EP2283277B1 - Burner - Google Patents

Description

The present invention relates to a burner used in particular in industrial furnaces, such as rotary kilns for cement, lime, alumina, oxides, minerals, etc.

There are many types of burner used in furnaces, having several parallel (or coaxial) axis lines including a first external air supply line located outside of all other burner lines, a central line of an air supply within which at least one central fuel supply pipe, at least one peripheral fuel supply pipe disposed around the central air supply pipe, and a second outer pipe are disposed air supply disposed around the peripheral fuel supply line. The document EP1862735 A1 discloses all the features of the preamble of claim 1.

The present invention aims to achieve a new type of burner performance and particularly easy to adjust. The object of the present invention is to solve by the features of claim 1.

The present configuration makes it possible to have a burner having a simple, easily adjustable configuration (the overall air flow resulting from the air leaving the two external ducts can be modified by the simple relative axial displacement of the two tubes delimiting the second pipe external) and able to operate with a high proportion of poor fuels (the axial air flow being formed by a series of single unit flows allowing to suck up a greater proportion of the secondary air coming from the furnace hearth).

• La figure 1 est une vue en coupe partielle longitudinale d'un bruleur conforme à un premier mode de réalisation de la présente invention ;
• La figure 2 est une vue similaire à la figure 1 d'un brûleur conforme à un second mode de réalisation de la présente invention ;
• La figure 3 est une vue similaire aux figures 1 et 2 d'un brûleur conforme à un troisième mode de réalisation de la présente invention ; et
• La figure 4 est une vue en coupe partielle longitudinale d'un stabilisateur de flamme du brûleur selon le second mode de réalisation.

Other features and advantages of the present invention will appear in the three embodiments given by way of non-limiting example and illustrated by the appended drawings in which:

• The figure 1 is a longitudinal sectional view of a burner according to a first embodiment of the present invention;
• The figure 2 is a view similar to the figure 1 a burner according to a second embodiment of the present invention;
• The figure 3 is a view similar to Figures 1 and 2 a burner according to a third embodiment of the present invention; and
• The figure 4 is a longitudinal partial sectional view of a burner flame stabilizer according to the second embodiment.

A burner 1 of rotary kilns as illustrated in FIG. Figures 1 to 4 comprises several lines 2, 4, 5, 6, 7 coaxial. These pipes comprise a central air supply pipe 2 which is associated with a flame stabilizer 3 which is disposed at the outlet of this pipe 2. The stabilizer 3 is in the form of a disc which may comprise, to ensure its cooling and its scan, several axial cylindrical or several radial slots tangential to the disk.

These conduits also include at least one (a 4 in Figures 1 and 2 ; two coaxial 4a, 4b in the figure 3 ) central fuel supply pipe 4 which is disposed inside the central air supply pipe 2 (here, in the axis of the burner 1, but which could be off-axis) and which opens through the stabilizer flame 3 via an opening 65.

In the first two embodiments, these conduits comprise at least one (here, a) peripheral fuel supply pipe 5 which is disposed around the central air supply pipe 2 (around the flame stabilizer 3).

Finally, the pipes comprise a first external air supply duct 6 which is located outside (around) all the other ducts 2, 4, 5, 7 of the burner 1, and a second external supply duct 6. air 7 which is arranged outside

(around) the flame stabilizer 3. In the first two embodiments, the second external air supply pipe 7 which is disposed around the peripheral fuel supply pipe 5.

These two external ducts 6, 7 make it possible to introduce into the hearth between 3 and 20% of the stoichiometric combustion air (preferably between 5 and 15%, or better, between 7 and 12%).

The first outer pipe 6 is delimited by two tubes 8, 9 which are stationary relative to each other (an outer tube 8 and an inner tube 9). These two tubes 8, 9 carry at their downstream end, immovably, a first series of axial channels 10 (here, peripherally closed) each having an outlet opening 11 opening into the home. The outlet orifices 11 of the channels 10 of the first series are the only openings opening into the hearth located between the two tubes 8, 9 delimiting the first external pipe 6.

These channels 10 are adapted to impart a zero tangential component to the air moving therethrough. As a result, the air from this first line 6 has an axial flow which is formed by the series of axial single point streams.

In the present embodiments, the channels 10 of the first series are angularly distributed regularly so that each outlet orifice 11 is separated from the two orifices 11 which are adjacent to it by an angular gap whose value is between two (or even three ) and ten times the angular extent of the orifice 11. This separation makes it possible to have axial unit flows sufficiently spaced from each other to allow good suction of the secondary air present in the hearth around the tube 8, while having enough axial unit air flow. The outlet orifices 11 are shaped so that the speed of the outgoing air is between 150 and 350 m / s, and preferably between 180 and 250 m / s (or even between 200 and 250 m / s). , in operating mode.

In the present embodiments, the channels 10 of the first series are all identical. Here, each channel 10 of the first series has a convergent conical shape from upstream to downstream and has an outlet port 11 having a circular cross-section. Each channel 10 of the first series comprises a progressive reduction portion 12 (here of conical shape) which makes it possible to pass from the continuous annular space situated between the two tubes 8, 9 delimiting the first external conduit 6, upstream of the channels 10 of the first series, to the outlet port 11 of these channels. Preferably, the value of the average half-angle at the apex of the conical reduction portion 12 is about 30 °. In addition, each channel 10 of the first series comprises, between its outlet orifice 11 and the reduction portion 12, a conical portion of acceleration 13 which makes it possible to have axial unit air flows resulting in less return of air near the front of the burner 1 and to avoid any air separation from the circular perimeter of the orifice output 11, which would cause a micro-wave ring. This therefore reduces the risk of deposition of dust around the outlet ports 11 which could cause their obstruction more or less important. Preferably, the value of the half-angle at the apex of the conical acceleration portion 13 is between 3 ° and 12 ° (preferably close to 7 °).

The second outer pipe 7 is delimited by two tubes 9, 14 which are axially movable relative to each other (an outer tube 9 and an inner tube 14). In this case, the two external ducts 6, 7 are separated from each other only by a common tube 9 which is the tube internally delimiting the first external duct 6 and externally the second external duct 7.

The tube 14 internally defining the second external pipe 7 carries, at its downstream end, immovably, a second series of channels 15 open towards the tube 9 externally defining the second outer pipe 7, each channel 15 having an outlet 16 coming into the home.

These channels 15 are adapted to impart a variable tangential component to the air moving therethrough. To this end, each channel 15 of the second series has, relative to the axis of the burner 1, a tangential deflection which decreases from its upstream end to its downstream end.

Furthermore, the tube 9 externally defining the second external pipe 7 (here, the middle tube 9) is shaped so that it comprises a cylindrical covering portion 17 which covers the open channels of the second series on a plus or minus long, according to the relative axial position of the two tubes 9, 14 delimiting the second outer pipe 7. In the present embodiments, the covering portion 17 is in the immediate vicinity of the channels 15 of the second series so that the almost all the air leaving the second external pipe 7 passes through these channels 15, a very small proportion coming out of the gap between the two tubes 9, 14 (gap allowing a necessary clearance between the two tubes 9, 14 allowing them relative axial displacement without friction). As a result, almost all of the air circulating in the external ducts 6, 7 comes out of the two series of channels 10, 15.

More specifically, in both embodiments, a sealing device 30 (in this case, a metal O-ring 30) is located between the two tubes 9, 14 delimiting the second outer pipe 7 so that the entire air flowing in this pipe 7 comes out only through the channels 15 of the second series. Here, the sealing device 30 is disposed in an annular groove formed in the covering portion 17.

The tube 9 externally defining the second external pipe 7 also comprises, in the downstream extension of the cylindrical covering portion 17, a driving portion 18 which is radially divergent from its upstream end (which is the downstream end of the lap portion 17) at its downstream end. As a result, the angle of tangential deflection of the air at the downstream end of the second external pipe 7 depends on the relative axial position of the driving portion 18 with respect to the channels 15 of the second series of which the Tangential deflection angle varies from their upstream end to their downstream end. The axial position of the downstream end of the cover portion 17 (and the upstream end of the drive portion 18) defines the output cross section 16a of the channels 15 of the second series.

In the first two embodiments and in the latter, the driving portion 18 is tapered fixed angle and its average half-angle at the vertex is at most equal to 30 °, and preferably at most equal to 20 °.

Moreover, in order to limit the presence of eddies that may cause abrasion of the burner 1, the distance separating, edge to edge, two channels 15 of the second series, measured on the circumference of their periphery, is at most equal to 6 mm. As a result, the overall flow of air leaving the second external pipe 7 remains essentially continuous, which avoids having suction of the dusty ambient air at the outlet of these channels 15 which would create surrounding counter-currents causing abrasions. burner metal 1.

In the present embodiments, for the same purpose of limiting the abrasion of the burner 1, regardless of the relative position of the two tubes 9, 14 delimiting the second external pipe 7, the output cross sections 16a of the channels 15 of the second series are upstream of the outlets 11 of the channels of the first series 10.

In addition, in the first example, the two external pipes 7, 8 are supplied with air in common. For this purpose, the upstream end of the adjacent tube 9 is located downstream of the upstream end of each of the other two tubes 8, 14 delimiting the two external ducts 6, 7 so that they delimit a single upstream pipe 20 power.

In contrast, in the second embodiment, the intermediate tube 9 extends upstream like the other two tubes 8, 14 delimiting the two outer conduits 6, 7. As a result, each external pipe 6, 7 is fed in air independently of one another, which allows for separate pressures for these two lines 6, 7.

In this embodiment, the adjoining tube 9 is formed by a downstream structure 31 (a tube) which carries the channels 10 of the first series, and by an upstream structure 32 (a tube) extending and covering the downstream structure 31. The upstream structure 32 extends upstream substantially to the upstream end of the other two tubes 8, 14 which delimit the two outer conduits 6, 7. The overlap of the two structure 31, 32 allows to compensate for expansion by their relative axial displacement. Moreover, in order to ensure the seal between the two external conduits 6, 7, the adjacent tube 9 also comprises a sealing device 33 (here, a metal O-ring 33) located between the two structures 31, 32. Here, the sealing device 33 is disposed in an annular groove formed in the upstream structure 32.

According to the invention, in order to have a cooling of the downstream end of the first external pipe 6 at the interstices between channels 10 of the first series, the burner 1 comprises a deflector 21 which forms a baffle. This baffle makes it possible, by partly masking the direct entry of air into the portion 12 of the channels 10, to circulate a portion of the air flowing in the first external duct 6 along the annular wall 23 in which are made the inlet ports of the channels 10 of the first series. In these embodiments, the deflector 21 is stationary relative to the annular wall 23. In these embodiments, the deflector 21 is formed by a series of obstruction walls 21 which are arranged upstream, at a distance and in front of each other. channels 10 of the first series.

Moreover, as illustrated in figure 3 , the flame stabilizer 3 is slidably mounted axially relative to a peripheral tube 50 which delimit externally the central air supply pipe 2. The inner downstream end 51 of this peripheral tube 50 and the peripheral rim 52 of the flame stabilizer 3 delimit an annular passage 60. In the present embodiment, to allow a modification the air flow passing through the annular passage 60, at least one of these two surfaces 51, 52 defining it is tapered (here, it is the inner downstream end 51 of the peripheral tube 50). In addition, in this example, at least one of the two surfaces 51, 52 delimiting the annular passage 60 has deflection members (in this case, inclined grooves) conferring a tangential component to the fluid passing through the annular passage 60 (here, it is the peripheral rim 52 of the flame stabilizer 3). Preferably, the angle of inclination of the grooves is between 5 and 60 ° with respect to the axis of the burner 1. Finally, in order to allow the axial displacement of the flame stabilizer 3 easily, the central tube 55 defining the pipe fuel supply station 4 is axially integral with the flame stabilizer 3.

Other embodiments are possible.

In order to limit the abrasion of the burner, it is possible that, whatever the relative position of the two tubes delimiting the second external pipe, the outlet orifices 16 of the channels of the second series are upstream of the outlet orifices of the channels of the first series.

It would thus be possible for the distribution of the outlet orifices 11 of the channels of the first series to have a somewhat modified regularity, these orifices thus being able to be grouped by two or three. This particular arrangement is of aerodynamic interest to further favor the good aspiration of the secondary air present in the hearth around the tube 8, while reducing the maximum distance between the two orifices furthest away, and, therefore, by reducing the risk of dust deposits on the downstream wall burner. In these cases, the angular gap separating two adjacent outlet orifices belonging to two different groups is between two (or even one and a half times in the case of a group of three orifices) and ten times the angular extent of the orifice. The gap separating two adjacent outlets belonging to the same group is at most equal to the angular extent of the orifice.

It would also be possible for the two outer pipes to be separated from each other by an external fuel supply line (generally, gas).

It would also be possible alternatively or cumulatively with the central fuel supply pipe 4, a central pipe receiving an ignition burner is disposed in the central air supply pipe 2.

It would also be possible for the tube externally delimiting the second external duct to comprise, in the downstream extension of the driving portion 18, a cylindrical rectifying portion whose upstream end would form the downstream end of the driving portion 18. and whose downstream end would form the downstream end of the tube. This cylindrical portion makes it possible to attenuate the diverging radial component of the air flow at the outlet of the second external duct and thus to limit the premature mixtures between the two air flows coming from the two external ducts.

It would also be possible for the driving portion 18 to have a progressive divergence, the half-angle at the summit increasing from upstream to downstream. Thus this half-angle could be less than 12 ° at its upstream end and increase gradually without exceeding, at its downstream end, 25 °.

Claims (14)

1. A burner (1) comprising several pipes (2, 4, 5, 6, 7) of parallel axes wherein:

   a central air supply pipe (2) on the outlet of which is arranged a flame stabilizer (3) and within which is arranged at least one central fuel supply pipe (4) and/or a central pipe receiving an ignition burner opening through the stabilizer (3) via an opening (65),

   a first external air supply pipe (6) located outside all the other pipes (2, 4, 5, 7) of the burner (1), delimited by two tubes (8, 9) which are immovable with respect to each other and which immovably bear at their downstream end, a first series of axial ducts (10) that are adapted to confer a null tangential component to air moving therein, and

   a second external air supply pipe (7) arranged outside the flame stabilizer (3), delimited by two tubes (9, 14) which are axially mobile with respect to each other, the tube (14) which internally delimits the second external pipe (7) immovably bearing, at its downstream end, a second series of open ducts (15) that are adapted to confer a variable tangential component to air moving therein, each duct (15) of the second series exhibiting, with respect to the burner (1) axis, a tangential deflection that decreases from its upstream end towards its downstream end, the tube (9) externally delimiting the second external pipe (7) comprising a drive portion (18) radially diverging from upstream to downstream such that the tangential deflection angle of air at the downstream end of the second external pipe (7) depends on the relative axial position of the drive portion (18) with respect to the ducts (15) of the second series, all air circulating in the external pipes (6, 7) when exiting from the two series of ducts (10, 15), characterized in that it comprises a series of obstruction walls (21) arranged upstream, at a distance and facing the ducts (10) of the first series, forming baffles adapted to cause part of the air circulating in the first external pipe (6) to circulate along the annular wall (23) in which the inlet orifices of the ducts (10) of the first series are made.
2. The burner (1) according to claim 1, characterized in that, the edge to edge distance separating two ducts (15) of the second series taken on the circumference of their periphery is at the most equal to 6 mm.
3. The burner (1) according to claim 1 or 2, characterized in that, the mean half-angle at the apex of the drive portion (18) is at the most of 30°, and preferably at the most of 20°.
4. The burner (1) according to any one of claims 1 to 3, characterized in that, the half-angle at the apex of the drive portion (18) increases from upstream to downstream, and preferably, exhibits at its upstream end a half-angle less than 12° and at its downstream end a half-angle less than 25°.
5. The burner (1) according to any one of claims 1 to 4, characterized in that both external pipes (6, 7) are only separated from one another by an intermediate tube (9) formed by the tube (9) bearing the drive portion (18).
6. The burner (1) according to claim 5, characterized in that the upstream end of the intermediate tube (9) is located downstream from the upstream end of each of the two other tubes (8, 14) delimiting both external pipes (6, 7) such that these delimit a unique upstream supply pipe (20) of both external pipes (6, 7).
7. The burner (1) according to any one of claims 1 to 6, characterized in that a sealing device (30) is located between both tubes (9, 14) delimiting the second external pipe (7) such that all air circulating in this pipe (7) exits from the ducts (15) of the second series.
8. The burner (1) according to claim 7, characterized in that the sealing device (30) is formed by a metallic O-ring (30) .
9. The burner (1) according to claim 5, characterized in that the intermediate tube (9) extends such that each external pipe (6, 7) may be supplied with air independently from one another.
10. The burner (1) according to claim 9, characterized in that the intermediate tube (9) comprises a compensation device making it possible to compensate for expansions.
11. The burner (1) according to claim 10, characterized in that the intermediate tube (9) comprises a downstream structure bearing the ducts (10) of the first series, and an upstream structure extending and overlapping the downstream structure and extending upstream substantially to the end of the two other tubes (8, 14) delimiting the two external pipes (6, 7), such as to compensate for the expansions by the relative axial movement of both structures of the intermediate tube (9).
12. The burner (1) according to claim 11, characterized in that the intermediate tube (9) comprises a sealing device located between the two structures forming the intermediate tube (9) ensuring the sealing between the two external pipes (6, 7).
13. The burner (1) according to claim 12, characterized in that the sealing device is formed by a metallic O-ring.
14. The burner (1) according to any one of claims 1 to 13, characterized in that the cross-section of the ducts (15) of the first series is constant in the plane perpendicular to the fluid flow in each of these ducts (15).

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