ES2942061T3 - adjustable flame burner - Google Patents

Abstract

The invention refers to a burner (1) comprising an annular fuel transport circuit (2) delimited by an inner tube (3) and an outer tube (4) substantially concentric along a longitudinal axis (X), said circuit having : - an upstream part (2A) and a downstream part (2B) in the direction of fuel flow ending in an open end (2C), - a distance (S) between the inner tube (3) and the outer tube (4) which is variable between the upstream portion (2A) and the downstream portion (2B) of said annular circuit (2), the burner (1) further comprising a bypass member (5) configured to impart a radial component to the fuel that travels in said annular circuit (2) from the upstream part (2A) to the open end (2C). According to the invention, said deflector element (5) can be moved between the upstream part (2A) and the downstream part (2B). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

adjustable flame burner

technical field

The invention relates generally to the field of burners, for example burners for rotary kilns, such as cement kilns or lime kilns. More particularly, the invention relates to a burner comprising means for adjusting the shape of the flame thereof.

state of the art

In rotary kiln installations known from the prior art, most of the combustion air, generally called secondary air, reaches a very high temperature (often between 300 and 1200°C) after it has been used as cooling air. for hot material falling from the kiln. For example, in a cement kiln, secondary air represents between 80 and 95% of the combustion air.

To ensure proper furnace operation, supplemental air is injected into the burner at a lower temperature, often at room temperature. This supplementary air, also called primary air, is injected at the end of the burner, at high pressure (generally between 100 and 500 mbar) in order to:

- Aspirate the hot secondary air into the core of the flame and ensure that it mixes quickly with the burner fuel in order to activate combustion.

- Control, by means of its axial and radial components, the shape of the flame (width and length) and, therefore, allow adaptation to the specific conditions of the oven.

In known burners, a problem arises when a significant amount of fuel is injected, for example in gaseous form or in the form of a pulverized solid and carried by a large volume of air. In fact, in this case, the momentum generated by this fuel injection can be much greater than the momentum generated by the primary air. As a consequence, the shape of the flame and its thermal profile can be significantly affected by this fuel injection and therefore the influence of the primary air on the shape of the flame becomes inadequate.

However, controlling the shape of the flame is important, as negative consequences can occur, including:

- a reduction in the flexibility of the burner,

- inadequate temperature profiles in the furnace, which affects its operation and increases the risk of damage to components, such as refractory bricks,

- deficient control of the level of nitrogen oxide (NOx) emissions produced by combustion. The objective of the present invention is to propose a burner that provides better adjustment of the flame shape and, as a consequence, that allows addressing the aforementioned problems.

Document US2002174810 describes a burner according to the preamble of claim 1.

Description of the invention

To this end, the object of the invention is a burner comprising an annular circuit for transporting fuel delimited by an inner tube and an outer tube substantially concentric along a longitudinal axis, said circuit having:

- an upstream part and a downstream part in the direction of fuel flow, the downstream part terminating in an open end; and

- a distance between the inner tube and the outer tube variable between the upstream part and the downstream part of said annular circuit.

The burner further comprises a diversion element configured to confer a radial component to the flow direction of a fuel moving in said annular circuit from the upstream part towards the open end.

According to the invention, said diverting element is placed in the annular circuit for transporting fuel and can move in translation between the upstream part and the downstream part of said circuit.

The fuel may be in the form of a fluid, eg a gas, or in the form of a pulverized solid carried by a fluid such as a gas, optionally having a calorific value, or air.

The burner according to the invention comprises a diversion element configured to adjust the shape of the flame by adjusting the effective fuel injection angle into the furnace. In fact, on the one hand, the distance between the first tube and the second tube is variable between the upstream part and the downstream part.

On the other hand, the diverting element can move in translation between the upstream part and the downstream part of the circuit to transport fuel.

Since the effective injection angle results from its axial component and its radial component, its value depends on the position of the deviation element in the circuit. In fact, the more it is positioned in an area where the circuit is narrow (the distance between the two tubes is reduced), the more fluid passes through the deflection element and, therefore, the more the radial component increases. Conversely, the more the diversion element is positioned in an area where the circuit expands (the distance between the two tubes increases), the smaller the radial component, because a significant amount of the fuel continues its axial trajectory and does not passes through the deflection element.

In other words, depending on the position of the diversion element in the annular circuit and the distance between the inner tube and the outer tube in line with the diversion element, the diversion element occupies all or part of the annular circuit to transport fuel. Therefore, when the bypass element occupies the entire annular circuit, all the fuel passes through the bypass element. Conversely, when the bypass element occupies only part of the annular circuit, only part of the fuel passes through the bypass element, the rest passing through the free space around the bypass element. The proportion of fuel passing through the bypass element is therefore greater when the ratio between the section of the bypass element and that of the annular circuit is low.

As a consequence, the effective injection angle of the fuel can be changed by moving the diverter member back or forth between the upstream and downstream parts of the burner.

Therefore, in this way, it is possible to adjust the shape of the flame to adapt to variations in the operating conditions of the furnace or the properties of the injected fuel, in particular when the momentum generated by injecting this fuel is greater than that generated by injecting the primary air.

Said adjustment also allows to reduce the level of nitrogen oxide emissions by placing the diversion element in an appropriate position.

According to one embodiment, the inner tube is fixed with respect to the outer tube.

According to another embodiment, said distance between the inner tube and the outer tube is greater in the upstream part than in the downstream part of the circuit for transporting fuel. The narrowing of the circuit in the downstream part makes it possible, in particular in the case of gaseous fuels, to increase the radial component that is conferred by the deflection element when it is in the advanced position in the downstream part.

Advantageously, the open end is provided with a convergent system configured to cause the fuel at the burner outlet to converge towards the longitudinal axis. The conversion of the fuel towards the center of the burner makes it possible, in particular in the case of a producer gas, to promote an air/gas mixture and to shorten the flame.

According to one embodiment, the distance between the inner tube and the outer tube is smaller in the upstream part than in the downstream part.

Increasing the distance between the two downstream tubes makes it possible to reduce the radial component at the tube outlet and, as a consequence, to reduce the fuel outlet velocity, so that it is close to the velocity at the circuit inlet.

When the diversion element is positioned in the downstream part, it covers part of the distance between the two tubes. In this case, the shorter the distance between the outer tube and the bypass element, the higher the fuel outlet velocity will be. However, an excessive increase in this output velocity can create rapid burner wear and will damage the downstream part of the circuit, due to the abrasive nature of some fuels, particularly solid fuels. Therefore, increasing the downstream part allows to address this problem.

Advantageously, the open end comprises an additional element that reduces the distance between the inner tube and the outer tube in the vicinity of said open end.

In this case, when the downstream part of the circuit has a distance between the inner tube and the outer tube that is greater than in the upstream part, said distance is further reduced, at the open end, by the additional element so that , for example, is close to the distance between the two tubes in the upstream part. Therefore, an identical or close effective distance can be maintained between the two tubes at the inlet and the outlet of the downstream part. This allows the variation of the fuel velocity to be limited depending on the position of the bypass element.

Advantageously, the additional element has a shape configured to cause the fluid at the burner outlet to converge towards the longitudinal axis.

In the case of solid fuels, the concentration of fuel in the center of the burner makes it possible to maintain a low level of nitrogen oxide formation. In fact, the concentration of the fuel with a low oxygen level encourages the formation of HCN and NH3 radicals that change to give N2 instead of NOx.

Advantageously, the deflection element has an annular shape. This results in a homogeneous flame along its circumference. The annular shape also facilitates the manufacture of the burner. As a variant, the deflection element can have an asymmetrical shape to promote the development of the flame in a particular direction, for example, towards the bottom or towards the top of the furnace. In this case, the means for moving the deflection element may comprise means for adjusting the angular position of the deflection element in order to orient the flame in the desired direction.

Advantageously, the distance between the inner tube and the outer tube has a minimum value and the deflection element has a height equal to said minimum value.

Therefore, when the bypass member is at the part where the distance between the two tubes is minimal, all the fuel passes through the bypass member, which allows the radial component of the injection angle to be maximized.

According to one embodiment, the distance between the inner tube and the outer tube has a minimum value and a maximum value, the minimum value being less than or equal to 85% of the maximum value.

Advantageously, the deflection element comprises blades, said blades being able to have a radial angle that is set between 5° and 50°.

The invention also relates to a kiln, in particular a rotary kiln, comprising a burner according to the above description.

The features of the embodiments described herein above can be taken separately or together or even in various combinations.

Brief description of the figures

The invention will be better understood, and additional features and advantages will become apparent, upon reading the following description, with reference to the accompanying drawings, in which:

figure 1 shows a partial view of a burner according to the invention with the deflection element in a first position;

figure 2 shows the burner of figure 1 with the deflection element in a second position;

figure 3 schematically shows a view in longitudinal section of the burner with the deflection element in the position of figure 1;

figure 4 schematically shows a view in longitudinal section of the burner with the deflection element in the position of figure 2;

Figure 5 schematically shows a longitudinal sectional view of a burner according to a second embodiment of the invention with the deflection element in a first position;

figure 6 schematically shows a longitudinal sectional view of the burner of figure 5 with the deflection element in a second position;

Figure 7 schematically shows a longitudinal sectional view of the burner according to a third embodiment of the invention with the deflection element in a first position;

figure 8 schematically shows a longitudinal sectional view of the burner of figure 7 with the deflection element in a second position;

figure 9 and figure 10 show variants of the burner of figure 8 with the deflection element in the same position.

Detailed description

Figures 1 and 2 show a partial view of an example of a burner according to the invention that can be used with gaseous fuels, for example, in a cement kiln.

The burner 1 comprises an inner tube 3 and an outer tube 4 substantially concentric along a longitudinal axis X visible in figure 3. The two tubes 3 and 4 form an annular circuit 2 for conveying fuel. The circuit 2 for transporting fuel has, in the fuel flow direction, an ^upstream part 2 and a downstream part 2B ending at one end 2C.

The burner 1 further comprises a diversion element 5 comprising, for example, blades 6 oriented to rotate the flow of fuel passing through this diversion element 5. Therefore, the fuel flow at the outlet of the diversion element comprises an axial component and a radial component. It should be noted that, in figure 1, the outer wall of the deflection element 5 has not been shown in order to better show the blades 6. This outer wall is visible in figure 2.

As shown in figure 1, the diversion element 5 is in a first position P0 at the end 2C of the circuit 2. The flame formed by the burner 1 resulting from the position P0 of the diversion element 5 has a first shape F0.

According to the invention, the diversion element 5 can move in translation in the circuit 2 to transport fuel between the upstream part 2A and the downstream part 2B. A mechanism, not shown, to move the deflection element 5 can be installed, for example, at the rear of the burner 1.

According to the invention, in Figure 2, the deflection element 5 has been moved to position itself in the upstream part 2A of the circuit 2. As a consequence, in this position P1, the shape of the resulting flame F1 is different.

In this embodiment, the inner tube 3 and the outer tube 4 are fixed with respect to each other. In other embodiments, not illustrated, the inner tube is movable with respect to the outer tube. For example, the deflection element can be fixed to the inner tube and therefore can move at the same time as the inner tube with respect to the outer tube.

Figure 3 schematically shows a longitudinal sectional view of burner 1 as shown in Figure 1. Circuit 2 in this embodiment has a distance S between inner tube 3 and outer tube 4 that varies from upstream to downstream. More specifically, the distance has a maximum value Smax in the upstream part 2A and a minimum value Smin in the downstream part 2B. In this embodiment, the distance S gradually decreases from upstream to downstream along the length Cmin shown in Figure 4. However, in other embodiments, not illustrated, the variation of the distance S can be abrupt.

The deflection element 5 has a height H, which, in this embodiment, is equal to the minimum value Smin.

In other embodiments, not illustrated, H can differ from Smin, in particular be less than Smin.

Therefore, at the position P0 shown in Fig. 3, the fuel flow completely passes through the diversion member 5 at the end 2C. As a result, during this step, the entire fuel flow is diverted by the diverting element 5 giving it a radial component, thus resulting in the flame shape F0 shown in Figure 1.

Since the effective injection angle of the fuel in the furnace results from its axial component and its radial component, it therefore assumes a maximum value at position P0.

Figure 4 shows a longitudinal sectional view of the burner 1 as shown in Figure 2 and in which the deflection element is in position P1.

In this case, a portion of the fuel Cb flowing between the upstream part 2A and the downstream part 2B passes through the bypass element 5. The other portion passes directly from the upstream part ² to the downstream part 2B without passing through the diversion element 5, as illustrated by the arrows. Therefore, only the portion that passes through the deflection element 5 has a radial component. As a consequence, the shape of the flame F1 at the position P1 is changed.

The distance Cmin is the minimum distance between the part of the circuit 2 in which the distance S is minimum Smin and the part in which the distance S is maximum Smax.

In other embodiments, not illustrated, the deflection element 5 can assume any other position between the upstream part 2A and the downstream part 2B by adjusting movement means 7. In this way, it is possible to modify the shape of the flame as needed.

In addition, the inner tube 3 can carry in it, in a known or discontinuous manner, a fuel, air or even a fuel/air mixture.

Lastly, the burner 1 can comprise other elements present in burners known to an expert. Figures 5 and 6 schematically show a second embodiment of a burner according to the invention, in particular intended for the combustion of lean gases with a view to their reuse, for example, for the production of steam.

The burner 10 comprises an inner tube 30 and an outer tube 40. The two tubes 30 and 40 form an annular circuit 20 for transporting fuel. The circuit 20 for conveying fuel has an upstream part 20A and a downstream part 20B terminating at one end 20C.

The burner 10 also comprises a deviation element 50 positioned in the circuit 20 and configured to be able to move in translation between the upstream part 20A, as illustrated in Figure 6 (position P1'), and the downstream part 20B, as it is illustrated in figure 5 (position P0').

In this embodiment, a pilot gas G is injected through a central tube 60 to guarantee the pilot flame function before injecting producer gas Gp. Once the producer gas flame Gp has been established, the pilot flame can be extinguished by closing the pilot gas inlet G. However, in some cases the pilot flame can be maintained.

To guarantee the correct operation of the burner, most of the air A (secondary air) is injected between the tubes 60, 61 and 61, 30, which are coaxial to the central tube 60. This air A can advantageously pass through a deflection element 62 to add a radial component to its movement.

The producer gas Gp arrives through a side inlet E with an angle close to 90°, and then the producer gas is directed to the upstream part 20A, as shown by the arrows. The producer gas Gp is then transported in circuit 20 to end 20C, where it is directed to be burned in the combustion chamber and to produce steam. In a similar way to the embodiment of figures 1 to 4, depending on the position of the deflection element 50, which may be similar to the deflection element 5 described above, which is obtained by adjusting a movement means 51, it is possible to adjust the shape of the resulting flame.

Advantageously, the end 20C can comprise a converging system 21 configured to cause the fuel at the burner outlet 10 to converge towards the longitudinal axis X.

Burner body B is only partially shown. It can take any form and/or element known to an expert.

Figures 7 and 8 show another example of a burner 100 according to the invention. The burner 100 is intended to burn pulverized solid fuels, such as coal, with reduced emission of NOx gas.

The burner 100 comprises an inner tube 300 and an outer tube 400. The two tubes 300 and 400 form an annular circuit 200 for transporting a combustible PC. The circuit 200 for transporting fuel has an upstream part 200A in the fuel flow direction and a downstream part 200B terminating at one end 200C. Unlike the previous embodiments, the distance S between the inner tube 300 and the outer tube 400 has a maximum value Smax at the downstream part 200B and a minimum value Smin at the upstream part 200A.

The variation of the distance S between the upstream part and the downstream part is abrupt in this embodiment. However, it may be gradual in other embodiments, not shown.

The burner 100 further comprises a bypass element 500, which may be similar to the bypass element 5 described above. This deflection element 500 is configured to be able to move translationally in the circuit 200. In the example shown, the deflection element 500 can move more specifically between one end of the upstream part, represented by step 301, and the downstream end 200C.

In this exemplary embodiment of the invention shown in figure 7 (position P0") and in figure 8 (position P1"), the burner also comprises two external circuits for transporting two other fluids AA and RA, for example, other fuels, combustion air or a mixture between a fuel and air. As a variant, the inner tube 300 can also carry a complementary fluid Q therein.

Figure 9 shows a variant of the embodiment of Figure 8, in which the end 200C is provided with an additional element 201 that makes it possible to reduce the distance S at this end. Advantageously, the resulting distance S is equal to the height H of the deflection element. For example, this can make it possible to maintain the same distance S=Smin at the inlet and outlet of the downstream part 200B. Therefore, the variation in the fuel velocity is limited depending on the position of the deflector member 500.

Figure 10 shows another variant of the embodiment of Figure 8, in which the end 200C is provided with an additional element 202 having a shape configured to cause the fluid at the outlet of the burner 100 to converge towards the longitudinal axis X. This This variant allows further reduction of NOx and concentration of the fuel in the center of the burner 100, especially if it is a pulverized solid fuel.

In each of the embodiments described above, element 5; fifty; Deflection 500 may have an annular shape. It can also comprise blades and other elements or shapes known to an expert.

Advantageously, said blades have a deflection angle of between 5° and 50°.

Advantageously, in each of the embodiments described, Smin can be less than or equal to 85% of Smax.

In the exemplary embodiments described above and shown in the figures, the fuel that does not pass through the baffle element passes outside the baffle element, i.e., in the space located between the baffle element and the outer tube. . As a variant, the fuel that does not pass through the bypass element circulates in the space located between the bypass element and the inner tube.

Claims (9)

1. A burner (1; 10; 100) comprising an annular circuit (2; 20; 200) that transports fuel delimited by an inner tube (3; 30; 300) and a substantially outer tube (4; 40; 400). concentric along a longitudinal axis (X), having said circuit: - a part (2A; 20A; 200A) upstream and a part (2B; 20B; 200B) downstream in the fuel flow direction ending in an open end (2C; 20C; 200C), - a distance (S) between the inner tube (3; 30; 300) and the outer tube (4; 40; 400) variable between the part (2A; 20A; 200A) upstream and the part (2B; 20B; 200B ) downstream of said annular circuit (2; 20; 200), the burner (1; 10; 100) also comprising a deviation element (5; 50; 500) configured to confer a radial component to a direction of the fuel that moves in said annular circuit (2; 20; 200) of the part (2A; 20A; 200A) upstream towards the open end (2C; 20C; 200C), characterized in that said deflection element (5; 50; 500) can move in translation between the part (2A; 20A; 200A) upstream and the part (2B; 20B; 200B) downstream and where the inner tube (3; 30; 300) is fixed with respect to the outer tube (4; 40; 400). The burner (1; 10) according to claim 1, wherein said distance (S) between the inner tube (3; 30) and the outer tube (4; 40) is greater in the downstream part (2A; 20A). above than in the part (2B; 20B) downstream of the annular circuit (2; 20). The burner (10) according to one of claims 1 to 2, wherein the open end (20C) is provided with a converging system (21) configured to make the fuel converge at the burner outlet (10) towards the axis longitudinal (X). The burner (100) according to claim 1, wherein the distance (S) between the inner tube (3; 30) and the outer tube (4; 40) is smaller in the upstream part (200A) than in the downstream part (200A). part (200B) downstream. The burner (100) according to claim 4, wherein the open end (200C) comprises an additional element (201; 202) that reduces the distance (S) between the inner tube (300) and the outer tube (400). in the vicinity of said open end (200C). The burner (100) according to claim 5, wherein the additional element (202) has a shape configured to converge the fluid at the outlet of the burner (100) towards the longitudinal axis (X). The burner (1; 10; 100) according to one of the preceding claims, wherein the deflection element (5; 50; 500) has an annular shape. The burner (1; 10; 100) according to one of the preceding claims, wherein the distance (S) between the inner tube (3; 30; 300) and the outer tube (4; 40; 400) has a value minimum (Smin), the deviation element (5; 50; 500) has a height (H) equal to said minimum value (Smin). The burner (1; 10; 100) according to any one of the preceding claims, wherein the distance (S) between the inner tube (3; 30; 300) and the outer tube (4; 40; 400) has a minimum value (Smin) and a maximum value (Smax), the minimum value (Smin) being less than or equal to 85% of the maximum value (Smax).