RU2697981C1 - Method of producing foamed glass - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to method of producing foamed glass. Method of producing foamed glass includes preliminary grinding of cullet, its wet grinding to obtain a glass binder suspension, molding, foaming, holding at foaming temperature and annealing. Cullet grinding is performed in one step to particle size 0.1…5 mm, wet grinding of cullet is carried out in water in ball mill at moisture content of 24…32 % for 2…4.5 hours, note here that additive of cement dust of electrostatic precipitators is introduced into mill in amount of 1...7 wt% and further grinding of glass binder suspension is carried out during 0.5 hour. Hardening is carried out in tight conditions at constant moisture content during 62…158 h, foaming is carried out at temperature 745...815 °C at furnace heating rate 200…250 deg/h with holding at this temperature for 0.25…1 hour.

EFFECT: reduced temperature interval of foaming, reduced time of curing, reduced resource consumption and power consumption.

1 cl, 1 tbl, 1 ex

Description

The invention relates to the field of industrial processing of waste from glass, and can be used to produce foam glass. The foam glass obtained by the proposed method can be widely used as an effective functional heat and sound insulation material.

A known method of producing foam glass, comprising preparing a suspension by wet grinding of the starting components, ripening the suspension by holding it in air, molding and heat treatment of the paste to produce foam glass. The temperature regime of processing the paste (suspension): sintering at 600 ... 780 ° C for 30 minutes, foaming at 870 ° C for 30 minutes, quenching to 500 ° C. Annealing is carried out from 520 ° C for 8.5 hours (ed. St. USSR No. 1744071, С03С 11/00, publ. 30.06.92).

The disadvantage of this method is the high energy consumption due to the long grinding time, and also that it can be realized only by using glass of the same chemical composition, which provides a paste (suspension) with a certain content of polysilicic acid gel in it. This is technologically difficult, since it requires the use of specially welded glass of a given chemical composition or cullet formed during the industrial processing of glass, but with a known and stable chemical composition.

The process of producing foam glass is also described in the patent (RF Patent No. 2176219, С03С 11/00, С03В 19/08, publ. 11/27/2001). It provides: preparing a suspension by wet grinding of the starting components (cullet of color picture tubes) for 17 ... 18 hours; then, the formed suspension is stabilized by introducing into the composition of the flocculant (polyacrylamide in an amount of 0.05 to 1% of the total mass of glass); the suspension is held in air for 1.5 ... 2 hours; bringing the finished suspension to a cured state; molding followed by heat treatment at 680 ... 720 ° C for 10 ... 20 min, and then at 740 ... 850 ° C with holding for 15 ... 20 min.

The disadvantages of this method are the high energy costs associated with a long grinding time and the use of a two-stage and long heat treatment mode, as well as the use of an expensive additive (flocculant).

Also known is the “Method for producing foam glass (options)” (patent WO 2003055815 A1, application No. PCT / RU 2001/000570, published July 10, 2003), in which an aqueous paste (suspension) is prepared from a mixture of ground: glass, silicate lumps or sodium silicate, blowing agent, acid. The resulting paste (suspension) is molded into blocks, dried in air for 1 ... 6 days at room temperature and heated to a foaming temperature of 780 ... 850 ° C with holding for 180 ... 300 minutes.

The disadvantages of this method are the high energy consumption for production due to the high foaming temperature, followed by a long exposure at this temperature, as well as the use of expensive additives, such as silicate block, sodium silicate, acid (acetic, nitric, sulfuric), which lead to higher prices for finished products.

Closest to the proposed invention, the technical solution adopted for the prototype is the study described in the thesis for the degree of candidate of technical sciences “Synthesis of a glass binder suspension and porous material based on it” (MV Month. Synthesis of a glass binder suspension and porous material on its basis: the dissertation ... candidate of technical sciences: 05.17.11 / Mesyats Mikhail Vladimirovich; [Place of defense: Belgorod State Technical University named after VG Shukhov] - Belgorod, 2016. - 145 p.) .

In this work, the production of foam glass was carried out by heat treatment of a cured glass binder suspension (SHS), which was obtained from the battle of sheet glass. The preparation of a glass binder suspension was carried out by grinding glass breakage of sheet glass in a jaw crusher to a particle size of 1 ... 30 mm and in a laboratory sample grinder to a particle size of 0.1 mm or a hammer mill to obtain a fraction of 0.2 mm or less.

At the next stage, the cullet was wet milled for 6.5 hours, and the method of step-by-step loading (loading is carried out every 0.5 hours after 3 hours of grinding) of the material in the mill was used. At the end of the grinding operation, the suspension was stabilized in a drum mixer to a gel state. Subsequently, stabilized SHS for producing blocks was developed by casting into molds. The drying of the blocks was carried out in natural conditions in air.

In the next step, the hardened blocks were foamed at a temperature of 810 ... 825 ° C with an exposure time of 0.5 ... 1 h.

The disadvantages of this method are:

- use for production of SHS technological wastes (sheet glass breakdown) generated as a result of industrial processing of sheet glass, the amount of which is limited;

- the use of two-stage grinding of sheet glass battle, which leads to significant energy costs for the preliminary preparation of glass battle;

- the use of the method of step-by-step loading of glass battle into the mill when obtaining SHS, followed by its stabilization, which leads to significant energy costs for the process and the high cost of foam glass.

The present invention is directed to the development of a technologically effective method for producing foam glass based on waste from the production of sodium-calcium silicate glass (ecological non-returnable cullet of container glass and cement dust of electrostatic precipitators), reduction of energy costs for its production due to:

- obtaining SHS one-stage grinding;

- reducing the temperature range of foaming of SHS;

- reduce the exposure time at the maximum foaming temperature;

- receiving foam glass with less resource and energy costs.

This is achieved by the fact that the method for producing foam glass includes preliminary grinding of cullet, its wet grinding to obtain a glass binder suspension, molding, curing, foaming, aging at a foaming temperature and annealing.

In this case, cullet grinding is carried out in one step to a particle size of 0.1 ... 5 mm, cullet is wet milled in water in a ball mill at a moisture content of 24 ... 32% for 2 ... 4.5 hours, then an addition of cement dust of electrostatic precipitators is introduced into the mill in the amount of 1 ... 7 wt. % and carry out further grinding of the glass binder suspension for 0.5 h, curing is carried out in sealed conditions with constant humidity for 62 ... 158 h, foaming is carried out at a temperature of 745 ... 815 ° C with a furnace heating rate of 200 ... 250 deg / h, with exposure at this temperature for 0.25 ... 1 h

Getting SHS is carried out from the battle of container glass grades BS, PST, ZS, KS (GOST 52233-2004. Glass containers. Cullet. General specifications). The compositions of glasses of these grades differ from the composition of sheet glass in the content of basic oxides. The chemical composition of container glasses of various grades also slightly differs from each other, but liquid-phase grinding with the developed optimal parameters provides a high degree of homogeneity of the chemical composition of SHS, which favorably affects the stability of the foaming process.

Liquid-phase grinding of cullet of container glasses is carried out in one stage, which provides an increase in the content of fine (colloidal) particles in the resulting SHS structure; grinding time to obtain SHS with the required structure is 2 ... 5 hours.

0.5 hours before the end of the grinding, cement dust from electrostatic precipitators in the amount of 1 ... 7 wt. %

Drying for the curing of SHS is carried out in sealed conditions, providing effective "accumulation" of moisture in the SHS volume in the form of physically and chemically bound water, and the addition of CPE introduced into SHS favorably contributes to this process. Complete curing of SHS during the implementation of the described processes proceeds within 62 ... 158 hours

Heat treatment, accompanied by “foaming” of the SHS, is carried out at a temperature of 745 ... 815 ° C with a heating rate of the furnace 200 ... 250 ° C / h, exposure at this temperature is carried out for 0.25 ... 1 hour

The preliminary grinding and liquid-phase grinding of the battle of glass containers under the developed conditions are accompanied by the following physicochemical processes: a decrease in size and an increase in the specific surface of glass particles, which increases the rate of chemical reactions at the glass-water interface with the formation of a loose film of silicic acid gel and insoluble silicates of alkali and alkaline earth metals. Due to the high energy saturation of the grinding process, a film of silicic acid gel is formed on the surface of the glass grains, which rapidly breaks down and dissolves under the influence of alkali formed. This process makes it possible to constantly “update” the surface of the glass grains, which remain reactive throughout the entire time of obtaining SHS.

After the grinding time, the SHS obtained is a high-density alkaline silicate solution, which is characterized by thixotropic dilatant rheological properties. The curing of SHS obtained by the specified method is caused by polymerization reactions by the polycondensation of silicic acid in the presence of alkalis.

The introduction of a CPE additive, due to the content of sodium and potassium sulfate in it, contributes to the additional “binding” of water with the formation of sodium sulfate decahydrate during curing of the suspension, and during heat treatment it favorably affects the foaming process due to the additional potential of gases such as SO ₂ and O ₂ .

Only if all the conditions and parameters of the developed method are met, it is possible to obtain such a structure cured in sealed SHS conditions that in a given temperature range of foaming will provide a given porosity of foam glass, the regulation of which is ensured by variations in the values of the foaming (processing) temperature and the exposure time at this temperature.

Component Feature

1. Cullet of sodium-calcium-silicate glass (battle of container glass), according to GOST 52233-2004 Glass containers. Cullet. General specifications).

2. Technical water according to GOST 23732-2011 "Water for concrete and mortar."

3. Cement dust from electrostatic precipitators, wt. %: 8.4 ... 16.31 SiO ₂ ; 2.75 ... 5.7 Al ₂ O ₃ ; 46.72 ... 59.8 CaO; 0.73 ... 1.73 MgO; 7.12 ... 27.5 K ₂ O; 1.28 ... 4.03 Na ₂ O; 5.07 ... 7.7 SO ₃ .

A method for producing cullet-based foam glass includes the following steps:

- grinding of cullet to a fraction of 0.1 ... 5 mm;

- wet grinding in a ball mill with a moisture content of 24 ... 30%;

- the introduction of CPE additives;

- SHS molding;

- SHS curing in sealed conditions for 62 ... 158 hours;

- heating to a temperature of 745 to 815 ° C at a speed of 200 ... 250 deg / h;

- exposure at this temperature for 0.25 ... 1 h;

- annealing the material in the furnace.

Comparative characteristics of the developed method for producing foam glass and prototype are presented in table. one.

An example embodiment of the invention.

Cullet in the amount of 14 kg is crushed in a jaw crusher to obtain particles with a size of 0.1 ... 5 mm. Make a wet grinding in a ball mill with the addition of water in the amount of 6 kg and get a glass binder suspension (SHS). 0.5 h before the end of the SHS production process, a CPE additive in the amount of 420 g is introduced into the mill. Then, the suspension is poured into molds of 200 * 100 * 20 mm in size, kept in sealed conditions at constant humidity for 120 hours until the suspension is completely cured. In this case, the curing process occurs in sealed conditions, ensuring the flow of polycondensation of silicic acid in the presence of alkali without drying. This process contributes to the accumulation of moisture in the structure of the SHS in the form of physically and chemically bound water.

Foaming is carried out after curing of the SHS at a temperature of 780 ° C for 0.5 hours with a furnace heating rate of 250 ° C / h.

The resulting samples are tested according to standard methods. The resulting foam glass has the following properties:

1. Density - 155 ... 170 kg / m ³ ;

2. Compression strength - 1 ... 2.5 MPa;

3. Water absorption - 1.2 ... 2.3%;

4. Thermal conductivity - 0.075 ... 0.097 W / m⋅K °.

The results of the studies showed that the foam glass obtained by the developed method meets the requirements of GOST 33949-2016 and TU 5914-001-73893595-2005, therefore, it can be used as a building block heat and sound insulation material.

Claims (1)

A method of producing foam glass, including preliminary grinding of cullet, its wet grinding to obtain a glass binder suspension, molding, foaming, aging at a foaming temperature and annealing, characterized in that the grinding of cullet is carried out in one step to a particle size of 0.1 ... 5 mm, wet Cullet grinding is carried out in water in a ball mill at a moisture content of 24 ... 32% for 2 ... 4.5 hours, an cement dust additive of electrostatic precipitators is introduced into the mill in an amount of 1 ... 7 wt. % and carry out further grinding of the glass binder suspension for 0.5 h, curing is carried out in airtight conditions with constant humidity for 62 ... 158 h, foaming is carried out at a temperature of 745 ... 815 ° C with a furnace heating rate of 200 ... 250 deg / h, with exposure at this temperature for 0.25 ... 1 h