WO2020144315A1

WO2020144315A1 - Production method for a surface-coated refractory material, surface-coated refractory material and industrial furnace

Info

Publication number: WO2020144315A1
Application number: PCT/EP2020/050522
Authority: WO
Inventors: Heiko Hessenkemper
Original assignee: Heiko Hessenkemper
Priority date: 2019-01-10
Filing date: 2020-01-10
Publication date: 2020-07-16
Also published as: DE102019100535A1

Abstract

The invention relates to a production method for a surface-coated refractory material, wherein a main body made of refractory material, in particular refractory ceramic, is provided and a surface of the main body is coated with a protective layer. According to the invention: - a glass raw material in the form of particles is applied to the surface of the refractory material that is to be coated, the glass raw material having a transition temperature; - the glass raw material is vitrified by heating the particles of the glass raw material on the surface, in particular together with the main body, to an increased temperature at or above the transition temperature in order to form a glass layer on the surface, wherein: - the glass layer is formed as a protective layer for the main body made of refractory material; and - the glass layer is chemically and mechanically modified on a side facing away from the refractory material such that an alkali-depleted and mechanically stressed surface layer is formed.

Description

Manufacturing process for a surface-coated refractory material, surface-coated refractory material and industrial furnace

The invention relates to a production method for a surface-coated refractory material. The invention further relates to a surface-coated refractory material which can be produced by the method and its use in an industrial furnace.

With refractory materials, particularly when used in high-temperature environments such as industrial furnaces, the refractory material is often susceptible to attack by alkalis. Alkaline compounds are present in all natural raw materials and are released when these raw materials are burned or heated. An alkali attack can occur in several ways. Due to their basic properties, alkalis can directly attack the surface of the refractory material. In addition, the porosity of refractory materials means that alkalis can penetrate the interior of the refractory materials and corrode the refractory material there. Corrosion can be observed for both the refractory materials that are in direct contact with the heated raw material, such as the tubs of glass ovens. In addition, however, an alkali attack can also take place from the gas phase. Such an atmospheric alkali attack can result in a significant reduction in the life of the refractory materials in question. For this reason, there are already various approaches to protect refractory materials. One approach to reducing alkali corrosion is to change the volume properties of the refractory materials. For example, US Pat. No. 6,313,057 B1 proposes a chemically and structurally modified refractory material which has greater resistance to an atmospheric alkali attack. However, a change in the chemical and structural properties of the refractory materials means a considerable additional effort in the production of these materials.

Another approach is to change the surface properties of the refractory material so as to reduce alkali corrosion. The refinement of the surface of refractory materials with metals such as gold or platinum is known here. The metals prevent alkalis from penetrating into the pores of the refractory material. Gold and platinum, but also other metals, have the further advantage that they are not attacked by alkalis themselves. A method for applying a metal layer on the surface of a refractory material is described in GB 2 1 15 30 A.

However, the raw material costs for refining the refractory material with metals are very high. In addition, refining the refractory material only leads to a slight increase in the alkali resistance of the refractory material.

A more advantageous approach is described in US2010 / 0242542 A1, according to which alkali corrosion of the refractory material in contact with a glass melt is prevented by introducing aluminum, tin or metal alcoholates into the pores of the refractory material, so that aluminum has a reducing effect at glass melting temperatures , Tin or the metal alcoholates occurs, so that oxides formed in the pores of the refractory material protect it from alkali corrosion.

The object on which the present invention is based is to specify a production method for a refractory material which is improved in particular with regard to alkali resistance and a refractory material which has been improved in particular with regard to alkali resistance.

In particular, the improved method and refractory material should address at least one of the above-mentioned problems, preferably represent an alternative to the surface refinement of refractory materials with metals. A production method for a refractory material which is improved with respect to alkali resistance and a refractory material which has been improved with respect to alkali resistance should be particularly advantageous in the event of an atmospheric alkali attack. According to the invention, the above object is achieved by a production method according to claim 1 for a surface-coated refractory material. The invention also leads to a corresponding refractory material of claim 11 and a glass melting furnace of claim 13, comprising a melting tank with a wall made of refractory material, in particular refractory ceramic, the refractory material being at least partially a surface-coated refractory material of the invention.

According to claim 1, a manufacturing method for a surface-coated refractory material is given. The surface-coated refractory material can in particular be a surface-coated refractory ceramic. Furthermore, the manufacturing process is particularly suitable for the production of surface-coated refractory material for use in a glass melting furnace.

The invention is based on the consideration that an economical use of a surface finishing is advantageously possible if the raw material and production costs for the surface finishing are reduced. In addition, the invention has recognized that surface refinement can already be achieved if a protective layer can be produced in an improved manner, in particular without metals. A protective layer should particularly preferably establish an alkali resistance on the surface of the material. In particular, a significant reduction in alkali corrosion can be achieved within the framework of this consideration if penetration of alkalis into the pores of the refractory material is not possible or is reduced.

A basic body made of refractory material, in particular made of refractory ceramic, is thus made available to the method as the starting material. A surface of the base body is then coated with a protective layer by the process. The invention is thus based on a known production method for a surface-coated refractory material, in particular refractory ceramics, preferably for a surface-coated refractory material for use in a glass melting furnace, a base body made of refractory material, in particular made of refractory ceramics, being provided and a surface of the base body with is coated with a protective layer.

According to the invention, the process is characterized by the following process steps: Applying a glass raw material in the form of particles to the surface of the refractory material to be coated, the glass raw material having a transformation temperature;

Vitrification of the glass raw material by heating the particles of the glass raw material on the surface to a temperature at or above the transformation temperature to form a glass layer on the surface.

First, the glass layer is formed according to the invention into a protective layer for the base body made of refractory material.

The invention has recognized that on the one hand a glass layer is suitable as a protective layer and can be implemented in an improved manner as an alternative to solutions based on metallic protective layers.

In addition, the invention has recognized that the glass layer can be modified particularly advantageously as a protective layer to achieve the object; this also has an advantage over metallic protective layers. In addition, according to the invention, the glass layer is modified chemically and mechanically at least in a surface layer on a side facing away from the refractory material. This advantageously serves to increase an alkali resistance of the refractory material.

According to the invention, the glass layer is modified chemically and mechanically, in particular to increase an alkali resistance of the refractory material, on a side facing away from the refractory material such that an alkali-poor and mechanically strained surface layer is formed, in particular on a base glass of the glass layer on the base body Refractory material.

In other words, according to the concept of the further development, a chemically and structurally modified glass layer is applied to a refractory material for surface refinement, which preferably averts the atmospheric attack by alkali.

The invention is particularly suitable for ceiling or wall coverings. Studies have shown that the surface resistance of, for example, chamotte compared to chamotte without surface refinement could be significantly increased by such a surface refinement. In particular, for an untreated and A refined crucible made of firebricks was shown that cracking of the crucible in the melting furnace due to an alkali attack caused by a mixture of sodium carbonate and potassium carbonate in the surface-treated crucible could be significantly reduced compared to the untreated crucible. The invention also leads to a surface-coated refractory material, in particular a surface-coated refractory ceramic, for use in a glass melting furnace, in particular produced according to one of the preceding claims, wherein a base body made of refractory material, in particular made of refractory ceramic, and a protective layer is formed on the surface of the base body. According to the invention, it is provided that the protective layer for the base body is made of refractory material as a glass layer, and in particular to increase an alkali resistance of the refractory material, the glass layer is chemically and mechanically modified at least in a surface layer on a side facing away from the refractory material, an alkali-depleted and mechanically strained surface layer is formed. In the following, the surface layer is referred to as the alkali-depleted surface layer and the underlying glass as the base glass.

Furthermore, the invention comprises a glass melting furnace having a melting tank with a wall made of refractory material, in particular refractory ceramic, the refractory material being at least partially made of a surface-coated refractory material as described above.

A surface coated refractory material of the invention can advantageously be used in one or more of the following applications. An alkali attack from the gas phase, for example, affects the upper part of a regeneration of industrial furnaces for the production of glass. Liner linings of furnace chambers for the production of float glass are also affected. This can lead to nepheline formation, which can lead to a considerable production disruption. It is also known that alkali attacks from the gas phase caused by burning coal damage the chamottes used in coking plants. This is also the case for chamottes that are used in tiled stoves or normal stoves that are fired with a fuel other than wood. Advantageous developments of the invention can be found in the subclaims and further develop the invention in relation to the task with further features.

The glass layer is formed into a protective layer for the base body made of refractory material, which is modified chemically and mechanically in particular to increase an alkali resistance of the refractory material, at least in a surface layer on a side facing away from the refractory material.

To increase an alkali resistance of the refractory material, the glass layer is advantageously chemically and mechanically modified on a side facing away from the refractory material in such a way that an alkali-depleted and mechanically tensioned surface layer is formed.

The formation of the alkali-depleted and mechanically stressed surface layer advantageously increases an alkali resistance of the refractory material. In particular, a particularly high resistance to alkali can be produced by using raw glass material that has already been reduced in alkali. As part of a further development, the glass raw material and / or the particles of the glass raw material have a reduced alkali content, in particular the glass raw material and / or the particles of the glass raw material will be subjected to dealkalization.

The particles of the glass raw material can, for example, be obtained from ground glass raw material. This can also include, for example, the use of grinding residues from flat glass, in particular grinding residues from float glass; It is advantageous that a reduced amount of alkali or the grinding residues are already de-alkalized in float glass. Glass raw material can preferably be borosilicate glass. The use of other types of glasses, even those that are not reduced in alkali, is also possible.

In general, the glass raw material and / or the ground glass raw material can advantageously be subjected to dealkalization even before it is applied to the refractory material. This has the advantage that that part of the glass layer on a side facing the refractory material - in particular directly below the chemically and mechanically modified part of the glass layer on a side facing away from the refractory material - has a reduced proportion of alkali or is low in alkali. I.e. In particular, the glass raw material and / or the ground glass raw material can advantageously material is subjected to dealkalization before being applied to the refractory material to remain with the formation of a base glass of the glass layer on the base body made of refractory material.

It is preferably provided in the manufacturing process that the transformation temperature is in a range from 600 ° C. to 800 ° C. and the elevated temperature in the glazing is in a predetermined range from 600 ° C. to 1400 ° C.

The glass raw material is advantageously heated to a temperature of 100-200 ° C. above the transformation temperature of the glass raw material. Depending on the glass raw material used, the glass raw material can be heated to a temperature in the range of 600-800 ° C. This process step advantageously makes a closed one

Glass layer formed on the surface of the base body. To form the closed glass layer, heating the glass raw material for a period of about 30 minutes has proven to be advantageous.

The chemical and mechanical modification is preferably carried out with at least two further process steps which lead to the formation of an alkali-depleted and mechanically strained surface layer; these can be implemented in any order one after the other or simultaneously in one or more process steps, individually or in combination. This is advantageously carried out in an autoclave, in particular the step “dealkalization” and “cooling” as explained below: 1. dealkalization of at least the surface layer of the glass layer in a neutral to acidic, aqueous solution and at an elevated temperature such that the alkali becomes poor Surface layer continuously formed in the glass layer. The dealkalization of the surface layer of the glass layer leads to the surface having a higher alkali resistance. As a result of the dealkalization, the glass layer then has two layers: a low-alkali surface layer and a base glass.

2. Cooling the glass layer by reducing the temperature at a predetermined rate, such that the alkali-depleted surface layer in the glass layer in any case partially tensions.

It is preferably provided in the manufacturing process that the alkali-depleted surface layer is continuously formed in the glass layer with a predetermined thickness. It is preferably provided in the production process that the thickness of the alkali-depleted surface layer depends on one or more of the parameters selected from the group consisting of: residence time in the aqueous solution, acidity and / or further increased temperature of the aqueous solution which is set in the aqueous solution is. A further predetermined temperature range and / or pH range in the aqueous solution, in combination with the residence time, has proven to be advantageous in the dealkalization.

By adapting the alkali-depleted surface layer, the alkali resistance of refractory materials can be adapted to the individual requirements that are specified by the various fields of application.

The temperature is advantageously reduced from the elevated temperature to room temperature at a predetermined rate. The predetermined rate should be in a range that is advantageous for generating a mechanical stress within the surface layer. It is preferably provided in the manufacturing process that the glass layer is formed on the surface of the refractory material with particles from a sol-gel process and / or the glass layer on the surface of the refractory material is produced by a sol-gel process.

It is preferably provided in the manufacturing process that the particle shape of the glass raw material is a flour, in particular a flour with a particle size in the range of 4 pm. This particle size is particularly advantageous since there is already a reduction in the alkali content in the glass raw material in a manufacturing process for producing glass raw material with this particle size.

It is preferably provided in the production process that the neutral to acidic, aqueous solution is an acidic solution with a pH value of slightly to moderately in the acidic range. It has been shown that when using an acidic solution, a pH in the given range is particularly suitable for dealkalization.

Embodiments of the invention will now be described below with reference to the drawing. This is not necessarily to show the exemplary embodiments to scale, rather the drawing, where useful for explanation, is in a schematic and / or slightly distorted shape. With regard to additions to the teachings which can be seen directly from the drawing, reference is made to the relevant prior art. It should be taken into account here that various modifications and changes regarding the form and the detail of an embodiment can be made without departing from the general idea of the invention. The features of the invention disclosed in the description, in the drawing and in the claims can be essential for the development of the invention both individually and in any combination. In addition, all combinations of at least two of the features disclosed in the description, the drawing and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below, or limited to an object that would be limited compared to the object claimed in the claims. For the specified design ranges, values within the stated limits should also be disclosed as limit values and can be used and claimed as required. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with an identical or similar function.

Further advantages, features and details of the invention emerge from the following description of the preferred exemplary embodiments and with reference to the drawing; this shows in:

1 is a block diagram of a manufacturing process for a surface coated refractory;

2 shows a schematic illustration of a surface-coated refractory material; FIG. 3A FIG. 3B shows a comparative example based on a result of a test for alkali resistance on a crucible made of firebrick as a refractory material.

1 shows a block diagram 100 of a manufacturing method for a surface coated refractory material. The blocks shown represent the individual process steps of the manufacturing process. The blocks 110 and 160 mark the beginning and the end of the manufacturing process. There are four process steps in between. In a first method step 120, a glass raw material in the form of particles is applied to a surface of the refractory material. The glass raw material has a Transformation temperature. In a second method step 130, the glass powder is glazed on the surface of the refractory material.

For this purpose, the glass powder is heated to a temperature at or above the transformation temperature of the glass raw material. The glazing creates a closed layer of glass on the surface of the refractory material. In a subsequent method step 140, a surface layer of the glass layer is dealkalized. For this purpose, the glass layer is placed in an aqueous, neutral to acidic solution at an elevated temperature.

In a final method step 150, the glass layer is cooled down to room temperature by a rate-wise reduction in temperature. A surface-coated refractory material produced by the manufacturing method 100 is shown in FIG. 2.

2 shows a schematic illustration of a surface-coated refractory material 200. The surface-coated refractory material is characterized by three components: a base body 230 and a surface coating consisting of a base glass 220 and an alkali-depleted surface layer 210. The base body 230 corresponds to an uncoated refractory material. In the surface-coated refractory material 200 shown here, the refractory material of the base body 230 is a refractory ceramic. In other embodiments of the surface-coated refractory material 200, the base body also consists of other refractory materials.

The surface coating consisting of the base glass 220 and the alkali-depleted surface layer 210 is located on a surface of the base body 230. The base glass 220 forms a lower layer, which is located directly on the surface of the base body 230. The alkali-depleted surface layer 210 is located on the base glass 220 and thus forms an outer layer of the surface coating.

The alkali-depleted surface layer 210 contributes to an increased alkali resistance, particularly in the case of atmospheric attacks. Furthermore, the alkali-depleted surface layer 210 and the base glass 220 are characterized by a different expansion coefficient, which leads to a stress close to the surface. The near-surface tension results in a reduction in transport processes within the surface coating and contributes to a further increase in alkali resistance. Act it If the base glass 220 is an alkali-reduced glass, the base glass 220 also serves as an alkali barrier.

In general, the glass raw material and / or the ground glass raw material can advantageously be subjected to dealkalization even before it is applied to the refractory material.

This has the advantage that that part of the glass layer on a side facing the refractory material 230, that is to say the base glass 220 as shown in FIG. 2, in particular directly below the chemically and mechanically modified part of the glass layer on a side facing away from the refractory material 230, thus directly below the alkali-depleted surface layer 210-- has a reduced alkali content or is alkali-depleted.

The surface coating consisting of base glass 220 and alkali-depleted surface layer 210 can be applied to base body 230, for example, by the production method shown in FIG. 1. However, it is also possible to use other manufacturing methods to produce the surface coating. Example of a firebrick test with alkaline melt

3A and 3B show a comparative example based on a result of a test for alkali resistance on a crucible made of firebrick as a refractory material. A crucible with common firebricks serves as a reference; d. H. with a base made of refractory material without coating a surface of the base with a protective layer. An identical crucible was treated by the method according to the concept of the invention, i. H. the base body made of refractory material was made available and a surface of the base body was coated with a protective layer. Various treatment options could be used here, with the steps taking place in all cases:

Applying a glass raw material in the form of particles to the surface of the refractory material to be coated, the glass raw material having a transformation temperature,

- Glazing the glass raw material by heating the particles of the glass raw material on the surface, in particular together with the base body, to an elevated temperature at or above the transformation temperature to form a glass layer on the surface, wherein - The glass layer is formed as a protective layer for the base body made of refractory material, and

- The glass layer is chemically and mechanically modified on a side facing away from the refractory material, in such a way that an alkali-depleted and mechanically strained surface layer is formed.

3A shows a top view of the crucible - in view (i) the reference and in view (ii) a crucible which has been treated according to the method according to the concept of the invention in order to visualize the improved alkali resistance. 3B shows the cut crucible along the cutting plane (left and right) - again in view (i) the reference and in view (ii) the crucible which was treated by the method according to the concept of the invention.

For the test, crucibles were prepared from existing firebricks and exposed to a test temperature. Different test temperatures were chosen

- In this representative comparative example shown here, the test temperature was set at 1350 ° C. Different trial operating times were also chosen

- In this representative comparative example shown here, the test action time was set to one hour.

In this representative comparative example for the concept of the invention shown here, the crucibles were filled with a mixture of 30 g of sodium carbonate and 30 g of potassium carbonate and covered with a lid. They were then preheated to 600 ° C and converted into the melting furnace at the test temperature of 1350 ° C.

When this test temperature was reached, they remained in the furnace for the test effective time of one hour and were subsequently annealed and from above - as in FIG. 3A with a reference crucible in view (i) and the crucible treated according to the concept of the invention in View (ii) visible-- shown.

The crucibles were then halved in the cold state and - as can be seen in FIG. 3B for the reference crucible in view (i) and the crucible treated according to the concept of the invention in view (ii) - along the cutting plane. As a result of the treatment according to the concept of the invention on the crucible in view (ii), in comparison to the reference crucible in view (i) in FIG. 3A, a clear improvement can be seen in terms of alkali bursting.

As can also be seen in comparison to the reference crucible in view (i) in FIG. 3B, the structure of the cut crucible in view (ii), which was treated according to the concept of the invention, is less attacked and the infiltration of the melt is significantly reduced or minimized.

As a result, the alkali resistance of the refractory material could be increased by the formation of the alkali-depleted and mechanically strained surface layer. In comparison of FIG. 3A (i) and FIG. 3A (ii), it can be seen particularly well that the crucible walls of the untreated reference crucible (reference) 300 have burst due to the alkali attack and cracks 301 have formed. In contrast, no cracks are visible in a crucible wall of the crucible 310 which has been surface-treated according to the method of the invention. 3B (i) shows the cut untreated reference crucible 300 from FIG. 3A (i). The cracks 301 in the crucible walls of the reference crucible 300 can also be clearly seen in this view. Furthermore, the discoloration around a chamber in the reference crucible 300 clearly shows a depth of penetration of the alkalis. With the untreated reference crucible 300, the maximum penetration depth 302 extends from the chamber to an underside of the crucible. In comparison to this, the depth of penetration 303 of the surface-treated crucible 310 is reduced by approximately half.

Claims

Expectations

1 . Production method (100) for a surface-coated refractory material (200), in particular refractory ceramics, preferably for a surface-coated refractory material for use in a glass melting furnace, wherein a base body (230) made of refractory material, in particular made of refractory ceramic, is provided and a surface of the base body with a Protective layer is coated, characterized by

- Glazing the glass raw material by heating the particles of the glass raw material on the surface, in particular together with the base body, to an elevated temperature at or above the transformation temperature to form a glass layer on the surface, wherein

- The glass layer is formed as a protective layer for the base body made of refractory material, and

- The glass layer on a side facing away from the refractory material is chemically and mechanically modified such that an alkali-depleted and mechanically braced surface layer (210) is formed, in particular on a base glass (220) of the glass layer on the base body (230) made of refractory material.

Manufacturing method according to claim 1, characterized in that the formation of the alkali-depleted and mechanically strained surface layer increases an alkali resistance of the refractory material.

3. Manufacturing method according to claim 1 or 2, characterized in that the

The method further comprises the steps: - De-alkalizing at least the surface layer of the glass layer in a neutral to acidic, aqueous solution, at a further elevated temperature, preferably such that the alkali-depleted surface layer forms continuously in the glass layer, and / or - cooling the glass layer by reducing the temperature from the further increased

Temperature preferably such that the alkali-depleted surface layer in any case partially tensions in the glass layer.

4. Manufacturing method according to one of claims 1 to 3, characterized in that the transformation temperature is in a range from 600 ° C to 800 ° C and the elevated temperature is in a range from 600 ° C to 1400 ° C.

5. Production method according to one of claims 1 to 4, characterized in that the glass raw material and / or the particles of the glass raw material have a reduced alkali content, in particular the glass raw material and / or the particles of the glass raw material are subjected to dealkalization, in particular to remain with formation of the Base glass (220) of the glass layer on the base body (230) made of refractory material.

6. Manufacturing method according to one of claims 1 to 5, characterized in that the alkali-depleted surface layer (210) forms continuously in the glass layer with a predetermined thickness.

7. The manufacturing method according to claim 6, characterized in that the predetermined thickness is set in the aqueous solution depending on one or more of the parameters selected from the group consisting of: residence time in the aqueous solution, acidity and / or further increased temperature of the aqueous solution .

8. Manufacturing method according to one of claims 1 to 7, characterized in that a further temperature is reduced from the elevated temperature to room temperature at a predetermined rate.

9. Manufacturing method according to one of claims 1 to 8, characterized in that the glass layer is formed on the surface of the refractory material with particles from a sol-gel process.

10. Production method according to one of claims 1 to 9, characterized in that the particle shape of the glass raw material is a flour, in particular a flour with a particle size in the range from 2 to 6 pm, in particular around 4 gm.

11. Surface-coated refractory material, in particular a surface-coated refractory ceramic, preferably for use in a glass melting furnace, in particular produced according to one of the preceding claims 1 to 10, wherein a base body made of refractory material, in particular made of refractory ceramic, and a protective layer is formed on the surface of the base body , characterized in that the protective layer for the base body is made of refractory material as a glass layer, and the glass layer is chemically and mechanically modified at least in one surface layer on a side facing away from the refractory material, an alkali-depleted and mechanically strained surface layer being formed.

12. Surface-coated refractory material according to claim 11, characterized in that the alkali-poor and mechanically strained surface layer increases an alkali resistance of the refractory material.

13. A glass melting furnace comprising a melting tank with a wall made of refractory material, in particular refractory ceramic, the refractory material being at least partially a refractory material coated on the surface according to claim 11 or 12.