DE2351094A1 - PROCESS AND DEVICE FOR MIXING A GRAINY MIXTURE, SUCH AS IN PARTICULAR ROCK CHARTS AND THE LIKE, WITH A BITUMINOUS BINDING AGENT - Google Patents

Description

Patent notification

of the company ι

Ironworks Union ¥ est ± 'alia, 4628 AItIUTs

Method and device for seeing a granular ^1st "Geuer-pey, such as stone chippings and the like, with a bituminous /;

binder

The invention relates to a method and a device for mixing a granular rock, such as in particular stone chippings and the like, with a bituminous binder, whereby for the \ / "liquefying of the binder and for coating the granular mixture with de / u binder the 1- jungle untci 'simultaneous hot air supply is produced »

In the well-known method of mixing, the granular mixture is used

409816/093

thoroughly dried on a regular basis before it is mixed with the binding agent. This leads to the fact that the dust and JFine-grain constituents of the mixture in considerable quantities escape from the heat chamber before the binder becomes liquid and binds in the mixture. Expensive dust collection devices must therefore be provided.

The invention is based on the object of creating a method which overcomes these disadvantages of the known methods have it effectively remedied. Furthermore, the invention aims to provide an expedient device for carrying out the Procedure.

The method according to the invention is characterized in that that with the initially cold granular mixture, so much water is supplied to the mixing space that the water contained in the mixture Dust material before it is bound by the liquefying binding agent by the hot air supply forming water vapor is prevented from being entrained by the hot air stream. A thorough bond of the dust material through the developing water vapor, it is advisable to measure the water content of the granular mixture to a value of about 0.02 to 15% by weight, preferably 5 wt .-% or higher, based on the weight of the Mixture, discontinue. It can be useful to premix the material to be mixed with the hot air before it is heated for largely uniform water penetration of the mixture perform. When using a rotating Kischer

409816/0938

its speed of rotation during premixing is expediently selected to be lower than during the subsequent hot mixing process. During the hot mixing process, the rotational speed is advantageously between 50 and 30%, preferably around 70% of the centrifugal or centrifugal speed, while in the case of door mixing, the rotational speed can be approximately 5 to 30% of the centrifugal or centrifugal speed.

To carry out the method according to the invention, a device can be used with advantage that has a between one horizontal misclip position and one inclined Emptying position pivotable. Mixer in connection with a charging device for charging the mixer with the granular mixture and the bituminous binder as well as with a hot air generator that is used for supply the hot air to the mixer located in the mixing position is connected to the mixer via a feed channel and is connected to an exhaust air duct to discharge the hot air from the mixing room. Preferably there is the mixer from a rotating Irommel or the like. That, as well like the hot air supply duct, with thermal insulation can be provided.

The loading device can be arranged to load the mixer in an inclined position which corresponds to the emptying position or at which the tilt angle of the mixer relative to the horizontal is somewhat

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is smaller than in the emptying position.

The binder can be in liquid form via an injection nozzle or the like. or can be introduced into the mixer in solid form. It is also possible to use a filler or a filler in powder form corresponding to the binder via an introduction nozzle, an introduction nozzle or the like. to introduce into the mixer. Instead, the filler can also be introduced in the form of a slurry, in which the powder is mixed with the water required to moisten the granular mixture. The binder and the filler can be fed in when the mixer is tilted or tilted. But it is it is also possible to introduce the binder and the filler into the mixer after it has returned to its horizontal working position has been postponed. The filler can also be used in a filling vessel or the like. located granular mixture can be added.

The device according to the invention can also be designed so that the mixer can be loaded in its horizontal position. In this case, a movable, endless feed conveyor can be provided which, during the feed process, can be introduced with its discharge end into the feed opening of the mixer. On one side of the conveyor frame, its outlet nozzle _{9 can have} an outlet sirate ocLdglo for the aiifgesoliaolssne binding agent; ssin- The SOrdersr can mx ^- 'j an Abdesfanig or

i> 09816 / 092S

Cover hood or the like. strand, be, through which the outlet a filling vessel, hopper or the like. for the grainy mixture grasps through.

The mixer can be open at both ends so that the Hot air flows through the mixer from one end to the other. On the other hand, the mixer can only work on its to be open to one end; in this case, the opening serves both for the introduction and for the discharge of the hot air.

If cooling of the mix is required, can a fan can be provided which guides unheated air through the mixer. In some cases, the arrangement of a fan can be dispensed with. Any cooling that may become necessary can be brought about by that with the heater set to a low flame, a secondary air flow is passed through the mixer.

If the water content is evenly distributed over the whole granular mixture, the heating of the mixture and of the binder use at the same time as the mixing process. Otherwise, it is advisable to start with the cold mix premix to prevent dust and fines be discharged from the mixing chamber with the hot air flow O

It is recommended * to heat the granular aggregates and the binding agent in such a way that these _{mixed materials are continuously}

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are rolled and thereby form a continuously falling mix. Although jumps, x-jie, for example, jacks and the like can be arranged on the inner wall of the drum, which take the mix with them into the upper drum area as the drum rotates, it is preferable if the arrangement of such projections and entrainment members starts which the Hischgut can caking is omitted and is instead uses a drum having a Im. liesentlichen smooth and even inner wall. This drum is driven at such a high rotational speed that the material to be mixed inside the drum becomes one. Mixture forms a veil. During the trip, the rotational speed is 50 to 90%, expediently 70? &, The Zentrifugalbzw. Spin speed.

At the beginning of the heating of the material to be mixed, the amount of ice air flowing through the mixer can be adjusted as a function of the tendency of the material to be carried away by the air flow. This means that at the beginning of the heating process, the air flow rate is kept small if there is a risk that fine material will be carried along by the air. The amount of air is then correspondingly increased with increasing softening and liquefaction of the binding agent and accordingly with increasing binding of the fine material by the binding agent. Observation of the exhaust air leaving the exhaust air duct; be made. It is also the liöglieMreit _f the air volume control automatically

408816 / Q938

table depending on the emerging from the mixer The amount of dust carried by the air The amount of dust is determined e.g. by means of a load or cooling device arranged on the exhaust air duct. The amount of air can be adjusted by adjusting a throttle member arranged in the exhaust air duct, by changing the speed of a fan supplying the air to the heater or by changing the fuel supply to the heater, if necessary also by combining these different measures, regulate.

The supply air duct through which the air is fed to the mixer can, according to a further feature of the invention, be connected to one end of a double-walled duct which consists of an outer pipe and an inner pipe located therein, both pipes being made of a non-refractory and non-refractory duct. heat-retaining material are made, such as Z ₀ B ₀ stainless steel. The arrangement is so made ₉ that ctarch the annular channel between the two tubes secondary air flows to the burner _t which at the same time the inner tube kühlt9 in which the burner flame befindete If the mixed material to be cooled _9, the burner can contact set to a small Plamme * Di © Secondary air then flows through the above-mentioned hanging duct in such a way that it cannot be blended with the Misclaei? Also, if necessary, a small amount of secondary air can still flow backwards in Hichtmig aiaf the mist, in order to prevent the interior roller from being transferred through the distillery on display »

4 O 9 8 1 6 / O 9 3 p

2351Q94

Further features of the invention emerge from the individual Claims and the following description of the exemplary embodiments of the invention shown in the drawing. In the drawing shows:

Hg. 1 in side view a device for coating granular materials, such as gravel material, stone chippings and the like. As used in road construction;

Pig. 2 in axial section a double jacket channel for supply from secondary air to a burner and hot or cold air to the mixer;

Pig. 3 shows a second exemplary embodiment in side view

the device, only the main parts of which are shown;

Pig. 4- also in a side view of a third embodiment the facility in a partial representation.

The device shown in Pig "1 is used for coating" of _grit% gravel or other granular material for road building or "by-production of a bituminous Straßenaeöken. ,, Bie binder device comprises a frame 1 on which by means of an _X-s astwagens or a STigfaiir-asugss gtt dsr respective application site liinsjsf@lh.rsn ^ © Sidsii kami _n - ^ n el® :? ^ s s hot © Misehetife ^ ym des iseller- amsgstssgan irii ^ do Dss Hiseheai 2 is on © i ~

Ξ.Θ2: ΊΠΓα © 2? 32ΐ B1Ü1J13 30 ds: s

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Drum 3, which is frustoconical on both sides. At one end of the drum is the feed opening 4- _o The inside of the drum is smooth and flat and has here with the exception of screws or ringsj which are located in the frustoconical part 7 _? no lifters or other take-away devices. The mentioned augers prevent the mix from falling out of the emptying opening 5 of the drum when the latter is at rest and is inclined or tilted rotatably mounted about its axis. It shall be driven by a hydraulic motor via a gear, the drum supporting frame 8 is pivotable or between supports 10 = tiltably mounted β on both sides of the frame 8 engages a hydraulic cylinder 11 at _o By means of the cylinder can therefore be the barrel of a position _s in extending tilt the drum axis R horizontal ₉ in a feed position in which the drum axle ₉ as R1 indicated inclined ₉ is "on a stage 31 at the one end of the frame is an air heater 12 mounted in the preferred embodiment, the air heater Fired by means of an oil or gas burner 32 whose burner flame, adjustable in intensity, burned in a combustion chamber, through which air is passed by a fan = the heated air flows through a supply duct 13 is the MiBv-hs: ..-, -

499816/0938

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The mouth of the supply air duct 13 is arranged so that it is aligned with the opening 5 of the drum _? . The axis of rotation of the drum is in a horizontal position. The supply air duct 13 is connected to a chimney or an exhaust pipe 14. A throttle valve is arranged in the supply air duct which can be adjusted so that the hot air from the heater 12 flows over the supply air duct 13 of the drum 3 flows in and is discharged in the other pail via the exhaust pipe 14. At the other end of the frame 1 is an expansion _{space 18 arranged 5} whose inlet opening is aligned with the drum opening 4 when the axis of rotation of the drum is in its horizontal position The expansion chamber also had an outlet with which it is connected to a fan 16, which blows out into a duct or exhaust pipe 19 has in its lower area an ^{opening that can be closed by a door ododglo x r} srelsel, ώε gathers here! to be able to remove particles of matter.

One (??? In ölargestelltisi dec not drawing) serves conveyor ZVx sales BSU "cliargentfeisen Bexördeiraiig of ungeiteoslsieten granular SsissngeE in a ¥ ags = JPäilgefäß or 22 _f, which with a iliisfeagsseirar-rs 221 Terselien Is ^- S ₅ dsr-eii Aus— ööffsizn ^ Ei ^- S ^- GeIs einea hood-like n ¥ ersslilii £ organ5: sE'bsz ¹ is'bc The Selxarss 221 is'fe so sngscx-dne ^ .- clsE

4OSS IS / 0933

the granular mix located in the milling vessel 22 over a pivotable feed chute 222 into the opening 4 of the Drum is inserted »

On the upper stage are containers for holding the molten binder, a powdered filler and a flow oil. Pipelines connect the containers with outlet openings _? through which the substances mentioned are introduced into the drum. The exit soff mangen for the binder and the iiiller may be arranged inside the feeding chute ₉ 222 so that these substances are supplied under gravity, x-Xenn check is the drum in its tilted position. Static which, at least the outlet opening for the binder, together with those ₉ that it flows to its inlet opening to be arranged for the passage of oil in the interior of the expansion chamber 18 so and a specific metered binder! Amount under the action of the air pressure A further outlet opening is connected to a Connected to water and arranged in such a way ₉ that the granular Miseligirfe (sapwood or other 6-stone seed material) is "washed with water before it gets into the SroBamsl? _O

The work-fesx-jeipe of the introductory described Einriekinmg is i-ji © follows s

The necessary% © n sorts of a moist isosiiigen ifeterial from a storage place ₉ the g _o 3 _o iron one of the l-iltte

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storage piles exposed to tion are formed, loading vessels fed, from which the different types of grain or grain classes are drawn off onto a conveyor belt. hit Using weighing devices, such as belt weighing feeders, or by means of volumetric measuring devices the proportional composition of the batch consisting of the different grain classes can be determined via the conveyor belt Determine the feed mix. The water content of the individual grain classes is determined by means of moisture indicators measured, e.g. arranged on the charging vessel taking into account the water content when weighing the proportions of the various grain classes to ensure that the dry weight of the granular mixture complies with the relevant regulations. It it has been shown that the coating of the granular substances with the liquefied binder by the hot mixing Presence of the water is promoted as the water has the fluidity and the flow rate of the liquid Binder improved. In addition, through the water the Effectiveness of the binding agent on the constituents of the granular mixture "favored. The water content of the Oiiarge the granular mixture can with the help of the water spray of the G-e-Msnges d®a "depending on requirements so

s'äell ^i? 5 Wsrdsn ^ that se ¹ swiseii®a 0 _f 02 and 15 (rew .-% lies ;, s ^ reis® Eindss'ösns 3 ¹ S-OW ₀ = f5 foefeagii _β Hex

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is discharged from the mixing room. In view of this, it is advisable to soak the granular mixture as evenly as possible with the water so that there are no major deviations in the moisture content. If even moisture penetration can be achieved _? Before the granular mixture reaches the mixer, this means a time saving in the mixing process, since in this case a previous cold premix can be dispensed with.

The burner is first set to a small flame. The throttle valve 113 is set so that undesired hot air generated by the burner is discharged via the exhaust air duct 14 x ^ ird. The fan therefore works load-free = Die OJrommel is in its inclined loading position R1.

When the weighing container is full, the hood closure and the feed chute 222 are swiveled into the open position so that the granular mixture is discharged into the drum. The "monitoring system then closes the shutter 122 and the feed chute and signals are delivered ₉ which request the next batch and pivot the mixer into the horizontal mixing position with the aid of the cylinders 11" The binding agent can be added to the granular mixture ₉ when the! Drum in its tilted position or in the horizontal position "is located!" _C , j © after ₉ where the iiis - fei'ti'iJS = - mid ZmfüliCTmgspifnimg fts the binder is =

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The motor 9 is put into operation, causing the drum is rotated clockwise.

If the mixture is unevenly moistened, it is advisable to carry out a cold premix before the hot mixing is carried out. In this case, the drum is rotated over a period of about five to ten seconds with the throttle valve setting unchanged in order to achieve a uniform transparency of the mixture . It may be expedient here _s to drive the drum at a comparatively low rotational speed, between 5 and 30% is the Schleudergesehwindigkeit, so that the granular mixture in the bottom region of the mixing drum undergoes a tumbling or overturning. During this stage, hardens in contact with the cold, moist binder, which also cools the drum itself, resulting in a cold mix of the granular mix and solidified binder particles »The first mixing stage is now over.

The control and monitoring system now sets the burner to full I ¹ lam? At the same time, the throttle valve 113 is switched on, so that mm of hot air from. the Ifaf'csriaitzsr- through the sicli dreiienae! r-ossiel sfeSario behind- the- Sr-osMel wi ^ d cLi® IßxS'b überea? den JLBstigiiixaiisl 19 in the JL '& moSphere s ^ gelsi «= OS'S ο ¥ enn" at cLsi? BssoliiöiriiLg dsr Siroiaiael das iiornigs Sessi ^ - gi a 3lsicSsii. 304 "3J'3ii.Gl;"sd'. igli: "sd '. j aiifwsiis ^ _; can from q / sl

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the loading can be carried out.

During the hot mixing, the drum is expediently driven at a speed of rotation which is around 70% of the spin speed. The hot air flowing through the drum drives the water out of the granular mixture and at the same time liquefies the binding agent, so that the granular mixture is coated and enveloped by the binding agent. The binding agent binds at the same time the fine material contained in the granular mixture and the dust from ₉ so that it cannot be carried out of the mixing chamber by the stream of hot air. Coarser lights, polygamy escaping from the drum, are collected in the expansion room. Until Erweicirang and Yerflüssigung of the binder is the dust or the leingut ¥ on the water content of the mix from escaping from the Miseteaum prevented "The drum may abruptly brought to a rotational speed are g containing about 70% of the spinning speed corresponds to" expediently is gedoch _s x-isnn the drum from standstill or long s ami is accelerated steadily ₉ if it reaches this rotational speed _o In addition, it is recommended to increase the amount of hot air steadily or in stages according to the measure · = the sit of the water is increasing © !! Chop © = raid Haft = the binder to rise @ m _o If the operator = determines ₉ that I'eiaststoff © aia © & em JLlbaiagsreto? 19 2 s © is this a itasaiekeii dafiisO that the barrel ¹ isge'ö ^ ielsQZii is used as © s in the Eialbli © Is bm £ di © simeli = mend © Haftt-jir-lssng of the binding agent © b3? Aoht is ο The Be =

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235 ^ 094

The exiling smarm can then be adjusted by adjusting the flap 119 and Throttling of the opening of the exhaust pipe 19 "by reducing it the fuel supply to the burner, x-ras to a decrease the amount of secondary air supplied, by reducing the speed of the burner the air feeding blower or a combination of some of these measures to premature drying out of the mix counteract. This setting can be achieved, for example, by using a burner with three settings allows, namely the setting of a pilot flame, a medium flame setting and a full I-flame setting. It goes without saying that other setting options can also be provided.

The above monitoring and adjustment can also be performed with With the help of an automatic monitoring system in dependence be effected by a signal which is supplied by a dust detector arranged in the exhaust pipe 19. Such a detector responds, for example, to radiation with a certain wavelength, which is obstructed by exhaust gas samples is sent.

It may be necessary to cool the material to be mixed in order to bring it to a Tewoe-ra'buT that corresponds to the usual mixing concept itself dadin? cli ₉ that cold air through dl © fEronnael hindnrchg © - s olii PJT ⁵ J becomes ο U'lnß- = Ibst-Jo Dürchlai ^ AÖl can x-jM.hr33id diessr-

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Stage are introduced into the drum. The Ealtluftstrom can be brought about by a fan which is provided with a throttled outlet which opens into the supply channel 13 in the direction of flow behind the throttle valve 115. The cooling can be effected by _s that the heater is placed on small! Flame "

In order to achieve the desired quality of the mix in certain cases To obtain this, another mixing stage may be required in which the burner works with a small flame and the throttle valve 113 is set so that it supplies the air to the exhaust duct 14- =

Each time the mixing process is completed, the mixer is tilted into position H2 and the motor 9 is driven at a lower speed in the opposite direction ₉ so that the screws or spirals located in the conical drum part 7 discharge the hot material to be mixed onto a carriage. The mixer is then tilted slightly and § thus brought into the position E1 to now be able to perform the next Mischsyklus "Bin cooling the (drum prior to loading with another batch of the granular batch is not required." it has rather shown ₉ that it is expedient c, the werderu drum gu isolate ₉ to Härme losses su possible ver-shun _o Accordingly, the isolation of the channel 13 provided

2 geigt a modified device aiar feeding the 4 09816/0933

Air to the burner and to the drum. According to FIG. 2, the burner is connected to the channel 13 via a double jacket, which consists of an inner tube 200 and a coaxial outer tube 201 ″ the reference numeral 202. The hanging channel 20; - is divided into two sections, a front and a rear channel section, by an annular guide wall 204. The two channel sections are each connected to the cylindrical inlet channel 202 Channel 206 an adjustable flap 205 is arranged in the ring catial, which can be adjusted so that in one setting position the air flowing through the channel 206 in egg chining on the drum and in the other setting position backwards as secondary air to the burner 12 This air flowing in the opposite direction cools the inner tube 200 ₉ which is made of a non-refractory and non-heat-storing material _ε such as stainless steel or another 'material is made. Depending on the setting of the flap 205, a flow of cold air or a flow of hot air from the drum can be supplied. will _o

shows one EinE-iolitnrigj at the Mischerleis' ^ raig

thereby to be increased kamir. that the iSr-oismel in liorisontsler-lags is loaded = With this facility is'ö a food

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a chain conveyor or the like. and the lengthways is so displaceable that it can be brought into a Besehickungsposition, in which the discharge end of the Conveyor is inside the drum. The sponsor is provided with a casing or cover 301 which has an opening for the discharge end of the conveyor. The arrangement can be such that the conveyor passes through the opening of a chimney or a suction shaft 303 or the like. o Since the drum with this arrangement only needs to be tilted for emptying, the inner drum wall can be completely smooth and even be. Discharge screws or the like. are not required. When emptying, the drum is rotated in the same direction as during the mixing process.

In the embodiment according to Fig. 4- the drum has only a single drum opening, which is also used for loading and emptying the drum when it is tilted into positions E1 and E2 the hot air with the drum in a horizontal position according to Ünie R3 »In IFigo 4- are the slill vessel for the granular mixture as well as the charging devices for the binding agent and the luller (not shown) Connected for the circulation system ± st _o In the channel 13 (not shown) inlet = and outlet lines can be placed

4 0 9 8 16/0938

rait adjustable throttle or the like. flow out. The drum can be mounted on one side on a shaft which is arranged on a drive and Eipp gear 9. These The facility is of compact design. It is therefore particularly demanding when using a binding agent in solid form IPorm is worked with little space, so with special Advantageously, it can be used as a small-sized transportable or mobile device. As mentioned, from the arrangement of jacks, drivers, screws and the like sn of the drum inner wall are disregarded. When emptying the drum rotates in the same direction of rotation as during the mixing process. As in the embodiment according to Fig. 3, the drum can rotate continuously, with it is only tilted to a certain extent for loading and emptying. In both cases, the binder be introduced into the drum in solid form rather than liquid form. It can therefore be added to the granular mixture before this is introduced into the drum '.

It can be seen that in all of the above Embodiments the complete method in one single mixer is performed. Instead of a continuous conveyance of the mix through a heater hindtax-eh, the mix is mixed and heated in the form of a closed batch, with the heat from one opposite dsm Mischsr removes aagsorfinetan Srliitzer gmgefüJart. Hi sr from sie, the possibility of monitoring the

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23 ^ 1G94

Temperature of the mix so that good results can be achieved. The method according to the invention is suitable especially for automatic control and monitoring based on temperature measurements «,

409816/093

Claims (1)

Expectations 1. A method for mixing a granular mixture, such as stone chippings and the like in particular, with a "bituminous binder, the mixture being produced with simultaneous hot air supply to liquefy the binder and to coat the granular mixture with the binder," characterized in that that with the initially cold granular mixture so much water is supplied to the Hischraujü that the dust material contained in the mixture is prevented from being entrained by the hot air stream before it is bound by the liquefying binder due to the water vapor formed during the hot air supply. 2 «Procedure nack claim 1 _? characterized in that the amount of hot air flowing through the ruffler is adjusted or regulated as a function of the amount of oil dust material entrained with the hot air stream. 3c. Method according to claim 1 or 2 _%, characterized in that the mixture is pre-separated by the hot air in a preliminary manner. Similiar sn ¥ sissei * fe! z? 3! 2— fsiiclrG'cng äes G-esienges ojLzroligefiihrt wi:? cu eiiissi the AnsiDrüci! ® i "to 3 ~ daGH2? Gii gs Mixer ton an approximately horizontal axis with a rotational speed is rotated between 50 to 90 ^ » preferably at about 70% of the spin speed lies. 5. Process according to Claims J and 4-, characterized in that that the mixer rotates during premixing at a speed of rotation that is 5 to JOyo the spin speed. 6. The method according to any one of claims 1 to 5 _9, characterized in that the water content of the granular mixture to a value of 0 ₉ 02 to 15 wt .-%, preferably J wt »~% or higher, based on the weight of the granular mixture , is set o 7 «Facility for carrying out the procedure after a or more of Claims 1 to 6, characterized by one between a horizontal mixing position and one inclined emptying position pivotable mixer (2) in connection with a loading device for loading of the mixer with the granular mixture and the bituminous Binder as well as with a hot air generator (12), which is used to supply the hot air to the one in the lüschposition befinö-union mixer with this via a feed channel (13) Terbunden and to the discharge of the hot air from the misery room to an outlet channel aneeselhlossen isto "O* ο Establishment according to iijiisprneii 7 ₃ by means of being denied ₉ that 4 09816/0938 An adjusting element (119) for adjusting the air throughput through the mixer is arranged in the exhaust air duct (19) is. 9. Device according to claim 7 or 8, characterized by a filling vessel (22) for charging the inclined in its Loading position located mixer (2) with the granular mixture. 10. Device according to claim 7 or 8, characterized by a feed conveyor (300) which feeds the mixer in its horizontal position with the granular mixture. 11. Device according to one of claims 7 to 10, characterized by a binder feed with which the Binder can be supplied to the mixer in the horizontal position. 12. Device according to one of claims 7 to 11, characterized in that the mixer (2) is free of inside Jacks or the like. is. 1Y. Device according to one of Claims 7 to 12, characterized characterized in that the mixer for the supply and discharge of the hot air has a single opening (1?). . Device according to one of Claims 7 to 13 »thereby characterized in that the hot air supply duct (13) is connected to one end of a double jacket duct 403816/0938 is composed of an outer tube (201) and one located therein Inner tube (200) "consists, both tubes of a non-refractory and non-heat-storing Material are made, and that the annular channel (20J) between the two tubes is the passage of the burner secondary air serves. 15. Device according to claim 14, characterized in that that in the annular space (203) between the two tubes (200, 201) in the direction of flow behind the supply air connection an adjustable shut-off element (205) is arranged. 16. Device according to one of claims 7 to 15, characterized characterized in that between the Hischer (2) and the exhaust line (19) an expansion chamber (18) is arranged. 403818/0338