RU1806119C - Composition for manufacturing laminated refractory material with heat-insulating layer for revolving furnace lining - Google Patents

Abstract

Use: production of multilayer heat-insulating products combining lining and thermal insulation, including for lining of rotary kilns. SUBSTANCE: composition for producing a heat-insulating layer includes: alumina May 25-48%, coke May 15-52%, clay 10-20 mass%, silica sand 8-15 mass%, boric acid 2-5 mass%. % In preparing the composition, alumina, coke and quartz sand are mixed for 15 minutes, then the mixture is moistened with a clay slip based on a solution of sulphite-alcohol stillage (PRS) with boric acid previously dissolved in it and mixed again for 5-10 minutes. After firing at 1400-1450 ° C, the product from the claimed composition is characterized by a thermal conductivity coefficient at 600 ° C of 0.14-0.31 W / m: .k. 1 tab.

Description

The invention relates to the production of multilayer thermal insulation products combining lining and thermal insulation and used in high-temperature firing units, including for lining rotary kilns for firing cement clinker, dolomite, alumina.

The purpose of the invention is to reduce the thermal conductivity of products.

The goal is achieved in that the composition for the production of a heat-insulating layer of a two-layer refractory, including earth, coke, clay, silica sand, additionally contains boric acid in the following ratio of components, wt.%:

alumina 25-48 coke 15-52

clay. 10-20

quartz sand8-15

boric acid 2-5

The claimed technical solution differs from the prototype in that the composition is supplemented by a ° pumo containing boric acid. When the charge is heated, boric acid is converted into metabolic acid, which partially transforms into a gas form, which has a beneficial effect on the reactions in the powder mixture. In this case, a chemisorption phenomenon occurs in which the concentration of electronic and ionic defects in crystals can increase significantly, i.e. there are real prerequisites for increasing the rate of diffusion of ions in the powder mixture and, consequently, the rate of decomposition of kaolinite and the formation of

new phases, in this case mullite. This allows products containing up to 98% of this phase to be obtained.

The higher thermal conductivity of the prototype is associated with a high content (in comparison with the proposed solution) of corundum in the product, whose thermal conductivity is much higher than mullite (9.4 and 3.0 W / m K at 600 ° C, respectively).

An example of a specific implementation.

As a dense part of the two-layer heat-insulating refractory, the standard MK-BO mass was used for the ShchTsU (GOST 891-73) product, which includes chamotte and a clay component.

The mass for the insulating layer is prepared as follows: after preliminary preparation, including crushing and drying, the initial components: alumina, coke, quartz sand are loaded into a Z-shaped mixer and mixed for 15 minutes. Then, the mixture is moistened with clay glycer based on a solution of sulphite-alcohol stillage (PRS) with boric acid pre-dissolved in it and is mixed for 5-10 minutes.

The compositions are loaded into the mold when the corrugated partition is installed at the rate of 1/3 in length - the mass of the lightweight part, and 2/3 - the mass of MK-65. The compression pressure is 30-50 MPa. After drying, the product is fired at a temperature of 1400-1450 ° C.

The composition of the charge and physico-mechanical properties of the products are shown in the table.

For the basis of the comparative characteristics, the characteristics of the samples with a p - 0.93-1.0 g / cm are taken. The thermal conductivity of the ShTsU-22 two-layer refractory, taking into account the lightweight layer corresponding to the proposed composition, analog, prototype, and base variant, was calculated by the formula

11 + 12

Ј

And 12

X + Ј

0

where a. - total thermal conductivity of a two-layer refractory,

And - the thickness of the dense layer,

2 - the thickness of the lightweight layer,

AI - thermal conductivity of the dense part,

Xg thermal conductivity of the lightweight part

The results obtained indicate that in the case of obtaining a two-layer

5

the refractory using the proposed composition, its thermal conductivity is reduced by almost 2 times compared with the analogue, by 1.5 times with the prototype, and by more than 2 times with the basic version.

Preliminary values of the charge components are justified by compositions corresponding to the stoichiometric composition of mullite (-25102). The upper limit of boric acid content (5%) is related to its solubility in water at T 40-50 ° C. The lower limit of the content of boric acid is due to the fact that its content of less than 2% does not give the desired effect

5 mullitization. .With a content of more than 50% coke chips, the products are characterized by low mechanical strength (composition, 5 MPa), and with a content of less than 15%, a significant increase in apparent density occurs, which leads to higher.

0

thermal conductivity (composition 6).

SUMMARY OF THE INVENTION A composition for producing a thermal insulating layer of a two-layer refractory for rotary kilns, including alumina, coke, clay, silica sand and an additive, with a view to reducing the coefficient of thermal conductivity, as an additive, it contains boric acid in the following ratio of components, wt.%:

Alumina 25-48 Coke. % 15-52 Clay 10-20 Quartz sand 8-15 Boric acid 2-5