EP0919769B1 - Device for protecting the injection tip of a burner and heating device comprising it - Google Patents

Description

The present invention relates to an output protection device ejection of a burner mounted through a wall of an oven, of the type comprising a peripheral heat shield and mounting means said heat shield around the burner ejection outlet.

The invention also relates to a heating device comprising a burner and a protection device of the aforementioned type. The invention relates more particularly to a burner according to the preamble of claim 1.

In some applications, such as in rotary ovens melting of cast iron, the burners used are subject to strong attacks due on the one hand to thermal radiation and on the other hand to attacks chemicals caused by bodies resulting from the melting of cast iron. In this type of oven, it is known to provide cooling means with water from the burner discharge end. These cooling means include a tubular protective member through which circulates cooling water. This tubular member is mounted axially at the end from the burner and protrudes inside the oven.

Such an arrangement is impractical since it requires the implementation costly and bulky equipment suitable for circulation water in the protective device. In addition, the presence of a circuit of water presents a risk of circuit breakage if the oven stops when the temperature is below 0 ° C.

EP-A-582 521 discloses a burner provided with a thermal screen made of refractory material.

The object of the invention is to propose a burner comprising a device for protecting the burner ejection outlet and a heating device comprising such a burner, do not not having the disadvantages mentioned above, and which allows get rid of the existence of a bulky water circuit and source of malfunctions.

To this end, the invention relates to a burner according to the preamble of claim 1 , characterized in that the screen thermal includes a consumable structure of refractory material having the shape of a sleeve whose position can be adjusted and which always exceeds the ejection end of the burner by a same distance.

• les moyens de montage sont disposés entre le brûleur et l'écran thermique, de sorte que l'écran thermique est porté par le brûleur ;
• le brûleur comporte une enveloppe renfermant des conduites d'acheminement du combustible et du comburant, laquelle enveloppe est tubulaire sur au moins une partie de sa longueur, et les moyens de déplacement comportent un organe de guidage emmanché sur la partie tubulaire de l'enveloppe, afin d'assurer le coulissement de l'écran thermique sur l'enveloppe ;
• l'organe de guidage est muni de deux brides accouplées, enserrant un joint torique de serrage appliqué contre la surface extérieure de la partie tubulaire de l'enveloppe, ainsi que de moyens de serrage des deux brides l'une sur l'autre, afin de comprimer le joint torique assurant ainsi un maintien en position de l'écran thermique par rapport à l'enveloppe du brûleur ;
• le matériau réfractaire constituant ladite structure est un aluminosilicate comportant en masse x % de SiO₂ et y % de Al₂O₃ avec un rapport x/y compris entre un tiers et deux tiers et notamment voisin de un demi ;
• la somme x + y des pourcentages en masse de SiO₂ et de Al₂O₃ est supérieure à 90 % ; et
• ladite structure est un pisé ayant subi, avant montage, une étape de cuisson à une température supérieure à 1000°C.

According to particular embodiments, the burner has one or more of the following characteristics:

• the mounting means are arranged between the burner and the heat shield, so that the heat shield is carried by the burner;
• the burner comprises a casing containing fuel and oxidant transport pipes, which casing is tubular over at least part of its length, and the displacement means comprise a guide member fitted on the tubular part of the casing, to ensure the sliding of the heat shield on the envelope;
• the guide member is provided with two coupled flanges, enclosing a tightening O-ring applied against the external surface of the tubular part of the envelope, as well as means for tightening the two flanges one on the other, so compressing the O-ring thus ensuring that the heat shield is held in position relative to the burner casing;
• the refractory material constituting said structure is an aluminosilicate comprising by mass x% of SiO ₂ and y% of Al ₂ O ₃ with a ratio x / including between a third and two thirds and in particular close to a half;
• the sum x + y of the mass percentages of SiO ₂ and Al ₂ O ₃ is greater than 90%; and
• said structure is an adobe having undergone, before assembly, a cooking step at a temperature above 1000 ° C.

The invention further relates to a heating device comprising a burner associated with a protection device as defined above.

• la figure 1 est une vue schématique en coupe longitudinale d'un four rotatif de fusion de fonte muni d'un brûleur selon l'invention ;
• la figure 2 est une vue en coupe longitudinale d'un brûleur associé à un dispositif neuf de protection selon l'invention ; et
• la figure 3 est une vue en coupe longitudinale du brûleur de la figure 1 associé à un dispositif de protection selon l'invention ayant déjà subi une longue période de fonctionnement.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings in which:

• Figure 1 is a schematic longitudinal sectional view of a rotary smelting furnace provided with a burner according to the invention;
• Figure 2 is a longitudinal sectional view of a burner associated with a new protection device according to the invention; and
• Figure 3 is a longitudinal sectional view of the burner of Figure 1 associated with a protection device according to the invention having already undergone a long period of operation.

In Figure 1 is shown a rotary furnace 10 for melting cast iron provided with a burner according to the invention. The oven has an enclosure 12 with axis of horizontal revolution, noted X-X. The enclosure 12 is delimited in its part running through a cylindrical wall 14 comprising, at each end 16, frustoconical obturation walls. At one end 18, the oven has axially means 20 for introducing the metals to be melted. It comprises, at its other end, an outlet 22 for molten iron.

Along the axis X-X is arranged, opposite the end 18 of arrival materials to be melted, a burner 24 adapted to produce a flame 26 along the axis of the oven. The burner 24 is carried by a shutter door 28 of the oven articulated around a vertical Y-Y axis. The oven is supported in its running part by two crowns of rollers 30. It further comprises rotational drive means not shown.

The interior wall of the furnace is lined with a siliceous refractory lining 32 comprising approximately 95% by weight of SiO ₂ and 4% by weight of Al ₂ O ₃ , the remainder consisting of impurities.

The door-mounted burner is shown on a larger scale in Figures 2 and 3.

The door has an outer metal wall 34 lined internally of a refractory material 36 similar to the coating 32 used for the interior wall of the oven.

The burner comprises, in a conventional manner, an envelope or body 38, generally of revolution. This envelope is separated by a wall transverse 40 delimiting therein a fuel gas inlet chamber 42 arranged behind and an oxidizing gas inlet chamber 44. The latter leads to the front end of the body, directly inside of the oven through an opening 46. Each chamber 42, 44 is connected to a corresponding gas supply source, by a side connection, noted 42A and 44A respectively.

The fuel gas inlet chamber 42 communicates with three fuel injection rods 48. These rods pass through the wall 40 and are carried by it. They extend into the following envelope 38 the axis of the burner and protrude beyond the opening 46.

The burner casing 38 is fixedly connected to the plate 34 of the door by a support frame 50 shown schematically in the figures.

In addition, according to the invention, the burner is associated with a device 52 for protection of the burner injection outlet. This device 52 essentially comprises a heat shield 54 carried by mounting means 56 of it on the cylindrical running part denoted 38A of the envelope.

The heat shield 54 is formed of a tubular member or sleeve. Thus, it has an external cylindrical surface denoted 54A and a passage internal cylindrical 54B. The diameter of the latter is constant and is very slightly greater than the external diameter of the current portion 38A of the burner body. The burner ejection outlet where the ends open rods 48 and chamber 44 is received in passage 54B, the sleeve being partially engaged on the current part 38A of the body.

Thus, the sleeve passes through the lining 36 of the door through an opening cylindrical 36A. A skirt 57 for protecting the heat shield, formed of a tubular wall, extends the cylindrical opening 36A and projects outside the oven. The skirt 57 is integral with the wall 34.

Sleeve 54 projects inside the oven at one front end at a distance of 7 cm. Its rear end projects outside the oven beyond plate 34 of the door. This rear end is integral mounting means 56.

The sleeve 54 is formed by an adobe having undergone, before assembly with the mounting means 56, a cooking step prior to a temperature above 1000 ° C.

The refractory material constituting the sleeve 54 is an aluminosilicate advantageously comprising by mass x% of SiO ₂ and y% of Al ₂ O ₃ , the ratio x / y being between one third and two thirds and advantageously close to one half.

In addition, the sum x + y of the mass percentages of SiO ₂ and Al ₂ O ₃ is greater than 90%.

EXTRADOS : partie du manchon faisant saillie dans le four, hors face d'extrémité avant ;

INTRADOS : partie courante du manchon, notamment dans la zone arrière de celui-ci ;

CRASSE : face d'extrémité avant du manchon, c'est-à-dire la partie annulaire en cours de dégradation à l'avant du manchon.

ELEMENT RESULTATS EN % EXTRADOS INTRADOS CRASSE SiO₂ 47.20 47.38 30.43 Al₂O₃ 45.97 46.23 37.58 Fe₂O₃ total 1.49 1.47 28.33 P₂O₅ 2.50 2.18 1.19 TiO₂ 1.21 1.21 0.59 CaO 0.29 0.26 0.25 MgO 0.21 0.20 0.19 MnO 0.01 0.01 0.13 K₂O 0.61 0.60 0.28 Na₂O 0.11 0.10 0.06 ZnO --- --- 0.4 ZrO₂ --- --- 0.10 Perte au feu 0.18 0.16 0.47 : gain au feu TOTAL 99.78 99.80 99.53 PHASES MINERALOGIQUES Sillimanite Sillimanite Al₂O₃,SiO₂ Al₂O₃,SiO₂ Cristobalite SiO₂ Cristobalite SiO₂ Andalousite Andalousite Al₂O₃,SiO₂ Al₂O₃,SiO₂ Quartz SiO₂ (traces) Quartz SiO₂ (traces) The following table describes, by way of example, the composition of the sleeve 54 analyzed by an X-ray fluorescence method. The sleeve was analyzed after use in an oven. The composition was determined at three distinct points on the sleeve located as follows:

EXTRADOS: part of the sleeve protruding into the oven, outside the front end face;

INTRADOS: running part of the sleeve, in particular in the rear area thereof;

CRASSE: front end face of the sleeve, that is to say the annular part in the process of degradation at the front of the sleeve.

ELEMENT RESULTS IN% EXTRADOS soffit DIRT SiO ₂ 47.20 47.38 30.43 Al ₂ O ₃ 45.97 46.23 37.58 Fe ₂ O ₃ total 1.49 1.47 28.33 P ₂ O ₅ 2.50 2.18 1.19 TiO ₂ 1.21 1.21 0.59 CaO 0.29 0.26 0.25 MgO 0.21 0.20 0.19 MnO 0.01 0.01 0.13 K ₂ O 0.61 0.60 0.28 Na ₂ O 0.11 0.10 0.06 ZnO --- --- 0.4 ZrO ₂ --- --- 0.10 Fire loss 0.18 0.16 0.47: gain on fire TOTAL 99.78 99.80 99.53 MINERALOGICAL PHASES sillimanite sillimanite Al ₂ O ₃ , SiO ₂ Al ₂ O ₃ , SiO ₂ Cristobalite SiO ₂ Cristobalite SiO ₂ andalusite andalusite Al ₂ O ₃ , SiO ₂ Al ₂ O ₃ , SiO ₂ Quartz SiO ₂ (traces) Quartz SiO ₂ (traces)

In order to ensure good resistance of the sleeve 54 to the flame, as well good resistance to thermal shock, especially during phases shutdown and start-up of the oven, the sleeve is made in the manner next.

The materials in the form of aggregates constituting the structure of the sleeve are arranged in a cylindrical mold defining the shape of the sleeve to make an adobe.

To ensure correct sintering, tamping or clamping the adobe in the mold is made with care, in particular by adding successive layers 2 or 3 cm thick each packed with a pneumatic gland.

The cooking of the rammed earth is then carried out according to a standard profile of temperature rise specific to adobe to a temperature of 1350 ° C.

After cooking and demoulding, the rammed earth has the following characteristics: Basic constituent fireclay Average expansion between 0 and 1000 ° C 3.10 ⁶ Physical characteristics Density after heating to 1000 ° C 2.3 T / m ³ Conductivity coefficient in Kcal m ² h ° C to 600 ° C 0.7 800 ° C 0.7 1200 ° C 1 Resistance to cold compression after heating to 1100 ° C 350 Kg / cm ² Pyroscopic cone 36 Temperature limit for use 1500 ° C Slump under load of 2 bars 0.5% at 1200 ° C and 5% at 1340 ° C.

The mounting means 56 are adapted to ensure movement of the heat shield 54 relative to the wall of the oven enters at least two positions spaced along the axis of the burner. They include for this purpose a guide tube 58 with an inside diameter slightly greater than the diameter external of the current part 38A of the envelope. The tube 58 comprises, at its front end, a transverse annular plate 60 provided with holes fixing the screen 54. For this purpose, the latter comprises inking 62 the threaded ends of which are received through bores and held in place by nuts 64.

At its rear end, the tube 58 has an annular flange 66 drilled with a set of tapped holes. Against this flange is applied an additional flange 68 retained on the first flange 66 by screws 70 forming means for tightening the two flanges against each other according to the axis of the burner.

The flange 68 has at its internal diameter, on its face in contact with the first flange 66, a countersink 72 in which is received a clamping O-ring 74 whose diameter corresponds substantially to outside diameter of the current part 38A of the envelope. So the joint O-ring 74 is in contact with the lateral surface of the envelope.

It is understood that, when the clamping means 70 are released, the O-ring 74 not being compressed, the tube 58 is free to slide axially along the current part 38A of the envelope from a position retracted shown in Figure 2 to an advanced position shown in Figure 3. It carries with it the heat shield 54.

On the contrary, when the clamping means 70 hold the flange 68 against the flange 66, the seal 74 is compressed and exerts a friction force on the main part 38A of the envelope, ensuring that the position of the heat shield 54. Thus, as a function of the length of the sleeve 54, the position of the heat shield can be adjusted, so that the sleeve 54 protrudes from lining 36 over a length predetermined. Advantageously, this length is of the order of 7 cm.

When the sleeve 54 is new, as shown in FIG. 2, it has a great length, for example equal to 40 cm. So, the mounting means 56 are held behind and most of the length of the sleeve 54 extends behind the lining 36.

During burner operation, the annular end face of the sleeve contained inside the oven gradually degrades, in particular under the chemical action of iron and manganese oxide molecules produced by the slag resulting from molten iron.

With the composition and structure chosen for the refractory material constituting the sleeve 54, it can be seen that the erosion of the end front of the sleeve is carried out along a plane extending perpendicularly to the axis of it. So in order to keep constant the length of the part of the sleeve projecting from the lining 36, the user of the oven periodically advances the sleeve to compensate for the amount of material eroded at its end.

As shown in Figure 3, after a certain period of operation, mounting means 56 are almost completely received inside the skirt 57 and the remaining length of the sleeve is reduced to the thickness of the lining 36 and the length projecting from this inside the oven.

It is understood that with such a device, the end of the burner is permanently properly protected, the heat shield always protruding beyond the end the same distance from the burner.

Although the material constituting the sleeve 54 undergoes erosion, this is slow enough to allow periodic adjustment of the position of the heat shield is sufficient to avoid degradation of the end of the burner.

Finally, the low cost of the sleeve allows it to be replaced several times during the life of the oven without significantly increasing the cost operating it.

Claims (9)

1. Burner comprising a jacket (38) containing pipes (34, 48) conveying the fuel and the oxidizing agent and equipped at its ejection outlet with a protective device of the heat shield type, characterized in that the heat shield (54) has a consumable structure made of refractory material in the form of a sleeve (54) the position of which can be adjusted so that it always protrudes by the same amount beyond the ejection end of the burner.
2. Burner according to Claim 1, characterized in that it comprises means of moving the heat shield (54).
3. Burner according to Claim 1 or 2, characterized in that it comprises mounting means (56) arranged between the body of the burner (24) and the heat shield (34), such that the heat shield is borne by the burner (24).
4. Burner according to either of Claims 2 and 3, characterized in that the jacket (38) is tubular over at least part of its length, and in that the movement means comprise a guide member (58) pushed over the tubular part (38A) of the jacket, so as to allow the heat shield (54) to slide along the jacket (38).
5. Burner according to Claim 4, characterized in that the guide member (58) is equipped with two coupled flanges (66, 68) trapping a gripping O-ring (74) pressed against the exterior surface of the tubular part (38A) of the jacket (38), and means (70) of clamping the two flanges together so as to compress the O-ring (74), thus keeping the heat shield (54) in position relative to the jacket (38) of the burner.
6. Burner according to any one of the preceding claims, characterized in that the refractory material of which the said structure is made is an aluminosilicate containing, by mass, x% of SiO₂ and y% of Al₂O₃ with an x/y ratio of between one third and two thirds and, in particular, close to one half.
7. Burner according to Claim 6, characterized in that the sum x + y of the percentages by mass of SiO₂ and Al₂O₃ exceeds 90%.
8. Burner according to Claim 6 or 7, characterized in that the said structure is a ramming mass which, prior to mounting, has been baked at a temperature in excess of 1000°C.
9. Heating device comprising a burner (24) according to any one of the preceding claims, designed to be mounted through the wall (28) of a furnace.

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