EP2017529B1 - Burner - Google Patents

Description

The present invention relates to a burner, in particular a burner for a cement plant.

An axially extending type burner is known comprising an axial flow primary air supply annulus which surrounds all of the fuel supply lines and which is delimited by an inner tube extending along the axis of the burner and a co-axial outer tube to the inner tube, the two tubes being axially movable relative to each other in translation in the axial direction between an open position and a closed position .

Such a burner is for example disclosed in the patent application EP 967 434 , is usually used for cement plants, and includes two primary air supply lines surrounding all fuel supply lines of the burner. These two lines are the axial flow air supply line at the outlet of which the flow of air is parallel to the burner axis, possibly with a slight radial component, and a flow air supply line. tangential output of which the flow of air has a tangential component so as to form a swirling flow around the axis of the burner. In addition, such a burner is generally surrounded by secondary air supply lines.

Another burner is disclosed by the document EP421903 .

The disadvantage of such a burner is the relative difficulty of varying the characteristics of the flame in a wide range, and controlling them, whereas, particularly in cement kilns, these characteristics have a great influence on the quality of the cooking of the material for the manufacture of cement.

According to the invention, this difficulty is solved by the implementation of a burner according to claim 1.

By this arrangement it is thus possible, easily, to activate more or less significantly the flame produced by the burner. In the open position, the outlet air, coming both from the grooves formed in the flange and the annular space between the flange and the second tube, is distributed continuously over the entire periphery of the pipe, and thus surrounds the flame and thus protects the beginning of the latter from the rapid introduction of secondary air, which in particular reduces the rate of nitrogen oxides. On the contrary, in the closed position, the outlet air, originating solely from the grooves formed in the flange, is distributed discontinuously over the entire periphery of the pipe, and the air jets (corresponding to each groove) attract air secondary (usually having a high temperature) from the origin of the flame, which activates the latter and allows to activate the cooking of the material in the oven.

• La figure 1 est une vue en coupe axiale d'une portion de la tête d'un brûleur, les tubes agencés conformément à un premier mode de réalisation de la présente invention, étant en position d'ouverture ;
• La figure 2 est une vue du premier mode de réalisation, similaire à la figure 1, les tubes étant en position de fermeture ;
• La figure 3 est une vue partielle en perspective d'un tube portant une bride conformément à la présente invention ;
• La figure 4 est une vue d'un second mode de réalisation, similaire à la figure 1, les tubes étant en position d'ouverture ; et
• La figure 5 est une vue du second mode de réalisation, similaire à la figure 4, les tubes étant en position de fermeture.

Other features and advantages of the present invention will appear in the description of two embodiments given as non-limiting examples and illustrated in the appended drawings in which:

• The figure 1 is an axial sectional view of a portion of the head of a burner, the tubes arranged according to a first embodiment of the present invention being in the open position;
• The figure 2 is a view of the first embodiment, similar to the figure 1 the tubes being in the closed position;
• The figure 3 is a partial perspective view of a tube carrying a flange according to the present invention;
• The figure 4 is a view of a second embodiment, similar to the figure 1 the tubes being in the open position; and
• The figure 5 is a view of the second embodiment, similar to the figure 4 , the tubes being in the closed position.

The figure 1 illustrates a portion of a burner 1 which extends along an axis 2 and which conventionally comprises solid fuel supply lines and / or liquid and / or gas and a central duct air intake which is used to allow the attachment of the flame to a flame stabilizer and to cool the latter.

The burner 1 also comprises a tangential flow primary air supply peripheral duct 3 which surrounds the central air supply duct and, in the present example, all the fuel supply ducts. This tangential flow primary air supply peripheral duct 3 comprises devices making it possible to impart a tangential component to the flow of air at its outlet. Furthermore, preferably, the tangential flow air supply line 3 is in accordance with one or the other of the conduits disclosed in the two patent applications. FR 2,887,597 and FR 06 04 829 .

The burner 1 further comprises a peripheral axial flow primary supply pipe 4 at the outlet of which the air has a substantially axial flow, that is to say without tangential component (or at least whose component tangential is weak, less than 10 ° with respect to the axis 2 of the burner 1). In this case, the airflow is axial. This axial flow primary air supply peripheral pipe 4 surrounds all the fuel supply pipes and the central air supply pipe. Here, the axial flow air supply pipe 4 surrounds the tangential flow air supply pipe 3.

More precisely, as can be seen in Figures 1, 2 , 4 and 5 , the axial flow air supply line 4 is delimited by two tubes 5, 6 movable relative to one another in translation along the axis 2 of the burner 1, an inner tube 5 which, in the present embodiments, defines the axial flow air supply line 4 of the supply line tangential flow air 3, and an outer tube 6 which is coaxial with the inner tube 5 and forms the tube defining the burner 1 of the secondary air supply lines. The two tubes 5, 6 are axially movable between an open position and a closed position.

As can be seen at Figures 1 to 5 , one of the two tubes (in this case, the inner tube 5) carries, near its downstream end 7 (here, at its downstream end 7), an annular flange 8 (stationary relative to the inner tube 5) . This annular flange 8 has grooves 9 which are regularly distributed angularly, which pass through it from one side, and which extend parallel to the axis 2 of the burner 1. In this case, the grooves represent about one third of the periphery of the flange 8.

In the present embodiments, each groove 9 is delimited on the one hand by a bottom wall 10 which, in this case, does not have any inclination in the direction of a displacement along the axis 2 of the burner 1, and, secondly, by two side walls 11 which, in this case, are parallel to each other and to the direction of the axis 2 of the burner 1, and are normal to the bottom wall 10. Here, the grooves 9 made in the annular flange 8 are open radially along their length, the flange 8 not carrying an upper wall facing the bottom wall 10.

Furthermore, the annular flange 8 has an upstream end 12 which has a radial inclination in the direction of a coming towards the outer tube 6 for a displacement along the axis 2 of the burner 1 upstream downstream. In this case, the upstream end of the flange is conical (to the upstream orifices of the grooves 9) with a cone center disposed upstream of the tube.

The other tube (in this case, the outer tube 6) comprises a closing portion 13, 15 (stationary with respect to the outer tube 6) which is arranged so that, when the two tubes 5, 6 are in position d opening, the distance separating the closing portion 13, 15 of the flange 8 allows a significant passage of air between the flange 8 and the second tube 6 in order to have an axial air flow at the outlet of the pipe 4 angularly continuous (cf. figures 1 and 4 ), and when the two tubes 5, 6 are in the closed position, the distance separating the closing portion 13, 15 of the flange 8 is substantially zero in order to have an air flow at the outlet of the pipe 4 angularly discontinuous and limited to the angular sectors corresponding to the grooves 9 (cf. figures 2 and 5 ).

In this case, in the first embodiment, the closing portion 13 is a surface having a radial inclination in the direction of a spacing of the inner tube 5 for a displacement along the axis 2 of the burner 1 upstream downstream. In this case, the closing portion 13 is conical with a cone center disposed upstream of the tube. Here, the half-angle at the top of the cone is about 10 °. In addition, the downstream end 14 of the closing portion 13 is the downstream end 14 of the outer tube 6.

So, at the figure 1 , the two tubes 5, 6 are in an open position in which an annular space exists (and is relatively large) between the flange 8 and the outer tube 6. On the contrary, figure 2 , the two tubes 5, 6 are in a closed position where the closing portion 13 is substantially in abutment against the annular flange 8 (against the upstream end 12 of the flange 8), thus limiting the passage section of the air in the grooves only 9. In the closed position, the flange 8 is in a position which is upstream of the position it takes when the tube which carries it is in the open position.

In the second embodiment, the closing portion 15 comprises a first surface 16 having a radial inclination in the direction of an approximation of the inner tube 5 for a displacement along the axis 2 of the burner 1 from upstream to the downstream. In this case, the first surface 16 is conical with a cone center disposed downstream of the tube. Here, the half-angle at the top of the cone is about 10 °. In addition, the closing portion 15 comprises a second surface 17 (cylindrical) extending in the downstream direction, the first surface 16. The second surface 17 has a diameter equal to the outer diameter of the flange 8 (the clearance necessary for the sliding of two tubes close).

So, at the figure 4 the two tubes 5, 6 are in an open position in which an annular space exists between the flange 8 and the outer tube 6.

On the contrary, figure 5 the two tubes 5, 6 are in a closed position where the cylindrical surface 17 covers the annular flange 8, thus limiting the air passage section to the grooves 9 only.

It is possible that the flange is carried by the outer tube and the closing portion by the inner tube.

It would also be possible for the annular flange to have a different shape, especially at its upstream end, and / or to have upper walls facing the bottom walls and delimiting, with these and the side walls, the grooves. It would also be possible for the bottom walls to have a slight radial inclination (less than 10 °) in order to impart a radial component to the air flow at their outlet, and / or that the lateral walls have a tangential component in order to confer a component tangential to the flow of air at their output.

It would thus be possible to use such a system (flange and closing portion) in any other pipe, and in any other burner.

It would also be possible for the closure portion to be a surface having a radial inclination in the direction of a spacing of the inner tube for a displacement along the axis of the burner from downstream to upstream (for example, the portion of closure could be tapered with a cone center disposed downstream of the tube, with an apex half-angle of about 10 °). In the open position the two tubes define between them an important annular space at the flange, and in the closed position (position in which the flange is downstream of the position it takes when the tube that carries it is in opening position), the closing portion would be substantially in abutment against the annular flange (against the downstream end of the flange), thus limiting the section of passage of the air to the grooves only.

Claims (9)

1. Burner (1) extending along an axis (2) and comprising a peripheral axial flow primary-air supply pipe (4) which surrounds the collection of fuel supply pipes and the central air supply pipe, and which is delimited by an inner tube (5) extending along the axis (2) of the burner (1) and by an outer tube (6) coaxial with the inner tube (5), the two tubes (5, 6) being axially mobile one relative to the other in translation in the axial direction between an open position and a closed position, a first of the two tubes (5, 6) bearing, near its downstream end (7), an annular flange (8) that has slots (9) running substantially in the axial direction of the tube, characterized in that the second tube comprises a closure portion (13, 15) arranged in such way that when the two tubes (5, 6) are in the open position, the distance radially separating the closure portion (13, 15) from the flange (8) allows a significant passage of air between these two members (8, 13), and when the two tubes (5, 6) are in the closed position, this distance is substantially zero so that almost all of the air passes via the slots (9).
2. Burner (1) according to Claim 1, characterized in that the slots (9) are uniformly angularly distributed.
3. Burner (1) according to one of Claims 1 and 2, characterized in that the slots (9) are open radially over their entire length.
4. Burner (1) according to one of Claims 1 to 3, characterized in that the annular flange (8) has an upstream end (12) that exhibits a radial inclination in the direction of converging towards the second tube (6) with progression from the upstream to the downstream direction.
5. Burner (1) according to one of Claims 1 to 4, characterized in that the annular flange (8) is situated at the downstream end (7) of the first tube (5).
6. Burner (1) according to one of Claims 1 to 5, characterized in that the closure portion (13) has a radial inclination in the direction of diverging from the first tube (5) with progression from the upstream to the downstream direction, and is substantially in abutment against the flange (8) when the two tubes (5, 6) are in the closed position, so as to limit the section available for the passage of air to the slots (9) alone.
7. Burner (1) according to Claim 6, characterized in that the closure portion (13) is a conical surface the vertex half-angle of which is substantially 10°.
8. Burner (1) according to one of Claims 1 to 5, characterized in that the closure portion (15) comprises, on the one hand, a first surface having a radial inclination in the direction of converging towards the first tube (5) with progression from the upstream to the downstream direction and, on the other hand, downstream of the first surface (16), a cylindrical second surface (17) with a diameter substantially equal to the outside diameter of the flange (8).
9. Burner according to one of Claims 1 to 9, characterized in that the axial flow air supply pipe (4) surrounds a peripheral tangential-flow primary-air supply pipe (3).

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