US2126881A - Apparatus for firing ceramic material - Google Patents

Description

Aug. 16, 1938. P. GATZKE 2,126,331

APPARATUS FOR FIRING CERAMIC MATERIAL Filed Dec. 9, 1935 2 Sheets-Shem. 1

Aug. 16, 1938. P. GATZKE 2,125,331

APPARATUS FOR FIRING CERAMIC MATERIAL Filed Dec. 9, 1935 2 Sheets-Sheet 2 gwuam-foz Paul 609 429 2354;; (QWM Patented Aug. 16, 1938 UNITED STATES PATENT OFFICE APPARATUS FOR FIRING CERAMIC MATERIAL Paul Gatzke. Berlin-Pankow, Germany 15 Claims.

This invention relates to a process and apparatus for firing ceramic material and particularly porcelain, hereinafter referred to generally as ceramic ware, in indirectly heated tunnel furnaces, in which term is included electrically heated tunnel furnaces.

In the treatment of porcelain in tunnel furnaces for the purpose of producing a spotlessly white porcelain, the atmosphere in the individual zones of the furnace tunnel, that is during the individual phases of the firing treatment, must be regulated according to accurately predetermined condition. As a rule, until the sintering temperature is reached a reducing followed by neutral and finally oxidizing firing is carried out, but these conditions vary in individual cases according to the composition of the mass and the kind of material to be fired. In certain circumstances it may, for example, even be found advisable to reverse the firing sequence, that is to employ at the commencement oxidizing, later neutral and finally reducing firing.

The production of a suitably graded furnace atmosphere presents no particular diiiflculties in gas heated tunnel furnaces with separately adjustable burners hitherto generally used for the firing of porcelain. Also in the case of tunnel furnaces heated with solid fuels it is possible to attain this by the arrangement of, for example, supplementary firings having a reducing action.

However, difficulties are encountered in infiuencing the composition of the furnace atmosphere in electrically and indirectly heated tunnel furnaces to which the present invention is chiefly concerned, since in such furnaces, which in themselves produce oxidizing firing and the heating of which does not influence the composition of the furnace atmosphere, it necessitates a separate introduction of gases exerting a reducing effect into the zones of the furnace in which a reducing firing must be carried out.

This might be effected by introducing suitably composed gases, that is primarily gases containing C0 for example, in the same way as gases containing oxygen, 1. e. air, are introduced into the oxidizing zone, but this presents technical and economical difficulties because these reducing gases must be procured as such or produced in a separate plant, the working of which requires great care owing to the danger of explosion.

Experiments to produce as an alternative carbon monoxide at suitable points in the furnace by incomplete combustion of fuels have shown that this procedure is not possible without spe- (Cl. 25142i cial measures, because it is neither possible to accurately regulate the 00 content in the individual zones, as is necessary, nor to produce any uniform reducing atmosphere over the entire cross-sectional area of the furnace tunnel. The reducing gases certainly sweep along the side surfaces and the upper portion of the charge on the firing truck, but scarcely penetrate in to the core thereof and consequently a defectively fired article results.

These objections are overcome in the best possible technical and economical way by the process according to the present invention, which renders it possible to feed the reducing gases into the interior of the furnace at such places and to distribute them so that a reducing action of the furnace atmosphere is ensured at all points of the whole charge block, that is, over the entire cross-sectional area of the tunnel. According to the invention, this result is obtained by the introduction or production of the reducing gases in the interior of the charge in the zones in nich the reducing furnace atmosphere is to be produced, by transporting through the furnace, by means of the firing truck, a reducing gas or a liquid or solid substance which produces the reduction gas by evaporation or incomplete combustion as the firing truck passes through the furnace. In the preferred arrangement for the production of the reducing gases from liquid or solid substances carried by the firing truck, the evaporation and the like takes place entirely under the automatic action of the gradually increasing temperature during the passage through the furnace, but additional methods of regulation may also be provided for this purpose.

In one form of construction according to the invention the platform of the firing truck is provided with longitudinal slots or correspondingly arranged discharge nozzles through which the reducing gas, which as a rule is the products of evaporation, gasification or combustion, are conducted directly into the core of the charge.

This is preferably effected by arranging, below a longitudinal slot or the row of nozzles in the firing truck platform, a storage receptacle, preferably of elongated shape, for accommodating the fuel which is preferably a liquid gasified by heat. This storage receptacle, although it is situated outside the furnace passage proper, heats during the passage of the firing truck owing to the gradually increasing temperatures, so that the oil or the like evaporates and the vapor from the slot enters the interior of the furnace tunnel and burns exactly at the place where the reducing gases are primarily needed, namely in the middle of the charge. In certain circumstances the gradual heating of the oil tank works satisfactorily, without auxiliary means, but if additional regulation of the existing oxygen content is desired, a particularly complete evaporation of the oil and consequently an intensive reducing effect of the furnace atmosphere precisely in the zones in which an increased reduction is required can be insured by auxiliary means. It is also possible to obtain this regulation by suitable selection of the fuel which is to be evaporated. Among the fuels concerned are chiefly liquid fuels such as oils having suitable points of evaporation for the case in question. Solid fuels may however also be used. It is also possible to regulate the production of the desired quantity of the reducing gases in the different zones of the furnace by subdividing the fuel receptacle under the firing truck platform, or providing several containers, and filling them with difierent fuels which evaporate at dificrent temperatures.

According to a further feature of the invention an additional regulation of the evaporation and consequently of the reducing effect may be provided by fitting in the oil containers or in the walls thereof. resistance heating elements. the heating efi'ect of which is controlled automatically at the corresponding points of the furnace tunnel, for example by the terminal contacts of these heating resistances sliding along contact bars arranged veiow the firing truck platform in the longitudinal direction of the furnace tunnel during the forward movement of the firing truck. the contact bars being so subdivided and supplied with such current that they produce a heating effect of the heating resistances regulated in steps.

In order to avoid a premature exhaustion of the content of the oil tank when there is a considerable consumption of reducing gases, feed conduits for the tanks may be fitted at suitable points of the furnace, through which fuel can be fed during the passage of the firing truck through the furnace.

According to a simplified form of the invention the introduction of the reducing gases can be effected alone, or in combination with the above described method, by providing over the surface of the truck platform containers (dishes or the like) for a liquid or solid substance which produces such a gas by evaporation (oils, heavy hydrocarbons, substances containing waste products,such as waste oll,or mazut (a Russian petroleum residue or other residue containing oil) said substance evaporating from said containers sole- 1y under the influence of the gradually increasing temperatures in the individual zones of the furnace passage as the truck passes through the furnace without requiring any additional regulating or heating devices, it being easily possible by a suitable selection or dimensioning of the number, the surface area and the capacity of the container, to ensure automatic production of the quantity of reducing gas which is necessary in the individual zones of the furnace for producing a furnace atmosphere having the desired reducing composition.

Instead of placing separate bowls, dishes or the like on the firing truck platform, cup-shaped recesses, may be provided therein having a surface area and depth or capacity according to the requirements of the individual case.

Instead of providing containers or the like as described above the porosity of the material of which the firing truck platform and other auxiliary means for firing are made, for example fine clay having a high degree of porosity, is utilized for accumulating the necessary quantity of substances to be evaporated for the purpose of producing the reducing gases, by saturating the fireclay material with these substances before the truck passes through the furnace. The saturation of the boxes, firing supports and other firing accessories in this manner has been found particularly advantageous owing to the direct action of the reducing gases.

Besides producing the reducing gases with the aid of the firing truck as described above it is advisable in certain circumstances to provide in the side walls of the furnace devices for feeding liquid fuels to be incompletely burned also in a suitably regulated manner, for example preferably oppositely arranged descending channels which open above the firing truck platform and to which are fed by ordinary drip lubricators regulated quantities of oil. Alternatively a similar fuel introduction is also possible from overhead, that is from the arch of the furnace tunnel using suitable dosing devices. Whether this arrange ment is suitable or whether it is advisable to fit such supplementary equipment depends upon the properties of the mass and the structures of the charge. In certain exceptional instances, for example in the case of a charge built up with wide spacing, or when the absoluteuniformity of the reducing action is not as absolutely essential as is necessary for high-grade porcelain, that is for inferior quality fired articles which must be fired under similar conditions and to which the invention can be advantageously employed, it is, in certain circumstances, possible to do without the feed of the reducing gases by means of the firing truck and to provide in its stead such a lateral or overhead oil feeding device.

In certain circumstances the slot or the row of nozzles formed in the firing truck platform may be fed with compressed reducing gas by a container arranged under and fixed to the firing truck platform, an automatic control of the outfiowing quantity of gas being rendered possible in similar manner by valves controlled by the firing truck passing through the furnace.

In order that the invention may be more clearly understood one particular form thereof (the first form described above) will now be described with reference to the accompanying drawings wherein:

Fig. 1 is a cross-section through the furnace and Fig. 2 a plan view of a firing truck platform.

Figj 3 is a cross-section through a portion of the furnace to which indirect heating is applied.

In these drawings a is the furnace tunnel proper. b the firing truck, c the platform of the firing truck on which the charge at is built up.

A longitudinal slot 9 preferably narrowing towards the top, or a row of nozzles, (not shown) is arranged in suitable manner in the firing truck platform. A container 1 which is likewise preferably of elongated shape, is situated below the slot e for the liquid fuel and therein or within its walls the heating coil 0 is arranged. This heating coil contacts with a collector h which brushes along a conductor bar i divided into sections. Oil feeding devices k are arranged at suitable points at the side of the furnace tunnel a and are provided with drip ollers l which feed the oil or other fuel in regulated quantities through inclined channels 1:: which open into the furnace slightly above the firing truck platform. The portion of the furnace which is heated indirectly is indicated somewhat diagrammatically in Fig. 3. In this view the tunnel a is shown covered by a relatively thin wall 0 which is heated from a furnace p. The products of combustion from the furnace p are conducted over wall 0 through a flue q, and from thence through checkerwork r to a chimney s. Air is drawn in through checkerwork r and fines t to the furnace. Any other suitable means may be employed for indirect heating of tunnel a, or electrical means may be employed which does not affect the gases in the tunnel.

The invention is not restricted to the forms of construction described above and those illustrated in detail in the drawings, but can be modifled in various manners without departing from the scope of the invention.

What I claim and desire to secure by Letters Patent is:

1. In apparatus of the class described the combination of a tunnel furnace, means for indirectly heating said tunnel furnace to substantially the desired temperature, a firing truck traversable through said tunnel furnace, and means transportable through said tunnel furnace on said firing truck to introduce reducing gas into the interior of a charge of ceramic ware upon said firing truck.

2. In apparatus of the class described the combination of a tunnel furnace, means for indirectly heating said tunnel furnace to substantially the desired temperature, a firing truck traversable through said tunnel furnace, means constituting a source of reducing gas transportable through said tunnel furnace on said firing truck, and means to inject said reducing gas into the core of a charge of ceramic ware upon said firing truck.

3. In apparatus of the class described, the combination of a tunnel furnace, means for indirectly heating said tunnel furnace, a firing truck including a platform for a charge of ceramic ware and traversable through said tunnel furnace and means constituting a source of reducing gas transportable through said tunnel furnace on said firing truck, said platform having a longitudinal slot therein through which reducing gas passes from said source into the interior of said charge.

4. In apparatus of the class described the combination of a tunnel furnace, means for indirectly heating said tunnel furnace, a firing truck including a platform for a charge of ceramic ware and traversable through said tunnel furnace and means constituting a source of reducing gas located beneath said platform and transportable through said tunnel furnace on said firing truck, said platform having a longitudinal slot therein narrowing towards the top and connecting with said source through which slot reducing gas is injected into the core of said charge.

5. In apparatus of the class described the combination of a tunnel furnace. means for indirectly heating said tunnel furnace, a firing truck traversable through said tunnel furnace, means constituting a source of reducing gas transportable through said tunnel furnace on said firing truck and a nozzle connecting with said source through which reducing gas is injected from said source into the core of a charge of ceramic wareupon said firing truck.

6. In apparatus of the class described, the combination of a tunnel furnace, means for indirectly heating said tunnel furnace, a firing truck including a platform for a charge of ceramic ware and traversable through said tunnel furnace, a container for compressed reducing gas located beneath said platform and transportable through said tunnel furnace on said firing truck, and means to inject reducing gas from said container into the core of said charge.

'7. In apparatus of the class described, the combination of a tunnel furnace, means for indirectly heating said tunnel furnace, a firing truck including a platform for a charge of ceramic ware and traversable through said tunnel furnace, a container for a liquid hydrocarbon located beneath said platform and transportable through said tunnel furnace on said firing truck, a resistance heating element in said container, a current collector for said heating element, a currentcarrying contact bar arranged longitudinally of said tunnel furnace along which said collector slides, and means to direct the heated liquid hydrocarbon in a substantially gaseous state into the core of said charge where it is incompletely combusted.

8. In apparatus of the class described, the combination of a tunnel furnace, means for indirectly heating said tunnel furnace to substantially the desired temperature, a firing truck including a platform for a charge of ceramic ware and traversable through said tunnel furnace and containers upon the surface of said platform for a substance producing areducing gas when exposed to the heat of the furnace, said containers being so located that the reducing gas so produced passes into the interior of said charge.

9. In apparatus of the class described, the combination of a tunnel furnace, means for indirectly heating said tunnel furnace to substantially the desired temperature, and a firing truck, including a platform constructed of porous material capable of accumulating substances which under the action of heat produce a reducing gas, traversable through said tunnel furnace.

10, In apparatus of the class described, the combination of a. tunnel furnace including side walls, means for indirectly heating said tunnel furnace, a firing truck traversable through said tunnel furnace, means transportable through said tunnel furnace on said firing truck to introduce reducing gas into the interior of a charge of ceramic were upon said firing truck, and means for feeding regulated quantities of liquid fuel through inclined channels in said side walls, which liquid fuel is incompletely combusted in said furnace to produce a reducing atmosphere. 11. In apparatus of the class described, a firing truck comprising in combination a truck body including a platform for a charge of ceramic ware, said platform having a longitudinal slot therein, and means constituting a source of reducing gas located beneath said slot through which the reducing gas passes into said charge.

12. In apparatus of the class described, a. firing truck comprising in combination a truck body including a platform for a. charge. of ceramic ware, said platform having a longitudinal slot therein narrowing towards the top, and means constituting a source of reducing gas located beneath said narrowing slot through which the reducing gas is injected into the core of said charge.

13. In apparatus of the class described, a. firing truck comprising in combination a truck body, means constituting a source of reducing gas, a nozzle connecting with said sourc e through which truck comprising in combination a truck body including a platform for a charge of ceramic ware, a container for a liquid hydrocarbon located beneath said piatform, a resistance heating element in said container, a current collector for said heating element, and means to direct the heated liquid hydrocarbon in a substantially gaseous state into the core of said charge.

PAUL GATZKE.

CERTIFICATE OF CORREOTI ON Patent No. 2,126,881.

August 16, 1958.

PAUL GA'I'ZK'E It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 51, claim 10, for the word "were" read ware; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of September, A. D. 1958.

(Seal) Henry Van Arsdale Acting commissioner of Patents.

truck comprising in combination a truck body including a platform for a charge of ceramic ware, a container for a liquid hydrocarbon located beneath said piatform, a resistance heating element in said container, a current collector for said heating element, and means to direct the heated liquid hydrocarbon in a substantially gaseous state into the core of said charge.

PAUL GATZKE.

CERTIFICATE OF CORREOTI ON Patent No. 2,126,881.

August 16, 1958.

PAUL GA'I'ZK'E It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 51, claim 10, for the word "were" read ware; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of September, A. D. 1958.

(Seal) Henry Van Arsdale Acting commissioner of Patents.

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