RU2606539C1 - Charge composition and method of producing foamed heat-insulating material - Google Patents

Abstract

FIELD: heat insulation.

SUBSTANCE: invention relates to heat insulating materials. Charge components are mixed in following ratio, wt%: amorphous silicic rock 48–55; dry sodium hydroxide 15–18; aluminosilicate component 3–5, water 24–35. Preparation of charge comprises first synthesizing primary sodium hydrosilicate with silica modulus of 2.1–2.2 when mixing dry sodium hydroxide with 54.5 % of total amount of amorphous silicic rock and hot water in specified quantity. Obtained sodium hydrosilicate is mixed with remaining amorphous silicic rock, followed by granulation of mixture and powdering granules of aluminosilicate component. Granules are loaded into a mould with a closed volume and foamed at a temperature of 760–780 °C for 20–40 minutes.

EFFECT: technical result of invention is reduction of moisture content and simple composition of charge.

2 cl

Description

The invention relates to the production of heat-insulating materials with a rigid structure, having low values of density and thermal conductivity.

Of the currently known heat-insulating materials with a rigid structure and high construction and technical properties, foam glass is.

The known composition of the charge and the method of producing foam glass, including the melting of glass and its grinding in a ball mill, mixing with a blowing agent and heat treatment in a foaming furnace (AS No. 393227, C03C, 11/00, BI No. 33, 1973).

The disadvantage of this composition and method is the need for glass melting at a temperature of 1450 ° C, fine grinding of the mixture and its foaming at a temperature above 800 ° C. In a number of known compositions of the blends it is proposed to exclude glass melting, as a very energy-intensive technological stage, and to use cullet as part of the blends.

A known method and composition of the mixture for producing foam glass containing (wt.%) Nepheline syenite 5-15, cullet glass container 45-55, sodium hydroxide 7-9, perlite - the rest (Pat. RF No. 2164698, C03C 11/00, publ. February 10, 2001). This composition allows you to exclude from the method the energy-intensive stage of glass melting and get foam glass from the mixture when it is heated to 750-800 ° C.

The main disadvantage of this composition and method is the need for additional energy-consuming mechanochemical activation of the charge, which allows to obtain foam glass with a density of 240-841 kg / m ³ . If the charge is not activated, then foam glass with a density of 411-1023 kg / m ³ can be obtained from it, which will belong to the group of structural heat-insulating materials.

A known composition and method of producing foam glass (AS No. 1073199, C03C, BI No. 6, 1984), in which the mixture does not contain any specially welded glass or cullet, and the task of the invention is solved by using a mixture containing (wt.% ) sedimentary siliceous rock 15-70, sodium hydroxide 6-15, blowing agent 0.02-1.5, perlite rock - the rest.

The main disadvantage of this method is the need for fine grinding of hard-to-grind pearlite rock (volcanic glass) in a medium of soft siliceous rock (diatomite, tripoli, flask), which reduces the grinding efficiency of pearlite rock, increases its duration and energy consumption for grinding the mixture. The disadvantage of the composition of the charge is also the high temperature of its foaming (800-850 ° C) and the high density of the resulting foam glass (up to 400 kg / m ³ ).

The closest in technical essence and the achieved result is the composition of the charge and the method of producing a heat-insulating material (analog foam glass) (RU No. 2478586, С03C 11/00, С03В 19/08, published on 04/20/2013, Bull. No. 10), in which charge is used in the following components (wt.%): expanded perlite - 20, amorphous siliceous rock - 28, sodium hydroxide - 12, water - 40.

The main disadvantage of the composition of this mixture is the low content of amorphous siliceous rock, as well as a significant amount of water, the removal of which requires a large amount of heat.

The main disadvantage of this method is the use of an aqueous solution of sodium hydroxide with a low (23.5% wt.) Concentration, which is formed by combining amorphous siliceous rock, water and sodium hydroxide. In a solution with such a concentration of sodium hydroxide, complete dissolution of the siliceous rock in alkali does not occur and part of the silica is not part of the sodium hydrosilicate formed during this interaction. We found (RU No. 2132817, СВВ 33/32, published July 10, 1999) that the most complete dissolution of silica occurs in an aqueous solution of sodium hydroxide with a concentration of 34-36% (wt).

The task of the invention is the elimination of these disadvantages. The technical result of the patented solution is to simplify the production process of heat-insulating material, reduce the time to obtain heat-insulating material, improve thermophysical and porous properties, as well as the ability to obtain products of various desired shapes (in the form of blocks, plates, segments, rings, etc.), which is achieved by using a charge in the form of granules with high porosity, while the use of traditional powder mixture allows the foaming process only in the form of blocks with a fuzzy shape and size.

This object is achieved by the fact that upon receipt of the heat-insulating material, a granular charge containing amorphous siliceous rock, dry sodium hydroxide, aluminosilicate component and water is used in the following components (wt.%):

Amorphous Siliceous Rock 48-55 Dry sodium hydroxide 15-18 Aluminosilicate component 3-5 Water 24-35

In particular, the mixture can be selected in the following composition, wt. %:

Amorphous siliceous rocks 55 Dry sodium hydroxide fifteen Aluminosilicate component 5 Water 25

As amorphous siliceous rock, diatomite, flask and tripoli in a finely dispersed state are used. The increased, compared with the analogue, the content of amorphous siliceous rock allows us to synthesize, as a result of hydrothermal reactions, a greater amount of sodium hydrosilicates. The increased content of sodium hydrosilicates, in turn, leads to an increase in the porosity of the composition and a decrease in bulk density of the products. The introduction of additional amounts of aluminum and iron oxides contained in amorphous siliceous rocks leads to an increase in the water resistance of the resulting foam glass.

As an aluminosilicate component, kaolinite and montmorillonite clays, granite processing waste or granitoid rocks, perlite rock, nepheline syenites, ashes and slags of TPPs in a finely dispersed (0-100 μm) state are used.

Sodium hydroxide can be used in the form of granules and flakes with a size of 0.5-5 mm.

In addition, the technical result is achieved by the fact that in the proposed method for the production of heat-insulating material, the mixture is used in granular form, obtained by performing technological operations of its preparation in the following sequence: synthesis of primary sodium hydrosilicate by mixing 54.5 (wt.%) Amorphous siliceous rock, dry sodium hydroxide and hot water for 5-10 minutes, mixing the resulting sodium hydrosilicate with the rest (45.5%) of amorphous siliceous rock, granulating according to irradiated plastic mass in a screw granulator, dusting the formed granules with an aluminosilicate component in a disk granulator and, if necessary, drying the granules. The granulated charge is loaded in the calculated amount into metal forms with a closed volume, in which foaming of the charge occurs when heated to a temperature of 750-780 ° C. The foaming time depends on the overall dimensions of the products obtained and is 20-40 minutes.

Due to the granular shape, the charge fills almost the entire volume of the form, which allows it to be initially evenly distributed in the form of any geometry, while the powder charge takes up a smaller volume. When porous, the granules increase in size and combine into a single array, forming a solid product, while the powder mixture occupies the lower compartments of the mold, it swells, but does not combine into a single product.

The granules of the charge can be spherical with a size of 2-10 mm or cylindrical with a diameter of 2-8 mm with a length of 5-15 mm.

Thus, the patentable composition of the charge and the sequence of operations of its preparation provide the synthesis of sodium hydrosilicates during mixing of siliceous rock, dry sodium hydroxide and water for 5-7 minutes, and the resulting mixture allows you to implement a method of obtaining a heat-insulating material at a foaming temperature in the range of 750-780 ° C.

Concrete example

1. As starting raw materials for the preparation of the charge, tripoli of the Zikeevskoye deposit (Kaluga region) with a SiO ₂ content of 84.5% and a particle size of less than 0.1 mm, granular and finely dispersed (less than 0.1 mm) sodium hydroxide aluminosilicate component was used - kaolin and bentonite clays, ash of Tomsk State District Power Station-2, finely ground granitoid rock, finely ground perlite ore. It should be noted that the type of aluminosilicate component used does not have a significant effect on the process of product porosity; all types of this component prevent the granules from sticking together during charge granulation and contribute to the formation of a honeycomb structure of products during porosity.

2. The preparation of the mixture began with the synthesis of primary sodium hydrosilicate with a module m = 2.17 by mixing dry sodium hydroxide and 54.5% of the total amount of amorphous siliceous rock and hot water with a temperature of 80-85 ° C. In this case, the concentration of an aqueous solution of sodium hydroxide was 37.5% (wt.), In which siliceous rock was intensively dissolved, and their mixture was heated to a temperature above 100 ° C (boiling). After stirring the hot mixture for 10 min, sodium hydrosilicate with a density of 1400 kg / m ^{3 was} obtained.

3. The remaining amount of 45.5% (wt.) Siliceous rock was introduced into the obtained sodium hydrosilicate, the mixture was thoroughly mixed until a plastic, solid mass was fed into the screw granulator equipped with a knife-grate pair, which allows thoroughly homogenizing the mixture, from which granules were formed with a diameter of 5-8 mm and a length of 10-20 mm.

4. At the exit from the granulator, the granules were dusted with a finely dispersed aluminosilicate component, then the granules, together with the dusting additive, were fed to a plate granulator for surface pelletizing, after which the granules were dried to a residual moisture content of 14-18%.

5. The granular charge was loaded into a metal mold with an internal volume of 0.5 dm ³ (10 × 10 × 5) cm, the mold was closed with a lid with clamps and placed in a muffle furnace previously heated to a temperature of 780 ° C and kept at this temperature for 20 min, after which the mold with the product was cooled together with the furnace for 5 hours. After disassembling the mold, an article was removed from it, from which the density, strength, coefficient of heat conductivity and water absorption were determined. All experimental samples had a clear geometric shape and specified dimensions. The properties of the obtained samples are as follows: density - 180-300 kg / m ³ , compressive strength - 1.5-3 MPa, heat conductivity coefficient - 0.062-0.085 W / m⋅grad, water absorption - 5-8% (vol.).

The main advantages of the proposed composition and method of obtaining insulating materials is the following:

- in the production of these materials, natural amorphous siliceous rocks are used as feedstock;

- the use of specially welded glass or cullet is completely excluded from the technological process;

- the composition of the charge does not use carbonate, carbon or other blowing agents, and the process of foaming of the mixture occurs due to the release of chemically bound water when heating sodium hydrosilicate to a temperature of 350 ° C and above up to the foaming temperature;

- water evolution during heating leads to the formation of hydrothermal conditions in the charge volume, accelerating the interaction of the second added part of the siliceous rock with sodium hydroxide and the formation of secondary sodium hydrosilicate;

- the use of a dry, crystalline sodium hydroxide as a part of the charge makes it possible to efficiently use the heat of its dissolution in water (42.4 kJ / mol), which sharply intensifies the reaction of formation of primary sodium hydrosilicate and the mixture is heated to a temperature of more than 100 ° C;

- in the synthesis of primary sodium hydrosilicate, the dissolution of 54.5% of amorphous silica rock occurs in an aqueous solution of sodium hydroxide with a concentration of 37.5% (wt.);

- the resulting primary sodium hydrosilicate has a silicate module m = SiO ₂ / Na ₂ O = 2.1-2.2 and is able, especially under hydrothermal conditions, to absorb an additional 45.5% silica rock with the formation of a secondary sodium hydrosilicate with a module m = 2 8-3.2;

- dusting of granules in the aluminosilicate component prevents the granules from sticking together and increases the content of aluminum and iron oxides in the composition of the glass formed during foaming of the charge, increases the viscosity of the glass and its water resistance;

- surface dusting of granules with an aluminosilicate component contributes to the formation of a honeycomb structure of the products during foaming;

- the use of granular charge with a residual relative humidity of 15-18% increases its thermophysical and porous properties, which allows to obtain products in the form of blocks, plates, segments, rings.

When exposed to high temperature on the charge, various physicochemical processes begin to occur in it. First of all, as a result of heating the mixture to 150-300 ° C, dehydration of primary sodium hydrosilicate occurs with the release of water in the form of water vapor, which, under the conditions of a persistent alkaline environment, contributes to a very intensive dissolution of free silica and the formation of secondary sodium hydrosilicate. Dissolution of an additional amount of silica increases the silicate modulus of the mixture to m = 3.0, as a result of which the ability of the mixture to be porous increases. In the temperature range 350–450 ° С, the process of dehydration of sodium hydrosilicates coincides with the process of the transition of the mixture into a pyroplastic state, and the water vapor released forms a sodium silicate glass, which during the pyroplastic state is actively enriched with oxides of calcium, magnesium, iron, and aluminum, which are impurity oxides into the amorphous siliceous rock and into the aluminosilicate component.

An analysis of the advantages of the claimed composition of the charge and the method for producing a heat-insulating material shows that the proposed technical solution to the problem allows us to achieve the goal of the invention and to obtain a heat-insulating material with a rigid structure, given characteristics, dimensions and shape with minimal heat and energy costs. In addition, compared with the known method and composition of the charge, in the present invention, the content of natural, amorphous siliceous rock increases by 1.95 times, and the introduction of aluminosilicate component increases the water resistance of silicate glass and products.

The thermal insulation material obtained according to the invention can be used in construction, for thermal insulation of power plants and pipeline transport.

Claims (3)

1. The mixture to obtain a heat-insulating material, including amorphous siliceous rock, sodium hydroxide and water, characterized in that it further contains an aluminosilicate component in the following ratio, wt.%: Amorphous Siliceous Rock 48-55 Dry sodium hydroxide 15-18 Aluminosilicate component 3-5 Water 24-35 2. A method of producing a heat-insulating material using a charge according to claim 1, comprising mixing the components of the mixture, foaming the mixture and cooling the products during annealing, characterized in that when preparing the mixture, primary sodium hydrosilicate with a silicate module of 2.1-2.2 is first synthesized mixing dry sodium hydroxide with 54.5% of the total amount of amorphous siliceous rock and hot water in the specified amount, ensuring the formation of an aqueous solution of sodium hydroxide with a concentration of 37.5% (wt.), mix sodium hydrosilicate with the rest of the amorphous siliceous rock, granulate the mixture and dust the granules with an aluminosilicate component, then load the granules into molds with a closed volume and foam at a temperature of 760-780 ° C for 20-40 minutes.