EA021140B1 - Method for producing foamsilicate - Google Patents

Abstract

The invention relates to production of building materials, in particular, to a method of producing noneorganic porous materials (heat-insulating and structural heat-insulating) foamsilicates from widely spread siliceous rock (tripoli, diatomite, gaize and the like). The foamsilicate is produced by mixing crushed siliceous rock with soda ash, wetting by an aqueous solution of liquid glass with volume ratio of liquid glass to water 2:1-1:1 or a mixture of said aqueous solution of liquid glass with NaOH 30-40% solution with volume ratio 5-9:5-1 correspondingly. The wetted mixture is granulated, dried at a temperature not exceeding 300°C and calcined at 700-900°C. The total mass content of sodium oxide to siliceous mass is 0.1-0.4. Implementation of the invention provides to produce a wide range of porous foamsilicates - heat-insulating blocks with 150-250 kg/mdensity and structural heat-insulating blocks exceeding 250 kg/mdensity and also granulated by bulk density of 80 kg/mand higher.

Description

The invention relates to the production of building materials, in particular, to a method for manufacturing inorganic porous materials (heat-insulating and structural-heat-insulating) foam silicates from widespread siliceous rocks (tripoli, diatomite, flask, etc.).

Inorganic composition block and granular heat-insulating porous building materials obtained from glass powders with a blowing agent are known. All types and classes of such materials are designated by a single term - foam glass (block or granular).

With all the positive properties of the foam glass, it is not widely used due to the high cost of glass melting. Glass break has a limited raw material resource. To reduce the energy costs of foam glass production, more and more attention is currently being paid to the development of the production of foams from natural raw materials - aluminosilicate and siliceous rocks without preliminary melting into glass. Siliceous rocks - tripoli, diatomite, flask, etc. are widespread and available for mining rocks. Foam materials made from siliceous rocks or with their partial use, it is more appropriate to call foam silicate.

A known method of producing block foam silicate from powders of glass, sand, blowing agent and a solution of sodium silicate (water glass). The components are mixed, pellets are formed from the mixture by the pelletizing method, they are placed in heat-resistant forms and fired at a temperature of 760-800 ° C. At this temperature, the granular charge melts and foams to form a single foam silicate block. Granulation of the powder mixture according to a known solution is carried out to eliminate dusting in the furnace compartment. The density of the foam silicates obtained by a known solution is 220-265 kg / m ³ (RF patent No. 2225373, IPC С03С 11/00, publ. 03/10/2004 [1]).

Such a porous building material to a greater extent is foam glass, since it is made from a composition that mainly contains glass breakdown powder. In the compositions of the known solution per 1000 g of glass powder, sand consumption is 20-40 g.

The development of methods for the manufacture of porous building materials from siliceous rocks without using glass in compositions and without preliminary melting of natural raw materials into glass has been going on for a long time (Gorlov Yu.P. Technology of heat-insulating and acoustic materials and products. M: Higher school, 1989, p. 197- 207 [2]). In all known methods and compositions for the production of silicate foam materials, silica rocks use an alkaline component as an aqueous component - an aqueous solution of sodium hydroxide (плавαΟΗ). Since sodium hydroxide is added to the crushed raw material in the form of an aqueous solution, it is better homogenized with siliceous powder and therefore exhibits fluxing properties better than other known Να-containing solid compounds (carbonates or sodium sulfides, etc.).

In addition to lowering the melting point of silicate compositions, dissolved sodium hydroxide interacts with highly reactive amorphous silica of siliceous rocks to form hydrated sodium silicates, which are a source of water vapor that swell the silicate mass when heated. However, alkali is a dangerous compound belonging to the 2nd class of harmfulness.

A known safe melt that reduces the melting point of silicate masses is soda ash (Να ₂ ί'.ί ₃ ). which is widely used when cooking glass. In the manufacture of silica foam silica rocks, soda ash is not used. This is due to the fact that in a dry state its fluxing effect on siliceous rock is much worse than sodium hydroxide. It cannot be used in the form of an aqueous solution, since when drying soda is salted out on the surface of the mass.

The lack of a method for producing silica foam with alternative safe meshes limited the possibility of organizing the production of porous building materials from natural siliceous raw materials.

Of the large number of known solutions for the production of foam silicate building materials, one can cite those that most fully reflect the essence of the manufacture of porous materials from siliceous rocks and are closest to the proposed invention.

For example, porous building materials and a method of their manufacture from siliceous natural raw materials are known - diatomites, spongolites, flasks, tripoli, zeolites and others with an alkaline component of sodium hydroxide solution (ΝαΟΗ) (RF patent No. 2300506, IPC С04В 28/24, С04В 111 / 20, С04В 111/40, published on June 10, 2007 [3]).

The manufacturing method consists in grinding siliceous rock, mixing with an aqueous solution of caustic soda with a concentration of 46 wt.% With an alkaline component to powder ratio of 0.080.40, the silicate mass is dried to a residual moisture content of less than 5%, then it is crushed to a size of not more than 100 microns, the powder is poured into molds and heated to a swelling temperature in the temperature range of 650-900 ° C and then cooled in a certain cooling mode.

According to this decision, both heat-insulating building material with a density of 90-150 kg / m ³ and structural and heat-insulating with a density of 240-370 kg / m ^{3 are} obtained.

The main disadvantages of this method of manufacturing porous building materials from natural siliceous raw materials are as follows:

- 1 021140 double grinding. The siliceous rock is first crushed, and then a dry silicate alkaline mass is crushed to a high degree of fineness (less than 100 microns);

high dustiness of the furnace compartment, as fine powder is poured into the molds. This requires good sealing of the molds and conveying devices and without fail the presence of covers for heat-resistant molds to prevent dusting of the internal volume of the furnace;

long-term heating of the foaming powder mixture in heat-resistant forms in the following sequence: 145-155 - 6-12 hours; 170 - 6-8 hours; 190 - 6-8 hours; 250 - 6-8 hours; 320 - 6-8 hours; 580-600 - 68 h; 680-720 - 3-4 hours. With such a long-term regime, building material with its highest quality will not be economically competitive;

the use of sodium hydroxide as a flux, an expensive compound with a high class of harmfulness.

There is another method for producing porous building material from siliceous natural raw materials also with sodium hydroxide solution as flux (RF patent No. 2333176, IPC С04В 28/26, С04В 111/20, publ. September 10, 2008 [4]). According to this method, a heat-insulating porous material with a density of 180-200 kg / m ^{3 is} obtained, structural heat-insulating material with a density of 400 kg / m ³ and granular with a bulk density of 200-250 kg / m ³ . In addition, the method provides for obtaining a wide range of structural material with a density of 1500-2000 kg / m ³ (paving slabs, bricks, blocks, etc.).

According to the known method, the siliceous rock is dried, the term is treated at 250-700 ° C for at least 0.5 hours, crushed to a fraction of less than 5 mm. The crushed siliceous rock, alkali and water are mixed, kept at a temperature from 0 to 150 ° C for at least 0.2 hours to form hydrosilicates, then the silicate mass is dried, milled to a powder, and subjected to heat treatment in the range of 250-700.

The production of block foam is carried out by foaming pre-heat-treated prepared powder mixture in heat-resistant forms. Dense building material is obtained by firing pressed blanks on a conveyor belt. The granular porous aggregate is obtained by firing in a rotary kiln after rolling the powder mixture into granules of 5-10 mm in size on a plate granulator.

The main disadvantages of the known solutions for obtaining porous building materials from siliceous raw materials are the following:

high temperature heat treatment of siliceous rock before grinding 250-700 ° C, the need for which in the known solution is not explained. For good grinding, it is enough to dry the rock at 100 ° C;

grinding silicate raw materials to a fraction of less than 5 mm With such coarse grinding it is impossible to obtain a homogeneous alkaline silicate mass with good ability to pore formation. Grinding to a fraction of 0.5 mm (example 2) is also an insufficient level of grinding silicate rocks to obtain high-quality porous products;

the need for re-grinding the dried alkaline silicate mass and re-heat treatment;

molds for producing block foam are filled with powder, which creates a high dust content in the furnace compartment;

the use of sodium hydroxide as a flux, an expensive compound with a high class of harmfulness.

A known method of manufacturing a heat-insulating material, comprising mixing crushed siliceous rock and an alkaline component, keeping the alkaline moistened mixture at a positive temperature for 2-24 hours, followed by expansion at a temperature of 650-750 ° C for 5-40 minutes until the initial volume of the mixture increases less than 10%, after which the expanded mass is subjected to grinding to a fraction of less than 0.5 mm, then the resulting powder mixture is poured into molds, heated to a temperature of 700-800 ° C and held for 15-60 minutes to oroobrazovaniya molten mass (RF Patent № 2,323,191, IPC S04V 28/26, S04V 40/00, publ. 27.04.2007 [5]).

In this way, block foam is produced with a density of 200-400 kg / m ³ . The intermediate swelling of the dry mass, which is carried out before filling the powder mixture into heat-resistant forms, makes it possible to obtain a foam silicate material with good strength characteristics up to 80 kg / cm ² (8.0 MPa). However, the known method is characterized by typical disadvantages associated with powder technology:

high dust content in the furnace compartment;

the need for double grinding. First, the rock is ground, then the dried alkaline silicate mixture;

the use of sodium hydroxide as a flux, an expensive compound with a high class of harmfulness.

Closest to the proposed invention is a method of manufacturing heat-insulating materials based on siliceous rocks, comprising mixing crushed siliceous rock and an aqueous solution of sodium hydroxide, laying the wet mixture in molds, preheating the mixture at a temperature of 40-60 ° C for 30- 60 min, heating to 800-900 ° C and holding at this temperature for 20-30 min (RF patent No. 2154618, IPC С04В 38/00, publ. 20.08.2000).

Laying in a heat-resistant form of wet mass in a known solution prevents dust from the furnace compartment. A single grinding of only the initial siliceous rock reduces the cost of production. Preheating the wet alkaline mixture ensures the complete passage of the process of silicate formation, and therefore the mass is characterized by intense pore formation during firing. By this method, a porous silicate material with a density of 100-300 kg / m ^{3 is} obtained.

The disadvantages of this method are as follows:

when the wet mass is poured into the mold, voids inevitably form in it, which, when foaming, form large caverns and inhomogeneities of the porous system in the block;

only alkali, sodium hydroxide, is used as flux. This compound is toxic and will require the organization of a high level of protection for staff;

limited range of porous material. The known solution does not provide for structural-insulating block and granular foam.

The technical result of the proposed invention is to increase environmental safety, reduce production costs and expand the range of porous products from natural siliceous raw materials with obtaining both heat-insulating and heat-insulating structural block foam silicate, as well as granular.

The technical result is solved due to the fact that in the inventive method for the production of foam silicate, including the preparation of a moistened mixture of crushed siliceous raw materials with the addition of a sodium-containing compound, laying the mixture in a fencing device and its heat treatment by preheating and firing, the silica raw materials are mixed with soda ash before wetting, and moistening the mixture is carried out with an aqueous solution of a sodium-containing compound, and the ratio of the total mass of sodium oxide to the mass of cr Amnesties 0,10,4 feedstock is moistened mixture is granulated before laying, and the preheating is carried out at a temperature not higher than 300 ° C. In this case, an aqueous solution of liquid glass is used as an aqueous solution of the sodium-containing compound at a volume ratio of liquid glass to water of 2: 1-1: 1 or a mixture of the specified aqueous solution of liquid glass with a 30-40% solution of ΝαΟΗ at a volume ratio of 5-9: 5- 1 respectively.

Moistening of siliceous raw materials with an aqueous solution of liquid glass or with a mixture of solutions of liquid glass and sodium hydroxide has a complex positive effect on the silicate mass. Moistening with the proposed solutions allows using a safe compound as soda ash as the main melt. The soda ash in a siliceous composition interacts with the components of water glass, forming complex sodium-containing compounds, and therefore, during drying, it does not saline on the surface of the mass. Moisturizing increases the contact of soda ash with particles of siliceous raw materials due to which its fluxing effect is improved compared to a dry mixture. In addition, sodium oxide, which is part of the proposed moisturizing solutions, has an additional fluxing effect on the silicate composition. In addition, liquid glass plays the role of a source of pore-forming gas - water vapor.

The restriction on the total content of Να ₂ Ο is determined by the optimality of technological processes and the type of porous product. When the ratio of the total content of the mass of sodium oxide to the mass of siliceous raw materials is less than 0.1, glass formation in the siliceous composition proceeds weakly and the granules do not swell, and with a ratio of more than 0.4, the melt viscosity decreases and the porous structure settles rapidly.

The concentration limit in the sodium hydroxide solution of 30-40% is determined by technological feasibility. There is no need to work with a higher concentration, since such solutions can crystallize quickly. At a lower concentration, the minimum density of the foam silicate is not achieved.

Granulation of the moistened charge, in addition to the known elimination of dust in the furnace compartment [1], in the proposed invention provides improved product quality and reduced production costs. This is due to the fact that the heating of individual granules proceeds faster and more uniformly than the entire moistened mass of the charge. When foaming individual granules with their subsequent coalescence and the formation of a monolithic block, voids or non-foamed sections do not appear in it, which inevitably occurs when laying in the form of a wet mass according to the prototype. In addition, the granular charge during storage is not caked and is a workpiece for two types of products at once - for block and granular foam silicate.

The drying of granules is necessary to give them strength and stabilize properties. Granules should not be destroyed during transportation and during subsequent heat treatment. Granules can be dried at any positive temperature not exceeding 300 ° C. The restriction on the temperature and temperature of drying is associated with technological and economic feasibility. Drying granules at a higher temperature will lead to unreasonably high heat costs. Dried granules at a temperature not exceeding 300 ° C acquire sufficient strength so as not to break when abruptly heated during firing. In addition, an unproductive gas phase is removed from the granules within this temperature, which improves its sintering during firing.

Implementation of the proposed invention allows to obtain a wide range of porous foam silicates: heat-insulating - with a density of 150-250 kg / m ³ , heat-insulating and structural - with a density above 250 kg / m ³ , and granular - with a bulk density of 80 kg / m ³ and above. The foam silicates obtained by the proposed solution are characterized by high homogeneity of the porous macrostructure in any density range. In porous products there are no blisters or non-foamed areas.

The drawing shows photographs of the porous structure of a foam silicate with a density of 150 (a) and 500 (b) kg / m ³ , which shows that the porous structure in both heat-insulating foam silicate with a low density and a denser heat-insulating structural is characterized by a high uniformity of distribution pore size.

Penosilicates by the proposed method is formed as follows. The crushed siliceous powder of any kind (tripoli, flask, diatomite or other siliceous rocks) from any deposit is mixed with soda ash in mixers of any type, after which the powder mixture is moistened with liquid additives. The ratio of liquid additives to solid components is selected in such a way that granules are formed from the mass in plate-shaped, paddle-type granulators, by extrusion from a plastic mass, or by any other method. Finished wet granules, if necessary, are dusted to prevent sticking to each other and dried in drying units of any type to remove physically bound water. Dry granules can be stored in storage unlimited time. The prepared granular charge is used both for the manufacture of block and granular foam silicate. If it is necessary to produce foam silicate from a specific grain fraction, the granulate is dispersed into fractions.

In the manufacture of block foam silicate, dry granules are poured into heat-resistant forms, which are fed to a foaming furnace, where they are heated to the temperature of melting and pore formation. The molds are held at maximum temperature until the desired increase in the volume of foam silicate and the formation of a monolithic porous block. The cooling and annealing of block foam silicate is carried out according to the generally accepted modes in the foam glass industry.

In the manufacture of granular foam silicate, dry granules are fed to kiln units in which the granules are fired without sticking together. Most often, rotary kilns are used with partial filling of the furnace space with bulk material with a higher melting point than granules (sand, brucite, etc.) to prevent them from sticking together. Pellets can be fired on any other kilns. For example, a fine fraction of foam silicate is produced in fluidized bed furnaces.

Some manufacturing options for block and granular foam silicates are given in the examples (see table) using the flask of the Shipovsky deposit and Tripoli of the Potaninsky deposit, which do not exhaust the possibilities of the proposed method. The method allows the use of siliceous rocks of any deposits.

No. p / p The composition of the dry mixture, wt.% Sosgav moisturizing solution * The volume of solution per 100 g of dry mixture, ml Ratio by weight KagO / siliceous raw materials Pellet drying temperature, ^& C Tempera- the tour firing, ° C Density of block foam silicate, kg / m ^? Bulk density granular silicate foam kg / m '’ one Flask -90 Soda -10 solution 1 (1: 1) 60 od one hundred 900 720 400 2 Flask - 85 Soda -15 RR 1 (2: 1) 80 0.17 one hundred 850 300 200 3 Flask - 80 Soda -20 RR 1 (2: 1): rr 2 (40%) = 5: 5 80 0.4 300 750 150 80 4 Flask - 87 Soda -13 solution 1 (1.5: 1): solution 2 (30%) = 9: 1 70 0.24 200 850 500 260 5 Flask - 85 Soda -15 RR 1 (1: 1) ' solution 2 (35%) - 7: 3 75 0.25 150 800 350 230

* Moisturizing aqueous solutions in the examples are indicated as follows: aqueous solutions of water glass - solution 1 (w.s .: in = 2: 1-1: 1); solution 2 - ΝαΟΗ (30-40%).

Claims (2)

CLAIM 1. A method of manufacturing a foam silicate, including the preparation of a moistened mixture of crushed siliceous raw materials with the addition of a sodium-containing compound, laying the mixture in a fencing device and its heat treatment by pre-heating and firing, characterized in that the siliceous material is mixed with soda ash, and the mixture is moistened with an aqueous solution sodium-containing compounds, and the ratio of the total mass of sodium oxide to - 4 021140 the mass of siliceous raw materials is 0.1-0.4, the moistened mixture is granulated before laying, and preliminary heating is carried out at a temperature not exceeding 300 ° C. 2. The method according to claim 1, characterized in that an aqueous solution of liquid glass is used as an aqueous solution of a sodium-containing compound with a volume ratio of liquid glass to water of 2: 1-1: 1 or a mixture of the specified aqueous solution of liquid glass with a 30-40% solution No. OI with a volume ratio of 5-9: 5-1, respectively.