EP0046994A1 - Roller hearth furnace - Google Patents

Abstract

The cooling zone (K.Z.) pertains to a furnace, preferably a roller furnace, comprising a preheating zone (V.Z.), a firing zone (B.Z.) and a cooling zone (K.Z.). The articles to be fired, preferably ceramic slabs or plates, are conveyed through that furnace, in one layer without refractory material support. The zone (K.Z.) is indirectly cooled in order to prevent, in this zone (K.Z.) and its neighbourings, the atmosphere from acting on the articles to be treated, thereby avoiding a re-oxidation of said articles (B), and it is possible to act on their outer surface in a simple manner by means of a heat-carrying flow, preferably a heat-conveying fluid. The cooling zone comprises members which are adjustable in direction and flow rate for injecting materials acting on the surface of the articles. The indirect cooling is achieved preferably by means of coils (3) arranged above the articles to be subjected to the firing (B); their radiating surfaces may be masked in an adjustable fashion (in 5) and are arranged transversely with respect to the direction of movement of the articles. The masking elements (5) may be pivoted to swing like the blades of a blind or be made of sliding plates, movable towards each other. The coils (3) may be connected with other parts of the furnace, or with heat recovery installations.

Description

The invention relates to the design of the cooling zone for a furnace consisting of a preheating, firing and cooling zone, preferably a roller furnace, through which the firing material, preferably ceramic tiles, is passed in one layer without supporting firing aids made of refractory material.

In the case of roller kilns burning in a single layer and without firing aids made of refractory material, the kiln passes through the preheating, burning and cooling zone on a roller carpet, the rollers of which are made of special steel or ceramic refractory material are driven from outside the furnace. The particular advantage of these ovens is that there is no need for trolleys or fireproof kiln furniture. These means of transport and support represent a considerable amount Mass that must be heated by the oven and brought to cool in the cooling zone. A considerable part of the energy supplied to the furnace for the firing of the material to be burned is thus wasted.

Such furnaces operated in one layer and without the use of transport and firing aids not only achieve substantial energy savings, but the firing process can also be carried out faster and more uniformly. This leads to significantly shortened production cycles.

In the cooling zone of such ovens, so-called tumble cooling is generally used, i.e. Appropriate amounts of air are introduced into the cooling zone and brought into effect on the firing material. This inevitably results, even if the firing zone is closed off from the cooling zone by an apron, to repercussions from the cooling zone into the firing zone and, if this is operated in a reducing manner, to reoxidation of the combustible material in the cooling zone and at least in the area adjacent to the cooling zone the burning zone. If you want to prevent such reoxidation of the firing material in the cooling zone and a repercussion of the reoxidation in the areas of the firing zone adjacent to the cooling zone, this can be done according to DE-OS 28 24 367, for example, by reducing the agents in the cooling zone enters the furnace intermittently under high pressure and in such proportions and intervals that the excess of the reducing agent portion remaining after each partial reduction achieved by inputting a portion is so small that it burns down in the pauses between successive inputs without additional air supply through the neutral furnace atmosphere becomes.

It can be seen that to carry out such a procedure an extremely complicated tax system is required.

The object of the invention is to use the simplest means to prevent the combustion goods in the cooling zone and in the area adjacent to the cooling zone from being affected by the atmosphere of the cooling zone and thus a corresponding reoxidation of the combustion goods and to provide a simple way of influencing the surface of the combustion goods .

This object is achieved according to the invention in that the cooling zone is indirectly cooled by means of a flowing heat transfer medium, preferably a liquid heat transfer medium, and has introduction elements for the surface of the combustion material which influence the direction and throughput of the inlet elements.

When using a liquid heat transfer medium, for example water, which is led through coils or registers in the cooling zone above the material to be fired, there is also a sudden cooling of the fuel in the cooling zone, but without the risk of the atmosphere being influenced by the cooling air introduced. At the same time, however, a practically calm atmosphere is created in the cooling zone, with which it is now possible to introduce air or another medium that influences the surface of the material to be controlled into the cooling zone in terms of quantity and direction. For example, an appropriate gas or vapor can be introduced to influence the glaze.

In order to avoid that from the pipe coils or registers leading to the heat transfer flaking scale or the like falls on the firing material, these pipe coils or register can be shielded against the firing material, the radiation surfaces of the heat carrier leading in a further embodiment of the invention regulate the coils or registers against the firing material. bar are shielded, so that not only the firing material is protected, but the cooling process can also be controlled in any and optimal way.

The coils or coils are preferably arranged transversely to the direction of travel of the firing material through the furnace, because then the feeding and removal of the heat transfer medium is particularly simple. The arrangement and operation of the shield 14st is much simpler with such an arrangement of the coils or coils.

The adjustable shielding preferably consists of rotatable, paddle-like elements arranged in the manner of blinds. In the closed state of the shielding, these elements cover the cooling coils or registers practically completely and, by turning them slightly, leave slots free through which the strongly cooled atmosphere present around the cooling coils or registers can suddenly fall down on the firing material.

Instead of the blind-like curtains, slotted plates can also be used, which can be pushed over each other in the desired manner so that more or less large openings are available for the passage of the cooled atmosphere down onto the firing material. Due to the adjustability of the shielding, it is also possible to influence the cooling process in the cooling zone in any way.

A major advantage of the invention is that the pipe coils or registers carrying the heat transfer medium can be connected to the heat-recovering or reusable systems or furnace parts.

• Fig. 1 eine schematische Draufsicht auf einen Brennofen;
• Fig. 2 einen Schnitt längs der Linie II-II der Fig. 1;
• Fig. 3 einen Teillängsschnitt.durch die Kühlzone.

The drawing shows in

• Figure 1 is a schematic plan view of a kiln.
• Fig. 2 is a section along the line II-II of Fig. 1;
• 3 shows a partial longitudinal section through the cooling zone.

In a furnace charged with the material to be burned, in particular ceramic plates, in the direction of arrow A, a preheating zone VZ, a firing zone BZ which is heated in the direction of arrows B by a burner, and a cooling zone KZ are provided, from which the finished and fired cooled fired material emerges. The fired material B is transported through the furnace by means of rollers, one of which can be seen at 1 in FIG. 2 and several, also denoted by 1 in FIG. 3. Such rollers form a roller carpet from the furnace inlet to the furnace outlet and are driven from the outside, so that they convey the firing material B stored on them through the furnace. In the cooling zone KZ, cooling has so far been carried out by cooling air, which was introduced into the cooling zone by means of fans attached above and below the roller carpet. In spite of a skirt between the combustion zone and the cooling zone indicated at 2 in FIG. 1, it is not possible to prevent this cooling air from reacting to the combustion zone and thus from influencing the atmosphere there. According to a feature of the invention, the combustion of the material B to be burned in the cooling zone KZ is not carried out by blowing in cooling air, but by indirect cooling by means of a flowing heat transfer medium, preferably a liquid heat transfer medium, such as water, through the cooling coils, which are preferably laid transversely to the direction of travel of the combustion material -register 3 is passed in the upper part of the cooling zone. The atmosphere in the cooling zone remains at rest and there can be no retroactive effect in the firing zone. A reducing gas, salt vapors or similar media influencing the surface of the fired material in the desired manner are introduced into this static atmosphere, for example, via lances 8 which can be controlled in terms of their direction and throughput. Since the introduction into a still atmosphere takes place, the dosing is simple and uncomplicated and can be carried out in such a way that there are no effects on: the neighboring area of the firing zone. In order to prevent any scaling or the like that may form on the cooling coils or registers 3 from falling onto the refrigerated goods, fixed shielding, as can be seen in FIG. 4, is provided, and also a shield in the form of a type of Venetian blind, as indicated at 5. This blind consists of paddle-like elements extending across the cooling zone, which can be adjusted so that they practically close the gaps between the fixed shields 4. This measure not only ensures additional protection of the firing material on the rollers 1, but it is also possible to meter the cooling process. Of course, instead of the paddle-like elements shown in FIG. 3, an arrangement can be provided which is composed of slotted plates extending transversely across the cooling zone or in the longitudinal direction of the cooling zone, the slits of which can be more or less coincident with one another, so that more or less Large openings are created through which the cooling coils or coils have a cooling effect on the fuel to be conveyed on the rollers 1.

Fireproof insulation 6 is located beneath the roller carpet consisting of rollers 1.

The cooling coils or registers 3 can be connected to systems or furnace parts in a manner not shown, for example guided to the preheating zone, so that part of the thermal energy of the heat transfer medium can be used there to preheat the combustion material. The amounts of heat absorbed by the heat transfer medium can also be used in other ways, e.g. continue to use for drying.

Claims (6)

1. Cooling zone for a preheating, firing and cooling zone furnace, preferably roller furnace, through which the material to be burned, preferably ceramic tiles, is passed without a supporting firing aid made of refractory material, characterized in that the cooling zone by means of a flowing Heat transfer medium, preferably a liquid heat transfer medium, is indirectly cooled, and has insertion elements which can be adjusted in their direction and throughput for media influencing the surface of the combustion material. 2. Cooling zone according to claim 1, characterized in that the heat transfer pipe coils or registers are arranged in the cooling zone above the kiln, the radiation surfaces are shielded controllably against the kiln. 3. Cooling zone according to claim 2, characterized in that the coils or registers are arranged transversely to the direction of travel of the material to be burned. 4. Cooling zone according to claim 2 or 3, characterized in that the shield consists of rotatable paddle-like elements arranged in the manner of blinds. 5. Cooling zone according to claim 2 or 3, characterized in that the shield consists of mutually displaceable slot plates. 6. Cooling zone according to one or more of the preceding claims, characterized in that the pipe coils or registers carrying the heat transfer medium are connected to the heat-recovering or reusable systems or furnace parts.

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