DE29614958U1 - Device for degassing and cooling stacked ceramic items in continuous furnaces - Google Patents

Description

Responsible: Andreas Hässler, Jahnstraße 45, 89155 Erbach

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BY REGISTERED MAIL

To the

German Patent Office

Zweibrückenstrasse 12

80331 Munich 2

Erbach, 26.08.1996

Device for degassing and cooling of stacked ceramics, firing material in continuous furnace

When firing ceramic fired goods, e.g. bricks with cross heating slots placed on firing carriages for stacking, problems with even temperature distribution in the firing stacks occur in both the heating and cooling zones. This results in longer heating and cooling times with reduced performance of the tunnel kiln. With the development of large-format porous perforated bricks with increased thermal insulation capacity, firing carriage sets are often stacked in a largely dense manner so that the kiln gas flows around these stacks rather than through the inside of the stack. This leads to thermal stresses on the individual bricks, which leads to firing damage. Furthermore, degassing in the heating zone inside the stack cannot be achieved if, for example, large quantities of sawdust have to be degassed. Undesirable carbon often remains in the bricks after the firing process. Although the perforated bricks are preferably placed on the kiln carriage with their hole direction facing the flow direction, almost no kiln gas flows through the horizontal perforation, _t

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Responsible: Andreas Hässler, Jahnstrasse 45, 8.9155 ErJiacfa.

because the relatively small hole cross-sections have too much air resistance compared to the large edge and ceiling gaps in the oven.

The large inner surfaces of the holes in such perforated bricks would be useful heat transfer surfaces for faster heating, degassing and cooling. The final cooling of such firing stacks is often not satisfactory with shorter firing times, so that considerable heat losses are recorded as a result of the firing material coming out of the kiln being too hot. This results in higher fuel consumption and CO2 emissions.
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The object of the invention is therefore to provide a device which improves the above conditions so that faster heating, degassing and/or cooling of bricks, in particular perforated bricks, stacked on top of one another on firing carriages becomes possible.

According to the state of the art, devices for rapid cooling of firing charges in tunnel kilns are known. These consist of devices for blowing cooling air over the kiln roof or kiln wall into transverse heating slots, preferably above the quartz modification of approx. 575 °C.

However, they do not cause heat exchange inside the combustion stack to any significant extent, even if a circulation zone above the quartz jump area with furnace gas is used for rapid cooling.

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Abs.: Andreas Hässler, Jahnstraße 45, 8.9155 ErJvactu

The object of the invention is therefore to create a device that can be used in a variety of different furnace zones of tunnel furnaces in order to:

A) to improve the heating, degassing and oxidation of organic material in the bricks and brick stacks.

B) to improve rapid cooling and make it more effective.

C) to improve the cooling down to the final cooling so that the firing material can be cooled to near the outside air temperature.

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Abs.: Andreas Kassier, Jahnstraße 45, Ü915.5

I · O ·

According to the invention, according to Fig. 1 (longitudinal section of a tunnel kiln (I)), the firing material placed on firing carriages (2) to form firing stacks (3) passes through a tunnel kiln (1) with a heating zone (4), firing zone (5) and cooling zone (6). In zones 4 and/or 6, horizontal blowpipes (8) in the transverse heating slots (9) between the firing stacks (3) are moved up and down at a suitable point via devices (7) that can be raised and lowered, whereby the firing stacks are intensively flowed through in a horizontal direction. The air supply to the blowpipes (8) takes place via vertical air pipes (10) and blowers (11) connected to them. Since the transverse heating slots (9) are usually about 200 - 400 mm wide, the horizontal outlet openings (12) of the blowpipes (8) on one or both sides are very close to the firing stacks and the open holes in the bricks, so that no very high pressures or outlet speeds are required to guide the air fed into and through the holes in the moldings. This also means that a tolerable amount of force is required to bring the air to the location of the large heat transfer surfaces inside the stack. Depending on where the device according to the invention is used, the cross sections and pressures must be designed differently.

In the cooling zone, larger air volumes are required for the cooling effect combined with lower conveying pressures. In the heating zone, where a cooling effect is undesirable, it is more important to expel the carbonization gases from the interior of the stack, by means of higher pressures and minimized air volumes.

In the final cooling zone, large amounts of air are permitted. One effect of the invention is the possibility of counteracting the vertical temperature stratification in the oven with annoying differential cooling.

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- Sheet 5 -

Abs.: Andreas Hässler, Jahnstraße 45,,&thgr;·$^5*&idigr;

The blowing time can be controlled differently at different combustion channel heights by differentiating the stroke times and speeds.

Fig. 2 shows an example of a furnace cross-section with a horizontal blowpipe and two vertical air pipes. Fig. 3 shows a design with a large number of vertical air pipes.

Fig. 4 shows vertical feed pipes that can be raised and lowered in a cross heating slot with horizontally acting blow-out openings, which are also directed towards the side surfaces of the stack of perforated bricks. Fig. 5 shows the horizontal section AA of the embodiment according to Fig. 4 (section through the firing channel and stack filling). Fig. 4 also shows a thermocouple (13) that is carried along, e.g. at the tip of a feed pipe, with which the vertical temperature curve in the respective cross heating slot is continuously recorded. From this curve, the required cooling capacity in the respective height range is then controlled according to the invention by means of variable dwell times of the blow-out openings and/or the amount of cooling air. /*%7

Claims (1)

Abs. : Andreas Kassier, Jahnstraße 45, 89155 Erbach BY REGISTERED MAIL To the German Patent Office Zweibrückenstrasse 12 80331 Munich 2 Erbach, 26.08.1996 EXPECTATIONS Claim 1 Device for heating, degassing, rapid cooling and final cooling of ceramic products, in particular perforated porous lightweight bricks in tunnel kilns, which are stacked on firing carriages with horizontal perforations, with transverse heating slots in between and periodic carriage advance, characterized in that horizontal blow pipes (8) with essentially horizontal air or gas outlet openings (12) on one or both sides are arranged transversely to the longitudinal axis of the kiln, can be raised and lowered in transverse heating slots, and are connected to vertical air pipes and fed with air or kiln gas via blowers. Claim 2 Device according to claim 1, characterized in that the blowpipes (8) are arranged divided into several blowpipes over the combustion channel width. /2 - Page 2 - Abs.: Andreas Hässler, Jahnstraße 45, ß _s 915,5 Erwach, Claim 3 Device according to claim 1 + 2, characterized in that the device is arranged several times on the tunnel furnace and is connected to an individual or total air supply. Claim 4 Device according to claims 1-3, characterized in that a group of air pipes that can be raised and lowered with blow-out openings arranged and acting horizontally on one or both sides are arranged next to one another in one (or more) transverse heating slots transverse to the combustion channel direction. Claim 5 Device according to claims 1-4, characterized in that the lifting and lowering speed of the blowpipes and the lifting height are automatically controlled in an adjustable manner. Claim 6 Device according to claims 1-5, characterized in that at least one blowpipe or supply pipe carries a conductive thermocouple that can be raised and lowered, for continuously recording the vertical temperature profile in the cross heating slot and regulating the blowing duration or the air quantity in areas of temperature deviations in the cross heating slot.