US2206944A - Furnace construction - Google Patents

Description

y 9, 1940- G. DANFORTH, JR 2,266,944

FURNACE CONSTRUCTION Filed March 9, 1940 3 Sheets-Sheet 1 3 a Q k 3 1 N m 3 I i I J IN}:

IN VENT OR.

y 9, 1940- G. L. DANFORTH, JR 44 FURNACE CONSTRUCTION Filed March 9, 1940 3 Sheets-Sheet 2 INVENT OR.

y 9, 1940- G. DANFORTH, JR 6,944

FURNACE CONSTRUCTION Filed March 9, 1940 3 Sheets-Sheet. 5

INVENTOR.

ATTORNEYS.

Patented July 9, 1940 UNITED STATES PATENT OFFICE Open Hearth Combustion Company, 111., a corporation of Delaware Chicago,

Application March 9, 1940, Serial No. 323,079

8 Claims.

This invention relates to a new and improved furnace construction and more particularly to the construction of the side walls or back wall of a furnace of the open hearth type. The invention is directed to the wall construction above the metal line of the furnace or above approximately the line of the door sills and not to the walls of the hearth proper which may be of any suitable and usual construction I01 supporting m both the hearth and the walls of the present invention.

The present invention is not directed merely to the design or construction of the inner face of the wall but to the design and construction of u the entire wall including its protective covering of bottom-making material and has especial reference to the form and construction of the outer face of the walls.

Furnace side or back walls were formerly built vertically and since it was possible to protect only the base of the wall by means of the bottommaking refractory materials it was necessary to rebuild the upper portions of the walls at relatively short intervals. This rebuilding of the Walls was expensive both in cost of labor and materials and in loss of time in operating the furnace, due to the necessity of taking the gas off the furnace and letting it cool down to some extent so that the workmen could do the repairs.

, Later, sloping types of back walls were developed, as exemplified by the constructions shown in the patent to Naismith No. 1,563,038, and these walls have been widely adopted and have proven superior to the vertical walls. Nevertheless,

5 these have not entirely solved the problem as the upper portion of the wall has not been sufficiently protected. These sloping back walls are based largely on the angle of repose of the bottom-making refractories which it is intended to have lie up upon the wall. This angle is not constant and therefore cannot be accurately predetermined, as the bottom-making refractories and their physical condition are subject to frequent changes.

The span of the furnace roof must be increased to an extent equal to the outward slope of the side wall. Too great an increase in the roof span is undesirable. Therefore, the outward slope of the side wall as generally built approxi- 5 mates the average angle of repose, and is somewhat less than the maximum sometimes required by the variable nature or condition of the refractories used for maintaining the protective lining, and at such times the inner face of the 55 upper portion of the sidewall becomes exposed and then burned away by the furnace flame. As the inner face is burned away it becomes flatter and is again covered by the protective lining. After this has occurred a number of times, the upper portion of the wall is materially thinner and must then be renewed to the extent required, either by shutting down the furnace for repairs, or when the furnace is given a general relining.

If, instead of sloping the outer face of the wall as well as the inner face, the outer face is off- 1 set and substantially vertical, the excessive thickness of the lower portions of the Wall insulates the corresponding inner face to such a greater extent than the .upper face that the lower portion is burned away and thereby destroys the foundation orsupport for the protecting upper portion of the lining.

In constructing a side wall to use the Naismith invention, it has been customary to connect the full sloping portion to the vertical side walls at the ends of the furnace hearth by gradually decreasing the slope of the wall to meet the vertical position. It isthen necessary to increase the thickness of the furnace wall below the door sill elevation to provide a foundation for the protective lining of bottom-making refractories, or else to gradually eliminate the protective lining. Either is undesirable, and therefore to the length of the connecting portion of the sloping wall, it is customary to change rather abruptly from the full slope to the vertical position. This abrupt change forms an obstruction to the flow of the hot gases of combustion, which retards the flow of gases and wears away this portion of the wall and the adjacent portion of the furnace roof.

The construction of the present invention requires no greater lateral oifset of the top of the wall and consequently no wider roof than a sloping back wall of the continuously sloping type of the Naismith patent referred to above. It does, however, provide a more effective protection to the wall than such prior types of walls. This is particularly true as to the middle and upper portions of the wall and is accomplished without the use of water coolers for the wall. 7

It is an object of the present invention to provide a. new and improved side or back wall construction for furnaces of the open hearth type.

It is a further object to provide a wall construction for such furnaces which walls are of. substantially constant thickness and may comprise substantially uniform protective linings of refractory materials throughout a major portion of the height of the wall.

It is an additional object to provide a wall having its major brick portion extending outwardly and upwardly upon an angle to retain a substantially uniform thickness of protective refractory material with the upper brick portion of the wall vertical, said vertical portion also being protected by refractory material.

It is also an object to provide a wall substantially fully protected by refractory material and having no excessive wall thickness adjacent the door sill line or metal line of the furnace.

It is another object to provide a wall construction which merges gradually with the end portions of the furnace without substantial change in the angle of the sloping portion of the wall.

Other and further objects will appear as the description proceeds.

I have shown certain preferred embodiments of my invention in the accompanying drawings,- in which- Figure 1 is a vertical section across the center of the furnace;

Figure 2 is a plan view of half the furnace on a somewhat reduced scale;

Figure 3 is a fragmentary vertical section taken on line 3-3 of Figure 2;

Figure 4 is a section similar to Figure 3 taken on line 4-4 of Figure 2; and

Figure 5 is a fragmentary section similar to Figure 3 but taken at the center of the furnace and showing a modified form of construction.

Referring first to Figures 1 and 2, the furnace is provided with a hearth portion ll, an end wall 82 and front and back walls l3 and Il, which walls are sometimes called side walls. The front wall is shown as extending vertically and provided with door openings l5. As shown in Figure 2, the furnace end includes the air uptakes l6 and I1, together with the gas uptake it which is covered by the gas port structure [9. As best shown in Figure 1, the furnace hearth is provided with front and back walls 20 and 2|. These walls and the bottom 22 support the hearth lining 23 formed of refractory material. The tap hole 24 is shown as extending through the bottom-making material and the back wall 2|. The front walls are supported by the buckstays 25 and the rear walls by the buckstays 26, the latter having the angularly offset portion 21. The tops of these buckstays are held together by tie rods 28. The furnace is provided with the arched roof 29 which spans the distance between the front and back walls but does not rest on those walls, being supported from the metal frame members 30 and 3| carried by the buckstays.

The rear wall of the furnace is provided with an outwardly and upwardly inclined portion 32 which extends from approximately the door sill line 33 up a substantial portion of the distance to the roof. To accomplish the best results the outwardly and upwardly extending portion of the side wall should not be less than 40% nor more than of the total wall height. Above the Wall portion 32 is erected a vertical wall section 34 and this wall section conversely should preferably not be less than 20% nor more than 60% of the total height of the back wall or the total distance between the door sill line 33 and the skewback of the furnace roof.

As clearly shown in Figure 1, the sloping wall portion 32 is at such an angle and is so related to the vertical portion 34 that it maintains upon it a relatively heavy lining 35 of refractory material which extends upwardly to the roof. This,

therefore, covers the wall portion 32 with a substantially uniform layer of bottom-making material and the greater portion of the vertical wall section 34 is also covered with avery substantial thickness of bottom-making The back wall is therefore fully and thoroughly protected from hot gases by the bottom-making material. However, the entire thickness of the wall structure including the brickwork 32 and 34 and the lining 35, is nowhere so excessive as to prevent suflicient radiation of heat- It is, therefore, unnecessary to supply water coolers, which cause loss of heat from the furnace. The entire wall and the protective are not substantially thicker at and adjacent the door sill line than at the point of junction of the upwardly inclined and vertical wall sections. Consequently, any tendency to burn away at or adjacent the metal line and thus remove the support from the upper portion of the lining is The manner in which the sloping back is merged into the end sections is brought out in Figure 2 and in the two fragmentary sections Figures 3 and 4. The outwardly and upwardly sloping portion 32 of Figure 3 extends outwardly 25 on the same angle as does that portion of the wall at the center of the furnace, as shown in Figure 1. The side wall at this point, however, has less oifset so the portion 32 extends both. outwardly and upwardly a shorter distance and the vertical wall section 34 is correspondingly taller. When the back wall reaches the pointindicated by the section lines H on Figure 2, the back wall 36 is vertical.

In Figure 5 is shown a. section taken on a center line of the furnace in which the combined thickness of the brick wall structure and fillnace lining is substantially the same as in the form of construction shown in Figure 1. In Figure 5, however, the wall I has outer face provided with an outwardly and upwardly extending portion ll and with a vertically extending portion 42, while the inner face of the wall is on a continuous slope as shown at 33. This, therefore, increases substantially the thickness of the brick structure at and adjacent the elevation of the junction of the upper and lower portions of the outer face. This brick structure of Figure 5 is, however, of the same thickness at the sill line and adjacent the roof skewback as the brick wall portion of the wall. structure of Figure 1. The refractory lining N in the construction of Figure 5 is gradually tapered in thickness so that the combined thickness of the lining and brickwork is substantially the same in the construction of Figure 5 as the combined thickness of these materials in the construction of Figure 1.

As compared with a wall of the type shown in the Naismith patent, on a given furnace with the same offset and width of roof the present construction provides a wall of more uniform thickness, greater strength and less heat loss. If and when renewal or repair of the wall becomes necessary, it would be confiend to approximately the top twenty percent of the present wall as compared with repairs to approximately fifty percent of the wall of the prior art.

While I have shown certain preferred embodiments of my invention it is capable of change to meet difl'ering conditions and requirements and I contemplate such modifications as come within the spirit and scope of the appended claims.

What is claimed is:

1. In an open hearth furnace, a hearth, a roof, a side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion.

2. In an open hearth furnace, a hearth, a roof, 2. side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper 'portion, said wall and the protective lining together having substantially a normal thickness adjacent the base and the roof and having substantially greater than normal thickness at and adjacent the elevation of the junction of the upper and lower portions of the outer face.

3. In an open hearth furnace, a hearth, a roof, a side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, said wall and the protective lining together having substantially normal thickness at the plane of the base of the wall and adjacent the roof, the protective lining having a substantially greater than normal thickness at and adjacent the elevation of the junction of the upper and lower portions of the outer face.

4. In an Open hearth furnace, a hearth, a roof, 3. side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottom-making material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, the lower portion of the wall constituting not less than forty percent nor more than eighty percent of the height of the wall.

5. In an open hearth furnace, a hearth, a roof, a side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, the horizontal projection of the lower portion of the wall being not less than fifty percent of the elevation of the entire wall.

6. In an open hearth furnace, a hearth, a roof, a side wall extending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottom-making material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, the lower portion of the wall constituting not less than forty percent nor more than eighty percent of the height of the wall, the horizontal projection of the lower portion of the wall being not less than fifty percent of the elevation of the entire wall.

7. In an open hearth furnace, a hearth, a roof, at side wall extending from adjacent the door sill elevation to the roof, said wall having an.

inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, the height of the outwardly and upwardly extending lower wall portion being at a maximum in the central portion of the furnace and gradually decreasing toward each end.

8. In an open hearth furnace, a hearth, a roof, a side wallextending from adjacent the door sill elevation to the roof, said wall having an inner surface extending outwardly and upwardly to retain a protective lining of furnace bottommaking material substantially throughout the surface, the wall having an outer surface extending outwardly and upwardly in its lower portion and substantially vertically in its upper portion, the lower portion of the wall constituting not less than forty percent nor more than eighty percent of the height of the wall, the horizontal projection of the lower portion of the wall adjacent the center of the furnace being not less than fifty percent of the elevation of the wall, the height of the outwardly and upwardly extending lower wall portion being at a maximum in the central portion of the furnace and gradually decreasing toward each end.

GEORGE L. DANFORTH, J

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