory (11), said structure
comprising a pair of parallel plates to each side, leaving an space
between each other, to form side support walls; and a removable
arch structure of a convex-shaped to form the roof, having an
internal space, which is resting on the support walls. The
structure is rested on the lower part (LP) of the metal side
structure support (10), leaving a parallel space PS between the
side structure support (10) and the structure S.
[0049] After the structure is filled with a castable refractory
material, in a required thickness that can be from 10 to 20 cm and
by means of common hand vibrators bars, it is allowed form the
desired density of such castable mixture removing excess of trapped
air and to avoid cavities. In this step prior to cast the bath roof
refractory (11), it is important to leave the required spaces for
access for electric heating modules (14) and access for atmosphere
supply or pyrometers (15) using sections of polystyrene (or
equivalent material) pieces made with the required and slightly
conical shape (from 5 to 10.degree.) and prepared in the surface
with lubricant grease or a double thin plastic film, in order make
easy the removal when the refractory mixture hardens. After, the
castable refractory material has been casted and the roof and side
walls (main bath roof refractory 11) have been formed, the metallic
or wood structure is disassembled.
[0050] Once that the bath roof refractory (11) is formed, a thin
sheet of metal layer (17) and preferably made of stainless steel
with high resistance to oxidation and with low expansion
coefficient is placed on the upper surface of the bath roof
refractory (11). This sheet of metal (17) prevents diffusion and
escape of gases to the atmosphere.
[0051] Finally a metallic or wood cover is placed over the bath
roof refractory (11), which is supported on the each side structure
support (10), leaving a space between the upper part of the sheet
layer (17) and the metallic or wood cover, in order to be filled
with the mixture of the castable and pumpable refractory material
and the insulation material to form the complementary insulation
wall (13). The castable refractory material is preferable a
composition from 40 to 50% Al.sub.2O.sub.3 and any of the additives
such as carlita, thermolita, perlita, verelite or mixture of the
same, which can supply insulation properties to the refractory
structure formed by sol gel process with good mechanical and
thermal properties. The mixture of insulation refractory material
and additive can be formed in a required thickness that can be from
10 to 20 cm and by means of common hand vibrators bars it is
allowed form the desired density of such castable mixture removing
excess of trapped air and to avoid cavities. In this step, the
extension of required spaces for access for electric heating
modules (14) and access for atmosphere supply or pyrometers (15)
using the same sections of polystyrene (or equivalent material)
with a slightly conical shape (from 5 to 10.degree.) prepared and
left in the main bath roof refractory. After the monolithic
refractory structure has harden, the polystyrene (or equivalent
material) shapes, are removed and also it is removed the metallic
or wooden structure to allow to continue to dry the refractory
structure to the ambient air at room temperature.
[0052] Side supports tensors (16) assure the required rigidity to
the structure caused by the weight of the roof refractory assembly
transmitted to the side structure support (10).
[0053] According with an evaluation made on differential chemical
compositions (40, 50, 60, 70 and 90% Al.sub.2O.sub.3) of several
considered refractory material compositions and prepared by casting
to be used with the method of the present application, following
are a resume of results compared with a standard 40%
Al.sub.2O.sub.3 refractory material commonly used for bath bottom
blocking. The evaluation consisted mainly in the next points and
related with behavior inside float bath at 1100.degree. C. during
30 days in terms of cold crushing strength and metal Sn and
Na.sub.2O vapor penetration in their structure. Also were tested
the thermal shock resistance in cooling cycles to room temperature
in air and with more intense conditions of thermal shock tests
cooling submerging in water at room temperature.
TABLE-US-00001 Standard 40% 40% 50% 60% 70% 90% Composition Al2O3
Al2O3 Al2O3 Al2O3 Al2O3 Al2O3 % Na2O increased in surface 0.393
0.234 0.171 0.129 0.218 0.408 composition after 30 days inside
Float Bath at 1100.degree. C. % Sn increased in surface 0.00 0.00
0.00 0.029 0.00 0.00 composition after 30 days inside Float Bath at
1100.degree. C. Cold crushing strength after 19 20 25 35 24 45 30
days inside Float Bath at 1100.degree. C. (MPa). Number of thermal
shock +20 +20 +20 +20 +20 +20 cycles (1000.degree. C.-Air room
temperature-1000.degree. C.) Number of thermal shock 19 +40 +40 +40
+40 +40 cycles (1000.degree. C.-Water room temperature-1000 C.)
[0054] The above results show that silica colloidal compositions
with 40, 50, 60 and 70% Al.sub.2O.sub.3, have lower Na.sub.2O
penetration compared with standard 40% Al.sub.2O.sub.3. In terms of
cold crushing strength, all silica colloidal refractory
compositions 40, 50, 60, 70 and 90% Al.sub.2O.sub.3, have better
resistance compared with standard 40% Al.sub.2O.sub.3. In case of
Sn penetration analysis, only colloidal compositions with 60%
Al.sub.2O.sub.3 showed signs of metal penetration. And also a very
important test carried out, that is the Thermal shock evaluation,
showed a better resistance with all silica colloidal refractory
compositions 40, 50, 60, 70 and 90% Al.sub.2O.sub.3 compared with
standard 40% Al.sub.2O.sub.3.
[0055] All the above is in understanding that the aforesaid
description of the invention, is only provide in order to show the
specific embodiments of the same and the better way to develop it
as of the time when this patent application is flied and the
invention will not be limited to these, but its scope must be
considered regarding to the following claims:
* * * * *