US3084924A - Comolded magnesite-chromite tuyere - Google Patents

Description

April 9, 1963 H. A. MoRLocK 3,084,924

coMoLDEn MAGNESITE-CHRQMITE TUYERE |NvEN-roR HAAP/@Y 4. MUPLOCA/ April 9,` 1963 H. A. MRLocK COMOLDED MAGNESITE'CHRQIIITE TUYERE 3 Sheets-Sheet 2 Filed June 30. 1960 INVENTCR fm?" 4. Manac/r United States` Patent O Thepresent invention relates to refractory tuyeres for metallurgical furnaces, especially for copper converters and Bessemer converters. i I

A purpose of the invention is to produce a tuyere brick which will have longer service life and be more resistant v to erosion.

A further purpose is to facilitate the production of a tuyere brick by pressing and avoid the necessity of ramming.

A further purpose is to produce a tuyere -brick which will electivelysea'l against -loss of gas notwithstanding that it is made n cooperating components.

A further purpose is to produce a tuyere brick that is more resistant -to spalling at the hot end.

Further purposes appear in the the claim. t

In the drawings I have ch-osen to illustrate a few only of the numerous embodiments in which the invention may appear, selecting the forms shown from the'standpoints of convenience in illustration, satisfactory operation and clear demonstration of -the principles involved.

FIGURE l is a diagrammatic transverse vertical section of a copper converter embodying the invention.

FIGURE 2 is a fragmentary longitudinal section on the line 2--2 of FIGURE 1.

FIGURE 3 is an enlarged fragmentary portion of FIG- URE 1 illustrating the tuyeres, with the section' taken at a somewhat different point and not actually through the tuyere passage.

specification and in version or 'Bessemerizatiom air is admitted beneathth'e surface of a bath of moltenpmetallic sultides including 'copper sulde, .to remove sulphur and iron by oxidation and slagging. v

'Ihere are other similar metallurgical or chemical processes to which the invention is applicable.`

These ltwo processes and others of similar nature are usually exothermic so that a great release of heat occurs which tends to keep the bath molten without the necessity of adding additional fuel.

On the other hand, there are other reactions carriedv out in converters which are endothermic, in which case additional fuel must be introduced within the vessel to maintain the bath ina molten state. v

in both cases it is necessary that the interior of the vesseland the charge be maintained at a high temperature,'.usually in excess of 2,000" F.

v head. V

The required pressure of the admitted air or other gases In both` of the processes mentioned, theair or other gases must be admitted below the surface of the lliquid ba-th at considerable pressure to insure that su'icient volume of air will pass through the bath and promote the chemical reactions and overcome the hydrostatic pressure causes Igreat turbulence at the point where the gas enters the bath, and this turbulence is further increased at that |point by the fact that the air or other gas is tremendously heated both by the molten bath and by the chemical reactions.

The turbulence therefore imparts energy to the molten bath so that drops and splashes ofthe molten charge are expelled with great force from the surface of the bath and propelled in an upward direction in the interior of the FIGURE 4 is a fragmentary enlarged section at the cold end of the tuyere on the line 4,-4 of FIGURE 3.

FIGURE 5 is a face view of an individual'tuyere brick,

the view being in the position of the line 5--5 of FIG- URE 4.

FIGURE `6 is a fragmentary perspective of the tuyere brick of FIGURE 5.

FIGURE 6a ris a fragment of FIGURE 4 showing av variation.

FIGURE 7 is a view similar to FIGURE 3 showing a variation. v

FIGURE 8 is another view similar to FIGURE 3 showa further variation.

Describing in illustration but not in limitation and re# ferring to the drawings:

The present invention has particular relation to a furnace wall construction involving tuyeres.

Certain metallurgical processes require that air or oxygen, or air enriched with oxygen, or 'other gases be introduced into a molten bath at pressures greater than atmospheric.V

metallurgical vessel. Some of this suspended, splashed material remains molten and returns to the bath either directly or by trickling down the interior surface of the refractory lining. Some other higher melting point portions of the splashed material freezes whi-le suspended in the interior atmosphere of the vessel above the bath and these solid particles arepropelled with relatively great force against the interior of the vessel above the surface of the bath. Y

The pressure of gases and the weight of the molten liquid charge make it necessary to contain such metallurgical furnaces or vessels within a heavy outer shell of steel plate. This outer steel shell is protected on its inner surface by a lining of refractory brick or tile components.' The refractory lining of the vessel must have suilcient thermal resistance to maintain a high temperature differential between its inner or hot end in contact with the molten bath and its outer or cold end in contact with the steel shell or adjacent the steel shell. The refractory lining must also be resistant to chemical attack by the molten bath and by the reaction products formed during the processing.

The refractory lining must also have greatl resistance to rupture from thermal shock arising from fluctuations in temperature within the metallurgical vessel.

The vrefractory lining must also possess a high resistance to abrasion and erosion from turbulent molten material as e well as from particles of suspended, frozen or solid material propelled against it.

Unless all of these influences which tend to destro;r

1the refractory lining are inhibited, early failure will occur. Because the purpose of the refractory lining is to protect the steel shell against weakness from high temperature or chemical attack, it is necessary to replace the refractory lining when its original thickness has been reduced to the extent that it no longer protects the steel it will lose its strength and -the moltenbath could be expelled through a rupture in the shell, causing great danger to human life` as well as economic loss. The present invention is concerned with improving the integrity of those highly stressed areas of the refractory lining which form the tuyere.

In the prior art practice, in designing metallurgical vessels in which blowing through the lining is to occur, a point is designated which will indicate the minimum ele-` vation of the molten bath. At some point below this, a continuous opening or air passage through the refractory lining and through the steel shell is provided. Usually in practice there are a series of such openings at the same elevation, each continuing from the inner hot face of the refractory lining to the outer face of the refractory which is in contact with the inside of the steel shell and thence through holes in the steel shell to a point in the outside where suitable piping connecting to a manifold or header duct is provided, which in turn connects to a source of gas at superatmospheric pressure.

The pressurized air or gas is conducted through the opening in the shell and in the refractory lining into the interior of the vessel through the openings or tuyeres which have been described.

In order vto better understand the construction, reference is made to FIGURES l and 2. These figures show a typical furnace or converter having an outer steel shell Z0, and an interior refractory lining 21 intended to protect 'the metal shell 20, and having a charging and discharging opening 22 near the top. The furnace normally rotates to discharge.

A molten charge 23 is placed in the furnace 4and this has atop surface 24.

At an elevation below the top surface of the molten charge, tuyeres Z extend inwardly and suitably downwardly through the lining and the metallic shell to admit pressurizedair or gas beneath the surface of the bath. A header 26 along the outside of the furnace connects to the individual tuyeres by pipes 27.

By reason of the factors already described, maximum turbulence and agitation of the liquid bath will occur adjacent the inside of the tuyeres.

The maximum intensity of chemical reactions will take place at the mouth of the tuyere, and hence the maximum temperature in the vessel will occur at approximately this point.

differences in thermal conductivity through various parts By reason of the inertia of the liquid molten bath,

the zone in which the material will be splashed or ejected .from the surface of the bath will be confined to that portion of the bath contacting and close to the lining adjacent to the tuyere openings. Some portion of this ejected material will be propelled against the lining. Of this propelled portion of splashed material, a fraction will remain molten and the balance will freeze or solidify while suspended in the vessel atmosphere. That fraction whichremains molten will trickle in a downward direction along the surface of the lining and tend to wash or erode a portion of particles of the lining.

Soliditied material which is propelled against the lining will thus tend to reduce the thickness of the lining by a mechanical action, which is analogous to"sand blasting.

Although the area of the lining below the tuyeres cannot be observed during blowing, it has been found experimentally that a high rate of erosion exists in this section of the lining caused by the abrasive action of the molten liquid bath moving in contact with the refractory lining. This movement of liquid material is caused by the current created by the upwardly moving molten material.

lIt is found in practice that the zone of the lining at the tuyere and above and below the tuyere requires most frequent replacement, and this proves that itis subjected to more severe conditions than the remainder of the lining.

In FIGURE l I illustrate by a bracket 28 an area of the refractory lining above the tuyeres which is most effected by the expelled material. I also illustrate by a bracket 30 an area of the lining beneath the tuyeres which is most affected by the destructive forces. The molten and solid material expelled from the surface of the bath and propelled ,against the lining is suggested by arrow 31, it being understood that this arrow indicates a whole series of generally adjoining travel paths of Agitated and turbulent material below the tuyere is shown by curved arrows 32 The refractory brick which conltains the tuyere opening is indicated at 33.-

the refractory lining above the worn section often loses its mechanical support and falls from place. Hence any refractory lining above the tuyere which has further utility must be prematurely replaced, with corresponding economic loss and loss of the productivity of the furnace. Accordingly it 'is very desirable tolengthen the service life of the zones 28 and 30 to reduce replacement cost of the refractory lining and lessen the down time of the furnace.

There are two additional factors which contribute to rapid wear of the refractory lining.

The first of these is the formation of zones of thermal instability within the body of the refractory brick. zones result from non-linear temperature gradient between the hot faces and the cold faces of the brick. This isv due to the variations in the density of the mass of the refractory components which form the lining, creating vof the refractory. -Where the temperature difference-between Aadjacent zones is high, great differences in thermal expansion will occur, with rupture of the refractory. This rupture liberates fragments of the refractory from the hot face and they Ifall from their places into the bath and diminish the thickness of the lining. This vis a common phenomenon known as spalling.

4Another important factor which contributes to the destruction of the refractory lining -is mechanical impact.

During'the blowing period of the processing, metal, slags and other compounds may become solid or frozen at the mouth of the tuyere and adhere tightly to the rethe lining material by displacing l fractory around the periphery of the tuyere opening. In some cases these accretions combine with the refractory at the hot face by fluxing In commonpractice, an opening isprovided at the outer end of the tuyere to Iinsert a steel bar and apply a heavy impact to the outer end of the bar to force the bar through the .tuyere into the molten bath'and remove any accretions at the mouth of the tuyere and thus restore free ow o, air or-gases into the bath. This imposes a tension stress on the refractory at the end of the tuyere. 'Iherefore any factor which inhibits or lessens the lowering of the tensile strength of the refractory is desirable.

The usual practice followed in the present invention is to employ two opposite counterpart tuyere bricks 33 side by side to form the tuyere opening. Each of these bricks has a refractory body 34 and has molded therein and extending longitudinally of the brick a semi-cylindrical portion 35 which forms half of the tuyere opening. FIG- URE 4 shows two of the bricks 33 assembled to make the tuyere opening. It will be evident that while the tuyere opening is provided by` two bricks inthe form shown, it may be formed by bricks having different lines of separation, whose relative position is superimposed y' particles.

These The preferred form of the tuyere brick as shown is of wedge or key shape, provided with a relatively smaller hot shaped bricks or tiles 42 of desired character form the refractory above and below the tuyere.

It is important to develop in the tuyere and in the areas above and below the tuyere characteristics which will improve the resistance to abrasion and erosion and the tensile and abrasive strength lof the refractory close vto the molten charge.

It is also important to increase the resistance to rupture, so -that the brick will not separate into fragments and thus decrease the thickness of the lining and cause overheating and weakening of the outer shell.

In my United States Patent 2,125,192, I describe bricks which have thin steel plates in the joints, so as to form joints of iron oxide. 'This tends to retain fragmentstor spalls by the effect of the iron oxide joint.

This iron oxide joint actually has higher thermal con'- ductivity than the refractory so that a greater amount of heat is transmitted by this joint toward the outside. This tends to distribute the heat more uniformly through the thickness of the refractory so that Vthe temperature drop will be approximately linear between the hot and the cold face.

Furthermore, the heat which reaches` the outer wall or shell can be radiated without overheating the shell. This tends to reduce the effect of localized zones of abnormally high temperature.

The ow of heat through such iron oxide joints to the outside tends also to maintain the hot faoe of the refractory at a lower temperature, so that the refractory can remain reliably below the temperature of incipient fusion, and better tensile and abrasive properties are obtained, as well as better resistance to abrasion and erosion.

In accordance with the present invention, very much superior tuyeres are produced, which have greater tendency to retain spalls or fragments, and also greater heat ilow from the hot face to the cold face. Superior resistance to erosion and mechanical shock is also obtained.

In accordance with the invention, each tuyere brick 33 is composed of magnesia or a mixture of chromite and magnesia containing at least 10 percent of magnesia by weight.

I provide on the face 40 which is to adjon the cooperating tuyere brick an external oxidizable metallic plate 43 which s desirably of rhomboid form, and covers a portion of the brick at one side of the tuyere opening. I also provide an external oxidizable metallic plate 44 suitably of rhomboid form which substantially occupies the face 40 of the brick on the opposite side of the tuyere passage 35.

Secured to the external oxidizable metallic plate 43 is a U shaped internal plate 45 having a base of the U 46 united to the plate 43 as by spot welding and having arms of the U 47 extending into the refractory in comolded relation. The internal plate 4S is cut off diagonally so as not to interfere with the tuyere opening. Extending inwardly from the plate 44 are internal oxidizable metallic plates 48 and 50 each having bases of the U 51 or 52 extending along the inside of the internal plate 44 and united thereto as by spot welding, and having arms of the U 53 or 54 which extend into the refractory in comolded relation. The plates 48 and 50 are cut olf diagonally to avoid the tuyere opening.

All of the oxidizable metallic internal and external plates are suitably made of steel, including plain carbon or low alloy steel. Stain-less steel may be used as long as it is oxidizable at the temperature of use. The external and internal plates will have a thickness in the range between %4 and 1A inch and preferably about ,z to Vs inch.

The external and internal plates are formed by suitably placing them in the bottom of a mold with the plates 43 and 44 resting on the bottom of the mold and the internal plates protruding upwardly amid the mass of refractory, and then applying pressure at the face 41 against the 'face 40 so that the external and internal plates are united. to the refractory by comolding.

It will be evident that the internal plates run generally transverse to the top end of the brick and generally ra- .dially of the tuyere Ibrick. It will be evident that if desired an oxidizable metallic plate can also be applied on the face 41 of the tuyere brick, suitably by comolding.'

In some cases it is desirable to form a comolded oxidizable metallic plate on the inside of the tuyere opening and I show in FIGURE 6a a fragment of the tuyere brick which has such an oxidizable metallic plate at 55 extending longitudinally of the tuyere opening, the plate 55 suitably being integral with the plates 43 and 44.

It will be evident that it is not specifically critical in the present inven-tion as to whether the internal plates extend wholly from plates on the face 40 or wholly from plates on the face 4l, or in part from plates on the face 40 and in part from plates on the face 41. vj -It will also be evident that the comolded internal plates which are Itransverse to the hotface can extend in from other faces of the brick as desired. Y

It .will be understood that the steel plates which are on the outside and which meet in FIGURE 4 at the face 40 will oxidize and formv zones of iron oxide extending toward the cold end. This will also be true of the internal plates and the internal plates will react with the magnesia to form magnesioferrite. Thus a large number of cells will be formed and the iron oxide ribs and the magnesioferrite nbs will tend to prevent spalling and damage lfrom abrasion and Will also conduct heat outv wardly. These conducting paths yield some of their heat to the refractory mass and make the refractory mass more uniform in temperature drop, and also more readily transfer heat to the outer steel shell for radiation. This tends to reduce abnormally high hot face temperature at the tuyere.

The key or wedge bricks 42 will suitably also be provided with comolded external plates 56 and radially ex tending internal plates 57 secured thereto as shown in FIGURE 7. In this figure heat insulating spacer bricks 58 are provided between the wedge or key bricks 42 and the shell, as well as a loose refractory layer 60 which extends between the shell and the tuyere brick as well as the wedge or key bricks.

In FIGURE 8 I illustrate a somewhat diiferent construction, in which the wedge or key bricks 42 and the tuyere bricks 33 are Ihacked up by heat insulating bricks 61 which in some cases at 62 have openings to connect with the tuyeres. In this case the metallic shell 20 is reenforced at 20 adjoining the tuyeres.

In view of my invention and disclosure variations and modifications to meet individual whim or vparticular need will doubtless become evident to others skilled inthe art, to obtain all or part of the benefits of my invention without copying the structure shown, and I therefore, claim all such insofar as they rfall within the reasonable spirit and'scope of my claim.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

In a copper converter for molten metal to be blown with air introduced 'below the line of the molten metal, a housing, a refractory lining extending rthroughout the interior of the housing and tuyeres formed by cooperating tuyere brick of basic refractory of the c lass consisting of magnesia and mixtures of chromite and magnesia containing at least 10% of magnesia, said tuyere brick extending with their inner ends in the interior of the con- 'verter below the metal line and passages of said tuyeres communicating with the molten metal below the metal line through the inner ends of said brick in the converter, each said tuyere brick for-ming only a portion of a cor- 7 responding one of said tuyere passages which extends from the interior of the converter outwardly generally longitudinally of the brick forming said portion, there being an oxidizable ferrous metallic external plate cover ing the mating cooperating faces of the tuyere 'bricksv and there being oxidizable ferrous metallic internal plates extending in the interior of the refractory of said tuyere bricks adjacent to the tuyere passages and said inner ends of the brick and secured to said external plates, and said external and internal plates being in comolded relation with the lrefractory and extending generally longitudinally of the tuyere bricks.

. UNITED STATES PATENTS Morlock July 26, Heuer lan. 28, Zippler Dec. 30, Cope Ian. l, Heuer et al. May 7, Kelsey Dec. 3l,

FOREIGN PATENTS Germany lan. 28, Canada Apr. 2l,

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