DE4221480C2 - Method and mixture for forming a coherent refractory mass on a surface - Google Patents

Description

The invention relates to a method for forming a contiguous refractory mass on a surface, in which against this surface simultaneously with oxygen a mixture of refractory particles and combustible part Chen is thrown with in an exothermic manner the spun off oxygen by releasing enough heat to form the aforementioned refractory Mass react under the effect of the heat of combustion. The invention also relates to a particle mixture which for a method of forming a coherent Refractory mass on a surface is determined by the mixture and oxygen thrown against the surface be changed, the mixture of refractory particles and Contains particles of a combustible substance which are used for exothermic reaction with oxygen to release enough heat is suitable to be under the effect of Combustion heat the aforementioned refractory mass too to form.

If you put a refractory mass in situ on a surface want to shape, you can choose between two known principles Select the procedure.

According to the first of these methods, sometimes as so-called tes "ceramic welding" named in the British Patent 1,330,894 (Glaverbel) and the British patent 2 170 191 is explained, is a contiguous Refractory mass on a surface by spinning a mixture of refractory particles and combustible Particles in the presence of oxygen on the Shaped surface. The combustible particles are  Particles, their composition and granulometry such are that they are in an exothermic way with the oxygen during the formation of a refractory oxide and during the Release of the necessary heat to melt, little very superficial, the flung refractory Particles react. Aluminum and silicon are examples for such combustible substances. It is known that Silicon is strictly classified as a semi-metal must be, but since silicon, like certain metals, itself behaves (it is capable of considerable exothermic oxidation during the formation of a refractory oxide to go through), these combustible elements are considered so-called combustible metallic substances Denoted for simplicity. In general it will recommended spinning the particles in the present a high oxygen concentration, e.g. B. by use of oxygen with commercial quality as one Gas carrier to perform. In this way, one coherent refractory mass formed on the Surface onto which the particles are thrown attached. Because of the very high temperatures that the ceramic weld reaction, it can Penetrate slag on the surface of the Refractory substance that is being treated may be present can, and it can soften the surface or melt that good connection between the treated surface and the newly shaped refractory Mass is produced.

These known ceramic welding processes can be used Forming a refractory object, e.g. B. a block, be used with a special look but they become very much for the formation of coatings or for Repair of bricks or walls are used and they are particularly useful for repairing or reinforcing  existing refractory structures, e.g. B. to repair Walls or coatings for refractory facilities, such as Melting furnace walls in glass production or coke ovens.

This procedure is generally carried out when the refractory support is hot. This enables to repair gnawed refractory surfaces while the facility essentially at its operating temperature ratur remains and, in certain cases, even during of their business.

The second known process for forming a refractory Mass on a surface is the so-called "flame spraying method ". It involves directing a flame the place where a refractory mass is to be formed and Spraying refractory powder across this flame. The flame is caused by a gaseous fuel or a liquid or even fed by coke powder. It it is obvious that the efficient use of this Flame spray technology a complete combustion of the Fuel presupposes the hottest flame that is possible to generate and to maximize efficiency achieve. Generally the one with the flame spray method obtained flame temperature not so hot like the one achieved with ceramic welding technology with the result that the coherence or the Connection of the shaped refractory mass not so good and since the connection between the new refractory Mass and the surface of the refractory support at one low temperature, this is Connection not so permanent. Moreover, it is one Flame less than a ceramic weld reaction to penetrate the slag on the Refractory surface to be treated exists can be.  

The composition of the mixture in a kera mixing welding process is used is common selected in the way to produce a repair mass represent a chemical composition similar or close to that of the refractory beam. This helps at, the compatibility and adhesion with the new Material and the support on which it is molded to deliver.

DE 36 29 886 relates to a method for forming a refractory mass on a Surface, such a method being used to make refractory coatings to form on refractory blocks or other surfaces, and the process is used in particular for repairing or reinforcing furnace linings in used in situ, with the application in some cases with full furnace operation can be done.

DE 38 42 252 describes a method for treating a refractory structure tur, and a particulate composition for use in one such procedures. The treatment procedure can be used to simply remove parts of a refractory structure. The particulate zu In contrast to the present invention, composition contains in addition to Refractory particles and fuel particles are a flux that causes under the heat released by the combustion of the fuel particles treated refractory structure is softened to such an extent that material the refractory structure due to the mechanical action of the impact Particle stream is removed or added. As a flux, borates, sulfa te, carbonates and phosphates, such as calcium carbonate or magnesium carbonate, be used.

However, problems have been found to occur when it is desirable to have certain types of refractory structures to repair and even if a refractory mass a chemical composition is formed that is similar which is the carrier refractory mass.

For example, repairing refractory waists surface structures with a silicon carbide carrier with the Using a mixture that is primarily carbon Silicon particles and also particles of metallic contains combustible substances, such as aluminum and Silicon particles, a refractory mass that is not always shows sufficient adhesion to the refractory support.

Refractory materials with a carrier made of silicon carbide are used in certain metallurgical facilities, ins especially in blast furnaces in the iron industry or in Zinc distillation columns used. During operation certain parts of the refractory Structures a fairly low, minimal operating temperature, e.g. B. in the order of 700 ° C, and they can also be significant Fluctuations in the ambient temperature. It it has been observed that by known techniques manufactured refractory masses on these parts of the Refractory structures are not always sufficient adhesion  show on the refractory carrier mass, and in certain Cases, especially when repairing a block or carried out on a refractory wall, the Temperature is low, the new refractory mass dissolves completely from the carrier refractory mass and dissolves even while the facility is operating.

Similar problems appear when you refractory Structures with a high density silicon dioxide carrier (so designated to separate them from traditional silica Distinguish refractory masses whose density is lower is) wants to repair that in certain coke ovens be used; even if you use a refractory material Similar chemical composition compared to that Can form carrier refractory mass, the new mass adheres not always enough and can even quickly change from detach the carrier refractory mass when the furnace is in Operation is.

From the international patent application WO 90/03848 (Willmet / Willard) is a process for repairing e.g. B. furnace linings known in which an inert gas carrier and refractory oxide particles and combustible oxidizable material fed to a flame sprayer with high pressure sucking in oxygen and the Carrier gas / particle mixture accelerated. Willart turns this procedure on the repair of refractory Blocks / bricks in the blow molding line of a copper melt converter as well as in the repair of silicon car bi-column trays. For example, you throw one Mixture of 79% silicon carbide, 16.25% silicon dioxide, 4% aluminum and 0.75% magnesium through a double Venturi air-oxygen system on a silicon carbide Column tray. In the examples there is a joint use of Silicon and silicon carbide not described.  

However, the use of magnesium metal powder is in disadvantageous to this method, at least in that Magnesium metal is relatively volatile; there is a measure of uncertainty about the composition of the molded Refractory cover.

The object of the invention is therefore the aforementioned Solve problems and the disadvantages of the state of the art Avoid technology.

This object is achieved by the kenn Drawing features of claims 1 and 4 solved.

The sub-claims contain advantageous execution form the invention.

The invention therefore relates to a method for molding a coherent refractory mass on one Surface based on a silicon compound, in which against the surface simultaneously with oxygen Mixture of refractory particles and combustible particles is thrown in an exothermic manner with the centrifuged oxygen by releasing enough Heat to form the refractory mass under the effect the heat of combustion react, taking the mixture contains: (i) combustible silicon particles; (ii) fire solid particles, selected from silicon dioxide and silicon carbide, as a major part by weight of the mixture; and (iiia) additional Liche particles of another substance that during the Forming the refractory mass incorporating silicon dioxide formed by burning the silicon particles into a crystalline lattice and / or (iiib) additional particles of a non-metallic compound, the other during the formation of the refractory mass That produces the incorporation of the  Combustion of Silicon Particles Shaped Silicon Dioxide into a crystalline lattice.

The invention also relates to particle mixtures intended for a method for forming a coherent refractory mass on a surface based on a silicon compound, in which the mixture and oxygen are thrown against this surface, the mixture refractory particles and combustible particles contains, which are capable of exothermic reaction with oxygen to release enough heat to form this refractory mass under the action of the heat of combustion, which is characterized in that the mixture contains: (i) combustible silicon particles;
(ii) silicon carbide as a refractory particle as the main weight fraction of the mixture; and
(iiia) additional particles of another substance which, during the formation of the refractory mass, brings about the incorporation of silicon dioxide, which is formed by combustion of the silicon particles, into a crystalline lattice, and / or (iiib) additional particles of a non-metallic compound which, during the formation of the refractory mass, produces this other substance, which brings about the incorporation of silicon dioxide, which is formed by the combustion of the silicon particle, into a crystalline lattice.

Such a mixture and such a method are useful for forming refractory masses with high Quality for the repair of surfaces based on a Silicon compound, such as. B. refractory structures from Furnaces, as well as for welding fragments together. It is possible to get a refractory mass that a excellent adhesion to the carrier refractory material shows if the repaired surface repeated  Changes in thermal conditions during the Operation of the facility is suspended and / or if the Repair is carried out on a surface whose Temperature is relatively low, like between 600 ° C and 1000 ° C (e.g. 700 ° C), although the invention on surfaces applicable with a temperature outside this range is.

The masses produced according to the invention show thermal expansion properties at the interface between the surfaces and the molded refractory Masses that are different from those that one could get if the starting mixture was not any Contained substance that the incorporation of Silicon dioxide caused by the burning of silicon is formed into a crystalline lattice. It will assumed that those achieved by the invention Advantages at least in part on this difference in the Interface are attributable and that the preserved Refractory-mass thermal expansion properties to show the interfaces that closely match those of the in Question refractory structures are adapted.

The combustible silicon particles (i) can be used as that sole combustible material can be used or they can with particles of another combustible mate rials such as aluminum. So that contains Mixture preferably continues to burn aluminum particles. Aluminum particles can quickly with a significant heat release and they are oxidized form refractory oxides themselves. The application of this essential feature thus favors the formation of Refractory masses with high quality.  

The mixtures according to the invention preferably contain not more than 15% by weight silicon. This is important for Limiting the amount of unreacted silicon that is in the shaped refractory mass remains. It was found that the presence of unreacted Procure silicon in the shaped refractory mass can affect it.

The refractory particles (ii) can be present in an amount of at least 70% by weight, preferably at least 75 wt .-%, be present to a homogeneous mass receive.

Make the additional particles (iiia) and / or (iiib) preferably the rest of the mixture and can be up to 25% by weight in the mixture, preferably from 5 to 15% by weight, be included.

The combustible particles used in the mixture (i) preferably have an average particle size of less than 50 µm.

The refractory particles (ii) preferably contain in essentially no particles larger than 4 mm, particularly preferably not larger than 2.5 mm, around the To facilitate the formation of a regular powder jet.

The additional particles (iiia) and / or (iiib), which in used in the mixture preferably have one Particle size less than or equal to 500 µm. If Particles that are too large are used Risk that they don't play an effective role. Preferred two These particles have a size of at least 10 µm. If particles that are too small are used a risk that they evaporate during the reaction.  

Different substances are during the formation of the Refractory mass for induction of incorporation in the Burning Silicon Shaped Silica into One suitable crystalline lattice.

The aforementioned additional substance (iiia) which the Incorporation of silicon dioxide by combustion is formed by silicon into a crystalline lattice is preferably introduced into the mixture in the form of Magnesium oxide particles introduced.

The presence of this compound in the mixture that hurled onto the refractory surface to be repaired will help ensure the correct fire resistance properties of the molded refractory mass are ensured.

Furthermore, the introduction of magnesium oxide into the Mix the formation of a refractory mass at which a Part of that formed by the burning of the silicon Silicon dioxide in a crystalline forestry type lattice is installed. This also helps the correct fire resistance properties of the molded Ensure refractory mass.

If the mixture contains both aluminum and magnesium oxide contains a refractory mass in which part of at least that from the combustion of silicon shaped silica into a crystalline lattice of the Forsterite structure and / or in a crystalline lattice Spinel structure and / or in a crystalline lattice Cordierite structure is incorporated.

The presence of a crystalline lattice Cordierite structure in the molded refractory mass bears  contribute to excellent resistance to thermi shocks of this mass. The presence a crystalline lattice of the forsterite structure and / or Spinel structure on the other hand influenced in preferably the heat resistance of the molded Refractory mass.

Other oxides, such as calcium oxide or iron (II) oxide, can can also be used as the additional substance (iiia), which the incorporation of by burning Silicon shaped silicon oxide in a crystalline lattice causes.

A mixture of particles can be used in addition or alternatively an additional substance or substances (iiib) contains whose composition is such when the Refractory mass is molded to be a substance brings about the incorporation of through the Burning Silicon Shaped Silica into One crystalline lattice. For example, peroxides, such as calcium peroxide, nitrides, carbides.

An oxide, e.g. B. calcium oxide, can be in the form of a compound, e.g. B. in the case of calcium oxide, in the form of wollastonite (CaO. SiO ₂ ).

The invention is particularly useful for the repair of Refractory materials with a silicon carbide carrier or Refractory materials with a high density silicon dioxide carrier. In a consistent way it will ceramic welding with the help of a Mixture performed, the main part by weight Silicon carbide or silicon dioxide.  

It goes without saying that the invention is also for the repair of other types of refractories is useful on a silicon compound, like the ones mentioned before, like normal silicon dioxide brick and silica-alumina brick, based.

The substance or substances that make up the main part by weight the mixture can make up with the composition of the Refractory product to be repaired correspond, or they can come from a different substance. In the latter case shaped a refractory mass that have properties that are different from and ideally improved compared to those of the refractories to be repaired Products, e.g. B. improved strength over Wear or improved refractory properties.

The invention will now be elucidated with the help of the following examples explained in more detail.

example 1

A refractory mass is formed on a wall of the zinc distillation column. The wall contains bricks made of a silicon carbide carrier. A mixture of refractory particles, particles of a combustible substance that can be oxidized exothermically by forming a refractory oxide, and magnesium oxide particles is thrown onto these bricks. The temperature of the wall is 800 ° C. The mixture is thrown into a stream of pure oxygen at the rate of 60 kg / h. The mixture has the following composition:

SiC: 79% by weight
Si: 8%
Al: 5%
MgO: 8%

The silicon particles have a dimension below 45 microns and a specific surface area, which is between 2,500 and 8,000 cm ² / g contained. The aluminum particles have a dimension below 45 µm and a specific surface area which is between 3,500 and 6,000 cm ² / g. The size of the silicon carbide particles is less than 1.47 mm with 60% by weight from 1 to 1.47 mm, 20% from 0.5 to 1 mm, and 20% below 0.125 mm. The MgO particles have an average size of approximately 300 µm. "Average dimension" means a dimension such that 50% by weight of the particles have a dimension smaller than this average.

The wall repaired in this way becomes significant Subject to fluctuations in ambient temperature, and it it is observed that the new refractory mass is permanent adheres to the carrier.

The structure of the shaped mass is under the microscope examined. Excellent continuity is established between the new refractory mass and the refractory mass carrier detected. It is also found that the silicon dioxide formed by the combustion of silicon into the crystalline lattice of forsterite, cordierite and aluminum-containing spinel is incorporated.

For comparison purposes, a mixture containing no magnesium oxide is spun under the same conditions. The composition of this mixture is as follows:

SiC: 87% by weight
Si: 12%
Al: 1%

It is observed that the shaped refractory mass quickly changes from the Wall separates and peels off in solid blocks when the zinc distillation column begins to work.

In a modification of this example, the mixture is ver turns to repair the bottom of a coke oven that from normal silica bricks and silica Alumina brick is shaped. You get one Repair compound with good resistance to wear, that adheres well to the wall, even if they are different undergoes thermal changes.

Example 2

As a variation of Example 1, a mixture is used in the following context:

SiC: 82% by weight
Si: 8%
Al: 5%
MgO: 5%

The wall being repaired contains bricks with one Silicon carbide carrier, and it has a temperature of 700 ° C.

The refractory mass obtained also adheres permanently on the wall.

Example 3

The goal is to put a refractory mass on a wall of one To shape the coke oven, the highly compressed silica Contains bricks. While the apparent density of tra traditional silica bricks on the order of  1.80 is the apparent density of high density Bricks approximately 1.89. Such bricks are on recently appeared on the market for refractory material, these Brick advantageous properties compared to tradi tional silica bricks show remarkably in In terms of their properties of gas permeability and thermal conductivity.

The repair is carried out on a wall, the temperature of which is approximately 750 ° C, using the following mixture:

SiO ₂ : 80.5% by weight
Si: 11.1%
Al: 1%
MgO: 7.4%.

The size of the SiO ₂ particles is less than 2 mm, with a maximum of 30% by weight of 1 to 2 mm and less than 15% by weight below 100 µm.

The molded mass sticks permanently to the wall.

In contrast, managed under the same company conditions a similar mixture, but no magnesium oxide contains a refractory mass that differs slightly from separates the wall if it has different thermal Subjected to conditions that exist when the Oven is in operation.

Example 4

The aim is to produce a refractory mass on a wall of a coke oven which is made from a refractory material based on a silicon compound which is subjected to significant changes in the ambient temperature and whose temperature does not exceed 900 ° C. The repair is carried out on a wall, the temperature of which is approximately 750 ° C, using the following mixture:

SiO ₂ : 80% by weight
CaO. SiO ₂ (wollastonite): 8%
Si: 8%
Al: 4%

The average dimension of the wollastonite particles is about 300 µm. The metal particle size corresponds to that in Example 1 and the silica particle size corresponds to that given in Example 3.

Claims (6)

1. Ceramic welding process for forming a coherent refractory mass on a surface based on a silicon compound, in which a mixture of refractory particles and combustible particles are simultaneously thrown against the surface with oxygen, which release in an exothermic manner with the spun-off oxygen of sufficient heat to form the refractory mass under the effect of the heat of combustion, the mixture containing:

• a) combustible silicon particles, optionally in a mixture with ver combustible aluminum particles;
• b) refractory particles selected from silicon dioxide and silicon carbide as the main weight fraction of the mixture; and
• c) additional metal oxide particles of another substance selected from MgO, FeO or CaO; and or
• d) additional particles of a non-metallic compound, selected from peroxides, nitrides, carbides or silicates,

the components (iiia) and / or (iiib) causing the incorporation of silicon dioxide, which is formed by the combustion of the silicon particles, into a crystalline lattice. 2. A method for molding a refractory mass according to claim 1, characterized in that at least a portion of the silicon dioxide formed by the combustion of the silicon in a crystalline lattice of the forsterite structure and / or in a crystalline lattice of the spinel structure and / or is worked into a crystalline lattice of the cordierite structure. 3. A method for forming a refractory mass according to one of the An sayings 1 and 2, characterized in that the temperature of the upper area is less than 1000 ° C. 4. Means for carrying out the method according to one of claims 1 to 3, characterized in that the mixture contains:

• a) combustible silicon particles, optionally in a mixture with combustible aluminum particles;
• b) as the main weight fraction of the mixture silicon carbide as refractory particles; and
• c) additional metal oxide particles of another substance selected from MgO, FeO or CaO; and or
• d) additional particles of a non-metallic compound, selected from peroxides, nitrides, carbides or silicates.

5. Means according to claim 4, characterized in that these additional Chen particle (iiia) or (iiib) a particle size less than or equal to 500 µm. 6. Composition according to claim 4 or 5, characterized in that the to additional particles (iiia) or (iiib) a particle size of at least 10 µm.