RU2247696C1 - Ceramic binder of high-pressure steam curing and method for production of ceramic materials using the same - Google Patents

Abstract

FIELD: ceramic binder and ceramic materials made from the same.

SUBSTANCE: ceramic binder is obtained by thermal treatment of raw materials containing (mass %) clay (e.g., clay waste) 20-45; limestone (e.g., limestone waste) 5-30; and ash (e.g., ash from thermoelectric plant) 25-75, at 900-1150⁰C. Method for production of ceramic materials using the claimed binder includes mixing of raw materials, forming, and thermal treatment at 174-210⁰C under pressure of 0.8-1.6 MN/m² in saturated water steam.

EFFECT: low-cost ceramic materials with reduced volume weight and high mechanical strength.

2 cl, 3 ex, 3 tbl

Description

The invention relates to the production of building materials, namely ceramic materials, including porous and extruded products, and can be used in the manufacture of refractories, heat-insulating materials, alumina brick.

It is known ceramic binder obtained by heat treatment of clay, limestone, brown coal ash and waste metal bismuth production (AS USSR No. 1418312 A1, 08/23/1988, class C 04 B 7/38), containing, wt.%:

- brown coal ash 5.1-6.4

- clay component 20.5-21.6

- waste production of metallic bismuth 0.5-1.0

- chalk the rest

The disadvantages of the famous ceramic binder:

- a narrow range of changes in the composition of the binder;

- the specificity of one of the components of the binder, namely: waste production of metallic bismuth;

- high content of a relatively expensive component - chalk.

A known method of producing silicate brick based on lime-silica binder autoclave hardening (RF Patent No.2000111927, CL 28 V 15/00, analogue), including:

- mixing of binder components;

- mixing a binder with a filler;

- moistening the mixture and extinguishing lime;

- molding;

- Autoclave processing of molded products.

The disadvantages of this method:

- a relatively high bulk density of products;

- insufficient mechanical strength of the products.

There is also a known method of manufacturing ceramic materials based on ceramic binder (RF Patent No. 2204542 C1, C 04 B, 35/10, p.5, prototype), including:

- mixing of raw materials: electrocorundum, sulfate-alcohol mash and ceramic binder - bentonite;

- molding of products;

- pressing in a split mold;

- drying;

- firing molded products.

The specified method is effective in the manufacture of expensive specific ceramics based on high quality raw materials: electrocorundum, bentonite, sulfate-alcohol mash. When using cheap raw materials, production wastes, ceramic materials are of low quality due to incomplete extinguishing of lime and the inhomogeneity of the mixture.

The technical result of the present invention lies in the fact that a method has been developed for producing a new binder of autoclave hardening, with the help of which cheap ceramic building materials are obtained having a reduced bulk density with high mechanical strength.

The technical result of the present invention is achieved by the fact that for the preparation of ceramic knitting autoclave hardening, cheap, non-deficient raw materials are used: clay and limestone waste, ash from thermal power plants, and molded products are heat treated at a temperature of 174-210 ° C and a pressure of 0.8-1.6 MN / m ² in an atmosphere of saturated water vapor.

Clay waste is a secondary clay raw material recognized as unsuitable for use in the manufacture of ceramic materials due to the excess content of carbonate inclusions. Limestone waste is characterized by a high degree of dispersion and is a screening fractionation of limestone before firing.

A study of the prior art found that inventions containing a method for producing ceramic materials based on ceramic cementitious autoclave hardening, further including heat treatment of molded products at a temperature of 174-210 ° C and a pressure of 0.8-1.6 MN / m ² in an atmosphere of saturated water vapor is not detected.

A comparison of the properties of the set of features of the known line of the claimed shows that the known ceramic binder is made on the basis of expensive raw materials: kaolin, talc, lime, and the claimed - on the basis of clay, limestone waste and ash TPP.

A comparison of the properties of the set of features of the known method of manufacturing ceramic materials (prototype) and the claimed shows that:

- in the known method, the molded products are fired at a temperature of 900-2000 ° C, and in the claimed - at a temperature of 900-1150 ° C, a ceramic binder is prepared;

- in contrast to the known inventive method contains the operation of heat treatment of molded products at a temperature of 174-210 ° C and a pressure of 0.8-1.6 MN / m ² .

The invention consists in the following.

The main task of the building materials industry is the production of artificial stones having high mechanical strength with a low bulk density. Artificial stones are obtained on the basis of lime-sand and ceramic binder. The former relate to silicate, and the latter to ceramic building materials.

Silicate building materials are obtained from a mixture of lime and sand by treatment with saturated water vapor at a temperature of 174-210 ° C and a pressure of 0.9-1.6 MN / m ² .

The production of ceramic building materials requires higher energy costs: firing a mixture of clay, lime and sand at 900-2000 ° C - but they are preferable because they have high mechanical strength, water and frost resistance, and have refractory properties.

The high temperature of heat treatment of ceramic mixtures due to the significant content of aluminosilicates. Depending on the origin of the clay, they contain from 10 to 40% alumina, which forms complex anions [Al _n Si _m O _{2 (n + m)} ] ^n- with silicon oxide, which contribute to the incorporation of small-sized mobile cations into the clay structure: K ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ . Therefore, alkaline treatment of clays, mainly using calcium hydroxide (lime), causes loosening of the clay framework structure, activates the formation of long-chain polyaluminosilicates, which primarily determine the mechanical strength of ceramic materials.

Thus, methods for producing ceramic materials suggest the selection of an optimal alkaline medium for the content of Ca ²⁺ , Mg ^{2+ ions} and the optimal heat treatment temperature for each type of clay.

High-grade clays used in the manufacture of porcelain contain 30-42% alumina and a minimum amount of moisture, therefore refractory. With a decrease in the content of aluminum oxide and an increase in hygroscopic humidity, the temperature of the transition of clay to a plastic state decreases, which in turn reduces the energy intensity of production. But traditional methods for producing ceramic materials, based on firing a ceramic mass containing low-grade clays and lime, do not allow obtaining ceramic materials of satisfactory quality.

Using additional processing of the molding mixture, which consists in exposure to saturated steam at a temperature of 174-210 ° C and a pressure of 0.8-1.6 MN / m ² in autoclaves, it is possible to produce ceramic materials based on low-grade clays with good performance ( Tables 1, 2).

The autoclave treatment of the molding mixture “quenches” the free lime, which did not react with clay aluminosilicates during firing, and activates the formation of long-chain polyaluminosilicates.

At the same time, the problem of using low-grade raw materials containing oxides of calcium, magnesium, aluminum: ash of thermal power plants, limestone and clay waste is being solved.

Currently, TPP ash is a widespread secondary raw material for the production of autoclave materials, traditionally based on a lime-siliceous binder.

The chemical composition of the raw materials of ceramic cementitious autoclave hardening "Keramzol" (Example 3) are presented in table 3.

In known methods for the production of autoclave materials, heat treatment of raw materials is carried out only in autoclaves at a temperature of 174-210 ° C. Particles of TPP ash, which almost always has a "burnout" (incomplete oxidation of the fuel) and, therefore, contains weakly reactive components, at this temperature become local defects in the skeleton structure of the artificial stone. Microcracks are formed in the volume and on the surface of the product; the product undergoes deformation.

Obtaining an astringent by roasting allows eliminating the underburning of fuel and at the same time activating the processes of interaction of ash and clay components.

Traditional ceramic products, in the manufacture of which the kiln firing operation is the finish, are made of high-quality clay (primary raw materials) with limitations in chemical composition. The content of basic oxides should be: SiO ₂ - up to 85%, Fe ₂ O ₃ + FeO - up to 14%, CaO + MgO - up to 20%, K ₂ O - up to 7%, SO ₃ - up to 2%. Particularly stringent requirements for the content of limestone inclusions in clay: particle size - not more than 2 mm.

The availability of high-quality clays in the Russian Federation is limited. Most of the proven clay deposits are not suitable for the manufacture of high-quality ceramic products, the production of which is carried out by plastic molding.

When using plastic "greasy" clays as an exhausting additive, ash from TPPs from burning peat and brown coal can be used. For such ash, there are also restrictions on the chemical composition: SiO ₂ - 55 ± 10%, Al ₂ O ₃ + TiO ₂ - 10 ± 2.5%, Fe ₂ O ₃ + FeO - 10 ± 8%, CaO + MgO - up to 12%, SO ₃ - up to 1%.

These limitations aim to achieve the best quality products.

During firing, the structure and properties of ceramic products are formed due to the chemical interaction of minerals, i.e. their oxides that make up the raw material. During firing, Ca and Mg oxides are also formed as a result of decarbonization of CaCO ₃ and MgCO ₃ , which are part of clay and ash. These oxides also interact with other raw material oxides. But a significant amount of oxides remains in an unbound state, since there is no liquid phase at a firing temperature of about 1000 ° C, and reactions occur in the solid phase in the boundary regions of the minerals.

While the oxides of Si, Al, Fe, being mutually unbound, play the role of fillers, the oxides of Ca and Mg, being not bound to other oxides, are highly reactive and form hydroxides of Ca (OH) ₂ and Mg (OH in the presence of moisture ) ₂ . These compounds form with a significant increase in volume, since this occurs in products with a fixed firing structure. These processes lead either to the destruction of products, or a sharp decrease in strength, frost resistance, the presence of efflorescence on the surface.

This explains the desire for the maximum restriction of Ca and Mg carbonates in raw materials.

In the present invention, the finishing operation is the heat-moisture treatment in an autoclave of products at 174-210 ° C and a pressure of 0.8-1.6 MN / m ² in an atmosphere of saturated water vapor.

In this case, the Ca and Mg oxides remaining in the binder after firing, quenched with water in the reactors with the formation of Ca (OH) ₂ and Mg (OH) ₂ hydroxides, enter into chemical interaction with the oxides of Si, Al, Fe, etc. the formation of new minerals that form the structure and properties of autoclave materials. Such neoplasms include compounds: CaO with SiO ₂ - CaO · SiO ₂ (CS), 2CaO · SiO ₂ (C ₂ S), 3CaO · SiO ₂ (C ₃ S), 3CaO · Al ₂ O ₃ (C ₃ A) , 4СаО · Аl ₂ O ₃ · Фе ₂ O ₃ (С ₃ АF), etc. (more than 20 items). Each of these new materials forms certain quality indicators of products.

These reactions of the formation of new materials occur in the aquatic environment.

Thus, the heat-moisture treatment of products not only neutralizes the negative effect of Ca and Mg oxides on the structure of products, but also contributes to the formation of new useful minerals in addition to those that are formed during baking of the binder. As a result, not only the sum of the positive factors of firing of the knitting and heat-moisture treatment of products from it is achieved, but also the production of a new type of building materials: autoclaved ceramic products.

But to obtain the optimal passage of the heat-moisture process in the product, the binder must contain the necessary amount of Ca and Mg oxides:

- for pressed products, wt.% 10 ± 2.5

- for porous products, wt.% 22 ± 5.0

To ensure these conditions, the composition of the mixture for the manufacture of a binder should include: clay raw materials, ash TPP, as well as limestone.

Given the fluctuations in the chemical composition of the components, their content should be, wt.%:

Ash TPP 25-75

Clay waste 20-45

Limestone waste 5-30

Thus, the heat-moisture treatment of ceramic products made of ceramic binder obtained by firing the mixture allows us to use not only primary clay and limestone as raw materials, but also clay and limestone waste, as well as TPP ash, which in itself is industrial waste.

The use of waste is, of course, more preferable, since, as a rule, they do not find industrial application and are much cheaper than primary raw materials. In addition, waste management is of great environmental importance (the liberation of significant areas occupied by waste, elimination and harmful effects on the environment).

Types of waste and their main features

1. Clay waste:

- overburden clays, loams, usually occurring on carbonate raw materials (limestone, dolomites, marls, chalk, shell rock, etc.), such clay waste contains mainly inclusions of underlying rocks, in most cases, such raw materials do not find industrial application even the development of carbonates is discharged into the depleted space in the order of reclamation of quarries;

- clay raw materials, recognized unsuitable for the manufacture of ceramic brick plastic molding;

- coal mining waste (terriconics) and coal preparation, containing, as a rule, high-quality clays randomly littered with coal.

2. Limestone waste:

- trifle (fraction less than 20 mm) when sorting crushed limestones, marls, limestone, unsuitable for calcination in shaft furnaces to obtain calcined calcium lime;

- trifle (fraction less than 5 mm) when sorting chalk, unsuitable for firing in rotary kilns;

- limestone with a content of Ca and Mg oxides of less than 70%, unsuitable for calcining lime, such limestone, as a rule, is contaminated with clay and silicon.

3. Ash of thermal power plants, which is formed during the burning of peat, brown coal, and also mixed fuels (peat + coal in different ratios) in boilers.

Tests of a new technology for the manufacture of ceramic binder and ceramic products based on it were carried out:

1. At the Glubokinsky silicate plant, using as raw materials: coal enrichment waste from the Donetsk mine control (clay raw materials), ash from the Kamensk TPP (coal), limestone waste (fines) from the Glubokinsky ZSK - semi-factory tests.

2. At Kalininsky KSM-1, using as raw materials: ashes of thermal power plants (peat + brown coal), overburden clay (waste) and limestone fines of the Monchalovsky lime plant - factory tests.

3. At the Kraskovsky pilot plant of the Institute VNIIstrom using as raw materials: ash TPP-4, clay and limestone waste Monchalovsky lime plant - routine tests.

A method of manufacturing ceramic materials based on ceramic binder autoclave hardening is as follows:

The ceramic binder obtained by heat treatment at 900–1150 ° С is mixed with filler and special additives, for example, a plasticizer, a surfactant, or a blowing agent, it is molded, for example, by pressing and subjected to heat treatment at a temperature of 174–210 ° С and a pressure of 0.8–1 , 6 MN / m ² in an atmosphere of saturated steam in an autoclave. At the end of the autoclave treatment, finished products are transported to the warehouse.

Examples of recipes for ceramic binder autoclave hardening.

Example 1. Glubokinsky silicate plant.

Components wt.%

Ash TPP 50

Clay waste 40

Limestone waste 10

Ash - SiO ₂ - 45-65%, Al ₂ О ₃ - 15-35%, Fe ₂ О ₃ + FeO - 15-21%, CaO + MgO - 10-14%, SO ₃ - 3%.

Clay waste - SiO ₂ - 50.3-60.4%, Al ₂ O ₃ - 16.8-30.2%, Fe ₂ O ₃ + FeO - 15.1-16.6%, CaO + MgO - 1 , 1-16.2%, SO ₃ - 0.2-1.0%.

Limestone waste - SiO ₂ - 4.1-11.9%, Al ₂ O ₃ - 10.55-10.75%, Fe ₂ O ₃ + FeO - 0.4-1.2%, CaO + MgO - 70 -82%, SO ₃ - 0.5%.

The composition of the binder obtained is SiO ₂ 48.55%, Al ₂ O ₃ 19%, Fe ₂ O ₃ + FeO 13.74%, CaO + MgO 17.2%, SO ₃ 1.8%.

Single bricks (250 × 120 × 65 mm) and stones (250 × 120 × 138 mm) were molded on hydraulic presses LA-550 from the binder obtained by firing in a cupola at 1050 ° С after mixing it with water and quenching for 24 hours were subjected to heat and humidity treatment in an autoclave at 174 ° C and a pressure of 0.8 MN / m ² in an environment of saturated water vapor, while the following product characteristics (average) were obtained:

- compressive strength, MPa 15.2

- bulk mass, g / m ³ 1,5

- water absorption,% 19

- frost resistance 30

- residual activity (CaO + MgO) 1.7

Note: after 30 cycles of alternate freezing and thawing, the samples showed no signs of destruction and no further tests were carried out.

Example 2. Kalinin plant of building materials No. 1

Components wt.%

Ash TPP 50

Clay waste 45

Limestone waste 5

Ash - SiO ₂ - 53.2%, Al ₂ O ₃ - 17.0%, Fe ₂ O ₃ + FeO - 9.1%, CaO + MgO - 12.7%, SO ₃ - 1.1%, Losses on ignition (P.P.P.) - 8.5%.

- calorific value

(from unburned fuel), kcal / kg 262.5

- water absorption,% up to 35

- bulk mass, kg / m ³ about 900

- residue on a sieve of 0.14,% 32

- specific surface, cm ² / cm 2200

- hydraulic activity, m ² / g 54

- type of ash - dump

Clay waste - SiO ₂ - 73.25%, Al ₂ O ₃ - 12.85%, Fe ₂ O ₃ + FeO - 4.47%, CaO + MgO - 4.4%, SO ₃ - 0.4%, P.P.P. - 4.12%.

Sieve residues,%: less than 0.25-6.4; 0.25-0.01 - 40.6; 0.01-0.005 - 15.8; 0.005-0.001 - 12.7; less than 0.001-24.5.

Limestone waste - SiO ₂ - 1.5%, Al ₂ O ₃ - 0.42%, Fe ₂ O ₃ + FeO - 0.57%, CaO + MgO - 54.96%, SO ₃ - 0.45%, P.P.P. - 42.1%.

Granulometric composition, fraction%: less than 1 mm - 4; 1-3 mm - 47; 3-5 mm - 11.5; 5-7 mm - 8.5; 7-10 mm - 29.

The charge is SiO ₂ - 59.64%, Al ₂ O ₃ - 14.22%, Fe ₂ O ₃ + FeO - 6.59%, CaO + MgO - 11.08%, SO ₃ - 0.75%, P .P.P. - 8.2%.

The composition of the binder obtained is SiO ₂ - 64.64%, Al ₂ O ₃ - 15.41%, Fe ₂ O ₃ + FeO - 7.14%, CaO + MgO - 12.01%, SO ₃ - 0.81% .

The binder was fired in a rotary kiln of the expanded clay workshop of the Kalininsky reinforced concrete plant-2 at a temperature of 950-1050 ° C. After the binder was moistened in the mixer and quenched in the reactor, bricks (250 × 120 × 88) were formed from the mixture, which were subjected to heat treatment in autoclaves at 174 ° С and a pressure of 0.8 MN / m ² in a saturated water vapor medium according to the following conditions: pressure increase - 2 hours, holding at maximum pressure and temperature - 8 hours, pressure reduction to 0-2 hours, while the following product characteristics were obtained:

- ultimate compressive strength, MPa 15.5-19.1

- bulk mass, g / m ³ 1.46-1.51

- water absorption,% 19-21.5

- frost resistance 30-35

- residual activity (CaO + MgO) 1.7-2.0

Example 3. Kraskovsky Experimental Plant Institute VNIIstrom

The mixture for the manufacture of a binder was prepared from raw materials for two types of products:

a) For pressed products (brick, stones)

Components wt.%

Ash TPP 50

Clay waste 45

Limestone waste 5

b) For porous products (cellular, thermal insulation and wall blocks)

Components wt.%

Ash TPP 50

Clay waste 20

Limestone waste 30

The mixture was fired in pallets on oven trolleys in a tunnel furnace at 950-1100 ° C.

The binder was moistened in the mixer, extinguished in the reactor. Bricks and stones were molded from the mixture on the Krupp-Intertekhnik and SM-816 presses.

The products were subjected to heat and humidity treatment in an autoclave at 210 ° C and a pressure of 1.6 MN / m ² in a saturated water vapor medium according to the following conditions: pressure rise - 1.5 hours, exposure at maximum pressure and temperature - 4 hours, pressure drop to 0- 1.5 hours, while the following product characteristics were obtained:

- compressive strength, MPa 21.4

- bulk mass, g / m ³ 1.44

- water absorption,% 17.8

- frost resistance up to 50

- residual activity (CaO + MgO) 2,4

Table 1
Characteristics of the production of pressed bricks based on ceramic knitting autoclave hardening in comparison with traditional NN s / n Indicators One meas. Silicate brick Ceramic brick 1. Raw materials Primary:
- quartz sand
- limestone (lime) Secondary:
- ash TPP
- loam
- screening of limestone 2. Type of brick - private facial 3. Dimensions mm 250 × 120 × (65.88) 250 × 120 × (65.88; 138) 4. Voidness % 8-12 22.5-25 5. Bulk mass
- in a dense body
- hollow kg / m ³ 2000
1800 1600
1450 6. Thermal conductivity of a brick in a dense body

0.76 0.55 7. Brand average kg / cm ² 125 125 8. Frost resistance cycle fifteen 35 9. Heat consumption

330 270 10. Power consumption

55 fifty eleven. Cost price

2200 2200 12. Selling price (as of September 2003)

2600 6000

table 2
Characteristics of the production of porous building materials based on ceramic cementitious autoclave hardening in comparison with traditional NN s / n Indicators One meas. Gas silicate Gazokeramzole 1. Raw materials - lime sand binder - astringent "expanded clay" - aluminum powder - sand slurry - surfactant - cement - water - gypsum - aluminum powder - surfactant - water 2. Type of product - structurally insulating blocks heat insulating blocks 3. Bulk mass kg / m ³ 700 500 4. Thermal conductivity

0.40 0.30 5. Strength (grade) kg / cm ³ 25 25 6. Frost resistance cycle fifteen fifteen 7. Heat consumption

163 116 10. Power consumption

fifty 36 eleven. Cost of sales (2003)

1050 850 12. Selling price (as of September 2003)

1250 1250

Claims (2)

1. Ceramic binder obtained by heat treatment of raw components - clay, limestone and ash, characterized in that it contains clay waste as clay, limestone - limestone waste, as ash - thermal power plant ash in the following ratio of components, wt.%: Ash of power plants 25 ÷ 75 Limestone waste 5 ÷ 30 Clay waste 20 ÷ 45 and the specified heat treatment is carried out at 900 ÷ 1150 ^about C. 2. A method of manufacturing ceramic materials based on a ceramic binder, including mixing raw materials, molding, heat treatment, characterized in that they use a ceramic binder according to claim 1, and the heat treatment is carried out at 174 ÷ 210 ° C and a pressure of 0.8 ÷ 1.6 MN / m ² in an environment of saturated water vapor.