CN211399774U - Burner and boiler-burner assembly - Google Patents

Abstract

The utility model relates to a can install burner to boiler for making premixed air-fuel mixture burn, the burner includes frame member, and frame member is provided with the burning head of elongated, and the burning head is protruding from the frame member and the distal end that sees when the frame member is observed at the burning head is provided with the top end board. In the burner, -there is an oblique angle of incidence (a) between the side edge of the top end plate and the plane (R) of the top end plate for guiding the gas conveyed to the front face of the top end plate away from the longitudinal centre axis of the burner head, -the top end plate of the burner head is provided with a plurality of air openings extending through the top end plate, and for cooling the top end plate the inner tube is additionally provided with a supply of combustion air for conveying combustion air through the air openings of the top end plate. The utility model discloses a still relate to a boiler-combustor subassembly.

Description

Burner and boiler-burner assembly

Technical Field

The present invention relates to a burner that can be installed in a boiler for burning a premixed air-fuel mixture.

The utility model discloses still relate to a boiler-combustor subassembly that is used for making premixed air-fuel mixture burn.

Background

So-called premix burners are used for burning a premixed mixture of fuel and air. These burners are used to achieve low NOx emission levels. In the prior art, i.e. in publication US-6,238,206, a premix burner is disclosed, in particular with a long burner head, for achieving low NOx emissions (NOx emissions in the flue gas below 9 ppm) without large amounts of residual oxygen. This burner model known from the prior art is provided with a burner head associated with the frame and extending a long distance into the boiler interior. However, it has been found that the greatest disadvantage of this burner is the continuously relatively high NOx emission levels, which do not fully meet the strict emission standards, e.g. with less than 3% residual oxygen, that certain state-specified burners in the united states will operate effectively. Another disadvantage associated with the discussed prior known premix burners is their limited compatibility with commercial boilers.

SUMMERY OF THE UTILITY MODEL

The present invention aims to provide an improvement or at least alleviate the above-mentioned drawbacks of the prior art. Accordingly, a first object of the present invention is to provide a high efficiency burner mountable on a boiler, and a boiler-burner assembly in which a premixed air-fuel mixture can be combusted by the burner with low residual oxygen of less than 3% so that average NOx emissions in flue gas are kept below 15ppm, and the premixed air-fuel mixture can be combusted by the burner with low residual oxygen of less than 6% so that average NOx emissions in flue gas are kept below 5 ppm. A second object of the utility model is to provide a burner that is easier to install to commercially available boilers, and a boiler-burner assembly that is thus obtainable.

The above object will be able to be achieved with a burner that is mountable to a boiler for combusting a premixed air-fuel mixture, and with a boiler-burner assembly for combusting a premixed air-fuel mixture.

More particularly, the utility model relates to a combustor mountable to a boiler for combusting a premixed air-fuel mixture. The burner comprises a frame member provided with an elongated burner head protruding from the frame member. The distal end of the combustion head as viewed from the frame member is provided with a tip plate, and the combustion head includes a larger diameter outer tube for the mixture of combustion air and fuel and a smaller diameter inner tube for the combustion air. The outer tube of the burner head is formed with at least one row of orifices around said body of the outer tube and, furthermore, the distal end opening of the outer tube, i.e. the top end opening of the outer tube, as seen from the frame member of the burner, opens below the top end plate. The outer tube is provided with a supply of premixed air-fuel mixture from a frame member of the burner for conveying the premixed air-fuel mixture to the exterior of the combustion head via an aperture included in the body of the outer tube and via a top end opening of the outer tube, and the inner tube of the combustion head is continuous and extends from the frame member to the front of the top end plate. The top end plate has a width approximately equal to the diameter of the top end opening of the outer tube, and the direction of the plane defined by the top end plate is transverse to the longitudinal direction of the burner head. In the utility model, the water-saving device is provided with a water-saving valve,

-having an oblique angle of incidence between the side edges of the top end plate and the plane of the top end plate for directing gas delivered forward of the top end plate away from the longitudinal central axis of the burner head, and

the top end plate of the burner head is provided with a plurality of air openings extending through the top end plate, and for cooling the top end plate the inner tube is additionally provided with a supply of combustion air for conveying the combustion air through the air openings of the top end plate.

In another aspect, in the utility model of a boiler-burner assembly for combusting a premixed air-fuel mixture with a flame generated inside a boiler, the burner comprises a frame member that remains outside the boiler and has an elongated burner head associated with the frame member that protrudes from said frame member. The burner head has a first portion that remains located outside or connected to the structure of the boiler, and a second portion that extends to the interior of the boiler. The distal end of the burner head, seen from the frame member of the burner, is provided with a top end plate, said burner head comprising a larger diameter outer tube for combusting a mixture of air and fuel and a smaller diameter inner tube. Therefore, the temperature of the molten metal is controlled,

the outer tube of the burner head is formed with at least one row of orifices of said body surrounding the outer tube, and furthermore the distal end opening of the outer tube, i.e. the top end opening of the outer tube, seen from the frame member of the burner, opens into the front of the top end plate. The outer tube being provided with a supply of premixed air-fuel mixture from a frame member of the burner for conveying the premixed air-fuel mixture to the outside of the burner head via an aperture comprised in the body of the outer tube and via a top end opening of the outer tube, and,

the inner tube of the burner head is continuous and extends from the frame member to the front of a top end plate having a width substantially equal to the diameter of the top end opening of the outer tube, and the direction of a plane (R) defined by the top end plate is transverse to the longitudinal direction (P) of the burner head. In the utility model, the water-saving device is provided with a water-saving valve,

-providing a supply of combustion air from the frame member of the burner into the inner tube of the burner head for conveying the combustion air via said inner tube to the forward side of the tip plate seen from the frame member of the burner and further through air openings comprised in the tip plate for cooling said tip plate. Therefore, the temperature of the flame portion generated in the interior of the boiler, which is formed immediately behind the tip plate in the interior of the boiler in the immediate vicinity of the tip plate, is lower than the temperature of the main flame surrounding the flame portion,

the top end plate of the burner head is located at a distance from the mouth of the outer tube, which distance is such that the gas reaching the forward side of the top end plate has a flow connection from the forward side of the top end plate to the interior of the boiler, and furthermore, there is an angle of incidence between the side edges of the top end plate and the rear surface of the top end plate, as a result of which angle of incidence the gas supplied to the forward side of the top end plate is directed angularly away from the longitudinal central axis of the burner head.

Wherein it is defined that "the width of the top end plate is substantially equal to the diameter of the top end opening of the outer tube" means that in this connection the width of the top end plate may be substantially the same as, or slightly larger than or slightly smaller than, the width of the top end opening of the outer tube.

The plane R of the tip plate is understood to be a plane extending across the central axis of the tip plate and extending in the longitudinal direction of the tip plate.

In a preferred embodiment of the invention, the side edges of the top endplate are angled at about 40-80 degrees, in particular at 60 degrees, with respect to a plane defined by the top endplate when viewed from the frame member of the burner.

As a result, the air-fuel mixture discharged from the mouth of the outer tube is directed away from the longitudinal central axis of the burner head at an angle of about 40-80 degrees, particularly at an angle of 60 degrees, when viewing the flow from the frame member of the burner.

In another preferred embodiment of the invention, the outer tube of the burner head is formed with a first set of orifices, for example a set of orifices with a circular cross-section. The set of apertures constitutes a row of apertures and the apertures included therein encircle the outer tube and are proximate to a distal end of the outer tube as seen from the frame of the combustor. Furthermore, the burner head is formed with a second group of orifices consisting of orifices with elongated or oblong cross section, such as orifices with oval or elliptical cross section, which make up an orifice row, these orifices included therein surrounding the outer tube and preferably being located in the middle section of the outer tube.

Therefore, it is preferred to provide a mechanical adjustment element in connection with the outer tube of the burner head for adjusting the size of the aperture comprised in the wall of the outer tube.

The present invention is based at first on a burner head constructed from two concentric tubes, and the inner tube is supplied with cooling air which flows from the inner tube to the front of the top end plate and further through the air openings comprised in the top end plate. This cools the tip end plate while forming a side flame C (hereinafter also referred to as a flame portion) at the rear side of the tip end plate, the temperature of which is lower than that of the main flame B adjacent to the side flame C.

In the case of an inner tube supplied with electrical wires, cooling of the top end plate also achieves significant benefits in the sense that the electrical wires extending within the inner tube are protected from overheating.

Secondly, the utility model is based on an oblique angle of incidence between the side edge of the top end plate and the front surface of the top end plate, which angle is in particular 40-80 degrees. Thus, the air-fuel mixture delivered to the forward side of the tip plate via the outer tube is directed away from the longitudinal center axis of the burner head at an angle, preferably at an angle of about 60 degrees, when viewing the airflow from the frame member of the burner.

By directing the air-fuel mixture in such a way: so that the tip of the burner head (approximately rearward of the plane R defined by the tip plate) is provided with an advantageously voluminous main flame B of hollow conical shape. The large volume of the main flame B brings the main flame to a low temperature and significantly reduces NOx emissions. In addition, it is a main flame with a conical shape, enhancing the backflow inside the boiler, which further expands the main flame volume and reduces NOx emissions.

If the boiler is provided with an outlet port for flue gas on the rearward side of the plane defined by the tip plate as viewed from the frame member of the burner, a flame portion D generated by a flame portion C immediately behind the flame portion C on the rear side of the tip plate is directed therefrom, for example, into the regions of the main flame B and the side flame C, with a strong backflow of flue gas. The backflow of the flue gas in question is generated by the shape of the flame and by the oblique position of the side edges of the flame plate with respect to the front surface of the flame plate. It is the return flow of the flue gases that the carbon monoxide emissions in the region of the flame section D are efficiently burnt off.

Third, the utility model is based on an outer tube with a burner head formed with a first row of orifices, for example with circular cross-section. Furthermore, the burner head is formed with a second row of orifices, preferably comprising orifices with elongated cross-sections, such as orifices with cross-sections in the shape of an oval or elliptical shape. The air-fuel mixture delivered from the first and second rows of apertures surrounding the burner head increases the temperature of the flame portion a generated around the burner head while stabilizing that particular flame portion.

In a preferred embodiment of the invention, the outer tube is provided with a mechanical adjustment element that can be used to configure the size of the elongated aperture comprised in the wall of the outer tube, thereby providing the ability to configure the temperature of the flame portion a around the burner head to make it suitable for each boiler.

Drawings

The invention and the benefits obtained thereby will now be explained in more detail with reference to the accompanying drawings.

Fig. 1 shows in perspective view a frame member of a burner and a burner head associated with the frame member of the burner.

Fig. 2 shows a burner head for the burner of fig. 1 in slightly inclined front and side views.

Fig. 3A shows in a schematic longitudinal cross-sectional view a burner head for the burner of the present invention and a burner frame member associated with the burner head of the burner.

Fig. 3B shows the top endplate region visible in fig. 3A in more detail.

Fig. 4A shows a first embodiment of the burner of the utility model mounted to a boiler in a longitudinal cross-sectional view.

Fig. 4B schematically shows the flame generated in the boiler visible in fig. 4A and equipped with the burner of the utility model.

Fig. 5A shows a second embodiment of a burner for the utility model in longitudinal section, mounted to a boiler equipped with a so-called flashback boiler.

Fig. 5B shows in longitudinal section the flame generated in a boiler equipped with a flashback boiler, visible in fig. 5A, with the burner of the utility model mounted to the boiler.

Fig. 6A shows in a direct side view a burner head for a burner according to a second embodiment of the present invention, having its frame provided with a slightly different orifice pattern than the orifice pattern in the burner head of the burner visible in fig. 1-5.

Fig. 6B shows, in a direct side view, a burner head for a burner according to yet another embodiment of the present invention, the top endplate of the burner having a right angled edge and the frame of the burner head having an orifice pattern that is further slightly different from the orifice pattern used in the burner head of the burner shown in fig. 1-5, 6A.

By describing the structural and functional details for the burner of the present invention that are visible in the drawings, the various aspects of the burner and boiler-burner assembly of the present invention shown in fig. 1-6 will be briefly reviewed hereinafter.

Detailed Description

The general configuration of the burner 1 is depicted in fig. 1-5.

In these figures, fig. 1 shows in its entirety a burner 1 of the present invention, which can be mounted to a boiler 9, as seen from the outside.

Fig. 2 discloses details of the outer tube 3 of the burner head 2 for a burner, which remain inside the boiler when the burner is installed. The burner head 2 has the body of its outer tube 3, the body of this outer tube 3 being provided with two rows 31, 33 of orifices, these two rows 31, 33 of orifices surrounding said body 30 of the outer tube 3 and also visible in fig. 1, 3A, 4 and 5.

As shown in fig. 1 and 2, the burner 1 comprises a burner head 2 associated with a frame member 5. The burner 1 can be mounted to the boiler by means of a flange 91. The outer end of the burner head 2 as seen from the frame member 5 of the burner 1 is provided with a top end plate 7.

Visible in the longitudinal sectional view of fig. 3A is the burner head 2 for the burner 1, as well as parts of the frame member 5 of the burner as shown in the longitudinal sectional view. The figure shows the outer tube 3 of the burner head 2 and the smaller diameter inner tube 4 located entirely inside the outer tube 3.

The actual burner head 2 comprises an outer tube 3 of larger diameter and an inner tube 4 of smaller diameter, which is more clearly visible in the cross-section of fig. 3A-5, which inner tube 4 extends in its entirety inside the outer tube 3. The inner tube 4 of the burner head 2 has a body with: the body is continuous, uniform and the body of the inner tube 4 extends to the forward side 7d of the top end plate 7 as viewed from the frame member 5; 7d2 and is connected all the way to the front face 7c of the top end plate. Thus, at the junction of the inner tube, the outer tube, and the top end plate, a first space 7d2 is formed on the forward side 7d of the top end plate 7 as viewed from the frame member 5.

The inner tube 4 is intended for combustion air and, in a manner described later (see fig. 3A and 3B), serves to prevent the temperature of a top end plate 7 mounted to the boiler 1 and the temperature of a flame portion C located behind the top end plate from becoming excessively high.

The outer tube also has its mouth 35, which mouth 35 opens into the second space 7d1 on the forward side 7d of the top end plate 7. Since the inner tube 4 extends up to the front surface 7c of the top end plate, the airflows 55, 80 reaching the first space 7d2 and reaching the second space 7d1 are prevented from mixing on the forward side 7d of the top end plate 7.

The top end plate 7 has a width T substantially equal to the diameter of the top end opening 35 of the outer tube 3 in the direction of the plane R defined by the top end plate 7. The direction of the R-plane of the top endplate is transverse to the longitudinal direction P of the burner head.

The burner head 2 has its body of the outer tube 3, which body of the outer tube 3 is provided with two rows 31, 33 of orifices, which rows 31, 33 of orifices surround said body 30 of the outer tube 3, wherein each orifice comprised in the row 31 of orifices is elongated in shape, see also fig. 1, 2, 4A and 5A.

The second row of apertures formed in the burner head 2 comprises apertures having an elongate cross-section, such as apertures having an oval and/or elliptical cross-section, which extend through the body 30 of the tube 3. The set of apertures constitutes a row of apertures 31, the apertures comprised in this row of apertures 31 surrounding the tube 3 at equal distances from the distal end 3a of the outer tube 3 in a middle section or middle region of the tube 3, as seen from the frame member 5 of the burner.

Fig. 3A also shows that a mechanical adjustment element 10 is provided in connection with the outer tube 3 of the burner head 2 for adjusting the opening size of the oval apertures 31 comprised in the wall of the outer tube 3. In this case, the mechanical adjustment element comprises a flange member, in particular a collar 10a, provided on the inner surface of the outer tube, which flange member is displaceable to partly or completely cover the elongated apertures in the aperture row 31. The collar 10a makes it possible to adapt the fuel-air mixture 40 flowing out from the orifices of the orifice row 31 to become suitable for each boiler size and shape, so as to be able to optimize the temperature of the flame portion a formed around the burner head 2 in a manner described later.

Fig. 3B shows the region around the top end plate 7 of the burner head 2, which is visible in fig. 3A, also in a longitudinal sectional view and in more detail. Due to the structural features of the top end plate 7, main flames B and side flames C on the rearward side 7C of the top end plate 7 immediately behind the top end plate 7 are generated.

The top end plate 7 represents a so-called flame plate for spreading the mixture 80 of combustion air and fuel arriving from the top ends 3a of the larger tubes 3 into the boiler 9. In addition, top end plate 7 may be used to protect wires running within inner tube 4 from excessive heating.

Thus, the top end plate 7 is first provided with a plurality of air openings 71 extending through the top end plate 7, and further, the inner tube 4 has its mouth opening to the forward side 7 of the top end plate 7 immediately in the traveling direction of the combustion air 55; 7d2 and opens into alignment with air opening 71 extending through top end plate 7. The inside of the inner tube 4 is a space for electrification, for example.

For cooling this top end plate 7, the inner tube 4 is provided with a supply of combustion air 55 from the frame member 5 of the burner 1 for conveying the combustion air 55 to the forward side 7 of the top end plate 7; 7d2 and further through the air openings 71 to the rearward side 7e of the top end plate. By cooling the top end plate 7, it is possible to mount, for example, electric wires (not shown in the figure) inside the inner tube. Electrification cannot be carried out in this way in previously known burners.

The top end plate 7 is disposed at a distance from the mouth 35 of the outer tube 3 in the longitudinal direction P of the burner head 2, the distance being such as to reach, via the outer tube 3, a second space 7d provided on the forward side 7d of the front surface 7c of the top end plate 7; 7d1 flows from space 7d on the forward side of tip plate 7 in the same direction as the side edge 7a of the tip plate; 7d1 flows through the other side of the plane R of the top end plate. There is an angle of incidence a between side edge 7a of top end plate 7 and rear surface 7b of top end plate 7. The mixture of fuel and gas delivered from the outer tube into space 7d1 on the forward side of top end plate 7 preferably travels along side edge 7a of top end plate 7 with fuel and air mixture 60. Due to the angle of incidence a between the side edges 7 of the top end plate and the rear surface 7b of the top end plate, the fuel and air mixture 60 also passes over the rear surface 7b of the top end plate in an oblique orientation. Thus, the fuel and air mixture 60 is directed into the interior of the boiler, as seen in the direction of the frame member 5, outwardly and forwardly from the centerline P of the burner head 2 of the burner, at an angle of about 60 degrees, as shown more clearly in fig. 3B, 4B and 5B.

In this coordinate system, the angle running straight sideways from the longitudinal axis of the burner head is 90 degrees. The longitudinal direction of the burner head, i.e. the direction of the centre line P, is considered to be an angle of 0 degrees.

In the boiler-burner assembly of the utility model, nitrogen oxide emissions are mainly generated, because atmospheric nitrogen is oxidized due to high temperature (so-called thermal NOx emissions). By lowering the flame temperature in the boiler, NOx emissions can be effectively reduced.

By directing the flow 60 of the air-fuel mixture outwards at a right angle as seen from the longitudinal centre line of the burner head 2 of the burner 1, it is possible to produce a main flame B inside the boiler, which main flame B burns at a lower than normal temperature and generates a lower than normal amount of NOx emissions at this temperature, see also the description of fig. 4B and 5B below.

In this utility model, the flow 60 of air-fuel mixture is directed away from the centerline P of the burner head at an angle of about 650 degrees, thereby producing a beneficially voluminous main flame B in the shape of a hollow cone at the top end of the burner head 2 (behind a plane R defined approximately by the top end plate). This large volume of the main flame B achieves a low temperature for the main flame and significantly reduces the thermal NOx emissions. Furthermore, the conical shape of the main flame enhances the return flow inside the boiler 9, which further expands the volume of the main flame B and reduces NOx emissions.

In fig. 4A an embodiment of the invention is shown, wherein the burner 1 visible in fig. 3A-3B is mounted to the boiler 9 by means of a flange 91; 9', a boiler 9; the flue gas in 9' is discharged from the boiler from the rear of the top end plate 7 as seen when viewed from the frame member 5.

Such a boiler 9 is depicted in fig. 4B by means of the burner of the present invention; 9' of the flame A, B, C, D. Boiler 9 visible in fig. 4B; 9' is provided with an outlet port for flue gas behind a plane R defined by the top end plate of the burner head, as seen from the frame member 5 of the burner. In such a boiler, a flame portion D, the temperature of which is higher than that of the flame portion C, is generated immediately behind the top end plate 7 behind the flame portion C behind the top end plate 7. In the region of the flame section D, virtually all the fuel has been completely burnt, but the combustion of the carbon monoxide emissions (CO emissions) continues. In the region of the flame section D strong backflow is generated, which flows into the flame section C and from there further into the flame section B. These back flows enhance the complete combustion of carbon monoxide and in practice the carbon monoxide emissions in the burner-boiler assembly of the utility model are really very low, 0-50ppm, with which even 0ppm carbon monoxide emissions can be achieved.

In fig. 5A, another embodiment of the invention is shown, wherein the burner 1 visible in fig. 3A-3B is mounted to the boiler 9 by means of a flange 91; 9', a boiler 9; the flue gases in 9' leave the boiler (this is a boiler equipped with a so-called flashback boiler) from the forward side of the top end plate 7 as seen from the frame member 5. The burner of the utility model can be used in such a boiler 9; the flame A, B, C, D obtained in 9' is visible in fig. 5B.

The most important aspects of the invention will now be reviewed in more detail with reference to the preceding brief description of figures 1-5.

The boiler-burner assembly of the utility model and the generation of the flame inside the boiler 9 are shown in fig. 4A-4B and 5A-5B. Fig. 1 and 3A show a flange 91, which flange 91 surrounds the burner head 2, and by means of which flange 91 the burner head 2 of the burner 1 is coupled to the wall of the boiler 9. In the boiler-burner assembly thus constructed, the burner 1 comprises a frame member 5, which frame member 5 remains outside the boiler 9 and to which frame member 5 an elongated burner head 2 protruding from said frame member 5 is connected. The burner head 2 has its first portion 22, which first portion 22 is held outside the boiler 9 or which first portion 22 is connected to the structure of the boiler 9 by means of a flange 91. In the embodiment of the invention shown in fig. 4A and 4B and fig. 5A and 5B, the part 2 of the burner head, similar to what has been described above; 21 are held within the boiler 9.

As described above, the opening at the distal end of the outer tube 3 as viewed from the frame member of the burner 1, that is, the opening 35 at the tip end 3a of the outer tube 3, opens into the space 7d1 located on the forward side 7d of the tip end plate 7. The top end plate 7 serves for spreading the flame, for lowering the temperature of the main flame B available inside the boiler and for generating a flame portion C behind the top end plate.

In order to generate the flame portion C, there is provided a supply of inner-tube combustion air 55 from the frame member 5 of the burner 1 into the inner tube 4 of the burner head 2, by means of which inner tube a flow of combustion air 55 travels along this inner tube 4 to a first space 7d2 provided at the forward side 7d of the tip plate 7 as seen when viewed from the frame member 5 of the burner 1 and further flows through the air openings 71 included in the tip plate to the rearward side of the tip plate. A flame section C is generated by supplying inner tube combustion air 55 through the inner tube 4 through the top end plate 7 into the interior 90 of the boiler 9 at the rearward side 7e of the top end plate, the flame section C being adjacent on each side thereof to the tapered main flames B. The flame portion C has a temperature lower than that of the main flame B, whereby the flame portion C cools the main flame B and, in addition, cools the top end plate 7 and, as appears hereinafter, the air duct extending within the tube 4. The cooling of the air duct located inside the tube 4 enables, for example, electric wires to be brought inside the tube 4. The temperature of the flame section C behind the top end plate 7 depends on the boiler size, whereby the flame section C may typically have a temperature of e.g. 900-. The temperature of the flame section C generated in the interior 90 of the boiler 9 is lower than the temperature of the main flames B surrounding the flame section C.

The outer tube 3 is provided with outer tube combustion air 50. Outer tube combustion air 50 arrives from the frame member 5 of the combustor 1, the outer tube combustion air 50 is premixed with the mixer 8, and then the mixed outer tube combustion air 50 is refueled via the row of orifices 72 for fuel (see fig. 3A, 4A, 5A). The orifices of the orifice row 72 surround the outer tube 3 at a short distance from the mixer 8 in the longitudinal direction P of the burner head 2. The premixed air-fuel mixture 80 thus produced further proceeds toward the distal end 3a of the outer tube 3 as seen from the frame member. The premixed air-fuel mixture 80 finds its way outside the burner head 2 through the orifices of the orifice rows 31, 33 comprised in the body of the outer tube 3, and through the mouth (tip opening) 35 of the outer tube 3, which mouth (tip opening) 35 of the outer tube 3 opens into the space 7d1 located on the forward side 7d of the tip plate 7 and defined by the front surface 7c and the side edges 7a of the tip plate 7. The space 7d1 is defined by the outer surface of the inner tube 4 in the longitudinal direction of the burner head 2, and the mouth 35 of the outer tube opens into the space. The space 7d1 opens in a direction away from the centerline of the burner head 2.

The burner head 2 has its top end plate 7, which top end plate 7 is located at a distance from the mouth 35 of the outer tube 3, which distance is such that the gas mixture 80 of air and fuel arriving in the space 7d1 located at the forward side 7d of the top end plate 7 has a flow connection from the space 7d1 of the forward side 7d of the top end plate 7 into the interior 90 of the boiler 9.

As shown in fig. 3A, 3B, 4A and 5A, there is an oblique angle of incidence a between the side edge 7a of top endplate 7 and the back surface 7B of top endplate (or the plane R defined by the top endplate). The angle of incidence a is about 40-80 degrees, particularly about 60 degrees, when the top end plate 7 is viewed from where the frame member of the burner 1 is located. Preferably, the incident angle is about 60 degrees when the top end plate is viewed from the frame member 5 of the burner. This angle of incidence a between the side edges and the plane R of the top endplate has the result that: such that the side edge 7a of the tip plate directs the air-fuel mixture 80 supplied into the space 7d1 located on the forward side 7d of the tip plate 7 to travel along said side edge 7a, thereby directing the flow 60 of air-fuel mixture 80 away from the longitudinal centerline P of the combustion head; and the flow 60 is directed away and forward at an angle of about 40-80 degrees as viewed from the frame member 5, at an angle of about 60 degrees as viewed from the frame member 5, when viewed from the longitudinal centerline P of the combustion head 2 and the frame member 5. The coordinate system is the same as previously mentioned.

This flow 60 of air-fuel mixture 80 contributes to the main flame B being conical in shape and having an enlarged combustion area. Large combustion volumes and low power densities are achieved due to the extensive conical combustion zone. The low power density results in low combustion temperatures and thus low NOx emissions. The conical shape of the main flame B around the tip of the burner head 2 also enhances the back flow which stabilizes the main flame B and mixes the flue gas into the main flame B, which further expands the conical combustion zone and thereby lowers the combustion temperature within the main flame zone.

The main flame B is partially stabilized by a flame portion C generated at the rearward side of the tip end plate C, but the main flame B is mainly stabilized by using a flame portion a developed to surround the burner head 2 and be adjacent to the main flame (see fig. 4B and 5B). In order to generate a suitable type of return flow of the flue gas, the outer tube 3 of the burner head 2 is preferably formed with a first set of apertures consisting of apertures with a circular cross-section, said first set of apertures constituting an aperture row 33, the apertures included therein surrounding the body 30 of the outer tube 3 at an equal first distance from the distal end 3A of the outer tube 3 seen from the frame member 5 of the burner (see fig. 3A, 3B, 4A, 4B, 5A, 5B).

The outer tube 3 of the burner head 2 is also formed with a second set of orifices constituting a row 31 of orifices, these orifices included therein surrounding the outer tube 3 and being located in a middle or intermediate region of the outer tube 3 at an equal second distance from the distal end 3a of the outer tube 3 seen from the frame member 5 of the burner.

Preferably, the orifices of the first orifice row 33 are located closer to the top end of the burner head 2 than the orifices of the second orifice row 31.

The orifices of the second orifice row 31 are orifices with an elongated cross-section, such as orifices with an oblong, oval or elliptical cross-section, which extend through the body 30 of the outer tube 3. An air flow, such as flow 40 of air-fuel mixture 80, directed from frame 5 into outer tube 3 and further to end 3a of the tube, travels through the orifices of both orifice row 31 and orifice row 33. The flow 40 of the air-fuel mixture 80 through these orifices has its velocity through the orifices of the orifice rows 31, 33, which depends, among other things, on the flow rate of the flow 40 of the air-fuel mixture 80 and the size of the orifices in the orifice rows 31, 33.

As can be seen from fig. 4A and 5A, the fuel-air mixture 80 is discharged via the rows of orifices 31 and 33 in the form of a stream 40, the direction of which stream 40 is at an angle of about 90 degrees with respect to the longitudinal centre line P of the burner head, thereby generating a flame portion a around the burner head 2. There is a lot of turbulence and flue gas recirculation around the burner head 2. When this region is supplied with an air-fuel mixture in the form of an air flow 40 from the orifices of the orifice rows 31, 33, this air-fuel mixture, as a result of its combustion, produces a flame portion a which increases the temperature in the vicinity of the burner head and stabilizes the main flame B adjacent to the flame portion a. The temperature of this flame section is strongly dependent on, for example, the diameter of the boiler 9, and in larger boilers, in addition to that the flame section a has a larger combustion area and the flue gas return has a larger mass flow rate. As already indicated above, by means of the mechanical adjusting element 10; 10' the size of the apertures included in the row 31 of apertures consisting of elongated apertures can be adjusted so that the temperature of the flame section a can be suitably adjusted for each boiler type.

In the boiler-burner assembly shown in fig. 5B, a boiler 9; the 9', so-called flashback boiler, has an outlet port for flue gas behind the plane R defined by the top end plate 7 of the burner head 2, seen from the frame member 5 of the burner 1. This type of boiler produces a substantially similar main flame B, a flame section C behind the top end plate, and a flame section a that surrounds and elevates the temperature in the vicinity of the burner head and stabilizes the main flame B, whereby the flame section a is confined in the same manner as the boiler-burner assembly of fig. 4A-4B. However, in this case, the backflow of the flue gas from the main flames B is diverted towards the outlet port of the flue gas, whereby the main flames are generally small. The flame portion D is not of great significance in this type of boiler-burner assembly.

It will be obvious to a person skilled in the art that the invention can also be implemented in various other ways. Thus, several alternative implementations of the burner of the present invention are shown in fig. 6A and 6B.

Fig. 6A shows a burner head 2 for the burner 1 of the present invention; 2' in an alternative configuration. The burner head 2; 2' are provided with a top end plate similar to that included in the burner 1 shown in figures 1-5, but in this case the outer tube 3 is formed with only a single set of apertures constituting an aperture row 31, the apertures included therein being apertures having an elongated, oblong cross-section, such as an oval or elliptical cross-section. The row of orifices surrounds the body 30 of the outer tube 3 and is located approximately in the middle of the body. It is also possible to provide a boiler-burner assembly in such a way that the main flame B has a relatively large volume.

Fig. 6B shows a burner head 2 for the burner 1 of the present invention; 2 "which provides some of the advantages of the burner according to the invention. The burner head 2 in fig. 6B; 2 ", a virtual angle of incidence a formed by the side edge 7a of the top end plate 7 together with the plane R defined by the top end plate is co-directional with the centerline P of the burner head 2. Therefore, the air-fuel mixture discharged from the tip end 3a of the outer tube 3 is directed at an angle of 90 degrees and away from the longitudinal centerline P of the burner head 2. In addition, the outer tube 3 of the burner head 2 is formed with three consecutive rows of orifices, each of said three rows of orifices constituting a row 37 of orifices; 37', 37 "', the orifices included therein being circular in cross-section and each orifice row surrounding the outer tube 3 and preferably being located in the middle section of the body of the outer tube 3.

List of markers

Burner 1

Burner head 2

Maintaining the portion 21 located inside the boiler

Maintaining the portion 22 outside the boiler

Larger diameter pipe, outer pipe 3

Body 30

The row of elongated apertures 31

First orifice row 33

One or more second rows 37 of apertures

Distal end of tube, tip end 3a of tube

Mouth, top end opening 35

Proximal end 3b of the tube

Inner tube, smaller diameter tube 4

Frame member 5 of burner

Top end plate 7

Side edge 7a

Rear surface 7b

Front surface 7c

Forward side 7d

Spaces 7d1, 7d2 on the forward side

Rear-facing side 7e

Air opening 71

Fuel opening line 72

Mixing device 8

Boiler 9

Inner portion 90

Flange 91 for coupling between boiler and burner

Mechanical adjusting element 10

Flow of premixed air-fuel mixture (into boiler) 40

Outer tube combustion air supply 50

Inner tube combustion air supply 55

Flow 60 of the gas mixture from one side of the top endplate (into the boiler)

Flow 65 of combustion air through the top end plate (into the boiler)

Premixed air-fuel mixture 80

Flame A, B, C, D

Side flame A around burner head

Main flame B

Side flame C immediately behind tip plate

Farther side flame D behind the tip plate

Angle a between plane R and side edge 7a of top end plate

Supplied air I

Longitudinal direction P of burner head

Plane R defined by the top end plate

The width T of the top endplate.

Claims (33)

1. A burner mountable to a boiler (9) for burning a premixed air-fuel mixture, the burner (1) comprising a frame member (5), the frame member (5) being provided with an elongated burner head (2), the burner head (2) protruding from the frame member and being provided with a tip plate (7) at a distal end of the burner head (2) seen from the frame member, the burner head (2) comprising a larger diameter outer tube (3) for the mixture of combustion air and fuel and a smaller diameter inner tube (4) for combustion air, wherein,

the outer tube (3) of the burner head (2) is formed with at least one row of orifices surrounding the body (30) of the outer tube (3) and furthermore the distal end opening of the outer tube, seen from the frame member of the burner (1), i.e. the tip end opening (35) at the tip end (3a) of the outer tube (3), opens below the tip end plate (7), the outer tube (3) being provided with a supply of premixed air-fuel mixture (80) for transporting the premixed air-fuel mixture (80) to the outside of the burner head (2) via the orifices in the at least one row of orifices included in the body of the outer tube (3) and via the tip end opening of the outer tube, and

the inner tube (4) of the burner head (2) being continuous and extending from the frame member (5) to the front of the top end plate, the top end plate (7) having a width (T) substantially equal to the diameter of the top end opening (35) of the outer tube (3), and the direction of a plane (R) defined by the top end plate (7) being transverse to the longitudinal direction (P) of the burner head, the longitudinal direction of the burner head being the direction of the longitudinal central axis of the burner head,

the burner is characterized in that it is provided with a burner,

-having an oblique angle of incidence (a) between the side edge (7a) of the top end plate (7) and the plane (R) of the top end plate (7) for directing the gas delivered to the front of the top end plate (7) away from the longitudinal central axis of the burner head (2),

-the top end plate (7) of the burner head (2) is provided with a plurality of air openings (71) extending through the top end plate (7), and for cooling the top end plate (7) the inner tube (4) is additionally provided with a supply of combustion air (55) for conveying the combustion air through the air openings (71) of the top end plate.

2. Burner (1) according to claim 1, characterized in that the mouth of the inner tube (4) opens into a first space (7d2) provided on the forward side (7d) of the top endplate (7) in the direction of travel of the combustion air and is aligned with the air opening (71) of the top endplate (7).

3. The burner (1) according to claim 1, wherein the combustion air (55) is adapted to flow from the frame member (5) of the burner through the inner tube (4) and also along the inner tube (4) extending to a front surface (7c) of the tip plate (7) as seen from the frame member (5) of the burner into a first space (7d2) provided at a forward side (7d) of the tip plate (7), and the combustion air (55) further flows through the air opening (71) of the tip plate (7) to a rearward side (7e) of the tip plate (7).

4. The burner (1) according to any of claims 1 to 3, characterized in that a top end plate (7) of the burner head (2) is arranged at a distance from the top end opening (35) of the outer tube (3) such that the air-fuel mixture (80) reaching via the outer tube into a second space (7d1) arranged at a forward side (7d) of a front surface (7c) of the top end plate (7) can flow from the second space (7d1) at the forward side (7d) of the top end plate (7) into an interior (90) of the boiler (9).

5. Burner (1) according to claim 2, characterized in that the mouth of the inner tube (4) is adapted to open into a first space (7d2) at the forward side (7d) of the tip plate and the tip opening of the outer tube (3) is adapted to open into a second space (7d1) at the forward side (7d) of the tip plate, whereby mixing of the air-fuel mixture reaching the first space (7d2) and the second space (7d1) at the forward side (7d) of the tip plate is prevented by means of the outer surface of the inner tube (4).

6. A burner (1) according to claim 1, characterized in that the outer tube (3) of the burner head (2) is formed with a first set of apertures constituting an aperture row, the apertures comprised in the first set of apertures surrounding the outer tube and being close to the distal end of the outer tube seen from the frame member (5) of the burner, and in addition the burner head (2) is formed with a second set of apertures being apertures with an elongated cross-section constituting an aperture row, the apertures comprised in the second set of apertures surrounding the outer tube (3) and being further away from the distal end of the outer tube seen from the frame member (5) of the burner.

7. Burner (1) according to claim 6, characterized in that said first set of orifices is an orifice with a circular section.

8. Burner (1) according to claim 6, characterized in that said second set of orifices is orifices having an oval or elliptical section.

9. The burner (1) according to claim 6, characterized in that the orifices comprised in the second group of orifices making up an orifice row are located in the middle section or intermediate zone of the outer tube.

10. Burner (1) according to claim 6, characterized in that said burner head (2) is further provided with a mechanical adjustment element (10) connected to the outer tube (3) of said burner head, said mechanical adjustment element (10) being intended to adjust the opening size of said apertures comprised in the wall of said outer tube (3).

11. Burner (1) according to claim 10, characterized in that said mechanical adjustment element (10) comprises a flange piece which is provided on the inner surface of said outer tube and which is displaceable to partially or completely cover said apertures of said second group of apertures with elongated cross-section that make up an aperture row.

12. A burner (1) according to claim 11, wherein said flange member is a collar.

13. The burner (1) according to claim 1, characterized in that a virtual angle of incidence (a) formed by the side edges of the top end plate (7) together with a plane (R) defined by the top end plate is co-directional with the longitudinal central axis of the burner head (2), so as to direct the air-fuel mixture discharged from the top end (3a) of the outer tube (3) at an angle of 90 degrees and away from the longitudinal central axis of the burner head (2).

14. Burner (1) according to claim 13, characterized in that the outer tube (3) of the burner head (2) is formed with three consecutive rows of orifices, each row of orifices of said three rows constituting a row of orifices and each row of orifices surrounding the outer tube (3).

15. Burner (1) according to claim 14, characterized in that the cross-section of the orifices comprised in each row of orifices making up a row of orifices is circular.

16. Burner (1) according to claim 14, characterized in that each row of orifices is located in the middle section of the body of the outer tube.

17. Burner (1) according to claim 1, characterized in that the side edges (7a) of the top endplate (7) are at an angle of 40-80 degrees with respect to a plane (R) defined by the top endplate (7) seen when the top endplate is seen from the location of the frame member (5) of the burner (1).

18. Burner (1) according to claim 1, characterized in that the side edges (7a) of the top endplate (7) are at an angle of 60 degrees with respect to a plane (R) defined by the top endplate (7) seen when the top endplate is seen from the location of the frame member (5) of the burner (1).

19. The burner (1) according to claim 17, characterized in that the outer tube (3) of the burner head (2) is formed with a single group of orifices constituting a row of orifices, the orifices comprised in said single group constituting a row of orifices being elongated in cross-section, said single group constituting a row of orifices surrounding the body (30) of the outer tube (3) and being located in the middle section of the outer tube.

20. The burner (1) according to claim 19, characterized in that the cross-section of the orifices comprised in the single group of orifices constituting a row of orifices is oval or elliptical.

21. Burner (1) according to claim 1, characterized in that the inner tube (4) has an electric wire running inside the inner tube.

22. A boiler-burner assembly for combusting a premixed air-fuel mixture (80) with a flame generated in the interior (90) of a boiler (9),

the burner (1) comprising a frame member (5) which remains outside the boiler (9), and the burner (1) having an elongated burner head (2) associated with the frame member (5), the burner head (2) protruding from the frame member (5) and having a first portion (22) and a second portion (21), the first portion (22) of the burner head (2) remaining outside the boiler (9) or connected with the structure of the boiler (9), the second portion (21) of the burner head (2) extending into the interior of the boiler (9), and a top end plate (7) being provided at the distal end of the burner head (2) seen from the frame member (5) of the burner (1), the burner head (2) comprising a larger diameter outer tube (3) for combusting a mixture of air and fuel and a smaller diameter inner tube (4), wherein the content of the first and second substances,

the outer tube (3) of the burner head (2) is formed with at least one row of apertures surrounding the body of the outer tube (3) and furthermore the distal end opening of the outer tube (3), seen from the frame member of the burner (1), i.e. the tip end opening (35) at the tip end (3a) of the outer tube (3), opens into a second space (7d1) at the forward side (7d) of the tip end plate (7), the outer tube (3) being provided with a supply of premixed air-fuel mixture (80) for transporting the premixed air-fuel mixture (80) to the outside of the burner head (2) via the apertures in the at least one row of apertures comprised in the body of the outer tube (3) and via the tip end opening (35) of the outer tube, and the number of the first and second groups,

the inner tube (4) of the burner head (2) being continuous and extending from the frame member (5) into a first space (7d2) located on a forward side (7d) of the tip plate (7), the tip plate (7) having a width (T) approximately equal to the diameter of the tip opening (35) of the outer tube (3), and the direction of a plane (R) defined by the tip plate (7) being transverse to the longitudinal direction (P) of the burner head (2), the longitudinal direction of the burner head being the direction of the longitudinal central axis of the burner head,

said boiler-burner assembly being characterized in that,

providing a supply of combustion air (55) from a frame member (5) of the burner (1) into an inner tube (4) of the burner head (2) for conveying the combustion air (55) via the inner tube to a forward side (7d) of the top end plate (7) as seen from the frame member (5) of the burner (1) and further through air openings (71) comprised in the top end plate for cooling the top end plate, whereby a first flame portion (C) generated in an interior (90) of the boiler (9) forming behind the top end plate (7) immediately adjacent to the top end plate (7) in the interior (90) of the boiler is at a lower temperature than a main flame (B) surrounding the first flame portion (C),

a top end plate (7) of the burner head (2) is positioned at a distance from a top end opening (35) of the outer tube (3), the distance being such that gas reaching into a second space (7d1) located at the forward side (7d) of the top endplate (7) has a flow connection from the second space (7d1) located at the forward side (7d) of the top endplate (7) into the interior (90) of the boiler (9) and, furthermore, having an angle of incidence (a) between a side edge (7a) of the top end plate (7) and a plane (R) defined by the top end plate (7), due to the angle of incidence (a), the gas supplied to the forward side of the top end plate (7) is directed angularly away from the longitudinal central axis of the burner head (2), thereby generating a main flame (B) surrounding said first flame portion (C).

23. The boiler-burner assembly according to claim 22, characterized in that the supply of premixed air-fuel mixture (80) comes from a frame member (5) of the burner.

24. The boiler-burner assembly according to claim 22, wherein the gas reaching the second space (7d1) located at the forward side (7d) of the top endplate (7) is the air-fuel mixture (80).

25. The boiler-burner assembly according to claim 22, characterized in that between the side edge (7a) of the top end plate (7) and the rear surface (7b) of the top end plate (7) there is an angle of incidence (a) of 40-80 degrees when the top end plate (7) is viewed from the location of the frame member of the burner (1) for directing the flow of the air-fuel mixture (80) discharged from the top end opening (35) of the outer tube (3) into: the flow, when viewed from the location of the frame member of the burner, is directed away from the longitudinal central axis of the burner head at an angle of 40-80 degrees, respectively.

26. The boiler-burner assembly according to claim 22, characterized in that between the side edge (7a) of the top end plate (7) and the rear surface (7b) of the top end plate (7) there is an angle of incidence (a) of 60 degrees when the top end plate (7) is viewed from the location of the frame member of the burner (1) for directing the flow of the air-fuel mixture (80) discharged from the top end opening (35) of the outer tube (3) to: the flow, when viewed from the location of the frame member of the burner, is correspondingly angled away from the longitudinal central axis of the burner head by an angle of 60 degrees.

27. The boiler-burner assembly according to claim 25 or 26, characterized in that the flow of premixed air-fuel mixture (80) provided from a frame member (5) of the burner (1) into an interior (90) of the boiler (9) via an outer tube (3) of the burner head (2) generates a main flame (B) in the interior (90) of the boiler (9) in which combustion of fuel takes place in a conical combustion zone at the tip of the burner head (2).

28. The boiler-burner assembly according to claim 22, wherein a flow of an air-fuel mixture (80) is additionally provided via the orifices of the at least one row of orifices to generate a second flame portion (a) surrounding the burner head (2) and adjacent to the main flame (B) to stabilize the main flame (B).

29. The boiler-burner assembly according to claim 28, characterized in that said air-fuel mixture (80) is adapted to flow and the temperature and combustion area of said second flame portion (a) can be varied by varying the diameter of the orifices comprised in said at least one row of orifices.

30. The boiler-burner assembly according to claim 22, characterized in that the boiler (9) is provided with outlet ports for flue gases on a rearward side of a plane (R) defined by a top end plate (7) of the burner head (2) as seen from a frame member (5) of the burner (1).

31. The boiler-burner assembly according to claim 30, characterized in that a third flame portion (D) is generated after said first flame portion (C), the temperature of said third flame portion (D) being lower than the temperature of the flame portion of the main flame (B).

32. The boiler-burner assembly according to claim 22, characterized in that the outer tube (3) of the burner head (2) is formed with a plurality of rows of orifices surrounding the outer tube, and one of the rows of orifices is composed of elongated orifices having an adjustable diameter.

33. The boiler-burner assembly according to claim 30, characterized in that the flue gas is discharged from the boiler (9) from a forward side of the plane (R) defined by the top end plate (7) of the burner head, seen when viewed from a frame member (5) of the burner (1).

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