RU1128537C - Refracory mass for manufacturing heat-insulating articles - Google Patents

Description

The invention relates to the field; production of refractories, namely Kg, compositions for the manufacture of shaped refractories used for lining thermal units with a hydrogen-containing medium and a service temperature above 1700 ° C

A known refractory mass for the manufacture of heat-insulating lightweight products, including hollow corundum spheres 64-76 mАСо distene-sillimanite finely ground 6 12 mАСО% and binder aluminophosphate 18-24 mА:

The disadvantage of this mass is the possibility of achieving a low density and thermal conductivity obtained from the refractories obtained from it, with a significant reduction in their strength (density I 1.43 g / cm, thermal conductivity at t Cd} 11.15 W / mK).

Xj

i In addition, the content in mass. distensillimanite and aluminum phosphate: a binder. When heat treated, it leads to the formation of mullite and

Pgos

With SL5 oxy in hydrogen-containing

Silicon oxides decompose before milling at temperatures above 1 ° C. Mullite;

and evaporate. Products lose weight, loosen and break.

The closest to the claimed technical essence and the achieved effect is the mass composition for the manufacture of porous refractories based on hollow corundum spheres containing hollow corundum spheres with granule sizes, mm;

3-210-50

2-120-25

1-0,520-30

0.5 20

and vibro-ground alumina G-0, calcined at 1750 ° С, 20-30 “

Refractories with a sufficiently high strength can be obtained from this mass. Their disadvantage is the high density (1.7 b, 97 g / cm) and thermal conductivity (1.82; 0 W / Mk at t).

To increase the density and. Heat. In this case, the conductivity of refractories results from the use of moistened СХ-А 2.0-5 (in the form of vibro-ground alumina) as a binder of hollow spheres

This mass is not plastic, since the components of the mass do not have sufficient mobility and adhesive ability, therefore, it is possible to make products from it only by semi-dry pressing or tamping, however, in the manufacture of products by such methods, partial destruction of hollow spheres occurs, which also leads to an increase in density and thermal conductivity of the product In addition, semi-dry pressing and tamping limit the possibility of manufacturing products of complex shapes

The aim of the invention is to reduce the density and thermal conductivity of insulating products while maintaining their strength.

This goal is achieved due to the fact that the refractory mass for the manufacture of heat-insulating products, including hollow corundum spheres and an aluminum-alumina binder, additionally contains granular corundum and, as a binder, an aqueous suspension from a mixture of finely divided Oi-Al Oj,, A1 ( OH) and hydrochloric acid in the following ratio of components, wtD:

Hollow corundum spheres 32-50

Fine Suspensions: 12-2

Jf-Al2f 36th

AKON), 2-6

Distilled water P, 2-1.0 Salt per acid 0.8-1.0 Granular corundum 3-32

The essence of this technical solution is as follows

The use of corundum in the form of hollow spheres in combination with granular corundum and a complex ceramic binder provides products with a low density of 1.25-1.61 g / cm3 and a thermal conductivity of 0.98-1.5 W / (mK) at 1350 C with a relatively high strength of products up to 29.0 MPa

In a suspension of aluminum-containing components, including aluminum hydroxides, when the content of hydrochloric acid is formed, aluminum oxychlorides are formed in an amount of up to 3-5, which exhibit enhanced adhesive and hardening properties. As a result, when vibroforming. Masses in gypsum forms, on hollow spheres and granular corundum forms a film of active alumina, which binds the mass into a stable monolith, providing it with strength both in the raw material and after firing, which is ocofeeH But it is important in the manufacture of products of complex shapes,

In suspension of finely dispersed

components containing technical alumina - aluminum hydroxide A1 (OH) 1, taken in the specified ratio, due to decomposition of aluminum hydroxide and polymorphic transformations upon transition to the heat treatment of the mass, a finely porous binder structure with a pore size of 50-3000 A

The finely porous binder structure provides products with low density and thermal conductivity.

The content in the mass of granular corundum and fine alumina in the form of-Al OJ in the stated proportions provide the proposed mass with strength

The properties of products from the proposed mass can be varied within specified limits due to a change in the grain composition of the filler, content of fused or sintered granular corundum, and a change in the ratio of components in the ceramic binder (suspension) os-A1, 0.-J y-Al, jO and. A1 (OH) With a decrease in the grain size of the filler and with an increase in the content of C-AljOj in the ceramic suspension, the strength increases, but at the same time, the charge and thermal conductivity of the mass increase. The decrease in density and thermal conductivity at a relatively high strength is ensured by the mass of the y-AljO and A1 (OH) components, which enter the ceramic binder within specified limits due to the formation of active aluminum oxychlorides and a finely porous structure, which binds. The increase in the content of granular corundum in the mass is more than 32 wt. %% Leads to a further increase in density (1.7 g / cm) and thermal conductivity, which cannot be compensated by the introduction of γ-A1.2.3 and A1 (OH). When the coruidas 3 grain content is contained, the refractories are weak (10 MPA), which does not allow them to be used at high temperatures, and an increase in the content in the suspension for hardening leads to high thermal conductivities. “The best formability of the masses during vibroforming in gypsum molds was obtained with a filler ratio of 53 to 64 wtD and binder from 7 to 3 wt% with its density from 1.9 to 2.0 g / cm3. “The presence of aluminum-containing components in the mass ensures volume stability in a hydrogen medium at temperatures above and low Is Capacity Example A mixture of aluminum-containing components (technical alumina of 2k masCO%, for example, grade GN-1, industrial grade alumina grade G-00 6 wtD and alumina hydrate 2 wt.%, For example grade GD-O or GD-1) is ground in a vibrating mill to a size particles less than 5 µmo. Then, the powder is closed with distilled water in May about 376 and hydrochloric acid 1 ml. (density 1.17 g / cm), adjust the suspension to a density of 1.9-2.0 g / cm and the pH of the solution pH. The components of the filler are hollow corundum spheres of 50 wt, made by known technology, with a grain size of 5-0 mm and granular corundum (3 wt.%) with a grain size of 3-0 mm (electrocorundum produced by industry, sintered corundum obtained by crushing sintered briquettes made from alumina, for example, grade GN-1) are pre-mixed with each other, then the suspension is volled, mixed and filled plaster molds with continuous vibration on a vibroinstallation (vibrator vibration frequency 280 Oscillations per 1 min, amplitude 0.1 mm) o Products are kept in gypsum molds for 2-3 days, at a temperature not higher Then the molds are disassembled and products burned at 1700Со: The table shows the mass compositions performed according to the invention, and the properties of products from these compositions in; compared with the properties of products obtained from known mass compositions. As can be seen from the table, the products obtained according to the invention are characterized by lower values of density and thermal conductivity compared with the same properties of products obtained by the prototype. The products obtained are characterized by sufficiently high strength . For compositions 6 and 7, the bending strength at a temperature of 1.2 MPa, and at 0.22 MPa, which guarantees the reliability of products in service at a temperature of. There is practically no additional shrinkage and evaporation at temperatures of 1700-1800 0 V hydrogen environment Thus, from the proposed mass, it is possible to prepare by vibration molding thermal insulation products of a complex style with sufficient mechanical strength