US2081476A - Ceramic furnace - Google Patents

Description

May 25, 1937 CERAMIC FURNACE Filed Oct. 16-, 1955 Z Sheets -Sheet 1 l'rwenian friennefian ussens Q J. DUSSERIS 2,081,476

y 1937- E. J. ousssms 2,081,476

- CERAMIC FURNACE I vr Filed Octi. 1.6, 1935 2 Sheets-Sheet 2 a mammfzz'enne Jan ssem's fif y.

metal cars along rails.

Patented May 25, 1937 rricr.

CERAMIC FURNACE Etienne Jean Dusseris, Paris, France Application October 16, 1935, Serial No. 45,328

7 Claims.

My invention relates to furnaces for burning ceramic products and the like, and more particularly concerns an improvement in the so-called Hoffman type of continuous furnace.

While theoretically, continuous furnaces represent the ultimate ideal in the ceramic industry and While they have been actually employed in this country, their operation has not been as successful as anticipated, for various reasons; and

in some instances their use has been discontinued altogether.

By a continuous type furnace I mean one in which loading, unloading, cooling, and pre-heating, and burning all can take place simultaneously in various parts of the furnace.

At present there are two acceptedtypes of continuous furnace. Gne of these has burners fixed in one portion thereof, while through a continuous passage the ceramic material is hauled as by The intense heat prevailing in the furnace, especially in the burning zone, warps the tracks, injures the car journals, and often causes injury to the car itself.

The other type of furnace has a progressive or .migratory flame, which advances step by step about the furnace, the various tiers of ceramic material remaining stationary. This is known-as the Hoffman-type furnace. As soon as one portion of the material is burnt the flame in that portion is shut off, the material is allowed to cool and anneal, and fuel is supplied in the next forward portion of the furnace, etc.

In both types of furnace, and particularly in the Hoffman-type, the serious drawback is present that large quantities of air are drawn through those doors of the furnace, which are opened for cooling, unloading, and loading these quantities being vastly in excess of that required for combustion. A large part of this excessair is employed simply for cooling purposes, but because of the relatively continuous and uninterrupted passage through the furnace, this air comesinto the region of the flame, which latter must heat thesame and a large proportion of the available heat must be sacrificed to this end. This results in unnecessarily low fuel efficiency, and because the amount of excess air is unpredictable due tovarying atmospheric and hence draft conditions and varying number of furnace doors which are open, it is impossible to obtain substantially uniform flame and hence heating conditions; the flame is turbulent, flickering and fretful.

I avoid these really serious drawbacks by pro- 'viding a plurality of vertical valve plates or gates disposed transversely of the passage through the furnace at various points along its extent, which points are preferably selected at restricted regions of said passage, whereby, by dropping any two of said valve plates or gates, the furnace can be divided into two separate and independent portions or zones, one of which can be unloaded and loaded, while burning takes place in the other. Valves are provided cooperating with each gate, and in the burning zone the amount of air led in can be controlled accurately, just sufficient to provide proper combustion, and this regardless of the quantity of air being used for cooling purposes in the separate, independent chamber of the furnace.

The region between any two adjacent valve plates or gates of my furnace I term asection, and two valve gates will be dropped in such manner, say, as to define a cooling zone and a burning zone, separate and independent of each other.

The cooling zone will, say, have one section .devoted to cooling, another to unloading, and a third to loading. The doors of all three sections will be open, and if desired, additional air can be led in through the valves associated with'the gates. In the burning zones, incoming air which is absolutely independent of the cooling zone and which is just sumcient for thorough combustion, will be led through a section in which burning has been just terminated, so that What may be termed active cooling of the material takes place, accompanied by regenerative heating of the incoming air. In the next section active burning occurs, in the next succeeding section incipient burning is brought about, while in the following section or sections the exhaust gasespass through material awaiting burning, to pre heat the same and to cool the gases, which latter are preferably then led directly to a drier or the like.

Referring now to the cooling zone, as soon as one section has been completely cooled, the next section unloaded and the third section loaded; and as soon as in the burning zone, active cooling in the onesection has terminated, the material in the next section has been completely burned, incipient or preliminary burning has been commenced in the next section, and preheating has been accomplished in the subsequent sections, the two valve plates or gates which have been previously lowered to define the two sections in question are lifted, and the two gates im mediately forward thereof are lowered, to commence a fresh cycle of operation. The supply of fuel to the burning section is discontinued, and the supply of fuel to the next forward section,

containing a batch of material at the temperature of incipient burning, is initiated.

It is of course possible by lowering desired valve plates or gates, to form any desired number of separate and independent zones, up to the capacity of the machine, each of any desired number of'sections.

Because of my arrangement, rapid and energetic ventilation and cooling of the first or cooling zone can take place without interfering with controlled burning in the second or burning zone, and no heating is required in the burning zone of the cooling air introduced into the cooling zone.

I have found that important economies result from my construction over the conventional Hoffman-type furnace. For example, where say sixty pounds of coal are used in the Hoffman-type of continuous furnace per ton of ceramic material (as compared to the 200 or 300 pounds required by the bee-hive kiln), my furnace requires only about 50 pounds per ton, a saving of some 20%.

In other words, the Hoffman-type requires virtually half as much again of fuel as does my improved construction.

One object of my invention, therefore, is to provide a modified Hoffman-type furnace which can be subdivided into two variable independent zones.

Another object is to produce a modified Hoffman-type furnace which has a plurality of vertically slidable valve plates for dividing the furnace into a desired number of separate and independent zones of controllable size.

Another object is to subdivide a modified Hoffman-type furnace into two variable independent zones, one zone being provided with charging, discharging and cooling sections, and the other zone being provided with active-cooling, burning, and pre-heating sections.

Another objectis to provide, in a furnace of the modified Hoffman-type, energetic circulation and ventilation, so that rapid cooling of'one of two variable independent zones may be provided without interfering with regular burning in the other of the said two zones.

Another object is to provide a modified Hoffman-type furnace in which the fuel consumption is reduced materially from that of the ordinary Hoifman furnace.

Still another object is to provide a modified Hofiman-type furnace in which are eliminated the heating irregularities which are ordinarily caused by the circulation of supplementary air through the combustion gases.

Still another object is to provide a furnace of the modified Hoffman-type having tight, partially movable partitions disposed therein for subdividing the latter at will into compartments.

Still another object is to provide a furnace of the modified Hoffman type having bafiie walls disposed therein perpendicularly to the axis of the heating chamber, and provided with vertically movable valve plates for closing off at desired points-the rectangular cross-sectioned passage through said heating chamber as defined 'by said baffle walls.

Yet another object is to provide a modified Hoffman-type furnace having bafiie walls disposed perpendicular to the axis of the chamber, vertically movable valve plates and cooperating control valves, the latter opening at one end into the heating chamber and at the other end for introducing controlled quantities of air.

Other objects and advantages will more fully appear hereinafter, as the description progresses.

One at-present-preferred embodiment of my invention is shown, solely by way of example, in the accompanying drawings, wherein:

Fig. 1 is a horizontal section through a furnace according to my invention;

Fig. 2 is a vertical transverse section on line 22 of Fig. 1, and showing the valve plates or gates;

Fig. 3 is a vertical transverse section on line 33 of Fig. 1, and showing one of the valves which are associated, one to each of said gates;

Fig. 4 is a vertical transverse section taken on line 4- 1 of Fig. 1; and

Fig. 5 is a vertical transverse section taken on line 55 of Fig. 1.

Turning now to the disclosure of the drawings it will be seen that there are outer walls I of fire brick or other suitable refractory material, shown in Figs. 2-4 as preferably being slightly slanting on their exterior surfaces, across which outer walls extend a top wall 2. From this top wall 2 depends a center wall 3 which at all points along its extent terminates short of the outer walls I, so as to provide a continuous and uninterrupted,

substantially annular passage 4 throughout the extent of the furnace. While this passage is shown as being substantially rectangular in cross section, it of course may be of any other desired cross section.

Bafile walls 5 are shown in Figs. 1 and 2 as projeoting outwardly and downwardly from the center wall 3 and top wall 2, respectively.

These baiiie walls divide the furnace into a plurality of sections I-VIII inclusive, which may be referred to as series-connected, although of course there may be any desired number of sections, each section being provided with one or more doors 6, which can be filled at the desired time with fire brick, cement, or the like 1.

Between each of the ballle walls and the adjacent outer walls (and it is to be understood that the bafile walls might just as readily project inwardly, from the outer wall) there is provided a valve plate or gate 8 preferably of steel, iron,

or the like, and preferably slidable vertically in slides or guides 9, and actuatable from the exterior, preferably from the top, by suitable means such as the rack shaft if], the gear box H, and the crank l2. This construction may be identical for each door, so that the control means for but a single door has been illustrated.

Associated with each gate 8, and preferably located immediately forward of the corresponding gate in the direction of progression (as shown by the arrows I3), is a valve 14, perhaps best shown in Fig. 3. Preferably, this valve is provided in the outer walls i, and consists of a conduit 15 communicating at one end with the passage 4, and at the other end, through the control IS, with the atmosphere at the top or 9 side of the furnace.

. Extending longitudinally through the center wall 3 are preferably provided two conduits l1 and E8, the upper one I! of which is adapted to lead away hot air from the intensely cooling section to means such as a drier, the lower conduit l8 serving to conduct away the products of combustion, exhaust gases, etc. to a suitable place, for example to any desired heat exchange device.

To accomplish its intended function, the conduit ll is shown in Fig. 5 as being connected through a feeder E9 to a removable header or manifold 29, there being a feeder 19 for each section I-VIII, one or more conduits 2| being provided in each section for cooperation with the ill Lin

"said header, and also opening into the passage 4. These headers or manifolds can be moved at will from section to section. In addition to the function described in the foregoing, the said conduits 2 I, 2|, when the header 20 is removed therefrom, also serve as inlets for the fuel.

A second valve disc 21 is shown in Fig. 5 as seating on the outlet 28 of feeder I9. It is shown as provided with a shaft 29 adapted to be con"- trolled by means such as the hand wheel 30. It is of course to be understood that any desired dual control for the two valve discs can be used, the one illustrated being shown merely by way of example. A second packing gland 3i is shown as sealing the chamber I1 against the atmosphere at the points where the shafts 24 pass therethrough.

As also shown in Fig. 4, a conduit feeder 22, provided one for each section I-VIII, interconnects the passage 4 and the exhaust gas conduit I8. Preferably this conduit I3 is controlled as by means of a valve disc 23 shown as fast on a shaft 24 extending to the exterior where it terminates in a hand-wheel 25 or other suitable control. Packing 26 preferably seals conduits I1 and I8 against each other.

The operation of my furnace is as follows:

Assume that brick, tile or other ceramic product has already been burnt in the upper part of the furnace of Fig. 1, while burning is being undergone in the lower part thereof. By dropping the two gates 3 as indicated, the furnace is divided into two separate and independent zones a so-called burning zone, and a cooling zone. As much air as desired can be introduced into the cooling zone, to bring about active cooling, without in any way whatsoever deleteriously affecting the combustion in the burning zone, which receives a controllable and absolutely independent supply of combustion air. In the said burning zone the combustion air is carefully controlled by means of air admitted only through that valve Id which is immediately infront of the second gate which is dropped, looking in the direction of the arrows I3 in Fig. 1.

The gates having been dropped, the fire brick and cement can all be removed from the doors 8 in the cooling zone.

Section IV, which has the last section of the cooling zone to be unsealed is undergoing active cooling. To this end the doors 6 will have been opened, as pointed out in the foregoing, and if desired, the valve It may also be opened, to introduce as much cooling air as is possible.

This cooling air will be considerably heated by the hot ceramic material in the section, and in order to utilize this heat as advantageously as possible, the exhaust air, now heated, will be drawn off, as shown in Fig. 5, through the conduits 2| to the header or manifold 20, which has been placed in position over this section IV, and thence through the feeder I9 to the conduit I1, and thence to the drier.

Section III, already cooled, is undergoing unloading, while at the same time, section II, previously cooled and unloaded, is undergoing loading with fresh ceramic material will be burnt after which the doors of this section will be sealed in the usual manner.

In the meantime, in the burning zone fuel is introduced into section VI through conduits 2| and active burning takes place in that section. The combustion air is preferably supplied through the valve I4 in the section V, this air, coming through the conduit I5 just in front of the closed gate 8 of steel or other metal construction, cool ing the same and protecting it from destructively high temperatures.

In the section V is ceramic material which has just-been burnt, so that this section marks the end of burning or preliminary cooling stage. By regenerative heating, the incoming combustion air is pro-heated, while at the same time the ceramic products are partly cooled.

The pre-heated air follows the passage 4 into the burning chamber VI, where it ignites the fuel introduced through the conduits 2|. Controllable suction preferably is applied to conduit I8, so that a circulation of air is created in the direction of the arrows I3, whereby the products of combustion form the burning in section VI are carried over into section VII, where the preheated ceramic material is brought up to a temperature of incipient burning, this section consequently being known as a section of beginning of burning.

The products of combustion then pass through sections VIII and I, pre-heating the material therein, and being cooled in the process. Only the valve disc 23 of section I has been opened, so the products of combustion do not escape from the passage 4 through the conduit 22 into the conduit I8 until they have entered the section I. From the conduit IS the products of combustion are sucked or otherwise conveyed into a suitable heat exchange device, not shown.

After operations in both the burning and cooling zones or chambers have been completed, the supply of fuel in section VI is discontinued, the

gates of section II and V (now loaded and doors sealed) are closed, and those of sections I and IV are opened. Fuel is supplied in section VII and the combustion air is led in through the valve I4 of section VI, the products of combustion being led into conduit I8 through the conduit 22 and valve disc 23 of section II. In the cooling zone the valve I4 and valve disc 21 of section V are opened, and shortly thereafter, sufficient cooling having occurred, and the heated air having been drawn off through conduit IT to the drier, the doors 6 of that section are broken open.

It is obvious that if for any reason such procedure is advantageous, as many gates 8 can be dropped as desired, forming any desired number of zones up to the maximum number of sections there are in the furnace, in this case eight.

It is obvious that once the broad features of my invention are disclosed, many adaptations and modifications will readily occur to those skilled in the art, all falling within the scope of my invention. Accordingly, I intend to be limited only by the scope of the appended claims, wherein I claim:

1. A continuously operable furnace of the Holiman-type, comprising outer masonry walls, and an inner masonry wall spaced from said outer wall, the said outer and inner walls defining between them a passage for the flow of gases, a plurality of masonry bafiles extending from said walls into said passage, the said bafiles extending alternately from the outer and inner walls, valve plates slidable vertically and disposed between those bafiles extending from a selected one of said outer and inner walls and the adjacent masonry wall, for controlling the cross-section of and for closing said passage, adjacent bafiies defining between them a section, a door extending through the outer masonry Wall, and providing a communication to the exterior for each section, and a valve disposed in the outer walls adjacent each of said valve plates, for the controlled intake of combustion air.

2. A continuously operable furnace of the Hoifman-type, comprising outer masonry walls, and an inner masonry wall spaced from said outer walls, the outer and inner walls defining between them a passage for the flow of gases, a plurality of masonry baffles extending from said walls into said passage, valve plates slidable'vertically and disposed between at least certain of said battles and the adjacent masonry Wall, for controlling the cross-section of and for closing said passage,

adacent baffles defining between them a section, a door for each section extending through an outer masonry wall and providing communication with the exterior, and a valve disposed in the outer walls adjacent each of said valve plates, for the controlled intake of combustion air.

3. A continuous type furnace, comprising a plurality of series-connected sections disposed in the form of a continuous path, and having a normally continuous passage therethrough, slidable gates for closing off the sections to form two or more separate and independent zones of any desired number of sections up to the capacity ofthe furnace, and means for moving said gates and for adjusting their position so as to control the dimensions of the apertures defined by said gates.

4. A continuous type furnace, comprising a plurality of series-connected sections disposed in the form of a continuous path, and having a normally continuous passage therethrough, at least one bafile wall for each section extending transversely across said passage to a position short of the opposite wall, means slidable between said baffle walls and the adjacent wall for closing off the sections to form two or more separate and independent zones of any desired number of sections up to the capacity of the furnace, and means for moving said slidable means and for adjusting the latter so as to control the dimensions of the apertures defined by said slidable means.

5. A continuous type furnace, comprising a plurality of series-connected sections disposed in the form of a continuous path, and having a normally continuous passage therethrough, at least one baflie wall for each section extending transversely across said passage to a position short of the opposite wall, slidable gates slidable between said bafiie walls and the adjacent wall for closing off the sections to form two or more separate and independent zones of any desired number of sections up to the capacity of the furnace, and means for moving said gates and for adjusting their position so as to control the dimensions of the apertures defined by said gates.

6. A continuous type furnace, comprising a plurality of series-connected sections disposed in the form of a continuous path, and having a normally continuous passage therethrough, vertically slidable gates for closing off the sections to form two or more separate and independent zones of any desired number of sections up to the capacity of the furnace, and means in advance of each gate for introducing a controlled amount of air to the particular furnace section.

7. A continuous type furnace, comprising a plurality of series-connected sections disposed in the form of a continuous path, and having a normally continuous passage theretnrough, vertically slidable gates for closing off the sections to form two or more separate and independent zones of any desired number of sections up to the capacity of the furnace, and valves communicating with the exterior and disposed one in advance of each gate in the direction of progression about the furnace, and adjacent its corresponding gate, for introducing a controlled amount of air to the particular furnace section.

ETIENNE JEAN DUSSERIS.

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