RU2539519C1 - Mix for production of refractory with forsterite bond - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: this mix comprises granular periclase, dispersed periclase, granular magnesian-silicate component, dispersed magnesian-silicate component and binder. Note here that said granular periclase is a vitrified periclase with density of at least 3.30 g/cm³ and/or fused periclase. Mix dispersed component is the mix of periclase with MgO weight fraction over 97% and magnesian-silicate component and/or zirconium silicate at the following ratio, in wt %: granular periclase with weight fraction of MgO of 93-97% - 50-80, granular magnesian-silicate component - 5-30, dispersed component of the mix of periclase with weight fraction of MgO over 97%, and magnesian-silicate component and/or zirconium silicate - 15-35, and binder over 100% - 3.5-5. Dispersed component of the mix contains additionally the zirconium dioxide ZrO₂ or titanium dioxide TiO₂.

EFFECT: good resistance to cyclic thermal effects and corrosion.

3 cl, 1 tbl

Description

The invention relates to the refractory industry and can be used for the manufacture of heat-resistant refractory products with forsterite bonding, intended for the lining of rotary cement kilns, shaft furnaces and other high-temperature and heat-exchanging units.

A known mixture for the manufacture of refractory with forsterite bonds, consisting of 15-30% of zircon mineral (ZrSiO ₄ ) and sintered periclase. Periclase of the following fractional composition is used: less than 0.1 mm, 0.1-0.5 mm, 0.1 mm - 4 mm; and finely divided zirconium silicate, in which the content, wt.%:

particles with a size of less than 0.1 mm from 10 to 20,

particles with grain sizes from 0.1 to 0.5 mm from 5 to 20 (DE 3720460 from 06/20/1987, IPC С04В 35/043).

As the main component indicated in the claimed solution, only sintered periclase is used for the production of refractories with forsterite bonding, which is characterized by less corrosion resistance to aggressive components in the service compared to fused periclase. In addition, the absence in the charge of a granular magnesia-silicate component (zirconium silicate) with a grain size of not more than 3 mm will reduce the likelihood of the formation of a plastic structure formed due to differences in the temperature coefficients of linear expansion of periclase and magnesia-silicate component.

A known mixture for the manufacture of refractory, prepared from 30-95% synthetically made fine component from fused forsterite with a grain size <1 mm, 5-70%, at least one coarse component from the group: sintered magnesia, fused magnesia, with grain size > 1 mm, up to 5% sintering additive (clay suspension), not more than 5% of other components (possibly impurities). Restrictions on the content of CaO in the mixture <2% and ZrO ₂ / ZrSiO ₄ <0.5 (US 8138110 dated November 7, 2008, C04B 35/20).

The obligatory presence in the known charge of up to 5% clay sintering additive causes the presence of a mass fraction of Al ₂ O ₃ (for clays of various deposits it ranges from 25 to 40%). Alumina Al ₂ O ₃ when interacting with magnesium silicate in the form of fused forsterite 2MgO · SiO ₂ promotes the formation of a low-melting cordierite phase (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) with a melting point of 1460 ° C filling the pores, which, as a result, reduces high-temperature indicators, such as heat resistance, the temperature of the onset of deformation, and also leads to an uncontrolled change in the linear dimensions of the product during cyclic temperature exposure in service conditions.

A known mixture for the manufacture of refractories containing sintered periclase and forsterite material in an amount of not less than 5%, and may be in an amount of from 10 to 35%. You can use any forsterite material, in particular olivine, the higher the content of forsterite, the better. Olivines and similar materials containing a predominant amount of forsterite are ideal raw materials for the formation of a crystalline strengthening lattice. The refractory can be made from a mixture of 85% MgO (periclase) and 15% natural olivine. Periclase can be of any type, for example, with an MgO content of 85%. Periclase should be a larger fraction than forsterite. Firing products at temperatures above 1600 ° C (US 2026088, 1935).

A disadvantage of the known mixture is the use of periclase with a low degree of purity. The indicated level of the mass fraction of MgO in the periclase component — about 85% — suggests the presence of a significant mass fraction of “impurity” oxides (up to 15% in total). In the process of firing products, impurity components at a firing temperature of more than 1600 ° C indicated in the well-known patent primarily form a series of low-melting compounds, such as monticellite (with a melting point of 1430 ° C), mervinite (with a melting point of 1436 ° C), cordierite ( with a melting point of 1460 ° C), etc. As a result, the high-temperature indicators of the properties of the finished products are reduced, in particular, the temperature at which deformation begins, and the products are subject to uncontrolled changes in linear dimensions during service. The presence of low-melting glass phases filling pores and microcracks in the refractory significantly reduces its resistance to cyclic and thermal effects of the medium and fired materials.

A mixture is also known for the manufacture of refractory materials with forsterite bonding, consisting of magnesium oxide (periclase) and a plasticizing component - granular (granular) forsterite (in particular, olivine) or the material that forms forsterite, in an amount of from 3 to 30%. A feature is the plasticizing and crusting effect of forsterite in a joint action with the base material. A microfractured structure forms in the refractory matrix due to different linear expansion coefficients. To achieve a plasticizing effect, granular forsterite is used, namely more than 50% (preferably 70-80%) of a fraction of 1-6 mm and from 0-50% of a fraction of 0.25-1 mm (RU 2412132 from 02/06/2007, IPC С04В 35 / 043).

When determining the influence of various temperature coefficients of linear expansion of periclase and forsterite-forming material, it is necessary to take into account the anisotropy of forsterite during thermal expansion. Depending on the direction along the axes of LTEC, the anisotropy of forsterite is:

x - 13.6 · 10 ^-6 K ^-1 ,

y - 22.0 · 10 ^-6 K ^-1 ,

z - 7.6 · 10 ^-6 K ^-1 , thereby causing the uncontrolled formation of microcracks of various intensities and lengths in different directions. Such uneven crack formation can have a negative effect on the relationship between the matrix and the granular components and lead to a decrease in the strength characteristics of the refractory, which is aggravated by the presence of a forsterite-forming material of a sufficiently large fraction - up to 6 mm.

The technical result consists in obtaining a refractory with a thermoplastic structure, resistant to cyclic thermal and corrosive effects of aggressive components in the service.

The specified technical result is achieved in that the mixture for the manufacture of refractory with forsterite bonding, including granular periclase, dispersed periclase, granular magnesia-silicate component, dispersed magnesia-silicate component and a binder, ACCORDING TO THE INVENTION as a granular periclase contains less densely densified 3 , 30 g / cm ³ and / or fused periclase, and the dispersed component of the charge is a mixture of periclase with a mass fraction of MgO> 97% and magnesia-silicate component and / or zirconium silicate in the following ratio, wt.%:

granular periclase with a mass fraction of MgO 93-97% 50-80 granular magnesia-silicate component 5-30 dispersed component from a mixture of periclase with MgO> 97% and magnesia-silicate component and / or zirconium silicate 15-35 binder, in excess of 100% 3,5-5

Additionally, the dispersed component of the charge may contain zirconia ZrO ₂ or titanium dioxide TiO ₂ in an amount of 1-6%.

One of the features of the present invention is that the mixture uses a combination of periclases of various purities: granular periclase with an MgO content of 93-97% and dispersed periclase with an MgO content of> 97%.

As the granular component, densely sintered periclase with a density of at least 3.30 g / cm ³ and / or fused periclase is used, the mass fraction of MgO being in the range of 93-97%, and the maximum grain size is not more than 6 mm. Preferably, granular periclase is represented by a different combination of the following fractions: 5-3 mm, 3-1 mm, 3-0.5 mm, 2-1 mm, 2-0.5 mm, 1-0.5 mm, 0.5-0 , 1 mm.

The granular component also uses a magnesia-silicate component with a maximum grain size of not more than 3 mm, preferably the granular magnesia-silicate component is represented by a different combination of the following fractions: 3-1 mm, 3-0.5 mm, 2-1 mm, 2- 0.5 mm, 1-0.5 mm, 0.5-0.1 mm. The content of the granular magnesia-silicate component in the charge is selected experimentally and is 5-30% of the weight of the entire charge. The use of a magnesia-silicate component with a grain size of more than 3 mm can lead to uncontrolled expansion of its grains during firing and the formation of an unevenly fractured structure with reduced strength parameters, which is associated with the anisotropy of this material during thermal expansion.

Another feature of the claimed invention is a refractory matrix, which is a dispersed mixture of periclase with a mass fraction of MgO> 97% and the magnesia-silicate component and / or zirconium silicate ZrSiO ₄ . Dispersed periclase (sintered and / or fused) is used with a mass fraction of MgO> 97%. The dispersed component forming the refractory matrix, consisting of refractory compounds (forsterite, periclase, and, in some cases, calcium zirconate, zirconium dioxide) contributes to the formation of a corrosion and thermally stable structure. The particle size of the dispersed component is not more than 0.063 mm.

The dispersed mixture contains at least two of the listed components. When the mixture contains three components, the ratio of periclase with MgO> 97% and the total amount of the magnesia-silicate component and zirconium silicate ZrSiO ₄ is (10-90) :( 90-10). When the mixture contains two components, the ratio of periclase with MgO> 97% and the magnesia-silicate component is (10-90) :( 90-10).

As zirconium silicate is used zircon, zircon concentrate.

As a magnesia-silicate component, fused forsterite, olivinite, or dunite, serpentinite, talc magnesite, etc., previously calcined at a temperature of about 1500 ° C, are used. To increase the MgO content, the indicated materials (dunite, serpentinite, talc magnesite) can be fired in a mixture with periclase-containing components.

In the presence of a high content of CaO impurity (> 2%) in the periclase during the firing process, at temperatures above 1400 ° C, fusible monicellite (with a melting point of 1430 ° C) is formed by the reaction:

Mg ₂ SiO ₄ + CaO → CaO · MgO · SiO ₂ ^.

To bind this impurity oxide present in periclase, the dispersed part of the charge may additionally include zirconia ZrO ₂ , for example, in the form of baddeleyite or titanium dioxide TiO ₂ , for example, in the form of rutile concentrate or pigment titanium dioxide, which form upon interaction with CaO, calcium zirconates (CaO · ZrO ₂ with a melting point of 2350 ° C) or calcium titanates (CaO · TiO ₂ with a melting point of 1975 ° C), which neutralizes the harmful effect of impurity calcium oxide by the reactions:

ZrO ₂ + CaO → CaZrO _3;

TiO ₂ + CaO → CaTiO _3.

The formation of these compounds in the structure contributes to the additional protection of the matrix from the corrosive effects of aggressive components. These additives (zirconia ZrO ₂ or titanium dioxide TiO ₂ ) are introduced into the mixture in an amount of 1-6%.

As a binder, for example, lignosulfonates, dextrin, starch, methyl cellulose, resins, etc. can be used. The quantitative content of the binder is determined depending on the solids content in the mixture to ensure the formability of the mass.

In the process of refractory firing, the interaction of periclase and magnesia-silicate components occurs until the formation of the main phases: periclase and forsterite. The presence of the magnesia-silicate component in the dispersed component ensures the formation of a forsterite bond located in the form of films between periclase grains with the formation of a network of interconnected curved microchannel pores, resulting in the formation of a microcrack structure evenly distributed in the refractory volume. The forsterite matrix obtained during the firing process has better chemical resistance, since forsterite is inert to most corrosive materials; during refractory service, forsterite also increases the abrasion resistance of the refractory due to its high hardness (on the Maoss scale 7).

In the case of the presence of zirconium silicate in the dispersed component during firing, the zirconium silicate ZrSiO ₄ decomposes into baddeleyite (ZrO ₂ ) and silicon oxide SiO ₂ , the latter, in turn, interacting with periclase forms forsterite and solid solutions Mg ₂ Zr ₃ O ₈ .

The following shows a specific embodiment of the invention, not excluding other options (examples) within the scope of the claims. The compositions of the charges for the manufacture of refractories with forsterite bonding and the properties of refractories are shown in table 1.

Example 1

The dispersed component of the mixture is prepared by joint or separate grinding, to a fraction of 0.063-0 mm, in a periclase vibro-mill with a mass fraction of MgO> 97% and olivine. Dispersed mixture in an amount of 25%. The granular component is represented by densely sintered periclase with 95% MgO in an amount of 55% and olivine in an amount of 20%. The granular and dispersed components of the mixture are mixed in the mixer when moistened with a temporary binder, in excess of 100% - 4% LST. Products are pressed from the wetted mass in a hydraulic press at a specific pressure of 130 N / mm ² . The raw material is dried, then fired in an oven at a temperature of over 1600 ° C. For fired products, resistance to Portland cement clinker, resistance to aggressive reagents of raw mixes (glass-alkali resistance), open porosity, compressive strength, temperature at which deformation began under load, heat resistance, additional linear shrinkage, etc. were determined.

In the same way, refractories were prepared according to the composition of the mixtures 2-16.

Forsterite bonded refractories made in accordance with the present invention are characterized by a thermoplastic structure that is resistant to cyclic thermal and corrosive effects of aggressive components in the service.

Table 1 Name of materials Charge 1 Charge 2 Charge 3 Charge 4 Charge 5 Fir 6 Fir 7 Charge 8 Fir 9 Charge 10 Charge 11 Charge 12 Charge 13 Charge 14 Charge 15 Charge 16 Granular periclase with a mass fraction of MgO 93-97%: densely sintered 55 - 55 55 55 63 - 63 67 67 67 67 - - 70 70 Fused - fifty - - - - 60 - - - - - 70 80 - - Granular magnesia-silicate component: Olivine twenty thirty - twenty - 10 5 - 8 - 8 - - 5 10 10 Fused forsterite - - - - - - - - - - - - 5 - - - Dunite - - twenty - twenty - - 10 - 8 - 8 - - - - dispersed component from the mixture: periclase with MgO> 97%, olivine and zirconium silicate - - - - - 27 35 27 - - - - 25 - - - periclase with MgO> 97% and dunite - - - 25 25 - - - - - 25 25 - - - - periclase with MgO> 97% and olivine 25 twenty 25 - - - - - 25 25 - - - fifteen twenty twenty Additive, over 100% - Badeleit - - - - - - - - - - - - one - 6 - Rutile concentrate - - - - - - - - - - - - - 2 - 3 Binder, in excess of 100% four 3,5 four four four four 4,5 four 5 3,5 four four 4,5 5 4,5 3,5 Indicators The limit of compressive strength, N / mm ² 55 80 55 55 fifty 110 130 one hundred 55 fifty 60 55 120 110 60 55 Open porosity,% eighteen 16 eighteen 19 19 10 8 12 fifteen 16 15.5 16 13 fourteen 16 17 Softening start temperature, ° C 1650 1680 1620 1630 1600 1600 1700 1580 1630 1620 1620 1600 1700 1700 1680 1650 Thermal resistance when cooled by compressed air (950 ° C - air) > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 > 30 Additional linear shrinkage,% -0.1 -0.1 -0.1 -0.1 -0.1 0.0 0.0 0.0 -0.1 0.0 -0.1 -0.1 -0.1 0.0 -0.1 0.0

Claims (3)

1. The mixture for the manufacture of refractories with forsterite bonding, including granular periclase, dispersed periclase, granular magnesia-silicate component, dispersed magnesia-silicate component and a binder, characterized in that as granular periclase contains dense-periclase with a density of at least 3.30 g / cm ³ and / or fused periclase, and the dispersed component of the charge is a mixture of periclase with a mass fraction of MgO> 97% and magnesia-silicate component and / or zirconium silicate in the following ratio, m ac%:
granular periclase with a mass fraction of MgO 93-97% 50-80 granular magnesia-silicate component 5-30 dispersed component from a mixture of periclase with MgO> 97% and magnesia-silicate component and / or zirconium silicate 15-35 binder, in excess of 100% 3,5-5 2. The mixture for the manufacture of refractory with forsterite bond according to claim 1, characterized in that the dispersed component further comprises zirconia ZrO ₂ in an amount of 1-6%. 3. The mixture for the manufacture of refractory with forsterite bond according to claim 1, characterized in that the dispersed component further comprises titanium dioxide TiO ₂ in an amount of 1-6%.