US2686666A - Hearth cooling means - Google Patents

Description

Aug. 17, 1954 B. E. TAU 2,686,666

HEARTH COOLING MEANS Filed Feb. 17, 1950 g- 5 INVENTOR.

BRUCE E. 72w, DECEASED, 55 CHAR/TY B. 7Zw, Exscurmx.

/ ATTORNEYJ Patented Aug. 17, 1954 UNITED STATES PATENT OFFICE HEARTH COOLING MEANS Application February 17, 1950, Serial No. 144,606

Claims.

The present invention relates to improvements in hearth cooling means.

More particularly, the present invention relates to improved means for cooling the hearth wall of a metallurgical furnace and especially the hearth wall of a blast furnace.

In practice, hearth walls are normally constructedof a thickness upwards of 30 inches. Furnaces taken out of service even long before the termination of a general lining campaign are frequently found to have a remaining hearth wall thickness of approximately inches, indicating that the hearth wall disintegrated early in its career to a most undesirable extent. So thin a hearth wall introduces an element of danger because of the fact that a stoppage or failure of the water flow through a cooling element or even through one component thereof might readily lead to local overheating and further thinning of the already thin Wall so as to present the imminent hazard of a break-through of molten iron and slag.

The present invention provides an improved hearth cooling means for a metallurgical furnace hearth wall which restricts the interior temperature of the hearth wall sufficiently to prevent undue thinning thereof.

More particularly, the present invention provides a metallurgical furnace hearth wall comprising: a main inner vertical extending wall r lic part of the circumferential portion having cooling fluid means formed therein and metallic fins extending radially inwardly therefrom to a point short of the outer periphery of the main vertical extending inner wall portion, the refractory part of the circumferential portion comprising molded refractory material disposed inwardly of the metallic part, the molded refractory filling the spaces between the fins and intimately contacting the metallic part of the circumferential portion including the fins and intimately contacting the outer periphery of the main vertical extending inner wall portion.

An object of the present invention is to provide improved hearth cooling means for the hearth of a blast furnace or the like which will raise the thermal conductance and reduce the objectionable heat gradient between the cooling element and the hearth wall.

A further object is to provide improved cooling means which has extended area of contact.

2 and improved intimacy of contact with the hearth wall.

A further object is to provide improved cooling means having portions extending into spaces between the bricks at the exterior of the hearth wall.

A further object is to provide improved cooling means having portions which conform closely to the adjacent surface contours of the bricks at the exterior of the hearth wall.

A further object is to provide hearth cooling means well adapted for practical commercial service.

Further objects will appear as the description proceeds.

Referring to the drawings- Figure 1 is a diagrammatic view illustrating in horizontal section a blast furnace showing the hearth thereof;

Figure 2 is a vertical sectional view taken along the plane indicated by the arrows 2--2 of Figure 1;

Figure 3 is a view in elevation of a cooling element according to the present invention, said view showing the inner side of said element, i1- lustrating refractory members, said figure being shown in lvlercators projection, that is, with the curved inner surface of the cooling element developed into a plane surface;

Figure 4 is a sectional view taken along the plane indicated by the arrows 4-4 of Figure 3;

Figure 5 is a sectional View on an enlarged scale taken along the plane indicated by the arrows 55 of Figure 4; and

Figure 6 is a sectional view on an enlarged scale taken along the plane indicated by the arrows 6-45 of Figure 5.

According to the present invention, the first rank, or outer course, of refractory members which are to comprise the hearth wall are to be incorporated into the structure of the metallic cooling elements, as by casting the metal of said cooling elements around the partly spaced refractory members so as to envelop each member on five surfaces with intimately contacting metal which is integral to that of the cooling element.

The inner surfaces of these cast-in refractory members are disposed so as to present brick faces to the outermost bricks of the rest of the hearth wall, thereby permitting the thermally conductant clay-and-water grout jointing between brick and brick; an improved thermally conductant joint between metal and brick having been secured by the means described in the paragraph next above.

The bricks are preferably cast edgewise or endwise into the metal so as to secure a maximum of brick-to-metal surface contact. In this manner, when using bricks of the dimensions commonly employed in blast furnace construction, the area of brick-to-metal contact is at least five times the area of contact heretofore secured in previous construction, so that the thermal conductancy between metal and brick enjoys at least a five-fold improvement over that obtaining to previous construction. Indeed, the improvement in thermal conductance effected by the construction which is the embodiment of this invention, is of even greater degree because of the much greater intimacy of contact secured by the procedure of casting the metal of the stave around the brick, as compared to the casual point-contact existing in previous construction.

Furthermore, the cast-in bricks are disposed with their long dimensions vertical, with their long, narrow faces presented to the balance of the hearth wall, so that the grouted joint therebetween may be of minimum thickness radially of the hearth wall.

Referring to the drawings, the hearth of a blast furnace is indicated generally by the numeral I0, which hearth is provided with the cylindrical wall ll providing a receptacle for molten metal. Surrounding the hearth Ill and the lower portion of the wall II are a plurality of metallic cooling staves I2I2 disposed in side by side relationship circumferentially with respect to the hearth l and the wall ll. Embedded in said staves |2|2 are pipes l3l3 connected together to provide a circuitous route, or circuitous routes, for cooling water.

Bricks, or other refractory members, which, in effect, comprise the outer course of bricks of the hearth I 0 and wall I l are indicated by the numerals |4l4. These bricks may be standard arch bricks, key bricks, or wedge bricks; that is, they may be standard shapes tapered on two opposite faces; or they may be bricks of special shape, tapering on more than two opposite sides. The particular bricks chosen for illustration approximate the shape of a frustum of a regular quadrangular pyramid; that is, a polyhedron whose bases are rectangles symmetrically disposed .with respect to each other. In any event the bricks l4--l4 are oi such shape and are disposed in such a manner as to secure, when cast into the metal of the staves I 2l2, metallic intrusions |5-l5 extending between adjacent bricks I i-44, whereby intimate contact is provided between the cooling staves l2-l 2 and the bricks I4i 4.

Since the metallic intrusions I5-I5 surround the cast-in bricks i4l4 on four sides, and since the body of the cooling staves l2--l2 contacts said cast-in bricks on their fifth sides, and, fur thermore, since bricks Hl-l4 are cast into the metal edgewise or endwise as previously recited and as shown in Figures 4, 5 and 6, the area of brick-to-metal contact is at least five times the area of contact secured in previous constructions wherein the bricks adjacent to the staves are laid edgewise or endwise thereto, with only one of the smaller area faces in contact with the staves. By reason of this five-fold extension of contact area alone the thermal conductancy between the hearth wall II and the cooling staves I2 is increased five-fold.

Bricks l6|6 are the innermost bricks (shown fragmentarily) of the hearth wall, and are bonded to the cast-in bricks I i-i4, with fireclay grout l'l-ll just as they (bricks Iii-l6) are bonded to one another and to the other bricks (not shown) of the hearth wall, said grout joint having a thermal conductivity but little less than that of the brick itself, as previously recited.

Because of the greatly improved intimacy of contact and because of the increase in contactarea between the cast-in bricks l4-i4 and the metal of the cooling staves 5 2-42, the objectionable heat gradient between the outer course of the outer wall and the cooling element (according to common practice) is greatly reduced.

As the result of the improved degree of thermal conductancy between hearth wall It and cooling staves l2l2 arising only from the five-fold increase in area of contact surface secured by the means herein disclosed and described, as compared with common practice, and even discounting the beneficial efiect of the greater intimacy of said contact, the increased heat fiow from wall to cooling staves is such as to hold the inside surface temperature of the wall to or below the critical temperatures of between 2350 and 2400 degrees Fahrenheit, while maintaining a wall thickness of approximately 20 inches, as compared with about 10 inches of wall thickness as commonly is the case.

With the additional benefits to thermal conductancy residing in the factor of greater intimacy of contact between brick and metal, the preservation of more than 20 inches of wall thickness is indicated.

A hearth wall 20 inches or more in thickness greatly decreases the hazard of break-through of molten iron and slag, as compared with a hearth wall only 10 inches in thickness.

According to the invention as above described, the bricks |4l-l have been cast into the metal of the cooling staves lZ-IZ. A similar result could be obtained if the cooling staves are cast with fin-like projections forming a grid having pockets and if the interstices in the grid are filled with material such as a refractory Gunite which is molded into said pockets and which due to the process of application, adheres intimately to the metal.

A further advantage of the construction of blast furnace hearth cooling staves as herein described and illustrated, is that said staves, armored, as it were, with cast-in refractory, constitute an effective last line of defense against a break-through of molten iron and slag even though the rest of the refractory hearth wall were completely destroyed.

Though a preferred embodiment of the present invention has been described in detail, many modifications will occur to those skilled in the art. It is intended to cover all such modifications that fall within the scope of the appended claims.

What is claimed is:

l. A metallurgical furnace hearth wall comprising: a main inner vertical extending wall portion forming with the bottom of said furnace a collecting zone for molten metal and slag; and a circumferential outer wall portion, part being metallic and part being refractory, the metallic part of said circumferential portion having cooling fluid means formed therein and metallic fins extending radially inwardly therefrom to a point short of the outer periphery of said main vertical extending inner wall portion, the refractory part of said circumferential portion comprising molded refractory material disposed inwardly of said metallic part, said molded refractory filling the spaces between said fins and intimately contacting the metallic part of said circumferential portion including said fins and intimately contacting the outer periphery of said main vertical extending inner wall portion.

2. The hearth Wall of claim 1 wherein said cooling means comprises pipes adapted for having cooling fluid flowed therethrough.

3. The hearth wall of claim 1 wherein every portion of the outer peripheries of said pipes contacts the metal of said metallic part of said circumferential portion.

4. The hearth wall of claim 1 wherein said fins are shaped and joined so as to form a frustum of a pyramid.

5. The hearth wall of claim 1 wherein said metallurgical furnace wall is a blast furnace wall.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,514,776 Menke Nov. 11, 1924 1,732,514 Hunter Oct. 22, 1929 1,900,007 Bailey Mar. 7, 1933 1,900,443 Harter Mar. 7, 1933 1,909,448 Bailey et a1 May 16, 1933 2,053,127 Biggs Sept. 1, 1936 2,256,179 Thompson Sept. 16, 1941 FOREIGN PATENTS Number Country Date 292,959 Great Britain Sept. :12. 1929

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