EP1122495A1 - Device for incinerating biomass material in pulverized and solid form - Google Patents

Abstract

A blower device (48) produces a rotating fire circulation (90) in the combustion chamber (12). A build-up disc limits the blower device on the outflow side which it at least partly cuts off in front of the hot gases flowing back from the combustion chamber. A ring space radially surrounds the build-up disc and a mixture chamber (28) connects the combustion chamber with the flower device for flow purposes.

Description

TECHNICAL AREA

The invention relates to a device for burning Bio dust masses and bio solid masses.

Biomass for heating and thermal disposal are available, for example, logs, chips, Sawdust, wood chips, bio fine dust and bio coarse dust. The progressive development of manufacturing technologies in the wood processing industry has not only been shortened Workpiece run times, but also at a significant finer, dusty production waste, which in the Industry and craft today a share of 70 to 80% (Percent) of the wood residues. Another user Wood burning is the bakery trade. The combustion such residues is a challenge to the Firemaker. The regularly used grate with additional Primary air addition achieved in most combustion plants no longer the required low emission values.

STATE OF THE ART

To generate heat from biomass, push, slanted grate screw, Underfeed and dust injection furnaces as combustion systems known. With the previously known plant technology is the residual biomass, which is predominantly lumpy incurred, burned satisfactorily.

From EP-A-0 473 618 is a device of the beginning known type known, in which a helical gas flow is produced. For dusty fuels that very dry and their structures in most cases as "mandatory blowing" in the sense of the German standard TRD 414 "Wood firing on steam boilers" are classified or at least in the border area of this regulation are with the cyclone injection firing known from this publication a combustion in a rotating Movement creates, resulting in the exhaust gas values CO and total CO get good enough. This device is with a Link head blower equipped. The range of services corresponding Incineration plants range from 50 KW to 10,000 KW. The oil and gas combustion takes place predominantly in one rotating flame instead.

The dust ash (residual dust) and NO _x still present after the combustion are still the greatest challenge, however, if centrifugal separators of the above or comparable type are to separate the residual dust from the hot gases. Many known systems are operated with too much excess air during load operation. The consequence of this is that too large a quantity of flue gas flows through the boiler trains and the particulate matter, in particular, from the ember bed is entrained in strands and blown out. Retrofitting with a hose or electrostatic precipitator is often seen as the only, but very expensive solution to "remove" these dusts. In systems under 2,000 KW, however, the initial cost of a corresponding filter exceeds that of the boiler with the furnace.

PRESENTATION OF THE INVENTION

The invention is based, based on the task Prior art described above a device for burning bio dust and bio solids specify the least possible pollutants arise and be emitted.

This invention is characterized by the features of claim 1 given. Developments of the invention are the subject of Dependent claims.

The device according to the invention means for the woodworking Industry and the bakery trade a big one technical progress in terms of thermal Energy generation and disposal of residual materials.

Old and new biomass furnaces can be used with the Equipped or inventive device be retrofitted. Such a device according to the invention can with a through a frequency converter regulated link head blower according to EP 0 344 498 or with an impeller operated with perforated blading become.

The fresh air can be drawn in and in the shaft flange area be used for engine cooling. Fresh air can too fed to the blower area via separate suction openings, set in rotation and accelerated compactly. The accordingly rotating fresh air is then over a Annulus supplied to the mixing room, in addition from the Returned hot gas mixed furnace and then the Combustion process fed.

Through a spatially integrated combinatorial arrangement of the blower area and mixing chamber can be one in terms of component firmly connected "gas mixer tap" arise. The This gas mixer tap has a combustion chamber in terms of flow subordinate. The transition area or border area between this gas mixer tap and the combustion chamber preferably water-cooled. The coldest zone this gas mixer tap is located in the blower area. The the warmer zone lies in the mixing room. The one in the center of the mixing room The resulting gas swirl nozzle is the prevailing one Heat build-up (approx. 900 ° C (degrees Celsius)) of the downstream Combustion chamber exposed. The one in the mixing chamber radially rotating gas mass creates one in the center very strong gas vacuum - eye of an eddy current - what to a backflow of CO-containing hot gas from the furnace leads to the inner baffle plate, which for reasons of a increased thermal load designed as a heat shield can be. The CO-laden partial flow heats the gases in the Mixing room to approx. 200 to 300 ° C (degrees Celsius). In the border area between the mixing room and the combustion chamber In contrast, the temperature is around 500 ° C to 700 ° C (degrees Celsius). The energy once used for promotion and production the radial flow at the beginning of the process, which is gradual Temperature increase of the gases with the physically released Expansion forces clearly show that the device optimal continuous thermochemical combustion permits and ensures.

With a chain link arrangement in the link head blower to generate the rotating air mass at an external Flue gas recirculation in the blower area is comparatively little Fresh air needed. Such returned Rezigas (after Passed cleaned through a dust separator hot flue gas), which is low in CO, can Blower or supplied to the annulus and for Cooling be passed over the heat shield. This stabilizes radial flow in the mixing room. By concentrically tapering the mixing chamber, the rotating mixed gas combustion air constricted and in a spiral, coaxial radial flow targeted against the existing in the downstream furnace To be blown embers. However, it is also possible, the mixed gas combustion air through an annular gap, the one that delimits the mixing chamber on the outflow side and an annular wall having a central opening is not to be released constricted in the combustion chamber.

The communication zone created by the prior art link head blower the gas flow with the supply air respectively Ambient air is present in the peripheral area of the annulus the inside of the chamber wall. The created according to the invention Communication zone is with a however, significantly improved efficiency at the end of the new existing mixing room according to a first embodiment of the invention in the cross-sectional area of the as a swirl nozzle acting gas passage opening in the area of a concentric Rejuvenation of the mixing room in its transition to Combustion chamber, or according to another embodiment of the Invention in the annular gap of the gas passage opening containing ring wall.

An accelerated, compressed and constricted mixed gas combustion air after passing through the swirl nozzle suddenly relax in the downstream combustion chamber. The around the eye, the center of the axis of rotation, stable rotating mixed gas gas roller (fire roller) can then be targeted end over an ember bed surface; the peripheral area this fire roller communicates with the carbonization gas above the ember bed in the flame area of the burnout zone and displaces the entire volume of the hot gas mass in the furnace in a smooth, endlessly rotating movement. this leads to an optimal and rapid release of methane gases the biomass. The remaining hydrocarbons in the charcoal-hydrocarbon mixture can later in Anneal the hot gas area with the necessary dwell time. The Combustion is particularly optimal when the flame roller or fire roller little contact with the walls of the Combustion chamber.

1. die Flammentemperatur im Feuerungsraum wird abgesenkt,

2. die NO_x-Emission wird dadurch um ca. 30 % reduziert,

3. die Verbrennung kann je nach Brennstoff mit wenig Luftüberschuss betrieben werden,

4. der Staubaustrag wird reduziert und der Wirkungsgrad der Anlage verbessert.

The internal, central recycle gas return to the inner heat shield, which cools it, and an additional or alternative admixture of the recycle gas to the fresh air, mixed as combustion air before passing through the swirl nozzle, has the following advantages:

1. the flame temperature in the furnace is reduced,

2. the NO _x emission is thereby reduced by approx. 30%,

3. Depending on the fuel, the combustion can be operated with little excess air,

4. The dust discharge is reduced and the efficiency of the system is improved.

The hot gas roller generated in this way can be existing or retrofitted combustion rooms a stepless Low-emission combustion of biomass in the control area from 30% to 100% with the necessary temperature mixing and dwell time too. By changing the cross sections from the inner heat shield or the swirl nozzle can the spiral radial flow in the furnace the respective requirements, especially the The location, shape and size of an ember bed can be adjusted. The resulting spiral, rotating radial flow fire roller may last longer through these changes and more constant or shorter and more unstable with regard to them Rotational form can be designed.

The device according to the invention can be vertical, horizontal or diagonally, as injection and / or underfeed firing be trained.

By placing the device in a suitable place to Example on the side above the ember bed in the flame area the spiral-shaped combustion air roller is targeted end of the ember bed surface. The amount of dust from the combustion material remains oppressive as it were the mixed gas fire roller in the ember bed lie. That means that in the over the ember bed rotating fire roller there is hardly any residual dust. The Residual dust discharge is therefore very low. The combustion can therefore be influenced and regulated in an optimal manner become.

When burning lumpy wood in the baking room, for example in a well-known wood-burning oven (length approx. 2.5 m (Meters), width about 1.8 m, height about 0.25 m, without grate) at the same time the combustion chamber is spiraling rotating fresh air to the side of the ember bed in the outflow area of the burning biomass. The one time generated rotating gas or fire roller is regardless of the speed of circulation and is always available and visible.

Known roller or moving grate furnaces that use the fuel when burning and keep moving mostly large open spaces above the ember bed. During partial load operation Such systems become the large embers bed by reducing the combustion air bad with oxygen provided; mixing takes place only to a limited extent. The outflow of unburned gases can be practical cannot be prevented. With the device according to the invention refurbished moving grate furnaces, however, remains Firewheel is very visible. During low load operation you can see that the ember bed glows yellow to bright red is preserved and does not die black, what a is a visible sign of optimal combustion. The Fire roller presses the existing one in front of the ember bed Heat build-up against the ember bed and thus ensures even with partial load operation for sufficient air supply.

In systems according to the invention with a feed screw are equipped and accordingly No rust is required when fuel is inserted. A secondary air addition and part of a primary air addition can be done via the swirl nozzle, in one Spirally rotating gas roller in the axial outflow direction towards the ember bed. Another primary air addition in the The front lower ember bed area can be inserted via gas blow-out nozzles take place in the front wall of the outer Heat shield can be placed. Your air jet can then end and act in the ember bed in the axial outflow direction, especially in the lower area of the ember bed.

With coarse or fine dust injection furnaces, the dust becomes the Spirally rotating gas roller added via injection nozzles. Dusts with a large coarse fraction are preferred tangential in the wall area - with 15 ° (old degree) to 45 ° (Old degree) inclined to the center axis - blown in. For As a rule, the ignition must be in the downstream cyclone furnace a gas or oil pilot burner can be placed that the Combustion monitored for safety reasons. Finer, drier The proportion of dust burns immediately. The one that is released Heat build-up, visible as a flame in the ignition area, stabilized the cracking phase of the coarser residual dust in the Rotation decreasing, becoming more unstable, always visible permanent, endlessly rotating, cyclone-like fire roller. However, a downstream one can be used in such dust injection furnaces Dust filter, especially in larger systems, become necessary.

In one embodiment, which is also shown in the drawing, the baffle plate, which is designed as a heat shield in the present example, has a central opening. The gases flowing back from the combustion chamber into the mixing chamber are not completely diverted radially outwards on the baffle plate, but rather flow partly directly into the blower device and then back into the mixing chamber via the annular space. This has a stabilizing influence on the rotating gas roller in the mixing room and can also be referred to as internal NO _x reduction.

Further features and advantages of the invention result from the claims, the description and the drawing.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1

einen Schnitt durch eine erfindungsgemäße Vorrichtung,

Fig. 2

einen Schnitt durch ein bei einer Vorrichtung ähnlich der von Fig. 1 zu verwendendes, mit einer zentralen Öffnung versehenes Hitzeschild,

Fig. 3

einen Querschnitt längs der Linie A - A der Fig. 1,

Fig. 4

eine Ansicht "x" der Vorrichtung gemäß Fig. 1,

Fig. 5

eine Vorrichtung ähnlich der von Fig. 1 mit einer zusätzlichen Staubeinblaseinrichtung,

Fig. 6

eine Seitenansicht eines Holzkessels mit einer Schnecken-Unterschubfeuerung und mit einer integrierten, erfindungsgemäßen Vorrichtung,

Fig. 7

einen Schnitt durch eine weitere Ausführungsform einer erfindungsgemäßen Vorrichtung,

Fig. 8

eine Vorrichtung ähnlich der von Fig. 5, aber mit einer andersartigen, dezentralen Staubeinblaseinrichtung und mit einem Ringspalt in der den Mischraum abströmseitig begrenzenden Ringwand, und

Fig. 9

einen Schnitt längs der Linie 9 - 9 von Fig. 8.

The invention is described and explained in more detail below with reference to an embodiment shown in the drawing. Show it:

Fig. 1

2 shows a section through a device according to the invention,

Fig. 2

2 shows a section through a heat shield to be used in a device similar to that of FIG. 1 and provided with a central opening,

Fig. 3

2 shows a cross section along the line AA of FIG. 1,

Fig. 4

2 shows a view "x" of the device according to FIG. 1,

Fig. 5

1 shows a device similar to that of FIG. 1 with an additional dust injection device,

Fig. 6

2 shows a side view of a wooden boiler with a screw-type underfeed firing and with an integrated device according to the invention,

Fig. 7

3 shows a section through a further embodiment of a device according to the invention,

Fig. 8

5 shows a device similar to that of FIG. 5, but with a different type of decentralized dust blowing device and with an annular gap in the annular wall delimiting the mixing chamber on the outflow side, and

Fig. 9

a section along the line 9 - 9 of Fig. 8th

WAYS OF CARRYING OUT THE INVENTION

A furnace 10 is used to burn bio-dust and bio-solid masses. The furnace 10 has a combustion chamber 12 in which solids 14 (Fig. 6) can be burned.

A gas mixer tap 20 produces a gas roller 90 and represents a compact unit, which in one in the Wall 22 of the furnace 10 existing breakthrough 24 is used gas-tight. The gas mixer tap 20 has an outer housing wall 26 in its central area is of circular cylindrical shape and has a mixing space 28 enveloped in a cylindrical shape. On their, related to the The combustion chamber 12, on the side facing away, is the housing wall 26 closed by a rear wall 30. In the rear wall 30 is a central opening in which a shaft 32 is rotatably supported which is about a motor drive 34 about the longitudinal axis 36 of the gas mixer tap 20 are set in rotation can. In the present case, two rings are on the shaft 32 attached by chain links 38, 40, which together with the Shaft 32 can rotate about the axis 36. The wreaths are movably attached to the shaft 32. In the present example are the chain links 38, 40 also with each other moveable.

In the area of the chain links 38, 40 one protrudes through the Rear wall 30 feed line 42 passed through. This Feed line 42 defines a suction opening 44 for in the Area of the chain links 38, 40 fresh air to be introduced and Rezigas. The area of the chain links represents the Blower section 46 of the essentially from the chain links 38, 40 and the drive 34 existing fan 48.

Downstream, in the transition area between the blower area 46 and the mixing chamber 28, is a central heat shield 50 available. The heat shield is on its upstream side 50 enclosed by a housing 52. In this case 52 a line 54 projects into the fan area 46 and pierces the rear wall 30. The opening 56 of this Line 54 provides a suction opening for fresh air and Rezigas represent. Fresh air and Rezigas can thus through the Line 42 (in the blower area 46) and through the line 54 (in the area of the housing 52 of the heat shield 50) be initiated in each case.

The housing 52 has opening slots 58 through which the in the housing 52 introduced mixture of fresh air and Rezigas can exit radially in an annular space 60, which Radially surrounds heat shield 50. The annular space 60 is therefore formed between the heat shield 50 and the housing wall 26 and provides the flow connection to the Mixing room 28 represents.

The gas mixer tap 20 ends with the combustion chamber 12 an annular wall 70, which is designed as an outer heat shield is. The ring wall 70 has a central opening 72 The inside of the ring wall 70 is in a smooth transition connected to the housing wall 26. This on the ring wall 70 adjacent housing wall area 78 is with the housing wall 26 connected in one piece. The metallic in the present case Housing wall 26 thus forms a in the area of the ring wall 70 inner lining of this ring wall 70. On the in Fig. 1st right side of this ring wall 70 is the Furnace 12, as schematized in particular in FIG. 6 can be seen.

In contrast to the full-area shown in Fig. 1 Heat shield 50 is shown in section in FIG. 2 Heat shield 50.2 has a central opening 62. This allows a certain flow balance between the Blower area 46 and the mixing room 28 take place. Instead of An opening 62 can also have a plurality of openings arranged his.

In the furnace 10.5 shown in FIG. 5 the bio-dust masses supplied via an injection line 18 (Arrow 16). The injection line 18 is in this embodiment Part of the gas mixer tap 20.

The injection line 18 projects largely centrally through the Mixing chamber 28 and ends in the area of the opening 72. With its other end area it pierces the heat shield 50 and its housing 52 and ends outside the rear wall 30th

The furnace 10 or 10.5 works do the following:

Rotation of the chain links 38, 40 produces a rotating air roller in the area of the annular space 60, which continues on the inside of the housing wall 26 through the mixing space 28 as a gas roller 90. In the region of the opening 72, this gas roller 90 is constricted centrally (gas roller 90.2). In the area of the combustion chamber 12, this gas roller 90.2 relaxes more or less suddenly outwards. As a result of the temperatures prevailing in the combustion chamber 12, a radially expanding hot gas roller (fire roller) 90.4 is formed, which ends above the ember bed of the solid mass 14 (FIG. 6). As a result of the strong rotation of this gas roller 90, 90.2, 90.4, a considerable negative pressure is formed in the area of its axis of rotation. This causes a gas backflow (arrow 100), which returns the CO-laden hot gas as a partial flow from the combustion chamber 12 into the area of the mixing chamber 28. This gas backflow 100 heats the gases in the mixing room to approximately 200 to 300 ° C. (degrees Celsius), the gases in the area of the opening 72 to approximately 500 to 700 ° C. As a result of the rotation of the gas roller 90, this gas backflow 100 likewise gets into a rotating flow form 102. In the area of the heat shield 50, the gas backflow 100 is deflected completely outwards (arrows 104) and mixes with the gas roller 90. In contrast, the heat shield 50.2 (FIG 2) a central portion of the gas backflow 100 into the blower area 46. In addition, fresh air and waste gas are introduced into the annular space 60 through the lines 42, 54 and from there are likewise fed to the gas roller 90. The CO portion of the gas backflow 100 reacts with the oxygen (O ₂ ) of the combustion air. The low-oxygen combustion air thus enables a combustion process with internal NO _x reduction. Finally, dust 16 can be fed through the injection line 18 to the gas roller 90.2 and thus also to the hot gas roller 90.4 (FIG. 5).

In the area of the mixing chamber 28, the supply line prevails of fresh air and Rezigas lower temperatures than in the area of the furnace 12. In addition, in Mixing chamber 28 an intimate mixing of the fresh air supplied and the fuel cell with that from the combustion chamber 12 backflowing hot gas mixture instead. Together with the Arrangement of the only having a central opening An extremely stable gas roller is created on the outer heat shield both in the area of the mixing room 28 and in the area of the Furnace 12, even with up to 30% reduced Part load operation.

In the present case, there are two more in the wall 70 Openings 110 are present (Fig. 4) through which air from the Mixing room 28 in the furnace 12 as a result of the Gas roller 90 flow through the gas flow generated in the mixing chamber 28 can. The openings 110 are aligned such that this gas flow additionally directed into the combustion chamber 12 (Primary air) in the direction of the solid mass 14 or whose embers bed 112 is directed.

In the embodiment variant shown in FIG compared to the embodiments shown in FIGS. 1 and 5 comparatively very thick wall 70.7 available. This allows one to be constricted longer in the direction of flow permanent gas or fire roller 90.4 achieve.

In the furnace 10.8 shown in Fig. 8 is the existing in the furnace 10 described above Ring wall 70 as relatively far into the combustion chamber 12 protruding pipe or duct piece 70.8 formed. In addition, between this pipe section 70.8 and the wall 22 delimiting the combustion chamber 12 is an annular gap 116 available. The injection line, which in Fig. 5 in the Mixing chamber 28 protrudes in this furnace 10.8 outside of the gas mixer tap 20 by being protrudes through the wall 22 and outside the pipe section 70.8 ends directly in the combustion chamber 12. Your end Injection nozzle for introducing coarse and in particular also Particulate matter in the combustion chamber 12, and thus its outlet opening 118, is aligned in the combustion chamber 12 in such a way that the dust 120 parallel to a pipe section 70.8 concentric can flow out surrounding circular cylinder. there this dust 120 flows when leaving the outlet opening 118 obliquely to the longitudinal axis 36. In Fig. 8 that is in the direction the directional component pointing the longitudinal axis 36 and in FIG. 9 the directional component oriented at right angles to it the dust movement is shown schematically. On this is an intimate mixing of this dust 120 with the outside of the pipe or duct section 70.8 forming fire roller 90.8 given below is described in more detail without the blown in Dust flow with the gas backflow (arrow 100) could collide.

Due to the annular gap 116 that in the mixing chamber 28 becomes forming gas roller 90 no longer constricted, like that is the case with the above embodiments. The on the outer housing wall 26.8 of the gas mixer tap 20 in Mixing chamber 28 existing gas roller 90 rather flows through through the annular gap 116 and into the combustion chamber 12 inside. As with the previous embodiments due to the formation in the mixing chamber 28, caused by the rotation of the gas roller 90 vacuum a gas backflow (arrow 100) from the combustion chamber 12 in effects the mixing chamber 28 into it. Because of the in the mixing room 28 existing rotating gas flow of the gas roller 90 the gas backflow is also set in rotation. The Gas backflow is schematized with a rotation spiral 100.8 shown. This gas backflow laden with CO mixes in the mixing chamber 28 with the rotating Chain links 38, 40 fresh air drawn in and recirculated Rezigas, as already described above.

This furnace 10.8 is based on the knowledge that a coarse and fine dust combustion does not constrict the Gas roller, as described in Figures 1 to 7 is needed. By direct derivation of the in the furnace 12 gas roller 90.8 becoming the fire roller over the Annular gap 116 flows the combustion air outside of the Pipe or duct section 70.8 in the furnace 12. The coarse and fine dust 120 is ignited immediately after leaving the injection line 18.8 and thus after flowing out of the outlet opening 118. The 90.8 in the rotating gas or fire roller in the combustion chamber 12 immediately released heat accumulation a quick and optimal combustion without coarse ash and Slag formation. The combustion chamber 12 is due to the prevailing high temperatures lined fire-proof.

The internal Rezigas recirculation and the NO _x reduction take place in the same way as in the glow bed combustion plant described above in connection with FIGS. 1 and 7.

The externally recirculated flue gas with its oxygen content contributes all the more to NO _x reduction, the more unburned hydrocarbons (CO) are still present in the externally recirculated regas.

Claims (21)

Device (10) for burning bio-dust masses and bio-solid masses (14, 16), with a furnace (12), a blower device (48) for generating a rotating fire roller (90) in the furnace (12), a baffle plate delimiting the blower device on the outflow side for at least partially shielding the blower device (48) from hot gases flowing back from the furnace (12), an annular space (60) radially surrounding the baffle plate, a housing wall (26) surrounding the annular space (60) on the outside, characterized in that A mixing chamber (28) is present between the combustion chamber (12) and the blower device, via which the blower device is connected in terms of flow to the combustion chamber (12). Device according to claim 1,
characterized in that the mixing chamber (28) has a cross-sectional taper on the outflow side with an approximately central gas passage opening (72). Device according to claim 2,
characterized in that Gas outlet openings (110) for air are present in the annular wall (70) of the mixing chamber (28) delimiting the gas passage opening (72) such that the air flow is directed out of these gas outlet openings (110) to the ember bed (112) present in the furnace. Device according to claim 2 or 3,
characterized in that an annular gap (116) for a gas roller (90.8) flowing from the mixing chamber (28) into the furnace (12) in which there is an annular wall (70.8) of the mixing chamber containing the gas passage opening (72). Device according to claim 4,
characterized in that the annular wall is designed in the manner of a pipe or duct piece (70.8) projecting into the combustion chamber (12). Device according to one of claims 4 or 5,
characterized in that the pipe or duct piece (70.8) is cooled, in particular water-cooled, is formed. Device according to one of the preceding claims,
characterized in that the baffle plate is designed as a heat shield (50). Device according to one of the preceding claims,
characterized in that the baffle plate or the heat shield (50) is partially gas-permeable. Device according to claim 8,
characterized in that at least one central opening (62) is present in the baffle plate or in the heat shield (50.2). Device according to one of the preceding claims,
characterized in that there is a feed line (18, 18.8) for supplying coarse dust and fine dust into the combustion chamber (12). Apparatus according to claim 10,
characterized in that the feed line (18) for coarse dust and fine dust (16) opens into the mixing chamber (28) or into the area of the gas passage opening (72). Apparatus according to claim 10,
characterized in that the supply line (18.8) for coarse dust and fine dust (120) opens into the combustion chamber (12). Device according to claim 12,
characterized in that the end region of the feed line (18.8) for the dust (120) with its outlet opening (118) is aligned approximately parallel to the wall of the pipe or duct piece (70.8), so that the dust (120) is concentric to the longitudinal axis (36) of the Pipe or duct piece (70.8) aligned circular cylinder wall flows out of the outlet opening (118). Device according to one of the preceding claims,
characterized in that the blower device (48) has at least one suction opening (42, 56) for fresh air. Device according to one of the preceding claims,
characterized in that the blower device (48) has at least one suction opening (42, 56) for recycle gas. Device according to claim 1,
characterized in that the housing wall surrounding the annular space is also present in the area of the mixing space (28) as an outer boundary wall such that a structural component for producing the fire roller (90) is present. Device according to claim 16,
characterized in that the housing wall (26, 78) extends as far as the gas outlet opening (72). Device according to one of claims 2 to 13,
characterized in that the annular wall (70, 70.8) delimiting the gas passage opening (72) is designed as an outer heat shield. Device according to one of the preceding claims,
characterized in that the blower device (48) has a blower wheel (32, 38, 40). Device according to claim 19,
characterized in that the impeller has a central hub (32) and vane-like elements (38, 40) movably attached to the hub. Device according to claim 20,
characterized in that the blade-like elements each have mutually movable members (38, 40).

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