CN116829873A

CN116829873A - Industrial burner and apparatus for reducing emissions

Info

Publication number: CN116829873A
Application number: CN202180079095.9A
Authority: CN
Inventors: 卢卡·博尔吉; 阿莱西奥·维森丁; 瓦伦蒂娜·莫恰; 乔瓦尼·乌格杜勒纳
Original assignee: Baide Co ltd
Current assignee: Baide Co ltd
Priority date: 2020-11-25
Filing date: 2021-11-25
Publication date: 2023-09-29
Also published as: IT202000028400A1

Abstract

An industrial burner (1) for reducing emissions, mountable in a combustion chamber (3), and comprising a first tubular discharge element (5) to supply a primary fuel flow (PF) configured to produce a flame Foot (FR); -a second supply duct (7) for generating a Main Flame (MF); at least one third supply duct (8) for supplying an oxidizing agent (OX). The burner (1) further comprises a second tubular discharge element (11) and a suction element configured to flow at least a portion of the gas (G) present outside the burner (1) into the second tubular discharge element (11) and comprising at least one opening (13) arranged between the first tubular discharge element and the second tubular discharge element (11) and which sucks the gas (G) present outside the burner (1) thanks to a zone of low air pressure generated in the region of the suction element.

Description

Industrial burner and apparatus for reducing emissions

Cross Reference to Related Applications

This patent application claims priority to italian patent application nos. 102020000028394 and 102020000028400, both filed 11/25 in 2020, the entire disclosures of which are incorporated herein by reference.

Technical Field

The present invention relates to an industrial burner and apparatus for reducing emissions to heat fluids. In particular, the present invention finds advantageous, though not exclusive, application in monolithic burners with diffusion flames, to which explicit reference will be made in the following description, without being relaxed by this generality.

Background

In industrial applications heating of fluids, such as air or water for boilers, foundries, roasting systems, kilns, etc., is typically performed by using industrial burners placed in boiler and kiln combustors, which are defined by at least two opposing walls, ceilings or tubular or box-shaped bodies. These chambers are typically heated by one or more burners arranged in series, depending on the use scenario. In particular, the burner installed in the boiler is typically an integral burner, i.e. with a corresponding fan and control panel on the burner.

In order to obtain a fast and uniform heating and to optimize efficiency and emissions, the operating cycle of the burner using methane (or mixture or LPG) is usually designed with the highest precisionDegree. In this regard, the emissions most frequently of interest in recent years must be nitrogen oxides (NO _X )。

During the heat treatment, NO is present at high temperature and in the presence of large amounts of oxygen _X Starting from the nitrogen normally present in the oxidizing agent (atmosphere). However, in the case of ideal combustion, nitrogen oxides are not part of the combustion products, since nitrogen is known to be inert at relatively low temperatures. Thus, since the temperature peak is reached in the intermediate (transition) stage of combustion, nitrogen molecules (N ₂ ) To nitrogen atoms, on the other hand, the nitrogen atoms are extremely reactive when in contact with oxygen, which also has an atomic dissociation, resulting in NO _X Is formed by the steps of (a).

In addition, the extreme temperature drop that occurs at the final stage of combustion or away from the flame in the burner freezes the reaction, thereby preventing the recombination of nitrogen and oxygen, thus converting the by-product NO _X Discharged downstream. Nitrogen oxides are generally considered pollutants and may cause pulmonary and/or atmospheric problems, and therefore reduction of nitrogen oxides is a common goal in the field of industrial combustion.

To this end, although emissions of nitrogen oxides are reduced as much as possible for environmental purposes and for energy efficiency purposes, different types of industrial burners have been developed to obtain the desired temperature inside the combustion chamber.

However, attempts to reduce emissions have determined a reduction in the gas flow rate used, thereby extending the time required to reach the desired flame temperature. In fact, in order to avoid temperature peaks that cause the greatest part of the emissions (when open in steady state), generally, with an increase in the air flow of the cooling flame, the power is reduced, thus reducing the NO _X Emission is produced.

In particular, the emission reduction is contrary to the requirements that need to be met in order to obtain a stable flame in order to reach the required temperature quickly, since the minimization of the fuel used jeopardizes the depth and stability of the so-called flame base.

It is an object of the present invention to provide an apparatus and a burner which are designed to at least partially overcome the drawbacks of the prior art and which are at the same time inexpensive and easy to manufacture.

Disclosure of Invention

According to the present invention there is provided an industrial burner and apparatus according to the appended independent claims, and preferably according to any one of the dependent claims directly or indirectly dependent on the independent claims.

The accompanying claims describe preferred embodiments of the invention and form a part of the specification.

Drawings

The invention will now be described with reference to the accompanying drawings, which show some non-limiting embodiments of the invention, in which:

FIG. 1 is a schematic cross-sectional side view of a first embodiment of an industrial burner according to the invention;

fig. 2 is a schematic perspective view of a second embodiment of an industrial burner according to the invention;

FIG. 3 is a cross-sectional side view of the portion of FIG. 2;

fig. 4 is a schematic perspective view of the cross-section of fig. 3; and

fig. 5 is a schematic front view of the burner of fig. 2 to 4.

Detailed Description

In fig. 1, numeral 1 generally designates an industrial burner with reduced emissions according to a first aspect of the invention.

The burner 1 may be installed (i.e. mountable) in a combustion chamber 3, for example a boiler or kiln, in particular in the region of a wall 4 of the combustion chamber 3. More particularly, the burner 1 can be installed (i.e. mountable) in an apparatus for firing enamels of ceramic articles, for baking enamels (booths painting), for drying sand and/or gravel, for precooking food products (e.g. deep-frozen products), in a heat generator using hot water, superheated water, steam, superheated steam with heat-permeable oil (hot oil boiler).

According to fig. 1, 3 and 4, the burner 1 comprises a tubular discharge element 5 inside which extends at least one duct 6 for a primary flow (primary flow) PF of fuel (for example natural gas or liquefied petroleum gas) configured to produce a flame base FR. In particular, in the region of the longitudinal (symmetry) axis LA of the burner, a flame root FR is formed in the radially central region of the burner 1.

In particular, the burner 1 comprises at least one duct 7 feeding a secondary fuel flow SF configured to generate a primary flame MF (radially external to the central flame root FR with respect to the longitudinal axis LA).

The burner 1 further comprises at least one duct 8 for supplying an oxidizing agent OX, typically ambient air. In particular, the fuel introduced through the fuel supply conduit 6 and the fuel supply conduit 7 is substantially methane, while the oxidant OX introduced through the oxidant OX supply channel 8 is substantially ambient air (with approximately 21% oxygen).

In the non-limiting embodiment of the figure, the tubular discharge element 5 is configured to be (fully) crossed by the oxidant OX and therefore by the conduit 8, in particular by the conduit 6 and conduit 7 feeding the primary fuel flow PF and the secondary fuel flow SF, respectively.

According to the non-limiting embodiment of fig. 1 and 3, the tubular discharge element 5 has an end 9, which end 9 is configured to be mounted outside the combustion chamber 3, and an end 10, which end 10 is opposite to the end 9 and is configured to be mounted inside the combustion chamber 3.

Advantageously, although not necessarily, the burner 1 also comprises a tubular discharge element 11 extending from the end 10 on the opposite side with respect to the end 9, i.e. towards the combustion chamber 3 (more precisely, the interior of the combustion chamber 3). In particular, the tubular discharge element 11 is configured to be at least partially crossed by the duct 6 and the duct 7. More particularly, the discharge element 11 is configured to be flown through by fluid flowing out from the tubular discharge element 5.

According to some non-limiting embodiments, the tubular discharge element 5 is coupled to a support element comprising a flange configured to fix the burner 1 to the wall 4 of the combustion chamber 3.

Advantageously, although not necessarily, the burner further comprises a suction element 12 configured to introduce at least a portion of the gas G present outside the burner 1 (i.e. inside the combustion chamber 3) into the tubular discharge element 11 and having at least one opening 13, the opening 13 being arranged between the tubular discharge element 5 and the tubular discharge element 11 and sucking the gas G present outside the burner 1 thanks to a low pressure zone generated in the region of the suction element 12. In particular, the opening 13 has an annular shape. In this way, suction of the dispersed gas G can be obtained. By doing so, it is also possible to use the oxygen remaining in the combustion chamber 3 and complete the combustion of those gases G, G' which are not completely combusted in the first passage inside the burner 1, i.e., the main combustion. In addition, the gases G, G' (assuming also the fact that they have a relatively high temperature) help to improve combustion efficiency. In addition, some of the gas G' is sucked back by the main flame MF due to the outflow speed of the mixture consisting of the secondary flow SF and the secondary fraction OX "(accelerated due to the constriction 20). The term "main combustion" refers to combustion of a combustor without recirculation of the gases G, G'.

In the non-limiting embodiment of the drawing, the burner 1 is configured to produce an acceleration of the (sole) oxidizing agent OX in the region of the suction element 12.

According to some non-limiting embodiments, the suction element 12 comprises in particular a venturi tube.

According to the non-limiting embodiment of the figures, the tubular discharge element 11 is connected to the tubular discharge element 5 in an integral manner and is substantially coaxial with the tubular discharge element 5. In other words, the longitudinal symmetry axis LA of the tubular discharge element 11 coincides with the longitudinal symmetry axis LA of the tubular discharge element 5.

Advantageously, although not necessarily, the tubular discharge element 11 is (entirely) located inside the combustion chamber 3.

According to the non-limiting embodiment of the figures, the burner 1 comprises a dividing element 14 for the oxidant OX, the dividing element 14 being configured to divide the oxidant OX (upstream of the opening 13 of the suction element 12) into a primary portion OX' to be mixed with said primary flow PF and a secondary portion OX to be mixed with said secondary flow SF.

In particular, the oxidant separating element 14 comprises a (yes) mixing head 15, which mixing head 15 accommodates the fuel supply conduit 6 internally. Specifically, the head 15 is in a radially central position with respect to the longitudinal axis LA of the burner. More precisely, the head 15 is partly inside the tubular discharge element 5 and partly inside the tubular discharge element 11.

Advantageously, although not necessarily, the burner 1 is configured to produce acceleration of the minor portion OX "and/or of the major portion OX'. In particular, the configuration of the oxidant separating element 14 in combination with the suction element 12 allows the burner 1 to produce an acceleration of the minor portion OX "(narrowing the channels of the minor portion OX") and a reduction of the speed of the major portion OX '(widening the channels of the major portion OX').

Advantageously, although not necessarily, the burner 1 comprises a diffuser terminal 16, which diffuser terminal 16 is fluidly connected to the fuel supply conduit 6 (for the main flow PF) and is configured to diffuse and swirl the main fuel flow PF. In particular, the diffuser terminal 16 splits and deflects the primary flow PF to create a stable and turbulent flame root FR. In detail, "stable flame" means a flame whose (oscillation) frequency falls within the range of 5-200Hz, preferably 10-100 Hz.

In particular, the diffuser terminal 16 is integrally formed with the tubular discharge element 5.

In some non-limiting examples, the tubular discharge element 11 is adjustable longitudinally (along the longitudinal axis LA) in order to widen or narrow the opening 13 of the suction element 12.

Alternatively or additionally, the diffuser terminal 16 may be adjusted longitudinally (along the longitudinal axis LA) so as to change the spacing of the oxidant OX (i.e., the manner and point of distribution of the burner) to the primary and secondary portions OX', OX ".

Advantageously, although not necessarily, the diffuser terminal 16 comprises a turbulence plate 17 (shown in all the embodiments of the figures, in particular in the front of fig. 5) arranged perpendicular to the longitudinal axis LA of the burner 1. In particular, the turbulence plate 17 comprises a plurality of through slits 18 and/or holes 19, the through slits 18 and/or holes 19 being configured to generate a turbulent motion of the main flow PF.

More precisely, the slits 18 are rectangular (oblong) openings extending in an inclined manner from the main surface of the turbulence plate 17, while the holes 19 are circular openings extending perpendicular to the main surface of the turbulence plate 17 and thus parallel to the longitudinal axis LA of the burner 1.

Advantageously, although not necessarily, and according to the non-limiting embodiment shown in fig. 1 to 4, the suction element 12 is arranged upstream of the flame root FR along the longitudinal axis LA of the burner 1. In other words, the flame root FR is produced downstream of the suction element 12.

In particular, the suction element 12 is arranged along the longitudinal axis LA between the flame root FR and the tubular discharge element 5. In other words, the main flow PF encounters the oxidizing agent OX (in particular OX') after passing through the tubular discharge element 5, i.e. inside the tubular discharge element 11.

In the non-limiting embodiment of fig. 1, 3 and 4, the suction element has at least one constriction 20 arranged in the region of the end 10.

In particular, the constriction is defined by an uninterrupted constriction of the tubular discharge element 5 or by an uninterrupted widening of the oxidant separating element 14.

Advantageously, although not necessarily, the constriction 20 has (at least) segments TT', tt″ having the shape of a truncated cone, delimited by a larger base and a smaller base.

According to a limiting embodiment, the tubular discharge element 11 has an open end 21 facing the suction element 12 and an open end 22 facing the combustion chamber interior.

In the non-limiting embodiment of fig. 1, 3 and 4, the constriction 20 comprises a segment TT 'having a truncated cone shape (consisting of a segment TT' having a truncated cone shape) extending radially in the flow direction FD towards the central longitudinal axis LA of the burner 1, in particular with its larger base coinciding with the end 10 of the tubular discharge element 5. Furthermore, the constriction 20 comprises a segment tt″ having a truncated cone shape, which extends radially from the central longitudinal axis LA of the burner 1 in the flow direction FD, in particular the larger and smaller bases thereof being determined by the geometry of the separating element 14 (i.e. the head 15) for the oxidizing agent OX.

Advantageously, although not necessarily, the segment TT "having a truncated cone shape is arranged radially external (radially RD, as shown in fig. 1 and 3) with respect to the segment TT" having a truncated cone shape.

Advantageously, although not necessarily, the frustoconical sections TT' and tt″ are at least partially staggered along the flow direction FD. In this way, the acceleration of the oxidizing agent OX is isolated. In particular, according to the non-limiting embodiment of fig. 1, 3 and 4, the frustoconical section TT' is arranged at least partially downstream in the flow direction FD with respect to the frustoconical section TT ".

Advantageously, although not necessarily, the duct 6 feeding the main fuel flow PF is arranged in a central position of the burner along the longitudinal axis LA of the burner 1. Furthermore, a conduit 7 (or a plurality of conduits 7) supplying the secondary fuel flow SF is arranged outside the conduit 6 in a concentric manner. In particular, the burner 1 comprises a plurality of ducts 7 (for example six in the embodiment of fig. 2 to 5), which are arranged radially with respect to the duct 6.

According to the non-limiting embodiment of the figures, said at least one duct 7 is arranged to cross a space S' extending between the tubular discharge element 5 and the separation element 14 for the oxidizing agent OX. In particular, the at least one conduit 7 is arranged to extend also at least partially through the space S comprised between the tubular discharge element 11 and the oxidant separating element 14.

Advantageously, although not necessarily, the discharge element 5 has a circular cross section, in particular a constant diameter.

Advantageously, although not necessarily, the discharge element 11 has a circular cross section, in particular a constant diameter.

Advantageously, although not necessarily, the ducts 6 and 7 have a circular cross section.

Advantageously, although not necessarily, the head 15 has a circular cross section, with an at least partially variable diameter.

In particular, in the region of the constriction 20, the cross section of the channel for the minor portion ox″ has a channel of less than two-thirds of the space S' and/or space s″. More particularly, in the region of the constriction 20, the cross section of the channel of the minor portion OX "has channels smaller than half of the space S' and/or space S". The more the channels in the region of the constriction 20 decrease with respect to the space S', the more the variation in the velocity of the oxidant fraction OX "increases, which in use mixes with the secondary flow SF for forming the main flame MF.

In some non-limiting cases, space S' is substantially equal to space S ". In other non-limiting cases, space S' is substantially larger or smaller than space S ".

Advantageously, although not necessarily, the diameter of the tubular discharge element 5 is smaller than the diameter of the tubular discharge element 11.

Advantageously, although not necessarily, and according to the non-limiting embodiment of fig. 1, 2 and 5, the burner 1 further comprises a fuel supply system 23 and a second fuel supply system 24, the fuel supply system 23 being configured to regulate the inflow of the primary flow PF inside the duct 6, the second fuel supply system 24 being configured to regulate the inflow of the secondary flow SF inside the duct 7 (or ducts 7).

In particular, supply system 23 and supply system 24 may be adjusted independently of each other. In this way, for example, based on the load of the burner 1, the primary flow PF can be changed, keeping the secondary flow SF constant, and vice versa.

According to some preferred but non-limiting embodiments, the burner 1 further comprises a supply system 25 for the oxidizing agent OX. In particular, the oxidant supply system 25 comprises at least one fan 26 (schematically shown in fig. 1) with a variable rotation speed, which fan 26 is controlled in its rotation by its own actuator system.

Advantageously, although not necessarily, the burner 1 comprises an electronic control unit 27, which electronic control unit 27 is configured to control (in a coordinated manner) the fuel supply system 23, the fuel supply system 24 and the supply system 25 for the oxidizing agent OX. In particular, the control unit 27 is configured to vary the ratio between the primary flow PF and the secondary flow SF according to the loading requested to the burner 1.

Advantageously, although not necessarily, the control unit 27 is configured to vary the primary flow PF between 5% and 50% of the total fuel produced by the sum of the primary flow PF and the secondary flow SF.

Advantageously, although not necessarily, the control unit 27 is configured to vary the secondary flow SF between 95% and 50% of the total fuel (resulting from the sum of the primary flow PF and the secondary flow SF).

According to some advantageous non-limiting embodiments, the control unit 27 is configured to minimize the inflow of the main flow PF, as long as the further reduction does not cause extinction of the main flame MF.

In the non-limiting embodiment of fig. 1 and 3, the burner 1 is configured such that the main flame MF is formed in a space of the combustion chamber 3 separate from the flame root FR.

In this way, a lower average flame temperature value can be achieved and thus thermal NO can be reduced _x Is a contribution of (a).

In some non-limiting cases, the supply system 23 and the supply system 24 each comprise a respective electric actuator device M, in particular for regulating a respective valve V, preferably a throttle valve. Specifically, the electric actuator system M is a stepping motor or a brushless motor.

According to a second aspect of the present invention, an industrial apparatus for heating a fluid is provided.

In particular, the apparatus comprises a combustion chamber 3 and a burner 1 according to the above description. Advantageously, the burner 1 is arranged such that the suction element 12 is placed inside the combustion chamber 3 and such that at least a portion of the gas G present inside the combustion chamber 3 flows through the tubular discharge element 11.

According to another aspect of the present invention, there is provided a method of controlling a burner 1, the method comprising the steps of: the electric actuator systems M are controlled separately to minimize the main flow PD for generating the flame roots FR.

In use, in the region of the turbulence plate, the burner 1 generates a first combustion mixture, in particular a flame root FR, from the main flow PF and the main oxidant fraction OX', the gases of which flow at least partly through the discharge element 11, which introduces the flame root FR into the combustion chamber 3. At the same time, the burner produces a secondary combustion mixture, in particular a main flame MF, from the secondary flow SF and the accelerated secondary oxidant fraction OX ", the gases of which flow at least partially through the discharge element 11, which discharge element 11 introduces the main flame root MF deeper into the combustion chamber 3 than the flame root.

The combustion products emitted by the burner 1 are not completely combusted when they first pass through the discharge element 11, but the combustion is increased (complete) due to the continuous recirculation of the gases G (present in the combustion chamber 3) through the suction element 12 in the discharge element 11. Furthermore, the combustion is further improved due to the high outflow velocity of the secondary stream SF and the mixture formed by the secondary oxidant fraction ox″ and the gas G, which gas G' is continuously returned to the space of the main flame MF.

In other words, the burner 1 burns the gases (fuel and oxidant) introduced by the pipes 6, 7 and 8 once with the gas G, G' recirculated from the inside of the combustion chamber 3 and burns them secondarily, since they are not completely burned (thus having residual oxygen), they are sucked by the suction element 12 or the main flame MF (separated from the flame base FR).

In particular, the constriction 20 of the suction element 12 determines an increase in the speed of the secondary oxidant fraction ox″ flowing out of the discharge element 5. The change in the oxidant velocity determines a zone of low gas pressure in the region of the opening 13 by means of the venturi effect. This low pressure zone in turn determines the suction of the gases G present in the chamber 3, thus allowing the use of these gases F for secondary combustion (in this case, the percentage of oxygen is still moderate-up to 10%).

In the non-limiting embodiment shown in the drawings, the suction element 12 determines an increase in turbulent motion within the combustion chamber 3. In addition, post combustion produces a further increase in heat exchange. As a result, the total heat exchange coefficient increases, and the temperature uniformity within the combustion chamber 3 is higher.

Furthermore, the independent regulation of the flows PF and SF limits the ineffective use of fuel, further improving the combustion efficiency and emissions (in particular NO) together with the suction element 12 _x ) Is reduced.

It is therefore evident that the device 1 according to the invention allows the user to obtain a greater temperature uniformity inside the combustion chamber 3, the average temperature of which is particularly low compared to the solutions of the prior art.

It should be noted that when using a burner according to the above description, the temperature peaks occurring in the vicinity of the exhaust ports of the burner 1 are (at least partially) flattened, thus determining a smaller emission.

Even if the above-described invention specifically refers to an exact application example, it should not be considered as being limited to said application example only, since the scope of protection thereof also covers all those variants, modifications or simplifications covered by the appended claims, for example different geometries of the head 15 and the suction element 12, different arrangements (in terms of positioning and alignment) of the ducts 6 and 7 inside the burner of the discharge elements 5 and 11, different supply systems, different types of diffuser terminals, etc.

The above-described apparatus and burner have a number of advantages.

First, the present invention significantly reduces the NOx and CO emissions from the burner 1 compared to standard burners due to a combination of factors. In particular, the invention allows a high fuel staging due to the arrangement of the pipes 6 and 7 and the independence of the feed systems 23 and 24. Thus, the classification determines the volumetric separation between the flame root FR and the main flame MF.

In addition, considering the geometry of the burner 1, an efficient oxidant staging can be achieved and can be easily installed to replace (retrofit) standard architectures.

Furthermore, the present invention results in a high burner power modulation ratio (the rotational speed of the fan 26 can be varied due to the electronic control of the oxidant supply system 25).

Finally, for the device and burner 1 according to the invention, in order to maintain a given temperature, the decrease in dispersion in the combustion chamber 3, the increase in combustion and the uniformity of the temperature, the independent control of the primary flow PF and of the secondary flow SF, determine the need to introduce a smaller quantity of gas (typically methane) into the burner 1, thus determining the savings in energy and raw materials given the same power and reduced emissions, compared to the solutions of the prior art.

Claims

1. An industrial burner (1) with reduced emissions, which can be installed in a combustion chamber (3);

the burner (1) comprises at least: a first tubular discharge element (5) having at least one first supply duct (6) inside thereof for supplying a primary fuel flow (PF) configured to form a flame base (FR); at least one second supply duct (7) for supplying a secondary fuel flow (SF) configured to generate a primary flame (MF); at least one third supply duct (8) for supplying an oxidizing agent (OX); the first tubular discharge element (5) is configured to be flowed through by the oxidizing agent (OX) and has a first end (9) and a second end (10), the first end (9) being configured to be mounted outside the combustion chamber (3), the second end (10) being opposite to the first end and being configured to be mounted inside the combustion chamber (3);

the burner (1) further comprises a second tubular discharge element (11) extending from the second end (10) on the opposite side with respect to the first end (9); and a suction element configured to let at least a portion of the gas (G) present outside the burner (1) flow into the second tubular discharge element (11) and comprising at least one opening (13) arranged between the first tubular discharge element and the second tubular discharge element (11) and sucking the gas (G) present outside the burner (1) thanks to a zone of low pressure created in the region of the suction element.

2. Burner (1) according to claim 1, the burner (1) being configured to produce an acceleration of the oxidizing agent (OX) in the region of the suction element.

3. Burner (1) according to any one of the preceding claims, comprising a dividing element (14) for the oxidizing agent (OX) configured to divide the oxidizing agent (OX) into a primary portion (OX') mixed with the Primary Flow (PF) and a secondary portion (OX ") mixed with the Secondary Flow (SF).

4. A burner (1) according to claim 3, the burner (1) being configured to produce an acceleration of the secondary portion (OX ") and/or the primary portion (OX'); in particular acceleration of the secondary fraction (OX ") and deceleration of the primary fraction (OX').

5. Burner (1) according to any one of the preceding claims, comprising a diffuser terminal (16), said diffuser terminal (16) being fluidly connected to said first conduit (6) for the supply of fuel and configured to diffuse said main fuel flow (PF) and cause its swirl, in particular said diffuser terminal (16) being integrally formed with a first tubular discharge element (5); in particular, the second tubular discharge element (11) is longitudinally adjustable to widen or narrow the at least one opening (13) of the suction element; in particular, the diffuser terminal (16) is longitudinally adjustable to vary the separation of the oxidizing agent (OX).

6. Burner (1) according to claim 5, wherein the diffuser terminal (16) comprises a turbulence disc (17) arranged perpendicular to the Longitudinal Axis (LA) of the burner (1); the turbulence plate (17) comprises a plurality of through slits (18) and/or holes (19), the through slits (18) and/or holes (19) being configured to generate a turbulent motion of the Primary Flow (PF).

7. Burner (1) according to any one of the preceding claims, wherein said second tubular discharge element (11) is connected to said first tubular discharge element (5) in an integral manner and is substantially coaxial with said first tubular discharge element (5).

8. Burner (1) according to any one of the preceding claims, wherein the suction element (12) has at least one constriction (20) arranged in the region of the second end, wherein the constriction (20) has at least one segment of truncated cone shape, which is delimited by a larger base and a smaller base; the second tubular discharge element (11) has a first open end (21) facing the suction element and a second open end (22) facing the interior of the combustion chamber (3).

9. Burner (1) according to claim 8, wherein the constriction (20) comprises a first segment (TT') with a truncated cone shape, which extends radially in the Flow Direction (FD) towards the central Longitudinal Axis (LA) of the burner (1), in particular with its larger base coinciding with the second end of the first tubular discharge element (5), and a second segment (TT ") with a truncated cone shape, which extends radially in the Flow Direction (FD) from the central Longitudinal Axis (LA) of the burner (1).

10. Burner (1) according to claim 9, wherein the first segment (TT') having a truncated cone shape is arranged radially outside with respect to the second segment (TT ") having a truncated cone shape.

11. Burner (1) according to claim 9 or 10, wherein a first section (TT') having a truncated cone shape and a second section (TT ") having a truncated cone shape are at least partially staggered along the Flow Direction (FD).

12. Burner (1) according to claim 11, wherein a first section (TT') having a truncated cone shape is arranged at least partially downstream of a second section (TT ") having a truncated cone shape along the Flow Direction (FD).

13. Burner (1) according to any one of the preceding claims, wherein a first supply duct (6) for supplying the main fuel flow (PF) is arranged in a central position along the longitudinal axis of the burner (1); and wherein a second supply conduit (7) for supplying the secondary fuel Stream (SF) is arranged in a concentric manner outside the first conduit (6); in particular, the burner (1) comprises a plurality of second ducts arranged radially with respect to the at least one first duct (6).

14. Burner (1) according to any one of claims 3 to 13, wherein said at least one second duct (7) is arranged through a first space (S') extending between said first tubular discharge element (5) and said separation element (14) for said oxidizing agent (OX); in particular, the at least one second conduit (7) is further arranged at least partially through a second space (S ") extending between the second tubular discharge element (11) and the separation element (14) for the oxidizing agent (OX).

15. Burner (1) according to any one of the preceding claims, wherein the suction element (12) is arranged upstream of the Flame Root (FR) along the longitudinal axis of the burner (1).

16. A burner according to any one of the preceding claims, comprising: at least one first fuel supply system (23) configured to regulate an inflow of a Primary Flow (PF) inside the first conduit (6), and a second fuel supply system (24) configured to regulate an inflow of a Secondary Flow (SF) inside the second conduit (7); the first supply system (23) and the second supply system (24) are adjustable independently of each other.

17. Burner (1) according to claim 16, comprising a supply system (25) for the oxidizing agent (OX); the supply system (25) for the oxidizing agent (OX) comprises at least one fan (26) with a variable rotational speed, the rotation of which is controlled by a first actuator system (23).

18. Burner (1) according to any one of claims 16 or 17, comprising an electronic control unit (27) configured to control, in use, the first fuel supply system (23), the second fuel supply system (24) and a supply system (25) for the oxidizing agent (OX).

19. Burner (1) according to claim 18, the electronic control unit (27) being configured to vary, in use, the ratio between the Primary Flow (PF) and the Secondary Flow (SF) according to the loading requested to the burner (1).

20. Burner (1) according to claim 19, wherein the control unit is configured to vary the Primary Flow (PF) between 5% and 50% of the total fuel produced by the sum of the Primary Flow (PF) and the secondary flow (PF).

21. Burner (1) according to claim 19 or 20, wherein the control unit is configured to vary the Secondary Flow (SF) between 95% and 50% of the total fuel produced by the sum of the Primary Flow (PF) and the Secondary Flow (SF).

22. Burner (1) according to any one of claims 18 to 21, wherein the control unit is configured to minimize the inflow of the main flow (PF), provided that the stability of the Main Flame (MF) is not impaired by further reduction.

23. The burner (1) according to any one of claims 16 to 21, configured such that the Main Flame (MF) is formed in a space of the combustion chamber (3) separate from a Flame Root (FR).

24. Burner (1) according to any one of claims 16 to 21, wherein the first supply system (23) and the second supply system (24) each comprise a respective electric actuator device (M); in particular, it is configured to regulate the respective valve (V), preferably a throttle valve.

25. Burner according to any one of claims 16 to 24, wherein the suction element (12) and the first (23) and second (24) supply systems cooperate to reduce the emissions of the burner (1).

26. A fluid heating device comprising a combustion chamber (3) and a burner (1) according to any of the preceding claims, wherein the burner (1) is arranged such that the suction element (12) is placed inside the combustion chamber (3) and at least a portion of the gas (G) present inside the combustion chamber (3) flows through the second tubular discharge element (11).