The method of cleaning the surface of the refractory structures and method of ceramic welding

 

(57) Abstract:

The described method of cleaning the surface of the refractory structures at elevated temperatures, mainly in the preparation of ceramic welding. The method includes the issue mentioned on the surface of the jet of powder carrier in a stream of oxygen-containing carrier gas fuel particles and fuel particles and oxygen interact in the reaction zone at the surface, and the simultaneous release on the said surface cleansing stream containing oxygen, preferably at a speed greater than the speed of release of a jet of powder, for cleaning said surface in the vicinity of the reaction zone. The described method of ceramic welding, including preliminary purification stage the place the seam on the above method. 2 S. and 11 C.p. f-crystals, 2 Il.

The invention relates to a method of purification of refractory structures, in particular, which is the stage in the repair of damaged refractory structures.

Refractory constructions of various types, such as metallurgical furnaces, kokoulina furnace, glass furnace, tend to pollution, korrodirovaniju or damage (destruction) during their working campaign.

Of course, fire-proof design can be cleaned mechanically, for example, by spraying a gas or liquid, sandblasting using the apparatus (air jet with sand) or by sonication. In certain cases, when material, vozgorelsya or combustible, can be cleaned using a burner (if consouling furnaces, for example). In other cases, when you want to handle or clean the surface, can be used, for example, grinding wheel, drill bits and other cutting tools, but all of these methods have certain disadvantages for the subsequent repair of refractories. To clear the refractory structure or equipment and to obtain a surface suitable for receiving the products of good quality or for subsequent repair, the operator should be close to purify the place is very close, and this means that this place should have such a degree that it can withstand the operator within the time required for cleaning. And it also means that the refractory design must be cooled from its normal operating temperature or operating temperature normal aqueous type, to avoid damage to the furnace, as the refractory material is compressed (shrinks or expands, the cooling and heating can take several days or even several weeks, and this will significantly decrease the performance of the furnace.

The processing method of the refractory lining, known from the British patent CB 2213919 And (Glaverbel), is carried out at elevated temperatures and is that the stream supports combustion gas carrying the mixture of particles containing particles of one or more elements that are or oxidized before the formation of one or more refractory oxides (hereinafter will be referred to as combustible or fuel particles) and particles of refractory oxides are sent to the place that you want to repair, and combustible particles cause or allow the burning, then the above mixture is mixed with a flux, such as fluorides or alkali metal salts, moreover, the flux under the action of heat released during combustion of combustible particles, softens and stretches the refractory lining and refractory lining is aligned due to the removal or displacement of material under mechanical influence of the incident jet.

The method according to the patent CB 2213919 And useful to prolzovatsya as a preliminary stage in a number of ways to repair refractories, in particular, in such way, when the repair can be done near or at normal operating temperatures of the refractory lining (design). One such repair technology known as ceramic welding. This type of methods is illustrated in British patent N 1330894 and British application CB A (both under the name Glaverbel).

In such ways the ceramic welding coherent (associated) ceramic material is formed on the surface when throwing (discus) on the surface of the mixture of refractory particles and fuel particles together with oxygen. Used combustible or fuel particles have a composition and grain size distribution that they interact with oxygen to produce heat, i.e., exothermically, resulting in the formation of refractory oxides and heat needed to melt at least the surface emitted refractory particles.

In practicing the methods of ceramic welding mixture of refractory and combustible particles (powder for ceramic welding) is transported to the storage of powder along the power line to the spear (lance), from which it is thrown away on a given surface. The gas which is discharged from the spears together with powder for ceramic SGAs, such as nitrogen or some other gas.

Found that when the refractory lining (design) is processed in accordance with the patent CB 2213919, the surface of this design (lining) is modified (modified) structure. This is because not all of the softened material is removed from this surface and that the softened material includes material that was released in the alignment process. If you want the surface was free from foreign materials, you should choose alternating current method. In addition, the flux may remain on the treated surface. In the presence of a flux on the surface of the refractory structure (lining) subsequent ceramic welding may result in poor repair and may not provide good adhesion with refractory design (lining), as, for example, in the case of high-quality refractories used at a high temperature.

The aim of the invention is to provide a method of cleaning the surface of the refractory structure (lining), which may be effected without the necessity of cooling of this design from the normal operating temperature, and to avoid, thus, t is ernesti.

The invention consists in that in the method of cleaning the surface of the refractory structure at elevated temperatures, including the throwing of issue mentioned on the surface of the jet support combustion gas carrying combustible particles in the oxygen-containing gas-carrier (hereinafter "the stream of powder), through which the contained combustible particles cause or allow the burning zone of collision with the said surface (hereinafter, "reaction zone"), according to the invention simultaneously or alternately produced on the said surface of scour (purifying) a stream containing oxygen washout mentioned surface in the vicinity of the reaction zone. The heat generated by the combustion of the particles over the surface and adhering to the material, and cleansing to lose gas blows away the molten material.

The invention thus provides a method of purification of refractory structures (constructions), which can be carried out without any requirements to conduct certain stages of a significant and deliberate cooling of the structure from its normal operating temperature, eliminating in this regard, the need for long periods of cooling and warming, ornago materials. Under "clearing" means the removal of material with the desired area of the refractory structure, as well as remove part of the refractory material, if necessary. In this sense, the term "cleaning" also includes the term "alignment" mentioned earlier. For example, you can usually act in a way that did not require cooling of the refractory structure, and reheat before any transition point on the dilatometric curve of the material from which it is made. At a higher temperature refractory design efficiency of the method according to the invention is higher. Preferably, the temperature of the refractory structure was above 700oC, mainly above 1000oC.

The method has special advantages, because it is easily applicable for cleaning structures of sufficiently high quality refractories and/or at elevated temperature, which, however, relatively low compared to the maximum sustained working temperature for grade refractories, from which it is made.

Education required of scour gas used various oxygen-containing gases, but the optimal choice of gas depends on the circumstances. Because Obraniak variant of the method of scour gas contains mainly oxygen. It is preferable to use commercial grade oxygen, such as oxygen usually one way or another is used as the carrier gas and more efficient for this purpose. Because of scour gas contains oxygen, it eliminates the formation of a dense cloud of smoke from combustion in the reaction zone and promotes complete combustion used combustible fuel particles. However, it should be borne in mind that the carrier gas itself contains enough oxygen for complete combustion of the fuel.

Convenient to the stream of powder and jet scour gas was produced along at the said surface of General spears. The gas can directly affect the reaction zone, but preferably in its surroundings.

When the spear is moving across the surface, the impact zone of scour gas preferably immediately follows the reaction zone. It is preferable to scour the gas contained numerous discrete jets located near the jet of powder. Streams of gas can be produced simultaneously or alternately. For example, if the spear moves back and forth on the surface, one jet scour gas, following the stream of powder, can be covered, while the opposite staple with lots of outlets located in the vicinity of one or more output(s) hole(s) for powder.

Scour gas may be produced on the surface of the refractory structure continuously or in pulses (policyrule), whereas the powder is fed continuously.

The rate of production of scour gas is greater than the velocity of the carrier gas. The choice of this characteristic creates interference in the flow of material in the reaction zone.

Scour gas mainly cold. The use of cold gas produced in the reaction zone, which requires such a high temperature as is necessary for melting refractory material, surprising as it can be expected that the cold gas will cause the solidification of molten material faster than its removal. In addition to scour gas on the surface of the refractory structure is produced jet of powder containing combustible fuel particles in the oxygen-containing gas-carrier.

As fuel can be used various elements, especially elements that can form refractory oxides, excluding the deterioration of the refractory properties of the treated surface. Therefore, as fuel can b is silicon, because these items provide a good compromise between reality, ease and safety of use and cost. Particularly preferable to use a mixture of aluminum and silicon particles in which silicon than aluminum. Aluminum as more flammable serves to maintain the reaction zone, in which the melted silicon, and sufficient for this purpose heat. In accordance with the invention, the fuel particles made of such material, which interacts with oxygen to the surface with the formation of refractory oxides, whose chemical composition corresponds to the composition of the refractory lining (design).

Grain size distribution of the particles in the jet support combustion gas has a very important influence on the course of the combustion reaction occurring during the cleaning of the refractory structure. Found that it is desirable to use very tonkoizmelchennye fuel particles, it is preferable that the average grain size of the above particles was not more than 50 μm and preferably at least 80 wt. mentioned fuel particles had a grain size less than 50 microns. More preferably, the average size of the mentioned fuel particles is EP grains of less than 30 microns.

The expression "average grain size" used here as suitable for ceramic welding means such a size at which 50 wt. ( not quantity) of the particles have a size less than the average.

Usually a jet of powder contains additional, in addition to the fuel particles. These particles are mostly refractory oxide particles. The presence of these additional particles increases the liquid mass and contributes to its over, especially in the presence of flux. Also additive particles can complement the effect of mechanical erosion from impingement of the powder with the surface of the refractory structure. This also makes it possible to use mixtures of powders, the composition of which is similar to the composition of the powder used for the subsequent repair of refractory ceramic design welding. The choice of refractory oxide particles to be produced mixture is not crucial, as they are removed blur gas. It is preferable therefore to choose the material that will be used for ceramic welding, so as to reduce the number of necessary raw materials, to reduce problems arising from differences in thermal expansion or compression on the outer surface of the lock is you on the surface of the refractory structure and ceramic welding were similar in General terms. It also provides chemical compatibility between the cladding and the refractory structure. To facilitate adhesion and compatibility, it is preferable that the aforementioned refractory oxide particles contained particles of at least the main component (s) of the refractory structure.

In a preferred variant of the method according to the invention the refractory particles selected at least one of the oxides of aluminum, chromium, magnesium, silicon and zirconium.

Preferably, the maximum grain size of the refractory oxide particles was not more than 4 mm and preferably 80 wt. mentioned refractory particles had a size less than 2 mm

The optimal number of fuel particles introduced into the mixture depends on the operating conditions. At a given operating temperature, it is desirable to introduce into the mixture the more the fuel particles, the higher the quality of refractories. Similarly, for a given refractories, it is desirable to introduce more fuel, reducing the operating temperature to-clean places.

Basically the mixture used for cleaning, has a higher fuel content than the mixture of ceramic welding.

Mostly jet of powder contains at least 20 wt. fuel frequent Oliva, want to enter, and the period of time during which the reaction zone must be cleared place to clean it. Of course, we should note that for operation at low temperatures and with high quality refractories may need more fuel and that it requires less to work at high temperatures and with low-grade refractory materials.

Found that for satisfactory cleaning quite enough to put in the produced mixture fuel in an amount of about 30 wt. Mainly the content of the above particles in the produced mixture does not exceed 30 wt. This creates an advantage in saving, since the fuel particles are the most expensive part of the produced mixture. It was revealed that the introduction of excessive amounts of fuel particles may unjustifiably increase the risk that caused the reaction may apply to graduate (emit) device.

The powder mixture may contain particles and other materials, for example, peroxide or fluxes, and especially fluxes corresponding to the above-mentioned patent CB 2213919-A. It is also an advantage in the case when necessary and cleaning, and alignment.

To implement the dry and one or more outlet for release of scour gas in the direction parallel to the jet direction(nd) powder. In a preferred embodiment, the set of discrete outlets for release of scour gas there are so many jets scour gas was localized around the jet of powder. When observing this characteristic of scour gas strikes the surface of a refractory structure in the vicinity of the reaction zone. As the spear moves along the surface of the refractory structure, a blur gas cleans the surface of the heated reaction zone.

In some preferred embodiments of the invention, a jet of gas produced from a spear, cooled circulating fluid. Such cooling can be easily provided through supply of spears casing for water cooling. This casing for cooling is arranged around a Central pipe or pipes for supplying a jet of powder, while he himself is surrounded by a channel or channels for transportation of scour gas. Alternative or additional water housings may surround all producing gas pipe spear. The temperature of the emitting gas in the case of repair of the furnace at its operating temperature will be considerably lower than the temperature inside the surrounding PE the Yu spear is easy and allows you to create a blur gas in the zone of the dynamic impact of a jet of carrier gas with the powder in it, produced from the exhaust hole for the powder.

Some preferred embodiments of the spear was originally intended for small and medium repair or situations that must be cleared large areas, but the time required for cleaning is not crucial, and in this case, particles are released from the spear, with the only outlet for the carrier gas with a diameter of 8 to 25 mm, the cross-sectional Area of this outlet is from 50 to 500 mm2. These spears are suitable for production of powder with a speed of from 30 to 300 kg/h and can therefore be used for ceramic welding under certain conditions by regulating the composition of the powder. The diameter of the outlet(s) hole(s) for stream(s) scour gas is 5 to 10 mm and less than the diameter of the outlet openings for the jet of powder.

Other preferred embodiments of the spear was originally intended for large repairs carried out within a short time, and in this case, the cross-sectional area of the outlet for the carrier gas ranges from 300 to 2300 mm2. These spears are suitable for production of powder with a speed of up to 1000 kg/h and even more, and also mo is with jet scour gas, having the form of a circular arc, located around the jet of powder.

Scour the gas can be released from vents located on a line parallel to the line of holes, producing a jet of powder, then when the spear has a comb-like structure for treating large areas. However, it is preferable, when the issue of scour jets have used a spray holes located around the Central hole to release the powder. Such a device simpler and easier.

The spear may be straight or curved for easy use in confined spaces.

The invention also provides a method of ceramic welding, in which is formed a coherent refractory mass, coupled with the refractory structure in place of welding carried out by feeding a jet of powder carrying a mixture of fuel particles and particles of refractory oxides, against the welding, while the fuel particles cause or allow the burning to soften or melt at least the surface of the refractory oxide particles so formed are mentioned coherent refractory mass, coupled with the aforementioned structure, and the welding prewar is recommended to produce particles in the presence of high oxygen concentration, for example, using commercial grade oxygen as the carrier gas. Due to the very high temperatures in the reaction zone ceramic welding is possible to obtain a sufficient degree of melting or softening of the refractory particles, which makes possible the creation of high coherent mass with good fire resistance.

A particular advantage of the methods of ceramic melting is that they can be performed on the refractory structure at its normal high operating temperature. This clearly brings benefit of minimizing the downtime of the repaired structure, as well as reducing the problems associated with thermal contraction and expansion of the refractories. Melting at a temperature close to the operating temperature of the refractory structure, also benefits for the quality of the resulting weld. The reaction melt is capable of softening or melting the surface of the refractories, which provides good bonding of the workpiece and the newly formed refractory mass seam.

Very comfortable on stage, the ceramic welding to have the same composition of the produced mixture of particles, and at the stage of refractory cleaning, to save the mix on stage, the ceramic welding and reducing Topley formed simply by adding a certain amount of additional fuel particles to the mixture of particles, having the same composition as the mixture of particles to be used on stage, the ceramic welding.

In Fig.1 is a schematic representation of a partial section of the spraying lance suitable for use in the method according to the invention; Fig.2 views of the issuing end of the spear, is shown in Fig.1.

The spray head 4 spears 5 has a Central opening 6 for spraying a jet of powder containing fuel particles dispersed in the carrier gas. Instead of a single outlet, the spear can have a separate outlet for spraying a jet of powder. Spray lance with a group of the outlet openings of this type are disclosed in British application Glaverbel N 2170122. The head of the spear 4 contains also in accordance with the invention, means for release of scour gas. In the variant shown in Fig.1,2, means for release of scour gas contains four outlet openings 8 arranged in a group around a Central outlet 6 for spraying a blur gas four discrete jets. The mixture of particles dispersed in a gas medium is introduced through the supply pipe 10, and the oxygen to scour gas is injected through the channel 11. Spear 5 also includes the military furnace needed repairs of potovyh blocks of zirconium bearing refractory material such as "Zac". This zirconium bearing refractories has the approximate composition, by weight. the silica - 10-15, aluminum oxide 40-55 and Zirconia, 30-45.

The cleansing composition of the mixture of particles was chosen as follows, wt. Si 13, Al - 10, stabilized Zirconia, 30, L - alumina (corundum) 45.

Silicon and aluminum fuel particles had a nominal maximum grain size less than 45 microns. The average grain size of silicon was 6 μm, the average grain size of aluminum 5 μm, the average grain size of the zirconium oxide 150 μm and aluminum oxide 100 microns.

The mixture of particles dispersed in the oxidizing gas was sprayed with a spear 5, shown in Fig.1. The temperature of potovyh blocks was approximately 1400oC. the Mixture was introduced through the supply pipe 10. All Central exhaust hole had a diameter of 12.5 mm and the Mixture was sprayed with a flow rate of 30 kg/h, with oxygen as the oxidizing gas at a speed of 30 nm3/h Stream of carrier gas containing particles of the mixture and oxidizing gas, was hit on the treated area of the collision with the surface. In accordance with the invention, this surface is also processed by the sprayed jet scour gas, which has flown to the surface in the vicinity of and around the collision zone. VD pressure of 10 bar. Each of the four outlets had a circular cross-section with a diameter of 5. The method is carried out, jetting powder and four jets of oxygen to lose gas at the area of the surface being cleaned, and then policyrule produce only oxygen for softening and smoothing the surface.

After softening refractory structure in such a way that modifies a stream of powder, reducing the level of aluminium up to 4 wt. the level of silicon up to 8 wt. and therefore reducing the level of zirconium oxide and aluminum oxide. Interrupt (block) oxygen scour jet. Next, the structure of the ceramic repair by welding to a desirable extent. So obrazom cleaning refractory structure and ceramic welding can be carried out using the same spear without having to remove the spear from the furnace between these stages.

Example 2. In furnaces for the production of aluminum spray powder containing 30% aluminum and 70% aluminum oxide was used for the purification of alumina refractory structure at 1000oC. Other conditions described in example 1.

Example 3. In this example, the processed steel Converter in a short break between the two downloads. Refractory TVersity to issue a jet of powder 37.5 mm, the spear is capable of producing 1 t/h of powder. The surface temperature of the refractories 1400oC. Cleaning consists of melting and slag removal.

The powder composition: MgO 2 mm, maximum 75% Si 45 mm, a maximum of 15% Al 45 microns, a maximum of 10%

Scour gas was oxygen is supplied under a pressure of 10 bar through a number of holes with a diameter of 5 mm, located so as to provide a combined flat flow profile. After that, the treated surface repair using the same spear (without blur) gas and applying the powder with the composition: MgO 82% ZrO2-10% Mg/Al alloy 5% Al 3% as described in British application 2234502-A (Glaverbel L Fosbel International Ltd.).

1. The method of cleaning the surface of the refractory structures at elevated temperatures, comprising applying to the said surface of the jet support combustion of the gas carrying the fuel particles in the oxygen-containing gas-carrier (hereinafter referred to as "jet powder"), whereby the fuel particles cause or allow the burning zone of collision with the said surface (hereinafter referred to as "reaction zone"), characterized in that the said surface simultaneously or alternately serves cleansing stream containing oxygen scavenging (washout) rature mentioned support surface above 700oC.

3. The method according to p. 1 or 2, characterized in that the rate of release of the cleaning jet support greater than the speed of the jet of powder.

4. The method according to any of paragraphs.1 to 3, characterized in that the cleaning jet is formed from sets of discrete jets located around the jet of powder.

5. The method according to any of paragraphs.1 to 4, characterized in that the cleaning gas is produced under a pressure of at least 7 bar.

6. The method according to any of paragraphs.1 to 5, characterized in that use gas purifying cold.

7. The method according to any of paragraphs.1 to 6, characterized in that a jet of powder, in addition, include particles of refractory oxide.

8. Method op p. 7, characterized in that use spray powder comprising at least 20 wt. fuel particles, based on the solid content in it.

9. The method according to any of paragraphs.1 to 8, characterized in that use fuel particles made of a material which reacts with oxygen to the surface with the formation of the refractory oxide, the chemical composition of which corresponds to the composition of the refractory structure.

10. The method according to any of paragraphs.1 to 9, characterized in that a mixture of powders containing flux.

12. The method according to any of paragraphs.1 to 11, characterized in that the jet of powder and cleansing stream produced together on the said surface of the common spear.

13. The way to ceramic welding, in which the seam is formed and connected with the refractory structure of the coherent refractory mass is carried out by issuing a jet of powder carrying a mixture of particles containing fuel particles and particles of refractory oxides, welding, while the fuel particles cause or allow the burning, which soften or melt at least the surface of the refractory oxide particles so as to form a concatenated with said refractory structure coherent refractory mass, characterized in that conduct preliminary purification stage place seam according to any one of paragraphs.1 12.

 

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FIELD: powder metallurgy.

SUBSTANCE: starting powders of silicon, 40 to 400 mcm, and niobium, below 63 mcm, are taken in proportion (1.33-1.38):1 to form monophase product and in proportion (1.44-1.69):1 to form multiphase product. Powders are subjected to mechanical activation in inert medium for 0.5 to 2 min, ratio of powder mass to that of working balls being 1:20. Resulting powder is compacted and locally heated under argon atmosphere to initiate exothermal reaction producing niobium silicide under self-sustaining burning conditions. Process may be employed in metallurgy, chemistry, mechanical engineering, space, nuclear, and semiconductor engineering, and in electronics.

EFFECT: found conditions for monophase and multiphase crystalline niobium silicide preparation.

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