US3337206A - Ceramic and tar bonded brick furnace lining - Google Patents

Description

Aug. 22, 1967 BQUVIER 3,337,206

CERAMIC AND TAR BONDED BRICK FURNACE LININC Filed July 6, 1964 INVENTOR GEORG 30L) VIER United States Patent Op 3,337,206 CERAMIC AND TAR BONDED BRICK FURNACE LINING Georg Bouvier, Leoben, Styria, Austria, assignor to Veitscher Magnesitwerke-Actien-Gesellschaft, Schuhertring, Vienna, Austria, a corporation of Austria Filed July 6, 1964, Ser. No. 380,232 Claims priority, application Austria, July 9, 1963, A 5,499/63 4 Claims. (Cl. 266-43) ABSTRACT OF THE DISCLOSURE A working lining for metallurgical vessels consisting of ceramically bonded and tar bonded basic and neutral refractory shapes. Each lining layer consists of the ceramically bonded shapes interspersed with a suificient number of the tar bonded shapes, preferably alternating with each other, for the latter shapes to take up the thermal expansion of the ceramically bonded shapes.

The invention relates to a lining for metallurgical vessels, in particular crucibles, converters, rotors, and electrical furnaces, used for carrying out metallurgical processes, and in particular for the smelting of steel. Of principal concern in this case are those processes in which pure oxygen is allowed to act on the melt. A satisfactory lining for such vessels has proved to be of ceramically bonded bricks, such as may be obtained by burning (also called kiln firing) or by a smelting process, which bricks are impregnated after the conclusion of the process causing the ceramic bond, with a carbon-containing medium. Impregnation with this carbon-containing medium may be effected either by immersion in it, or by treatment under vacuum and/or excess pressure, if necessary at elevated temperature. The purpose of this impregnation process is to fill the pores of the fired or smelted shaped element with carbon, in order to render it more resistant to the attack of slag or metallic baths. The carbon-containing medium may be hydrocarbons, the distillation products of coal, crude oil or wood, in particular tar or pitch, or finely-dispersed suspensions of soot or graphite in a suitable carrier liquid. It is also possible to elfect the deposition of the carbon by means of the decomposition of a carbon-containing gas in the pores of the brick. The shaped elements, which have been treated with carbon by one of the above methods, may also be fired under reducing conditions. 1

If a metallurgical vessel is lined with such shaped elements, which may for example be fired, tar-impregnated bricks, expansion gaps must be provided to take up the thermal expansion of the bricks until the operating temperature is reached. In the case of a cylindrical vessel, it is essential to provide within a ring of bricks, i.e., in the case of a vertical cylindrical vessel in a horizontal direction, space for expansion of the order of 1%, depending on the material of which the bricks are composed. This expansion space has hitherto been provided by combustible inserts, preferably of cardboard of appropriate strength. Such combustible inserts are, however, subject to various disadvantages. It is, for example, not possible with these inserts, which are uniformly strong over their Whole length, to obtain in the case of the lining of convex sectors of wall, especially where the radius of the curved sector is small, a uniform compensation for the expansion over the whole depth of the wall, thus leading to stresses and to the chipping 01f of layers of brick. The principal disadvantage of combustible expansion inserts is, however, that on the heating of the vessel they are rapidly burnt out, leaving behind empty gaps. Although these 3,337,206 Patented Aug. 22, 1967 ice empty gaps will in the main be filled in again by the thermal expansion of the bricks during the progressive heating of the lining, it is nonetheless possible for the carboncontaining impregnation agents and their distillates to escape through these gaps into the interior of the vessel. It is also possible for tar distillates from an, e.g., tarcontaining back-ramming attached behind the wearing lining, to pass through the gaps. Any escape of the carbon compounds in question to the outside of the vessel is prevented by the suitably sealed shell, e.g., steel. casing, of the vessel. I

However, in order that the bricks may retain the slagrepelling properties, imparted to them by the introduction of the carbon, it is necessary to block the egress of the carbon-containing compounds and to prevent as far as possible the escape of the components and distillates of these. Since such escape takes place principally through non-sealed gaps, the formation of such gaps must be prevented in advance.

The formation of gaps is furthermore promoted by the fact that the ceramically-bonded, e.g., fired, bricks possess, due to their method of manufacture, small surface roughnesses, which prevent the gaps becoming completely closed even after the burning away of the expansion inserts and the thermal expansion of the bricks.

In order to avoid these disadvantages, it is proposed according to the invention to line metallurgical vessels with two types of refractory shaped elements. The shaped elements are of refractory materials which are chemically basic or neutral. One type of the shaped elements are ceramically bonded elements treated with a carboncontaining medium, and the other type are unfired and bonded with carbon-containing media.

According to the invention, the lining comprises a plurality of layers of these two types of refractory shaped elements, each lining layer consisting of the ceramically bonded elements interspersed with a sufiicient number of the unfired shaped elements or bricks, which have been bonded with tar or some such substance, to take up the expansion of the ceramically bonded, e.g. fired, shaped elements and to prevent the formation of undesirable gaps. In view of their relatively loose structure and their tar content, the tar-bonded shaped elements are sufiiciently pliable and compressible for this purpose; this'can also be obtained by the use of lower production pressures, the selection of a suitable quantity of tar or other like bonding agent and of a refractory material of suitable grain size. r

If the occurrence of gaps is prevented in this way, the only route for the escape of the volatile-compounds in question into the interior of the vessel is via the pores in the bricks. This has the further advantage of causing a deposition of carbon in the pores of the bricks due to the rise in temperature.

As carbon-containing bonding agents for the unfired shaped elements in question, first consideration is given to tar, pitch or bitumen, alone or in combination, it being possible to add further carbon-containing substances, such as graphite or soot, in order to increase the carbon content. These bonding agents can, moreover, be precracked. Bricks, bonded with tar or the like, for the lining of metallurgical vessels are already known, but in such cases the whole lining has been produced from the same material throughout.

BRIEF DESCRIPTION OF DRAWING In the schematic drawings illustrating embodiments of the invention:

FIG. 1 is a perspective view of a part of a lining in a metallurgical vessel;

FIG. 2 is a plan view of a part of a ring of bricks in another embodiment of the lining;

DETAILED DESCRIPTION If ceramically-bonded shaped elements or bricks 1 and tar-bonded shaped elements or bricks 2 of approximately the same size are used for the lining, they can be arranged in checkerboard formation, as shown in FIG. 1. The shell 3 of the vessel, the permanent lining 4 mostly consisting of fired magnesia bricks and the back-ramming 5 consisting of tar-dolomite or tar-magnesia rammingmiX are shown in section.

Expansion may be sufiiciently compensated by a brick bonded with tar or similar bonding agent interspersed after a certain number of ceramically bonded bricks, e.g., after every second, third or fourth brick. In FIG. 2 there is shown an embodiment wherein one tar-bonded brick 2 is interspersed after each three ceramically bonded bricks.

In general, however, it will be useful as far as possible to lay one compressible tar-bonded shaped element into each gap. It is, however, desirable for the material which determines the degree of wear, i.e., the material which is present in excess, to be ceramically bonded. This is effected by having the unfired shaped elements produced in the form of plates 6, i.e., inserts which are considerably narrower than the ceramically-bonded bricks 1, a possible width ratio being, e.g., 1:4. As shown in FIG. 3, in the case of a vertical cylindrical vessel, these plates 6 are laid in the vertical gaps between the ceramically-bonded bricks 1. In FIG. 3 there are also indicated the furnace shell 3, the permanent lining 4 and the back ramming 5.

As shown in FIG. 4 it may also prove of practical advantage to combine one ceramically-bonded brick and one tar-bonded unfired plate 6 into a single unit 7 for ease of handling, e.g., by adhesive means, thus simplifying and shortening the lining process.

All basic or neutral refractory materials may be used as refractory material both for the ceramically-bonded and for the tar bonded bricks or shaped elements, in particular magnesia or periclase (sintered magnesia from natural or from purified magnesite or artificially manufactured magnesia, e.g., from sea water), dolomitic magnesia, dolomite, if desired with the addition of chromium ore, clay, magnesium-aluminium-spinel, lime or similar materials. According to the required use, the magnesia may be selected with a high or low iron content. (Instead of the term sintered magnesia there are often used the terms calcined magnesia or dead-burned magnesia) Example The following materials were used for the lining of an LD crucible:

(a) Fired bricks: size x 400 x 94 mm. (wedge bricks); pressed of sintered magnesia, fired in a continuous-type tunnel kiln at approx. 1700 C. and then impregnated with steel-works heavy tar by means of vacuum treatment at an elevated temperature (approx. C).

(b) Tar-bonded plates: size x 400 x 94 mm., from sintered magnesia, mixed with 4% steel-works heavy tar and 2% hard tar and compressed. These two types of brick were laid alternately.

In a comparative experiment an LD crucible was lined partly with bricks according to (a) above together with expansion inserts of cardboard and in another part with the combination of bricks according to (a) and plates according to (b), as shown in FIG. 3. It was shown in this case that the section, lined in the latter fashion, suffered appreciably less wear than the section lined with fired bricks according to (a) alone.

What I claim is:

1. A lining for a metallurgical vessel, comprising a plurality of layers of two types of refractory shaped elements, said shaped elements being of refractory materials selected from the group consisting of chemically basic and neutral materials, one of said types of shaped elements being ceramically bonded elements treated with a carbon-containing medium and subject to thermal expansion at operating temperatures of the metallurgical vessel, and the other type of said shaped elements being unfired and bonded by a carbon-containing medium, said bonded shaped elements being compressible, and each of said lining layers consisting of said one type of shaped elements interspersed with a sufficient number of the shaped elements of the other type for the latter elements to take up the thermal expansion of the ceramically bonded elements.

2. The lining of claim 1, wherein the bonded shaped elements have the shape of narrow inserts.

3. The lining of claim 2, wherein the ceramically bonded shaped elements and the narrow inserts are bonded together into single units each consisting of a ceramically bonded shaped element and a narrow insert.

4. The lining of claim 1, wherein the two types of shaped elements alternate with each other in each of said layers, and in adjacent ones of said layers.

References Cited UNITED STATES PATENTS 2,567,007 9/1951 Brassert et al 26643 X 3,058,736 10/1962 Martinet 26643 3,190,626 6/1965 Schwabe et al. 266-43 X I. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

Claims (1)

1. A LINING FOR A METALLURGICAL VESSEL, COMPRISING A PLURALITY OF LAYERS TO TWO TYPES OF REFRACTORY SHAPED ELEMENTS, SAID SHAPED ELEMENTS BEING OF REFRACTORY MATERIALS SELECTED FROM THE GROUP CONSISTING OF CHEMICALLY BASIC AND NEUTRAL MATERIALS, ONE OF SAID TYPES OF SHAPED ELEMENTS BEING CERAMICALLY BONDED ELEMENTS TREATED WITH A CARBON-CONTAINING MEDIUM AND SUBJECT TO THERMAL EXPANSION AT OPERATING TEMPERATURES OF THE METALLURGICAL VESSEL, AND THE OTHER TYPE SAID SHAPED ELEMENTS BEING UNFIRED AND BONDED BY A CORBON-CONTAINING MEDIUM, SAID BONDED SHAPED ELEMENTS BEING COMPRESSIBLE, AND EACH OF SAID LINING LAYERS CONSISTING OF SAID ONE TYPE OF SHAPED ELEMENTS INTERSPERSED WITH A SUFFICIENT NUMBER OF THE SHAPED ELEMENTS OF THE OTHER TYPE FOR THE LATTER ELEMENTS TO TAKE UP THE THERMAL EXPANSION OF THE CERAMICALLY BONDED ELEMENTS.

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