CN1307115C - Method of manufacturing glass and compositions therefore - Google Patents

Abstract

The invention relates to a method for producing glass. In particular, the present invention relates to a method of producing glass in a process of reacting materials in a glass melting furnace in either batch mode or continuous mode. These reactions affect the thermodynamic and other properties of the glass-forming reaction. The invention also relates to the compositions used in this reaction.

Description

Process for the production of glass and compositions therefor

field of invention

The invention relates to a product, a method for preparing the product and the application of the product in glass. More specifically, the present invention relates to a method for the production of solid particles particularly suitable for the production of glass products such as flat glass, fiberglass, glass containers, lighting glass, tableware and the like.

Background of the invention

The methods of producing glass and the materials it uses have evolved over millennia. Glass producers in particular have been and continue to be concerned with the compositional, thermodynamic and other characteristics of glass forming reactions in glass melting furnaces. Glass reactions generally involve the reaction of multiple materials resulting in compositions containing reacted and/or dispersed silica (silicon dioxide from sand, quartz, etc.), soda ash (sodium carbonate) and lime (from quicklime, slaked lime, etc. Calcium oxide) components and other optional components, these optional components are generally lead, lithium, cerium, iron, magnesium, potassium, barium metal oxides and borax.

Various concerns with these methods can be addressed by changing the starting materials and processing schemes for the reaction of these compositions. For example, these concerns include reacting portions of the material before producing the entire batch of glass. For example, one approach is to pre-treat the batch components by calcining the limestone and/or dolomite components to decompose the carbonates to oxides. This calcination liberates carbon dioxide from the added material, making the bulk frit. It is advantageous to remove the carbon dioxide prior to melting because this reduces the entrainment of gaseous inclusions in the glass. Other approaches involve attempting to use various components to influence the kinetics or quality or yield of the reaction. While progress is being made, there is still a need to develop processes and raw materials to improve the glass manufacturing process.

related technology

In US3082102, the batch mixture is heated prior to melting to effect a reaction between silica and soda ash to form sodium metasilicate. For soda lime silica glass, the temperature is limited to 820°C to avoid the generation of a molten phase that would cause blockage of the preheating equipment.

A similar process for the production of silicates by reacting the bulk mixture prior to melting is disclosed in US3682666, wherein the reaction temperature is reduced to 600-787°C. This scheme is made possible by the inclusion of a small amount of halide.

In US3817776 a method is disclosed in which preheated sand is partially reacted to form sodium silicate by contact with molten caustic soda. The remaining batch components were then added. The disadvantage of this method is the need to use caustic soda, which is more expensive than soda ash, as a sodium source for glassmaking. Additionally, processes in which solid and molten materials are in contact are more difficult to control and more prone to clogging than solid state reactions.

In US3883364 the dust problem in glass melting furnaces is reduced by providing a method of sintering alkaline earth metal carbonates charged into the glass melting furnace.

In US4248615 an energy efficient glass production method is provided in which the coagulant is pre-treated before it is added to the vertical bed used to form the glass.

An example of calcination pretreatment is disclosed in US4539030. Calcination requires temperatures in excess of 1600 (870°C), which avoids handling of the bulk mixture since such high temperatures would melt other components of the bulk mixture, especially soda ash or other sodium sources.

In US4920080 silica and sodium carbonate are reacted to form sodium silicate in the initial step of the glass melting process. The process preferably starts liquefaction by sintering the calcium carbonate-containing batch alone and then combining it with sodium silicate. The process material is preheated and preconditioned in two separate sections to optimize it before melting begins.

In the method provided by US5004706, the bonding problem of the glass batch is solved by pre-reacting a part of the glass batch.

Summary of the invention

The present invention discloses a method comprising preferentially reacting a portion of a batch of glass within a batch of glass. This preferential reaction is accomplished by reacting solid particles comprising a portion of the bulk frit, thereby creating a heterogeneous phase within the bulk frit. The components reacting in this preferential reaction are exothermic in nature and can effectively reduce the eutectic character of the bulk glass.

The invention discloses a method for producing glass with glass batch materials, the method comprising:

(a) Effectively mix calcium hydroxide, magnesium oxide, magnesium hydroxide, silicon dioxide, and water to form aggregates, which are solid particles that, when heated, initiate a solid-state reaction within the particles to generate new compounds calcium magnesium silicate;

(b) effectively mixing the solid particles with a second source of silica and a source of sodium oxide in a glass furnace to form a glass batch mixture, heating the glass batch mixture to initiate an exothermic reaction of the solid particles, thereby producing a glass batch Calcium magnesium silicate is formed in the mixture;

(c) then maintaining the temperature of the glass batch mixture to produce the final glass batch; and

(d) Molten glass products are produced from glass melting furnaces;

Wherein the average particle size of the solid particles is 0.018-0.14cm, and the respective weight ratios of the silicon material, the calcium material and the magnesium material of the solid particles are 0-1 part of calcium oxide and 0-1 part of magnesium oxide to 1 parts of silica.

The present invention also discloses a solid particle comprising silicon, calcium and magnesium capable of producing a heterogeneous phase within the batch of glass frit. The solid particles produced by the method of the present invention can be used in the production of glass products, such as flat glass.

The invention also discloses a glass produced from a glass batch comprising silica, soda ash, lime or limestone and solid particles containing silica, calcium hydroxide, magnesium oxide and magnesium hydroxide and other optional metal oxides combination.

The solid particles of the present invention are particularly suitable for the production of glass products, such as flat glass, fiberglass, glass containers, lighting glass, tableware, and the like.

Description of drawings

Figure 1 - Solid Particles in Float Glass

Figure 1 shows unreacted silica per pound of glass as a function of residence time at a temperature of 1400°C. The black line represents the comparative glass which is not the invention, the red line represents the invention (glass batch containing solid particles), and the black line requires a longer residence time than the red line to reach the point where there is no significant silica. The residence time is related to the melting rate of the glass, which in turn affects the throughput of the glass melting furnace. Thus, glass batches using the present invention melt faster, allowing for greater throughput in glass melting furnaces.

Figure 2 - Differential Thermal Analysis

Figure 2 shows the energy released or absorbed as a function of temperature for the comparative glass (red line) and the glass with solid particles (green line). The temperature of 900-1100°C shows that the calcium magnesium silicate reaction occurred in the experimental glass (green line). The nature of the reaction was clearly exothermic (compared to baseline). The comparative glass without solid particle aggregation showed an endothermic reaction, which is generally the case for most glass reactions by this mechanism. Overall, the figure shows evidence for the absence of calcium magnesium silicate phases in glasses not of the present invention. This calcium magnesium silicate not only contributes to the melting rate in Figure 1, but due to the exothermic nature of the reaction, energy can be injected into the batch of glass.

Detailed description of the invention

One embodiment of the invention is a method comprising preferentially reacting a portion of a glass batch within an overall batch of glass frit. This preferential reaction is accomplished by reacting solid particles comprising a portion of the bulk frit, thereby forming a heterogeneous phase within the bulk frit. The components reacting in this preferential reaction are exothermic in nature and can effectively reduce the eutectic characteristics of the bulk frit as compared to the eutectic characteristics without such selective reaction. The "eutectic nature" of a glass batch is defined as the temperature and reaction pathway required for two or more batch components in physical contact with each other to drive the glass-forming reaction and its effect on reaction kinetics and rate. Aggregates are "solid particles," meaning mixtures of compounds such as silica, calcium hydroxide, magnesium oxide, and magnesium hydroxide that, when heated, initiate solid-state reactions within the particles to form new compounds such as calcium-magnesium silicate .

In a preferred embodiment of the invention, solid particles comprising silica, calcia and magnesia material components form a heterogeneous phase and are located within the glass batch. The relative amounts of these three components are effective to effect an exothermic reaction when heated to the reaction initiation temperature. The solid particles are mixed with a stream containing the balance of other glass-forming materials prior to the exothermic reaction. These other glass forming materials may contain sodium materials and other silicon materials as well as various other materials required to produce the desired glass composition.

The silicon material of the solid particles is silicon dioxide, more preferably quartz powder. Preferred sources include sand, quartz flour, nepheline syenite and spodumene. To promote reaction kinetics favoring solid state reactions over standard glass reactions, the silicon material preferably has a particle size of 90% below 0.0075 cm.

The solid particulate calcium material is calcium oxide, more preferably calcium hydroxide. Preferred sources thereof include dolomitic lime, dolomitite, calcite, lime, colemanite, natural diopside and wollastonite, sorbite, gypsum, fluorspar, aragonite and feldspar. To promote reaction kinetics favoring solid state reactions over standard glass reactions, the calcium material preferably has a particle size of 90% below 0.0075 cm.

The solid particulate magnesium material is magnesium oxide, more preferably magnesium hydroxide. Preferred sources thereof include dolomitic lime, dolomitic limestone, natural diopside, brucite, periclase and Epsom salt. To promote reaction kinetics favoring solid state reactions over standard glass reactions, the particle size of the magnesium material is preferably 90% below 0.0075 cm.

These components of the solid particles, silicon material, calcium material and magnesium material, are each present in a weight ratio of about 0 to about 1 part calcium oxide and about 0 to about 1 part magnesium oxide to 1 part silicon dioxide.

More preferably, the respective weight ratios of these components of the solid particles, i.e. silicon material, calcium material and magnesium material, are about 0.4 to about 0.6 parts of calcium oxide and about 0.3 to about 0.4 parts of magnesium oxide to 1 part of bismuth silicon oxide.

The size of the solid particles should be of an order that promotes large and maintained uniform distribution of the material in the glass batch during the glass reaction. Thus, the solid particle size should be of a similar order of magnitude to that of the other glass batch components used in the bulk frit, and more preferably of the silicon source material, such as sand. Preferably, the median particle size of the solid particulate material should be from about 75% to about 500% of the median particle size of the balance silica material used to produce the glass batch, and even more preferably in the balance silica material. From about 85% to about 115% of the particle size.

The preferred solid particulate material is an inorganic solid particulate derived from a mixture of calcium oxide material, magnesium oxide material, silicon dioxide and water. The resulting solid particles have a particle size close to the balance of the sand used in the glass batch, preferably from about 0.018 cm to about 0.14 cm, more preferably from about 0.025 cm to about 0.085 cm.

The reaction product of the solid particles produced within the bulk frit may be a calcium magnesium silicate of the empirical formula (CaO) _x (MgO) _y (SiO ₂ ) _z , where the weighted value x with respect to the amount of silica and y are sufficient to produce an exothermic reaction. x, y and z preferably range from about 0 to about 3, from about 0 to about 1 and from about 1 to about 2, respectively. The calcium magnesium silicate product and other materials formed in the glass batch react as the entire glass batch system to produce the desired glass product. Additional energy is provided to the glass batch system to drive the glass forming reaction to completion. Preferably, the energy provided by the exothermic reaction is from about 5% to about 20% of the total energy required to react the entire batch of frit to form the desired glass product.

The following examples illustrate the invention without limiting the scope of the invention defined by the appended claims.

Example 1

The glass product has silicon, sodium, calcium, magnesium components measured in silicon dioxide ( _SiO2 ), sodium oxide ( _Na2O ), calcium oxide (CaO) and magnesium oxide (MgO) equivalents. In order to provide the silicon component of the glass, sand material is selected as the raw material, and the particle size of the sand is 30 mesh to 140 mesh. To provide the calcium and magnesium components to the glass batch, solid particles containing magnesium, silica and calcium components are added to the bulk glass frit. The solid particles are aggregated with water, dried and sieved. The solid particles contain silicon dioxide (SiO ₂ ), hydrated calcium oxide (Ca(OH) ₂ ), hydrated magnesia (Mg(OH) ₂ ), periclase (MgO) and water. This solid particulate material is combined with sand for the desired application in an amount capable of achieving the total silicon value of the glass batch. Soda ash is added to give the glass its sodium value. Limestone is used because the solid particles do not contain calcium values high enough for glass formulations. The bulk frit is heated to a temperature below the reaction temperature of the glass but sufficient to initiate an exothermic reaction in the solid particles.

An exothermic reaction begins to form calcium magnesium silicate material in the bulk frit. The heat generated by the external heat supply and exothermic reaction keeps the temperature of the bulk frit elevated continuously, and a glass reaction involving the calcium magnesium silicate material, sand, limestone, and soda ash occurs. In the glass batch vessel, the exothermic and glass reactions occur simultaneously for a period of time until all reactions are complete and glass is produced.

Claims (11)

1. A method for producing glass from a batch of glass, the method comprising: (a) Effectively mix calcium hydroxide, magnesium oxide, magnesium hydroxide, silicon dioxide, and water to form aggregates, which are solid particles that, when heated, initiate a solid-state reaction within the particles to generate new compounds calcium magnesium silicate; (b) effectively mixing the solid particles with a second source of silica and a source of sodium oxide in a glass furnace to form a glass batch mixture, heating the glass batch mixture to initiate an exothermic reaction of the solid particles, thereby producing a glass batch Calcium magnesium silicate is formed in the mixture; (c) then maintaining the temperature of the glass batch mixture to produce the final glass batch; and (d) Molten glass products are produced from glass melting furnaces; Wherein the average particle size of the solid particles is 0.018-0.14cm, and the respective weight ratios of the silicon material, the calcium material and the magnesium material of the solid particles are 0-1 part of calcium oxide and 0-1 part of magnesium oxide to 1 parts of silica. 2. The method according to claim 1, wherein the silicon material, the calcium material and the magnesium material of the solid particles are each in a weight ratio of 0.4-0.6 parts of calcium oxide and 0.3-0.4 parts of magnesium oxide to 1 part of silicon dioxide . 3. A solid particle for use in the production of glass, which solid particle is produced by effectively mixing calcium hydroxide, magnesium oxide, magnesium hydroxide, silicon dioxide and water, which when heated, initiates a solid state reaction within the particle, Generate a new compound calcium magnesium silicate. 4. The solid particle according to claim 3, wherein the empirical formula of the calcium magnesium silicate reaction product of the solid particle is (CaO) _x (MgO) _y (SiO ₂ ) _z , wherein the weight value relative to the amount of silicon dioxide x and y are sufficient to produce an exothermic reaction, where x, y and z range from 0-3, 0-1 and 1-2, respectively. 5. Solid particles according to claim 4, wherein the particle size is 0.018-0.14 cm. 6. Solid particles according to claim 5, wherein the particle size is 0.025-0.085 cm. 7. Solid particles according to claim 6, wherein the median particle size is 75-500% of the median particle size of the balance silica. 8. Solid particles according to claim 7, wherein the median particle size is 85-115% of the median particle size of the balance silica. 9. Solid particles according to claim 8, wherein the energy provided by the exothermic reaction is 5-20% of the total energy required to produce the desired glass product. 10. Use of solid particles according to any one of claims 3-9 for the production of flat glass. 11. A glass composition produced from a glass batch comprising silica, soda ash, lime or limestone, solid particles according to any one of claims 3-9 and other optional metal oxides.

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