US3568611A

US3568611A - Furnace construction

Info

Publication number: US3568611A
Application number: US774977A
Authority: US
Inventors: Howard E Konrad; August Pocius
Original assignee: Johns Manville
Current assignee: Johns Manville Corp; Johns Manville
Priority date: 1968-11-12
Filing date: 1968-11-12
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09
Also published as: DE1957532A1; GB1257699A; FR2023104A1; BE741231A; ES373379A1; NL6916728A

Abstract

Improved furnace construction for furnace tops, arches or crowns and furnace wall sections in areas of the furnace not subject to weight and pressure of the structure itself or abrasion and impact from the charge or burden and washing action of melts, and a resilient lightweight insulating and refractory composite material therefor.

Description

United States Patent [72] Inventors Howard E. Konrad [56] References Cited sll-JJ UNITED STATES PATENTS 3 2 1,8 70,721 8/1932 FOltZ 110/1 [21] P 7 2,463,217 3/1949 TOhneSOl'l.... 110/1 [221 PM 1968 3 045 616 7/1962 Reich 110/99 [45] Paemed 1971 3 100 734 8/1963 Rex e661 l26/l44X 73] Assi nee Johns-Manville Corporation l g 3,118,807 l/l964 Holcomb l10/1X 3,213,917 lO/1965 Scheppers 126/144 3,375,795 4/1968 Merkle 110/99 Primary Examiner- Edward G. Favors Attorneys-John A. McKinney and Robert M. Krone [54] EP? B E.T ABSTRACT: improved furnace construction for furnace tops, 8 arches or crowns and furnace wall sections in areas of the fur- [52] US. Cl. 110/99 nace not subject to weight and pressure of the structure itself [51] Int. Cl. F23m 5/06 or abrasion and impact from the charge or burden and wash- [50] Field of Search llO/ 1, 99; ing action of melts and a resilient lightweight insulating and refractory composite material therefor.

PATENTEDMAR 9l97l 3,56? 611 sum 1 nr 4 HOWARD E. kO/VPAD gf AUGUST Poe/us PATENTEDHAR 9|97l 3,553,511

SHEEI 3 OF 4 HOWA RD E. ko/vmw TS AUGUST ROG/U5 FURNACE CONSTRUCTION BACKGROUND OF THE INVENTION Furnaces, kilns, etc. of conventional constructions and materials are fabricated from dense and rigid block and/or brick units typically assembled into massive structures of great weight and inflexible mass which are of relatively poor thermal insulating properties in relation to typical low-density thermal insulating materials. The structural strength limitations and high weight of such common refractory materials normally employed in furnace constructionsrequire auxiliary suspension means of extensive and heavy supporting beams and buttresses, etc., and if curved arches or crowns are utilized such foregoing means are required to resist the cold thrust of the arch and the additional horizontal stress from thermal expansion therein. Moreover, due to their dense and unyielding consistency, common refractory block and/or brick, upon exposure to heat and thermal expansion or shrinkage from internal or composition changes, are prone to spalling from cracks and ruptures withthe loss of fragments or spalls from the face of the refractory, thus exposing inner portions of the brick or block. Additionally, the thermal expansion or other heat induced dimensional changes in these inflexible materials are decidedly greater on the inner surface or hot face of the brick or block than on the outer surface or cold face which produces pronounced difierences in the dimensional changes through the individual brick or block between its inner and outer extremities thereby creating uneven stresses within the brick itself and in the overall structure assembled therefrom such as a wall or arch, as well as disrupting the original close or overall contacting fit of the full brick surface with joining members. Such changes in the surface contact between bricks, etc. through uneven thermal dimensional changes create excessive pressures or pinching between the bricks or blocks at either their inner or outer ends and when bricks are held by pressure of their weight between their engaging surfaces as in unmortared arches, thermal changes partially open joints between the bricks and may increase lower end or side exposure of the bricks tothe furnace atmosphere and temperatures furthering deformation and accelerating deterioration and failure of the brick structure. Thermal expansion and opening of joints between bricks are especially detrimental in arches because the inevitable shifting of bricks in the rising of the arch in response to thermal expansion frequently opens the joints at the outer edges of the brick near the point of midspan of the arch which concentrates the entire arch stress upon very small bearing surfaces of the inner edges of the brick and the unit stress can become so great as to break off the inner ends of the brick or reduce their service life. Accordingly, the heavy weight and rigid inflexibility, among other disadvantages, of conventional refractory materials have been responsible for many causes of failure, limited service life and assorted costly remedial measures.

SUMMARY OF THE INVENTION This invention constitutes an improved furnace construction and new materials therefor to provide nonload or low load carrying and supported or braced enclosing sections, such as walls and tops or roofs including flat or curved arches, crowns, etc. comprising the interior surface of the furnace structure exposed directly to the ambient conditions within the furnace including the combustion atmosphere, for substantially any area of the furnace construction which is not subject to significant weight and pressure of the structure or of the charge or burden, or abrasion or impact therefrom, or washing action of melts. The invention includes the use of a thermally and mechanically durable, resilient light weight material of high insulating properties and high temperature integrity composed primarily of refractory ceramic type fibers in the construction of furnace enclosure sections such as walls or tops and is especially directed to the formation of building units such as brick or blocklike components for assembly into furnace walls or roof sections including the utilization of more or less conventional fabricating operations, arrangements and supporting means or systems and devices as are commonly employed with typical refractory brick or block, and the manifold advantages and new benefits attributable thereto.

The principal objects and advantages of this invention are to provide improved means and materials for furnace construction and structures which facilitate installation in furnace assemblies in their ease of handling and working in either initial forming or thereafter cutting to shape and assembly in construction including prefabricating lightweight sections and transporting and assembly thereof in the field, which are relatively lightweight which minimizes the mass and complicity of supporting beams or butresses and suspending framework required and the material and construction costs associated therewith, which are of high thermal insulating properties reducing furnace operating costs and the expense for added external insulation. And of paramount significance, the means and materials of the invention are of such thermal and mechanical durability and resiliency as to effectively resist spalling or loss of fragments with the resultant exposure of inner portions due to cracking and rupture, form tight-fitting and resilient joints between adjacent surfaces of units obviating the need for mortared joints, and are of sufficient resilient compressibility to compensate for thermal expansion to offset any overall dimensional changes in either the individual units or entire assembled sections thus eliminating the uneven and destructive stresses within each unit and/or of the assembled section such as an arch as well an overcoming changes in or the opening of contacting faces or joints between the units.

BRIEF DESCRIPTION OF THE DRAWING This invention will be more fully understood and further objects and advantages thereof will become apparent when reference is made to the following detailed description of several preferred embodiments of the invention and the accompanying drawings in which:

FIG. I constitutes an end view of a curved arch construction embodying materials of this invention in the form of assembled tapered units joined with a key element;

FIG. 2 is a pictorial representation of the joining key element uniting the tapered units of the curved arch construction of FIG. 1;

FIGS. 3A and 3B are pictorial representations illustrating an alternative form of a joining key element for the uniting of tapered units of a curved arch construction as in FIG. 1;

FIG. 4 is a partial pictorial representation of a suspended flat arch construction embodying materials of this invention in the form of assembled supported rectangular units;

FIGS. 5A and 5B comprise a pictorial representation of an individual rectangular unit of the material of this invention with an embedded hanger, and the hanger for the flat arch construction of FIG. 4;

FIG. 6 is a partial pictorial representation of a modified hanger system for a flat arch construction comprising hanger brackets keyed into generally rectangular units of material of this invention;

FIGS. 7A and 7B constitute a pictorial representation illustrating the rectangular unit of the material of this invention cut to receive hanger bracket of FIG. 7B for the suspended flat arch construction of FIG. 6;

FIG. 8 constitutes a partial pictorial representation of another embodiment comprising hollow units for the assembly of a furnace arch or wall section, containing internal additional insulating material, and a modified suspending system;

FIG. 9 comprises a transverse cross-sectional view of a further embodiment and suspension bracket including backup insulation;

FIG. 10 is a pictorial representation of the hanger bracket illustrated in the embodiment of FIG. 9;

FIG. It comprises a transverse cross-sectional view of another embodiment and hanger bracket of the invention;

FIG. 12 is a pictorial view of the hanger bracket of FIG. ll;

H0. 13 illustrates a transverse cross-sectional view of a still further embodiment of an alternative supporting system of units comprising materials of this invention;

FIG. IA is a pictorial view of the hanger means of FIG. 13;

FIG. 15 is a partial pictorial representation of a furnace wall construction embodying material of this invention assembled with a keyed bracing system; and

FIG. 16 constitutes a partial transverse cross-sectional view of another version of a furnace wall construction embodying material of this invention illustrating a further variation of bracing.

DESCRIPTION OF THE PREFERRED EMBODIMENT This invention is concerned with an improved furnace construction comprising the application of apt forms or arrangements of low-density materials possessing high thermal resistance and insulating capacity, composed predominately of highly refractory ceramic-type fibers and a high-temperature resistant binder which have been integrated into strong and resilient bodies of apt configurations and dimensions, for assembly into the furnace construction and which possess the properties of ample thermal and mechanical integrity to endure typical furnace temperatures and. conditions without structural degradation in substantially any low-weight load bearing area and location free from direct physical contact with the furnace charge, burden or melt, and are of sufficient resiliency to offset thermal expansion or distortion. The essential high-temperature resistant refractory fibrous material of this invention can be precision formed initially, or thereafter cut or worked into substantially any configuration or dimensions including those of conventional or special commercial refractory brick or block bodies typically employed heretofore in furnace constructions. Thus, if appropriate, prior supporting beams and buttresses and/or suspending superstructures and arrangements need not be changed as they can be utilized with the materials and means of this invention whereby the means of this invention are readily amenable to the rebuilding or repair of old units as well as new furnace constructions, although due to the substantially reduced weight of the materials of this invention, lighter duty supporting or bracing, etc. components will suffice.

The low-density materials of this invention which are amenable to formation in precision configurations and dimensions, or easily workable to exact shapes, and of ample thermal and mechanical endurance for service in many types of furnaces in nonstructural and low or nonload bearing sections and areas beyond physical contact with the charge or melt, comprise refractory fibers of high melting, ceramiclike properties, effectively integrated with a bonding system of suitable thermal tolerances into a coherent low-density body of uniform and void-free consistency in relative approximate proportions, in percentage by weight, of about 60 to about 95 percent of refractory fiber with about up to about 40 percent of apt inorganic binder. To facilitate manufacture by means of filter molding or possibly other techniques in formation of the bodies of fiber and binder, it is frequently preferred to include small proportions of for example up to about percent by weight of a temporary or fugitive type binder material such as starch or similar organic adhesives to increase green or unfired strength and handling properties and which burn out upon exposure to temperatures encountered in the designed use of the product. Additionally, the predominately refractory fiber bodies may include, depending primarily upon the properties desired for the particular use or conditions encountered therewith, minor porportions of generally filler type materials such as amounts up to about 30 or 35 percent by weight, depending often upon the characteristics of the particular filler material. Preferred compositions suitable for many furnace applications comprise in approximate percentage by weight: 70 to 95 percent refractory fiber, 5 to percent inorganic binder, 2 to 8 percent starch or other organic adhesive and 0 to 20 percent of suitable filler. These materials are mixed uniformly, shaped and consolidated through appropriate means into bodies of about 6 to 25 pounds per cubic foot and typically most expediently about 10 to 20 pounds per cubic foot for all round optimum properties.

For most industrial furnaces or kilns, etc. service, the refractory fiber component usually must substantially maintain its integrity and essential characteristics at temperatures of at least about 2,000 F. and frequently higher, that is about 2,300 to 2,800 F. Commercially available refractory fibers exhibiting such temperature stabilities are usually suitable. They comprise fibrous products composed of silica or quartz, alumina-silica compositions including those containing small proportions of titania, zirconia, manganese, etc. The aluminasilica type fibers are preferred for their generally good qualities and lower costs. Of course, the so-called exotic or currently rare or costly fibers such as alumina, magnesia, hafnia, calcia, beryllia, zirconia, silicon carbide, boron nitride, etc. offering outstanding temperature resistance in the order of 3,000 F. or above and strength can be employed except at their present costs are more or less prohibited from any applications.

Inorganic binders include certain clays such as bentonite and hectorite, colloidal silica and colloidal alumina, phosphates comprising phosphoric acid salts such as aluminum phosphate, borates, sodium and/or potassium silicate, ceramic frit, etc. Organic fugitive or temporary ancillary binders comprise, in addition to starch, elastomer or resin based adhesives, natural adhesives of either vegetable or animal origin and assorted synthetics of substantially any base since their composition is not of paramount significance as their basic function is simply to enhance preliminary processing and handling. Apt fillers depending primarily upon properties desired such as densities and the desired degree of resiliency and costs, include in addition to recovered scrap or waste, kyanite, refractory grogs and particles, calcined diatomaceous earth, calcined kaoline, alumina, silica, pyrophyllite, etc.

These components are preferably formed into apt bodies such as brick or blocklike units of appropriate dimensions and configurations by admixing the ingredients in water as a dispersing medium to form a uniform and relatively dilute suspension of the constituents in a ratio of about 0.1 to about 10 parts by weight of the ingredients per parts by weight of water, preferably approximately 1 part by weight of the ingredients to 100 parts of water and filter molding therefrom. A vacuum, hydraulic means or mechanical press can be utilized to provide a pressure differential to motivate the filtering and in turn very uniform accumulation of the admixed and suspended ingredients into a mass of high consistency and of the exact shape and dimensions of filter mold. Other means of formation comprise simply casting a water suspended mixture of the components within a mold or container and removing the water content, or simply dry or wet felting and shaping a mass of the uniformly mixed components. Formation may be achieved either with or without a binder initially distributed throughout the fibers or other solids since binders in liquid form or carried in a liquid medium may thereafter be introduced into the bodies through subsequent impregnation, and frequently it is desirable to add additional binder or indurating agents by impregnating after formations either throughout the body or to only a limited area thereof such as the hot face to render it less porous and more durable. Formation by filter molding of the ingredients from a dilute water suspension is preferred in that it produces a decidedly superior product as to uniformity of composition and void-free consistency, and enables more effective control as to density.

This invention, in particular the materials thereof, is readily adaptable to conventional furnace constructions or assemblies and suspending or supporting systems and devices as will be fully evident from the hereinafter descriptions of specific embodiments, as well as being amenable to improvements or innovations in furnace constructions and associated means of support or suspension.

Fit ll illustrates a curved arch furnace top assembled from the material of this invention comprising low-density resilient bricklike units molded or cut with a groove in opposing sides to receive complemental keybars to maintain their relative abutting relation to adjacent units. The furnace sidewalls 10, typically of common refractory brick or block, are of conventional construction, but may be of less mass and strength due to the lower weight and resiliency and in turn reduced stresses attributable to the arch top formed by the means of this invention. The furnace top is assembled in a common arrangement of units ll formed of the material of the invention as blocks of aptly tapered shapes to provide typical arch wedges. To maintain the relatively lightweight units in position and alignment with each other throughout thermally induced changes and stresses, keybars 12 are positioned in' complemental slots 13 molded or cut into the abutting lateral sides of the units 11 FIG. 2 of the drawings more clearly illustrates in perspective how a keybar extends through the side of multiple adjacent units It fixing their lateral abutting relationship. FIGS. 3A and 3B illustrate a modification of this keybar arrangement utilizing an l-I-shaped or flanged keybar 12a and complemental shaped slot 13a to receive the flange bar. This latter arrangement prevents lateral movement as well as vertical movement.

in addition to the advantages of a lighter weight construction and in turn reduced strength requirements for supporting means, and improved thermal efficiency of higher insulating values, the resilient and compressible nature of the nonrigid material of this invention making up the units 11 and the curved arch assembly thereof, permits the material of the arch structure to absorb or offset the forces or deviation of the mass resulting from thermal expansion or change obviating dimensional changes in the structure such as the normal raising of the arch, shifting of the individual units relative to each other and in turn opening of the abutting joints or the introduction of added or uneven stresses or unbalanced forces within or among the units, particularly as between the outside or cold face and the inside or hot face thereof. As such, the nonrigid units and resilient material thereof are compressible internally without incurring degrading internal stresses whereby there are no added detrimental external or combined assembly stresses or forces and the abutting joints of the units surfaces are not disturbed or opened. 1

MG. illustrates a simple assembly for a flat arch furnace roof with associated suspending means and systems. One vertical bearing wall 114 of a furnace is shown of typical refractory brick construction and providing suppofi. for the flat arch suspending means which as employed with the lightweight and resilient construction materials of this invention need only be of light duty. As shown, an economical suspension beam may consist of ordinary steel pipe or bars 15 spanning the furnace from one vertical bearing wall 114 to the other. Generally rectangular shaped units 116, as illustrated individually in FIG. 5A, of the low-density resilient material of the invention are assembled laterally to each other to form a composite flat arch type roof for the furnace and each unit is suspended by an embedded hanger l'7 comprising, for example as illustrated in H6. 58, an inverted T provided with a curved upward end forming a hood to secure about suspension bar 19. Upon exposure to elevated temperatures and expansion, the resilient and compressible materials of the invention form closed, tight abutting joints over the entire adjacent surfaces between units and without creation of destructive uneven, stresses upon the units or the overall furnace roof structure and its supports. uneven FEG. 6 represents a similar type of flat arch furnace roof construction as in FlG. 4 comprising a modified suspension not entailing banger brackets molded in situ into the units as in the system of FIGS. 4 and 5A and 5B. in the system of H68. 6 units 38 of generally rectangular shape are provided with inverted T-shape slots E9 in their upper surface extending transversely across from one side to the other. The slotsl9 can be formed either during molding or subsequently cut therein. A slot l9 receives complemental transverse hanger bar 20 consisting of an inverted T-shaped or horizontally flanged vertical bar as shown in H6. 78 which in turn is secured to main suspension beam 21 resting on vertical furnace wall 22. i

FIG. 8 illustrates a distinctive embodiment of the invention comprising rectangular units 23 having a hollow interior 2e running therethrough to receive flat plate 25 of the supporting bracket which is secured to hanger rods 26, or wires or chains, etc., suspended from the suspension bar 27. Optionally, the hollow interior of units 23 can, as an economy measure either to enhance the insulating efficiency or reduce material costs, contain a lower cost insulating material 23 such as glass fiber, conventional mineral or semirefractory -wool, etc. since the latter materials of reduced thermalendurance are shielded from the furnace atmosphere and accompanying high temperatures.

FIG. 9 illustrates the use of a relatively large unit 28 of generally slab or blocklike shapes of the low-density resilient material in the invention. The slablike units 28 can be supported for flat arch or furnace tops by any of a number of systems or devices. As shown in FIGS. 9 and 10, pin 29 with a hooked shaped head for attachment to a standard suspension bar, constitutes the hanger bracket. The pin 29 is pointed at its lower end to facilitate forced penetration through the unit 28' and it is provided with a washer 30 as shown in H0. 10 which is slipped over the pointed end of the pin and wedged thereon or otherwise fixed by any appropriate means to provide a retaining shoulder or stop. Preferably a section or plug 31 of the construction unit 28 is cut out from the lower half or hot face generally concentric with the pin and of a size to accommodate and countersink the washer 30, and following installation of the pin and securing washer plug 31 is replaced and held by a forced friction fit or an inorganic adhesive, to insulate and shield the pin and washer hanger bracket from the furnace temperature and conditions. Optionally this embodiment or substantially any of the other arrangements of this invention, may include a low cost backup insulation shown as 32 in FIG. 9 to either increase the overall insulating efficiency of the furnace, or alternatively to reduce costs by enabling the use of furnace wall or roof sections composed of units of reduced or minimum thickness through the substitution on the back or cold face of a less costly insulating material as shown in FIG. 9.

The variation of FIG. ii. is similar to FIG. 9 except that a ceramic pin 33, independently illustrated in FIG. 12, with a flanged head 34 passes through and supports the unit 35 by attaching to suspension bars 36. The ceramic composition of pins 33 will endure furnace temperatures whereby the head of pin 34 need not be countersunk and covered as with a metal pm.

FIG. 13 demonstrates the hanging of similar slablike units 37 as of FIG. 9 and 11 by means of l beam hangers 38 of ceramic material shown in FIG. 14 wherein the units 37 are supported by the flanges 39 of the ceramic I beams which in turn are suspended from suspension channels it).

The illustrations of FIGS. 15 and lo demonstrate the application of the material and principle of this invention to the construction of furnace walls or generally vertical sections in areas beyond physical contact with the charge or melt, and which are of low or nonload bearing requirements. As illustrated a typical construction constitutes assembling the upper area of the furnace wall from the units of low-density and resilient material of the invention, either combined with a conventional arch or roof or with one of this invention, by continuing from the lower refractory brick or block wall which is in direct contact with and retaining the charge or melt, with a construction of the more economical and efficient materials of this invention. Specifically referring to FIG. 15 the brick wall 41 constitutes the base of the furnace wall and retains the melt or charge 42, and superimposed thereon the units d3, consisting for example of relatively large block or slablike bodies, constitute the balance of the furnace wall structure continuing from a level safely beyond possible contact with the melt. The

units 43 of the upper wall assembly are in the instant embodiment provided with channels 44 in their outer or cold face surface to complementally receive a bracing H-shaped or flanged keybar 45 which bar in turn is fixed to vertical struts or uprights 46, and may additionally serve as buttresses for wall 41 or supports for suspension beams or systems for the hanging of the furnace arch.

In FIG. 16, the block or slablike units 47 are resting on furnace base wall 48 of conventional refractory material and braced and secured to backing plates 49 by means of large lag screws 50 passing through plate 49 and threaded into units 47. The backup plates 49 are held by transverse bars 51 which in turn are fastened to vertical struts or uprights 52.

As with the furnace arch or roof constructions of this invention, the wall or vertical sections of the invention can be supported or braced by means of a number of systems or arrangements of either conventional or new designs and the arch or roof and wall or vertical sections can be employed together through the use of suitable combined structural braces or supports and suspension means which due to the low weight of the materials of this invention need not be of as extensive mass and strength as that required with conventional refractory constructions. Moreover, the resilient and compressible characteristics of the nonrigid materials of this invention decidedly reduce the degree of precision of dimensions or shapes and of mating of parts as normally required for the assembly of rigid or inflexible refractories.

It will be understood that the foregoing details are given for the purpose of illustration, not restriction, and that variations within the spirit of this invention are intended to be included within the scope of the appended claims.

We claim:

1. In a furnace, a low load carrying, supporting enclosing section which includes at least a substantial part of the interior surface of the furnace structure in an area beyond physical contact with the furnace charge, said enclosing section including a substantial part of the interior surface of the furnace structure formed thereby being composed of a plurality of individual units constructed of low density and resilient integrated masses of less than 25 pounds per cubic foot consisting essentially of refractory fiber and high-temperature resistant binder with the refractory fiber being the major constituent, assembled together in abutting contact with each other.

2. The furnace construction of claim 1 wherein the low density and resilient individual units are about 6 to about 20 pounds per cubic foot.

3. The furnace construction of claim 2 wherein each individual unit has been fitted therein a bracket securing the unit to a supporting structure.

4. The furnace construction of claim 3 wherein the enclosing section which includes at least a substantial part of the interior surface of the furnace structure comprises the furnace roof.

5. The furnace construction of claim 3 wherein the enclosing section which includes at least a substantial part of the interior surface of the fumace structure comprises a furnace wall.

6. The furnace construction of claim 3 wherein each individual unit of the body is substantially rectangular in configuration forming an easily assembled block.

7. The furnace construction of claim 3 wherein each individual unit is .hollow and contains insulating material therein.

8. The furnace construction of claim 3 wherein each individual unit is backed by thermal insulating material.

9. The furnace construction of claim 3 wherein the retaining means comprises a bracket having a flange fitted within the unit to secure the same to a supporting structure.

10. The furnace construction of claim 3 wherein a bracket is fitted into the abutting surfaces of adjacent units to key the adjacent units together.

11. The furnace construction of claim 3 wherein the bracket comfrises a hanger which attached to a supporting structure.

1 The furnace construction of claim 2 wherein the individual units of the body are suspended by ceramic refractory hangers.

13. The furnace construction of claim 2 wherein the individual units of the body are supported by penetrating pins.

Claims

5. The furnace construction of claim 3 wherein the enclosing section which includes at least a substantial part of the interior surface of the furnace structure comprises a furnace wall.

7. The furnace construction of claim 3 wherein each individual unit is hollow and contains insulating material therein.

11. The furnace construction of claim 3 wherein the bracket comprises a hanger which attached to a supporting structure.

12. The furnace construction of claim 2 wherein the individual units of the body are suspended by ceramic refractory hangers.