LT4286B - Production of a siliceous refractory mass - Google Patents

Abstract

The invention is a method for producing an incombustible crystal mass of silicate, which has cristobalite, it directs hard incombustible particles, hard particles of silicon and gassy oxygen to the surface so that the heat, relieved in reaction between the particles of silicon and the gassy oxygen forms a incombustible coherent mass containing cristobalite. The hard incombustible particles contain silicon dioxide in the form of transparent glass; the surface to which they are directed must be heated to at least 1,000 degrees Celsius. This method can be used for repairs where the temperatures are very high, such as a furnace for producing glass and high quality incombustible bricks.

Description

The present invention relates to a process for the production of crystalline silicate refractory mass containing cristobalite. This method can be adapted to produce mass from which refractory building furnace bricks or blocks are made, or rebuilt in situ, i.e. the presence of silicate refractory surfaces on industrial furnaces such as glass furnaces.

The refractory mass production process uses "ceramic welding" technology, whereby a mixture of solid refractory particles and solid flammable metal or semiconductor fuel particles, such as aluminum and silicon, is applied to the restoring surface and then exposed to oxygen-saturated gas, preferably - pure oxygen, and the surface heat of the fuel released forms a new, coherent refractory mass.

Such "ceramic welding" is described in GB 1 330 894 and GB 2 170 191. A coherent refractory mass is formed on the surface by coating the latter with a mixture of refractory and flammable particles in an oxygen environment. Flammable particles are particles whose chemical composition and granulometry are such that they exothermically react with oxygen to form a refractory oxide while releasing the necessary heat to melt at least the refractory particles on the surface. The surface is properly and safely coated with particles using oxygen as the carrier for the particles. The particle-coated surface thus forms a coherent refractory mass.

These known ceramic welding techniques may be used in the manufacture of refractory products such as blocks of certain shapes, but they are most widely used in the formation of coatings or in the reconstruction of bricks or walls, and are particularly useful in rebuilding or reinforcing existing structures such as glass furnaces. or blast furnace walls.

This method is particularly suitable for the rebuilding of a hot sublayer surface. It is possible to repair worn surfaces without changing the operating temperature of the unit, and often without stopping the furnace. Such an opportunity to reconstruct a functioning furnace is particularly useful in glass making and blast furnaces, as the design life of the furnace is measured in years, usually up to 20 years. All this time, the furnace operates continuously.

The composition of the ceramic welding compound was chosen to give a restorative mass having a chemical composition similar to that of the main refractory layer. This ensures that the new material is compatible with the underlying material on which it is formed and provides a reliable bond between them.

However, even with a similar chemical composition, there may be problems with the reliable bonding of the recovery mass to the sublayer. The problem becomes even more acute if the restored surface is exposed to very high temperatures, such as a glass tank vault. In this case a high level of refractory material is required.

Do not split the repair mass. In the glass manufacturing industry, a broken piece of pulp may fall into the molten glass and form an unwanted impurity that may require a change in the full charge of the molten glass.

It has been found that cristobalite-containing highly refractory masses of solid refractory macroparticulate material, which has traditionally been considered incompatible with the substrate, can be readily formed. This material, which according to the present invention can now be successfully used for reconstruction, is clear glass.

The present invention relates to a process for producing a crystalline silicate refractory mass by directing gaseous oxygen, solid refractory particles and solid combustible particles containing silicon particles to a surface such that a reaction between the flammable particles and the gaseous oxygen occurs to release and thereby heat the surface. forming a coherent refractory mass containing crystobalite, characterized in that the solid refractory particles contain silica in the form of clear glass and that the target surface is heated to a temperature of at least 1000 ° C.

Due to the high surface temperature, the silicon formed during the combustion of the silica particles is embedded in a crystalline lattice in the refractory mass.

The crystal lattice improves the internal adhesion of the refractory mass and its ability to adhere to the restoring surface. All of these explanations are purely hypothetical, but the advantages of the invention are obvious in practice.

The crystalline lattice is believed to act as a binder for the refractory mass. The grid compactes and binds the mass structure with high mechanical strength. If the process is used to rebuild a worn refractory surface, the crystal lattice covers and adheres to the surface.

The structure of refractory particles covering the restorable surface may differ from the binder phase. The adhesion to the surface is ensured by the binder phase.

The refractory mass, which is exposed to the high temperature of the furnace itself, is transformed into cristobalite. In the case of a single refractory brick or block, the formed refractory mass shall be fired at a temperature of at least 1000 ° C by pouring the mass from the workpiece. High furnace temperatures and scorching transform the residual glass phase into cristobalite.

The method described in the present invention is particularly suitable for in situ repair of glass-making furnaces, i.e. because they always have very high temperatures. For example, the surface temperature of the vault above the glass melt tank may be higher than 1500 ° C.

A mixture of particles consisting of solid flammable particles and solid refractory particles having clear glass can be used for surface restoration at temperatures below 1000 ° C provided that the mixture contains the additive mentioned in GB 2 257 136.

The silica used in the present invention must be highly pure, having a purity (by weight) of at least 95%, preferably 99% pure oxide. The resulting mass is extremely flame-retardant and reduces the risk of contamination of the glass production tank should any part of the mass fall into the glass.

Transparent glass used in this process is a semi-solid refractory material and is therefore preferred. that it is readily available and that its degree of purity can be very high.

Preferably, the total silicon content by weight does not exceed 15%. This limits the amount of unreacted fuel in the formed refractory mass, since a higher proportion of unreacted fuel in the formed refractory mass may impair its quality.

Preferably, the size of the refractory particles does not exceed 4 mm, more preferably 2.5 mm. It is then easier to coat the surface evenly with powder. It is also desirable for the refractory particles to have a particle size distribution f (G) of not less than 1.2. This coefficient f (G) depends on the type of particle and is expressed by the formula:

2 (Gso - G? O) f (G) = ...............>

(Gso + G? O) where Ggo expresses a grain size of 80% for that species and G20 represents a grain size of 20%.

The average diameter of the silicon particles should preferably not exceed 50 µm. The term "average particle diameter" means that 50% of the particles have a size smaller than this average.

The melting point of the mass obtained according to the invention approaches the melting point of pure silica. The bricks produced according to the present invention have a cristobalite structure and a deformation coefficient T0.5 of ISO R1893 greater than 1650 ° C. This equates to T0.5 of ordinary silica bricks manufactured in the conventional manner, which reaches about 1550 ^u C. Refractory bricks consisting mainly of a stabilized, highly crystallized solid solution (ie silica in which Si is replaced by Al with Ca or Ca plus others) cations) prepared by recrystallization of glass according to U.S. Patent 4,073,655 are suitable for use at temperatures up to 1250 ° C.

The invention is further illustrated by several examples. It should be noted, however, that the invention is not limited to the specific amounts and procedures described therein.

An example

A mixture of 88% (by weight) of 88% clear glass particles containing 99.7% pure silica and 12% silica particles was subjected to a stream of pure technical oxygen into the vault of the glass production tank to form a refractory mass on its surface. The temperature of the vault was about 16 () 0 ° C. The maximum clear glass particle size was 2 mm. It had a G 50 of 950 µm and a G? D of 225 µm, resulting in a particle size distribution f (G) of 1.23.

The silicon particles had an average diameter of less than 45 µm and a comparative surface area between 2500 and 8000 cm ² / g. After six days, the specimen was removed for analysis, which revealed the following properties:

Melting point 1723 ° C

Structure Cristobalite

To.5 (ISO R1893) nearly 1700 ° C * * T0.5 for most widely used industrial bricks (refractory HEPSEL S V High Pure Silica) is approximately 1640 ° C.

An example

A mixture of powders having the same composition as in Example 1 was directed into the workpiece in a stream of pure pure oxygen to form a brick. The workpiece was preheated to 1600 ° C. Once formed, the brick was maintained at 1450 ^u C for 6 days. The brick was then analyzed and found to have a melting point, a structure and T0.5 consistent with the data obtained from the analysis of the sample mentioned in Example 1.

Bricks made in accordance with Example 2 can be used without prior precautions to rebuild a worn glass furnace vault if additional welding is required. Any other type of crystalline silica brick placed under similar conditions without precautionary measures such as careful preheating will decay.

Claims (9)

DEFINITION OF INVENTION CLAIMS 1. A method of producing a crystalline silicate refractory mass comprising the step of surface-contacting gaseous oxygen, solid refractory particles, and solid combustible particles containing silicon, by reacting between the flammable particles and gaseous oxygen on a surface to form a coherent refractory characterized by the addition of silica in the form of clear glass to the surface of the crystalline material containing crystallite, and directing it to a surface at a temperature of at least 1000 ° C. 2. A method according to claim 1, characterized in that it burns a refractory mass formed on the surface at a temperature of at least 1000 ° C. 3. A process according to claim 1 or 2, characterized in that the refractory particles add silica having a purity of at least 95% by weight. 4. A process according to any one of the preceding claims, characterized in that silica with a purity of at least 99% by weight is added to the solid refractory particles. 5. A method as claimed in any preceding claim, wherein the total silica content is determined to be at least 15% by weight of the total particles directed to the surface. 6. A process according to any one of the preceding claims, wherein the silica particles are selected such that the average silica particle size is not greater than 50 µm. 7. A process according to any one of the preceding claims, wherein solid refractory particles are used which do not contain particles larger than 4 mm. 8. A process according to any one of the preceding claims, characterized in that the refractory particles have a particle size distribution f (G) of at least 1.2. 9. A refractory brick having a cristobalite structure, characterized in that it has a deformation factor To, greater than 1650 ° C, and is produced by the methods listed in claims 2-8.