RU2164898C2 - Composition for preparing foam glass - Google Patents

Abstract

FIELD: manufacture of heat-insulating material, more particularly foam glass as heat insulating material of production equipment, pipelines and refrigerating plants. SUBSTANCE: composition comprises evulcanic glass, sodium hydroxide, crushed container glass and nepthelite syenite, ratios of components being as follows wt.%: nepheline sienite, 5-15; crushed container glass, 45-55; sodium hydroxide, 7-9; and vulcanic glass, the balance. EFFECT: improved properties of the composition. 5 tbl

Description

 The invention relates to the production of heat-insulating material, in particular foam glass, which can be used in construction, for thermal insulation of production equipment, pipelines, for insulation of refrigeration units.

Known mixture for the manufacture of foam glass, having in its composition, wt.%:
Sodium Oxide Hydrate - 6 - 8.5
Perlite (volcanic glass) - 91.5 - 94.0
(see A.S. N 292909, C 03 C 11/00, BI N 5, 1971).

However, the known composition has a relatively high foaming temperature of 850 - 950 ^o C, a long firing period (15 - 60 min) and low heat resistance of 300 ^o C. According to the known composition, the density of the foam glass reaches 0.9 g / cm ³ , which is undesirable for a heat-insulating material.

A known mixture for the production of foam glass, providing for the melting of glass with the addition of Al ₂ O ₃ , the carriers of which is nepheline concentrate, grinding glass in a ball mill, mixing with a blowing agent and further heat treatment in a tunnel oven using the powder method. The composition of the charge in this case, wt. %:
SiO ₂ - 68 - 71
CaO + MgO - 5 - 9
R ₂ O - 14.5 - 15.0
Fe ₂ O ₃ - up to 5
SO ₃ - 0.2 - 0.4
and besides,
Al ₂ O ₃ - 3 - 10
(see A.S. N 393227, C 03 C 11/00, BI N 33, 1973).

However, the glass in the known method is boiled in a bath furnace at a maximum temperature of 1450 ^o C, then crushed in a ball mill, mixed with a blowing agent and get foam glass in a tunnel oven at temperatures above 800 ^o C.

Similar in technical essence and in the chemical composition of the charge used is a composition for producing foam glass by glass melting in the following ratio of components, wt.%: SiO ₂ 72; Al ₂ O ₃ + Fe ₂ O ₃ to 1.2; CaO 6; MgO 0.4; Na ₂ O 16.5; SO ₃ 0.3 (see A.S. N 806627, C 03 C 11/00, BI N 7, 1981).

 However, in the known preparation of the composition, as in the previous one, high-temperature glass melting is present, followed by foaming it by powder technology. The nepheline concentrate from 5 to 15 wt.% Is introduced, unlike the previous preparation, not at the stage of cooking the main glass, but at the stage of grinding before foaming. The compositions are characterized by the energy intensity of the process and the complexity of the technology.

The closest in technical essence and the achieved result to the proposed invention is a mixture for the production of foam glass, including dry grinding of rocks (volcanic glass - perlite, sedimentary siliceous rock and a blowing agent) to obtain a powder with a specific surface of 3000 - 5000 cm ² / g in the following ratio of components , wt.%:
sodium oxide hydrate - 6 - 15
blowing agent - 0.02 - 1.5
sedimentary siliceous rock - 15 - 70
volcanic glass - the rest
To increase temperature resistance, sedimentary siliceous rock is additionally introduced into the mixture containing volcanic glass (perlite), sodium oxide hydrate, and a gasifier. Diatomite, tripoli, and flask were used as sedimentary siliceous rock (A.S. 1073199, C 03 C 11/00, BI N 6, 1984).

 The reasons that impede the use of the known substance include the fact that in places where sedimentary siliceous rocks are not common, it becomes problematic to implement the described foamglass technology using these rocks. In our opinion, the increased content of sodium hydroxide (15%) contributes to the increase in the cost of foam glass. Separate compositions of the known substance (N 2, N 4) lead to increased water absorption (53.1 and 75.1 vol.%), Which is undesirable if they are used for the production of heat-insulating foam glass.

 The problem to be solved in the present invention is to create a heat-insulating material based on cullet of container glass and alkaline aluminosilicate rocks of Transbaikalia.

The technical result of the invention is:
- improving the quality of the foam glass (structure and density) and lowering the foaming temperature of the resulting material;
- reducing the environmental burden due to the disposal of cullet casing glass;
- reducing the cost of foam glass due to the partial replacement of conditioned perlite with cheaper cullet of container glass and nepheline concentrate - nepheline syenite;
- simplification of foam glass production technology.

The specified technical result in the implementation of the invention is achieved in that the composition for producing foam glass, consisting of volcanic glass, sodium hydroxide, according to the invention contains glass cullet and nepheline syenite in the following ratio of components. wt.%:
nepheline syenite - 5 - 15
cullet of container glass - 45 - 55
sodium hydroxide - 7 - 9
volcanic glass (perlite) - the rest
Comparison of the invention with other known technical solutions allowed to establish the following.

As in the known technical solution, the proposed composition eliminates the energy-intensive stage of glass melting and foam glass directly from the melt, but the proposed composition is characterized by a lower content of the introduced sodium hydroxide, which helps to reduce the cost of foam glass. In our opinion, partial replacement of perlite with cullet with a high content of R ₂ O (up to 16%) will save natural volcanic glass (perlite), lower the foaming temperature of foam glass to 750 - 800 ^o C and the amount of additional alkali (sodium hydroxide) to be added 7 - 9%, whereas in the known compositions, foam glass is obtained at temperatures of the order of 850 - 950 ^o C with an alkali consumption of up to 15%.

 The multicomponent composition of the proposed mixture increases the viscosity of the aluminosilicate melt in the temperature range of foaming, which positively affects the inhibition of crystal growth and a decrease in the rate of formation of crystallization centers. As a result, the rate of water absorption in the claimed foam glass is lower than in the prototype, and is in the range of 0.5 - 4%.

 To carry out leaching processes in order to maximize the alkali yield from alkali-containing rocks and materials, according to V.V. Boldyreva, expressed by him in his work ("Development of research in the field of mechanochemistry of inorganic substances in the USSR" (Novosibirsk: Nauka, Sib. Department, 1991, p. 20)), an increased activity of the substance is required not only on the surface, but also in volume . In this case, the substance must be crushed to the maximum size, and then proactivated. The achievement of increased activity in the volume of the substance in order to initiate leaching processes is the "know-how" of the present invention and is not described in the application materials.

 In the known technical solution for the production of foam glass (see AS No. 292909, C 03 C 11/00, BI N 5, 1971), a composition was used in the system "volcanic glass - sodium hydroxide", which leads to the consumption of conditioned perlite (volcanic glass), whose reserves have declined in recent years and, due to new realities, the main sources of perlite raw materials are abroad (Aragatskoye deposit, etc.). In this regard, the replacement of a part of perlite with cullet of container glass helps to expand the raw material base for the production of foam glass and reduce the environmental burden on the environment: due to incombustibility and biostability, glass waste irreversibly pollutes the landscape. On the other hand, the use of cullet casing glass is a source of saving alkali and electricity.

Known compositions that include only cullet and blowing agent (see F. Schill. Foam glass (production and use). - Moscow, Publishing House of Construction Literature, 1965, p. 53), lead to increased water absorption on average up to 70% of for the tendency of the glass to crystallize upon repeated heating. So, the foam glass produced by the Likhoborsky factory of heat-insulating products was not regulated by the water absorption index due to the instability of container glasses to crystallization in the temperature range up to 900 ^o C, which makes them suitable for the production of foam glass with a lower level of thermophysical and humidity properties.

 In the proposed composition, the problem of reducing the water absorption of foam glass is solved by selecting a multicomponent raw material charge. It is known that a decrease in the tendency to crystallization can be achieved by complicating the composition of the charge. The introduction of additional oxides increases the likelihood of simultaneous precipitation of two or more crystalline phases, which is accompanied by inhibition of crystal growth of each of the compounds and, accordingly, a decrease in the overall crystallization ability of glass (see Physical Chemistry of Silicates. Edited by A. A. Pashchenko. - M.: Higher School , 1986, p. 285).

 Introduction to the charge in the proposed composition of nepheline syenite contributes not only to the complexity of the composition, but also to increase the heat resistance of glass due to aluminum oxide.

In the known composition (see AS No. 393227, C 03 C 11/00, BI N 33, 1973), alumina is introduced by nepheline concentrate at the level of high-temperature (1450 ^o C) cooking of the main glass, as well as after high-temperature cooking glass at the grinding stage before foaming (see A.S. N 806627, C 03 C 11/00, BI N 7, 1981).

 In contrast to the known compositions with the introduction of nepheline concentrate in the proposed composition, nepheline syenite is introduced along with the other components and the foam glass is obtained directly from the melt, which helps to reduce energy consumption and simplify the technology for the production of foam glass.

 The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information and identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find an analogue characterized by features identical to all the essential features of the claimed composition for producing foam glass. The determination from the list of identified analogues of the prototype as the closest analogous set of essential features made it possible to identify a set of significant features relative to the technical result (improving the quality of the foam glass - structure and density; lowering the foaming temperature of the resulting material; lowering energy costs, cost; simplifying the technology) distinctive features the claimed invention set forth in the claims, namely the interaction of nepheline syenite, cullet glass, volcanic glass and sodium hydroxide.

 Therefore, the claimed invention meets the conditions of "novelty" and "inventive step".

 An intensifying factor when using a composition consisting of perlite, and, in addition, from cullet of container glass and nepheline syenite, is the high content of alkaline components in them, which are smooth and contribute to lowering the foaming temperature of the glass charge. In the claimed composition, the main glass-forming components are volcanic glass of the Mukhor-Talinsky deposit, nepheline syenite of the Mukhalsky deposit of the Republic of Buryatia and cullet of container glass, the chemical composition of which is given in table. 1.

 Volcanic glass (perlite) of the Mukhor-Talinsky deposit is represented by 90-95% glass, has a network of thin concentrated cracks, which are zones of glass devitrification.

 The Mukhal deposit of alkaline rocks is located in the Baikal region and is a source of raw materials for various industries. This alkaline rock is represented by the nepheline mineral (56%), secondary to nepheline (21.6%), including cancrinite (7%), analcime (2.2%), mica (3.3%); feldspars (3.1%): plagioclases (1.4%), potassium-sodium (1.7%); non-ferrous and ore minerals (18.1%), as well as accessory minerals (sphene - 0.3% and apatite - 0.9%) and consists of three main components - silica, alumina and alkali. For comparison, we give the chemical composition of the raw materials used in the known compositions (table. 2).

The cost of nepheline syenite used in the claimed composition is 3.29 rubles. per 1 ton in 1981 prices. Known compositions include an expensive component - nepheline concentrate, cost per 1 ton - 47.8 rubles. in prices of 1981. Moreover, in the work of B.K. Demidovich ("Production and use of foam glass. - Minsk, Science and Technology, 1972, p. 124) indicated that when cooking high-alumina glasses using nepheline concentrate, volcanic glasses, good penetration is achieved at a temperature maximum of 1450 - 1480 ^o C. So, nepheline for optimum cooking temperature when the content of Al ₂ o ₃ in the glass in the range of 5 - 7% was determined to be 1460 ^o C, and in the inventive composition with the same contents nepheline syenite foam glass is obtained directly from the melt at a temperature high lather Bani 750 - 800 ^o C.

To obtain the optimal composition of the foam glass and temperature treatment conditions were prepared compositions that differ from each other in content, wt. %: cullet of container glass 40.0; 45.0; 50.0; 55.0; 60.0; nepheline syenite 1.0; 5.0; 10.0; 15.0; 20.0; sodium hydroxide 7.75 - the average value for all formulations; as well as the content of volcanic glass - perlite, which constitutes an additional up to 100% part in each composition. Foam glass of the proposed composition was obtained at processing temperatures of the compositions of the charge of foam glass 700, 750, 775, 800, 850 ^o C.

 The resulting foam glass compositions had the following characteristics (see tables. 3 and 4, examples 1 to 5).

An analysis of the results obtained (Tables 3 and 4) allows us to conclude:
- with an increase in the consumption of cullet of container glass up to 60%, the structure of foam glass deteriorates: large-pore with a pore diameter of more than 2-4 mm; with a decrease in cullet cullet consumption up to 40%, foam glass density sharply increases (1023 kg / m ³ without mechanical activation, 841 kg / m ³ during mechanical activation);
- to the greatest extent the foaming temperature is reduced by the content of cullet of container glass in the amount of 45 - 55%, with the content of nepheline syenite in the amount of 5 - 15%;
- an increase in the content of nepheline syenite over 15% is impractical due to an increase in the density of foam glass, and a decrease in the content of nepheline syenite below 5% leads to a deterioration in the structure of foam glass;
- the temperature increase significantly reduces the density, but starting from the foaming temperature above 800 ^o C there is a pore enlargement due to the coalescence of bubbles in the melt. The optimal temperature range of foaming is defined 750 - 800 ^o C.

 In connection with the introduction of an aqueous solution of sodium hydroxide in the charge and the content in the charge of water-containing volcanic glass (perlite), it becomes possible to obtain foam glass without introducing additional reagents - blowing agents.

Therefore, optimal are the compositions of the foam glass containing, by weight. %: cullet of container glass 45 - 55%, nepheline syenite 5-15%, sodium hydroxide 7-9%, the rest is volcanic glass (perlite), providing improved quality of foam glass (structure and density), lowering the foaming temperature of the resulting material to 750 - 800 ^o C.

 The proposed foam glass is prepared as follows.

Dry milling of the rocks is carried out to obtain a powder with a specific surface of 3000 - 3500 cm ² / g in a ball mill. Then the charge is mechanically activated with the content of the components: cullet of container glass 45–55%; nepheline syenite 5-15%; volcanic glass - the rest. To the finished powder add 7 - 9% NaOH in the form of an aqueous solution, providing a moisture content of the mixture 18 - 21%. After mixing the mixture, the products are molded by pressing with a pressing force of 25-30 kg / m ³ . The pressed samples are fired in an oven at a temperature of 750 - 800 ^o C. Exposure of products at this temperature for 15 minutes The resulting products are annealed according to the mode: rapid cooling from the expansion temperature by 100 - 150 ^o C, holding at this temperature, followed by slow cooling to ambient temperature.

 Example 1

cullet of container glass - 45.00
nepheline syenite - 15.00
volcanic glass (perlite) - 32.25
sodium hydroxide - 7.75
The raw material mixture, consisting of cullet, nepheline syenite, volcanic glass, is ground in a ball mill to a specific surface (S _beats ) of a glass charge of up to 3500 cm ² / g and then subjected to mechanical activation in a rod vibration mill to S _beats = 4000 cm ² / g with the components in the mixture (wt.%).

Sodium hydroxide is added in an amount of 10% in excess of the mass of the mixture by dry components, which in terms of 100% is 7.75%. NaOH is introduced into the mixture in the form of an aqueous solution, providing a moisture content of the mixture of 18-21%. The mixture is thoroughly mixed and molded by compression molding. The pressed samples are fired at a temperature of 800 ^o C in a muffle furnace according to the regime: 1.5 hours - temperature increase, 15 minutes - firing (foaming), 5 minutes a temperature decrease of 100 - 150 ^o C in order to fix the foam, and then cooling together with oven to room temperature.

The density of the foam glass during mechanical activation is 302 kg / m ³ , the structure of the foam glass is uniformly porous, the pore diameter is 0.5 - 1.5 mm.

 Example 2

It is carried out analogously to example 1 in the following ratio of the component, wt. %:
cullet of container glass - 50.00
nepheline syenite - 10.00
volcanic glass (perlite) - 32.25
sodium hydroxide - 7.75
In this case, the pressed samples are fired at a temperature of 775 ^o C. The density of the foam glass during mechanical activation is 321 kg / m ³ , the structure of the foam glass is uniformly porous, pore diameter 0.5 - 1.5 mm.

 Example 3

It is carried out analogously to example 1 in the following ratio of components, wt. %:
cullet of container glass - 55.00
nepheline syenite - 5.00
volcanic glass (perlite) - 32.25
sodium hydroxide - 7.75
In this case, the pressed samples are fired at a temperature of 750 ^o C. The density of the foam glass during mechanical activation is 240 kg / m ³ , the structure of the foam glass is uniformly porous, pore diameter 0.5 - 1.5 mm.

 In the table. 5 shows comparative data on the physico-mechanical properties of the foam glass obtained according to the invention in comparison with the prototype (A.S. N 1073199, C 03 C 11/00, BI N 6, 1984).

Thus, the proposed composition for producing foam glass has the following advantages compared to the prototype:
- a heat-insulating material was obtained - foam glass based on alkaline aluminosilicate rocks of Transbaikalia and cullet of container glass with improved qualities (in structure and density);
- lowering the temperature of firing (foaming) of the obtained material to 750 - 800 ^o C due to the introduction of alkali-containing raw materials and materials (nepheline syenite and cullet) into the foam glass composition;
- the effect of decreasing the density of the foam glass in the proposed material is higher at lower energy and material costs;
- reduction of environmental pressure on the environment due to the disposal of cullet container glass;
- simplification of foam glass production technology;
- reduction in the cost of raw materials due to the replacement of part of conditioned perlite (volcanic glass) with glass cullet from container glass and nepheline concentrate with nepheline syenite; by reducing the amount of sodium hydroxide introduced up to 8% (in the prototype up to 15%) and due to the one-step process of heat treatment.

 The proposed composition of the charge was developed at NILSTROM VSSTU in conjunction with the laboratory of chemistry and technology of mineral raw materials of the Baikal Institute of Nature Management SB RAS and can be used in construction, in the power system as a heat-insulating material.

 Summarizing the results, we can conclude that foam glass based on alkaline aluminosilicates, cullet casing glass is a durable building heat-insulating material, which is advisable to use in the form of plates, blocks, shells for thermal insulation of building structures, thermal installations, as well as for self-supporting fencing elements. Therefore, the claimed invention meets the criterion of "industrial applicability".

Claims (1)

The composition for the production of foam glass, including volcanic glass, sodium hydroxide, characterized in that it further comprises cullet glass containers, nepheline syenite in the following ratio, wt.%:
Nepheline syenite - 5 - 15
Glass cullet - 45 - 55
Sodium Oxide Hydrate - 7 - 9
Volcanic Glass - Else

Images