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Publication numberUS2242434 A
Publication typeGrant
Publication dateMay 20, 1941
Filing dateFeb 27, 1937
Priority dateFeb 27, 1937
Publication numberUS 2242434 A, US 2242434A, US-A-2242434, US2242434 A, US2242434A
InventorsJr Charles L Norton
Original AssigneeBabcock & Wilcox Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of manufacturing insulating firebrick
US 2242434 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

Patented May 20, 1941 2,242,434 FsFI'CiE METHOD OF MANUFACTURING INSULATING Fl-REBRICK Charles L. Norton, Jr., New York, N. Y., assignor to The'Ba'bcock & Wilcox Company, Newark, N. J., a corporation :of New Jersey NoDrawing. Application February 27, 1937, Serial No. 128,162

Claims.

This invention is an improvement inthear't of light weight, high strength, permeable, cellular, ceramic products and their manufacture, particularly relating to those of a character adapted for use as heat insulator-s and also having good acoustic properties whereby noises, for instance, accompanying firing of and flame propagation in a furnace may be quieted to a marked degree.

In the manufacture of such ceramic products processes have heretofore been proposed, and products have been successfully manufactured by combining various proportions of argillaceous material, wood or other combustible or eliminative particles and water, the solid materials first being mixed dry, water then added and the whole being mixed to an extent which results in air bubbles being liberally interspersed; then molding the mixture, drying the molded shapes, and finally firing the dried shapes to burn out the combustible or remove the eliminable particles of the mixture under such conditions as avoid disintegration of the shapes and preserve the cellular structure created by the entrained air bubbles and elimination :of such particles while, at the same time, rendering the product porous.

In order to facilitate handling of the molded shapes priorto burning, such mixtures as above outlined and treated have also .had added to them a small amount of some hydraulic setting agent such as calcined gypsum or the like.

However, with such mixtures the rate of productionnecessarily has been slow, due to the fact that in the manufacture of bricks of ordinary size, such as 4%" x 9" 'x 2 the drying step has been considered necessaryjin order to remove moisture before burning-the brick shapes being dried for a period of 12 hours at a temperature of approximately 225 F. This drying step. before burning, has the disadvantage of requiring additional expenditure of fuel, and large storage space for unburned shapes in order that an adequate supply of dried shapes maybe kept ahead to provide suitable quantities for economically operating large sizekilns, with consequently high overhead charges in the manufacture.

An object of the present invention is to provide a method and a product of the character described wherein the drying step is eliminated.

A further object is a method and a product of the character described wherein the stability of the mass, after being mixed, is such as to eliminate the usual step of molding, should it be desirable, and permit the extrusion of the mass through a die and the utilization of appropriate cutting-off means to sever the extruded strip into brick shapes.

One manner in which the invention has been commercially practiced is to form a dry batch mixture according to the following formula:

. Pounds Plaster of Paris (CaSOUI-IzO) 3'7 4-8 mesh wood sawdust '37 Pulverized. Georgia kaolin The foregoing materials for the batch are commercially dry, that is to say they contain only the normal moisture content incident to storage in the air.

These dry materials are paddle mixed in a container for a time "interval such that there is an intimate association of the particles of the mass.

The dry batch 'isthen similarly paddle mixed in another container where water is added in sufficient quantity to condition the mix for the step of forming into shapes. The shapes may be formed by extrusion and wire cutting or by casting to shape, or by casting a slab and wire cutting.

To form -a fiowable castable mixture of the above batch water is usually added in an amount equal to 100% by weight, but atmospheric 'conditions, the type, amount and condition of the starting materials, and the character of forming step to be used dictate and actual relationship of added moisture to dry materials.

In forming the above mixture into shapes for standard fire brick units when fired and finally sized, the mixture of fiowable castable consistency was'cast into molds after dry and wet mixing periods of 30 seconds each with a transfer interval of 20 seconds from dry to wet mixer.

In the particular operation referred to molding was accomplished by casting into mold shapes each of which was 30" x 10 x 5". The slabs thus obtained were then each wire cut to provide nine slugs ready for firing. After casting the filled molds are allowed to set for only a suffi'cient period oftime to permit recrystallization of the plaster of Paris.

Instead of wire cutting division plates or partitions may be used in the molds. When extrusion is used two of the required dimensions are fixed by the die head used, whereas the third is obtained by governing the rate of extrusion and wire cutting at uniform intervals. Another method of molding commonly referred to as extruding and which may also be used is to cast the shapes into a mold form from which they are removed onto oiled shods by push blocks contacting one face of the cast shape while the mold and its respective push block are moved relatively to displace the brick shape. From the foregoing it is apparent that molding or shaping of the wet material is not restricted to any parmethods may be employed.

After formation of the brick shapes and recrystallization of the plaster of Paris it will be found that while still wet they are, nevertheless,

in condition to be readily transported and placed;

in the kiln.

The wet shapes are placed in the entrance of a; I

perature level than the interior too rapidly and promote uniformity of temperature penetration with-the result that leeway in kiln regulation is greaterfand there is less opportunity for the development of surface and other flaws in the finished shape. I

The water vapor and gases due to distillation of the combustible particles are many hundreds of times greater in volume than the original water or combustible volume, and escape through minute ruptures of the cellular walls which thus adds porosity to the structure, but such ruptures are so minute in the finished product as to impose considerable resistance to the passage of gases through the ultimate brick. I I

At approximately the stage where carbonization of the combustible particles is complete throughout the brick shapes and where there is nofurther danger of uncontrollable combustion of the same adding to the'temperature of the kiln, the reducing atmosphere is replaced withan oxidizing atmosphere and the temperature elevated over a suitable time interval to 2350 F., the carbon particles are thus completelyeliminated, leaving minute voids or cells which by volume constitute better than 70% of the volume of the shape.

The resulting product is a light weight insulating firebrick refractory to 2200-F., of low thermal conductivity, with unusual stability, which may be cut and sized with ordinary wood saws, will receive screws, bolts or nails, and has the property of absorbing sound to a marked degree. In use'it effects a substantial saving in industrial furnace operation by reducing both the'timeand fuel, or electric current energy, required to reach thermal equilibrium.

Authenticated tests for thermal conductivity and fusion at the laboratories of Massachusetts Institute of Technology for brick made in accordance with the foregoing formula and method are as follows:

An additional advantage incident to wet burning as compared with burning the shapes after drying is that the volume shrinkage of the dried shapes while burning is materially greater; 'It was found that with slugs made from the same were burned undried.

The result is that the density of the dried and fired material was as much as 16% more than the density of the undried and fired material and the volume shrinkage of the dried and fired material was nearly twice that of the volume shrinkage of the undried and fired material; for instance, in measured samples the volume shrinkage of the undried and fired material was 16.7%,

while that of the dried and fired material was 32.6%, the weight of a finished brick size of the fired undried sample was ,1.98# whereas that of the dried and fired sample was 2.29#. It is a well known fact that with materials of essentially the same composition the thermal conductivity will increase directly with an increase in the weight of a given volume, thus conclusively demonstrating the superiority of the product of this invention over that produced by methods used heretofore.

Additionally contributing to the superiority of the product is the fact that the starting materials do not contain just sufiicient plaster of Paris to cause setting but have an additional.

amount over that required for setting. With amounts as low as is required only for setting undue shrinkage in firing is encountered, but gwith the use of as much as 21% of the dry mix, as is the case in applicants invention, a real advantage is gained for this reason: The fired shape is rendered more cellular and consequently lighterin weight by the incorporation in the starting materials of enough plaster of Paris and water; the plasterof Paris, on burning the shape, loses all of its water of combination as well as any that is mechanically present, and also the sulphate radical breaks up, leaving merely CaO to combine with silica in stable compounds. This loss of water of combination by the plaster of Paris and the breaking up of the sulphate radical leaves minute voids or cells in large numbers in addition to those due to aeration and burning out of wood particles, for instance a pound of set plaster of Paris dead burned is reduced to .3 of a pound (approx). In the burned shape of the formula incorporated herein each slug originally contains approximately .8 lb. of plaster of Paris which, after firing is reduced in weight to approximately .22 1b., the loss in weight resulting in additional cells. Inthe claims, the terms molded and molding are intended to generically cover the various methods of forming the desired shapes described herein and equivalent methods; the term burning temperature is used to define kiln temperature conditions sufficient to heat the surface of the brick within one (1) hour of being inserted to a temperature several hundred F. higher than the maximum ebrick temperature attained heretofore during ordinary drying operations.

Iclaim- 1. The method of making a ceramic product which comprises mixing argillaceous material and a hydraulic setting agent with water to flowable consistency, forming the shapes before setting occurs, and'then subjecting the shapes to a burning temperature While they still retain substantially all of the water of the mixture.

'2. The method of making a refractory product which comprises intimately mixing refractory material, eliminable particles, a hydraulic setting agent, and waterto flowable formable consistency, forming the shapes before setting occurs, and subjecting the shapes to a burning temperature while the mixture still retains substantially all of its water and whereby eliminable particles disappear to leave a cellular structure.

3. The method of making a ceramic'product which comprises intimately mixing argillaceous material, combustible particles, a hydraulic setting agent, and water to flowable formable conable mass, forming into shapes prior to recrystalization of the plaster of Paris, and subjecting the shapes to a burning temperature while the mixture still retains substantially all of its water.

5. The method of making a ceramic product which comprises intimately dry mixing pulveriaed kaolin, wood flour and plaster of Paris, adding water while mixing to form a flowable formable mass, forming into shapes prior to recrystallization, subjecting the shapes, while the mixture still retains substantially all of its water, to a burning temperature in a reducing atmosphere to carbonize the wood flour, and then burning at a higher temperature in an oxidizing atmosphere whereby the carbon particles are eliminated.

6. The method of making a ceramic product which comprises intimately dry mixing plaster of Paris, wood flour, and Georgia kaolin in the ratio of 37 pounds of plaster of Paris, 37 pounds of Wood flour and 100 pounds of Georgia kaolin,

all in pulverized form, adding 100 per cent water while mixing to form a flowable castable mass, molding shapes therefrom prior to recrystallization of the plaster of Paris, firing the shapes at a burning temperature in a reducing atmosphere while the mixture, still retains substantially all of its water and immediately following recrystallization of the plaster of Paris to completely carbonize the wood flour, and then firing at a higher temperature in an oxidizing atmosphere.

'7. The method of making a burnt cellular ceramic product which comprises forming a flowable moldable mixture of argillaceous material, gypsum and water, with an excess of gypsum over that required for suificiently strengthening the mixture when molded into shapes to permit handling, molding the mixture into shapes, and then subjecting the shaped mixture while it still retains substantially all of its water to a temperature sufiicient to break up the sulphate radical of the gypsum whereby voids are produced throughout the mass.

8. The method of making light-weight refractory products which comprises forming a flowable moldable mixture of refractory material, a hydraulic cement, and water, molding the mixture intoshapes, and subjecting the molded shapes when set and while retaining substantially all of the water present therein when molded to a burning temperature.

9. The method of making light-weight refractory products from molded shapes containing a mixture of refractory material, combustible particles, and a substantial amount of water which comprises subjecting the molded shapes while containing an amount of water equal to at least 30% of the weight of the dry materials included therein to a burning temperature.

10. The method of making light-weight refractory products from molded shapes made from a flowable mixture of refractory material, a hydrauiic cement, and a substantial amount of water which comprises subjecting the molded shapes while containing substantially all of the water. present therein after being molded to a burning temperature. v

11. The method of burning molded shapes made from a fiowable mixture of refractory material, a hydraulic cement, combustible particles, and a substantial amount of water to form lightweight porous refractory products which comprises subjecting the molded shapes while containing substantially all of the water present therein after being molded to a burning temperature, and rapidly heating the same to a temperature above the ignition temperature of the combustible particles.

12. In the manufacture of refractory products from an argillaceous base material normally having a high shrinkage when fired, the method of making such products with a minimum firing shrinkage which comprises mixing a hydraulic setting agent and a substantial amount of water with the argillaceous material to a flowable consistency, molding the mixture into the desired .final shapes, and subjecting the molded shapes when setand while containing substantially all of the water present therein when molded to a continuous firing cycle in which the molded shapes are rapidly heated to a temperature substantially above 1600 F.

13. The method of making light-weight insulating brick which comprises molding a flowable mixture of pulverized kaolin, combustible particles, a hydraulic cement, and water into the de sired brick shapes, and subjecting the molded shapes when set and while retaining substantially all of the water present therein when mold- ,ed to a continuous firing cycle in which the molded shapes are rapidly heated to a temperature above 1000 F.

14. The method of making light-weight insulating brick which comprises molding an aerated flowable mixture of pulverized kaolin, combustible particles, a hydraulic cement, and water into the desired brick shapes, and subjecting the molded shapes when set and while retaining substantially all of the water present therein when molded to a continuous firing cycle in which the molded shapes are rapidly heated to a temperature above 1000 F. in a reducing atmosphere and subsequently heated at substantially higher temperatures in an oxidizing atmosphere.

15. The method of making lightweight porous refractory products which comprises molding into shapes a flowable mixture of refractory material, water and an amount of plaster of Paris substantially in excess of th amount required when set to sufliciently strengthen the molded shapes to permit handling thereof, and then subjecting the molded shapes when set and while re taining substantially all of the water present therein when molded to a temperature sufficient to break up the sulphate radical of the plaster of Paris.

CHARLES L. NORTON, JR.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2425891 *Jan 12, 1946Aug 19, 1947Carborundum CoRefractories and method of making
US2908157 *Oct 30, 1953Oct 13, 1959Foster Wheeler CorpComposite firebrick
US3176054 *Apr 9, 1962Mar 30, 1965Harbison Walker RefractoriesInsulating refractories
US3297801 *Jan 21, 1965Jan 10, 1967Johns ManvilleManufacture of insulating firebrick
US6042763 *Sep 19, 1997Mar 28, 2000Kumaoka; Shun`IchiMethod of preparing porous ceramics provided with amorphous pore surfaces
US6413432Feb 29, 2000Jul 2, 2002Shun'ichi KumaokaMethod for treating drain water and waste liquid by the use of porous ceramics provided with amorphous pore surfaces
US6420292Feb 29, 2000Jul 16, 2002Shun'ichi KumaokaPorous ceramics provided with amorphous pore surfaces
DE202012103050U1Aug 13, 2012Sep 3, 2012Promat GmbhWärmedämmstoffformkörper
EP2698358A1Aug 12, 2013Feb 19, 2014PROMAT GmbHHeat insulating material formed body
Classifications
U.S. Classification264/44, 264/DIG.630, 264/680, 501/83
International ClassificationC04B28/14, C04B38/06
Cooperative ClassificationC04B28/14, C04B38/0675, Y10S264/63
European ClassificationC04B38/06F2D10, C04B28/14