CN116906891A

CN116906891A - Burner and furnace-burner assembly

Info

Publication number: CN116906891A
Application number: CN202310391224.9A
Authority: CN
Inventors: 约纳斯·卡泰卢斯; 拉西·卡尔沃宁
Original assignee: Oilon Technology Oy
Current assignee: Oilon Technology Oy
Priority date: 2022-04-12
Filing date: 2023-04-12
Publication date: 2023-10-20
Also published as: EP4261457C0; EP4261457A1; FI130837B1; FI20225319A1; EP4261457B1

Abstract

A burner mountable to a furnace for combusting an air-fuel mixture and producing a flame in the furnace, the burner comprising a frame member provided with an elongated burner head protruding from the frame member and adapted to the interior of the furnace, the burner head comprising a larger diameter outer duct for combusting the mixture of air and fuel, and a smaller diameter inner duct for primary air and primary gas surrounded by the outer duct. The space bounded by the outer wall of the outer tube and the sleeve of the outer tube of the inner tube is configured as a discharge channel extending from the frame member to the distal end of the burner head. A flow controller is provided in the flow space for the primary air and at the distal end of the burner head, and a plurality of nozzles are provided in the inner tube of the inner tube and at the distal end of the inner tube in the flow direction of the primary gas. It also relates to a furnace-burner assembly for producing flames in a combustion chamber present in the inner side of the furnace.

Description

Burner and furnace-burner assembly

Technical Field

The present invention relates to a burner according to the preamble of claim 1, which can be installed in a furnace for burning a premixed air-fuel mixture.

The invention also relates to a furnace-burner assembly for burning a premixed air-fuel mixture according to claim 16.

Background

So-called premix burners are used for burning a mixture of premixed fuel and air. These burners are intended to achieve lower NOx emission levels. In particular, premix burners with long burner heads aimed at obtaining lower NOx emissions (NOx emissions lower than 9ppm in flue gas) without a large oxygen excess are disclosed in the prior art, i.e. in publication US-6,238,206. Such previously known burner models are provided with a burner head associated with the frame and extending a long distance to the interior of the furnace, low NOx emissions requiring an oxygen excess of less than 12%, in particular less than 6%. However, the biggest disadvantage of such burners is the relatively high NOx emission levels that persist, in other words, the lower oxygen excess that the burner is operating with, for example, certain states of the united states, do not fully meet stringent emission standards. Applicant's own U.S. application discloses such burners capable of achieving low emissions, however, such burners are limited in terms of compatibility with commercial furnaces.

Disclosure of Invention

The present invention aims to provide an improvement in, or at least alleviate, the disadvantages of the prior art described above. It is therefore a first object of the present invention to provide a high efficiency burner capable of being installed on a furnace and a furnace-burner assembly in which a premixed air-fuel mixture can be burned by the burner with an oxygen excess of less than 3% and an oxygen excess of less than 7%, with an oxygen excess of less than 3% maintaining an average NOx emission in the flue gas below 15ppm and an average NOx emission in the flue gas below 5 ppm. It is a particular object of the invention to achieve NOx levels below 2.5ppm with oxygen surplus below 8% by means of flame stabilization and staged mixing ratios.

A second object of the present invention is to provide a burner that can be more easily mounted to a commercial furnace and a furnace-burner assembly thus obtained.

The above object is achieved by a burner according to claim 1, which can be mounted to a furnace for combusting a premixed air-fuel mixture, and a furnace-burner assembly according to claim 16 for combusting the air-fuel mixture and generating a flame in a combustion chamber inside the furnace.

More particularly, the present invention relates to a burner mountable to a furnace for burning an air-fuel mixture and generating a flame in the furnace according to claim 1. The burner comprises a frame member provided with an elongated burner head protruding from said frame member and being adapted to the interior of the furnace, the distal end of said burner head being adapted to produce both a main flame and a primary flame, as seen from the frame member of the burner, said burner head comprising an outer duct of larger diameter for burning a mixture of air and fuel, and an inner duct of smaller diameter for primary air and primary gas surrounded by the outer duct. Thus, the inner conduit of the burner head extends from the frame member of the burner to the distal end and comprises an inner tube for primary gas and an outer tube surrounding said inner tube, wherein a flow space for primary air is provided between the outer side of the sleeve of said inner tube and the inner side of the sleeve of the outer tube, the outer conduit of the burner head extends from the frame member of the burner to the distal end of the burner head and may be provided with a supply of pre-mixed air-fuel mixture from the frame member of the burner or from a portion of the burner head associated with the frame member and located upstream in the flow direction of the pre-mixed air-fuel mixture of the combustion chamber for generating the main flame (B).

The space between the outer wall of the outer tube and the sleeve of the outer tube of the inner tube is configured to: a discharge channel extending from the frame member to a distal end of the burner head, wherein the discharge end of the discharge channel is turned away from a longitudinal centre line of the burner head such that the centre line of the discharge end or an extension thereof forms an oblique angle of incidence with the longitudinal centre line of the burner head, the angle of incidence being 90 to 140 degrees when the discharge end of the discharge channel is seen from the frame member direction of the burner.

A flow controller is provided in the flow space for the primary air and at the distal end for guiding the flow of the primary air in the flow space such that the primary air flows from the flow guide towards the mouth of the flow space in the vicinity of the sleeve of the outer tube of the inner channel,

a plurality of nozzles are provided in the inner tube of the inner passage and at the distal end of the inner tube in the flow direction of the primary gas for guiding the primary gas into the flow space upstream or downstream of the flow controller in the flow direction of the primary gas.

In the furnace-burner assembly for burning an air-fuel mixture and generating a flame in a combustion chamber inside the furnace of the present invention,

The burner has been defined in claim 1 and is connected to the furnace such that: a second portion of the elongated burner head protruding from the frame member is provided inside the combustion chamber of the furnace and a first portion of the burner head is provided outside the furnace or is connected to the structure of the furnace. The main flame may be generated by guiding a premixed air-fuel mixture into the discharge channel, the fuel-air mixture being discharged into the furnace from a mouth of the discharge channel at an angle of 90 to 140 degrees when the mouth of the discharge channel is viewed from a direction passing through a center line of an end of the discharge channel on one side of the frame of the burner.

The main flame (B) can be produced by:

by guiding the premixed air-fuel mixture into the discharge channel, the fuel-air mixture is discharged from the mouth of the discharge end of the discharge channel to the combustion chamber, the center line of the discharge end forming an oblique angle of incidence with the longitudinal center line of the combustion head and the longitudinal center line of the discharge channel, the angle of incidence being about 90 degrees to 140 degrees when the discharge end of the discharge channel is viewed from the frame member direction of the burner.

The primary flame (E) can be generated by:

by providing a supply of primary air from a frame member of the burner or from a portion of the combustion head associated with the frame member upstream of the combustion chamber in the direction of flow of primary air to the flow space for delivering a flow of primary air to a flow controller adapted to direct the flow of primary air in a co-current manner with the main flame for delivery towards the mouth of the flow space, and

by providing the inner tube of the inner duct with a frame member from the burner, or with a supply of primary gas from the burner head upstream of the combustion chamber in the direction of primary air flow, wherein the nozzles of the plurality of nozzles located near the free end of the inner tube are adapted to direct primary gas from the mouth of the burner head out of the duct flow space.

The invention is based on a burner head consisting of two nested tubes. The premixed air-gas mixture passes through an external conduit, i.e. an exhaust passage, thereby discharging the premixed air-gas mixture from the exhaust end of the exhaust passage into the combustion chamber, which narrows and turns when viewed from the centerline of the combustion head. The cross-sectional area of the discharge passage gradually decreases in the advancing direction of the air-gas mixture while advancing toward the mouth of the discharge end portion, which is located at the mouth of the combustion head.

The cross-section of the discharge channel is continuously reduced so as to be minimized at the mouth of the discharge channel. This has the advantage that the premixed air-gas mixture (main flow) is continuously accelerated in the discharge channel. Thus, the main flow reaches a maximum flow rate at the mouth of the discharge channel.

Primary air and primary gas flow in the inner duct. Primary air is directed through a flow controller, such as a vane, co-directionally with the main flame toward the mouth of the burner head. The flow controller directs the primary air from the flow controller toward a mouth of the flow space near the sleeve of the outer tube of the inner conduit. In this way, the path of the primary air from the flow controller flow toward the mouth of the flow space may be directed away from the centerline of the combustion head following the curvature of the inner wall of the discharge passage.

The primary gas travels within its own tube in the inner conduit and is directed through the nozzle towards the mouth of the burner head.

In the burner, the intensity of the flame and the amount of air are adjusted, and the adjustment is accurate and has a strong influence on the main flame. It is due to the good adjustability that the burner is better compatible with various applications and combustion chambers than before. In particular, the burner is more compatible with water tube boilers and other special applications than before.

It is due to the more reliable regulation that the new burner is able to maintain an emission limit of 5ppm and acceptable stability in a combustion chamber that is more diversified than before. In addition, the novel concept enables NOx levels of less than 2.5ppm and oxygen excesses of less than 8% due to further optimization of the phasing of flame stability and mixing ratios (see also Table 1). It is the innovative burner design that minimizes the risk of flashback typical to premixed burners, thereby improving safety and convenience of use.

Drawings

The invention and the advantages that can be obtained will be described in more detail below with reference to the drawings.

FIG. 1 illustrates in cross-section a frame member of one burner embodiment and a combustion head associated therewith.

Fig. 2A shows an embodiment of a flow controller at the burner head of a burner according to the invention in an oblique front view.

Fig. 2B shows, also in an oblique front view, another embodiment of a flow controller at the burner head of a burner according to the invention.

Fig. 2C shows a further embodiment of a flow controller at the burner head of a burner according to the invention in an oblique front view.

Detailed Description

A brief review of some aspects of the burner and furnace burner assembly of the present invention, which are illustrated in detail in fig. 1, 2A, 2B and 2C, follows.

Fig. 1 shows a burner 1 in a longitudinal section, the burner head 2 of the burner 1 extending into a furnace 9. The combustion head 2 is generally cylindrical and has a circular cross-sectional profile. Fig. 1 also shows how a flame A, B, C, D, E is generated in the burner assembly by burning an air-fuel mixture 80 (generating a main flame B) or primary air 60 or primary gas 70 (generating a primary flame E) directed to the mouth 23 of the burner head, flame A, B, C, D, E being formed within the furnace. Fig. 1 shows the direction of advance of the air-fuel mixture 80, the primary air 60 and the primary gas 70 in the combustion head 2 with arrows.

The burner 1 in fig. 1 is installed in a furnace 9 such that: the mouth 23 of the burner head 2 opens into the interior 90 of the furnace 9 and the frame member 6 of the burner is attached to the furnace 9 by means of a flange 91.

The elongated burner head 2 of the burner 1 protrudes from the frame member 6 and has generated in the interior 90 of the furnace 9 a main flame B and a primary flame E, which are located downstream of the mouth 23, the mouth 23 being the distal end 2a of the burner head 2, seen from said frame member 6. The accumulation of other flame regions (A, C, D) will be described later.

The burner head 2 comprises an outer conduit 3 of larger diameter for burning a mixture 80 of air and fuel and an inner conduit 4 of smaller diameter surrounded by the outer conduit 3, said inner conduit 4 being for primary air 60 and for primary gas 70.

The inner duct 4 of the burner head 2, which is surrounded by the outer duct 3 of the burner head 2, has been provided with a supply of primary gas 70 and primary air 60. The inner conduit 4 of the burner extends from the frame member 6 of the burner up to the mouth 23 of the distal end 2a of the burner head 2.

The inner conduit 4 of the burner head 2 comprises an inner tube 4;41 and an outer tube 4;42, inner tube 4;41 for a gaseous fuel (primary gas) 70. An outer tube 4;42 surrounding the inner tube 4;41. an outer surface 41a of the sleeve 40 of the inner tube 41 (i.e., the side of the sleeve 41 of the inner tube 4 facing the outer tube 4; 42) is in contact with the outer tube 4; the inner surface 42a of the sleeve of 42 (i.e. the side of the sleeve 40 of the outer tube facing the inner tube) leaves a flow space 4 for primary air 60 between them; 43. a flow space 4;43 are thus guided in the direction of the outer pipe 3 by the outer pipe 4 of the inner pipe 4;42 such that the outer tube 4 of the inner tube 4 is constrained by the sleeve-like member of 42; 42 become the inner wall of the outer pipe 3.

The mouth 23 of the burner head 2 is divided into a discharge end 10a of the discharge channel 10 and a combined mouth 43a for the flow space 43, wherein the primary gas 70 flows via the inner tube 41 and the primary air 60 flows via the flow space 43.

The free end of the discharge channel 10 facing the mouth 23 of the burner head 2 comprises a discharge end 10a, the mouth of the discharge end 10a opening into the mouth 23 of the distal end 2a of the burner head 2. The discharge passage 10 will be described in more detail below.

The mouth 43a of the flow space 43 of the inner passage 4 is restricted by the discharge end 10a of the discharge passage 10, in particular, by the distal end of the sleeve 42a of the outer tube 42, as viewed from the center line of the burner head, i.e., in the radial direction of the burner head 2.

The flow controller 7 is mounted at the mouth 43a of the flow space 43 of the inner duct 4, the flow controller 7 being located at the free end of the flow space as seen from the frame member 6 of the burner 1, and the flow controller 7 constituting a part of the mouth 23 of the distal end 2a of the burner head. Thus, the flow controller 7 is located at the distal end 2a of the burner head 2, close to the mouth 23 of the burner head, as seen from the frame member 6 of the burner.

A flow space 4 for primary air 60; 43 extend from the frame member 6 of the burner 1 to the mouth 23, said mouth 23 being the distal end 2a of the burner head 2 (seen from the frame member 6). An outer tube 4; the sleeve 42a of 42 simultaneously constitutes the boundary surface between the inner conduit 4 and the outer conduit 3.

As described above, the outer tube 4 of the inner tube 4; the sleeve 42a of 42 also separates the discharge end 10a of the discharge channel 10 and the mouth 43a of the flow space 43 from each other at the mouth 23 of the burner head 2.

The outer end 42A, i.e. the free end 42A, of the outer tube 42 of the inner duct 4 is arranged to turn outwards, seen from the frame member 6 of the burner 1, i.e. in the direction of the free end 31A of the outer wall 31 of the outer duct 3 seen from the longitudinal centre line of the burner head 2. The center of the radius of curvature is located outside the burner head 2.

As can be seen in fig. 1, the sleeve 42 of the outer tube 42 of the inner conduit 4, which delimits the flow space 43, extends substantially parallel to the centre line P of the burner's burner head 2 up to the flow controller 7 located in the flow space 43 of the inner conduit. The distal end 42A, i.e. the free end 42A, of the sleeve 42A of the outer tube 42 of the inner duct 4 extending downstream of the flow controller 7 in the flow direction of the primary air 60 is turned away from the centre line P of the burner head 2 towards the outer wall 31 of the outer duct 3. In this way, the distal end 42A of the outer tube 42 of the inner tube 4 is directed away from the centerline P of the burner head 2 in the radial direction of the burner head 2.

More precisely, said free end 42A of the outer wall of the sleeve 42A of the outer tube 42 of the inner duct is positioned on a circular arc of radius R1, the centre of which is positioned outside the burner head 2.

In this case, the distal end 42A or the free end 42A of the outer tube 42 of the inner tube 4 refers to a portion of the outer tube 42 that is located at the outer end 2A of the burner head 2, as seen from the frame member 6 of the burner, which is located substantially downstream of the flow controller 7.

As the primary air 60 leaves the flow space 43, the flow controller 7 directs the flow of the primary air 60 in the flow space 43 in the same direction as the main flame B. The structure and function of the flow controller 7 is shown in more detail in fig. 2A-2C below.

The outer conduit 3 of the burner in turn extends from the frame member of the burner 1 to the mouth 23 of the distal end 2a of the burner 2. The outer wall 31 of the outer conduit 3 at the same time constitutes the outer wall of the burner head 2. The free end 3A of the outer duct 3, i.e. the free end 31A of the outer wall of the outer duct, turns outwards with a radius of curvature R, seen from the centre line 10L of the discharge channel 10, i.e. the free end 3A of the outer duct 3 turns away with a radius of curvature R, seen from the centre line P of the burner (see fig. 1). The center of the radius of curvature R is also preferably located outside the combustion head 2.

The remaining space between the inner side 30 of the outer wall 31 of the outer duct 3 and the outer side of the sleeve 42 of the inner duct 42 constitutes a discharge channel 10 in which a premixed air-fuel mixture 80 for generating the main flame B travels. The sleeve 42A of the outer tube defines the inner tube 4, thereby simultaneously acting as an outer wall of the inner tube 4. The discharge channel 10 has its free end closer to the mouth 23 of the burner head 2, including the discharge end 10a, the mouth of which is part of the mouth 23 of the distal end 2a of the burner head 2.

Therefore, when the burner head is viewed from the direction of the frame member 6, the distal end 42A of the sleeve 42A of the outer tube 42 of the inner duct 4, which is the inner surface of the discharge end 10a of the discharge passage 10, and the outer wall 31 of the outer duct 3, which is the outer surface of the discharge end 10a of the discharge passage 10, are turned toward each other while being away from the center line P of the burner head. Therefore, the combustion end portion 10a has a trumpet-like appearance at the mouth 23 of the combustion head 2, and the cross section of the discharge end portion 10a of the discharge passage 10 is continuously reduced, and the minimum is reached at the mouth of the discharge passage 10.

This provides the following benefits: the premixed air-gas mixture (main flow) is continuously accelerated at the discharge end 10a of the discharge channel. Thus, the maximum flow rate of the main flow is achieved at the mouth of the discharge end portion 10 a.

As described above, the outer wall 31 of the discharge channel 10 and the free ends 31A and 42A of the inner wall of the discharge channel, i.e. the free ends of the sleeve 42A of the outer tube 42, have an overall appearance of "flares" at the distal end 2A of the burner head 2. Accordingly, the respective free ends 31A and 42A of the outer wall 31 of the discharge channel 10 and the inner wall 42A of the discharge channel are curved outwardly from the center line 10L of the discharge channel and the center line P of the burner head with radii of curvature R and R1, respectively, wherein R and R1 are equal or unequal. The centers of these radii R and R1 are located outside the burner head.

In a preferred embodiment of the invention, the centre of the radii of curvature R and R1, seen from the frame member 6 of the burner, is located on one side of such a cross-sectional plane of the centre line P of the burner head and faces the mouth 23 of the burner head 2, which mouth 23 extends substantially via the flow controller 7 at the distal end of the burner head 2.

Since the free end 31A of the outer wall 31 of the discharge channel 10 and the free end 42A of the inner wall 42A of the discharge channel are respectively curved outwardly as viewed from the center line 10L of the discharge channel 10a and from the center line P of the combustion head 2, the entire discharge end 10a is directed away as viewed from the center line P of the combustion head.

Since the discharge passage 10a itself is annular, the center line 10L of the discharge passage refers herein to the annular center line 10L of the annular discharge passage 10a as viewed in the longitudinal section of the discharge passage (refer to fig. 1). Therefore, the angle of attack between the center line 10L (in the longitudinal section of the discharge end portion) of the discharge end portion 10a of the discharge passage 10 and the longitudinal center line P of the combustion head 2 is the inclined angle of attack t. The same oblique incident angle 5 is also formed between the center line 10A of the discharge end portion 10A and the center line 10L of the discharge passage 10 (its longitudinal section). The oblique angle of incidence t is about 90-140 degrees when the angle of incidence 5 between the centre line 10A of the discharge end and the longitudinal centre line P of the burner head and the discharge end 10A of the discharge channel 10 are seen from the direction of the frame member 6 of the burner 1.

In general, the free end 42a of the inner wall 42 of the discharge channel 10 having the radius of curvature R1 (the free end 42a of the outer tube 42) arches more strongly than the free end 31a of the outer wall 31 of the discharge channel 10 having the radius of curvature R, whereby R > R1. Thus, when advancing toward the mouth of the discharge end portion 10a of the discharge passage 10, which is a part of the mouth 23 of the combustion head (refer to fig. 1), in the traveling direction of the premixed air-gas mixture 80, the entire discharge end portion 10a of the discharge passage 10 becomes narrower and turns outward. Thus, the cross-sectional area of the discharge end 10a of the discharge channel 10 decreases in the traveling direction of the premixed air-gas mixture 80 as it proceeds toward the mouth of the discharge end 10a located at the mouth 23 of the combustion head 2.

This causes the flow rate of the premixed air-gas mixture 80 flowing in the discharge passage to be continuously accelerated as it passes toward the mouth of the discharge end 10 a. The flow rate and the magnitude of its acceleration will depend on the relationship between the inclination angle 5 between the centre line 10A of the discharge channel and the longitudinal centre line P of the burner head and the radii of curvature R and R1.

It is the novel design of the discharge end 10a of the discharge channel 10 that minimizes the risk of flashback of a typical premix burner, thereby improving safety and convenience of use.

The discharge channel 10 of the outer duct 3 is provided with a supply of a premixed air-fuel mixture 80 for generating a main flame B visible in fig. 1. The premixed air-fuel mixture 80 reaches the discharge passage 10 of the outer duct 3 from the frame member 6 or from a portion 2b of the combustion head 2 associated with the frame member and located upstream of the combustion chamber 90 in the flow direction of the premixed air-fuel mixture.

In the flow direction of the primary gas 70 is the inner conduit 4;41, which in turn is provided with a distal end 41a for introducing a primary gas 70 into the flow space 4;43, a plurality of nozzles 8. The primary gas is conveyed into the flow space in the flow direction of the primary air 60 upstream or downstream of the flow diverter 7 at the free end 43 of the flow space 43. An inner tube 4 of the inner tube 4;41 are provided with primary gas 70 from the frame member 6 of the burner 1 or from the portion 2b of the burner head 2 associated with the frame member and located upstream of the combustion chamber 90 in the flow direction of the primary gas 70.

When the flows of the primary air 60 and the primary gas 70 introduced into the flow space 43 are combined with each other after the mouth of the flow end portion of the flow space 43, a primary flame E is generated. The flow space mouth is part of the mouth 23 of the burner head 2.

Fig. 2A, 2B and 2C show structural and functional options of the flow controller 7 installed in the flow space 43 of the inner tube of the burner of the present invention in a view from a front oblique view. The flow of primary air 60 to the flow controller 8 and from the inner tube 4 is further depicted in each figure; 41 to the same flow space 43; 701.

As shown in fig. 1, the flow of primary air 60 is adapted to flow from the frame member 6 of the burner into the flow space 43 and further through the flow controller 7.

The flow controller 7 for guiding the primary air 60 may have different designs and shapes, however, the most important aspect is that the flow of primary air 6 from the flow space 43 to the flow controller 7 is guided to the main flame B by the flow controller 7. The main flame is generated by the air-fuel mixture 80 flowing in the discharge passage 10.

For example, as shown in fig. 2A, a flow controller 7;7a may comprise a plurality of lobes 7 ¹ 、7 ² 、7 ³ …7 ⁿ . A flow controller 7;7a leaf-shaped part 7 ¹ 、7 ² 、7 ³ …7 ⁿ Is installed to surround the inner tube 4 in an equidistant manner from the free end 41A of the inner tube 41; 41. relative to passing through two adjacent lobes (e.g. 7 ¹ And 7 ² Or 7 ² And 7 ³ ) The flow of primary air 60 in between, each leaf 7 ¹ 、7 ² 、7 ³ …7 ⁿ Is adapted such that: downstream of the lobes 7, the flow of primary air 60 is directed towards the mouth 23 of the flow space 43 and simultaneously towards the mouth of the burner head 2 in a co-current manner with the main flame B. Preferably, the flow of primary air 60 is directed by the action of the flow controller 7 to the vicinity of the inner surface of the outer tube 4, 42.

Leaf-shaped part 7 ¹ 、7 ² 、7 ³ …7 ⁿ The flow direction 60 relative to the primary air 60 in the flow space 43 is at least in a partially cross-orientation. PreferablyLeaf-shaped part 7 ¹ 、7 ² 、7 ³ …7 ⁿ At an angle of 20 to 90 degrees relative to the direction of flow of primary air 60.

In fig. 2B, the flow controller 7;7b comprise a single circular disc surrounding the inner tube 41, and the plane of the disc is in a transverse direction with respect to the longitudinal direction of the inner tube 41. The disc comprises grooves spaced apart from each other in the radial direction of the disc, whereby the volume of the flow of primary air 60 reaching the bottom surface of the disc will be directed from the grooves to the mouth 23 of the flow space 43 in a co-current manner with the main flame B.

Fig. 2C shows a further embodiment of the flow controller 7C. A flow controller 7;7c comprise a single circular disc surrounding the inner tube 41, and the plane of the disc is in a transverse direction with respect to the longitudinal direction of the inner tube 41. The flow of primary air 60 reaching the bottom surface of the disk bypasses the disk and is directed towards the mouth 23 of the flow space 43 in a manner that is co-directional with the main flame B.

Next, some important details of the present invention are further reviewed with reference to the previous descriptions of fig. 1, 2A, 2B, 2C.

A flow space 4;43 increases as it progresses towards the mouth 23 of the burner head 2, because the free end 42A of the sleeve 42 of the outer tube is bent away, as seen from the centre line P of the burner head 2.

It is by virtue of the reliable main flame B regulation that the burner is enabled to reach an emission limit of 5ppm in a number of combustion chambers that were previously difficult to control, with acceptable stability. In addition to this, with further optimized flame stability and phasing of the mixing ratio, the new concept enables the NOx level in the combustion chamber to be reached<2.5ppm(O ₂ Reference value 3%).

In order to produce the primary flame E, the amount of primary air 60 supplied is 5% to 30% of the total amount of air delivered to the burner head 2, and the adjustment of the relative amounts and flow rates of primary air 60 and primary gas 70 enables the intensity of the primary flame E to be controlled with precision. This provides a major contribution to the intensity and stability of the main flame B. Preferably, the amount of primary air 60 supplied for generating the primary flame E is about 20% of the total amount of air used for generating the main flame B by the premixed air-gas mixture 80 and for generating the primary flame E by the primary air 60.

All of the premixed air and fuel is delivered to the location of the main flame B or to zone B in fig. 1. Most of the combustion occurs in this area. The primary flame E is generated at the mouth 23 of the burner head, the intensity and the air quantity of which can be adjusted so that the temperature of the flue gas flowing into the zone B of the main flame is different. In this way, the burner 1 stability and emissions can be optimized for various applications and combustion chambers. By virtue of the good adjustability, the burner is better compatible with various applications and combustion chambers than before. In particular, the burner is more compatible with water tube boilers and other special applications than before.

As seen in fig. 1, some combustion also occurs in the a flame zone, with fuel and air eventually entering the a flame zone from the B zone of the main flame. The flue gas circulates in zone a while cooling. The flue gas cooled in zone a eventually returns to zone B while reducing the main flame temperature and reducing the NOx emissions from the burner. Some of the partially cooled flue gas also flows from region C of flame C into zone B of the main flame, which both dilutes and cools zone B, thereby cooling the temperature profile of the flame, thereby reducing NOx emissions from the burner.

There is a strong backflow in front of the mouth 23 of the burner head 2. The flue gas is discharged from the main flame zone B along the wall of the furnace 9 while being cooled, and a portion of the flue gas is returned in the form of a return flow D-C through the middle section of the combustion chamber 9. The reflux D-C both cools and dilutes zone B of the main flame build up. In zone D of the flame, there is no significant back flow at the end of the combustion chamber 90, but some complete combustion of carbon monoxide still occurs.

In the burner-furnace combination according to the invention, the flame becomes very different due to the radial direction of the fluid compared to competing technologies. The flame becomes compact (wide and short), but still very bulky. Increasing the diameter of the flame has a greater effect on the volume of the flame than increasing the length. (barrel volume = PI (D/2)/(2)).

Because of the shape of the flame, the backflow (a and D) dilutes and cools the flame more effectively than competing technologies. These differences provide the following advantages: the flame is cooled and thus the NOx emissions are low.

If the burner is used with a high excess of air, a smaller excess of air is sufficient to achieve the desired NOx emissions. If the burner is used in combination with external flue gas recirculation (flue gas recirculation, FGR), a smaller amount of recirculated flue gas is sufficient. Furthermore, a shorter flame is advantageous in many applications, as a shorter furnace is sufficient.

With the exemplary burner-furnace combination according to the invention, low Nox values are achieved due to the design of the burner head and the shape of the resulting flame. Table 1 gives the NOx emissions [ dry, mol-% ] produced from the flue gas of the furnace in accordance with the excess oxygen.

Table 1:

excess of oxygen

O ₂ [ Dry mol-%]	NOx [ ppm, dry, O ₂ ＝3％]
		6	＜9
7	<5
		8	＜2.5

Reference numerals of main parts

Burner 1

Burner head 2

Distal end 2a

The portion 2b of the combustion head upstream of the combustion chamber

Mouth 23

External pipe 3

Free end 3A

Outer wall 31

Interior 30

Free end 31A

Inner pipe 4

Inner tube 41

Sleeve 41a

Outer wall 40

Outer tube 42

Free end 42A

Sleeve 42a

Flow space 43

Free end 43a

Frame member 6 of the burner

Flow controller 7

Leaf-shaped part 7 ¹ , 7 ² , 7 ³ ..7 ⁿ

Nozzle 8

Furnace 9

Internal combustion chamber 90

Flange 91 for junction between furnace and burner

Discharge channel 10

Discharge end 10a

Primary air 60

Primary air 602 discharged from the mouth

Primary gas 70

Primary gas 701 discharged into a flow space

Premixed air-fuel mixture 80

Reverse flame A

Main flame B

Side flame C immediately behind primary flame

Farther apart side flames D behind the primary flame

Primary flame E

Longitudinal centerline P of burner

Radius of curvature R for the free end of an outer pipe

Radius of curvature R1 for the free end of an outer tube

Center line 10L of discharge passage

A centerline 10A of the discharge end.

Claims

1. A burner (1) mountable to a furnace (9) for combusting an air-fuel mixture and for generating a flame in the furnace (9), the burner (1) comprising a frame member (6), the frame member (6) being provided with an elongated combustion head (2) protruding from the frame member (6) and being adaptable to the interior of the furnace (9), a distal end (2 a) of the combustion head (2) being adaptable to generate both a main flame (B) and a primary flame (E) as seen from the frame member (6) of the burner (1), the combustion head (2) comprising: an outer pipe (3) of larger diameter for a mixture (80) of combustion air and fuel, and an inner pipe (4) of smaller diameter for primary air (60) and primary gas (70) surrounded by the outer pipe (3), whereby,

The inner duct (4) extends from the frame member (6) to the distal end (2 a) of the burner, and the inner duct (4) comprises an inner tube (4; 41) for primary gas (70) and an outer tube (4; 42) surrounding the inner tube (4; 41), wherein a flow space (4; 43) for primary air (60) is provided between the outside of the sleeve (41 a) of the inner tube and the inside of the sleeve of the outer tube, and an outer duct (3) of the burner head (2) extends from the frame member (6) to the distal end (2 a) of the burner head, and the outer duct (3) of the burner head (2) can be provided with a supply of pre-mixed air-fuel mixture (80) from: the feed coming from the frame member (6) of the burner, or from a portion of the combustion head (2) associated with the frame member and located upstream of a combustion chamber (90) in the flow direction of the premixed air-fuel mixture (80), for generating the main flame (B),

it is characterized in that the method comprises the steps of,

the space delimited by the outer wall (31) of the outer pipe (3) and the sleeve of the outer pipe (42) of the inner pipe (4) is configured to: -a discharge channel (10) extending from the frame member (6) to the distal end (2 a) of the burner head (2), wherein the discharge end (10A) of the discharge channel turns away from a longitudinal centre line (P) of the burner head (2) such that the centre line (10A) of the discharge end (10A) or an extension of the discharge end (10A) forms an oblique angle of incidence (t) with the longitudinal centre line (P) of the burner head (2), which angle of incidence (t) is 90 to 140 degrees in case the discharge end (10A) of the discharge channel (10) is seen from the direction of the frame member (6) of the burner (1),

A flow controller (7) is provided in the flow space (4; 43) for primary air and at the distal end of the combustion head (2) for guiding a flow of primary air (60) in the flow space (43) such that the primary air (60) flows from the flow controller (7) towards a mouth (43 a) of the flow space (43) in the vicinity of the sleeve (42 a) of an outer tube (4; 42) of the inner channel (4),

a plurality of nozzles (8) are provided in the inner tube (4; 41) of the inner tube (4) and at a distal end (41 a) of the inner tube (4) in the flow direction of the primary gas (70) for guiding the primary gas (70) into the flow space (4; 43) upstream or downstream of the flow controller (7) in the flow direction of the primary air (60).

2. Burner (2) according to claim 1, characterized in that the outer wall (31) of the outer duct (3) as outer wall (10 d) of the discharge channel (10) is simultaneously turned outwards from the longitudinal centre line (P) of the burner head (2) at the discharge end (10 a) when the outer wall (10 d) of the discharge channel (10) is viewed from the direction of the frame member (6) of the burner.

3. Burner (2) according to claim 1 or 2, characterized in that the inner wall (10 c) of the discharge channel (10) as the outer tube of the inner duct (4) is simultaneously turned outwards from the longitudinal centre line (P) of the burner head (2) at the discharge end (10 a) when the inner wall of the discharge channel (10) or the sleeve of the outer tube (42 a) is viewed from the direction of the frame member (6) of the burner.

4. Burner according to claim 1, characterized in that the mouth (23) of the burner head (2) comprises the mouth (10 a) of the discharge channel (10) and the mouth (43 a) of the flow space (43).

5. Burner (2) according to claim 1, wherein the flow controller (7) comprises a plurality of lobes (7 ¹ 、7 ² 、7 ³ …7 ⁿ ) The surface area and orientation of the lobes relative to the flow of primary air (60) through between the lobes are adapted such that: the flow of primary air (60) is directed downstream of the lobes towards the mouth of the flow space (43) and discharged into the combustion chamber (90) in the same direction as the main flame (B).

6. Burner according to claim 1, wherein the flow controller (7) is composed of a circular-shaped disk surrounding the inner tube (4; 41), the plane of the disk being oriented transversely with respect to the longitudinal direction of the inner tube (4; 41).

7. Burner (1) according to any of the preceding claims, wherein the flow controller (7) comprises a disk or a leaf (7 ¹ 、7 ² 、7 ³ …7 ⁿ ) The disc or leaf is mounted to: surrounding the inner tube (41) of the inner tube (4) at an equal distance from the free end (41A) of the inner tube (4), the disc or the leaf (7) ¹ 、7 ² 、7 ³ …7 ⁿ ) At least partially oriented with respect to the flow direction of the primary air (60).

8. Burner (1) according to claim 6, characterized in that the lobes (7 ¹ 、7 ² 、7 ³ …7 ⁿ ) Relative to the placeThe flow direction of the primary air (60) is at an angle of 20 degrees to 90 degrees.

9. Burner (1) according to any one of the preceding claims, wherein the flow space (4; 43) increases in the direction of the mouth (43 a) of the flow space (43), the mouth (43 a) of the flow space (43) being surrounded by the inner wall of the discharge channel (10) at the discharge end (10 a).

10. Burner (1) according to any one of the preceding claims, characterized in that the nozzle comprised in the plurality of nozzles (8) near the free end of the inner tube (4) is adapted to direct the primary gas (70) from the inner tube (4; 41) into the flow space (43) or into the mouth (43 a) of the flow space (43) in the flow direction of the primary air and upstream or downstream of a flow controller (7) located at the free end (2 a) of the burner head of the flow space (43).

11. Burner (1) according to any one of the preceding claims, wherein said discharge channel (10) is adapted to: when travelling in the travelling direction of the premixed air-gas mixture (80) towards the mouth of the discharge end (10 a) of the discharge channel (10), the discharge channel (10) narrows and the discharge channel (10) turns away as seen from the centre line (P) of the combustion head.

12. Burner according to claim 11, characterized in that the cross-sectional area of the discharge end (10 a) of the discharge channel (10) decreases in the travelling direction of the premixed air-gas mixture (80) when travelling towards the mouth of the discharge end (10 a) which is held outside the inner wall (10 c) of the discharge channel (10).

13. Burner (1) according to claim 11 or 12, characterized in that the outer wall (10 d) of the discharge end (10 a) of the discharge channel (10) is located on such an arc with a radius (R), and the inner wall of the discharge end (10 a) of the discharge channel (10) is located on such an arc with a radius (R1), wherein the radius (R) and the centre of the radius (R1) are located outside the burner head (2).

14. Burner (1) according to any one of claims 11 to 13, characterized in that the outer wall (31) of the discharge channel (10) and the inner wall (42 a) of the discharge channel (10) are curved outwards as seen from the centre line (P) of the burner head, wherein the radius of curvature (R) and the radius of curvature (R1) are equal or unequal.

15. Burner (1) according to claim 14, characterized in that the inner wall (42) of the discharge end (10 a) of the discharge channel (10) with the radius of curvature (R1) is curved more outwardly than the outer wall (31) of the discharge end (10 a) of the discharge channel (10) with the radius of curvature (R), as seen from the centre line (P) of the burner head, whereby R1> R.

16. A furnace-burner assembly for combusting an air-fuel mixture (80) and for generating a flame (B, E) in a combustion chamber (90) present in the inner side of the furnace,

the burner (1) has been defined in claim 1, and the burner (1) is connected with a furnace (9) such that: inside the combustion chamber (90) of the furnace, a second portion of the elongated burner head (2) protruding from the frame member (6) remains, a first portion of the burner head (2) remaining outside the furnace (9) or being connected to the structure of the furnace (9), characterized in that,

Some of the main flames (B) can be produced by: directing some pre-mixed air-fuel mixture (80) to a discharge channel (10), discharging the air-fuel mixture (80) from the mouth of a discharge end (10 a) of the discharge channel to the combustion chamber (90), whereby in case of viewing the discharge end (10 a) of the discharge channel (10) from the direction of a frame member (6) of the burner (1), a centre line (10L) of the discharge end (10 a) or an extension of the discharge end (10 a) forms an oblique angle of incidence (t) with a longitudinal centre line (P) of the combustion head (2), the angle (t) being about 90 to 140 degrees, and the centre line (10L) of the discharge end (10 a) or the extension of the discharge end (10 a) also forms an oblique angle of incidence (t) with the longitudinal centre line (10L) of the discharge channel (10), and

the primary flame (E) can be generated by: providing a flow space (4; 43) with a supply of primary air (60) from a frame member (6) of the burner (1) or from a portion of the burner head (2) associated with the frame member and located upstream of the combustion chamber (90) in the flow direction of the primary air (60) for delivering the flow of primary air (60) to a flow controller (7) adapted to direct the flow of primary air (60) through the mouth of the flow space (43) in a manner co-current with the main flame (B), and

-providing the inner tube (4; 41) of the inner conduit (4) with a supply of primary gas (70), the supply of primary gas (70) coming from the frame member (6) of the burner (1) or from a portion of the burner head (2) upstream of the combustion chamber (90) in the flow direction of primary air (60), whereby a nozzle of the plurality of nozzles (8) in the vicinity of the free end (4 a) of the inner tube (4; 41) is adapted to direct the primary gas (70) to be discharged from the mouth (2 a) of the burner head into the flow space (4; 43).

17. Furnace-burner assembly according to claim 16, characterized in that the primary gas (70) is conveyed from the inner tube (4; 41) through the nozzle (8) and into the flow space (4; 43) upstream or downstream of the flow controller (7) at the free end (43 a) of the flow space (4; 43) in the flow direction of the primary air (60).

18. The burner-furnace assembly according to claim 16, characterized in that the discharge channel (10) becomes narrower and deflects outwards when travelling in the direction of travel of the premixed air-gas mixture (80) towards the discharge end (10 a) of the discharge channel (10) as seen from the centre line (P) of the burner head (2), whereby the velocity of the air-gas mixture (80) increases as the air-gas mixture flows towards the mouth of the discharge end (10 a) of the discharge channel (10).

19. Furnace-burner assembly according to claim 16, characterized in that the back flow of flame together with the flow controller (7) is adapted to direct the flow of primary air (60) travelling by means of the flow controller (7) towards the mouth of the flow space (43) near the inner surface of the outer tube.

20. The furnace-burner assembly according to claim 16, wherein the intensity and stability of the primary flame (E) is controllable by adjusting the amount and speed of primary air (60) and primary gas (70).

21. Furnace-burner assembly according to claim 16, characterized in that the amount of primary air (60) supplied for generating the primary flame (E) is 5-30% of the total amount of air for generating the main flame (B) by means of the premixed air-gas mixture (80) and for creating the primary flame (E) by means of the primary air.