EP3177872B1 - Burner with adjustable air or gas injection - Google Patents

Description

The present invention relates to the field of burners of any field and of any fuel, and in particular but not limited to burners for rotary kilns (or rotary kilns), such as cement kilns or lime kilns.

In most rotary kiln installations, the majority of combustion air generally called secondary air arrives at very high temperature (between 600 to 1200 ° C) and low speed (between 4 and 10m / s), after being used as cooling air for hot material falling from the oven.

In a cement kiln, this hot secondary air represents between 80 and 95% of the combustion air in the kiln.

Complementary air, called primary air, is the air injected directly into the burner at a lower temperature (temperature close to ambient temperature in most cases) but at high speed.

• Le refroidissement et la tenue mécanique du brûleur de four
• L'activation de la combustion et la maitrise de la forme de flamme. Pour ce faire, cet air primaire est injecté à l'extrémité du brûleur, à haute pression (entre 100 et 500 mbar) et à haute vitesse (entre 80 et 350 m/s) dans le but :
  • ∘ D'aspirer l'air secondaire chaud au cœur de la flamme et assurer son mélange rapide avec le combustible du brûleur et activer ainsi la combustion.
  • ∘ De contrôler par ses composantes axiales et radiales la forme de flamme tel que sa largeur et sa longueur, et de s'adapter aux conditions spécifiques du four.

It generally represents between 5% and 20% of the combustion air and has two functions:

• Cooling and mechanical resistance of the oven burner
• Activation of combustion and control of the flame form. To do this, this primary air is injected at the end of the burner, at high pressure (between 100 and 500 mbar) and at high speed (between 80 and 350 m / s) in order to:
  • ∘ Draw the hot secondary air into the heart of the flame and ensure its rapid mixing with the fuel from the burner and thus activate combustion.
  • ∘ Control by its axial and radial components the shape of the flame such as its width and length, and adapt to the specific conditions of the oven.

Rotary oven burners are generally characterized by their primary air pulse which is the force generated by the expansion of the air primary in the furnace (primary air mass flow x primary air expansion speed) divided by the calorific power of the burner.

The primary air at high pressure and low temperature impacts the energy balance of the process by the electrical consumption necessary for its pressurization as well as by the introduction of cold air into the process.

• la détente de cet air primaire soit réalisée à la toute extrémité de l'embout pour bénéficier pleinement de la vitesse de détente
• la pression avant l'extrémité du brûleur ne doit pas être affectée par des organes de réglage ou perte de charge afin d'obtenir la vitesse de détente maximale à l'extrémité.

To minimize this impulse and optimize its use, it is important to have a maximum speed of expansion of this primary air for the suction of secondary air. Therefore, it is recommended that:

• the expansion of this primary air is carried out at the very end of the nozzle to take full advantage of the expansion speed
• the pressure before the end of the burner must not be affected by regulating devices or pressure drop in order to obtain the maximum expansion speed at the end.

The primary air injections at the end of the rotary oven burners generally consist of at least two primary air outlets, at least one of which is axial and the other radial (or rotational), as in the patent FR 2 780 489 and FR 2 901 852 . In this case, the adjustment of the proportion between the flow and / or the axial and radial air pressure allows the adjustment of the overall radial component of the primary air and varies the flame shape.

These burners are therefore generally equipped with devices for adjusting the axial and / or radial pressure which reduces the pressure and consequently the expansion speed of these airs at the end of the burner. They thereby reduce the burner pulse which is proportional to the expansion speed. To compensate for the pressure loss due to the adjustment and maintain the pulse of the burner which is used to obtain a combustion result or equivalent process operation, it is therefore necessary to increase the primary air flow or pressure. For many of these burners, the injection of pulverized fuel (coal, petcoke, etc., which are the main fuels in the rotary kiln) is sandwiched between the primary external axial air and the internal radial air. Therefore, at primary air pulse, this radial outlet does not fully participate in the absorption of secondary air in the flame. It will therefore take more primary air impulse to achieve an equivalent result.

In addition, the arrangement of the radial air inside the pulverized fuel circuit increases the risk of fuel being ejected from the flame, which can create unfavorable operating conditions (deterioration of the cooking quality of the product , operational difficulties, reduction in the life of the brickwork lining the furnace, etc.) and increases NOx emissions, because the fuel concentration is too low at the center of the flame, which prevents the phenomenon of NOx-reducing re-combustion. .

• soit la composante radiale est obtenue par un mélange axial / radial en amont et l'on retrouve la même problématique que sur les brûleurs à deux sorties d'air primaire, à savoir une perte d'efficacité liée à l'usage d'organe réglant créant des pertes de charges et faisant baisser la vitesse de détente de l'air primaire,
• soit la composante radiale est obtenue par orientation des sections de sortie du brûleur. Il faut que cette orientation soit faite sans perte de charge particulière pour que le brûleur bénéficie d'une vitesse de détente de l'air primaire à l'embout optimale, et d'une meilleure efficacité énergétique.

The primary air injections at the end of the rotary oven burners can also have a single primary air outlet with adjustable radial component. In that case:

• either the radial component is obtained by an axial / radial mixture upstream and we find the same problem as with burners with two primary air outlets, namely a loss of efficiency linked to the use of regulating member creating pressure drops and lowering the expansion speed of the primary air,
• either the radial component is obtained by orientation of the burner outlet sections. This orientation must be done without any particular pressure drop so that the burner benefits from an optimal primary air expansion speed at the nozzle, and better energy efficiency.

Controlling the flame diameter is more difficult in burners with a single primary air outlet with adjustable radial component. Indeed, if in burners with two or more outlets, the axial outlet is generally located at the periphery of the burner to control and stabilize the divergence of the flow and allow a more efficient and finer adjustment of the flame diameter, this advantage does not exist on single outlet burners, making it more difficult to adjust the diameter. Too large a flame diameter which can have serious consequences on the conditions of operation of the process (affecting the nature of the material to be cooked and / or the operating conditions) and or the lifetime of the refractory linings of the oven.

For burners used in fields other than that of rotary ovens, part of the combustion air can also be rotated to ensure turbulence and a better mixture of air and fuel. The present invention also applies to these burners, whether the air is called primary air, combustion air or radial air or rotational air, or staged air.

In the following description, this portion of combustion air will be referred to as primary air.

In many burners, including rotary kiln burners, the problem described above for air also applies to gaseous fuels such as natural gas, industrial process gas (refinery, steel industry, etc.) of which it is important. to adjust the radial outlet angle as well as its speed.

The object of the present invention is to provide a burner which makes it possible to gradually and linearly adjust the radial component of the primary air or of the gas and to avoid adjustment by reducing the pressure (and therefore the expansion speed). ) of a radial or axial component and therefore of retaining the maximum pulse of the primary air or of the gas.

The burner according to the invention comprises a primary air or gas pipe of axis X delimited by an outer wall and a concentric inner wall and pipes for injecting primary air or radial gas, it is characterized in that that the primary air or gas duct comprises a ring movable in rotation and having axial protrusions constituting distributors which cooperate with the primary air or radial gas injection ducts disposed at the end of the burner on the part outer peripheral of the inner wall and form two channels of different angles in each primary air or gas injection duct radial. The rotation of the crown will allow the section of the primary air or radial gas ducts to be divided into two series of interposed channels.

Advantageously, the crown is also movable in translation. The translation of the crown will make it possible to modify the passage section of the primary air or radial gas injection conduits. Indeed, the passage section is the sum of the sections of the conduits constituting the primary air or gas conduit, and it is smaller than the outlet section, the passage section is therefore adjustable.

A first series of channels has a small radial primary air injection angle (generally between -10 and + 30 °) while the other series has a greater radial primary air injection angle than the previous series (generally between +10 and + 60 °).

The injection angle of the radial primary air or of the resulting gas is the combination of the air jets from the two series of interleaved channels, one at a small angle and the other at a large angle.

The rotation adjustment of the crown around the X axis makes it possible to vary the section distribution, and therefore the flow of primary air or gas between these two series of intercalated channels and therefore to adjust the injection angle. radial air.

This cross-sectional distribution between the two series of interleaved channels is carried out at constant total cross-section, which greatly simplifies the adjustment of the burner.

In addition, the adjustment is located just at the end of the burner, at the level of the exit of the primary air or the gas in the furnace, by this position of the adjustment at the end one maximizes the exit speed of the air or gas and therefore the pulse.

It also avoids the rotation of moving parts in direct contact with the outside of the burner which are subjected to very high thermal stresses. This minimizes the risk of damage to these parts.

Advantageously, the two channels are formed by a flared shape complementary to the distributor and the primary radial air ducts and the sum of the sections of said channels is constant in a plane perpendicular to X, whatever the angular position of the crown (3). The distributors and the primary air or radial gas injection conduits are of complementary flared shape which form channels of constant section. Thus the adjustment is made by modifying the outlet angle of the radial component with a constant outlet section which greatly simplifies the adjustment of the burner.

Advantageously, the distributors and the primary air or radial gas injection conduits have walls with parallel edges.

Advantageously, the distributors and the primary air or radial gas injection conduits have curvilinear edges. This form makes it possible to limit the pressure drops.

Advantageously, the movable crown has at least one inclined groove and it is actuated in rotation by a movable ring in translation to which it is connected by a nut sliding in said groove. The translation of the ring thus allows the rotation of the crown.

According to a particular arrangement, the movable ring is actuated by a jack. The cylinder can be hydraulic, or mechanical, or pneumatic.

Advantageously, the radial primary air ducts and the distributors are chamfered upstream. The chamfer is in a tangent plane or in a vertical plane relative to the air flow, and it allows a progressive entry and acceleration of the air in the channels and therefore a limited pressure drop.

Advantageously, the burner also includes axial primary air ducts.

According to a particular arrangement, the primary air or radial gas injection pipe is sandwiched between the fuel pipes and the axial primary air pipe.

Advantageously, the axial primary air and radial primary air injection conduits are supplied by the same supply. This is very advantageous, especially in the case of a burner with two primary air outlets (one axial and the other radial), located outside the fuel circuits as this makes it possible to lighten the burner and limit the pressure losses in the supply circuits, to have a burner whose settings are simple. We can thus adjust the rotation of the crown to increase the radial component and act on the flame diameter and adjust the air pressure upstream of the burner to adjust the pulse. This makes it possible to limit the maximum rotation by a constant proportion between the external axial circuit and the internal circuit with adjustable radial component and to limit the maximum flame diameter and thus protect the refractories of the ovens from false operations and / or incorrect adjustment.

Advantageously, the number of primary air or radial gas injection ducts is a multiple of the number of axial primary air duct or of a group of axial primary air ducts.

Advantageously, the primary air or radial gas injection conduits and the axial primary air conduits are arranged on the same radii. The number of outlet ports in the radial air circuit, or with a tangential component, can be matched with the number of holes (or group of holes) in the axial air circuit, so that the primary air pulse from the two circuits best contributes to the absorption of secondary air. In this perspective, the angular location of the axial and radial air orifices is important and the arrangement with the axial and radial orifices (or group of orifices) on the same radius is advantageous, that is to say that the radial air or gas injection ducts are located radially directly below the axial air injection ducts.

Advantageously, the inclination and the length of the groove is proportional to the rotation of the crown. The groove may have a length of 50 to 300mm and a slight inclination of 1 to 15 ° relative to the X axis. The combination of a long groove and a small angle makes it possible to obtain high adjustment precision.

According to a particular arrangement, the duct has an outlet section, this outlet section varies according to the movement of a wall relative to the other, the inner radial face of the distributors and the outer radial face of the notches make an angle α with the axis X and the inner radial face of the outer ring makes an angle β with the axis X. In certain applications and advantageously, the primary radial air or gas circuit, the outlet section can be adjusted to maintain a pressure and therefore a maximum injection speed of the primary air or gas at the end of the burner. This modification of section is obtained by relative displacement along the X axis of the inner and outer tubes of the circuit and by an inclined shape along the X axis of the distributors mounted on the movable ring and the notches of primary radial air or of gases arranged on the outer peripheral part of the inner tube of the circuit.

According to a particular arrangement, the primary air or radial gas injection pipe is disposed outside of fuel circuits (pulverized solid, liquid or other gas). This limits any risk of projection of liquid or solid fuel at the periphery of the flame when the radial component of the air or gas is increased. In addition, this arrangement makes it possible to reduce NOx by a staged combustion effect, by concentrating the fuel in the center of the flame.

According to an even more advantageous arrangement for controlling the flame diameter, the primary air or radial gas injection pipe is sandwiched between an axial air pipe and the center of the burner comprising the combustible pipes (pulverized solid , liquid or gaseous) and possibly the flame stabilizer.

Advantageously, the distributors and the primary air or radial gas injection conduits are of complementary flared shape forming two channels and the sum of the sections of which is variable in a plane perpendicular to X, whatever the angular position of the crown. . In certain applications, the outlet section must be adjustable to maintain a pressure and therefore a maximum injection speed of the primary air or gas at the end of the burner. This section modification is obtained by a relative displacement along the axis X of the movable crown and radial primary air or gas notches arranged on the outer peripheral part of the inner tube of the circuit.

• La figure 1 est une vue en coupe d'un circuit d'air ou de gaz du brûleur selon l'invention,
• La figure 2 est une vue de face du brûleur suivant une disposition particulière,
• Les figures 3 à 5 montrent différentes positions d'un répartiteur à bords curvilignes dans un conduit d'air primaire radial,
• La figure 6a et 6b sont des vues en développé du répartiteur dans les deux positions extrêmes,
• La figure 7 une vue de la couronne,
• La figure 8 est une vue du conduit principal.
• Les figures 9 à 12 montrent des vues de face de différentes dispositions des circuits d'air primaire et combustible au brûleur.
• Les figures 12 et 13 montrent une vue en coupe du brûleur dans une disposition particulière où la section du circuit d'air ou de gaz est réglable. La figure 12 est en position section maximale, la figure 13 en position section minimale
• Les figures 14 et 15 montrent une vue en coupe du brûleur dans une disposition particulière où la section du circuit d'air ou de gaz est réglable par déplacement axial des répartiteurs. La figure 14 est en position section maximale, la figure 15 en position section minimale.
• Les figures 16a et 16b montrent différentes positions des répartiteurs à bords curvilignes dans un conduit d'air primaire radial.
• Les figures 17 et 18 montrent une vue en coupe du brûleur dans une disposition particulière où la section du circuit d'air ou de gaz est réglable.

Other advantages may also appear to those skilled in the art on reading the examples below, illustrated by the appended figures, given by way of example:

• The figure 1 is a section view of an air or gas circuit of the burner according to the invention,
• The figure 2 is a front view of the burner according to a particular arrangement,
• The figures 3 to 5 show different positions of a distributor with curvilinear edges in a radial primary air duct,
• The Figure 6a and 6b are developed views of the distributor in the two extreme positions,
• The figure 7 a view of the crown,
• The figure 8 is a view of the main duct.
• The Figures 9 to 12 show front views of different arrangements of the primary and fuel air circuits to the burner.
• The figures 12 and 13 show a sectional view of the burner in a particular arrangement where the section of the air or gas circuit is adjustable. The figure 12 is in maximum section position, the figure 13 in minimum section position
• The Figures 14 and 15 show a sectional view of the burner in a particular arrangement where the section of the air or gas circuit is adjustable by axial displacement of the distributors. The figure 14 is in maximum section position, the figure 15 in minimum section position.
• The Figures 16a and 16b show different positions of the distributors with curvilinear edges in a radial primary air duct.
• The Figures 17 and 18 show a sectional view of the burner in a particular arrangement where the section of the air or gas circuit is adjustable.

In the following description, the parts placed on the side of the inlet of the primary air will be called "downstream" and "upstream" those placed on the side of the outlet of the primary air.

The burner 1 comprises at least one primary air or gas duct 22 comprised between an outer wall 52 and an inner wall 23 of axis X and constituting concentric tubes of cylindrical shape, surrounding the center of the burner 10 in which can be several other primary air or fuel ducts 100, 101 or a stabilizer 8 are installed. The end of this duct on the furnace side is closed by an inner end ring 2 and an outer end ring 5, which can be as follows the embodiments, two separate parts to facilitate machining or the same part.

The primary air or gas duct has a crown 3, itself surrounded by a ring 4. The downstream end of the duct is encircled by the ring 5. As can be seen in figures 1 , 2 and 8 , the inner ring 2 connected to the inner tube of the wall 23 has on its periphery notches 20 which have two faces 200 and 201 flared relative to each other (or V-shaped), which are closed on their peripheral part by the ring 5 and thus constitutes conduits 21 for injecting radial primary air or gas.

In an advantageous arrangement illustrated, the outer ring 5 comprises conduits 50 for primary air with an axial component.

Crown 3 (cf. figures 1 , 2 and 7 ) has protrusions 30 of flared or V shape which are arranged in the notches 20 and constitute air distributors 30. Each protrusion 30 has two faces 300 and 301 which join downstream and which are respectively parallel to the faces 200 and 201 of the notch 20. The V shape therefore has its point arranged downstream.

The crown 3 rotates around the axis X on the main conduit between two extreme positions, in which the distributor 30 is in abutment on the face 200 of the notch 20 or on the face 201 of said notch 20. The crown 3 has at least one groove 31 disposed in an inclined manner relative to the axis X.

In a particular arrangement illustrated, the ring 4 slides from upstream to downstream on the wall 23 along the axis X. The ring 4 comprises a stud, nut or key 42 which slides in the groove 31. The ring 4 is fixed to the at least one control arm or bar 43 connected to a piston (not shown) in order to slide the ring 4 from upstream to downstream and vice versa.

We will now describe the operation of burner 1, illustrated by the figures 3 to 5 , 6a and 6b .

Each air distributor 30 makes it possible to separate the flow of primary air or gas which arrives in the conduit 21 for injecting radial primary air or gas and to give it a tangential angular component by dividing it into two channels 210 and 211 with different angles. These channels 210 and 211 generate two jets which recombine into a single jet at the outlet and whose mean angle is practically proportional to the outlet angle of each V weighted by the flow rate of each jet. By the rotation of the crown 3, the sectional distribution between the two channels 210 and 211 is varied, the overall section of the channels 210 and 211 being constant over the entire setting and therefore the flow rate in each of the branches of the V to obtain a variation of the exit angle of the air flow 6 without decreasing the ejection speed and keeping the flow constant.

It is thus possible to adjust the component of the radial air or of the gas by adjusting the outlet angle of the jet, at iso pressure, at iso flow, and iso section upstream of the outlet orifice, thus maximizing the jet pulse.

In the embodiment presented in figures 3 to 5 , the channels 210 and 211 are curved, to reduce the pressure drop in the channels by the progressive increase in speed according to the tangential component and allow greater aerodynamic stability of the jet. Indeed, the curved shape gives the underside of the jet a slightly lower expansion speed than that at the underside of the jet. It makes it less turbulent the mixture of the two jets at different angles and therefore more stable the resulting flow and more optimal the average speed of the jet.

To the figure 3 the distributor 30 is placed substantially in the middle, the amount of air which passes through the two channels is substantially identical. To the figure 4 the distributor 30 is pressed against the wall 200 and the majority of the air passes through the more inclined channel 210, the air flow 6 is therefore more strongly inclined. On the contrary to the figure 5 , the distributor 30 is pressed against the wall 201 and the majority of the air passes through the channel 211 less inclined, the air flow 6 is therefore very slightly inclined.

In the figures 3 to 5 , chamfers 303, 203 are provided at the inlet of the air distributor 30 as well as at the inlet of the channels 210 and 211 in a tangent plane or in a vertical plane.

In the view of the figure 2 , the burner comprises an outer protective concrete 7, the outer ring 5 with axial ducts 50, the inner ring 2 with the ducts 21 for injecting radial primary air or gas, and the center of the burner 10 delimited outside by the wall 23 comprising a pulverulent and / or gaseous fuel conduit 100, and other combustible conduits 101 and a central stabilizer 8.

This type of burner can be used both if it has a primary air or single gas outlet with only the primary air ducts 21 or multiple with the primary air or gas ducts 21 and 50.

In the case of a multiple primary air outlet, the conduits 50 and 21 can be supplied with primary air by a single primary air duct 22 or by separate primary air circuits, generally concentric or almost concentric with respect to the 'X axis.

The Figures 9 to 11 show different radial arrangements of the primary air or gas conduits according to the invention and of the annular fuel duct (s) (pulverulent, gaseous fuels).

The figure 9 shows an arrangement with, from the center of the burner, at the stabilizing center 8, fuel conduits 101 in the stabilizer, a pulverulent fuel line 100, primary air or radial gas injection lines 21, one of the axial lines50.

The figure 10 shows an arrangement with, from the center of the burner, at the stabilizing center 8, a fuel duct 101 in the stabilizer, primary air or radial gas injection ducts 21, a pulverulent fuel duct 100, axial ducts 50.

The figure 11 shows an arrangement with, from the center of the burner, at the stabilizing center 8, a fuel duct 101 in the stabilizer, a pulverulent fuel duct 100, one of the primary air or radial gas injection ducts 21 without axial duct .

Other arrangements not shown, such as for example, the pulverulent fuel circuit outside 100 are also possible.

In certain applications and advantageously illustrated figures 12 and 13 , the primary radial air or gas duct 22, the minimum section of the radial component in the plane 216 can be adjusted at the end of the burner to maintain a pressure and therefore a maximum injection speed of the primary air or gas at the end of the burner. This section modification is obtained by the displacement along the axis X of one of the walls 23 or 52 relative to the other, of the inclination of angle α of the inner radial face 315 of the distributors 30 and the outer radial face 215 of the primary radial air or gas notches 20 relative to the axis X, as well as a divergent angle β on the inner radial face 51 of the outer ring 5. Preferably the inner wall 23 is movable and the outer wall 52 is fixed.

On the Figures 16a and 16b , the crown 3 also translates along the axis X on the main conduit between two extreme positions, in which the face 310 of the distributor 30 is in abutment on the face 220 to obtain a minimum passage section. The distributor 30 can be moved back for an increased passage section. The translation of the crown 3 or the rotation of the latter can be done by two relative movements independent. The adjustment of the section can also be carried out by a translation and / or a rotation of the crown.

In the illustrated applications Figures 14 and 15 , in the radial primary air or gas duct 22, the section of the radial component can be adjusted at the end of the burner 1 to maintain a pressure and therefore a maximum injection speed of the primary air or gas at the end of the burner. This section modification is obtained by the translation along the axis X of the crown 30 linked to the control bar 43. In the retracted position, figures 14 , 16b and 17 , the section of the channels 210, 211 are maximum, while when they are pushed, figure 15 , 16a and 18 , the section of the channels 210, 211 are minimum.

We see on Figures 17 and 18 , that the translational movements of the crown 30 are made along the axis X and are controlled by the tube or the control bar 43, as for the rotational movement of the crown 30 it is obtained by the translation of the tube or the control bar 43.

The optimal arrangement for the suction of secondary air into the flame is the installation of this primary air duct outside the fuel ducts and in particular the pulverulent fuel duct. This arrangement limits the projection of solid fuels outside the flame and reduces the formation of nitrogen oxides.

In the case of a burner with several air outlets, have this device located just outside the combustible duct as illustrated figure 2 , in particular the pulverulent fuel conduit (coal, pet coke ...), and generally between the pulverulent fuel conduit and the axial conduit, allows it to be rotated to activate its combustion but also to benefit from an arrangement of the orifices outlet of the primary air duct with tangential component close to the secondary air, in order to benefit from the impulse of this duct for the absorption of the secondary air in the flame.

In the configuration presented in figure 10 , the number of ducts 21 is a multiple of the number of axial ducts 50 or group of axial ducts 50, to improve the absorption of secondary air.

This is optimal when the number of conduits 21 and identical to the number of axial conduits 50 or group of axial conduits 50 and the conduits 21 are on the same radii as the conduits 50 or group of conduits 50.

Claims (14)

1. Burner (1) comprising a primary air or gas duct (22) of axis X delimited by an exterior wall (52) and a concentric interior wall (23) and ducts (21) for radial gas or primary air injection, characterized in that the air or gas duct (22) comprises a ring (3) that is rotationally mobile and has axial protrusions constituting distributors (30) which collaborate with the radial primary air ducts (21) arranged on the exterior peripheral part of the interior wall and form two passages (210, 211) of different angles in each duct (21).
2. Burner (1) according to the preceding claim, characterized in that the ring (3) is translationally mobile.
3. Burner (1) according to Claim 1, characterized in that the two passages (210, 211) are formed by complementary flared shapes of the distributor (30) and of the radial gas or primary air ducts (21) and that the sum of the sections of the said passages is constant is a plane perpendicular to X, whatever the angular position of the ring (3).
4. Burner (1) according to one of the preceding claims, characterized in that the distributors (30) and the radial gas or primary air ducts (21) have walls (200, 300; 201, 301) with parallel edges.
5. Burner (1) according to Claim 1 or 2, characterized in that the distributors (30) and the radial gas or primary air ducts (21) have curvilinear edges.
6. Burner (1) according to one of Claims 1 to 4, characterized in that the radial primary air ducts (21) and the distributors (30) are chamfered at the upstream end.
7. Burner (1) according to one of Claims 1 to 4, characterized in that it comprises axial primary air ducts (50).
8. Burner (1) according to the preceding claim, characterized in that the radial primary air duct (21) is sandwiched between the fuel ducts and the axial primary air duct.
9. Burner (1) according to the preceding claim, characterized in that the axial primary air and radial primary air ducts (50, 21) are fed from the same supply (22).
10. Burner (1) according to Claim 7, characterized in that the number of gas or of radial primary air ducts (21) is a multiple of the number of axial ducts or of a group of axial ducts (50).
11. Burner (1) according to the preceding claim, characterized in that the gas or radial primary air and axial air ducts (50, 21) are arranged on the same radii.
12. Burner (1) according to one of Claims 5 and 6, characterized in that the ring (3) comprises at least one slot (31) inclined with respect to the inclination axis X, and in that the length of the slot (31) is proportional to the rotation of the ring (3).
13. Burner (1) according to Claim 3, characterized in that the duct (21) has an outlet section (216), that this outlet section (216) varies as a function of the movement of one wall (52, 23) with respect to the other (23, 52), that the interior radial face (315) of the distributors (30) and the external radial face (215) of the notches (20) make an angle α with the axis X, and that the interior radial face (51) of the exterior annulus (5) makes an angle β with the axis X.
14. Burner (1) according to Claim 2, characterized in that the distributors (30) and the radial primary air ducts (21) are of complementary flared shape, forming two passages (210) and (211) of which the sum of the sections is variable in a plane perpendicular to X, whatever the angular position of the ring (3).

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