US2759723A - Compress laminated refractory block for metallurgical furnaces - Google Patents

Description

G. CRES Pl Aug. 21, 1956 COMPRESS LAMINATED REFRACTORY BLOCK FOR METALLURGICAL FURNACES 5 sheets-sheet 1 Filed Feb. 5, 1954 G. CRESPI Aug. 21, 1955 COMPRESS LAMINATED REFRACTORY BLOCK FOR METALLURGICAL FURNACES 3 Sheets-Sheet 2 Filed Feb. 3, 1954/ Aug. 21, 1956 G. CRESP] 2,759,723

COMPRESS LAMINATED REFRACTQRY BLOCK FOR METALLURGICAL FURNACES Filed Feb. :5, 1954 5 Sheets-Sheet s United States atent COMPRESS LANIINATED REFRACTORY BLOCK FOR METALLURGICAL FURNACES Giovanni Crespi, Omegna, Italy Application February 3, 1954, Serial No. 408,000

Claims priority, application Italy February 3, 1953 1 Claim. (Cl. 266-43) The present invention relates to an improved method for forming the refractory lining of metallurgical furnaces such as are furnaces, Martin-Siemens furnaces, blast furnaces, rotary furnaces, Bessemer cupola furnaces, mixers and industrial furnaces in general.

As it is known in said furnaces, and more particularly in Martin-Siemens furnaces and are furnaces, the lining of the bottoms at least is actually made by tamping masses of loose pulverulent or granular materials mixed with cementing substances such as tar, directly upon the bearing surface of the furnace, into layers parallel to said surface which tend to easily disintegrate and thus create corrosion zones while the lining of the vaults is made either of silica refractory bricks, such as silica bricks which have the drawback of dripping during the casting operations, or of magnesite-chromite bricks which are very expensive, having in mind their short life, and are in any case of a very small size as the above mentioned silica bricks. As it will appear clearly these known construction systems of the bottoms and the vaults cause the furnace to remain inoperative for quite a long time during the formation of the lining and furthermore involve the employment of considerable manpower that during the running of the furnace remains idle. For these reasons, apart from other considerations, the economical operative results of the furnaces are at present quite unsatisfactory.

The improved method for forming refractory linings for furnaces according to the present invention essentially consists in constructing at least a section of such lining of pre-fabricated elements or blocks so dimensioned as to be capable to build up said lining by means of the association of a few blocks and having a structure stratified according to predetermined directions so as to allow said blocks to be used also for the lining of the bottoms and vaults of the furnaces as well as the walls thereof.

According to the above mentioned method, it is possible to obtain a very quick change of the refractory lining such as wall, bottom or vault lining, in any type of furnace with a reduced employment of manpower, which can be conveniently utilized during the running of the furnace for preparing the blocks either in the same places where the furnaces are installed or in any especially equipped place for the production and the installation of refractory blocks according to the invention.

Said blocks, which have a general parallelepipedic shape with plane or curved walls according to their particular destination, are preferably obtained by compressing loose pulverulent or granular material mixed with cementing susbtances into molds in which said material is compressed in succeeding layers of sufficiently small thickness and so arranged that their stratification planes are substantially perpendicular to the block face designed to constitute the inner surface of the lining.

However, according to a further characterising feature of the invention, it is possible, in order to speed up the manufacture of said blocks, to insert in the single layers small compact masses of convenient thickness, which are preformed, by pressing said incoherent material in molds by means of presses under a suitably high pressure.

Due to the stratified structure the danger of surface disintegration and consequent formation of zones of greater corrosion is completely avoided. Another advantage is that, should the planes of said layers be perpendicular to the periphery of the armature containing them, it will result in an increased compactness of the lining during the running, as a consequence of the resistance offered by said armature to their expansion.

It is convenient, although not strictly necessary, that the compression of the incoherent material for the formation of big blocks, be effected in molds in which there has been arranged a metal reticular frame which extends with some of its portions from the blocks surface so as to serve as a means for gripping the blocks for their transport and at the same time to increase their resistance to disintegration before and during the installation. To the same purpose, short rod-like pieces of refractory material or the like, such as graphite, orientated in said mass or in the thickness of the single layers, can be introduced into the mass in order to cooperate with said metal frame or as a substitute for said frame.

In'the absence of a reticular frame, it is absolutely necessary that other means be provided in order to make easy and safe the transport of said blocks of great size. Some of these means are illustrated in the following description as an important part of the invention.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings illustrating by way of example and not in a limiting way, some embodiments of the invention, in which:

Fig. l is a perspective schematic view, with some parts broken away of the crucible of a Martin-Siemens furnace.

Fig. 2 is a cross sectional view with some parts in perspective of the vault of the same furnace.

Figs. 3 and 4 are partial sections of two different forms of vaults that can be used both for are and Martin- Siernens furnaces.

Fig. 5 is a plan view of an arc furnace vault.

Fig. 6 is a perspective view showing the disposition of a metal reticular frame in one of'the peripheral blocks of the arc furnace vault.

Fig. 7 is a perspective schematic view of a Bessemer converter showing a lining ring according to the invention which embodiment is applicable also to cupola furnaces.

Fig. 8 is a perspective view showing the method of formation of a block.

Figs. 9 to 13 are perspective views of different embodiments of blocks concerning the grasping and the transportation thereof.

Referring particularly to Figs. 1 to 7 it will be noted that the lining of a Martin-Siemens crucible can be made according to the invention, with a few suitably shaped blocks 1, spaced by blocks 1 comprising the charging doors 2, all of them extending for the whole height of the crucible between the bottom and the vault.

According to the invention, the bottom and the vault of the crucible can be constructed with a few large dimensioned blocks, the blocks 3 for the formation of the bottom being directly laid upon a suitable supporting surface 4 while the blocks 5 (Fig. 2) constituting the vault are advantageously made as ashlars that are inserted into a peripheral carrying armature formed by a steel frame 6 or the like.

As it can be seen from Figs. 1 to 7, the wall blocks 1, 1', as well as the bottom blocks 3, are obtained by compressing succeeding layers of suitable loose material,

as it will be better specified hereinafter, into special molds so that said layers are perpendicular to the surfaces of the lining or of the bottom exposed to the fire. A similar arrangement is adopted for the vault blocks. The presence of this Stratification is clearly indicated in Fig. l by the shading 7.

It is suitable, especially as concerns the vault blocks, that these blocks be provided with a metal reticular reinforcing frame incorporated into the blocks, some parts of said frame projecting from the blocks so as to form attaching eyes 8 to form means for interconnecting the blocks or for interconnecting the blocks and the armature to the furnace with bars 9 passing through holes in appendages 6' of the armature 6. Said attachment eyes can be also very useful in the transportation of the blocks into the furnaces wherein they are to be applied.

A particular way of making this reinforcing frame is specifically shown in Fig. 6 for are furnace vault blocks. Accordingly, the reinforcing frame is constituted by two peripheral round bars 1010', which are interconnected at the corners by diagonal bars 11 connecting them to corner bars 11, the outer element 10 of the frame being provided with eyes 8.

Fig. 5 shows the assembly of a group of blocks 12 of the kind shown in Fig. 6 for constituting the vault of an arc furnace together with a polygonal center block 13 having a number of sides corresponding to the number of blocks 12 forming the vault; in block 13, of course, there will have to be provided the openings for electrodes 14.

The same identical arrangement can be used for forming the bottom of arc furnaces by inverting the position of the blocks 12 so as to dispose them with their inclined face 12 upwards and omitting the openings for the electrodes in the polygonal center block.

Figs. 3 and 4 show two constructional modifications of vault blocks capable of being applied to substantially parallelepipedic blocks such as those shown in Fig. 2, for constituting Martin-Siemens furnace vaults, as well as to trapezoidal section blocks such as those shown in Fig. 6 for the construction of arc furnace vaults. It appears clearly that the same arrangement can be employed also for bottoms of Martin-Siemens furnaces or are furnaces, by inverting the position of the blocks in relation to the armature 6. The blocks may either decrease in thickness from the periphery towards the center as shown in full lines in Fig. 3 or have a uniform thickness as indicated in dash-and-dot lines in Fig. 3, and in full lines in Fig. 4, or increase in thickness towards the center as indicated in dash-and-dot lines in Fig. 4.

According to the invention so far described, the stratification 7 of the blocks, besides being perpendicular to the lined surfaces, is also perpendicular to the alignment direction of the blocks, irrespective of the fact that said alignment may be rectilinear or curvilinear.

There is no departure from the scope of the invention, when such a Stratification, while being perpendicular to the surfaces to be lined, is not parallel to the direction of the blocks alignment, as it is the case in Fig. 7 in which there is schematically shown a lining ring 7 for a Bessemer converter, which ring is obviously appliable also to cupola furnaces.

To manufacture lining blocks of the aforementioned type, molds are used, preferably of metal such as the one shown in Fig. 8 that may comprise four fiat plates 15 connected together by any means and placed on a work table into which the material for the block is tamped in superposed layers 7. It is possible to insert between the layers pieces of strip or iron plate connected with the reinforcing frame disposed beforehand in the mold so as to reinforce the mass of the block.

Fig. 8 relates to the simplest case of parallelepipedic blocks. In the case of blocks differing from the parallelepipedic form, it will be sufiicient to correspondingly shape the walls 15 of the mold, or to insert into a parallelepipedic mold, before tamping, counter shapes of wood or other suitable material. The withdrawn blocks can be suitably enveloped into a thin metal sheet for their better preservation if they are not immediately used.

In view of the very large dimensions of these blocks, it is necessary to provide means for easily grasping them for transportation purposes. This can be done in various ways:

According to Fig. 8, for instance, in two of the opposite plates 15 of the mold, holes 16 are provided through which a bar can be made to pass during the tamping operation, which bar causes holes 16' to be formed in the block, into which holes may temporarily be introduced bars for transporting the blocks. Said bars can also be inserted in a permanent way in the block, as shown at 17 in Fig. 9, which shows a wall lining block in the face, which is to be located against the furnace wall, are provided depressions 18 near the heads of bars 17 to easily slip out the block sustaining cable when installing the blocks. To the same purpose can serve end eyelets 8' of rods 19' extending from a base frame 19 of the block and crossing the block in the direction of its height, as shown in Fig. 10; this construction relates to a parallelepipedic block having curvilinear walls.

Fig. 11 shows a grasping means for the blocks completely external and made of two metal yokes 20 inserted in grooves 20 in the lower edges of the block and provided at their upper portions with eyes 20". Instead of these yokes peripheral metal strip bands 21 as illustrated in Fig. 12 may be used and are arranged so as to permit the introduction of a cable between the upper part 22 of the block and the bands also, shaped strips 23, as illustrated in Fig. 13, adapted to allow for the slipping out of the cable from below and from the side located against the furnace wall, can be used.

For compounding the blocks any material may be provided which has a convenient degree of refractoriness, together with a cementing substance. it is possible to use, for example, dolomite with coal tar or pitch; stabilized or semistabilized dolomite, chromite magnesia mixtures; chromite-magnesia-dolomite mixtures, dolomitic mixtures with addition of kaolin, bauxite, talcum, ferrous scale, alumina, silicious and silico-alurninous mixtures; to the coal tar and pitch small quantities of alkali silicates of molasses and other organic refractory binders can be conveniently added.

The size of the blocks will naturally vary according to the size and parts of the furnace to be lined and to the nature of the furnace. In practice, said dimensions may vary within limits corresponding to a variation in weight of the blocks between 50 and 2000 kgs., in exceptional cases up to 8000 kgs. this being but an approximate indication of the limits of the Weight variation of said blocks, and in no way being restrictive of the field of employment of the invention.

It is evident that the form of the blocks is to be established only in relation to the nature of the surfaces of the furnace to be lined and that it may therefore vary within the widest limits.

The practical usefulness of the furnace lining system forming the object of the invention is made evident by the following example:

Referring to a 20 ton Martin-Siemens furnace, for the construction of the bottom wall and of the wall where the doors are located, approximately 20 tons of magnesite bricks, 30 tons of silica bricks, 5 tons of chromite bricks are employed for the laying of which about 500 man-hours are usually necessary.

The same constructional work of the two above mentioned longitudinal walls, done according to the new proposed method, requires 45 tons of prefabricated blocks that can be placed with about 50 man-hours with a saving of about 40%.

Furnace bottoms are generally rebuilt every 10 months and for this job consecutive hours of 15 working men are required, whereas with the prefabricated blocks the 5 bottoms can be constructed with the Work of 4 men for 12 hours.

Besides the advantage deriving from the cheaper cost of the lining, there is therefore the other and perhaps more important advantage of a much shorter period of time during which the furnace is idle.

Having thus described my invention, what I claim and desire to protect by a Letters Patent is:

A refractory structure for the Walls, bottom or roof of a steel fusing furnace, at least partially formed of pre fabricated blocks of large size, each block consitituting a complete section of the structure and having the same form and thickness as the portion of the structure it forms, each of said blocks being composed of a bonded mass of incoherent refractory material strongly compressed into superposed thin layers with each layer extending the entire length of the block section and perpendicular to the face of the block forming the inner surface of the furnace, a

References Cited in the file of this patent UNITED STATES PATENTS 348,443 Anderson Aug. 31, 1886 1,448,684 Beecher et al Mar. 13, 1923 1,570,538 Thomas Jan. 19, 1926 1,624,386 Betts Apr. 12, 1927 2,510,352 Sklenar June 6, 1950 2,527,063 Heuer Oct. 24, 1950 2,684,842 Crespi et a1. July 27, 1954 FOREIGN PATENTS 665,551 Great Britain Jan. 23, 1952

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