EP2029939B1 - Furnace for solid fuels - Google Patents

Abstract

A burner plate (12) has an opening (3) for afterburning heating gases from the fuel via horizontally-supplied secondary air. A nozzle part (5) is connected to the opening and tapers in cross-section from a combustion chamber (6) to an afterburning chamber (4). The secondary air is horizontally supplied into the nozzle part through the opening. The nozzle part is arranged near to the combustion chamber and faces the afterburning chamber. The nozzle part is made of fire-resistant material.

Description

Technical area

The invention relates to a kiln according to the preamble of claim 1. Such a kiln is made, for example EP 0 641 969 A1 known.

State of the art

Such furnaces, in particular so-called wood gasification boilers, have the characteristic that they improve the energy yield as well as the pollutant content of the flue gases by means of secondary air.

A burner of this kind is from the EP 0 268 208 B1 known. This comprises a combustion chamber, a burner plate designed as a burner brick and an afterburner chamber underneath. The burner block has an insert recess in which an insert part is inserted. In the burner block and in the insert part openings are formed so that there is a through opening when inserted burner block. In this case, an annular channel is formed so that an air path via a secondary air duct, the annular channel and the openings for the secondary air results. The air duct in the region of the opening is frustoconical, so that the radii decrease towards the post-combustion chamber. Through this training, a concentration to the flame or heat front is possible. The combustion gases are also intensively intermixed with each other, so that intensive combustion occurs and there is improved oxidation in the combustion gas. The secondary air is supplied horizontally in this furnace.

Another feststoffbefeuertes heater is in the DE 91 07 850 U described. The device is divided into a combustion chamber and an ash storage room or a combustion chamber with a burner stone. In the area of the burner stone a truncated cone is present, are drawn through the combustion gases. In this solution, a secondary air duct is also present. The secondary air is also supplied horizontally here.

Another solution in the DE 81 21 837 U is presented, characterized by the fact that above the secondary secondary air ducts a combustion chamber bell is installed in a combustion chamber which, together with a combustion chamber wall, defines a flue gas guiding space and forms an approximately flush extension of the lateral secondary air ducts. This design ensures that the combustion chamber wall is not adjacent to its circumference on the combustion chamber at any point, whereby a heat stress is reduced and the durability of the combustion chamber wall is increased. The burn-through boiler created in this way is designed for low-value fuels such as lumber and straw.

A boiler for burning solid fuels according to the so-called burn-through principle is improved in terms of pollutant formation and energy yield, characterized in that a convective heating surface of the boiler or a Heizgasabzug is provided with a innenberippten cylinder. For intake, an exhaust fan is used. In this design, primary combustion air passes under a grate. The secondary air flows in via a burnout chamber.

A furnace with natural draft for combustion of solid fuels is in the DE 40 07 849 C3 shown and described. The flue gases are supplied centrally in a passageway secondary air. The formation of the air supply paths is complicated and expensive in this furnace.

In order to improve both the energy yield and, above all, to reduce the pollutant content of the flue gases in an oven, in the solution according to the DE 44 35 749 C2 the flue gases are not discharged directly to the environment, but burned again in a Nachbrennraum under additional supplied combustion air, namely the secondary air. This avoids that flue gases, which contain many flammable, not yet oxidized particles, are delivered unburned. Namely, these particles are highly pollutants. This is achieved by a good mixing of the sucked flue gases with secondary air. For this purpose, several nozzles with frusto-conical cross section are required. In a special design, an existing also made of sheet metal, welded or spread partition is used in a cavity of an inner hollow body. As a result, on the one hand, secondary air and, on the other hand, flue gas can be supplied from the secondary discharge of the nozzle arrangement.

A heating device in which the energy yield is improved and the pollutant content of the pollutants is reduced, discloses the DE 44 35 748 C2 , Again, the flue gases are not derived directly to the environment but burned in a Nachbrennraum under secondary air supplied. The secondary air is supplied through a plurality of horizontal feed body, but the secondary air is fed vertically to these bodies. Each feed body is frusto-conical and protrudes into a side adjacent room, so that particularly easily turbulent eddy currents and good mixing of the flue gases with secondary air is achieved. By this principle, in which the neighboring space is arranged laterally, the distance of the glow to the nozzle-like Zuführkörpern is large, so that the temperature of the feed is relatively low.

The kilns of the prior art acknowledged herein may also be provided with nozzle tops which may be insertable into a first aperture disposed on the upper burner plate. The structure of such nozzle tops of the prior art is characterized in that they have a cover surface which is planar. In a terminology used herein, the nozzle top could therefore also be referred to as a cover plate. A nozzle top substantially causes it to cover the burner hole, thus preventing uncontrolled falling of wood or charcoal pieces through the burner hole. In another terminology, nozzle tops are also referred to as a turbo disk. This name results from the slanted lamellae with which the nozzle top is provided and bring the wood gases with primary air in rotation and mix in the swirl chamber of the kiln with the secondary air.

By the kilns according to the prior art and the good thermal conductivity of metal particles and gases are burned much better with the help of the secondary air. Due to the relatively low mass of the thin-walled nozzle insert in conjunction with the high thermal conductivity rapid heating of the nozzle part is achieved, which can achieve good combustion values after a few minutes after lighting the furnace.

A good oxidation and reduction of pollutants is achieved without the principle of a horizontal gas inlet of the burner must be left and without a complex furnace construction. The nozzle top is vertical and located directly under the embers, which creates a very high temperature of the nozzle top, but also the nozzle part and thus optimum combustion values.

An assembly is also very simple, since the nozzle top, for example, can be easily inserted into the opening of a burner plate and fastened there. The installation of the nozzle part is also very simple, since an installation space was created by the division of the burner plate in an upper burner plate and a lower burner plate, which also serves to supply the secondary air.

From the assessment of the prior art shows that not inconsiderable temperature differences occur in furnaces of the type mentioned due to the heat flows occurring. These differences in temperature cause cracks to form in flat cover surfaces of nozzle tops at high temperature loads. These cracks have their cause in stresses in the material of the covering surface, which occur when due to thermal expansion due to high temperatures, the covering area initially increases, and then shrinking again on cooling. Such a process ultimately leads to cracks or at least to distortion in the flat covering surface.

Presentation of the invention. Task. Solution. advantages

The invention has for its object to provide a kiln of the generic type, in which the disadvantages shown are avoided in a simple manner.

This object is achieved by a kiln with the characterizing features of claim 1 in conjunction with its generic features.

The special inventive design of the nozzle top is particularly advantageous. The design of the peripheral edge with the lamellae arranged thereon and the central truncated cone a particularly good adaptability to the thermal loads is achieved. When heating up to the operating temperature, there is a corresponding expansion, which is not limited by the bearing over the slats. In addition, it has been found that due to the geometry during expansion and subsequent cooling, a certain shrinkage sets in, which could lead to cracking. However, the combination of the peripheral edge in the form of a ring in connection with the truncated cone leads to a stress compensation and a material displacement, so that cracking is avoided.

In the context of the invention, it is additionally provided that the covering surface of the nozzle upper part has recesses and / or elevations. Characterized in that the cover surface of the nozzle upper part recesses and / or elevations, the planar part of the covering surface is reduced.

By reducing the plane surface, the internal stress in the nozzle top is reduced and thus also the cracking. The pits and elevations imply a paragraph or level. This step or step acts as a spring between the planar part of the surface and the surfaces of the depressions or elevations, which results in certain elasticities within the covering surface of the nozzle upper part.

In an advantageous development of the furnace according to the invention it is provided that the nozzle upper part and the nozzle part consists of sheet metal material. On the one hand, this material offers high resistance to fire and, on the other hand, is easy to process. It is also inexpensive. Sheet metal has even proved to be more durable than chamotte, because due to the high and rapid temperature changes thermal stresses occur, which are only tolerated by sheet longer term.

So that a secondary air to be fluidized can enter the nozzle part and good mixing of the air with the particles to be combusted is possible, it is preferably provided that the nozzle part is provided with circumferential window-like air inlet openings, through which the secondary air enters the nozzle part. The air inlet openings need not be present directly on the nozzle part.

In a further advantageous embodiment of the invention, the nozzle part is provided with external profiles, in particular provided with air guide fins or with guide elements for swirling the secondary air. The louvers are shaped or positioned so that a rotational movement of the air and thus a complete combustion is achieved. Conveniently, the burner plate made of stone, in particular of firebrick. Due to the material combination achieved (sheet / chamotte) creates a favorable temperature distribution, with a long shelf life of both materials is given. The burner plate can be water cooled.

This glowing pieces of wood can not fall through uncontrollably through the nozzle part, the nozzle top is formed with a peripheral edge web and a truncated cone and mounted on fins, so that an annular gap is formed with inlet openings between the fins. This allows a controlled gas entry.

It is particularly advantageous if the burner plate is provided with an upwardly directed collar on which the lamellae of the nozzle upper part are mounted. This so existing paragraph is raised, so that ash is up to the annular gap or slot on the burner chamber floor and is not immediately entrained. This further reduces the dust emission. The ash also forms an insulating layer opposite the burner plate. This burner plate is thus less burdened by heat. The paragraph can also be made of metal as a ring and integrally formed on the nozzle top. In addition, the collar can be releasably up or used.

It is advantageous if the nozzle part consists of a nozzle upper part which can be inserted into a first aperture arranged on the upper burner plate and consists of a nozzle lower part, which can be placed on a second burner plate arranged on a second opening. This solution is very easy to install, because both parts can be prefixed to the respective openings. The nozzle top can also be made differently than the lower part. For example, the upper part may be formed as a casting, while the lower part may be a deep-drawn part. The wall thicknesses of both parts can also be customized be dimensioned so that the mechanical strength and thermal conductivity of the nozzle part can be optimized. The top can be thicker and more stable, while the bottom can be very thin.

A very rapid heating of the nozzle part, which is important for optimum exhaust gas and heating values, can be achieved if the wall thickness of the nozzle part is less than 5 mm, in particular 1-3 mm.

In the context of the invention, further embodiments of the nozzle upper part according to the invention are provided.

Advantageous embodiments of the nozzle upper part provide that the elevation is a downwardly projecting truncated cone with a circumferential collar or the elevation is arranged centrally of the cover surface, wherein the elevation is formed integrally with the cover surface and formed in the shape of a hollow hemisphere.

A practicable variant of the invention also provides that the depression is formed centrally of the covering surface, wherein a hollow pyramidal formation extends upwards in the depression. Also can the elevation may be formed centrally of the cover surface, wherein the elevation may take the form of a hollow closed cylinder.

Further advantageous embodiments of the ejektungsgemäßen nozzle top part may be such that the recess is arranged centrally of the cover surface, wherein the recess is in the form of an open hemisphere or round, wherein the roundish recess has a bottom.

Brief description of the drawings

Fig. 1

eine perspektivische Schnittdarstellung eines Bereiches einer Brennerplatte eines Holzvergaserheizkessels;

Fig. 2

ein herkömmliches Düsenoberteil; und

Fig. 3 bis Fig. 8

in perspektivischen Darstellungen und perspektivischen Schnittdarstellungen verschiedene Ausführungsformen des erfindungsgemäßen Düsenoberteils

An embodiment will be explained in more detail with reference to the drawings, wherein further advantageous developments of the invention and advantages thereof are beschirieben. It shows:

Fig. 1

a perspective sectional view of a portion of a burner plate of a wood gasification boiler;

Fig. 2

a conventional nozzle top; and

Fig. 3 to Fig. 8

in perspective views and perspective sectional views of various embodiments of the nozzle upper part according to the invention

Best way to carry out the invention

The FIG. 1 shows internal parts of a solid fuel kiln. This is preferably designed as Holzvergaserheizkessel. The boiler is provided with a combustion chamber 6 and an upper burner plate 12 below the fuels, not shown. In principle, the boiler comprises a primary air feed 1 and a secondary air feed 2. The burner plate 12 has an opening 3 for the afterburning of fuel gases of the fuels or wood pieces. In the area or above the opening 3 are glowing pieces of wood. The opening 3 is covered up to an annular gap 17 by a nozzle upper part 10.

The secondary air (8a) is supplied horizontally through the secondary air supply 2. The nozzle part 5 is also made in two parts. Below the upper burner plate 12 is at a distance another plate so that two plates are present, namely an upper burner plate 12 and a lower burner plate 13. Between the two plates 12, 13 flows horizontally, the secondary air (8a). The afterburned gases are guided and discharged through an afterburner chamber 4 located below the lower burner plate 13.

According to the invention, the opening 3 is followed by a thin-walled nozzle part 5, which can also be referred to as a burner pot. The nozzle part 5 tapers in cross section from the combustion chamber 6 in the direction of the afterburning chamber 4. The nozzle part 5 has in principle the form of a funnel or hollow truncated cone. The secondary air 8a passes through gas inlet openings into the interior of the nozzle part 5, where it is swirled and mixes with the gases or particles to be combusted.

According to the invention, the nozzle part 5 made of fire-resistant metal, in particular sheet metal. Thus, the wood embers disposed above the nozzle part 5 very quickly heat the nozzle part 5 and thus also the secondary air 8a, so that an optimal afterburning and a low environmental load are given.

Above the nozzle part 5 are formed in the annular gap in a circumferential edge web 8 window-like air inlet openings 7, through which the secondary air 8a enters the nozzle part 5. The window-like openings 7 need not be formed directly by the nozzle part 5. You can, for example, by tooth-like webs at the bottom the burner plate 12 are formed, wherein tooth spaces form the air inlet openings 7.

In order to achieve a stronger turbulence of the secondary air 8a, the nozzle part 5 is preferably equipped with external profilings, not shown, in particular air guide fins or vanes. The turbulences created in this way ensure more effective combustion. By using the fins 16, which are explained below, on the nozzle upper part 10, the openings 7 for the inflow of the secondary air 8 a and the design of the nozzle part 5, optimum turbulence and the gas path G indicated in the figure are achieved.

The burner plate 12 is preferably made of stone. But it can also consist of another heat-resistant material such as metal, in particular sheet metal. In order to keep ash on the burner plate, the upper burner plate 12 is provided with an upwardly directed collar 9. This is practically out of the burner plate 12, as the figure shows.

On the collar is the nozzle upper part 10, which is insertable into the arranged in the upper burner plate 12 first opening 3, wherein the nozzle member 5 as a nozzle lower part 11 surrounds a arranged on the lower burner plate 13 second aperture 14. The nozzle upper part 10 does not have to be connected directly to the nozzle base 11.

The wall thickness of the nozzle part 5 is less than 5 mm, in particular 1-3 mm. For example, the nozzle top 10 has a wall thickness of 2 mm while the nozzle base has a wall thickness of 1 mm.

The nozzle upper part 10, which can also be referred to as a turbo disk, is funnel-shaped with a downwardly projecting truncated cone with a peripheral edge, under which disks 16 are supported as a support. and air guide elements are formed, which are arranged in the annular gap 17 through which the fuel gases from the combustion chamber 6, together with the primary air, enter the nozzle part 5. The fins 16 are preferably not radially but slightly inclined to improve the turbulence. The fins 16 bear on the collar 9 and carry the nozzle upper part 10. Between the fins 16, the inflow openings 18 are formed for the fuel gas and primary air mixture. The nozzle base 11 is approximately funnel-shaped and has at its upper end also a circumferential, outwardly directed web 15 on which the openings 7 between the upper burner plate 12 and this web 15 are arranged.

It is also possible at least partially exhaust gas recirculation in the context of a recirculation burner. Exhaust gas recirculation can reduce the proportion of nitrogen oxides by cooling the flame and avoiding the development of excessive levels of nitrogen oxide. For this purpose, 13 inflow openings 19 are formed in the bottom region of the nozzle part 5 and in the lower burner plate 13. The exhaust gas enters an inner space 20 of the nozzle part 5 and flows out via outflow openings 21 and mixes with the fuel gas, the primary air and the secondary air 8 a in the flow area of the nozzle part 5.

FIG. 2a shows in perspective and FIG. 2b in a perspective sectional view of a nozzle top 22 according to the prior art. The nozzle upper part 22 has a planar covering surface 23 with a cross-sectional extension. Below the nozzle upper part 22, the fins 16 are formed as support and air guide elements in the edge region. The fins 16 may in principle be arranged radially, but they are preferably arranged not radially but slightly obliquely to improve the turbulence. Between the fins 16, the inflow openings 18 are formed for the fuel gas and primary air mixture. The cover surface 23 has a circular shape.

From the FIGS. 3 to 8 Various embodiments of the nozzle top according to the invention are apparent both in perspective views and in perspective sectional views. All embodiments of the nozzle upper part 10 according to the invention have in common that the covering surface 23 recesses 24 or elevations 35 has. It is also conceivable that the covering surface 23 of the nozzle upper part 10 has both recesses 24 and elevations 35. The nozzle upper part 10 according to the invention also has lamellae 16, which are arranged below the cover plate 23 in the edge region of the cover plate 23.

Even with the nozzle upper part 10 according to the invention, the lamellae 16 can in principle be arranged radially. Preferably, however, the lamellae 16 are arranged slightly obliquely in order to improve the turbulence here as well.

Various embodiments are conceivable for the nozzle top part according to the invention. In one of the embodiments shown here gem. FIG. 3 For example, the depression 24 may have a downwardly projecting truncated cone 26 with a peripheral edge 27 as a planar part of the covering surface 23, and the depression 24 may be integrally formed with the planar part of the covering surface 23. The elevation 35 can also be arranged centrally in the cover plate 23, which has a cross-sectional extension 32, the elevation 35 being in the form of a hollow hemisphere 28 (FIG. Fig. 4 ).

Further embodiments of the nozzle upper part according to the invention can be distinguished by the fact that the depression 24 is arranged in the center of the covering surface 23 and in the form of an open hemisphere 29 ( Fig. 5 ). According to the Figures 6a and 6b provides a further embodiment of the nozzle top 10 according to the invention that the Recess 24 is arranged centrally of the cover surface 23, wherein the recess 24 is formed round.

Further embodiments of the nozzle upper part according to the invention show the FIGS. 7 and 8th , In FIG. 7 the recess 24 is formed in the center of the cover 23. In the recess 24 is integral with the nozzle top 10, a hollow pyramidal molding 30 which extends upward. For this purpose, the formation 30 has a number of isosceles triangles 33, 34 which terminate in a common point and serve as side surfaces of the formation 30. Finally, an embodiment of the nozzle upper part 10 according to the invention provides that the elevation 35 is formed centrally of the covering surface 23 and is in the form of a hollow cylinder which terminates with a surface 25 (FIG. Fig. 8 ).

LIST OF REFERENCE NUMBERS

1

Primary air supply

2

Secondary air supply

3

first opening

4

afterburning

5

nozzle part

6

firebox

7

inlet openings

8th

edge web

8a

Secondary air

9

collar

10

Nozzle shell

10a

truncated cone

10b

surrounding border

11

Nozzle base

12

upper burner plate

13

lower burner plate

14

second opening

15

web

16

slats

17

annular gap

18

inflow

19

inflow openings

20

inner space

21

outflow

22

Nozzle shell

23

coverage area

24

deepening

25

area

26

truncated cone

27

edge

28

hemisphere

29

hemisphere

30

hollow pyramidal shape

31

cylinder

32

cross-sectional extent

33

triangle

34

triangle

35

survey

G

gas path

Claims (4)

1. A furnace for solid fuels, comprising a heating space (6) and a burner plate (12) located below the fuels, and comprising a primary air supply (1) and a secondary air supply (2), wherein the burner plate (12) comprises an opening (3) for the post-combustion of heating gases of the fuels by means of the horizontally supplied secondary air (8a), and the burned gases are guided through a post-combustion chamber (4) located below the burner plate (12) and are carried away, wherein

   - a thin-walled nozzle part (5) having a cross-section tapering from the heating space (6) towards the post-combustion chamber (4) is connected to the opening (3), the secondary air (8a) being horizontally supplied to said nozzle part via openings (7),

   - the nozzle part (5) is arranged close to the heating space (6) and is oriented towards the post-combustion chamber (4), and

   - the nozzle part (5) consists of a fire-resistant metal,

   characterized in that an upper nozzle part (10) is provided with a truncated cone (10a) for covering the opening (3) of the upper burner plate (12) in such a manner that an annular gap (17) is formed between the burner plate (12) and a circumferential rim (10b) of the upper nozzle part (10), wherein the upper nozzle part (10) is supported, in particular by means of fins, on a collar (9) which is oriented upward and projects beyond the burner plate (12).
2. A furnace according to claim 1, characterized in that the nozzle part (5) consists of sheet metal material.
3. A furnace according to claim 1 or 2, characterized in that window-like air inlet openings (7) are provided on the circumference of the nozzle part (5), the secondary air (8a) entering the nozzle part (5) via said openings.
4. A furnace according to any one of the preceding claims, characterized in that the nozzle part (5) is profiled, in particular provided with air guidance fins, for swirling the secondary air (8a), and/or the burner plate (12) consists of stone, of metal, in particular sheet metal, and/or is water-cooled, and/or the collar (9) can be releasably placed on or inserted into said burner plate and/or
   the nozzle part (5) consists of an upper nozzle part (10), which can be inserted in a first opening (3) arranged on an upper burner plate (12), and a lower nozzle part (11), which can be placed on a second opening (14) arranged on a lower burner plate (13), and/or
   the wall thickness of the nozzle part (5) is less than 5 mm, in particular 1-3 mm, and/or
   that the furnace is characterized by being designed as a wood gasification boiler.

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