WO2003057636A1

WO2003057636A1 - Method of manufacturing glass and compositions therefore

Info

Publication number: WO2003057636A1
Application number: PCT/US2001/049926
Authority: WO
Inventors: John Albert Hockman
Original assignee: Specialty Minerals (Michigan) Inc.
Priority date: 2001-12-27
Filing date: 2001-12-27
Publication date: 2003-07-17
Also published as: HK1070346A1; CA2467176A1; JP4219816B2; CN1558874A; BR0117185A; MXPA04005800A; CN1307115C; EP1458650A1; AU2002234091A1; JP2005514308A

Abstract

The present invention relates to the production of glass. In particular, the present invention relates to a method for the production of glass utilizing processes of reacting materials in a glass furnace in either a batch mode or a continuous process. These reactions affect the thermodynamics and other characteristics of the glass-forming reaction. The present invention additionally relates to compositions which are useful in such reactions.

Description

METHOD OF MANUFACTURING GLASS AND COMPOSITIONS THEREOF

FIELD OF THE INVENTION

The present invention relates to a product, a process for its preparation, and the use of such

product in glass. More particularly, the present invention relates to a process that produces a

solid state particle that is particularly useful in the production of glass products, such as flat

glass, fiberglass, container glass, lighting glass, tableware, and the like.

BACKGROUND OF THE INVENTION

Processes, and materials for such processes, for the manufacture of glass have millenniums of

development. In particular, glass manufacturers have been, and continue to be, concerned with

the components, thermodynamics and other characteristics of the glass-making reactions in glass

furnaces. The glass reaction generally involves the reaction of materials to produce a

composition containing the reacted and/or dispersed components of silica (silicon dioxide from

sand, quartz and the like), soda ash (sodium carbonate), and lime (calcium oxide from quicklime,

hydrated lime and the like) with other optional components, generally metal oxides of lead,

lithium, cerium, iron, magnesium, potassium, barium, borax and the like.

Various considerations have addressed such processes by varying the feed materials and the

process schemes for the reaction of such compositions. Such considerations include, for example, reaction of a portion of the materials before creating a total glass batch. For example,

one scheme is pretreatment of the batch constituents by calcining the limestone and/or dolomite

constituents so as to decompose the carbonates to oxides. This calcining releases carbon dioxide

from the material added to make the total glass batch. This elimination of carbon dioxide before

melting begins is advantageous since it reduces the entrapping of gaseous inclusions in the glass.

Other schemes involve using various components to attempt to effect the reaction's

thermodynamics or quality or yield results. While advances have been made, there still exists the

need for developing processes and feed materials to improve the glass-making processes.

RELATED ART

In U.S. Pat. No. 3,082,102, heating of the batch mixture is performed prior to melting to effect

reaction between silica and soda ash to produce sodium metasilicate. The temperature is limited

to 820. degrees Centigrade for soda-lime-silica glass to avoid producing a molten phase that

would lead to clogging of the preliminary heating apparatus.

In U.S. Pat. No. 3,682,666, a similar process of reacting the whole batch mixture to produce

silicates prior to melting is disclosed in which a lowered reaction temperature between

600. degrees Centigrade and 787. degrees Centigrade. Such is made possible by the inclusion of a

small amount of halide. In U.S. Pat. No. 3,817,776, a process is disclosed to partially react preheated sand grains to

sodium silicate by contact with molten caustic soda. The remainder of the batch ingredients are

added subsequently. This process has the disadvantage of requiring the use of caustic soda,

which is more costly than soda ash as a source of sodium for making glass. Also, the process of

contacting solids with molten material is more difficult to control and more prone to plugging

than a solid state reaction.

In U.S. Pat. No. 3,883,364, glass furnace dusting problems are reduced by providing a process

for sintering alkaline earth carbonate to be charged to a glass furnace.

In U.S. Pat. No. 4,248,615, an energy conserving glass manufacturing process is provided in

which agglomerants are preconditioned prior to supplying them to a verticle bed for glass

manufacturing.

In U.S. Pat. No. 4,539,030, an example of a calcining pretreatment is disclosed. Calcining

requires temperatures in excess of 1600 degrees Fahrenheit (870 degrees Centigrade), which

precludes treatment of the whole batch mixture because such temperatures would cause fusion of

other constituents of the batch, particularly the soda ash or other soda source.

In U.S. Pat. No. 4,920,080, silica is reacted with sodium carbonate to form sodium silicate in as a

preliminary step in a glass melting process. The method preferably calcines calcium carbonate-

containing batch materials separately before combining with sodium silicate as liquefying is initiated. The process materials are preheated and pre-reacted in two separate portions to

optimize prior to initiation of melting.

In U.S. Pat. No. 5,004,706, a process is provided to address problems of stickiness of glass

batches by pre-reaction of a portion of the glass batch.

SUMMARY OF THE INVENTION

The present invention discloses a process that includes preferentially reacting a portion of a glass

batch within the total glass batch. This preferential reaction is accomplished by reacting a solid

state particle containing a portion of the total glass batch thus effectively creating an in-

homogeneity in the total glass batch. The components reacted in this preferential reaction are

exothermic in nature and effectively lower the eutectic character of the total glass batch.

The present invention further discloses a solid state particle comprising silicon, calcium and

magnesium that creates an inhomogeneity within the total glass batch. The solid state particle

produced according to the process of the present invention is useful in the production of glass

products, such as flat glass.

The present invention further discloses a glass composition comprising silica, soda ash, lime or

limestone, a solid state particle containing silicon dioxide, calcium hydroxide, magnesium oxide,

and magnesium hydroxide, and other optional metal oxides. The solid state particle of the present invention is particularly useful in production of glass

product such as flat glass, fiberglass, container glass, lighting glass, tableware, and the like.

DESCRIPTION OF THE FIGURES

Figure 1 - Solid State Particle in Float Glass

Figure 1 shows the unreacted silica (stones) per pound of glass as a function of dwell time at a

hold temperature of 1400 Centigrade. The black line, representing the control glass without the

invention, requires a longer dwell time to reach a point without significant stones compared to

the red line representing the invention (glass batch with the solid state particle). The dwell time

relates to the melting rate of the glass, which in turn effects the throughput of the glass furnace.

Therefore, the glass batch using the invention will melt faster allowing for more throughput on

the furnace.

Figure 2 - Differential Thermal Analysis

Figure 2 shows the energy evolved or absorbed as a function of temperature for a control glass

(in red) and a glass using the solid state particle (in green). The temperatures between 900

Centigrade and 1100 Centigrade show the calcium magnesium silicate reaction in the

experimental glass (in green). This reaction is clearly exothermic in nature (compared to the

baseline). The control glass without agglomeration of the solid state particle shows an

endothermic reaction, typical of most glass reactions in this regime. In total, the graph shows the

evidence of a calcium magnesium silicate phase that would not exist in the glass if not for the present invention. This calcium magnesium silicate not only helps the melting rate as in Figure

I, but also imbues energy into the total glass batch due to the exothermic nature of the reaction.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention is a process that includes preferentially reacting a

portion of a glass batch within the total glass batch. This preferential reaction is accomplished by

reacting a solid state particle containing a portion of the total glass batch thus effectively creating

an inhomogeniety in the total glass batch. The components reacted in this preferential reaction

are exothermic in nature and effectively lower the eutectic character of the glass batch compared

to that eutectic character present without such selection. "Eutectic character" of a glass batch is

defined as the temperature needed by two or more batch components in physical contact with

each other to drive the glass-forming reactions as well as the path of the reaction and the impact

of such on the reaction kinetics and speed. "Solid state particle" refers to a mixture of

compounds such as silicon dioxide, calcium hydroxide, magnesium oxide, and magnesium

hydroxide that, when heated, will initiate a solid state reaction within the particle that concludes

with the production of a new compound such as calcium magnesium silicate.

In a preferred embodiment of the present invention, the solid state particle, comprising

components of silicon dioxide, calcium oxide and magnesium oxide materials, creates an

inhomogeniety and is located within the glass batch. The relative amount of these three

components is effective to produce an exothermic reaction when heated to a reaction initiation temperature. This solid state particle is admixed with a mass containing a balance of other glass-

forming materials prior to the exothermic reaction. Such other glass-forming materials may

contain sodium materials and additional silicon materials as well as various other materials

needed to produce the desired glass composition.

The silicon material of the solid state particle is silicon dioxide, and, more preferably, a silica

flour. Preferred sources of such include sand, silica flour, nepheline syenite, and spodumene.

Preferably the silicon material particle size is 90% less than 0.0075 Centimeters to promote a

thermodynamic advantage towards the solid state reaction versus the standard glass reaction.

The calcium material of the solid state particle is calcium oxide and, more preferably, a calcium

hydroxide. Preferred sources of such include dolomite lime, dolomitic limestone, calcite, lime,

colemanite, natural diopside and woUastonite, ulexite, gypsum, fluorspar, aragonite, and feldspar.

Preferably the calcium material particle size is 90% less than 0.0075 Centimeters to promote a

The magnesium material of the solid state particle is magnesium oxide and, more preferably, a

magnesium hydroxide. Preferred sources of such include dolomitic lime, dolomitic limestone,

natural diopside, brucite, periclase, and epsom salt. Preferably the magnesium material particle

size is 90% less than 0.0075 Centimeters to promote a thermodynamic advantage towards the

solid state reaction versus the standard glass reaction. The components of the solid state particle, the silicon material, calcium material and magnesium

material are in the respective molar ratios of from about zero (0) part to about one (1) part

calcium oxide and from about zero (0) part to about one (1) part magnesium oxide with respect

to one (1) part silicon dioxide.

More preferably, the components of the solid state particle, the silicon material, the calcium

material and the magnesium material are in the respective weight ratios of from about 0.4 parts to

about 0.6 parts calcium oxide and from about 0.3 parts to about 0.4 parts magnesium oxide to

one (1) part silicon dioxide.

The solid state particle size should be of a magnitude that promotes the attainment and retention

, of a homogenous distribution of material in the glass batch during the glass reaction.

Accordingly, the solid state particle size should be of a similar magnitude of the other glass batch

components, more preferably of the silicon source material, e. g. sand, used in the total glass

batch. Particularly, the median size of the solid state particle material should be from about 75

percent to about 500 percent of the median size of the balancing silicon dioxide material used to

produce the glass batch, even more particularly from about 85 percent to about 115 percent of the

median size of the balancing silicon dioxide material.

A preferred solid state particle material is an agglomerate of minerals produced by the admixture

of calcium oxide material, magnesium oxide material, silicon dioxide and water. The

agglomerate is formed to a particle size which approximates the sand balance to be used in the glass batch, preferably from about 0.018 centimeters to about 0.14 centimeters, more preferably,

from about 0.025 centimeters to about 0.085 centimeters.

The product of the reacted solid state particle, that occurs within the total glass batch, can be a

calcium magnesium silicate having an empirical formula of (CaO)_x(MgO)_y(SiO₂)_z , wherein the

weight values of x and y relative to the amount of silica is sufficient to produce an exothermic

reaction. Preferably, x, y, and z have the respective ranges from about zero (0) to about three (3),

from about zero (0) to about one (1), and from about one (1) to about two (2). The formed

calcium magnesium silicate product and the other material in the glass batch react as a total glass

batch system to produce the desired glass product. Additional energy to drive the glass-forming

reaction to completion is provided to the glass batch system. Preferably, the exothermic reaction

provides from about 5 percent to about 20 percent of the total energy needed to perform the total

glass batch reactions to produce the desired glass product.

The following examples are intended to illustrate the present invention, but not to limit the scope

of protection afforded by the claims hereafter:

EXAMPLE 1

A glass product is to have components of silicon, sodium, calcium, magnesium, measurable in

equivalents as silica dioxide (Si ₂), sodium oxide (Na^), calcium oxide (CaO), and magnesium

oxide (MgO). To supply the silicon component of the glass, a sand material is selected as a feed material. The sand has a size measurement of 30 mesh to 140 mesh. To supply the calcium and

magnesium components to the glass batch, the solid state particle containing the magnesium,

silica, and calcium components, agglomerated with water, dried, and screened, is added to the

total glass batch. The agglomerated (solid state) particles contain silicon dioxide (SiO,),

hydrated calcium oxide (Ca(OH)₂), hydrated magnesium oxide (Mg(OH)₂), periclase (MgO), and

water. This agglomerated particle material is combined with the sand to be used in an amount to

complete the total silicon value of the glass batch. Soda ash is added to supply the sodium value

for the glass. Since the agglomerated particle does not contain sufficient calcium value for the

glass formula, limestone will be used. The total glass batch is heated to a temperature below the

glass reaction temperature but sufficient to initiate an exothermic reaction in the agglomerated

particles.

The exothermic reaction begins the production of calcium magnesium silicate material in the

total glass batch. The temperature of the total glass batch continues to rise due to the supplied

heat and the exothermic reaction heat to produce a glass reaction involving the calcium

magnesium silicate material, sand, limestone, and soda ash. The exothermic reaction and glass

reaction occur simultaneously for a period within the glass batch vessel until all reactions are

completed producing a glass.

Claims

What is claimed is :

1. A process for manufacturing glass from a glass batch comprising:

(a) effectively admixing calcium hydroxide, magnesium oxide, magnesium

hydroxide, silicon dioxide, and water to produce an agglomerate;

(b) effectively admixing the agglomerate and a second source of silicon dioxide and a

source of sodium oxide to produce a glass batch admixture in the glass furnace under temperature

conditions such that an exothermic reaction of the agglomerate produces a solid state particle of

calcium magnesium silicate composition in the glass batch admixture;

(c) subsequently maintaining the temperature of the glass batch admixture to produce

a final glass batch; and

(d) producing a molten glass product from the glass furnace.

2. The process of claim 1 wherein the agglomerate is a solid state particle having an average

size of from about 0.018 centimeters to about 0.14 centimeters.

3. The process of claim 2 wherein the silicon dioxide material, the calcium oxide material

and the magnesium oxide material are in the respective weight portions of from about zero (0)

parts to about one (1) part calcium oxide and from about zero (0) parts to about one (1) part

magnesium oxide to one (1) part silicon diopside.

4. The process of claim 3 wherein the silicon dioxidematerial, the calcium oxide material

and the magnesium oxide material are in the respective weight portions of from about 0.4 parts to

about 0.6 parts calcium oxide and from about 0.3 parts to about one 0.4 parts magnesium oxide

to one (1) part silicon dioxide.

5. A solid state particle agglomerate used in manufacturing glass comprising admixing

calcium oxide, magnesium oxide, silicon dioxide, and water.

6. The solid state particle agglomerate of claim 5 wherein the solid state particle reactant is

calcium magnesium silicate, having the empirical formula of (CaO)_x(MgO)_y(SiO₂)_z .

7. The solid state particle agglomerate of claim 6 wherein the weight values of x and y

relative to the amount of silica is sufficient to produce an exothermic reaction, wherein x, y, and

z have the respective ranges of from about zero (0) to about three (3), from about zero (0) to

about one (1), and from about one (1) to about two (2).

8. The solid state particle agglomerate of claim 7 wherein the particle size is from about

0.18 centimeters to about 0.14 centimeters.

9. The solid state particle agglomerate of claim 8 wherein the particle size is from about

0.025 centimeters to about 0.085 centimeters.

10. The solid state particle agglomerate of claim 9 having from about 75 percent to about 500

percent of the median size of the balancing silicon dioxide.

11. The solid state particle agglomerate of claim 10 having from about 85 percent to about

115 percent of the median size of the balancing silicon dioxide.

12. The solid state particle agglomerate of claim 11 wherein the exothermic reaction provides

from about 5 percent to about 20 percent of the total energy needed to produce the desired glass

product.

I D . The solid state particle agglomerate of claim 12 utilized in the production of flat glass.

14. A glass composition comprising silica, soda ash, lime or limestone, a solid state particle

containing silicon dioxide, calcium hydroxide, magnesium oxide, and magnesium hydroxide, and

other optional metal oxides.