ITRE960008A1 - COOLING ELEMENT, PARTICULARLY FOR OVENS COOLING ELEMENT, PARTICULARLY FOR TUNNEL TUNNEL OVENS - Google Patents

Abstract

Process for the treatment of styrene to obtain pyroresistance characteristics and in particular for the conferment of these characteristics to the expanded and extruded polystyrene consisting in mixing intimately to the liquid monomer styrene a quantity of silicon variable according to the desired pyroresistance characteristics before the polymerization process .

Description

DESCRIPTION

of the Patent for Industrial Invention entitled: COOLING ELEMENT, PARTICULARLY FOR TUNNEL OVENS,

The present invention relates to kilns for tiles in general, and to so-called single-layer tunnel kilns in particular.

In these devices, the possibility is of particular importance. to regulate the cooling in the terminal section of the oven, in order to preserve not only the integrity? of the material, but also its geometric characteristics.

In fact, it is considered indispensable not only that the cooling of the terminal section of the furnace takes place according to a rigorously established cooling curve, but also and above all that the temperature of the furnace remains homogeneous in every point of the same cross section of the furnace, both above and below the tile.

The cooling curve should generally be the same both above and below the tile.

However for certain particular products? required, in order to obtain flatness, that the cooling curve also differs considerably from the top and bottom of the product.

In other words in certain cases? it is desirable to be able to differentiate also sensibly, but always in a strictly controlled way, the action d? cooling on the two faces of the tile, while maintaining said homogeneous action in the transversal sense.

This need? imposed by the fact that if one face of the tile? subjected to a temperature even slightly different from the convenient one, then it can? fail the planarity? of the tile itself.

It is known to regulate the temperature of the various sections of the kiln by introducing air at room temperature, through perforated manifolds which affect both the upper surface of the tiles and the lower one.

The entity? cooling is adjusted according to the quantity? of air introduced, in the sense that obviously you will have? greater cooling by introducing a high air flow rate, and if you want to reduce the cooling, the flow rate must be reduced.

The determination of the scope? generally enslaved to means controlled by suitable temperature detectors placed in the various sections of the furnace. Despite the widespread use of the aforementioned cooling systems, isn't it? up to now it has been possible to obtain an adjustment as precise as it would be necessary, and what about it? ? mainly due to the difficulty? to regulate the air flow rates in a sufficiently accurate way, in order to be able to obtain even large temperature differences between above and below the roller surface in a homogeneous way in the cross section of the furnace, especially in single-layer furnaces with considerable widths. The purpose of this patent? to make available cooling gas distribution means whose thermal effect can be regulated with greater precision.

This purpose? achieved by the invention thanks to cooling gas distribution means equipped with devices adapted to regulate the temperature of the gas distributed by them.

Said distribution means can be made of a manifold having for example the shape of a tubular body closed at one end, equipped with radial openings directed towards the roller conveyor of the kiln, and whose length covers the entire width of the kiln, to which they are associated gas supply means at a controlled temperature and flow rate.

The latter consist of a pressure fan which feeds a flow of pressurized ambient air inside said tubular manifold, through a gas burner which in turn discharges the burnt gases mixed with the excess air.

Alternatively, the blower fan supplies, through a derivation, the correct quantity? of combustion air to the burner, and through another room air derivation directly into the manifold.

In this way the gas intended to cool the tiles will be able to? if necessary, have temperatures even higher than those of the ambient air, allowing to maintain the desired temperature gradient on the two faces of the tile. The advantages and the functional and constructive characteristics of the invention will be evident from the following detailed description, which with the figures of the attached drawings illustrates two particular preferred embodiments given by way of non-limiting example.

FIG. 1 shows a cross section of the oven in correspondence with a first embodiment of the invention.

FIG. 2 shows an enlarged and partial section of the oven in correspondence with a second embodiment of the invention.

FIG. 3? section III-III of FIG. 1.

The figures show the side walls 1 and 2 of a single-layer tunnel kiln, built in refractory masonry, between which the rotating rollers 3 of a roller surface on which the tiles 4 travel are supported.

Said tiles are equidistant both in the longitudinal direction and in the direction transverse to the motion, and are subjected to firing in the sections of the kiln upstream of those illustrated, according to a very rigorous temperature curve.

After the prescribed permanence at the maximum firing temperature, regardless of the means by which the heating is carried out, the tiles must begin to cool progressively and uniformly until they come out of the kiln.

According to the invention, cooling takes place by introducing gas into the kiln obviously having a temperature lower than that of the tiles, but such as not to damage them by creating internal tensions.

The internal tensions due to uncontrollable cooling on the two faces of the tile cause a series of drawbacks well known to those skilled in the art, not least the loss of planarity. of the tile.

This is the reason why the cooling is done by introducing ambient air with great caution, in a very long time, which negatively affects both the length of the oven and the duration of the cycle, with all that this entails in economic terms.

According to the invention, hollow manifolds 5 are provided, placed transversely to the oven, both above and below the roller conveyor 3, of a tubular shape for example closed at one end. and facing the other end? outside the oven wall 2.

These collectors are made of material suitable to withstand the high temperatures existing inside the furnace, such as silicon carbide or tungsten-based materials. The manifolds 5 have openings 6.

The openings 6 can be placed on one or more? alignments and are preferably radial equidistant and aligned, facing the roller plane.

They have a different section in order to guarantee the same cooling effect over the entire width of the oven.

Outside the wall 2 of the furnace, means are provided for supplying cooling gas at a strictly controlled flow rate and temperature. According to the solution illustrated in Fig. 1, said means consist of a gas burner 7 whose combustion air? fed in excess by a blower fan 8.

On the delivery duct of fan 8? preferably a capacity control valve, indicated with 9 and controlled by an external servomechanism 10, is placed.

Also shown in Fig. 1 are the gas supply pipe 11 to the burner 7 and the wires 12 which control its ignition and shutdown.

The servomechanism 10 and the ignition and shutdown means of the burner 7 are controlled by an externally programmable microprocessor 13 which receives the signals from a thermal probe 14 placed inside the oven.

The test form? illustrated? suitable to be applied to those sections of the oven placed in the most? hot, since? its cooling action can not? overcome certain limits.

The cooling action of the test device? described? maximum when ambient air is supplied at maximum flow rate, and minimum when the burner is kept on.

The intermediate conditions are possible thanks to the intermittent shutdown of the burner and the regulation of the valve 9, controlled by the microprocessor 13.

The air fed by the fan 8 can not? exceed certain ranges, as an excess of oxygen causes instability? into the burner flame. When? the cooling action must be more? energetic, the embodiment of the invention illustrated in FIG. 2.

In it the same numerical references have been used to distinguish the parts in common with FIG. 1.

From FIG. 2 it can be seen that in correspondence of the extremity? open of collector 5? a mixing chamber 15 is placed, obviously made of material similar to the material of the manifold 5. In said chamber? the burner 7 is inserted, and the forced air supply duct 80 leads into it, throttled by the valve 9 enslaved by the servomechanism 10.

Conduit 80? a branch of the delivery duct of the fan 8, and? placed in parallel with a further derivation 81 which feeds, in the quantity? strictly necessary, the combustion air to the burner 7.

Thanks to the aforementioned provision, you can? feed a desired quantity? of ambient air regardless of the needs? of the burner. Do you get with there? the desired cooling effect.

It is hardly necessary to specify that the cooling elements referred to above, with their respective feeding and adjustment means, are arranged both above and below the roller conveyor and distributed throughout the final part of the oven, mainly in the rapid cooling zone.

Claims (5)

CLAIMS 1. Cooling element particularly for tunnel furnaces equipped with a roller conveyor for transporting the material, characterized by comprising a manifold placed transversely to a section of the furnace and equipped with equidistant and aligned radial openings directed towards the roller conveyor of the furnace; means associated with the extremity? said manifold for generating a cooling gas composed of a mixture of ambient air and combustion gas from a burner; a temperature sensing probe inside the furnace in the section comprising the manifold, and means for controlling the flow rate and temperature of said mixture in response to the signals of said probe. 2. Cooling element according to claim 1, characterized by the fact that said cooling gas generating means comprise a gas burner, a blower fan which supplies excess combustion air to said gas burner and partialising means of the air supplied by said fan, a microprocessor being further provided for the control of said valve and of the ignition times of said burner in response to the signals of the thermal probe, and according to the instructions received from the outside. 3. Cooling element according to claim 1, characterized in that said cooling gas generating means comprise a mixing chamber external to the manifold, within which? fixed a gas burner, as well as? a blower fan that feeds combustion air directly to said burner d? gas, and ambient air directly inside said mixing chamber, with partializing means for the air fed from said fan to said mixing chamber being provided, and it being provided that the regulation of said valve and of the ignition times of said burner are enslaved, through an externally programmable microprocessor, to the signals of the thermal probe. 4. Cooling element according to the preceding claims, characterized in that the collector has a circular section. 5. Cooling element according to the preceding claims, characterized in that? intended to be arranged both above and below the roller conveyor of the oven, in various sections of the terminal section of the same.