RU2714415C1 - Method of preparing charge for alkali-silicate glass - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention can be used in glass industry for preparation of charge of alkali-silicate glasses, including glass alkaline silicates. Disclosed is a method of preparing a glass mixture for producing alkali-silicate glasses, including glass alkaline silicates, involving activation of the silicon-containing component of the glass mixture using sodium hydroxide as a sodium-containing component to obtain CCM having chemical composition corresponding to eutectic in oxide system NaO-SiO.EFFECT: disclosed is a method of preparing a glass mixture for producing alkali-silicate glass.1 cl, 7 dwg

Description

The invention can be used in the glass industry for the preparation of mixtures of alkali-silicate glasses, including glassy alkaline silicates.

The use of blends prepared by the disclosed method allows to intensify the reaction of silicate and glass formation in the charge and melt, to reduce the maximum temperature and time of glass melting, to increase the specific removal of glass melt, to reduce the technogenic load on the environment in comparison with the previous inventions. One of the ways to intensify glassmaking is the preliminary activation of the refractory components of the glass mixture using hydroxides. The result of the activation of a silicon-containing crystalline raw material source of a glass mixture using sodium hydroxide to obtain a good classified synthetic raw material (CCM) / 1-6 /.

Common to the technological schemes for producing CCM in the presented analogues is the complete replacement of the sodium-containing component of the glass mixture (traditionally soda ash) with sodium hydroxide, heat treatment of the caustic reaction mixture (in the form of a solution or in solid form) and quartz-containing raw materials in the range 325-700 ºС for 1 -5 minutes. The resulting powdery powder product in chemical composition consists of oxides of Na ₂ O and SiO ₂ in mass fractions close to alkaline silicate glass. The phase composition of the SSM is represented by amorphous and crystalline phases in the form of low-temperature quartz, sodium meta- and di-silicate. The chemical composition of the CCM corresponds to the selected glass composition.

An analysis of the CCM chemical compositions for the most common types of alkali-silicate glasses (tare, float, medical) in the part of the Na ₂ O - SiO ₂ binary oxide system showed that the region of the two-component composition CCM compositions (Na ₂ O; SiO ₂ ) lies in the region enriched with SiO _2, wt.% (80.85 - 85.62) and "depleted" content of Na ₂ O, wt.% (19.15 - 14.38), as is possible from the phase diagram (Fig. 1). According to (Fig. 1), this means that despite the intensification of the processes of silicate formation in the SSM before loading into the furnace, the chemical compositions of the SSM do not correspond to the eutectic compositions in the Na ₂ O - SiO _{2 system} with eutectic temperatures, ºС (1022; 846; 793) , which may cause a later appearance of the liquid phase in the CCM-based charge upon heating in the furnace, than this is supposedly possible.

A prototype may be a method of preparing a charge for alkaline silicate glass (Partial Selective Batching, Eng.), Providing for the separation of silicon, sodium and calcium-containing charge raw materials into parts (Na ₂ CO ₃ + quartz) and (CaCO ₃ + quartz ) with mass fractions corresponding to the eutectic composition Na ₂ O - SiO ₂ and CaO - SiO ₂ system, Na ₂ O - CaO -SiO _2, followed by mixing and granulation / 7 /. However, soda ash is used as the sodium-containing component; activation of the most refractory component of the glass mixture — quartz — is not activated according to the proposed method at the stage of preparation of the mixture; part of the quartz sand in free form (about 20% of the total) is added to the mixture, consisting of two granular products (Na ₂ CO ₃ + quartz) and (CaCO ₃ + quartz), which can contribute to the segregation of the mixture due to the difference in the size of the granules products and grains of quartz sand, and bulk density of materials; the use of quartz sand in the mixture in a free form increases both the dissolution time of quartz grains in the melt and the total time of glass melting.

The objective of the disclosed invention is a method of preparing a glass charge for producing alkaline silicate glasses, including glassy alkaline silicates, including the activation of a silicon-containing component of a glass mixture using sodium hydroxide as a sodium-containing component, to obtain CCM having a chemical composition corresponding to the eutectic in the oxide system Na ₂ O - SiO ₂ .

This object is achieved in that the quartz-containing component of the glass charge and sodium hydroxide used as the sodium-containing component are divided into initial mixtures to obtain CCM, the ratio of weight parts (including) in one of which is expressed

(NaOH _eut : Quartz _eut .) (1)

and corresponds to the eutectic composition in the oxide system Na ₂ O - SiO ₂ , and the ratio of mass parts in another mixture is expressed

((NaOH _total .- NaOH _eut .): (Quartz _obs. -Quartz _eut .)), (2)

where NaOH _total and Quartz _obsh . - weight parts of the total amount of sodium hydroxide and quartz-containing raw materials for alkaline-silicate glass of a given composition. Thus, the obtained SSM has a chemical composition corresponding to the eutectic composition, and all quartz-containing material is physically chemically activated as a result of interaction with NaOH.

The invention is illustrated by the following graphic materials:

FIG. 1 with a phase diagram of a two-component system of Na ₂ O - SiO ₂ Krachek; the field bounded by points 1 and 2 corresponds to the region of the chemical compositions of the SSM.

FIG. 2 with a phase diagram of silica sand BC - 030-V, Q - low-temperature β-quartz.

Figure 3 with a phase diagram of a mixture of chemical composition, wt.%: Na ₂ O - 26.1; SiO ₂ - 73.9 from quartz sand and soda ash, heat-treated at 400 ºС. The main phase is crystalline in the form of low-temperature β-quartz (Q) and soda ash (SA).

FIG. 4 with a phase diagram of a heat-treated product at 325 ° C of silica sand and sodium hydroxide, having a chemical composition, wt.%: Na ₂ O - 26.1; SiO ₂ 73.9. The main phases are amorphous and crystalline in the form of low-temperature β-quartz (Q) and sodium metasilicate (S). The presence of a compound characteristic of Na ₂ CO ₃ (SA) is noted.

FIG. 5 with scanning electron microscopic images of thin sections of CCM particles of chemical composition, wt.%: Na ₂ O - 26.1; SiO ₂ 73.9.

FIG. 6 with a scanning electron microscopic image of a thin section of a CCM particle.

FIG. 7 with a photo image of tabletted samples of a silicate-block mixture with n = 4 during heat treatment - 900ºС. 1 - sample of the mixture on quartz sand and soda ash; 2 - sample of the mixture on sodium hydroxide and quartz sand.

According to x-ray phase analysis, it was found that obtaining a CCM having a phase composition in the form of low-temperature quartz and sodium disilicate (Figure 4) is possible from the reaction mixture with a ratio of sodium hydroxide in the condensed state and quartz sand as 1: 100 v. h

The resulting ratio is the lower boundary for (2), which can be expressed (v.h.):

((NaOH _total .- NaOH _eut .); (Quartz _general .- Quartz _eut .)) ≥ (1; 100)

or

((NaOH _total .- NaOH _eut .) / (Quartz _general .- Quartz _eut .)) ≥ 0.01. (3)

The above method of preparation of the mixture will explain the examples of the calculation of the recipes of the charges CCM for some types of alkaline-silicate glasses, which do not limit the use of the disclosed invention:

Example 1

Calculation of the mixture recipe for CCM to obtain container glass composition wt.%: SiO ₂ –73; Al ₂ O ₃ - 2; CaO - 10; MgO - 2; Na ₂ O - 13.

Raw materials used in the preparation of the mixture: quartz sand BC-030-V; flake sodium hydroxide grade TP, (analytical grade), GOST 4328-77; technical soda ash, grade B; feldspar concentrate PShS-0.20-21; ground dolomite grade DM 20-0.10; lumpy limestone for the glass industry GOST 23671-79.

The recipe for a mixture using NaOH per 100 parts by weight of glass (parts by hour): silica sand - 67.62; PShS - 8.70; sodium hydroxide - 17.09; dolomite - 10.05; limestone - 12.38. Losses during insoles formation - 15.85%.

The recipe of the mixture using Na ₂ CO ₃ per 100 parts by weight of glass (parts by hour): silica sand - 67.62; PShS - 8.70; soda ash - 21.84; dolomite - 10.05; limestone - 12.38. Losses due to insoles - 20.38%.

The chemical composition of the SSM based on quartz sand and caustic, wt.%: SiO ₂ - 82.2; Na ₂ O - 17.8.

The eutectic point (Fig. 1), having a minimum temperature of 793 ° C of the appearance of the liquid phase in the oxide system Na ₂ O - SiO ₂ , has the following composition, wt.%: Na ₂ O - 26.1; SiO ₂ 73.9.

Based on the given values of the chemical composition of the SSM and the eutectic composition of the oxide system Na ₂ O - SiO ₂ , it is possible to obtain the SSM of the specified eutectic composition by activating 36.31 hours quartz sand, in the free (unactivated) form will remain 31.32 vol. quartz sand.

The amount of NaOH required for activation of 31.32v.h. quartz sand according to (3) is 0.31 v.h.

In accordance with (2), charge recipes for CCM:

- charge (A) corresponding to the eutectic composition, including: sodium hydroxide - 16.78; silica sand - 35.66

- charge (B) - to activate the remaining part of quartz sand, including: sodium hydroxide - 0.31; silica sand - 31.97

After processing the mixtures according to the most optimal methods presented in the patents / 1,2 /, based on the blends (A) and (B), we obtain two-component CCM (A) and CCM (B), which we mix with the rest of the raw materials of the alkali-silicate glass mixture packaging composition followed by possible agglomeration.

Comparative X-ray phase analysis of silica sand BC-030-B (Fig. 2), heat-treated samples of a mixture based on quartz sand and soda ash (Fig. 3) and a mixture based on sodium hydroxide and caustic prepared according to the disclosed method (Fig. 4 ), showed that, unlike the samples (Fig. 2,3), the phase composition of the sample (Fig. 4) is represented by the main phases in the form of amorphous and crystalline low-temperature β-quartz and sodium metasilicate. The presence of a compound characteristic of Na ₂ CO _{3 is} noted. The intensity of the peaks characteristic of the presence of the low-temperature form of quartz in the charge sample prepared in accordance with the invention was lower, and the peak shape was more “blurred” than in the sample (Fig. 3 ), which indicates a possible change in the structure of quartz, which contributes to the breaking of bonds of the silicon-oxygen skeleton at lower energy costs.

Scanning electron microscopy of SSM particles and their sections prepared in accordance with the invention showed that the core of the particle is a quartz grain with a surface layer in the form of compounds containing Si, O, Na (Fig. 5). A shell on a quartz grain has complex morphological structure with a thickness of 10-70 μm in the form of uniformly distributed clusters of crystalline formations. A distinctive feature is the formation of a near-surface shell in the defect channels of silica grain (Fig. 6), which together with the coating on the surface of silica grain contributes to the intensification of solid-phase reactions of charge materials.

Example 2

Calculation of the recipe for the mixture to obtain a sodium silicate block with n = 4, the following chemical composition, wt.%: SiO ₂ - 79.5; Na ₂ O - 20.5.

Raw materials used in the preparation of the mixture: quartz sand BC-030-V; flake sodium hydroxide grade TP, (analytical grade), GOST 4328-77.

The recipe for a charge for 100 parts by weight of glass, parts by weight: quartz sand - 79.46; sodium hydroxide - 27.30. Losses during glass formation - 6.78%.

SSM eutectic composition (Fig. 1) specified in Example 1 will contain 57.88 parts by weight quartz sand, in its free (not activated) form will remain 21.58 parts by weight quartz sand.

The amount of NaOH required to activate 21.58 v.h. quartz sand according to (3) is 0.22 v.h.

In accordance with (2), charge recipes for CCM:

- charge (A) corresponding to the eutectic composition, including: sodium hydroxide - 27.08; quartz sand - 57.41

- charge (B) - to activate the remaining part of quartz sand, including: sodium hydroxide - 0.22; silica sand - 22.06.

Getting CCM is similar to that described in Example 1.

The synthesis products of parts of quartz sand and sodium hydroxide are either used in the form of a mixture or agglomerates to obtain a silicate block of various modularities, or they are mixed with the remaining components of an alkali-silicate glass charge mixture, followed by possible agglomeration by known methods.

Comparative laboratory boiling of tabletted samples of the silicate-block from Example 2 (Fig. 7) showed that the sample on the carbonate mixture contained a larger amount of the gas phase in the form of bubbles up to 1-2 mm, as well as undissolved quartz grains.

A sample of the mixture prepared by the disclosed method contained a smaller amount of the gaseous phase, and the area of the melt with a more pronounced vitreous phase was larger than the area of the melt of the sample on a traditional basis.

Sources of information.

1. Patent 2597008. RF. Claim 08/24/2015. Publ. 09/10/2016.

2. Patent 2638195. RF. Claim 07/03/2016. Publ. 12.12.2017.

3. Patent 2007131721. RF. Claim 08/21/2007. Publ. 02/27/2009.

4. Patent 2152363. of the Russian Federation. Claim 06/18/1999. Publ. 07/10/2000.

5. Patent GB1411257 (A). US Declared 07/21/1972. Publ. 10/22/1975.

6. Patent US3817776 (A). FR. Claim 03/31/1970. Publ. 06/18/1974.

6. Patent US2008087044 (A1). US Declared 02/27/2003. Publ. 04/17/2008.

Claims (4)

A method of preparing a charge for alkali-silicate glass, comprising obtaining a water-soluble silicate shell on quartz grains due to heat treatment of the initial mixture of a source of quartz raw materials and sodium hydroxide to obtain a synthetic raw material having a chemical composition in the form of Na ₂ O and SiO ₂ , and the phase composition in the form the main amorphous and crystalline phases of β-quartz and sodium silicate, characterized in that they activate the silicon-containing component of the glass mixture using sodium hydroxide as the content of the sodium-containing component due to the fact that the total amounts of the quartz-containing material and sodium hydroxide are separated so that the weight parts in one mixture correspond to the eutectic mixture in the Na ₂ O - SiO ₂ oxide system, and the remaining part of the quartz-containing material for the formation of another mixture corresponds to the minimum amount of hydroxide sodium necessary to obtain a synthetic raw material, and in parts by weight, the ratio of the minimum value of the amount of sodium hydroxide in the condensed state necessary to obtain a synthetic raw material to a quartz-containing material is defined as: ((NaOH _total - NaOH _eut ) / (Quartz _obs - Quartz _eut )) ≥ 0.01, where NaOH _total and Quartz _total - weight parts of the total amount of sodium hydroxide and quartz-containing raw materials for alkaline-silicate glass of a given composition; NaOH _euth and Quartz _euth - weight parts of the total amount of sodium hydroxide and quartz-containing raw materials, corresponding to the eutectic composition in the oxide system Na ₂ O - SiO _2.

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