US3336716A

US3336716A - Furnace combustion chamber with a transverse composition differential

Info

Publication number: US3336716A
Application number: US294165A
Authority: US
Inventors: Scheppers Arthur
Original assignee: Johns Manville
Current assignee: Johns Manville Corp; Johns Manville
Priority date: 1963-07-10
Filing date: 1963-07-10
Publication date: 1967-08-22
Anticipated expiration: 1984-08-22
Also published as: GB1064644A; DE1274490B

Description

v A. SCHEPPERS FURNACE COMBUSTIO Aug. 22, 1967 I N CHAMBER WITH A TRANSVERS COMPOSITION DIFFERENTIAL Filed July' 10, 1963 INVENTOR. 4271/0 SCHEPPEES United States Patent Ofi 3,336,716 Patented Aug. 22, 1967 ice FURNACE COMBUSTION CHAMBER WITH A TRANSVERSE COMPOSITION DIFFERENTIAL Arthur Scheppers, Martinsville, N.J., assignor to Johns- Manville Corporation, New York, N.Y., a corporation of New York Filed July 10, 1963, Ser. No. 294,165 16 Claims. (Cl. 52-612) This invention relates to furnace combustion chambers, and more particularly to light weight furnace combustion chambers molded and constructed from refractory fibers and inorganic binders.

Typical furnace or boiler combustion chambers heretofore have comprised cast bodies or have been constructed of brick or the like components consisting of high density refractory compositions such as fire clay. Combustion chambers constructed of materials in this category entail several inherent disadvantages in addition to their material costs, such as their heavy weight and frangibility in handling, shipping, installing, etc., high labor costs in on-site fabrication, and such disadvantages are each reincurred in the subsequent replacement of burned-out units.

It is a primary object of this invention to provide a low cost, relatively light Weight, strong and durable furnace or boiler combustion chamber which is conveniently and economically molded from its constituents as a unitary body or article, or in the form of constituent or integral parts of a composite body or article, and which with normal care can be conveniently handled, shipped and installed without breakage under normal conditions and care and at relatively low labor costs.

It is also a primary and more specific object of this invention to provide a relatively light weight combustion chamber for furnaces or boilers of a unique construction having a relatively dense, non-porous or continuous, rigid, hard and strong outer Wall surface or area substantially conterminous with and adjacent to the outer surface of the article, and a relatively low density, porous, soft, resilient, fibrous inner wall surface or area substantially conterminous With and adjacent to the inner surface of the article whereby the composite effect of said chamber wall construction imparts such high and ample strength, integrity, rigidity and the like physical properties as to result in a light weight fibrous furnace chamber which fully withstands the abuses inherent in handling, shipping and installation, is self-supporting andcapable of being held or secured .in position Within the furnace, and resists high temperatures, thermal shock, temperature extremes and flame impingement in service Without appreciable or disabling cracking or erosion, spalling, etc.

It is a further object of this invention to provide a furnace construction chamber which is easily and conveniently molded or fabricated from relatively low cost materials, including conventional refractory fibers and temperature resistant inorganic binders, in a unique construction providing an effective, efiicient and enduring combustion chamber.

FIG. 1 is a pictorial view illustrating one exemplary type of a filter molded fiber and binder furnace combustion chamber of this invention in a typical configuration.

FIG. 2 is a cross-sectional view of the combustion chamber wall of this invention taken along line 22 illustrating the fiber-binder gradation transversely through the chamber wall from the inside surface of the chamber wall to the outside surface of the chamber Wall.

The foregoing objects and advantages, among others, are achieved by the present invention which comprises constructing or providing a furnace combustion chamber of suitable refractory fiber and inorganic binder wherein 'the Wall member forming the chamber comprises a heterogeneous composition gradated transversely through the wall thickness. More specifically, the transverse composition of the combustion chamber wall construction of this invention consists of a heterogeneously gradated composition having a maximum concentration of the inorganic binder accumulated in the area comprising or adjacent to and substantially conterminous with the outer surface of the combustion chamber, and a maximum concentration of the refractory fiber accumulated in the area comprising or adjacent to and substantially conterminous With the inner surface of the combustion chamber. This transverse Wall construction or composition provides a chamber having a relatively non-porous and dense, hard, strong external surface or area contiguous thereto, and a relatively porous and low density, soft, resilient interior surface or area contiguous thereto. The construction or effect of the transverse composition of the wall forming the product or chamber should be substantially uniform throughout the body thereof or at least through all critical areas of physical stress or shock and of exposure to temperature extremes or shock and aggressive flame conditions.

Referring to the drawing, FIG. 1 illustrates a typical cylindrical furnace combustion chamber 1 having a wall member 2, defining and forming a substantially closed chamber or enclosure for the containment of combustion, constructed in accordance with the precepts of this invention. Chamber 1, for conventional oil fired furnaces, typically has in the wall member 2 or in sectional members defining and forming the chamber enclosure, one or more openings for the introduction of a burner means, fuel or flame, and/or an outlet for the combustion products and the heat of combustion, as for example opening 3 to ac,- commodate a burner nozzle and combustion products and heat outlet 4 at the top of the chamber.

FIG. 2, illustrating a cross-section of the chamber Wall member 2 of FIG. 1 along lines 22, demonstrates the fiber-binder progression or gradation, attributable to the means of this invention, transversely through the chamber Wall member 2 from the inside surface 6 of the chamber Wall to the outside surface 5 of the chamber wall. As illustrated in FIG. 2, the outer surface 5 of the chamber Wall, or walls, defining the combustion chamber has a maximum concentration of binder accumulated in the area adjacent and substantially conterminous thereto providing a relatively non-porous and high density, hard, strong external surface for the chamber, and the intersurface 6 of the wall, or walls, defining the combustion chamber has a maximum concentration of fiber accumulated in the area adjacent and substantially conterminous thereto providing a relatively porous and loW density, soft, resilient interior surface for the combustion chamber.

This heterogeneous composition or construction transverse the inner and outer surfaces ofthe Wall defining the combustion chamber comprises a substantially uniform progression or gradation in composition differential with the concentration of inorganic binder of the wall member being at a minimum at the location of the innermost surface of the chamber wall and increasing in the direction towards the outermost surface of the combustion chamber while the refractory fiber content of the wall member is at a minimum at the outermost surface of the chamber wall and thereafter increases in a direction towards the innermost surface of the combustion chamber Wall wherein it is present at its maximum concentration.

Optimum conditions and effects of this invention are provided by a transverse Wall structure or construction refractory fiber approximately uniformly increasing in the direction of the innermost surface of the combustion chamber. However, an improved product of good and adequate characteristics can be provided by constructing the chamber wall in two or more integral parts or sections of unlike composition comprising discernible areas conterminous with and parallel to each major surface thereof with the section comprising or adjacent to the outermost wall surface embodying the maximum concentration of inorganic binder and the minimum of refractory fiber and the section comprising or adjacent to the innermost wall surface containing the minimum concentration of inorganic binder and maximum of refractory fiber. Any section(s) or area(s) intermediate the foregoing specified outermost and innermost sections, or areas adjacent to and conterminous therewith, can be aptly formulated or constructed to impart or contribute specific properties or meet the requirements of a particular application. Although the utilization of one of more distinctive compositions or areas thereof intermediate those of the outermost and innermost section or parts would in general comprise a somewhat complicated and not typical construction, when employed such an arrangement would normally entail ratios of refractory fiber and inorganic binder somewhere between those of the outermost and innermost surfaces or areas adjacent thereto and in a progressive gradient or series in keeping with the respective proportions of the said outermost and innermost surfaces or areas adjacent thereto.

The furnace combustion chambers of this invention can be molded as a complete unit, or fabricated from two or more molded constituent or integral elements, depending upon the construction desired and/ or the size, the intricacies of configuration, etc. of the furnace combustion chamber, and means of applying or introducing the chamber into the furnace or boiler structure. Molding of the chambers of this invention is effected in a usual manner as by accumulating from the medium of a dilute aqueous slurry or suspension thereof the fibrous component and binder, and any other material(s) employed therewith, on a perforated or foraminous mold or screen and consolidating and interfelting or co-mingling the same. As is typical, the molding procedure can frequently be enhanced or facilitated by the application of sub-atmospheric pressure conditions.

In molding the optimum product of this invention comprising a combustion chamber formed of a wall member(s) having a substantially uniformly progressing com position gradient transversely therethrough with the inorganic binder content approximately uniformly increasing in the direction of the outermost surface of the chamber and the refractory fiber content approximately uniformly increasing in the direction of the innermost surface of the chamber, the filter mold screen employed is arranged or constructed in such a manner that the solids components of the slurry stock are built up from the outside of the resulting molded combustion chamber towards the inside of the chamber. In other words, a mold screen or forming means is employed which defines the outer surface of the chamber molded thereon whereby the initial solids collected or accreted on the screen form and constitute the exterior surface or portion of the resulting molded chamber with the subsequent accretion of material progressing and accumulating towards the interior surface or portion of the molded chamber. With a mold of this nature the finer particles of the slurry which normally constitute the binder, and fillers if utilized, exhibit a greater tendency to migrate with the water through the fibrous material previously accumulated on the screen during the filtration process whereby the net effect comprises a greater accumulation of the fines comprising the binder, etc., upon or adjacent to the filtering screen surface and a corresponding maximum accumulation of the fibrous material on the surface opposite the screen mold.

Other means or molding techniques may, of course, be

employed in the molding of products within the scope of this invention. Such means or expedients include appropriately applying a filter mold or screen means to two or more slurry stocks of unlike proportions of solids constituents or compositions in a sequence which will effect accretion of the materials in a fiber-binder proportion gradient providing a chamber wall of a construction commensurate with the concepts of this invention, viz., providing the maximum concentration or accumulation of the inorganic binder in the area comprising or adjacent to the outermost surface of the chamber, and a maximum concentration or accumulation of the refractory fiber in the area adjacent to or comprising the innermost surface of the chamber. Accordingly, if a filtration mold is employed wherein the solid materials are built up from the outermost surface of the molded article or chamber inwardly as in the preferred means, the initial stock slurry is provided with a high ratio or a disproportionate quantity of inorganic binder(s) in relation to the inorganic fiber, and the subsequent stock slurry or slurries contain progressively reduced ratios of inorganic binder and progressively increased proportions of inorganic fiber. On the other hand, if the filter mold is of the opposite type wherein the solids of the slurry are built up from the innermost surface of the molded article or chamber in a direction toward the outermost surface thereof, the initial stock slurry consists of a higher or disproportionate ratio of inorganic fiber and subsequently applied slurry stocks comprise progressively reduced ratios of fiber and increased amounts of the binder(s).

Still further, but less desirable or expedient means or techniques of providing products within the concepts of this invention comprise the building up or uniting wall sections or areas of apt compositions or constructions commensurate with the product requirements and concepts of this invention.

Upon molding either the unitary body or one or more integral parts thereof by one of the foregoing or equivalent means, the article or component(s) is removed from the mold and subsequently dried as, for example, at about 300 to 350 F. for approximately 4 to 6 hours which completes the manufacture of the product if the particular binder(s) utilized does not require special curing or setting conditions and/ or further fabrication such as assembling constituent parts or the cutting of burner or the like openings in the chamber wall is not involved or required.

In the molding of the combustion chambers and of the constituents or integral parts of composites thereof the total solids concentration of the aqueous slurry or suspension of the mold stock are typically low, approximately 10 to 0.1% by weight and preferably about 1% by weight, as is common in such molding operations. Rem-oval of the shaped and consolidated molded chamber from the filter mold screen or element can be facilitated by conventional means including the reverse application of pneumatic pressure or partial disassembly of the mold structure.

Fibrous materials suitable for the construction of the molded furnace combustion chambers of this invention comprise conventional refractory fibrous materials having temperature resistance or softening points in excess of at least about 1500 F., or at a point providing a reasonable safety margin beyond the maximum temperature conditions contemplated in the particular furnace combustion chamber for which the product is designed, and preferably of about 2000 to 2500 F. Fibrous materials include semi-refractory wools formed of relatively pure rock or argillaceous matter and metallurgical slag but preferably high refractory compositions such as silica or quartz, magnesia, alumina-silica compositions and those also containing titania and/or zirconia in wide ranges of proportions, etc., and assorted combinations of such fibers.

Apt high temperature binders, for example, include clays, such as bentonite and hectorite, alkali metal silicates such as sodium and potassium silicates, frit, borax, aluminum phosphate, colloidal silica, colloidal alumina,

etc., and combinations thereof in finely divided particulate or solution form. Suitable proportions of refractory fiber to inorganic binders comprise approximately 60 to 95 parts by weight of fiber to approximately 5 to 35 parts by weight of binder with a typical optimum of about 9 parts by weight of fiber'per 1 part by weight of binder.

In addition to the foregoing essential components, various other additives or components can be included to impart or augment specific properties. These include, for example, organic or fugitive binders which burn out such as common starch based binder materials and the synthetic and natural resins which substantially contribute to green or prefired strength. Non-refractory fibrous materials such as asbestos and cellulosic fibers as exemplified by news or kraft pulp are also effective in raising the prefired strength level and integrity of the green or unfired product. Additionally, fl-occulating agents such as Dow Chemical Companys Separan may be effectively employed to enhance the molding procedure, and high temperature resistant, light Weight aggregates can be included as fillers. The organic or fugitive binder components can be employed in amounts up to approximately 10 to 15% by weight of the solids; the asbestos, glass and the like nonrefractory fibers are effectively included in amounts up to about 20% by weight; and the fillers, in amounts up to about 20%.

Typical composition formulations for the manufacture of the light weight (about 6 to 20 p.c.f. and preferably approximately 12 p.c.f.) fibrous furnace or boiler combustion chambers of this invention comprise:

Broad Preferred Range, Range, Percent Percent Refractory fiber 60 to 95 75 to 90 Inorganic binder. 5 to 35 7 to 10 Non-refractory fiber to 15 to Fugitive binder 0 to 20 0 to 5 O to 20 0 Light weight filler The following comprises specific illustrations or examples of some preferred and typical means of carrying out this invention. It is to be understood, however, that the specific materials and amounts thereof or formulations given and the means of molding, fabricating or otherwise constructing the products of this invention are primarily exemplary and are not to be construed as limiting the invention to any particular materials, amounts, formulations, compositions and/ or molding techniques or procedures recited hereinafter.

EXAMPLE I A combustion chamber of this invention comprising a product having a chamber wall member construction with a maximum accumulation of the inorganic binder concentrated in the area comprising the outermost surface of the chamber and/or adjacent and conterminous therewith, and the maximum accumulation of the fibrous component concentrated in the area comprising the innermost surface thereof and/or adjacent and conterminous therewith, was filter molded from a stock of dilute aqueous slurry or suspension comprising:

Bentonite clay, lbs. 10 Refractory fiber,* lbs. 74 Asbestos fiber, lbs 5 Kraft pulp, lbs. 10 Starch, lbs. 1 Water, gals. 2500 *Fiber composed of approximately equal parts of alumina. and silica with about 5% by Weight of titania. The stock was prepared by mixing the solids in a hydropulper with 500 gallons of water and subsequently diluting the same with 2000 gallons in a storage tank whereupon it was fed as needed to a mold box or tank. The filter mold, constructed of 14 gauge perforated brass with 7 in. perforations on A in. centers, was cylindrical in configuration, with one end closed, of the overall dimensions of 12 in. in diameter by approximately 15 in. in depth, and the foraminous cylinder and end wall were surrounded by a vacuum chamber to effect filtration through the wall and provide means for elimination of the aqueous filtrate. This filter mold was immersed in the mold box and with the application of a sub-atmospheric pressure of approximately 20 in. of mercury through the vacuum chamber the solids were filtered out on the surface of the closed end cylinder mold screen to an overall thickness of approximately /8 in. in a period of about 45 seconds. The mold was then removed from the mold box, and the molded item comprising an annular chamber open at one end was allowed to remain thereon for approximately 1 minute to further remove water prior to its discharge from the mold screen. The thus molded combustion chambers were then dried at about 300 F. for a period of approximately 8 hours to remove residual water and moisture whereupon they exhibited a modulus of rupture in excess of 30 lbs/sq. in. at an average density of approximately 11 lbs/cu. ft. These chambers had ample wet strength for handling without distortion and dry strength sufiicient to withstand normal shipping and installation conditions and their heat resistance was such that they could be repeatedly fired on their inner surfaces to 2000 F. without distortion, cracking, or spalling. Each fibrous chamber thus produced exhibited a relatively continuous or pore free, dense, hard, rigid outermost surface and a porous, relatively soft and flexible, fiber-like, resili ent innermost surface providing a chamber with strong,

rigid structural properties and a yielding, felt-like insulat-.

ing innermost surface.

Additional exemplary formulations in the manufacture of products of this invention comprise:

The formula of Example V eliminates any smoking resulting from the kraft when the chamber is initially fired. The glass of this formulation also fuses somewhat with the refractory fiber on the heated surfaces causing a hardening and strengthening effect. Heat shrinkage at 2000 F. of such a product is comparable to an organic fiber reinforced product, being less than 2% at 2000' F.

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

I claim:

1. A filter molded furnace combustion chamber formed uniformly throughout of a heterogeneous composition transversely through its thickness from the inner surface of the wall forming the chamber to the outer surface of the wall forming the chamber and having a maximum concentration of the said inorganic binder accumulated in the area adjacent and approximately conterminous the outermost surface of the wall forming the combustion chamber providing a relatively non-porous and high density, hard, strong external surface area and a maximum concentration of the refractory fiber accumulated in the area adjacent and approximately conterminous the innermost surface of the wall forming the combustion chamber providing a relatively porous and low density, soft, resilient interior surface.

2. The filter molded furnace combustion chamber of claim 1 wherein the chamber wall member comprises at least about 75% by weight of refractory fiber and inorganic binder.

3. The filter molded furnace combustion chamber of claim 2 wherein the refractory fiber is selected from the group consisting essentially of silica, alumina-silica, alumina-silica-titania, magnesia, and mixtures thereof.

4. The filter molded furnace combustion chamber of claim 3 wherein the inorganic binder is a high temperature binder selected from the class consisting of clays, alkali metal silicates, borax, aluminum phosphate, colloidal silica, colloidal alumina, and mixtures thereof.

5. The filter molded furnace combustion chamber of claim 4 wherein the chamber wall member comprises refractory fiber in the amount of approximately 60 to 95% by weight, and inorganic binder in the amount of approximately 5 to 35% by weight.

6. The filter molded furnace combustion chamber of claim 5 wherein the chamber wall member comprises nonrefractory fiber in amount up to approximately 20% by weight.

7. The filter molded furnace combustion chamber of claim 6 wherein the non-refractory fiber is cellulose fiber.

8. The filter molded furnace combustion chamber of claim 6 wherein the chamber wall member comprises a fugitive binder in amount up to approximately by weight.

9. A filter molded furnace combustion chamber formed by a chamber wall member comprising refractory fiber and inorganic hinder, the wall member being substantially uniformly throughout of a heterogeneous composition transversely through its thickness from the inner surface of the wall forming the chamber to the outer surface of the wall forming the chamber and having a maximum concentration of the said inorganic binder accumulated in the area adjacent and approximately conterminous the outermost surface of the wall forming the combustion chamber providing a relatively non-porous and high density, hard, strong external surface area, and a maximum concentration of the refractory fiber accumulated in the area adjacent and approximately conterminous the innermost surface of the wall forming the combustion chamber providing a relatively porous and low density, soft, resilient interior surface, said heterogeneous combustion chamber wall being substantially uniformly progressive in composition differential with the concentration gradient of the inorganic binder approximately uniformly increasing from the innermost surface in the direction of the outermost surface of the combustion chamber and commensurate therewith the relative concentration gradient of the refractory fiber approximately uniformly increasing from the outermost surface in the direction of the innermost surface of the combustion chamber.

10. The filter molded furnace combustion chamber of claim 8 wherein the chamber wall member comprises at least about by weight of refractory fiber and inorganic binder.

11. The filter molded furnace combustion chamber of claim 9 wherein the refractory fiber is selected from the group consisting of silica, alumina-silica, alumina-silica titania, magnesia, and mixtures thereof.

12. The filter molded furnace combustion chamber of claim 10 wherein the inorganic binder is a high temperature binder selected from the group consisting of clay, alkali metal silicates, borax, aluminum phosphate, colloidal silica, colloidal alumina, and mixtures thereof.

13. The filter molded furnace combustion chamber of claim 11 wherein the chamber wall member comprises refractory fiber in the amount of approximately 60 to by weight, and inorganic binder in amount of approximately 5 to 35% by weight.

14. The filter molded furnace combustion chamber of claim 12 wherein the chamber wall member comprises non-refractory fiber in amount up to approximately 20% by weight.

15. The filter molded furnace combustion chamber of claim 13 wherein the chamber wall member comprises a fugitive binder in amount up to approximately 10% by weight.

16. A filter molded furnace combustion chamber formed by a chamber wall member comprising approximately 89% by weight of refractory fiber, approximately 7% by weight of bentonite clay, and approximately 4% by weight of kraft pulp, the wall member being substantially uniformly throughout of a heterogeneous composition transversely through its thickness from the innermost surface of the wall forming the chamber to the outermost surface of the wall forming the chamber and having a maximum concentration of the said inorganic binder accumulated in the area adjacent and approximately conterminous the outermost surface of the wall forming the combustion chamber providing a relatively nonporous and high density, hard, strong external surface area, and a maximum concentration of the refractory fiber accumulated in the area adjacent and approximately conterminous the innermost surface of the wall forming the combustion chamber providing a relatively porous and low density, soft, resilient interior surface, said heterogeneous combustion chamber wall being substantially uniformly progressive in composition differential with the concentration gradient of the inorganic binder approximately uniformly increasing from the innermost surface in the direction of the outermost surface of the combustion chamber and commensurate therewith the relative concentration gradient of the refractory fiber approximately uniformly increasing from the outermost surface in the direction of the innermost surface of the combustion chamber.

References Cited UNITED STATES PATENTS 1,313,526 8/1919 Doble 26444 X 2,050,225 8/1936 Kohler 26444 2,103,463 12/1937 Jones.

2,122,288 6/1938 Knote 26444 2,124,745 7/1938 Morgan 162-384 2,895,544 7/1959 Parsons 158-45 3,100,734 8/1963 Rex et al. 158-1 X 3,179,156 4/1965 Weiss et al. 158-116 3,191,659 6/1965 Weiss 158-116 3,213,917 10/1965 Scheppers 158-1 3,217,701 11/1965 Weiss 158-99 X FRANK L. ABBOTT, Primary Examiner.

A. C. PERHAM, Assistant Examiner,

Claims

9. A FILTER MOLDED FURNACE COMBUSTION CHAMBER FORMED BY A CHAMBER WALL MEMBER COMPRISING REFRACTORY FIBER AND INORGANIC BINDER, THE WALL MEMBER BEING SUBSTANTIALLY UNIFORMLY THROUGHOUT OF A HETEROGENEOUS COMPOSITION TRANSVERSELY THROUGH ITS THICKNESS FROM THE INNER SURFACE OF THE WALL FORMING THE CHAMBER TO THE OUTER SURFACE OF THE WALL FORMING THE CHAMBER AND HAVING A MAXIMUM CONCENTRATION OF THE SAID INORGANIC BINDER ACCUMULATED IN THE AREA ADJACENT AND APPROXIMATELY CONTERMINOUS THE OUTERMOST SURFACE OF THE WALL FORMING THE COMBUSTION CHAMBER PROVIDING A RELATIVELY NON-POROUS AND HIGH DENSITY, HARD, STRONG EXTERNAL SURFACE AREA, AND A MAXIMUM CONCENTRATION OF THE REFRACTORY FIBER ACCUMULATED IN THE AREA ADJACENT AND APPROXIMATELY CONTERMINOUS THE INNER-