US1927830A - Means and method of heat treating ceramic materials - Google Patents

Description

, P 19336 J. HARRINGTON 1,927,830

MEANS AND METHOD OF HEAT TREATING CERAMIC MATERIALS Filed Oct. 6, 1930 2 Sheets-Sheet 1 I p 1933- J. HARRINGTON 1,927,830

MEANS AND METHOD OF HEAT TREATING CERAMIC MATERIALS Filed 001:. 6, 1930 2 Sheets-Sheet 2 Patented Sept. 26, 1933 UNITED STA MEANS AND METHGD OF HEAT TREATING CERAMIC MATERIALS corporation of Illinois Application My invention relatesgenerally to means for and methods of heat treating ceramic materials, and more particularly to apparatus and methods for heat treating such materials. as brick within a kiln chamber.

In burning ware such as brick and other clay products, a certain period of the burning is required for burning out or oxidizing the carbon in the clay. During this period it is necessary to have an excess of oxygen within the kiln chamber in order to obtain the proper oxidizing effects. After this period of oxidation has continued for a predetermined period of time, it is desirable to produce a surface color or what is commonly known in the trade as flashing to the ware and this is accomplished by subjecting the ware within the kiln to a reducing atmosphere. That is to say, the atmosphere within the kiln is such as to reduce or de-oxidize' certain metallic or other oxides on the surface of the ware to produce certain colors or textureson saidsuriace.

It is one of the primary objects of my present invention to provide improved methods and means whereby the above mentioned oxidizing and reducing atmospheres within the kiln chamber may be obtained. 7

"More specifically, it is an object of my invention to provide areducing atmosphere within a kiln chamber by burning bituminous fuel in such a manner as to supply a deficiency of oxygen so that incomplete combustion of the carbon within the fuel takes place, thereby producing carbon monoxide.

Still more specifically, my invention contemplates the production of a reducing atmosphere within a kiln chamber by supplying an excess of carbon for the oxygen present within a fuel bed, thereby producing the same efiect as incomplete combustion. In other words, producing carbon monoxide for use in the kiln cham-,

the combustion of a .bed of fuel, such as bituminous fuel, may be controlled so as to produce proper oxidizing and reducing conditions within the kiln.

chamber may be maintained.

October 6, 1930. Serial No. 186,573 10 Claims. (01.25 145) A still further object of invention is to produce oxidizing and reducingxconditions with- TES PATIENT OFFICE} in a kiln chamber,as above setfor th, by introducing heated gases from an .external source under pressure, above atmospheric pressure where the cracks and crevices ofthe kiln; In addition to the above "mentio "ed objects and-advantages, my invention contemplates the V provision of a kiln in which "hot gases under apressure above'atmosphericpressure, may-beintroduced in the central lower portion j of the kiln chamber, the ware within the chamber proby to prevent the leakage of coldfair through viding a central passage fordirecting theheated gases vto'theupper portion o f the, chamber from i which point. said gases pass downwardly through the ware so as to effect "the uniform "burning thereof, said gases being drawn off through suit; able passageways connected with; tion ofthe kiln.

Figure 1 is a vertical sectional view .ofa dethelower por- 7 v I i oing and numerous other. objects and V y vice'whereby my improved method'of heat treat-:

ing ceramic materials may beefiectively :practiced; I

Figure 2 is an enlarged semi-diagrammatic;

disclosure insection of'an automatic furnace;

or stoker, said device beingprovidedfwitha fuel, bed capable of ;-pro ducing oxidizing conditions within the kiln chamber; and I Figure 3 is aview similar to Figure 2, disclosing a fuel bed of increased thickness whereby reducing atmospheric conditions within the kiln Referring now, to: the drawings more 'cle-1 tail wherein like numerals have been employed to designate similar parts throughout the variousjfigures, it willbe seen that'one embodiment of my invention resides in theprovision of a dome shaped kiln which I have designated-generally by the numeral 10. This kiln may beof any suitable refractory material and is providedwith a suitable floor 12 having a plurality of apertures 14 Ihese apertures 14 communicate with a commonegress chamber or passage 16 which passage in turn communicates with a central annularpassage 18. Gases from this passage 18 may be withdrawn through a suitable horizontal-passage 20, Figure 1. Heated gases are introduced within the chamber 22 of the kiln 10 from a. conduitorpassagefl i which opens intothe central lower portion of the chamber as clearly shown in Figure 1. This passage 24 communicates at its opposite extremity with the discharge side of'a combustion chamber 26 provided within a suitable furnace or stoker which I have desig nated generally by the numeral 28. I I This stoker or furnace 28 is positioned externally of the kiln chamber as clearly shown in Figure 1 and I prefer to have the furnace posioscillatory-bar 36 whic h is operativelyconnected with a depending arm. 38 of the plate by means of' a horizontal link 40 interposed between the I armf-38andthe free extremity of a lever arm 42. The plate 34 is supported by rollers 44 which are in turnsupported bysuitable guides 46, Figures 2"-=an'cl 3. The left onrearward extremity of the plate -34 is connected with a grate section 48 and this section rests upona stationary grate section 50. The rearward portion of this grate section 50 is formed with an upwardly projecting portion or h unp'52 which serves to control the thickness of .,th fuel bed within the combustion chamber 26. r

" The rearward-or left"extremity of this grate sectionbp rests upon a receptacle grate section 54' which is also-f'provided with an upwardly projecting portion or hump 56; Reciprocation is ,imparted to this section '54 by means of an 40"elongated link 58 which is detachably connected at its forward extremity with a pin 60 mounted at the free extremity of the arm 42. A notch 760a, Figure 3, is provided in the link 58 and when the .llink occupies the position shown in Figure 2, this 'notch 60a receives the pin. 60, thereby coupling f the arm 42 with the grate 54. However, when the link'58 is elevatedby manipulating-a suitable control lever" 62, the link occupies the position shown in Figure 3, thereby disconnecting the' "oscillatory arm 42 from the'grate 54. In other words, the grate 54 is reciprocable when the link 58 is connected to the pin 60 and is stationary when said link is disconnected from said pin.

7 V The grate 54 rests upon a rear stationary grate section 64 and thissection serves to direct ashes to the ash pit 66. A suitable partition 67 serves to separate the horizontal portion of the ash pit 66 from a chamber 68. This chamber 68 is adapted to receive air for draft purposes from 60 'anadjoining chamber '70, Figure .1.

This chamber 70 receives air under pressure from'a suitable air pump '72, Figure 1. connection it should be noted that the cham- .ber '70 is enclosed by a sealing wall '74. The air 'pressure within the chamber is maintained at slightly greater pressure than the-pressure within the stoker and hence proper draft conditions upwardly through the fuel bed supported bythe ..stoker grates isconstantly maintained. The advantages resulting from the provision of the sealing wall '74 will be apparent when it is understoo'd'that it is very difficult to construct a furnace or stoker which is free from leaks. at'all .points. Even the porous condition of the material used in the construction of the furnace is often tioned below the kiln chamber so as to facilitate In this sufficient to establish a certain amount of leakage. Hence, by subjecting the entire stoker unit and I am able to supply heated gases under pressure above atmospheric pressure .to. the kiln chamber 22. I

In Figure 2 I have shown a fuel beddesignated by the letter A and this fuel bed is maintained within the combustion chamber when the grate 48 with its associated fuel receiving plate 34 and the grate 54 are reciprocated The reciprocation of these grates causes a fuel bed of uniform moderate thickness to be built up and advanced through the combustionchamber. This fuel bed A is the type of bed which is employed to pro duce an oxidizing atmosphere within the kiln chamber 22.. Itshould be noted that I contemplate piling the ware or brick '76 within the kiln chamber so as to present a central flue or passage 78. The lower reduced portion of this passage or flue '78 communicates with'the passageway 24 extending from the combustion chamber and the upper extremity of the passage- 78 terminates at the upper central portion of the kiln chamber. Thus, hot gases introduced at the bottom of the kiln'pass upwardly through" the flue 73 and are then uniformly dispersed within the kilnchamber so as to effect the uniform diffusion of heat to all parts of the'kiln chamber. i

In order to obtain 'aclear understanding of my improved means andmethod for heat treating the ware, it is necessary to reviewin a gen- 'eral way the chemical reactions which take place in the fuel bed insofar as they apply to the formation of carbon'monoxide (CO) and carbon Referring first to Figure 2 wherein I have disclosed the fuel bed A which dioxide (CO2) is employed to effect the oxidation within the kiln chamber, it will be seen that air for com bustion passes upwardly through the grate surfaces, and the oxygen of this air first encounters the fixed carbon or coke at the lower incandescent surface of the fuel bed. It then combines with this carbon to form carbon dioxide,

(CO2) but the fuel-bed is sufficiently thick and 'contains'voids or channels of sufficient amount so that combustionis complete and carbon dioxide (CO2) escapes through these passageways or voids to the upper surface of the fuel bed without further contact with the carbon. Thus, the gasemerging from such a fuel'bed as the bed A contains a'high per centage of carbon dioxide (CO2) and little or nocarbon monoxide (CO).

As a matter of fact, there is practically univer sally an excess of oxygen which finds its way through the voids in the fuel bed, and the re-' sultant gases carry substantially from '2 to 8 percent of free oxygen. This gas which emerges from the fuel bed A is called an oxidizing gas or atmosphere, and it is this free oxygen at high temperatures that burns out the carbon:

contained in the clayof the ware, wherein the temperature of the ware reaches a certain defi-1 nite amount. Thus, when the stoker 28 is oper-i ating so as topresent the fuel bed A, I am able to produce an oxidizing atmosphere within'the kiln chamber so as to effect burning out of the carbon in the clay of theware. This burning process is continued fora predetermined time until the ware is in conditionto be flashed, that is, to be subjectedto a reducing atmosphere for the purpose of producing a desired surface 50 color.

"I' his'reducing atmosphere may be producedin various ways and for the purpose of illustrating one'practical-method, I have shown means whereby the thickness of the fuel bed may be increased. When it is desired'to change the oxidizing atmostion 48 and its companion fuel receiving plateBql.

Under such conditions the'distance betweenthe pushing'face of the grate-48 and the rear of the stoker is so great that the friction of the fuel thereon will act as a dam or check to the flow of thefuel and hence will necessarily effect the piling up of 'thefuel to a considerablethickness within thekiln chamber. 'In other words, the

thickness of the fuel bed will be materially in- V creased and I have designated this fuel bed of increased thickness by A ,Figure 3; By having this fuel bed of increased thickness, I obtaina stated above. vof the incandescent coke prevents a large quan- 'tity of carbon which at these temperatures will different chemical reaction Within the fuel bed which serves to produce a reducing atmosphere within the kiln chamber. Thus,'in the fuel bed A there is a thicker layer of incandescent coke won the supporting grate and air enters the fuel bed from below, as previously described, and the oxygen thereof combines with the bottom layer of carbon toform carbon dioxide (CO2) as also However, the increased thickness break down the carbon dioxide (CO2) and cause it to become carbon monoxide-(CO). There being no further air for combustion-available at this point, the carbonmonoxide (CO) will emerge from the surface of the fuel bed and presents what may be referred to as a reducing atmosphere within the kiln chamber. The stoker 28 may be continuously operated under thethick fuel bed conditions so as to cause the desired degree of flashing. It should be remembered that during this entire operation the pressure within the kiln chamber is above atmospheric pressure so as to maintain constant uniform atmospheric conditions within the chamber during this reducing process. Gases from the kiln chamber are continuously withdrawn from the bottom thereof and may be conducted to a second kiln (not shown) and subjected to ware therein, if so desired. Certain kinds of face brick can be permanently colored if allowed to cool several hundred degrees in a reducing atmosphere, and my invention enables this method to be effectively practiced. In other words, the fuel bed conditions within the .stoker may be continuously maintained while the kiln is cooling and during this entire time the pressure within the kiln is above atmospheric pressure. Placing the kiln and connecting passages under a pressure above atmospheric is esseptial because in the conventional operation of a kiln there will be enough infiltration into the kiln chamber through the cracks and other voids in the brickwork to provide all the oxygen needed to offset the reducing atmosphere produced in the furnace. It is essential, therefore, that the kiln be kept under pressure to maintain reduc ing conditions within the chamber.

From the foregoing description it will be apparent that my invention provides improved my 'means and methods whereby atmospheric conditions within a kiln chamber may be very effec- This causes the uncoupling tively' controlled -More specifically, it "mightbe stated that myinvention providesxan'ew and improved method of burning fuel, such as bituminous products, at a 'point externallyof a kiln chamber and controlling the combustion of saidfuel so as to present oxidizing or reducing conditio'ns'within the kiln chamber. the type of stoker shown in'the drawingsI obtain smokeless combustion, thereby positively prevent-' ing the introduction of smoke withinethe kiln chamber. By having the stoker positioned at-a point spaced from the kiln'chamber; Iamf'able By employing to employ allof the space withinthe kiln cham I her for ware toibeburned. Infact, the onlypor tion of the kllnwhich is nottaken-up by the ware is that portion immediately abovethe' passage or flue 24 andthis passagemust be'fpresent in order to effect the delivery ofthe heated gases to the upper portion of the kiln chamber; T- The kilnr and its associated partsiisvery-practical in con struction and may be very economically "manufactured. In fact, my invention presentsa' decideddivergence from the conventional methods 1 of heat treating ceramic materials, such as clayf products, and practical tests. have conclusively shown that by employing my'invention ceramic materials may be heat treated with greater economy and the time necessary for heat treatment materially reduced.

Having thus described my claim as new and desire to secure by Letters Patent isz' i 1. In heat treating apparatus of the class described, a kiln chamber for receiving a supply of ware to be heat-treated; an external furnace for supplying heated gasesunder pressurein excess' invention, what I of atmospheric pressure, means for conducting said heated gases into said kiln chamber,.whereby the pressure of the will be maintained above atmospheric pressure, and means for varying the thickness of the fuel bed within said furnace to control the oxidizing and reducing actions within the kiln chamber.

2. In combination with the chamber of a kiln, a furnace for supplying heated gases. a flue connecting said furnace with the kiln chamber, a casing enclosing said furnace, means for supplying air within said enclosure to maintain pressure surrounding the furnace greater thanpressure within the furnace, and means for varyingthe gases in said kiln chamber 1 i thickness of the-fuel bed in the furnace to control the oxidizing and reducing actions of the gases supplied thereby to the kiln chamber.

3. In heat treating apparatus of the class dej scribed, a closed kiln having a chamber for receiving ware to be treated, means for supplyingheated gases under pressurein excess of the atmospheric pressure surrounding the kiln, means for conducting said heated gases to the lower central portion of the kiln, and means for withdrawing gases from the lower'portion of said kiln.

4. In combination withthe chamber of a kiln, a furnace for supplying heated gases including a plurality of relatively reciprocable grate sections within a combustion chamber, a flue connecting said furnace with the kiln chamber, and control means for regulating the relative reciprocation of the grate sections to enable the production of oxidizingand reducing gasesfor said kiln chamber.

5. In combination'with the chamber of a kiln, a furnace for supplying heated gases including a plurality of relatively reciprocable grate sections within a combustion chamber, a flue con,- necting said furnace with the kiln chamber, and

means, for arresting the movement of at least I one of said reciprocable grate sections whereby to cause a building up of the fuel within the combustion chamber for the production of reducing gases. v

'6; In heat treating apparatus of the classdescribed; a kiln chamber for receiving a supply of ware to be treated, a furnace for supplying heated gases to said kiln chamber, said furnace includinga combustion chamber and means for pro v gressively feeding a bed of fuel therethrough, and

means for controlling the movement of the fuel bed through said combustion chamber in accordance with the oxidizing and reducing requirements Within the kiln, chamber.

7. In heat treating apparatus of the class dey 8. In heattreating apparatus of the class de scribed, a kiln chamber for receiving material to be treated; means to supply the products of fuel combustion to said chamber and'means to regu- 1 late the combustion of the fuel inaccordance with the oxidizing and reducing requirements within thekiln chamber. v H

9. The method of heat treating ceramic material, which consists in burning fuel and applying products of combustion to the material being treated whileregulating the combustion ofgthe fuelin accordance with the oxidizing and reduc- 7 ing effect required by the heat treatment.

10. The method of heat treating ceramic ma;-

terial, which consists in first oxidizing the ma- I terial by exposing it to-the products of fuel combustion properly regulated to' provide oxidizing gases and then exposing the material to betreated to a reducing atmosphere comprising the products of fuel combustion properly regulated to produce reducing gases. c e

JOSEPH HARRINGTON.

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