DD223803A1 - CERAMIC COATING AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

Ceramic coating and process for its production for industrial furnaces and heat aggregates in all branches of economy with the aim of creating a wear-resistant, emission-enhancing ceramic coating for the inner surfaces of the refractory lining in order to increase the efficiency and to reduce energy consumption. The object is to provide a ceramic coating in the form of a binder-containing metal oxide coating with an emissivity of 0.93, which is also resistant to oxidizing atmosphere and is applicable depending on the used refractory material of the liner. According to the invention, this object is achieved in that the binder-containing metal oxide coating of 80 to 99% by weight finely divided iron oxides or finely divided iron oxides and admixtures up to 5% by mass oxides of the metals chromium and / or nickel and / or titanium and / or manganese and / or Molybdenum and a conventional binder in the ceramic, wherein metal oxide as the main of scale of iron and / or iron alloys, in particular chromium, nickel, manganese and titanium-containing iron alloys or Ferroschlacke, as in the Erwaermungsprozess of Stahlbloecken anfaellt is included.

Description

8. A process for producing a ceramic coating, characterized in that the binder-containing

The metallic coating (4) is applied as a coating by means of spraying, spraying, brushing, rolling or rolling on the inner surfaces of the refractory lining (3) or the heat-insulating refractory layer (5) or non-woven fabric (6) or other elements in the space ,

9. The method according to item 8, characterized in that the binder-containing metal oxide coating (4) is applied to a intermediate heat-insulating layer (5) made of fibers or burner bricks or other interior elements before it is fixed in the interior of the industrial furnace or heat aggregate or.

be introduced. ,:

10. Procedure after.Pkt. 8 and 9, characterized in that the binder-containing metal oxide coating (4) is thin

: inorganic nonwoven fabric (6) is applied and this is adhered to the inner surfaces of the refractory lining (3) or other refractory surfaces in the interior.

11. The method according to Pkt.8 to 10, characterized in that the binder-containing Metälloxiddispersiön additionally up to 5 wt .-% of a chemical binder, preferably sulfite waste liquor is added.

12: A process according to points 8, 10 and 11, characterized in that a spring-resistant adhesive is used for attaching the nonwoven fabric (6) provided with the binder-containing metal oxide coating (4) to the inner surfaces of the refractory lining (3) as a blocking layer acts. · ·

For this T page drawing,

Field of application of the invention

The invention relates to a ceramic coating and process for its preparation for the inner surfaces of the refractory lining of industrial furnaces and heat units such as heat exchangers and combustion chambers of furnaces and burner bricks and other elements located in the interior of such plants, in all sectors of industry, agriculture and services available.

Characteristic of the known technical solutions

Industrial furnaces and heat aggregates have a refractory shell or liner for the purpose of heat insulation and as a heat transfer surface. This lining may consist of refractory masonry, monolithic or block construction in egg or multi-layer construction.

More recently, lightweight construction has been used, in which the refractory lining is made of refractory inorganic fiber material.

This fiber material is used in the form of mats, plates or modules in various thicknesses for lining. It has also become known that these fiber elements are applied to existing linings in heavy construction on the inside for the purpose of additional heat insulation and thus energy savings. This solution is very effective with heat treatment with discontinuous operation, since in addition to the loss of wall loss high low memory heat loss occurs. .

The total emission reduction of the refractory materials used in the lining for this lining is very different, but at application temperatures in the high temperature range it is 0.75 (individual authors vary). Exceptions are carbon-containing refractory materials such as Siiiciumkarbid- and graphite stones, the

a 0.88 b sit. - - ^---: ----- ^ - · - ·. ·, - -. -

In the solution according to DE-AS 1 302596 refractory coatings which form a glass phase are prepared from a mixture consisting of calcium fluoride, silica, potassium oxide, sodium carbonate, sodium fluoride, sodium silicate and Siiiciumkarbid and / or molybdenum carbide and / or graphite. Since this mass is applied relatively thick, be

-2-263 116 8

(DE-PS 3016377), in order to bring about a further improvement of the economical use of energy by having a layer of an inorganic fibrous heat-insulating material between the binder-containing SiC'-coating and the inside of the heating-furnace wall. This SiC _: coating has the disadvantage ,, that the SiG reacts in an oxidizing atmosphere in the high temperature range with the oxygen and therefore is not resistant to oxidation. In addition, a SiC coating is relatively expensive. According to the solution of DD 206552 refractory coating compositions of metallurgical slag or chrome or SiC ^ material and fillers and binders are used, which are applied in a layer of 2-5mm with the risk of chipping and large amounts are required, and not on fiber material can be used. -. , , '..''''"-.''''' _: '' - '·. · .. ·'. '.' · '. · ·.' ·

It is also known that the emissivity of the refractory materials during its use in the Wärmeaniagen changed (s.lzvestija vyrsich ucebuych zavedenij Cernajä Metallurgija [1980] 7, pp. 111-113). , · ..

This change comes once by structural change in ff material itself due to pressure and heat, as well as by the dusts accumulating from the atmosphere located in the heat transfer chamber and / or the material to be thermally treated. ,

In metallurgical heaters, it was found that the total emissivity of a high alumina liner. riaph 2.5-year operation increased from approx. 0.52 to approx. 0.91 (s.lzvestija mps. üceba Zaved. Cernaja Metallurgija [1980] 7, p.

113). : "/,; ·. '.. ..; /';, '.'. '.'';;''. · ·'. '. .- - .. .- - '·. ^{:: ':.}

Object of the invention,

The object of the invention is by the application of a ceramic coating in the form of a binder-containing metal oxide coating on the inner surfaces of the refractory lining or in the heat transfer chambers' arranged refractory elements of industrial furnaces and heat units in the zones and heat transfer spaces where the heat to the Wärmgut bz .w. the surface to be heated is transmitted predominantly according to the principle of indirect radiation heat transfer via acting as Sekundärheizfläche inner wall of the refractory lining to increase the emissivity of these surfaces from the beginning of the furnace trip and by the associated 'intensification of the radiant heat transfer more effective efficiency and thus a reduction Energy consumption while reducing the wear of the refractory lining to achieve. Durcrrdas applying the ceramic coating on refractory surface ^ where combustion reactions take place, such. 8. burner stones, the combustion process in the boundary layer can be activated, which leads to the temperature increase of the radiating surface.

Explanation of the essence of the invention

The invention has for its object to increase a ceramic coating and process to ^ their production for industrial furnaces and heat aggregates, by applying a firmly adhering yerschleißfesten> to 1700 K thermally resistant binder-containing metal oxide coating, the emissivity of the lining from the beginning of the furnace journey and an emissivity equal or greater than 0.93. By increasing the Emissiönsgrades the refractory lining, including inorganic fiber material or fiber spraying masses or refractory ve'rschäumbarer lightweight material, entering energy: and wear-reducing effect is auchbei oxidizing furnace atmosphere '.wirksam · ¹ /;.''' -. ...-. '. ';. ^: , ''"" · _; , '. , '· ·' ·. '''''. · '. , According to the invention this object is achieved in that a ceramic coating of a binder-containing metal oxide coating consisting of finely divided iron oxides or iron oxides with minor admixtures of oxides of the metals chromium and / or nickel and / or titanium and / or manganese and / or molybdenum and a conventional in the ceramic Binder, wherein as metal oxide Vorrahgig tinder of iron and / or iron alloys / in particular chromium, nickel, titanium, manganese and molybdenum iron alloys or feinteilige ferro slag, as obtained in the heating process of steel blocks; on the inner surfaces of the refractory lining of industrial furnaces and heat generators and burner bricks and other refractory elements in the interior, z. B. Regeneratorgittersteine or kiln furniture can be applied.

The refractory lining can also consist only of fibrous materials or fiber spraying masses.

The particle size of the metal oxide or the dry binder-containing metal oxide mixture is 1 mm, with up to 70Ma.-. % of the particles can have a size of 250 to 1 mm /

The effect of energy savings is significantly increased when a heat-insulating refractory layer of fibrous material or fiber sprayed aggregates or of lightweight construction material is provided between the inner surfaces of the refractory lining and the binder-containing metal oxide coating. , ,

Under certain furnace room conditions and certain refractory lining materials, it is advantageous to prevent premature wear; if between the binder-containing metal oxide coating and the refractory lining or the heat-insulating refractory layer or a nonwoven additional, also the pores and cracks of the refractory wearable refractory blocking layer of finely divided material based on high alumina (50 Ma '.-% alumina) or magnesium oxide or chromium oxide-containing substances or a mixture of the abovementioned components with or without binders and dispersants. As a binder for the metal oxide coating, clay is very suitable. '. ,

The ceramic coating by means of binder-containing metal oxide coating is carried out according to the following process steps

manufactured. \ / '· -. '''';"'''''' - ^: '../y'''."'"'.''.'.·:.'''"'·"'.

; After Neuzustellüng the refractory lining of the binder-containing metal oxide as Überzugsdispersioh by means of spraying, atomizing * is applied brush, roller or rollers to the refractory internal surfaces and according to the usual drying and heating of the industrial furnace or heat Aggregates the ceramic coating above 800 ^p C sinters through. · '. -. "-.:. -> · -. ''..'

^k The binder-containing metal oxide coating may be applied to the fiber layer outside the furnace and the fiberboard, mats, modules or elements may then be secured to the interior surfaces of the furnace. Also, the binder-containing metal oxide coating can be applied to a thin inorganic nonwoven fabric and then adhered to the inner surfaces of the refractory lining, such as a kind of wallpaper. This is particularly advantageous in small furnace spaces, where the application methods are difficult to apply or the binder-containing metal oxide mixture z. B. can come into contact with SiC heating rods during the order. These coated fiber webs can also be made up into rolls. For the purpose of better adhesion of the binder-containing metal oxide coating at ambient temperature, the mixture may additionally contain a chemical binder, such. B. sulfite liquor are added; The nonwoven fabric provided with the binder-containing metal oxide coating can advantageously be applied with a refractory adhesive to the inner surfaces of the refractory lining, which at the same time acts as a blocking layer.

Embodiment. '

The ceramic coating according to the invention and the process for its production will be explained in more detail below with reference to four exemplary embodiments:

'Example 1 (Fig.1). Λ

A blast furnace is coated on the inner surface of the refractory lining 3 of the false ceiling and the wall (chamotte I x) after delivery with a binder-containing metal oxide coating 4 by means of spraying. The coating mixture consists of a finely divided mixture of 95% by weight of scale, of which 15% by weight of the scale has a particle size of 250 to 1 mm and the particle size of the remaining amount of scale is below 250, and 5% by weight of binding clay. The metal oxide mixture is mixed until the Forbkonsistenz with water.

The specific dry amount of the coating dispersion is 0.37 kg / m. The application thickness was 0.2 to 0.3mm. At the blast furnace are burners with a low-glowing natural gas flame in use.

The energy savings compared to a newly delivered oven without ceramic coating on the inner surfaces is' 9%. '. '''·'. , · -. \;. , .;. , _; ';

Example 2 (FIGS. 2 and 3).

A comb annealing furnace with furnace room temperatures of (1273 K) was lined on the inside of the vault and the side walls of fireclay with a heat-insulating refractory layer 5 of fibreboard with a thickness of 4cm. The back wall was delivered with light-weight concrete blocks, which have a high SiO ₂ and CaO content. The inner surfaces of these refractory concrete blocks were first coated with a refractory blocking layer 8 of about 0.2 mm thickness of finely divided dispersible high alumina material. Thereafter, the binder-containing Metalloxiddispersiön was sprayed with 96 wt .-% finely divided scale of a chromium-nickel-iron alloy and 4 wt .-% binding clay in a layer thickness of about 0.2 mm. The particle size of the dry binder-containing metal oxide slurry was 250. The energy savings over the oven, which was not additionally internally provided with heat-insulating material and the ceramic coating with a binder-containing metal oxide coating, was 17%.

Example 3 (Figure 4). · J

On a refractory nonwoven fabric 6, the binder-containing metal oxide dispersion used in Example 2 was sprayed with an addition of 2 wt .-% sulfite liquor and then in a equipped with SiC heating rods hardening furnace with a high alumina refractory adhesive, which also acts as blocking 9, to the ceiling glued.

Example 4 (Figure 5)

The Flammenmenbegrenzungsflächen a radiant burner block 10, which is used as ceiling radiant burner are sprayed to the mixing head with the binder-containing metal oxide coating 4 of Example 1 for the wall. The remaining inner surface of the blanket is rolled with the binding agent-containing metal oxide dispersion in a layer thickness of 0.2 to 0.3 mm.

Claims (7)

-1- 263 116 Invention claims: 1. Ceramic coating for the inner surfaces of the refractory lining (3) of industrial furnaces and heat units: and Brehnersteine and other interior elements, characterized in that the ceramic coating of a binder-containing metal oxide coating (4) with 80 to 99Ma .-% finely divided iron oxides or finely divided iron oxides and admixtures to 5 wt .-% oxides of the metals chromium and / or nickel and / or titanium and / or manganese and / or molybdenum and a conventional binder in the ceramic, wherein as the metal oxide primarily of iron and / or Iron alloys, in particular chromium, nickel, manganese and clay-containing iron alloys or ferro-slag, as z. B. beii heating of steel blocks obtained is included. 2. Ceramic coating according to item 1, characterized in that the particle size of the metal oxide or the binder-containing metal oxide mixture is 1 mm. 3. Ceramic coating according to item 1 and 2, characterized in that up to 70% by mass of the metal oxide or the binder-containing metal oxide mixture have a particle size of 250 to 1 mm. 4. Ceramic coating according to Pkt. 1 to 3, characterized in that between the inner surfaces of the refractory 'Lining (3) and the binder-containing metal oxide coating (4) a layer of heat-insulating refractory material (5) is provided. V 5. Ceramic coating according to Pkt. 1 to 4, characterized in that between the inner surfaces of the refractory lining (3) and the binder-containing metal oxide coating (4) arranged layer of heat-insulating refractory material (5) made of organic fibers or a non-woven fabric or foamable lightweight construction material or Faserspritzmasse exists. 'ν: 6. Ceramic coating according to item T to 5, characterized in that between the binder-containing metal oxide coating (4) and the inner surfaces of the refractory lining (3) or a heat-insulating refractory layer (5) or a non-woven fabric (6) an intermediate refractory blocking layer ( 8) is provided from finely divided material based on high alumina content (50% alumina content) or magnes iümoxidhaltiger or chromium oxide-containing substances or a mixture of the aforementioned components with or without binders and dispersants. 7. Ceramic coating according Pkt. T to 6, characterized in that preferably used as the binder clay