DE9218953U1 - Solid fuel furnace, especially pellets - Google Patents

Description

Riener Karl Stefan Müllerviertel 20, A-4563 Micheldorf

Stove for solid fuels, especially pellets

The invention relates to an oven as described in the preamble of claim 1.

Known stoves for solid fuels with a burner bowl arranged in a combustion chamber and a conveyor device for the fuel, a fuel container in the combustion chamber and a convection chamber for recirculation operation

by means of a fan and a flue gas fan and which are designed to burn wood or wood-like fuels, i.e. fuels with a lower calorific value, have so far only been able to be used to a limited extent as permanent heaters to emit a uniform heating energy in the form of radiant and convective heat, in contrast to furnaces designed to burn coal or coke. The control processes required during the operation of these furnaces under changing operating conditions on the devices for the fuel and fresh air supply as well as the convective air flow are carried out by continuous monitoring of these furnaces and automatic control interventions. This often makes it possible to operate these furnaces unattended, but the energy utilization and operational safety are not satisfactory.

Furthermore, such stoves for solid fuels are often used as permanent heaters to emit radiant heat and also convection heat. Adjusting these stoves to changing requirements requires control processes and devices for the fuel supply of the primary and secondary air or the exhaust air, which means that continuous monitoring of the operating status, in particular the fuel supply, is necessary to avoid overheating of the combustion chamber or going out.

The invention is based on the object of creating a furnace with a high degree of efficiency for converting the energy contained in the fuel into space heating, as well as a combustion chamber with a fuel bowl and an exhaust air system for the flue gases with a sensitive central control system, which also has a high degree of operational reliability.

This object of the invention is achieved by the characterizing features of claim 1. The surprising advantage of this solution is that the specific design of such a furnace can be used to significantly increase the heat emission or heat transfer between the flue gases and the fresh air intended to heat the rooms to be heated, without having to provide complex additional technical equipment. At the same time, however, this design also advantageously increases the operational reliability of such a furnace, since the temperature of the flue gases flowing out of the furnace can be further reduced by this interposition of the heat exchanger, and an additional insulating effect is achieved between the combustion chamber and the chambers storing the fuel.

straight receiving container. At the same time, however, the solution also increases the efficiency of such a furnace without the need for additional fuel.

A further embodiment according to claim 2 is also advantageous, whereby the temperature of the supplied fresh air required for a pleasant living space atmosphere can be easily controlled.

A further development according to claim 3 is also advantageous, since this reliably prevents the risk of mixing of the heated fresh air to be supplied to the room and the flue gases.

In the embodiment according to claim 4, it is advantageous that, due to the cross-section becoming smaller in the direction of the outlet end, the passage speed of the fresh air to be heated is faster in those areas in which the flue gases have a higher temperature and a more intensive heat transfer takes place, whereby a uniform heat transfer between the flue gases and the fresh air is achieved.

It is advantageous for a favorable heat transfer between the flue gases and the fresh air if the tubes of the heat exchanger are designed according to claim 5.

However, an embodiment according to claim 6 is also advantageous, since it enables intensive heat transfer from heated flue gases to the surface of the parts of the heat exchanger through which the fresh air flows, so that the temperature changes resulting from different heat emissions during the combustion process can be compensated.

Furthermore, an embodiment according to claim 7 is also possible, whereby the cleaning devices necessary for keeping the surfaces of the heat exchanger clean in order to achieve a favorable heat transfer can simultaneously be used for an improved energy exchange between the flue gases and the heat exchanger.

In the embodiment according to claim 8, improved circulation and faster heating of the room air is achieved.

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The arrangement of a further air duct according to claim 9 enables a targeted reduction of the very hot temperatures on the combustion chamber track while simultaneously reducing radiation losses and making the best possible use of the energy for heating the fresh air supplied for room heating. In addition, it is possible to reduce the stress on temperature-sensitive machine components through this gradual temperature reduction and the arrangement of such an air duct for fresh air.

A design according to claim 10 is also advantageous, since it allows the already heated fresh air to be heated up again by passing over a wall of the overflow channel immediately before it exits into the room, which can prevent air build-up or turbulence in the convection shaft running almost horizontally beneath the cover plate.

The embodiment according to claim 11 is advantageous in that the overflow channel can, if necessary, also be subsequently installed in an already completed furnace.

A further advantageous embodiment is described in claim 12. This results in a forced guidance of the flue gas along the rear wall of the combustion chamber up to the area of the upper boundary of the combustion chamber, whereby additional heat is released to the rear wall and the heat exchanger adjoining the rear wall.

However, a design according to claim 13 is also advantageous because it shields the glass panes used in the doors and thus prevents contamination of the glass panes with soot particles from the flue gas.

A design according to claim 14 is also possible, whereby a rinsing process in the form of a fresh air curtain in front of the glass panes is achieved to cool them and keep them clean.

An advantageous further development is described in claim 15, whereby the mode of operation of the window flushing can be adjusted depending on the draft conditions in the combustion chamber.

A design according to claim 16 is also possible, whereby overheating of the contact surface of the furnace immediately in front of it is avoided.

The embodiment according to claim 17 is advantageous in that the air flow rate of the furnace is continuously monitored in order to carry out control interventions to maximize energy conversion.

A further embodiment according to claim 18 enables a simple and cost-saving control of the air quantity to be supplied via the cooling of a sensor element caused by the flow velocity of the air.

Furthermore, a further development according to claim 19 is also advantageous, since the fresh air supply to the combustion chamber can be easily changed by changing the delivery capacity of the flue gas blower.

A further advantage is a design according to claim 20, whereby the values determined by the sensors can be coordinated with target specifications for carrying out automatic control functions.

However, a design according to claim 21 is also advantageous, whereby a regulation adapted to the respective performance requirements is achieved.

A further advantageous embodiment is described in claim 22, whereby a uniform air and flue gas circulation in the combustion chamber and thus a compensation in the surface heating due to the different temperature load in the combustion chamber is achieved.

However, a design according to claim 23 is also possible because this achieves a higher efficiency of the heat exchanger.

A design according to claim 24 is also advantageous because the fresh air flowing into the combustion chamber is preheated while flowing through the air shaft arranged in the flue gas duct, which has a positive effect on combustion and thus on efficiency, particularly at very low temperatures of the fresh air.

A design according to claim 25 is also possible. As a result, a very high percentage of the surface of the combustion chamber is used to transfer heat energy from the flue gas to the convection air.

However, a design according to claim 26 is also advantageous because it achieves a very differentiated control, tailored to the respective operating conditions for the performance of the energy conversion in the fireplace and the heat transfer in convection operation.

Furthermore, an embodiment according to claim 27 is also advantageous because it achieves a uniform surface temperature of the casing surrounding the combustion chamber even with inherently unfavourable cross-sectional dimensions of the combustion chamber, e.g. with an aspect ratio of width to depth > 2.

The advantage of the design according to claim 28 is that a burner bowl inserted into a receiving chamber for the fresh air via sealing surfaces and openings in surface areas of the burner bowl for the primary air and a pressure control device between the combustion chamber and the flue gas blower ensure uniform and complete combustion of the fuel over the entire performance range of the furnace. The pressure control device also automatically regulates a difference in the negative pressure between the combustion chamber and the intake side of the fan depending on the set fan output of the exhaust air blower, at which constant operating conditions are achieved.

A further advantageous embodiment is described in claim 29. This achieves a differentiated supply of combustion air into the cone of the fuel, in particular the pellets.

A design according to claim 30 is also possible because the base area of the cone of material is thereby evenly supplied with primary air.

A design according to claim 31 is also possible, whereby a greater air supply is achieved on the bottom surface of the pouring cone than on the side surfaces.

A further advantageous embodiment is described in claim 32, because the conical design of the air duct in the flow direction of the primary air

- it.,

The flow velocity of the primary air is increased in the direction of the openings further away from the entry point of the primary air and therefore a higher flame image is achieved in this area facing the front doors.

However, a design according to claim 33 is also possible because the burner bowl is inclined in the direction of the ejection chute for the fuel, whereby a uniform fuel distribution in the burner bowl is achieved.

A further advantageous embodiment is described in claim 34, whereby a supply of primary air into the base of the fuel cone and thus a uniform combustion of the same is achieved.

An advantageous further development is described in claim 35, whereby overall a concentrated accumulation of the fuel in the burner bowl and thus a small surface area of the cone of material is achieved. This arrangement in particular achieves good continuous burning behavior of the furnace.

However, a design according to claim 36 is also advantageous because it enables the burner bowl to be fed with fuel without the fuel parts getting outside the burner bowl, which effectively prevents uncontrolled combustion of such parts.

A design according to claim 37 is also possible, whereby the burner bowl with its sealing surface as well as the sealing surface of the receiving chamber are achieved economically with a high level of precision, which is necessary to avoid false air flowing into the combustion chamber.

However, a design according to claim 38 is also advantageous, whereby overall a larger flame surface adapted to the cross-sectional shape of the combustion chamber and thus a better efficiency of the furnace is achieved.

According to an advantageous further development, as described in claim 39, the flue gases are collected in the flue gas chamber and fed to the flue gas blower and the exhaust air duct via the pressure control device which regulates the magnitude of the negative pressure.

Further training according to claim 40 is advantageous because it requires only a few and

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easy-to-manufacture components are required.

An advantageous further development is described in claim 41, whereby a flow-optimized deflection of the flue gases through the flue gas chamber and the pressure control device is achieved.

However, a design according to claim 42 is also advantageous because it enables the burner flap to respond automatically due to the effect of gravity.

According to an advantageous development according to the features of claim 43, a non-linear control curve is achieved for the pressure control device, which is adapted to the performance curve of the furnace.

A design according to claim 44 is also advantageous because it means that no additional components are required to achieve a non-linear control curve for the pressure control device.

Finally, a design according to claim 45 is also advantageous because the pressure control device simultaneously forms a shut-off element for the exhaust gas line.

For a better understanding of the invention, it is explained in more detail using the embodiments shown in the drawings.

Show it:

Fig. 1 shows a furnace according to the invention in front view; Fig. 2 shows the furnace according to Fig. 1 in side view;

Fig. 3 the furnace according to the invention, sectioned along the lines IH-III in

Fig. 4 shows the furnace according to the invention in plan view and partially in section; Fig. 5 shows the furnace according to the invention equipped with a heat exchanger.

Oven, sectioned along lines V-V in Fig.3;

Fig. 6 shows the heat exchanger arranged in the flue gas duct of the furnace according to the invention, sectioned along the lines VI-VI in Fig. 5;

Fig. 7 shows another embodiment of the oven according to the invention in side view, partially sectioned;

Fig. 8 shows a further embodiment of the oven according to the invention in plan view, partially sectioned;

Fig. 9 shows a further furnace according to the invention in front view; Fig. 10 shows the furnace according to Fig. 9 in side view;

Fig. 11 shows the further furnace according to the invention, sectioned along the lines XI-XI in Fig. 9;

Fig. 12 the further oven according to the invention in plan view and partially in section;

Fig. 13 a pressure control device of the furnace according to the invention, in section;

Fig. 14 a burner bowl of the furnace according to the invention in view, sectioned;

Fig. 15 the burner bowl according to Fig. 14, in plan view.

In Figs. 1 to 3, a furnace 1 is shown which has a combustion chamber 2 which is accessible via an operating and/or cleaning opening 3 which can be closed with combustion chamber doors 4, 5. The operating and/or cleaning opening 3 is arranged in a front wall 6 of a one-piece component 9 which preferably also forms side walls 7, 8. The one- or multi-piece component 9 has a trapezoidal or C-shaped cross-section and mounting strips 10, 11 running parallel to the front wall 6. The combustion chamber 2 is further closed off by a rear wall 12. At a distance in the opposite direction to the combustion chamber doors 4, 5 from the rear wall 12, a rear wall plate 13 of the convection casing is attached which, together with

the side walls 7,8 define a flue gas channel 14. In the area of the side walls 7,8, the convection jacket is formed by cladding elements 15,16, which are arranged between stop strips 17,18. Above the combustion chamber 2, a convection shaft 19 is arranged and below the combustion chamber 2, an inflow chamber 20 for convection air is arranged. In the flue gas channel 14, a convection shaft 19 formed from pipes 21 is arranged, which is connected to the inflow chamber 20 by a heat exchanger 22, in which ambient air flowing through arrow 23 - is heated by a flue gas flowing around the pipes 21 - arrow 24.

A base plate 25, a cover plate and a rear side 27 also form a boundary of the furnace 1. A loading flap 29 is arranged on the cover plate 26, which forms the vertical boundary of the furnace 1 and can be opened via a hinge arrangement 28, which covers a fuel container 30 when closed. The fuel container 30 is formed by a container wall 32 and container walls 33 that connect the side walls 7, 8 of the furnace 1 and are arranged in front of the rear wall plate 13 at a short distance 31. The flue gas channel 14 is thus located between the combustion chamber 2 and the fuel container 30.

A bottom area 34 of the fuel container 30 is V-shaped and tapered in the direction of the base plate 25, whereby a gravity chute is formed in the direction of an inlet opening 35 for a screw conveyor 36, which is arranged approximately at the lowest point of the bottom area 34. This conveys in particular a particulate fuel 37, e.g. pellets, with a screw 39 driven by a drive motor 38 in the direction of a tubular discharge chute 40. The discharge chute 40 is arranged inclined in the direction of the combustion chamber 2 and extends through the rear wall plate 13 and the rear wall 12, whereby the fuel 37, after reaching the highest point of the screw conveyor 36, slides down the discharge chute 40 by gravity and is fed to the combustion chamber 2 and is received by a burner bowl forming the firebox 41.

The burner bowl 42 is inserted in a receiving chamber 43 in a sealing arrangement 44. The receiving chamber 43 is connected to the ambient air - arrow 23 - via an air line 46 extending in the direction of the rear side 27 in order to supply combustion air - arrow 45. The combustion air - arrow 45 - flows to the firebox 41 and

flows around the particulate fuel 37. The flue gas is sucked out by a flue gas blower 49 and a negative pressure is generated in the combustion chamber 2, which inevitably increases the supply of combustion air - arrow 45. A change in the speed of the flue gas blower 49 allows the heat output of the furnace 1 to be adapted to the required amount of heat. The flue gas blower 49 supplies flue gas 50 to a flue gas outlet 51, which is connected, for example, to existing chimneys. As can also be seen from Fig. 3, a blower 52, in particular a radial blower, is arranged in the area between the fuel container 30 and the base plate 25, which supplies ambient air or fresh air - arrow 53 - to the convection shaft 19 through the pipes 21 of the heat exchanger 22. The fresh air - arrow 53 - is heated as it flows through the heat exchanger 22 through the hot pipes 21 around which flue gases 50 flow and is released as warm air into the environment of the furnace 1 through the convection shaft 19.

The flue gases 50 are guided through openings 55 arranged in the rear wall 12 in the area of a cover plate 54 delimiting the combustion chamber in the direction of the convection shaft 19 into the flue gas channel 14 and along the pipes 21 forming the heat exchanger 22 in the direction of an intake opening 56 for the flue gas blower 49. In the area of the flue gas channel 14 there is a cleaning device 58 which surrounds the pipes 21 at their periphery and is displaceably mounted in the direction of the longitudinal extension of the pipes 21 via a handle 57, in which scraper elements 59 formed from a flat profile form flue gas guide plates 60 of a flue gas guide device 61. This is achieved by arranging several scraper elements 59 in the longitudinal direction of the pipes, spaced apart from one another and offset relative to one another and relative to the rear wall 12 or rear wall plate 13. These narrow the flow cross-section or the opening width of the flue gas channel 14 alternately along the rear wall 12 or rear wall plate 13. As a result, the flue gas 50 is guided in a spiral shape around the pipes 21 of the heat exchanger 22, whereby a high level of efficiency of the heat exchanger 22 is achieved when heating the fresh air - arrow 53 - which is fed by the fan 52 through the pipes 21 to the convection shaft 19 and via this to the environment.

In the area of the convection shaft 19, an air guide device 62 formed by curved baffles is arranged to deflect the heated fresh air - arrow 53. This air guide device 62 causes a flow-optimized deflection of the preheated fresh air - arrow 53 -. In addition, if

this is considered advantageous, as a result of an injector effect in the area of the deflection, a portion of cooler fresh air can be sucked in via an opening 63 arranged in the rear wall plate 13 in the area of the cover plate 26 from an air duct 64 formed by the rear wall plate 13 and the container wall 32. This additional fresh air can serve as cooling for the screw conveyor 36.

In Fig. 4, the furnace 1 is shown in a top view and half cut in a horizontally arranged plane. The side walls 7, 8 are formed by the, in particular ceramic, cladding elements 15, 16, which are held in the stop strips 17, 18 arranged parallel to one another at a distance in the vertical direction. The combustion chamber 2 assigned to the front wall 6 is bordered by the combustion chamber doors 4 and 5 and the rear wall 12.

The loading flap 29 is arranged in the cover plate 26 and in an area between the side wall 7 and the container wall 32 there is a recess 66 covered by a flap 65 for a control and regulating device 69 supplied from an energy source 67 via lines 68 and mounted in the recess 66. Connecting lines 70 lead from the control and regulating device 69 to the blower 52, flue gas blower 49 and drive motor 38 of the screw conveyor 36. External data, such as the room temperature, is transmitted to the control and regulating device 69 via an external control device 71, e.g. a room thermostat, connected to the control and regulating device 69 via the connecting line 70 and is converted in the control and regulating device, in particular electronic, into commands, such as for changing the speeds of the blower and the drive motor 38 of the screw conveyor 36, whereby an automated and safe operation of the furnace 1 is achieved.

The combustion air - arrow 45 - is fed by the suction effect of the flue gas blower 49 via the air line 46 under the burner bowl 42 and through its openings 48 to the fireplace 41 with the fuel 37, e.g. parts pressed from plant materials, so-called pellets. The flue gas 50 produced during combustion in the fireplace 41 flows in the direction of the cover plate 54 that limits the combustion chamber 2 at the top and through the openings 55 and is drawn downwards against the thermosiphon effect, whereby it washes around and heats the flue gas channel 14 and the pipes 21. The flue gases are then diverted sideways and forcibly discharged by the flue gas blower to the outside via the flue gas outlet 51.

In Figs. 5 and 6, the flue gas channel 14 of the furnace 1 with the heat exchanger 22 is shown, whereby the same reference numerals are used for identical parts. The flue gas channel 14 is formed by the rear wall 12 and rear wall plate 13 connecting the side walls 7, 8, which are arranged parallel and at a distance 72 from one another. In the vertical direction, the flue gas channel 14 is limited in the direction of the cover plate 26 by a support plate 73 and in the direction of the base plate 25 by a hollow profile 74 of the heat exchanger 22.

The hollow profile 74 is formed, for example, by a tube 75 with a square cross-section, in which one side length corresponds approximately to the distance 72 and which is closed at the front and has a length 76 which corresponds approximately to an inner width 77 between the side walls 7, 8. The hollow profile 74 forms a distribution channel 78 of the heat exchanger 22, with the fan 52 for supplying the fresh air - arrow 53 - on a lower side 79 facing the base plate 25, which is fed to the fan 52 via openings 80 arranged in the front wall 6, which open into the inflow space 20. On an upper side 81 facing the support plate 73 or cover plate 26, the pipes 21 are arranged in a vertical direction to the cover plate 26, preferably welded, soldered, etc. to the distribution channel 78, with the pipes 21 being assigned openings 82 in the leg of the hollow profile 74.

At least several parallel pipes 21 are arranged over the length 76 of the distribution channel 78, which have an outlet opening 83 in the region of the convection shaft 19, which is formed by the side walls 7, 8 and the cover plate 26 and support plate 73. The pipes 21 extend through the support plate 73 in the direction of the convection shaft 19 and are connected to the support plate 73 in a movement-connected manner, e.g. welded, soldered, etc. The support plate 73, which spatially separates the flue gas channel 14 from the convection shaft 19 and forms the heat exchanger 22 with the pipes 21 and the distribution channel 78, is pulled forward in the direction of the front wall 6 and is fastened, preferably screwed, to the cover plate 54 which delimits the combustion chamber 2 in the direction of the cover plate 26, whereby the heat exchanger 22 forms a ready-to-assemble unit which can be dismantled from the area of the flue gas channel 14 for maintenance and/or repair work.

In the area between the distribution channel 78 and the support plate 73, the pipes 21 are connected by holes 84 enclosing the scraper elements 59 in the vertical direction.

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arranged longitudinally movable according to a double arrow 85, wherein these have an actuating rod 86 which is guided through the cover plate 26 and has a handle 57 for actuation. The scraping elements 59 preferably comprise several of the tubes 21, wherein preferably several scraping elements 59 are arranged parallel to one another and distributed in the longitudinal extension of the tubes 21, whereby even with a small movement in the direction of the double arrow 85, all surface areas of the tubes 21 can be reached by the front edges 87 formed by the bores 84 and cleaned of any soot particles, combustion residues, etc.

Furthermore, the scraper elements 59 are arranged offset from one another in tiers, whereby a gap 88 is alternately formed between the scraper element 59 and the rear wall 12 or the rear wall plate 13. The front edge 89 of the scraper element 59 opposite the gap 88 lies almost tightly against the rear wall 12 or the rear wall plate 13. Due to this offset arrangement of the scraper elements 59, the flue gases 50 flowing from the combustion chamber 2 into the flue gas channel 14 via the openings 55 are guided in a spiral around the pipes 21 of the heat exchanger 22 in the direction of the intake opening 56, through which the flue gases 50 flow to the flue gas blower 49.

In the embodiment shown, the tubes 21 of the heat exchanger 22 are grouped together in groups of three and arranged symmetrically to a central axis 90, with the tubes 21 closest to the central axis 90 being spaced further apart than the distances between the tubes 21 grouped together. This creates a free space along the central axis 90 for the discharge chute 40 that crosses the flue gas channel 14 in the direction of the combustion chamber 2. When forming the tubes 21 made of a good thermally conductive material, e.g. a copper alloy, care must be taken to ensure that they are designed to be flow-optimized, particularly in the area of the openings 82 of the distribution channel 78. It is advisable to expand the pipes 21 to a square cross-section, which results in a flow-optimized and large cross-section for the entry of fresh air - arrow 53 - into the pipes 21 from the distribution channel 78 and thus a low noise level. This also achieves a low output for the fan 52, which makes the furnace 1 particularly economical to operate.

Of course, it is also possible to provide the tubes 21 of the heat exchanger 22 with a square cross-section or rectangular cross-section over their entire length!

The cross-section should be designed with rounded corners or similar in order to achieve a large surface area for heat exchange on the one hand and a large flow cross-section on the other. This achieves a high air throughput at a reduced flow speed, thereby avoiding drafts and stress caused by flow and engine noise.

It has proven to be beneficial both for the efficiency of the heat exchanger 22 and for the service life of the tubes 21 to make them from copper alloys with a nickel-plated surface. Of course, other materials, such as stainless steel or rust-proof steels, can also be used for the tubes 21 of the heat exchanger 22.

Fig. 7 shows another variant of the furnace 1, whereby the same reference numerals are used for identical parts. In this variant, an overflow channel 92 is formed in the convection shaft 19 in the area between the air guiding device 62 and an outflow opening 91 by a housing 93 arranged on the cover plate of the combustion chamber 2. This housing spans openings 94 arranged in the cover plate 54 and connecting openings 95 arranged at a distance from these in the direction of the rear side 27 to the flue gas channel 14 provided with the heat exchanger 22.

A concavely curved design of the housing 93 results in a larger surface area and thus more effective heating of the circulating air flowing out of the convection shaft 19 by the flue gas 50. At the same time, a surface 96 of the housing 93 acts as an air guide device 62. The opening 94 in the cover plate 54 is covered in the direction of the combustion chamber 2 by an L-shaped profile 97, which is connected to the cover plate 54 by a leg 98, in particular welded, and whose other leg 99 extends approximately parallel to the cover plate 54 in the direction of the rear side 27. As also shown in dashed lines, the leg 99 can be unrolled or curved in order to deflect the flue gas 50 in the direction of the base plate 25 in a streamlined manner.

In the direction of the burner bowl 42, an approximately J-shaped profile 100 is attached to the leg 99, in particular screwed to it, which extends beyond the leg 98 in the direction of the firebox door 4.5, which is connected to one of the doors 4.5 or one of the firebox doors 4.5 or a glass plate inserted in the firebox doors 4.5.

pane 101 closest surface 102 forms a gap-shaped opening 103 for fresh air - arrow 105 - fed into the combustion chamber 2 through openings 104 in the cover plate 54. This fresh air - arrow 105 - fed into the combustion chamber 2 flows along the glass panes 101 in the direction of the base plate 25 and ensures that the glass panes 101 are kept free of combustion residues, soot, etc. In the area of the burner bowl 42, this fresh air is subsequently fed to the fireplace as secondary air for combustion.

An L-shaped profile 108 with a leg 109 is attached, in particular screwed, to the combustion chamber doors 4, 5 on a lower side 107 facing a support surface 106 of the furnace 1, the other leg 110 of which is arranged parallel to the glass pane 101 and projects in the direction of the cover plate 26. The leg 110 is arranged at a small distance 111 from the glass pane 101, whereby a channel 112 is formed for cooling air - arrow 114 - supplied through openings 113 in the leg 109 for cooling the glass pane 101. At the same time, the profile 108, which projects at a distance 111 from the glass pane 101 and in the direction of the cover plate 26, forms a heat shield 115, which shields a base area 116 of the support surface 106 from overheating due to heat radiation from the fireplace 41. In order to prevent overheating of the heat shield 115, it is particularly expedient to form an inner surface of the profile 108 facing the combustion chamber 2 with a radiation-reflecting surface 117.

Sensors 118 are arranged on the air line 46 for supplying the fireplace 41 with fresh air, which protrude into the clear pipe cross-section with sensor elements 119. The sensors 118 are connected via lines 120 to an electronic measuring device 121 of the control and regulating device 69. By means of the sensors 118 and the evaluation electronics of the measuring device 121, a regulation of the supplied fresh air adapted to the respective combustion performance of the furnace 1 is achieved by a target-actual comparison of the air flow. This target-actual comparison of the air flow is carried out in such a way that the sensor elements 119 are designed as thermal sensors. One of the two thermal sensors is heated and the determination of the amount of air supplied to the combustion chamber is now carried out by determining the cooling of this thermal sensor by the amount of air moving past. If the flow speed at the predefined constant cross-section corresponds to the target value, a precisely predefined amount of air is supplied to the furnace. This amount of air is completely independent of the external air pressure and therefore also of the altitude of the installation location.

This also makes it possible to determine, based on the heated resistance, whether the amount of air supplied is above or below the desired target value. If the resistance is warmer than would be the case with the target air flow, the air flow speed must be increased; if the resistance is cooler than the specified target temperature, the air flow speed must be reduced in order to supply the combustion chamber with the desired amount of air.

In order to precisely match this air flow control, which enables precise combustion air supply and thus precise control of the combustion process, to the respective operating state or installation location, the temperature of the fresh air drawn in must also be taken into account. This is done using a further sensor 118 or a further sensor element 119, which is formed by a thermal sensor, i.e. a resistor. If the air temperature is cooler, the heated resistor or sensor element 119 cools down more quickly, whereby the target temperature of the heated resistor must be predefined depending on the air temperature determined in order to ensure that the air flow supplied to the combustion chamber corresponds to the respective set power level. In order to enable control of the combustion process over a large control range, these sensors can be designed for flow speeds of 0.5 m/sec to 5 m/sec, for example. Preferably, the speed of the air flow is 0.8 to 3.2 m/sec. The respective flow speed monitored by the heated resistor or sensor element 119 depends on the set power level of the oven, since the amount of air required for a higher heating output is greater than, for example, for a low heating level.

Depending on the flow speeds determined by the sensors 118 or sensor elements 119 and taking into account the set heating power, this is then continuously changed.

The advantage of this solution is also that minor leaks in the combustion chamber are compensated for by this air flow control. This is such that the incorrect air flow in the event of leaks leads to a lower combustion output, which means that the desired combustion temperature for the set output level is not reached and the next higher output level is automatically switched on via the control and regulating device 69.

A further advantage of this air quantity control based on the flow rate is that in order to change the air quantity to be supplied, it is only necessary to change the speed of the flue gas blower 49, for example, so that the negative pressure formed in the combustion chamber 2 is increased, so that the flow rate of the fresh air drawn in - arrow 53 - is increased. If the flow rate is too high, the speed of the flue gas blower 49 is reduced accordingly. This closed control loop between the sensors 118 and the flue gas blower 49 is created via the control and regulating device 69. For example, in this context it is also possible to provide a sensor or a sensor element 119, for example a thermal sensor, in the convection shaft 19, with which the air temperature of the heated fresh air is determined in order to increase the combustion process accordingly if the furnace's output is insufficient.

If deviations are detected by the measuring devices 121, the control and regulating device 69 activates a control circuit for the corresponding speed change of the variable-speed drive of the flue gas blower 49.

Through the target-actual comparison, which is achieved through the measurement results of the sensors 118, the supply of fresh air into the combustion chamber 2 can be monitored according to the respective operating state and adjusted via the speed control even if, for example, there is an increased flow resistance when supplying fresh air in the air line 46. This results in an automatic adjustment of the speed level of the flue gas blower 49, which takes into account different connection conditions, especially when the furnace 1 is first put into operation. Furthermore, the drives of the blower 52 for the convection air and the screw conveyor 36 are designed to be speed-adjustable in order to regulate the air and fuel quantity according to a desired operating state of the furnace 1.

In Fig.8, a further variant of the furnace 1 is shown, whereby the same reference numerals are used for the same parts. The combustion chamber 2 is surrounded by the C-shaped flue gas channel 14 on its rear wall 12 and the side walls 7, 8. This is limited in the direction of the rear side 27 by the rear wall plate 13 and in the direction of the side surfaces 122 by the cladding elements 15, 16. In the area of an axis of symmetry 123, a

A U-shaped profile 124 protruding in the direction of the flue gas channel 14 is arranged for an air shaft 126 extending approximately from the area of the cover plate 54 into the area of a burner plate 125, in particular welded to it in a gas-tight manner. The fresh air arrow 53 is fed to the air shaft 126 via the air line 46 and is heated by the flue gases flowing through the flue gas channel 14 as it flows in the direction of the burner bowl 42 arranged in the burner plate. The heat exchangers 22 formed by the pipes 21 are arranged in the flue gas channel 14 and, due to the formation of the flue gas channel, enclose the combustion chamber 2 on the rear wall 12 and on the side walls 7, 8. As shown in dashed lines, for example, it is possible to divide the flue gas duct 14 into several independent shafts 128 using separating plates 127 and to assign a heat exchanger 22 to each shaft. It is also possible to assign the flue gas blower 49 for the flue gas 50 to the flue gas duct 14 as a whole or to each shaft 128 of the flue gas duct 14. It is also possible to assign the blower 52 as a whole to the heat exchangers 22 or to each heat exchanger 22. This design makes it possible to achieve sensitive power control even with combustion chambers 2 that have a large volume or unfavorable side ratios of width 77 to depth 129 of the combustion chamber 2.

The ambient air indicated by an arrow 23 or the fresh air indicated by an arrow 53 can be taken from the heated room, i.e. for example the ambient air, but can also be supplied via a separate pipe from outside the building or from a room other than the heated room. If necessary, it can also prove useful to change the air extraction point or to change the proportion of the air that is taken from the room to be heated to that part that is supplied from another room or from outside a building in general.

In Figs. 9, 10 and 11, a furnace 201 is shown which has a combustion chamber 202, which is accessible via an operating and/or cleaning opening 203, which can be closed with combustion chamber doors 204, 205. The operating and/or cleaning opening 203 is arranged in a front wall 206 of a one-piece component 209 which also forms side walls 207, 208. The component 209 has a trapezoidal or C-shaped cross-section and mounting strips 210, 211 running parallel to the front wall 206. The combustion chamber 202 is also closed off by a rear wall 212. A rear wall plate 213 of the convection jacket is attached at a short distance from the rear wall 212. In the area of the side walls 207, 208

* · · » ·■■·■» ^&tgr;&bgr; -;

the convection casing is formed by cladding elements 214, 215 and 216, which are arranged between stop strips 217 to 220. Above the combustion chamber 202 there is a warming or baking compartment 221 and below it there is a circulation chamber 222 for convection air, which continues vertically into a convection chamber 223 between the rear wall 212 and rear wall plate 213, which is connected to the ambient air by pipes 224 crossing the combustion chamber 202 in the direction of the front wall 206.

A base plate 225, a cover plate 226 and a rear side 227 also form a boundary of the furnace 201. A loading flap 229 is arranged on the cover plate 226, which forms the vertical boundary of the furnace 201 and can be opened on the cover plate 226 via a hinge arrangement 228, which covers a fuel container 230 when closed. The fuel container 230 is formed by a container wall 232 and a container wall 233, which connects the side walls 207, 208 of the furnace 201 and is assigned to the rear wall plate 213 of the combustion chamber 202 at a short distance 231. A bottom area 234 of the fuel container 230 is V-shaped and tapered in the direction of the base plate 225, which results in an inclined plane in the direction of an inlet opening 235 of a screw conveyor 236 arranged approximately at the lowest point of the bottom area 234. A particulate fuel 237 is grasped in this area by a screw 239 driven by a drive motor 238 and conveyed upwards in the direction of a tubular discharge chute 240. The discharge chute 240 is arranged inclined in the direction of the combustion chamber 202 and extends through the rear wall plate 213 and the rear wall 212, whereby the fuel 237, after reaching the highest point of the screw conveyor 236, is fed to the combustion chamber 202 by gravity and is received by a burner bowl 242 forming the firebox 241. The burner bowl 242 is inserted into a box-shaped receiving chamber 243 via a sealing arrangement 244 formed on the burner bowl 242 and the receiving chamber 243. The receiving chamber 243 is connected to the ambient air in the direction of the rear side 227 for supplying combustion air - arrow 245 - via a pipe 246. The combustion air - arrow 245 - flows to the firebox 241 and thus into the particulate fuel 237 via openings 248 arranged on the surface areas 247 of the burner bowl 242 facing the receiving chamber 243, whereby a flue gas blower 249 generates a negative pressure in the combustion chamber 202 by sucking out the flue gases - arrow 250 -, whereby the supply of combustion air - arrow 245 - is necessarily increased and this effect is increased by changing the speed

the flue gas blower 249 can be adapted to the requirements of the heat output of the furnace 201. The flue gas blower 249 feeds the flue gas - arrow 250 to a flue gas outlet 251, which is connected, for example, to existing chimneys. As can also be seen from Fig. 11, a blower 252, in particular a radial blower, is arranged in the area between the fuel tank 230 and the base plate 225, which supplies fresh air - arrow 253 - to the convection chamber 223. The fresh air - arrow 253 - is heated as it passes along the rear wall 212 of the combustion chamber 202 and is released as warm air to the surroundings of the furnace 201 through convection pipes 254.

In Fig. 12, the furnace 201 is shown in a top view and half cut in a horizontally arranged plane. The side walls 207, 208 are formed by the, in particular ceramic, cladding elements 214, 215, 216, which are held in the stop strips 217, 218, 219, 220 arranged parallel to one another at a distance in the vertical direction. The combustion chamber 202 assigned to the front wall 206 is bordered by the combustion chamber doors 204 and 205 and the rear wall 212, with channels 256 for supplying the flue gases - arrow 250 - to the flue gas blower 249 arranged near the base plate 225, which are delimited from the combustion chamber 202 in a mirror image to a plane of symmetry 255 and cross it in the vertical direction. The combustion chamber 202 is surrounded in a U-shape in the direction of the rear side 227 of the furnace 201 by the shaft-shaped convection chamber 223, whereby a large radiation surface for heat transfer to the convection air is achieved. In the area between the convection chamber 223 or a sheet metal profile delimiting the convection chamber 223 and the rear side 227 of the furnace 1, the fuel container 230 is arranged and between this and the base plate 225 the flue gas blower 249 and the blower 252 for the convection air are arranged. The loading flap 229 is arranged in the cover plate 226 and in an area between the side wall 207 and the container wall 232 there is a built-in trough 258 covered by a flap 257 for a control and regulating device 261, which is fed from an energy source 259 via lines 260 and mounted in the built-in trough 258. Connecting lines 262 lead from the control and regulating device 261 to the blower 252, flue gas blower 249 and drive motor 238 of the screw conveyor 236. External data, such as the room temperature, are transmitted to the control and regulating device 261 via an external control device 263, e.g. a room thermostat, which is connected to the control and regulating device 261 via the connecting line 262 and is converted into commands in the control and regulating device, in particular electronic ones, such as for

the change in the speeds of the blower and the drive motor 238 of the screw conveyor 236 is implemented, whereby an automated and safe operation of the furnace 201 is achieved.

The combustion air - arrow 245 - is fed by the suction effect of the flue gas blower 249 via the pipe 246 under the burner bowl 242 and through its openings 248 to the fireplace 241 with the fuel 237, e.g. parts pressed from plant materials, so-called pellets. The flue gas escaping from the fireplace 241 flows in the direction of the cover plate 264 that limits the combustion chamber 202 at the top, whereby the convection pipes 254 are washed around and heated. This is followed by the lateral deflection of the flue gases - arrow 250 - and their discharge in the channel 256 and discharge through an automatic pressure control device 265 upstream of the flue gas blower 249 into the flue gas outlet 251.

In Fig. 13, the pressure control device 265 is shown, which is arranged upstream of the flue gas blower 249 in the direction of the combustion chamber 202 and the channel 256 for the flue gas - arrow 250. A pivotable flap 269 is assigned to an opening 266 in an inclined surface area of a collecting channel 267 in the direction of the flue gas blower 249 around an axis 268 arranged parallel to the base plate 225, the overall center of gravity of which has a greater distance 270 from the base plate 225 than a distance 271 of the axis 268 from it. In the inoperative state, the flap 269 closes the opening 266, whereby the air circulation from the channel 256 and thus from the combustion chamber 202 to the flue gas outlet 251 is interrupted. If a suction effect is exerted by the flue gas blower 249 in the operating state, the flap 269 pivots in the direction of an arrow 272, whereby the opening 266 is released depending on the magnitude of the suction effect up to a maximum value with the flap 269 in an almost vertical position, which results in different pressure conditions in the flow direction upstream and downstream of the flap 269 depending on the position of the flap. The restoring moment of the flap 269 is further reduced by the arrangement of the center of gravity of the flap 269 in relation to its axis 268 with increasing opening position in the direction of the position of the flap 269 shown in dashed lines, which achieves the desirable effect that the pressure difference at high suction power of the flue gas blower 249 and thus at a high power requirement of the furnace 201 is smaller than at a preselected low power requirement of the furnace 201. The pressure difference is at least approximately 0.5 mb and

Maximum 1.2 mb.

In Figs. 14 and 15, the receiving chamber 243 is shown with the burner shell 242 held in it. The burner shell 242 preferably has a circular cross-section associated with the sealing arrangement 244, with which the burner shell 242 rests sealingly on the receiving chamber 243. In the surface areas 247 facing the receiving chamber 243, the burner shell has the openings 248 for the combustion air supplied via the pipe 246 - arrow 245. From the sealing arrangement 244 in the direction of the combustion chamber 202, the burner shell 242 is formed by a baffle wall 273, a rear wall 274 and transverse walls 275, 276 connecting these. Preferably, a height 277 of the baffle wall 273 projecting beyond the sealing arrangement 244 is greater than a height 278 of the rear wall 274. Accordingly, the transverse walls 275, 276 also have a height gradation in their course connecting the baffle wall 273 and the rear wall 274. The cross section of the area of the burner bowl 242 projecting beyond the sealing arrangement 244, formed by the baffle wall 273, the rear wall 274 and the transverse walls 275, 276, preferably has an oval or elliptical cross section. However, a circular cross section that widens conically from the sealing arrangement 244 in the direction of the combustion chamber 202 is just as possible, as is a square or rectangular cross section with rounded corners. A design as a cast body is also advantageous. The openings 248 can be arranged evenly or unevenly in a base plate 279 and/or in the inclined surface areas 247 of the burner bowl 242 and can be of equal or unequal size.

Of course, it is also possible to construct the burner bowl 242 in a welded construction made of heat-resistant sheet metal.

For better understanding, a disproportionate representation was chosen for the embodiments in the figures. Furthermore, the invention is not limited to the embodiments shown, as other combinations and individual features can also form independent, inventive solutions.

Claims (44)

Protection claims 1. Stove for solid fuels, in particular pellets with a combustion chamber, a receiving tray for the fuel arranged in the combustion chamber, a fuel conveying device between the receiving tray and a fuel container for fuel, a convection chamber surrounding the combustion chamber, which is closed off from the outside by a convection jacket, and optionally a fan arranged between the ambient air and the convection chamber and with a smoke blower arranged between the combustion chamber and a smoke line, characterized in that at least one rear wall (12) of the combustion chamber (2) is preceded by a smoke duct (14) on the side facing away from the combustion chamber (2), which extends at least over part of a width (77) and a height of the combustion chamber (2) and in the upper end region of the smoke duct (14) facing a cover plate (26) with at least one opening (55) connecting this to the combustion chamber and in the opposite end region facing a base plate (25) with at least an intake opening (56) is connected to a flue gas outlet, preferably with the interposition of a flue gas blower (49), and that a heat exchanger (22) is arranged in the flue gas duct (14), through which fresh air - arrow (53) - flows against the flow direction of a flue gas (50). 2. Oven according to claim 1, characterized in that the heat exchanger (22) is assigned a blower (52) for the fresh air - arrow (53) -, in particular arranged upstream. 3. Oven according to claim 1 or 2, characterized in that the heat exchanger (22) is formed by hollow profiles arranged parallel to one another and through which fresh air flows, e.g. tubes (21), oval tubes, square tubes, rectangular tubes with rounded corners or the like. 4. Oven according to one or more of claims 1 to 3, characterized in that the tubes (21) of the heat exchanger (22) have an approximately square expanded cross-section at least in the region of an inflow opening for the fresh air - arrow (53). 5. Furnace according to one or more of claims 1 to 4, characterized in that the tubes (21) of the heat exchanger (22) are made of a copper alloy, Stainless steel, steel, etc., and a surface is preferably nickel-plated. 6. Furnace according to one or more of claims 1 to 5, characterized in that the heat exchanger (22) is provided with a flue gas guide device (61) which is formed from the flue gas guide plates (60) which delimit the flue gas channel (14) from opposite sides in the opening width and are spaced apart from one another in the direction of flow. 7. Oven according to one or more of claims 1 to 6, characterized in that the flue gas guide plates (60) are formed by scraper elements (59) of a cleaning device (58) guided along tubes (21) of the heat exchanger (22). 8. Oven according to one or more of claims 1 to 7, characterized in that an air guiding device (62) is arranged between the outlet of the fresh air from the heat exchanger (22) and an outflow opening (91) from a convection shaft (19), in the area of which at least one opening (63) for fresh air - arrow (53) - supplied from the ambient air is arranged. 9. Oven according to one or more of claims 1 to 8, characterized in that the opening (63) for the fresh air supply is connected to an air duct (64) running parallel to the heat exchanger (22), and preferably a bearing device of a screw conveyor (36) is arranged in this. 10. Oven according to one or more of claims 1 to 9, characterized in that an overflow channel (92) for the flue gas (50) formed by a housing (93) is arranged in the region of the convection shaft (19). 11. Oven according to one or more of claims 1 to 10, characterized in that the overflow channel (92) is in flow connection with the combustion chamber (2) via openings (94) arranged in a cover plate (54) of the combustion chamber (2) and connecting openings (95) with the flue gas channel (14). 12. Furnace according to one or more of claims 1 to 11, characterized in that the opening (94) in the direction of the combustion chamber (2) is provided with an L-shaped profile (97) connected to the cover plate (54) as a guide device for the Flue gas (50) is arranged upstream. 13. Oven according to one or more of claims 1 to 12, characterized in that a J-shaped profile (100) projecting in the direction of the firebox doors (4, 5) is arranged on the profile (97), which forms a gap-shaped opening (103) with a surface (102) of the profile (100) and a glass pane (101) of the firebox doors (4, 5). 14. Oven according to one or more of claims 1 to 13, characterized in that openings (104) are arranged in the cover plate (54) in the region of the combustion chamber doors (4, 5), which form a flow connection between the ambient air and the combustion chamber (2) for secondary air - arrow (105). 15. Oven according to one or more of claims 1 to 14, characterized in that an opening width of the gap-shaped opening (103) is adjustable via an adjusting device of the J-shaped profile (100). 16. Oven according to one or more of claims 1 to 15, characterized in that a heat shield (115) is arranged in front of the glass pane (101) in the region of an underside (107) of the combustion chamber doors (4, 5). 17. Oven according to one or more of claims 1 to 16, characterized in that sensors (118) with sensor elements (119) protruding into the clear cross-section of the air line (46), e.g. a thermal sensor formed by a heated resistor and a thermal sensor formed by an unheated resistor, are arranged in an air line (46) for supplying fresh air to a fireplace (41). 18. Oven according to one or more of claims 1 to 17, characterized in that in an air line (46) for supplying fresh air to a fireplace (41), arranged upstream of a smoke gas blower (49), a sensor element (119) formed by a heated resistor is arranged, the output signals of which are passed on to a control and regulating device (69) to which a motor of the smoke gas blower (49) is connected via a control circuit and a target temperature for the sensor element (119) is determined depending on the set heating output, and this target temperature is changed depending on the air temperature of the fresh air supplied - arrow (53). 19. Oven according to claim 18, characterized in that the conveyed air quantity, in particular the speed of the flue gas blower (49) is increased by the control and regulating device (69) when an actual temperature of the heated resistor of the sensor element (119) is below a target temperature, and when the temperature is above the target temperature, the speed is reduced. 20. Oven according to one or more of claims 1 to 19, characterized in that the sensors (118) are assigned a measuring device (121) in a control and regulating device (69). 21. Oven according to one or more of claims 1 to 20, characterized in that drives of the flue gas blower (49) and the screw conveyor (36) are designed to be infinitely variable in speed. 22. Furnace according to one or more of claims 1 to 21, characterized in that the openings (55, 94), connecting openings (95) and intake openings (56) that flow-connect the combustion chamber (2) to the flue gas duct (14) and the flue gas blower (49) are formed by a plurality of connecting openings (95) arranged at a distance from one another in the direction of a width of the furnace (1). 23. Oven according to one or more of claims 1 to 22, characterized in that the connecting openings (95) are arranged approximately in the region of the tubes (21) of the heat exchanger (22). 24. Oven according to one or more of claims 1 to 23, characterized in that an air shaft (126) is arranged in the flue gas duct (14) in the region between at least two heat exchangers (22) formed by the pipes (21) for supplying fresh air to the fireplace (41). 25. Oven according to one or more of claims 1 to 24, characterized in that the flue gas channel (14) is arranged in a U-shape surrounding the combustion chamber (2) at its rear wall (12) and side walls (7,8). 26. Furnace according to one or more of claims 1 to 25, characterized in that in the region of the C-shaped flue gas channel (14) several heat exchangers (22) formed by the tubes (21) are arranged and the heat exchangers i I. (22) a common or each heat exchanger (22) has an independently controllable fan (52) for the fresh air - arrow (53) - assigned to it. 27. Oven according to one or more of claims 1 to 26, characterized in that the U-shaped flue gas channel (14) is formed by several separate shafts (128) and each channel is assigned a flue gas blower (49). 28. Furnace according to one or more of claims 1 to 27, characterized in that a primary air line in the combustion chamber (202) opens into a receiving chamber (243) which is provided with an end face designed as a sealing surface facing a burner bowl (242) for burning the fuel (237), on which the burner bowl (242) rests in a sealing manner with a circumferential sealing surface, and in that the burner bowl (242) has openings (248) for the primary air in the surface area (247) facing the receiving chamber (243), and an automatic pressure control device (265) is arranged between the combustion chamber (202) and the flue gas blower (249). 29. Oven according to one or more of claims 1 to 28, characterized in that a cross-sectional area of the openings (248) becomes smaller as the distance to the sealing surface decreases. 30. Oven according to one or more of claims 1 to 29, characterized in that the openings (248) are evenly distributed over the surface area (247) facing the receiving chamber (243). 31. Furnace according to one or more of claims 1 to 30, characterized in that a size of the openings (248) in a base plate of the burner bowl (242) arranged in the receiving chamber (243) is larger than the openings (248) in side walls running at an angle to the base plate. 32. Oven according to one or more of claims 1 to 31, characterized in that the base plate runs inclined to a support surface of the oven (201) or to a plane receiving a supply line for the primary air or an end plate of the receiving chamber (243). 33. Oven according to one or more of claims 1 to 32, characterized in characterized in that the end plate of the receiving chamber (243) and the base plate of the burner bowl (242) are aligned parallel to each other and run at an incline to a supporting surface of the furnace. 34. Furnace according to one or more of claims 1 to 33, characterized in that the burner bowl (242) has a baffle wall (273) which projects beyond the sealing surface of the same in the direction of the combustion chamber (202) and is located opposite an inlet opening (235) of an ejection chute (240) of the conveying channel for the fuel (237), transverse walls (276) which delimit the latter and a rear wall (274) facing the inlet opening (235). 35. Furnace according to one or more of claims 1 to 34, characterized in that the baffle wall (273) projects beyond the rear wall (274) and optionally at least parts of the transverse wall (276) in the direction of the combustion chamber (202) and approximately parallel to a vertically extending axis of symmetry of the burner bowl (242) beyond the sealing surface of the receiving chamber (243). 36. Oven according to one or more of claims 1 to 35, characterized in that a height (277, 278) of the baffle wall (273), rear wall (274) and transverse wall (276) projecting beyond the sealing surface of the receiving chamber (243) has a different size. 37. Furnace according to one or more of claims 1 to 36, characterized in that the burner bowl (242) has a circular cross-section in the region of the sealing surface in a plane running parallel to the base plate. 38· Oven according to one or more of claims 1 to 37, characterized in that the baffle wall (273), rear wall (274) and transverse walls (276) of the burner bowl (242) delimit an oval or elliptical cross-sectional area in the direction of the combustion chamber (202). 39. Furnace according to one or more of claims 1 to 38, characterized in that channels (256) for the flue gas are arranged between the combustion chamber (202) and a collecting channel (267) of the pressure control device (265) connected to the flue gas blower (249). 40. Oven according to one or more of claims 1 to 39, characterized in characterized in that the pressure control device (265) is formed by a flap (269) which tightly covers an opening (266) of an intermediate wall of the collecting channel (267) and can be pivoted about an axis (268). 41. Oven according to one or more of claims 1 to 40, characterized in that the flap (269) in its position closing the opening has an inclination of approximately 45° to 70°, preferably 60°, relative to the base plate (279). 42. Oven according to one or more of claims 1 to 41, characterized in that the flap (269) in its open position forms an angle of less than or equal to 90° with respect to the base plate (279). 43. Oven according to one or more of claims 1 to 42, characterized in that a distance of the overall center of gravity of the flap (269) pivotable about the axis (268) from the base plate (279) is greater in the open position than in the closed position. 44. Oven according to one or more of claims 1 to 43, characterized in that the flap (269) and/or intermediate wall has a sealing arrangement for the intermediate wall and/or flap (269).