RU2187473C2 - Method of manufacturing block expanded glass - Google Patents

Abstract

FIELD: heat-insulation materials. SUBSTANCE: broken glass is dispersed, hydroxylated, and 2-25 wt parts of expanding mix are added to 75-98 wt parts of broken glass, said expanding mix being composed of, wt %: sodium liquid glass 0.5-5, activated carbon black with specific surface 75- 150 sq.m/g 0.2-1.5, sodium sulfate 0.5- 1.5, activated silica 0.6-12.0, boron oxide 0.2-5.0. Mix is granulated into particles 30 to 2000 mcm in diameter, loaded into metallic molds, compacted, and subjected to caking, foaming, and tempering. Resulting block glass is then annealed. Product shows high heat-insulation properties and volumetric water absorption no higher than 10% and can resist to mechanical loads no less than 0.5 kg/sq.cm. EFFECT: avoided stage processing starting mixture into special glass. 1 tbl, 3 ex

Description

 The invention relates to the production of effective functional heat-insulating materials with low values of thermal conductivity and density, to glassy silicate materials, in particular foam glass and its manufacture, and for the disposal of glassy wastes resulting from the accumulation of human life and industrial products of industrial and industrial origin.

Several methods are known for preparing block foam glass. For example, foam glass panels are formed by blowing air or other gas through a molten glass melt, the melt is cooled so that gas bubbles formed during the blowing are stored in a cooled glass / US patent 3151966, class. 65-22, from 06.10.64 g. /. Block foam glass is obtained by mixing finely ground glass with a foaming agent, which may contain a reducing agent in the form of a carbon ingredient and an oxidizing agent from sulfates, oxides, etc. The mixture is heated to a glass transition temperature and then softened or melted. During heat treatment, a redox reaction occurs between carbon and sulfates (oxidizing agents) and / or glass oxides. As a result, SO ₂ , CO ₂ , N ₂ , H ₂ S and other gases are formed in the glass melt, which form bubbles and impart a porous structure to the mass, which leads to the formation of materials with low density and high resistance to heat transfer by thermal conductivity and radiation. Best results are achieved when the structure consists or closed pores predominate, which makes the product impermeable to water, other liquids, water vapor and gases / US patent 5516351, 03 03 19/06 from 14.05. 1996 /.

 Block foam glass has significant positive qualities that make it useful for ultra-low temperature insulation, fire and thermal insulation, sound-absorbing, architectural and structural building material. In many cases, it is required that the block glass be waterproof, heat-resistant, and durable. Compared to wood-based materials, it is not subject to decay, resistant to various insects.

 The quality and properties of block foam glass depend on its apparent density, pore size and distribution, pore wall thickness, volumetric water absorption, etc.

 The disadvantages that reduce the quality include the heterogeneity of pore size and their distribution over the section of the block, increased wall thickness, high bulk density, the presence of residual stresses that reduce mechanical strength, a high proportion of permeable pores, and water and vapor saturation of the block foam glass. In addition, due to the high costs of glass melting and thermal processing of ingredients into block foam glass, large waste when cutting blocks into products of the desired style and size, foam glass products are relatively expensive.

 The most common is the production of high-quality block foam glass from specially welded and granular glass, which use scarce and expensive ingredients to improve its properties. It is considered acceptable to involve up to 20 wt.% Of certain types of glass waste in the charge. It is claimed that obtaining high-quality block foam glass from recycled container glass waste is a big problem / B.K. Demidovich. Foam glass. Publishing House "Science and Technology", Minsk. 1975 /.

The known method / US patent 5516351, C 03 B 19/06 from 14.05. 1996 / for producing block foam glass, which includes the use of ground glass and a foaming agent from the number of CaCO ₃ or CaSO ₄ , the specified particle size distribution, mixing them in the mill, filling out the form, displacing the air from the mixture by blowing it with SO _x and / or CO _x gases and heating to the foaming temperature, cooling and annealing, which allowed the use of glass of a mixed type. It is well known that the use of ingredients whose chemical reactions with glass are accompanied by gas evolution do not provide fine-porous block foam glass mainly and / or completely with pores evacuated from the external environment. Bulk density, heat-insulating, mechanical and other properties of such materials quickly and severely degrade in a humid atmosphere. The use of SO _x and CO _x gases increases the cost of production, has adverse environmental consequences and requires high costs for the capture and processing of gaseous emissions hazardous to operating personnel and the environment.

Closest to the claimed method is US patent 2775524, cl. 106-40 of December 25, 1956, according to which the cullet is dispersed with specially prepared materials from the diatomite group, silica with a specific surface of more than 10 m ² / g, containing carbon in the amount of 5-50 mass parts per 100 parts, based 0.08-0.15 wt.% Carbon by weight of cullet, heating to a temperature sufficient to soften and foaming the glass, cooling and annealing.

The method is most applicable when oxides of arsenic, antimony, vanadium, molybdenum, tungsten are involved in gas formation in redox reactions with a carbon ingredient and are practically not applicable for producing effective block glass with a low bulk density when SO ₃ (SO ₂ ) acts as an oxidizing agent.

Our studies show that, in principle, in addition to specially welded glass and provided that SO ₃ , As ₂ O ₃ , Sb ₂ O ₃ or their combinations are introduced into the composition of oxidizing agents, it is impossible to obtain an effective heat-insulating material with a low bulk density and closed pores using recyclable glass cullet .

 Considered in the prototype method does not solve the problem of disposal of accumulated in a large volume of domestic and industrial technical waste colorless alkaline aluminosilicate and colored glasses, because It does not provide for activation of redox interactions, stabilization of the foam, and expansion of the softening interval of glass without introducing the necessary amounts of active silica and doping the melt with boron oxide. Block foam glass from colorless recyclable glasses is obtained mainly with open pores, low mechanical strength and high water absorption. Block foam glass from recyclable colored glasses is obtained with a high bulk density, an uneven large porous structure, and caverns due to rupture of the walls and pooling of pores.

The purpose of the invention is to obtain effective functional block glass with improved performance: bulk density of 0.15-0.45 g / cm ³ , with high thermal insulation properties λ = 0.056-0.086 W / (m • K), volumetric water absorption of not more than 10%, capable of withstanding mechanical loading of at least 0.5 kg / cm ^2, and recycling the alkali aluminosilicate glass-waste container, window, medical, agricultural and other purposes glass discrete or arbitrary amounted smesevogo a.

This goal is achieved by the fact that in the known method for producing block foam glass, the glass cullet is dispersed to a specific surface of 6000-20000 cm ² / g, then it is hydroxylated to saturation with moisture 0.4-1.6 wt.%, And 2- to 75-98 wt.% Hydroxylated cullet 25% by weight of a foaming mixture comprising active carbon black with a specific surface area of 75-150 m ² / g as a carbon-containing component, sodium sulfate and additionally liquid sodium glass and boron oxide in the following ratio of ingredients, wt.%: Liquid soda 0.5-5.0 evoe glass, active carbon black having a specific surface area of 75-100 m ² / g 0.2-1.5 sodium sulfate 0.5-1.5, active silica 0,6-12,0, boron oxide is 0.2-5.0, mixed, granulated into particles with a diameter of 30-2000 microns, filled into a mold and compacted to an apparent density of 0.96-1.35 g / cm ³ , sintered at a temperature of 450-700 ^o C, foaming at a temperature of 450-700 ^o C, foaming, subjected to hardening at a temperature of 540-620 ^o With a speed of 80-300 ⁰ C / min and annealed foam glass at a temperature of 420-520 ^o C.

 The rank and values of the temperature parameters, concentration and ratio of ingredients, the dispersion of glass and the foam-forming mixture, the amount of gases formed, the structural and mechanical properties of the melt are determined by the functional orientation of the use of block foam glass in the declared values of the indicators of thermal conductivity, volumetric water absorption, strength, bulk density. The implementation of the method for the first time provides, bypassing the glass melting stage, the involvement for the production of effective types of block foam glass, glassy alkaline aluminosilicates accumulated over many previous years, sorted by type of glass or not sorted glass break.

 The proposed solution has a novelty, inventive step and is industrially applicable.

 The presented invention proposes for the manufacture of efficient block foam glass to use as a glassy alkaline aluminosilicate material in the form of used glasses for various purposes, which must be recycled, bypassing the stage of their melting into glass, intended for foaming by carrying out redox reactions accompanied by gas evolution and the formation of bubbles in molten glass.

 The inventive method can be processed into high-quality block foam glass, i.e. recycled individual glass containers, for example, bottle glass: colorless, green, brown, agricultural and medical glass containers, window and display windows, their various combinations and mixtures.

 In order to develop the method, the use of a wide range of recycled glass has been successfully determined as the initial glassy alkaline aluminosilicate.

 According to their technological features, they are divided into three groups in order of increasing scientific and technical problems of obtaining effective block foam glass. For example, bottle glass for spirits, green bottle glass, etc. 1st group: bottle, medical, agricultural brown glass, etc., 2nd group: window, transparent container glass, etc., 3rd group: green bottle glass, bottle for strong alcohol , a glass bottle for alcohol.

Dispersion of a glassy alkaline aluminosilicate should provide a specific surface area of 6000-20000 cm ² / g in the product. The dispersion values below 6000 cm ² / g require increased consumption of the carbon ingredient of more than 0.35 wt.% And high foaming temperatures of 840-860 ^o C, which leads to block foam glass with increased bulk density, and therefore increased thermal conductivity. The dispersion values in the range of 6000-20000 cm ² / g require less consumption of the carbon ingredient 0.15-0.35 wt.%, Lower foaming temperatures of 790-820 ^o With, and provide block foam glass of high quality with low bulk density, and low values of volumetric water saturation, and hence low thermal conductivity. The use of a glassy alkaline aluminosilicate with a dispersion of more than 20,000 cm ² / g is not economically and technologically feasible.

Hydroxylation of the surface of the cullet, that is, saturation with functional OH groups, to a moisture content of 0.4-1.6 wt.% Of recyclable glasses reduces the sintering temperature of the expandable mass and improves the porous structure of the block foam glass, it allows to reduce the foaming temperature by 15-20 ^{° C.}

A higher degree of hydroxylation creates great technological difficulties due to the formation of lumps and waterlogging of the mixture, which requires drying. The introduction, for example, of sodium sulfate in an amount of 0.5-1.5 wt.% Provides the oxidizing potential of the redox interaction with the carbon ingredient and the formation of the required volume of gases SO _x , CO _x , N ₂ , H ₂ S. With an increase in block size an increasing amount of oxidizing agent is required. At small amounts of less than 0.5 wt.%, Block foam glass with a low bulk density of less than 0.20 g / cm ^{3 is} not ensured, excessive carbon burning occurs in quantities of sulfate of more than 1.5 wt.% And informative open pores predominate in the block foam glass. increased sizes, increased water absorption.

The introduction of 0.15-1.5 wt.% Active carbon black with a specific surface area of 75-150 m ² / g makes it possible to obtain block foam glass with predominantly or fully autonomous pores with a size of less than 30-300 microns, with a decrease in the specific surface area of the carbon ingredient below 75 m ² / g decreases the efficiency of redox reactions, accompanied by the formation of bubbles in the mass of glass. As a result, block foam glass is obtained with increased bulk density. With an increase in the specific surface area of more than 150 m ² / g, the foaming efficiency decreases due to burning of the carbon ingredient by the involved air and surface-adsorbed gases in the period before the glass is sintered.

 Melt structuring is achieved by introducing 0.6-12.0 wt.% Active silica in the form of diatomite, aerosil, silica gel. At small values up to 0.6 wt.% The concentration of active silica, it is not possible to stabilize the structure of block foam glass due to the large contrast of viscosity over the cross section of the temperature field of the resulting block foam glass. At a higher concentration of more than 12.0 wt. % active silica there is a significant increase in the bulk density of glass due to the reduction of swelling. Active silica stabilizes the structure, makes it more uniform and eliminates or reduces volumetric water saturation.

 Alloying the melt with boron oxides in an amount of 0.2-5.0 wt.% Reduces the thermomechanical stresses in the molded product from block foam glass, simplifies the annealing of thermal stresses, and significantly increases the mechanical strength of products from block foam glass. When boron oxides are introduced into the melt in an amount exceeding 5 wt.%, The chemical resistance of block foam glass may deteriorate and operational characteristics may decrease. The introduction into the melt of boron oxide in amounts below 0.2 wt.% Does not have a significant effect on the formed product from foam glass and, therefore, is impractical.

Granulation of the mass into spherical particles with a size of 30-2000 μm helps to increase the bulk density of the material in the form to 0.96-1.35 g / cm ³ , reduces the volume of entrained and adsorbed air prematurely burning the active carbon component, improves and makes it more uniform and homogeneous structure of block foam glass. A decrease in the mass density in the form of less than 0.96 g / cm ³ does not allow to obtain a uniform structure of block foam glass; an increase in the mass density in the form of more than 1.35 g / cm ³ reduces foaming and enhances the heterogeneity of the structure.

The placement of the mold in a furnace with a temperature of 450-700 ^o C is necessary for the formation on the surface of a dense crust and the evacuation of the mass volume from the external environment and reduce the thickness of the surface decarburized crust. At temperatures below 450 ^o C, the evacuation of the volume is delayed, as a result, foaming decreases sharply or does not occur at all. At temperatures above 700 ^o C, thermal shock occurs with violation of the continuity of the structure and the division of the block into fragments.

 The heating rate to the foaming temperature of the forming block of foam glass is selected based on the preservation of the continuity of the material, which significantly depends on the volume of the block.

The lowest foaming temperature of 790 ^o C is limited by the properties of the system to form block glass with a bulk density of 0.15-0.45 g / cm ³ , the highest foaming temperature of 860 ^o C is limited by the violation of the uniformity of the porous structure of the glass and the increase in volumetric water saturation due to the continuity of the walls then, combining them into large pores, the formation of cavities and a decrease in the economic feasibility of the process and the cost of commodity production.

Structural and mechanical properties of the foamed melt are fixed by quenching at a temperature of 540-620 ^o With a speed of 80-300 ^o C / min The lower temperature value of 540 ^o C is determined by the difference that the block can withstand in a thermoplastic state without the development of stresses causing cracking or fracture in it; the upper value of 620 ^o C is limited by the need to inhibit redox reactions and fix the volume of the formed foam glass block.

When doping the melt with boron oxide, annealing to relieve thermal stresses, maintain continuity, and increase the mechanical strength of the material is not difficult. The lowest temperature value up to 420 ^o C allows you to remove thermal stresses, when the temperature is higher than 520 ^o C, subsidence of the volume of block foam glass, an increase in bulk density and significant deformation of the block are possible.

 The technical implementation of the method consists in the sequential implementation of technological influences with the declared parameters and their values, the effect of which on the properties of block foam glass is described above. The glass to be recycled is dispersed in a grinding unit, which can be a vibratory or ball mill. Hydroxylation of recyclable glass is carried out during grinding in the presence of a water additive or in a special unit by treatment with water vapor. Active silica, water glass, active carbon black, sulfate, boric acid are mixed. The activated recyclable glassy alkaline aluminosilicate is combined with the functional mixture in compliance with the claimed concentration of ingredients, which is designed to provide controlled process control for the formation of effective block foam glass. The prepared mixture is subjected to granulation. Next, the metal form is filled with granular material and densified to the claimed apparent density. Forms with foamable material are sent to the furnace for sintering, foaming, stabilization of the structure, annealing, which removes thermal stresses in the foam glass block under the established conditions and temperature values.

 EXAMPLE 1

The green glass bottle is thermally crushed to particles smaller than 250 microns. Crushed glass is dispersed in the presence of 0.8 wt. % water additives in the mill. The obtained hydroxylated glassy alkaline aluminosilicate has a BET specific surface area of 14,000 cm ² / g. A mixture of 7 wt.% Active silica in the form of, for example, diatomite, 0.2 wt.% Active carbon black, 0.5 mass parts of sodium sulfate, 1.5 wt. % boron oxide and subjected to mixing in a mill. Glassy hydroxylated alkaline aluminosilicate in the amount of 88 parts by weight is combined with 12 parts by weight of the mixture and mixed, achieving the greatest possible uniformity. The prepared composite mixture is granulated in the presence of water glass, introduced in an amount of 2.5 wt.% Per dry substance, into spherical particles with a size of 0.5-2.0 mm. If liquid glass was introduced with dry powder, the composite mixture is wetted to improve the collection of material into granules.

The granules are loaded into a metal mold and compacted to an apparent density of 1.00 g / cm ³ .

The mold with the material is initially fed into the sintering zone of the furnace with a temperature of 600 ± 20 ^° C, then it is successively transferred to the foaming zone of the furnace with a temperature of 800 ± 10 ^° C and into the quenching zone at a temperature of 560 ± 20 ^° C at a speed of 250 ^° C / min.

The formed block of foam glass is subjected to annealing at a temperature of 460 ± 10 ^o C.

Properties of block foam glass:
- apparent density of 0.186 g / cm ³ ;
- volumetric water absorption of 4.8%;
- thermal conductivity λ (at 20 ^o С) 0,062 W / (m • K);
- compressive strength 10 kg / cm ² .

 EXAMPLE 2

Brown bottle glass is thermally crushed to particles less than 250 microns. Crushed glass is dispersed in a mill in the presence of 0.5 wt. % water supplement. The obtained hydroxylated glassy aluminosilicate has a BET specific surface area of 15,000 cm ² / g. A mixture is made up of 4% by weight of active silica, for example, in the form of diatomite, 0.3% by weight of active carbon black, 0.5% by weight of sodium sulfate, 0.5% by weight of boron and mixed in a mill to achieve homogeneity of distribution of ingredients. Glassy hydroxylated alkaline aluminosilicate in an amount of 95 parts by weight is combined with 5 parts by weight of the mixture and mixed until uniform
The prepared composite mixture is granulated in the presence of liquid glass, introduced in an amount of 1.5 wt.% Per dry substance, into spherical particles with a size of 0.5-2.0 mm. If liquid glass is introduced with dry powder, the composite mixture is wetted to improve granulation of the material.

The granules are poured into a metal mold and compacted to an apparent density of 1.3 g / cm ³ .

The mold with the material is initially fed into the sintering zone of the furnace with a temperature of 660 ± 20 ^° C, followed by transfer to the foaming zone of the furnace with a temperature of 800 ± 10 ^° C and then to the quenching zone at a temperature of 550 ± 20 ^° C at a speed of 300 ^° C / min.

The formed block of foam glass is subjected to annealing at a temperature of 450 ± 10 ^o C.

Properties of block foam glass:
- apparent density of 0.350 g / cm ³ ;
- volumetric water absorption of 2.7%;
- thermal conductivity (at 20 ^o C) 0,080 W / (m • K);
- compressive strength of 7 kg / cm ² .

 EXAMPLE 3

Tare glass of light (transparent) color is crushed and mechanically ground to a particle size smaller than 250 microns and magnetized from metallic iron. Ground glass is dispersed in the presence of 0.5 wt. % water additives in the mill. The resulting hydroxylated alkaline aluminosilicate has a BET specific surface area of 18,000 cm ² / g.

 A mixture is made up of 11 wt.% Active silica, for example, in the form of diatomite, 0.5 wt.% Active carbon black, 1.0 wt.% Sodium sulfate, 5.0 wt.% Boron oxide and mixed in a mill.

 Glassy hydroxylated alkaline aluminosilicate in an amount of 85 parts by weight is combined with 15 parts by weight of the mixture and mixed to achieve the greatest possible uniformity of the composite mixture.

 The prepared composite mixture is granulated in the presence of liquid glass, introduced in an amount of 5 wt.% Per dry substance, into spherical particles with a size of 0.5-2.0 mm. If liquid glass is introduced with dry powder, the composite mixture is moistened to improve the collection of material into granules.

Pellets fill the metal form and fill up the densify to an apparent density of 1.25 g / cm ³ .

The mold with the material initially enters the sintering zone of the furnace, where the temperature is 700 ± 20 ^o C, and after exposure to equalize the temperature over the cross section of the block, it moves to the foaming zone of the furnace with a temperature of 860 ± 10 ^o C, thermostats, then enters the quenching zone at a temperature of 510 ± 20 ^o With a speed of 250 ^o C / min.

The formed block of foam glass is subjected to annealing from 500 ± 10 ^o C.

Properties of block foam glass:
- apparent density of 0.270 g / cm ³ ;
- volumetric water absorption of 8.7%;
- thermal conductivity (at 20 ^o C) 0,072 W / (m • K);
- compressive strength of 5 kg / cm ² .

 The table shows additional examples similar to examples 1-3, illustrating the great potential of the proposed method for producing functional block foam glass based on individual and mixed compositions of recycled glass for domestic, medical and other uses.

 Thus, the proposed method for producing block foam glass allows you to utilize different types of glasses and get block foam glass with improved performance.

Claims (1)

A method of producing block foam glass, comprising dispersing a recycled cullet, adding a foaming mixture containing active silica, a carbon component and metal sulfate, sintering, foaming at a temperature of 790-860 ^o C, hardening and annealing, characterized in that the glass cullet is dispersed to a specific surface of 6000- 20,000 cm ² / g, and then hydroxylated to saturation with moisture 0.4-1.6 wt.%, and 75-98 wt.% hydroxylated cullet added 2-25 wt.% expandable mixture, comprising as active component a carbonaceous w carbon black having a specific surface area of 75-150 m ² / g, as a metal sulphate - sodium sulphate, and further sodium liquid glass and boron oxide in the following ratio of ingredients, wt.%:
Liquid sodium glass - 0.5 - 5.0
Active soot with a specific surface of 75-150 m ² / g - 0.2 - 1.5
Sodium Sulfate - 0.5 - 1.5
Active silica - 0.6 - 12.0
Boron oxide - 0.2 - 5.0
mix, granulate into particles with a diameter of 30-2000 microns, pour into a mold and condense to an apparent density of 0.96 - 1.35 g / cm ³ , sinter at a temperature of 450-700 ^o C, foam, subjected to hardening at a temperature of 540-620 ^o C at a rate of 80-300 ^o C / min and block foam glass is annealed at a temperature of 420-520 ^o C.

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