DE1303596B - MULTI-LAYER BURNER BLOCK FOR RADIATION BURNER - Google Patents

Description

The invention relates to multilayer ceramic burner blocks for radiant gas burners through which a mixture of flammable gases is passed and near the front of which is burned upon exiting them. Such bodies are or can be built into walls or other parts of ovens or the like be placed on the ceilings of covered walkways, if required, To transfer heat in the form of radiant energy to bodies or areas that at lower temperatures and at moderate distances from the front of the Burner blocks are located. In order to do this effectively, it is desirable that the ignited gases as close as possible to the exposed front of the burner block or even burn in the pores of the burner block, which are the exposed front are immediately adjacent. In this way, the sensible warmth or intrinsic heat trust the Brennaase on the burner block and increase its temperature so that the heat then as radiant heat to areas remote from the burner block will trust.

There have been aemacht numerous attempts to apply this Priiizip, but these attempts ledi-lich have been partially successful because the exposed surface of the burner is not "enüccnd heat C7 J Ahl, estr" ililt liat or because the ignited flame through the burner block kicked back through it and ignited the gases on the wrong side of the block, causing explosions or otherwise destroying the device.

In the Swiss patent specification 323 162 the disadvantages of known burner fittings formed from sintered or ceramic materials of radiant burners are described, whereby in particular a flashback of the flame on the gas nozzle was to be feared. To overcome the disadvantages, a burner is provided according to the Swiss patent specification, which has at least two superimposed layers of the permeable layer, of which at least the outermost consists of a gauze-like film. The layers in this radiant burner should in particular all consist of sieve-like metal grids. The layers are laid loosely on top of one another, i.e. that is, no special measures need to be taken to keep them at a certain distance from one another. Under these prerequisites, the layers touch one another in certain places, while in most places they have a small distance from one another. The provided metal grilles only allow operation up to about 800 ° C and are not backfire-proof because the inner metal grilles also heat up.

Instead of sieve-like metal grids or wire mesh, you can also other gas-permeable, gauze-like layers. z. B. thin, coarse-pored. (yesintered Layers apply. Refractory meshes made from other materials can also be used can be used as metal.

In any case, it should be the outermost one consisting of a gauze-like film Layer be dimensioned and arranged in such a way that the combustion is not behind it he follows. Expediently, the inner surface of the burner head is considered to be reflective Surface designed to throw the inwardly radiated heat back outwards. Even when using gauze-like layers made of a material other than metal the risk of reignition not excluded.

From the French patent 340 044 is a burner for acetylene gas known, the principle of which is essentially that the gas through a shell- or cylinder-like container is performed with a porous material, in particular Sand, which rests on a sieve and divides the gas flow. It educates This creates a veil of flame on the surface of the porous material. The porous Material should prevent the flame from flashing back into the interior of the burner and ensure complete combustion of the acetylene gas. The well-known burner does not represent a radiant burner capable of generating substantial radiant energy submit.

From USA. Patent 3,148,962, a non-return barrier is known to be arranged independently of a gas burner of any kind in a gas line. In the known kickback barrier, packs of particulate bodies are arranged one behind the other, the first layer consisting of a pack of loose, crooked particles and being provided next to the line to be protected. .- #, on this coarse packing follow VC for packing of finer particles. The main purpose of the first layer of coarse particle packing is to bring about a partial cooling of the gases left and to absorb heat without even reaching a surface temperature sufficient to ignite the acetylene gas. As a result of the cooling effect in the coarse layer, when the gases reach a subsequent layer of finer particles, they have a lower temperature and cannot reach a flashback temperature. The training of such a non-return barrier is not suitable to give an indication of the structure of a radiant burner from which a high level of radiant energy is emitted.

The object of the invention is to provide a robust and light to create exchangeable ceramic burner block, which a maximum proportion convert the inherent heat of the combustion gases into radiant energy and use this energy can transmit the desired area while simultaneously removing the flame from the hot Surface cannot recoil into the chamber in which the Brenn-C Clase with Air or oxygen can be premixed.

This task is performed with a ceramic burner block for radiant gas burners with several different ones lying one behind the other in the gas passage direction Layers, of which the outer as a radiation layer and the inner as a kickback protection acts, according to the invention in that the outer layer consists of a bonded A pile of silicon carbide grains and the inner layer of a bound pile of grains of heat-insulating material, e.g. B. clay grains, the The grain size of the outer layer is coarser than that of the inner layer and the gas permeability of the two layers matched to the properties and conditions of the fuel gas is that the gas permeation velocity in the outer layer is smaller and in of the inner layer is greater than the ignition speed of the gas.

Preferably the inner layer is thicker than the outer layer, in any case, it is of sufficient thickness to provide thermal insulation between the front layer and to create the flammable gases at the back of the barrier.

The invention further comprises a multilayer ceramic burner block, in which at least one additional thinner layer, the combustion, is attached to the inner layer controlling layer of an even finer heap of bound grains of heat-insulating Material, e.g. B. clay grains adjacent.

This additional layer can be attached to the outer layer as well be bound to the heat-insulating inner layer.

In this way, the invention makes it possible to create a burner block, through which a minimal amount of unused heat escapes and at which no flashback is possible. Furthermore, in the burner block according to the invention ensures that the flow rate of the combustible gases through the burner block therethrough, heating of these gases as operation progresses to a minimum Extent - it is set. Finally, when operating the burner block according to the invention on its front side no local areas higher and lower Temperature caused. but it is with large emission or emission of Overall, radiant heat ensures an even glow.

C C- The front surface of the outer layer can optionally have a thin coating of finely divided catalytic material in a manner known per se. The ceramic grains are preferably made of nfullite.

The invention is illustrated below with reference to the drawing, for example explained.

Fig. 1 is a sectional view of one embodiment of a brake on which the invention is embodied; F i g. 2 is one of the F i g. 1, similar sectional view of a modified embodiment of a burner block according to the invention.

In Fig. 1 , the ceramic part of a burner block is designated as a whole by 1 . The ceramic part 1 has an outer layer 2 which is formed from relatively coarse grains of silicon carbide, for example from silicon carbide with a grain size of about 0.5 to 2 mm, which is bonded in an appropriate manner. The ceramic part 1 also has an inner U insulating layer or barrier layer 3 made of insulating refractory ground clay chamotte, which is bound with a ceramic low-temperature binder in order to keep it in a rigid but permeable form, and which in turn is attached to the rear surface of the outer layer 2 is bound. The permeability of layer 3 is somewhat smaller than that of layer 2 in order to ensure that the flame does not migrate backwards from the exposed surface through the burner block and enter a gas chamber 10 .

According to the illustration, the burner block has a further, combustion-controlling layer 4 made of very fine-grained insulating material, which is adjacent to the chamber 10 in order to additionally ensure that the flame does not migrate back through the burner block into the chamber 10. The layer 4 is relatively thin and has, for example, a thickness of about 3.18 mm, since it is desirable not to restrict the gas flow any more and not to build up a back pressure that is greater than is necessary for safety. It is within the scope of the invention to select the grains of layer 3 so "that the speed of the gas flow through the pores in layer 3 is greater than the speed of the spread of flanges. So that the flame cannot migrate back through layer 3 In such a case, a special layer 4 can be omitted.

If necessary, a fine, flame-controlling layer 4 'similar to layer 4 can be built into the burner block, as shown in FIG. 2, namely between layers 2' and 3 '. It may also each one of such layers between the Schichten2 'and 3' and be provided at the gas inlet face of the layer 3 '.

The burner block t has grooves t1, which are machined into two or more of its side surfaces and tire into the flanges 7 of the side walls of the burner housing 6 , which is formed from appropriate metal 2. In order to create a tight fit to prevent the escape of gas, a cushion 9 made of felt-like asbestos or of fireproof wool is provided around the sides of the burner block.

A premixed combustible mixture. For example, natural gas and air is introduced into the gas chamber 10 of the housing 6 through an A 1 aßrohr 8 therethrough. Instead, the gas and air can be introduced overall cut and mixed in the chamber 10th They flow out of the chamber 10 through the pores of the burner block to the front of the layer 2, where they are ignited and burn. Some of the combustion goes back into the pores of the layer 2 when it heats up, whereby the temperature of the layer 2 increases and a rapid emission of heat is caused. However, the pores of the layer 3 are so fine that the velocity of the gas through them is great enough to prevent the flame from moving back into the layer 3 , and the pores of the layer 4 are very fine as described above, so that migration of the flame back through the layer 4 is completely avoided.

In order to ensure that the combustion of the exposed surface of the layer 2 takes place as close as possible, this surface can be coated with some finely divided catalytic material 5 , for example with cerium oxide with a particle size corresponding to a mesh size of 0.147 mm, which is obtained by spraying flames or dusted with a temporarily binding material or applied in the form of a dust and burned on either with the burner block or later. The effect of this material is to cause the maximum flame temperature to be reached quickly in close contact with the surface of the burner block.

When producing the burner block, it is preferably not made thicker than about 63.5 mm, divided into a thickness of about 3.18 to 12.7 mm made of coarse-grain silicon carbide with a grain size corresponding to a mesh size of, for example, 0.584 to 1.97 mm in layer 2. For layer 3 , ground refractory bricks or mullite are used in a grain size corresponding to a mesh size of about 0.584 to 0.1 mm, layer 3 being made about 38.1 mm thick, and layer 4 being used Similar ground material, as used for the layer 3 , with a grain size corresponding to a clear mesh size of about 0.176 to 0.71 mm and with a thickness of about 3.18 mm.

The following working sticks are described as an example of a preferred production: 1. 90 parts by weight of silicon carbide with a grain size corresponding to a mesh size of about 0.584 to 1.97 mm, 10 parts by weight of silicon carbide with a grain size corresponding to a mesh size of about 0.074 mm, 3 parts by weight of dextrin. are mixed together and a layer of this mixture with a thickness of 6.35 mm is placed in a mold in which the molding is to be formed.

2. 90 weight points of mullite of the same size as a grain corresponding to a mesh size of 0.584 to 0.71 mm. 10 parts by weight of slurried clay, 3 parts by weight of dextrin are mixed together, and a layer 3K 1 mm thick made of this material is applied to the top of the silicon carbide layer already in the mold.

Finally, if a third barrier layer is desired, 88 parts by weight of mullite with a grain size corresponding to a mesh size tD of 0.176 to 0.71 mm, 12 parts by weight of slurry clay and 3 parts by weight of dextrin are mixed together in a similar manner, and it is about 3.18 mm thick Layer of this material placed in the mold on the bust of the previous layers. Then the various layers or layers are pressed together under a pressure of about 70 kg per cm 2, the pressed piece is removed from the mold and baked for 4 hours at about 1260 ° C. in order to bring about the bond. The fitting is then ready to be inserted into the housing 6.

If desired, the compositions, the grain sizes, the Binder and the firing method used can be changed as desired, such as this in the Kerarnischen technology is known. It is important to maintain high strength and that the materials are chosen to match so that rapid Changes in temperature do not damage the block. It has generally been found that Silicon carbide forms an excellent hot surface and that the backing layer Mullite, like ground, baked clay. Alumina or other masses can be formed, which have a lower thermal conductivity than silicon carbide.

The burner assembly can then be hung from an outside wall using mechanical supports attached to the housing 6 , or it can be framed alone or in groups in any desired manner.

In operation, it is preferred to reach a temperature of 982 to 10931 C on the hot surface so that the heated surface radiates heat very quickly. With properly adjusted gas and air pressures, it has been found that these temperatures can be maintained, the temperature not exceeding 204 ° C. on the entire rear surface. The gas flow through such devices tends to tend to decrease as the temperature increases. This is partly the case with a burner according to the invention, but this change is far less when the fine control layer is present than when the layer is omitted.

It has been found that the hot surface of the burner over the entire surface has a substantially uniform temperature, the silicon carbide serves to transfer heat from a particularly hot point to its surrounding area to transfer laterally.

When the speed of the flammable gases is at such a value - it is held that a complete combustion is made impossible. while the gases are in contact with the refractory material remains a considerable one. Amount of heat still released in the gases after they hit the burner block have left. In such a case it is desirable to use a heat-resistant mesh Wire 12, for example made of nickel or a nickel alloy, in front of the silicon carbide surface to arrange. This wire or this sieve pulls a lot much of that Residual heat from the gases and emits it as radiation either directly to the desired Area from or redirects them to the silicon carbide, from which they are to the area to be heated is radiated. This network can be in any geel desired Wise are attached to the ceramic body, for example by the fact that the body is grooved at its edges, and the edges of the net can be so be bent so that they extend into this groove.

Claims (4)

Claims: 1. Ceramic burner block for gas radiant burner with several different layers lying one behind the other in the gas passage direction, of which the outer layer acts as a radiation layer and the inner one acts as a kickback protection, characterized in that the outer layer (2) consists of a bound pile of silicon carbide grains and the inner one Layer (3) consists of a bound pile of grains of heat-insulating material, e.g. clay grains, the grain size of the outer layer being coarser than that of the inner layer and the gas permeability of the two layers being matched to the properties and conditions of the fuel, that the gas passage speed in the outer layer (2) is lower and in the inner layer (3) higher than the ignition speed of the gas. 2. Burner block according to claim 1, characterized in that the inner layer (3) is thicker than the outer layer (2). 3, burner block according to claim 1 or 2, characterized in that on the inner layer (3) at least one additional thinner layer (4 or 4 ') of an even finer-grain pile of bound grains of heat-insulating material, e.g. B. Grains of clay, adjoins. 4. Burner block according to claim 3, characterized in that the additional thinner layer (4, 4 ') is bonded either to the outer layer (2) or to the heat-insulating layer (3, X).