US3831914A

US3831914A - Metallurgical furnace

Info

Publication number: US3831914A
Application number: US00423575A
Authority: US
Inventors: R Zimmermann
Original assignee: Koppers Co Inc
Current assignee: Raymond Kaiser Engineers Inc
Priority date: 1972-12-20
Filing date: 1973-12-10
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

A novel metallurgical furnace with a cylindrical shell and a contoured hearth is disclosed in combination. The cylindrical shell is lined with different refractory materials of uniform thickness, and the contoured hearth comprises a crowned sole plate, such as a dished head, covered with stepped refractory bricks. A plurality of columns engage a foundation cap plate, and a plurality of cooling water sprays cool the sole plate.

Description

United States Patent [191 1111 3,831,914 Zimmermann Aug. 27, 1974 [54] METALLURGICAL FURNACE 2,683,032 7/1954 Hartman 266/43 2,733,913 2/1956 Mercer 266/43 1 Inventor! Robe" Zlmmmann, Plttsbufgh, 2,859,030 11/1958 Snyder 266/32 3,378,249 4/1968 French et a1 266/32 Assigneez pp p y, Inc, Pittsburgh 3,612,501 10/1971 Berczynskl 266/32 X Primary Examiner-Gerald A. Dost [22] Flled' 1973 Attorney, Agent, or Firm-Sherman H. Barber; Olin E. [21] Appl. No.: 423,575 Williams; Oscar B. Brumback Related U.S. Application Data [63] Continuation-impart of Ser. No. 317,099, Dec. 20, ABSTRACT 1972 abandoned A novel metallurgical furnace with a cylindrical shell and a contoured hearth is disclosed in combination. [52] U.S. Cl 266/25, 266/32, 2266642236, The cylindrical Shell is lined with different refractory [51] Int Cl Czlb 7/10 materials of uniform thickness, and the contoured hearth comprises a crowned Sole plate Such as a [58] new of Search 266/24 43 dished head, covered with stepped refractory bricks. [56] References Cited A plurality of columns engage a foundation cap plate, and a plurality of cooling water sprays cool the sole UNITED STATES PATENTS plate. 2,052,928 9/1936 Harris 266/32 2,418,742 4/1947 A new et a1 266/43 9 Claims, 11 Drawing Figures mimmwczmu SHEET t (I 4 FIG. 1/

METALLURGICAL FURNACE CROSS REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION The present invention relates to metallurgical furnaces and, more particularly, to blast and cupola-type furnaces for producing molten iron.

The trend in metallurgical furnace design, especially blast furnace design, is to increase the hearth diameter and to increase the blast pressure. In a blast furnace having a hearth diameter as large as, say, 50 feet, and a blast pressure as high as 60 pounds per square inch, there are many problems that must be solved before such a blast furnace can be operated satisfactorily.

The flow of molten iron and slag, when the fumace is tapped, is one such problem, and the prevention of a blow through at the increased blast pressure is another related problem. By no means are these the only problems, but for them my invention has a solution. The erosive wear of the hearth lining by the removal of the liquid products is another problem that my invention solves. My invention also minimizes heat losses and dust losses; both losses being present to a greater or lesser degree in conventional blast furnaces.

To some furnace designers it is axiomatic that the liquid contents of the furnace should be as nearly a minimum and as nearly a constant quantity as is possible at all times. However, because of the very high blast pressure, in order to prevent the blast from blowing through the tap hole, there must be a liquid metal seal and a liquid slag seal in the furnace above the inside end of the iron hole, plus a pressure drop in the tap hole that is great enough to prevent the blow through. Should a blow through occur, it would mean that the blast pressure within the furnace would have to be lowered to allow enough molten iron and slag to collect in the hearth to again form a liquid sea]. This upsets the working of the furnace, and the tap hole in use probably would have to be closed and another tap hole would have to be opened to continue using the fumace.

In blast furnaces having a flat hearth as large as, say, 50 feet in diameter, raising the height of the effective slag-iron interface requires the accumulation and the holding of a very large tonnage of iron and slag in the hearth. Such action is contrary to the axiom that the liquid contents of the furnace should be kept at a minimum and at as nearly constant volume as possible.

One solution to the problem would be to so construct a furnace and hearth that there would be a greater difference in height between the effective slag-iron interface and the inside level of the tap hole without greatly increasing the volume of the liquids in the hearth. Further, with this provision, there would be less change for a blow through," and less likelihood of the necessity of having to run both iron and slag through the same tap hole during the greater part of a cast, which decreases the severity of wear of the refractory forming the tap hole.

SUMMARY OF THE INVENTION The invention includes a cylindrical shell of a metallurgical furnace, divided into zones and each zone is separately cooled. The hearth is also divided into zones cooled separately. The shell is lined with refractory that is selected for its resistance to the deteriorating wear conditions in the furnace. The hearth is contoured, having a generally conical cross sectional shape which is cooled by water sprays impinging against the underneath side of a hearth plate.

For a further understanding of the invention and for features and advantages thereof, reference may be made to the following description and the drawings which illustrate an embodiment of equipment in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic view of a form of standardized blast furnace as known from the prior art;

FIG. 2 is a schematic view, in a vertical cross section, of a metallurgical fumace in accordance with my invention,

FIG. 3 is a schematic view, in vertical cross section, of a modified lower portion of the furnace of FIG. 2;

FIG. 4 is a view along line IV-IV of FIG. 3;

FIG. 5 is a view of one quadrant of a structure like that of FIG. 4, but at an enlarged scale;

FIG. 6 is a view of a portion of FIG. 3 showing one arrangement of hearth bricks;

FIG. 7 is a view of a portion of FIG. 3 showing another arrangement of hearth bricks; and

FIGS. 8-11 are views of typical refractory hearth brick shapes.

DETAILED DESCRIPTION Referring to the drawings, FIG. 1 illustrates a form of metallurgical furnace 3 that is known from the prior art and that is described in an article by W. Feldmann that was published in STAHL UND EISEN (vol. 63, pp. 597-598, 1943). In such article, he refers to a previous article (1941) by E. Cotel that describes the features and advantages of a blast furnace that does not have the conventional double-cone shape; the preferred shape being nearly cylindrical. The furnace shape preferred by Cote] is self-supporting; which is to say, the furnace jacket is continous from the hearth to the throat. The jacket is cylindrical, beginning at the boshes and up to the shaft, while only the lower part is enlarged conically to strengthen the brickwork, and to assist in obtaining a uniform run-off of cooling water.

Although with this external shape, the inner lines of the furnace 3 remain more or less the same as before. It will be noted from FIG. 1, that the lines of the shell portion 7 above the level A-A and below the level BB are frusto-conical, with the larger diameter located at level A--A. Above the level BB, the lines of the fumace shell portion 7 are frusto-conical, with the smaller diameter at the throat at the level C--C. Between AA and BB, the lines of the shell portion 7 are cylindrical.

Internally, the refractory lining portion 9, below the level BB, increases in thickness, as shown, but the refractory lining portion 10, above the level BB, is of substantially uniform thickness.

FIG. 2 illustrates schematically a metallurgical furnace 11 in accordance with my invention includes a cylindrical outer shell 13 that is free-standing and is supported on the ground, or on a suitable concrete base 15. The cylindrical, free-standing shell 13 has a hearth portion 17 and a top structure or gas off-take belt 19.

The shell 13 is made cylindrical in order to simplify construction, to reduce construction costs, to reduce lining wear, to reduce dust losses, and to decrease fuel consumption.

The cylindrical shell 13 is lined with different types of refractory material 21a, 21b, 210, selected to suit the process conditions that occur within the furnace at different levels. Each different type of refractory material 21a, 21b, 21c, is cooled in the most effective manner, or to an optimum degree, as mentioned hereinafter. The refractory lining may be cooled by spraying water onto the shell 13 in certain zones, in conjunction with aluminum ribs (not shown) that are embedded in the refractory material to aid in conducting heat from the refractory lining material to the shell 13. External spray cooling of the shell 13, if employed, may be more effective than evaporative cooling. In some instances, an insulating layer may be interposed between the evaporative cooling units and the shell as is conventional from known prior art structure.

Because the shell 13 is cylindrical and, thereby, free of mechanical supporting attachments, such cooling arrangements as are adopted can be designed for their cooling function only without making comprises therein to suit interfering structural members used in conventional furnace designs.

Zone separating rings (not shown) of a metallic nature located in the lining may or may not be employed for the added function of assisting in supporting the refractory lining material.

Between the top of the steel shell 13 and the top structure 19 there is an expansion joint 23 which is necessary to accommodate thermal stresses in the shell 13 and the gas off-take belt 19.

The cylindrical steel shell 13 is provided with a plurality of surrounding

cooling water conduits

25, 27, 29 to suit the zone cooling requirements. Each such conduit carries a plurality of spray nozzles 31 or even a plurality of apertures from which cooling water flows onto the outer surface of the steel shell 13 to cool it according to zonal requirements. Suitable gutters 33 are installed on the shell 13 about where shown to collect the water that flows down the outer surface of the shell. Drain lines may be provided for each gutter 33 to carry away the collected water if necessary or desirable.

The top structure or gas off-take belt 19 includes a circular continuous conduit 35 that is shaped about as shown in FIG. 2 to fully realize the beneficial effect of reduced top gas velocities on the dust losses from the wide top, inherent in the cylindrical design. The structure 19 may also incorporate the functions of the expansion joint 23. A downcomer (not shown) would be installed to carry the off-gases away in the usual manner.

A number of tubular support members or legs 37 (only one is shown) are connected to the off-gas conduit 35 and they connect at the lower end to the ground or to the foundation 15. These tubular legs 37 support the top structure or gas off-take belt 19 relative to the cylindrical shell 13.

The structure 19 also includes a filling system 39 that may be similar to that shown and described in US. Pat. No. 3,693,812, that issued Sept. 26, 1972, or it may be a conventional bell and hopper, or valve and hopper, top-filling structure, though these types of structures are not entirely suitable for large furnaces that have no adjustable stockline armor or other provision for distribution of stock. Around the top of the structure 19 there may be a plurality of stock level probes 41 which are conventional. The structure 29 also carries dirty gas bleeders 43 with bafiles 45 located within the top structure about where shown. Also, an explosion valve 47 with a similar baffie 49 is installed when local existing conditions permit the installation of such equipment.

The lower portion of the cylindrical, free-standing shell 13 is fitted with a conventional bustle pipe 51 and conventional tuyeres 53.

The hearth portion 17 of the metallurgical furnace 11 includes an upwardly contoured, domed portion 55 of refractory material, described, hereinafter, that is centrally located with respect to the circular cross section of the shell 13, and that forms a circular channel 57 for holding molten iron 59. A conventional iron tap hole 61 is provided in the refractory portion 21a, as shown in FIG. 2. The tap hole 61 is located so as to terminate internally of the furnace 11 at about the bottom level of the circular channel 57. Although, only one tap hole is shown, in large furnaces many tap holes will be provided.

The hearth portion 17 also includes a supporting sole plate 63 that can be made as an inside, as shown, or outside dished head of conventional form. The sole plate 63 is spaced apart from a foundation cap 65, that is or may be slightly crowned to facilitate drainage of coolant fluid therefrom. The sole plate 63 may be supported on the cap 65 by any suitable means, such as by a plurality of short columns 67. Thus, the entire weight of the structure above the sole plate 63 is transmitted to the foundation cap plate 65 by the columns 67. The columns 67 may, if preferred, be replaced by a suitable grillage structure or radial spacers, or the like. A system of radially arranged, removable cooling water spray conduits 69, equipped with a plurality of suitably graded spray nozzles 71 so that the quantity of cooling water can be suited to the respective zonal requirements, is disposed in the space between the sole plate 63 and the foundation cap 65, as shown in FIG. 2.

The radial cooling water conduits 69 are connected to

conduits

75, 77 carrying cooling water by means of flexible hoses 73, or the like. Because the foundation cap 65 is slightly crowned, the cooling water from the sprays drains readily into a trough or gutter 79 that encircles the foundation cap 65, as shown. Of course, cooling water in the gutter or trough 79 drains away in a conventional manner.

FIG. 3 illustrates a modification of the lower or hearth portion of the fumace of FIG. 2. Similarities between the modified embodiment of the invention of FIG. 3 and that of FIG. 2 have the same reference numerals.

In the modified embodiment of the invention shown in FIGS. 3 and 4 there are a plurality of cooling

water conduits

81,83,85 that encircle the shell 13. These conduits receive cooling water from a convenient source of supply, not shown.

Between the sole plate 63 and the foundation cap 65 there are a plurality of conduits connecting to spray headers having generally a cruciform shape. The underneath surface of the hearth sole plate 63 is figuratively subdivided into three cooling zones, A, B and C; zone A being a circular zone at the center of the sole plate, and the other two zones B, C being annular and disposed outward of Zone A.

The sole plate surface of Zone A is cooled by sprays in the four cruciform headers 87, as arranged in FIG. 4. The headers 87 are connected to the cooling water conduit 81 by conduits 89, as shown in FIG. 3.

The sole plate surface of zone B is cooled by sprays in the eight cruciform headers 91, as arranged in FIG. 4. The headers 91 are connected to the cooling water conduit 83 by conduits 93, as shown in FIG. 3.

The sole plate surface of zone C is cooled by sprays in the twelve cruciform headers 95, as arranged in FIG. 4. The headers 95 are connected to the cooling water conduit 85 by conduits 97, as shown in FIG. 3.

Between the several cruciform headers shown in FIG. 4, a plurality of columns, with centers indicated by the several crosses 99, extend between the sole plate 63 and the foundation cap 65, as suggested in FIG. 2.

The number and the spacing arrangement of the cruciform spray headers depends largely upon the size (diameter) of the hearth and the area of the sole plate that is cooled by the sprays. The number of cruciform spray headers in one arrangement are shown in FIG. 4.

FIG. 5 illustrates the number and a typical arrangement of cruciform spray headers in one quadrant of a circular hearth of relatively large diameter, say fifty feet. It will be noticed that in Zone A of the whole hearth -of FIG. 5 there would be 8 cruciform spray headers 101; and in zone B, there would be 32 cruciform spray headers 103; and in zone C there would be 64 cruciform spray headers 105. Each cruciform header carries at least four spray nozzles.

In FIG. 5, like in FIG. 4, crosses 107 indicate the centers of supporting columns 67 that extend between the sole plate 63 and the foundation cap 65.

FIG. 6 illustrates one arrangement of refractory bricks comprising an contoured domed portion 55a. In FIG. 6 the centerline portion of the bricks are stacked three high. In FIG. 7, which also illustrates an arrangement of refractory bricks in another contoured dome portion 55b, the bricks are only stacked two high.

FIGS. 8, 9, l0 illustrate typical stepped refractory bricks 109, I11 113, respectively, used to make the contoured dome portions 55a and 55b. The bricks 111, 113 are stepped once, in FIGS. 9, 10, and the bricks 109 are stepped twice in FIG. 8. The twice-stepped bricks of FIG. 8 are used where shown in FIG. 6 and in FIG. 7; otherwise the bricks comprising the contoured dome portions 55a, 55b are once-stepped in shape and are similar to those shown in FIGS. 9 and 10.

The top surface of the refractory bricks forming the top of the contoured dome portions, like that shown in FIG. 9, is a warped surface, geometrically speaking.

Adjacent the outer edges of the contoured dome portions 55a, 55b, where they meet the side walls of the furnace proper, refractory bricks 115 have a more conventional shape as suggested in FIGS. 6 and 7.

On the centerline of the contoured dome portions 55a, 55b, at the bottom thereof, there is a single frustoconical keystone-type refractory brick 117 of the type shown in FIG. 11.

Since the operation of conventional blast furnaces is well known to those skilled in the art, and since the operation of the metallurgical furnace of my invention is not unlike that of the conventional blast furnace, it is deemed to be unnecessary to describe the operation of my furnace, except to say that during the period when my furnace is in operation, the cooling arrange ment described herein would be in operation to keep the hearth, and particularly the sole plate, at a reasonable temperature.

While my furance is operating, it is desirable that the volume and rate of flow of cooling water emitted by the several spray nozzles be so regulated that a thin crust I 19 of solid iron is allowed to form and remain in place on top of the refractory bricks of the contoured dome portions to protect them from excessive erosion in service.

From the foregoing description of my invention, those skilled in the art should recognize many important features and advantages of it, among which the following are particularly significant:

That the shell and refractory lining of my metallurgical furnace may be self-supporting, and no conventional-type columnar support structure attached to the shell is required.

That the refractory lining is zoned, which means that in selected zonal surface areas, a particular type of refractory is used to resist the chemical or mechanical actions that affect the lining in those particular zones;

That each such zone may be cooled to suit the particular requirements of the refractory material making up each zone;

That the thicker lining of conventional blast furnaces, which is used partially for mechanical support support purposes and which creates a cooling problem, is not found in my furnace structure. Hence, the cooling problem resulting from use of very thick lining is avoided;

That the cooling plates or coolers of conventional blast furnace linings may be advantageously omitted from my metallurgical furnace;

That the hearth structure is spray cooled in zones with removable sprays, and the external surface of the shell is cooled by sprays as needed in each zone, by a closed system with attendant auxiliary water quality control equipment, results in more effective cooling of the furnace shell lining and hearth, whereby the refractory material of the hearth may always be protected from erosion by a layer of iron, the product of the furnace;

That the bustle pipe need not hug the furnace shell as it does in conventional blast furnaces; but, it may be shell-supported or not, as convenience dictates; and

That the top structure is more advantageously supported by an external structure than by the furnace shell, as in conventional practice.

Although the invention has been described herein with a certain degree of particularity, it is understood that the present disclosure has been made only as an example, and that the scope of the invention is defined by what is hereinafter claimed.

What is claimed is:

I. In a metallurgical furnace having a cylindrical shell, the improvement comprising:

a. refractory materia lining the interior of said shell, with said shell and the refractory lining material being divided into zones with a different type of refractory material being in each said zone;

b. means for cooling said zones of said shell as required by the characteristics of the refractory material in the zones of the lining of said shell;

c. a contoured hearth comprised of stepped coacting refractory shapes having a greater thickness at the center than at the juncture of said hearth with the fractory material selected for their resistance to lining of said shell, said hearth being disposed in wear conditions at the particular level of said furspaced-apart relation to a support structure; and nace;

(1. means for cooling the undersid Surface of Said b. a dish-shaped sole plate connected to said shell hearth. and spaced apart from a supporting base;

The invention of Claim 1 Whereifli 0. means disposed between said sole plate and said a. a plortion of said refractory shapes have two steps; base f maintaining them in Spaced apart relation;

I). another portion of said refractory shapes have one d. a hearth Comprising a contoured arrangement f step- 10 stepped refractory shapes supported on said sole 3. The invention of claim 2 including:

a. a keystone like refractory shape coating with said stepped refractory shapes.

4. The invention of claim 1 wherein:

a. said means for spray cooling said hearth includes 1 a plurality of conduits carrying spray nozzles, said nozzles being separated into groups so that fluid emitted from each group of nozzles impinges on a selected zonal area of said hearth.

5. ln a metallurgical furnace, the improvement comprising:

a. a contoured hearth comprised of a plurality of stepped coacting refractory shapes forming a circular channel for holding the metal product of said plate; and

e. means for cooling zonal areas of said hearth.

9. ln metallurgical furnace the improvement comprising:

a. a cylindrical shell lined with different kinds of refractory material selected for their resistance to wear conditions at the particular level in said furnace;

b. a dish-shaped sole plate connected to said shell and spaced apart from a supporting base;

c. means disposed between said sole plate and said base for maintaining them in spaced-apart relation;

d. a hearth comprising a contoured arrangement of furnace. The invention f claim 5 wherein; stepped refractory shapes supported on said sole a. a portion of said refractory shapes have two steps; Plate; and

d e. means for cooling zonal areas of said hearth comb. another portion of said refractory shapes have one P I Step 1. a plurality of conduits having nozzles that emit a 7. Th i v ti n of lai 5 i l di cooling fluid over a first zonal area of said hearth, a. a keystone-type of refractory shape that coacts and with adjacent stepped refractory shapes. ii. a plurality of conduits having nozzles that emit 8. In a metallurgical furnace the improvement coma cooling fluid over a second zonal area of said prising: hearth.

a. a cylindrical shell lined with different kinds of re-

Claims

1. In a metallurgical furnace having a cylindrical shell, the improvement comprising: a. refractory materia lining the interior of said shell, with said shell and the refractory lining material being divided into zones with a different type of refractory material being in each said zone; b. means for cooling said zones of said shell as required by the characteristics of the refractory material in the zones of the lining of said shell; c. a contoured hearth comprised of stepped coacting refractory shapes having a greater thickness at the center than at the juncture of said hearth with the lining of said shell, said hearth being disposed in spaced-apart relation to a support structure; and d. means for cooling the underside surface of said hearth.

2. The invention of claim 1 wherein: a. a portion of said refractory shapes have two steps; and b. another portion of said refractory shapes have one step.

3. The invention of claim 2 including: a. a keystone like refractory shape coating with said stepped refractory shapes.

4. The invention of claim 1 wherein: a. said means for spray cooling said hearth includes a plurality of conduits carrying spray nozzles, said nozzles being separated into groups so that fluid emitted from each group of nozzles impinges on a selected zonal area of said hearth.

5. In a metallurgical furnace, the improvement comprising: a. a contoured hearth comprised of a plurality of stepped coacting refractory shapes forming a circular channel for holding the metal product of said furnace.

6. The invention of claim 5 wherein: a. a portion of said refractory shapes have two steps; and b. another portion of said refractory shapes have one step.

7. The invention of claim 5 including: a. a keystone-type of refractory shape that coacts with adjacent stepped refractory shapes.

8. In a metallurgical furnace the improvement comprising: a. a cylindrical shell lined with different kinds of refractory material selected for their resistance to wear conditions at the particular level of said furnace; b. a dish-shaped sole plate connected to said shell and spaced apart from a supporting base; c. means disposed between said sole plate and said base for maintaining them in spaced-apart relation; d. a hearth comprising a contoured arrangement of stepped refractory shapes supported on said sole plate; and e. means for cooling zonal areas of said hearth.

9. In metallurgical furnace the improvement comprising: a. a cylindrical shell lined with different kinds of refractory material selected for their resistance to wear conditions at the particular level in said furnace; b. a dish-shaped sole plate connected to said shell and spaced apart from a supporting base; c. means disposed between said sole plate and said base for maintaining them in spaced-apart relation; d. a hearth comprising a contoured arrangement of stepped refractory shapes supported on said sole plate; and e. means for cooling zonal areas of said hearth comprising i. a pluRality of conduits having nozzles that emit a cooling fluid over a first zonal area of said hearth, and ii. a plurality of conduits having nozzles that emit a cooling fluid over a second zonal area of said hearth.