RU2332386C2 - Furnace burden for firebrick production - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of complex processing of manufacturing wastes in order to prepare refractory and constructional materials, precisely meant for processing of the broken piece ''Dinas''. The furnace burden for refractory brick production consists of a filler material, sodium water glass according to dry residue, microsilica metallurgic wastes with SiO₂ > 80% and water, it also contains the broken piece of Dinas and aluminium oxide as the filler material, the weight ratio of the components is following: broken piece of dinas - 100.0; aluminium oxide - 3.0-15.0; sodium water glass according to dry residue - 2.5-2.7, water - 4.0-10.0.

EFFECT: strength enhancement and simplification of refractory products manufacturing.

1 ex, 4 tbl

Description

The invention relates to a technology for the integrated processing of industrial waste and secondary raw materials with the aim of obtaining building and refractory materials, namely, the processing of refractory scrap brand "Dinas".

A known method of producing a mixture for unburned refractory products, including grinding a silicate block with a refractory aggregate, mixing them at a temperature of 80-90 ° C, mixing the mass with water at the same temperature. Refractory products are then obtained by molding at a pressure of 40 MPa, the products are dried at a temperature of 250-300 ° C for 1-2 hours (A.S. No. 1701693, С04В 28/24, С04В 40/40, BI No. 48, 21.06. 91) [1].

The method requires preliminary joint grinding and heating of the molding sand (mixture).

A technical solution is known in which the mixture for the manufacture of non-fired building products is obtained by co-grinding a silicate block with a part of the filler, mixing this mass with the rest of the filler. The products are molded at a pressure of 10-20 MPa, pre-steamed at a temperature of 80-90 ° C and a humidity of 90-100% for 1.5 hours, then dried at a temperature of 110-120 ° C. The proposed composition of the mixture: 1-3% silicate blocks, 97-99% sand (US Pat. RF No. 2018498, С04В 28/26, 40/00, 42/02, BI No. 16, 09/30/99) [2].

This composition assumes a rather high content of silicon oxide in an amount greater than 97%.

A known method of obtaining non-fired refractory and building products from a mixture containing a refractory filler chamotte or dinas, including grinding in a ball mill a silicate block with a refractory component - chamotte or quartzite, or dinas, or silicon carbide to a specific surface of 2500-3000 cm ² / g mixing the obtained silicate-sodium composite binder (SNCR) with a filler of the same material as the refractory component at a temperature of 80-90 ° C, and after 3-4 minutes, water of the same temperature is introduced based on water a solid ratio of 0.12-0.14 and finally mixed, the products are molded at a pressure of 40 MPa, then heat treatment is carried out by thermal shock at a temperature of 250-300 ° C for 1-2 hours. The method provides a structurally stable product without preliminary firing, increasing the strength and thermal stability of the products due to the complete dissolution of the silicate block and its uniform distribution in the mixture during mixing. Strength after drying 38.8-56.8 MPa, temperature resistance 62-80 heat exchange. The composition for the charge are given in table 1 (SU 1701693 A1, С04В 28/24, С04В 40/00) [3].

Table 1.
The composition of the charge Component The content of the mixture, wt.% marginal beyond one 2 3 four 5 Dinas-SNCR 70 80 90 60 95 Fine hammer. dinas / silicate block 24/6 16/4 8/2 32/8 4/1

The closest solution selected for the prototype is a method of producing a mixture for non-calcined dinasoquartzite refractory and building products, in which the dinas aggregate is moistened with an aqueous-alcoholic solution of sodium methylsiliconate, then dust-fly production of ferrosilicon or grinding of quartzite is introduced, finely ground quartzite, ferrochrome are added liquid glass, the components are mixed and an additional powder of phenol-formaldehyde resin modified with urotropine is added with the following content of the charge components s, parts by weight: aqueous-alcoholic solution of sodium methylsiliconate - 0.04-0.21; fine quartzite - 11-18.43; ferrochromic slag - 0.3-0.8; siliceous dust-fly-off of the production of ferrosilicon or grinding quartzite - 4.45-8.6; liquid glass - 7.3-11.9; powder of phenol-formaldehyde resin modified with urotropine - 0.48-2.12; dinas filler - the rest. The compressive strength of the refractory is 25.2 N / mm ² , with a bend of 9.5 N / mm ² , the thermal conductivity is 1.42 W / m · K (SU 1719364 A1, 5 С04В 35/14) [4].

This composition contains burnable organic additives that allow you to maintain a dense heat-conducting structure of the refractory at a temperature of 1300-1400 ° C.

The disadvantage of this technical solution is the insufficiently high refractoriness of the products obtained, as well as the use of organic additives that pollute the environment and equipment.

The problem solved by the claimed technical solution is to obtain products with higher refractoriness, corresponding to GOST 4157-79 "Dinas products", due to the integrated processing of industrial waste and secondary raw materials, and the rejection of the use of burnable organic additives.

Technical result

Using the inventive charge taught products with a density of 2.0 g / cm ³ have compressive strength: 320-390 MPa (with the requirements of GOST 4157-79 - 150 MPa), fire resistance: 1620-1680 ° C (according to GOST - 1580 ° C), additional linear growth: 0.27-030 (according to GOST - 0.4).

Secondary raw materials — refractory scrap of dinas — are used as a filler, and metallurgical silica wastes are used as an additive. In addition, this composition does not contain any organic additives that pollute equipment and the environment during the burnout process.

The problem is solved due to the fact that the inventive charge for the manufacture of refractories includes a filler, liquid sodium glass on a dry residue, silica fume metallurgical waste with a content of SiO ₂ > 80% and water, characterized in that it contains dinas scrap and aluminum oxide as a filler the following ratio of components, parts by weight:

Dinas scrap one hundred aluminium oxide 3-15 liquid sodium glass by dry residue 2.5-7.0 silica fume metallurgical waste with SiO ₂ content> 80% 2.5-7.0 water 4-10

As the main filler, secondary raw materials are used - refractory scrap of dinas (waste from the West Siberian Metallurgical Combine, Novokuznetsk). It is pre-crushed, sorted into fractions, mixed with a binder - a mixture of liquid sodium glass and a modifier; aluminum oxide additives (electrocorundum and other aluminum oxide wastes) are used to increase refractoriness.

Products are molded by means of semi-dry pressing at a pressure of 35-40 MPa and a mixture moisture content of 4-10% (with semi-dry pressing, the quality of products is positively influenced by the slowed-down pressing speed and pressure holding at the end of pressing), they are held in air on specially designed pallets installed in shelves up to 24 hours, then heat treatment is carried out in drying chambers at a temperature of 240-400 ° C.

This composition allows you to use part of the raw materials to obtain building products, and part to return to production in the form of refractories.

To obtain products, the most suitable brands of liquid sodium glass with a module of 2.0-3.6 and a density of 1.3-1.6 g / cm ³ . Liquid glasses with such a range of modulus and density are standardly used to produce various building materials. When using lower modules, an additional neutralization of alkali is required, and when using liquid glass with a module above 3.6, the adhesive ability, and hence the strength of the products, drops sharply. Densities of 1.3-1.6 g / cm ³ are also commonly used densities. A density below 1.3 g / cm ^{3 is} rarely used as a bond due to the low content of the basic substance and low adhesive ability, and a density above 1.6 g / cm ^{3 is} rarely used due to the high viscosity (but higher density water glass can also be used after dilution with water).

As a modifier of liquid sodium glass, various silica fume metallurgical wastes (dust ablation) with a SiO ₂ content _of more than 80% can serve. Silica fume is used to prevent swelling of sodium silicates during heat treatment, to increase the strength and water resistance of the final product. Silica fume wastes are best known for the production of ferrosilicon, aluminum fluoride, and silicon. Fly dust taken from different places of even one production process can vary greatly in chemical and particle size distribution. The dust fly of the production of silicon metal may contain 60% or more SiO ₂ and up to 40% carbon, which prevents the particles from sticking together with liquid glass.

Silica fume - a waste from the metallurgical production of ferrosilicon - this is dust fly that occurs during smelting. Dust consists of spherical particles of different sizes, forming a kind of aggregates. The average particle size is 3.0 μm, and the size of aggregates after aging can reach 17.0 μm. Dust is an amorphous substance, a small amount of the crystalline phase is represented by α-tridimite, the specific surface can reach 22 m ² / g, the true density is 2.31 g / cm ³ , while the bulk density is only 0.18-0.2 g / cm ³ . The ablation dust composition by the amount of silicon and iron and aluminum can vary greatly, except for SiO ₂ and Al ₂ O _{3, the} composition may contain an approximate amount of CaO - 1, MgO-1.3, - 5, Fe ₂ O ₃ - 1.7, C - 0.56 wt. .% :, the rest is impurities. The most suitable is the following dust removal composition: 80-97% SiO ₂ , not more than 2% Fe ₂ O ₃ , the rest is Al ₂ O ₃ and other impurities.

The approximate particle size distribution of silica fume samples taken from different sludge collectors should contain:

the number of particles in the region of 1-6 microns - 80-95%,

the number of particles in the region of 15-30 microns is 10-15%.

Artificial silicon dioxide with a specific surface area of 10-50 m ² / g can also be used as a modifying additive for sodium silicates. The choice of artificial silicon dioxide with a high specific surface is due to the fact that the finer the powder particles (it must be taken into account that the processing temperature is low), the more active they are, they interact faster with sodium silicate, more evenly mix with the whole mass. Silica with a lower specific surface can be used, but this can lead to a decrease in water resistance, due to incomplete interaction with sodium silicate or due to the inhomogeneous distribution of the powder in the total mass. However, artificial silicon dioxide is an expensive raw material, compared with silica fume waste, and is rarely used.

Silica fume wastes of metallurgical industries (with SiO ₂ content _of 80% or more) incorporate amorphous silica, which is very active and the specific surface of such an additive, as a rule, is not of great importance (usually the specific surface is in the range of 6-25 m ² / g). This waste should not contain a large amount of chlorine and iron, which destroy sodium silicates, such waste will require an additional amount of liquid sodium glass to neutralize, and this, in turn, can greatly increase the humidity of the mass to an unacceptable value. At the same time, components such as chromium, aluminum, zirconium and many others have an additional reinforcing effect and increase the water resistance of products.

Studies on the use of various grades of the initial secondary raw materials have shown the possibility of their use both on individual grades (fireclay bricks, dinas, electrocorundum combining with chamotte additives), and in the form of their mixtures.

After sorting, the secondary raw materials are crushed and divided into fractions. The proposed option for grinding scrap of refractory material (dinas): crushing on a jaw crusher and fine crushing on a cone crusher to obtain a fraction of up to 15 mm.

By selecting the fractional composition, humidity and pressing conditions, you can adjust the density of the products.

To obtain bricks with a density of 2 g / cm ³ and 3-linear sizes (see Table 2), a fraction of recycled materials with particle sizes below 5 mm was used.

Table 2.
Linear dimensions of finished products Type of refractory The apparent density, g / cm ³ linear dimensions length mm width mm thickness mm Dinasovy 2 150 130 65 GOST 4157-79 2 230 130 67 2 380 130 120

The inventive charge was obtained as follows.

Liquid sodium glass (table 3, sample 1) 3.4 wt.h. mixed with 6.7 parts by weight of silica fume and water (until the final moisture content of the mixture was 5% by weight), the so-called binder was obtained, dinas was added in portions, mixed until homogeneous, pressed at a pressure of 38 MPa. After pressing, the products were kept in air for 5-6 hours to gain strength of 5-6 kgf / cm ² , after which they were heat treated at 240 ° C for 4 hours to accelerate the passage of the chemical reaction and obtain the final strength and water resistance. The properties of the obtained refractories are summarized in table 4.

Table 3.
The composition of the mixture for bricks (density 2 g / cm ³ ) Refractory No. (DIN GOST 4157-79) The content of dinas, parts by weight The content of Al ₂ About ₃ The content of liquid sodium glass (dry residue), parts by weight The content of the modifier, parts by weight one one hundred 12.0 3.4 6.7 2 one hundred 3 2.5 2.5 3 one hundred 15.0 7.0 7.0 four one hundred 7.0 7.0 5.0 Analog [3] 72.5 Fine Quartzite-4.0 11.9 8.6 Prototype [4] Dinas-SNKV (sodium silicate composite binder) 80 - Fine Dinas / Silicate block 16/4 -

Table 4.
Refractory Properties No. The apparent density, g / cm ³ Compressive strength, kgf / cm ² (MPa) Refractoriness, ° С Additional linear growth,% one 2.0 385 (38.5) 1680 0.27 2 2.0 320 (38.0) 1600 0.30 3 2.0 330 (36.0) 1640 0.27 four 2.0 390 (38.0) ¹ 1620 0.29 5. Analogue 5a. 329 (32.9) ² 1300-1400 - 5 B. 247 (24.7) ³ - 6. Prototype 552 (55.2) ⁴ - - GOST requirements 2.0 150 (15) 1580 0.4 ¹ Strength (samples 1-4) after heat treatment of 240 ° C
² Strength (sample 5a) after heat treatment 120 ° C
³ Strength (sample 56) after heat treatment of 1400 ° C
⁴ Durability after thermal shock at 275 ° С for 1.5 hours

When the content of alumina is less than 3 parts by weight the fire resistance of products decreases, with an increase above 15 parts by weight strength decreases.

When the content of liquid sodium glass is below 2.5 wt.h. the strength of the products decreases, with an increase above 7 parts by weight fire resistance decreases.

When the content of the modifier is less than 2.5 wt.h. the strength of the products decreases, with an increase above 7 parts by weight cost increases.

When the water content is less than 4 wt.%, Greater pressures are required when pressing, with an increase in the moisture content of the mixture more than 10 wt.%, The strength of the products decreases due to cracking during drying and firing.

A decrease in the processing temperature below 240 ° C does not allow the reaction to go through, therefore, a decrease in the strength and water resistance of the products is observed. An increase in the processing temperature from 240 to 400 ° C does not affect the properties of refractory products (they have sufficient mounting strength, and in the process of increasing the temperature, up to the working temperature, a further increase in strength is observed, while shrinkage remains within acceptable limits (significantly lower than 0.4%) For construction products, a treatment temperature of 350-400 ° C is more preferable to obtain greater water resistance.

Thus, scrap of refractory materials can be used again for the production of refractory (as well as building) materials based on silicate binder containing a modifier.

Compared with the prototype of the inventive charge allows you to get products that comply with GOST 4157-79 "Dinas products", but with higher refractoriness, in addition, the composition eliminates the use of burnable organic additives that degrade the environment.

Due to the integrated processing of industrial waste and secondary raw materials, the economic, social and environmental effectiveness of the proposed technical solution is not in doubt.

Literature

1. A.S. No. 1701693, С04В 28/24, С04В 40/40, BI No. 48, 06/21/91.

2. Pat. RF №2018498, С04В 28/26, 40/00, 42/02, BI №16, 09/30/99.

3. SU 1701693 A1, С04В 28/24, С04В 40/00.

4. SU 1719364 A1, 5 С04В 35/14 (Prototype).

Claims (1)

The mixture for the manufacture of refractories, including aggregate, liquid sodium glass on a dry residue, silica fume metallurgical waste with a content of SiO ₂ > 80% and water, characterized in that it contains Dinas scrap and aluminum oxide as a filler in the following ratio of components, parts by weight .: Dinas scrap one hundred aluminium oxide 3-15 liquid sodium glass by dry residue 2.5-7.0 silica fume metallurgical waste with SiO ₂ content> 80% 2.5-7.0 water 4-10