BIOMASS BOILER AND METHOD FOR OPERATING A BIOMASS BOILER

Description

[0001] The invention relates to a biomass boiler for a solid biomass fuel, in particular pellets and / or wood chips, comprising: a boiler casing; a combustion chamber; a solid fuel conveying device for feeding the combustion chamber with the biomass solid fuel, wherein the solid fuel conveying device has a conveying channel and a conveying unit for conveying the biomass solid fuel within the conveying channel; a combustion air supply device within the boiler casing for distributing and supplying combustion air, in particular primary and / or secondary and / or tertiary air, into the combustion chamber, wherein the combustion air supply device within the boiler casing is arranged at least partially around the combustion chamber and the combustion air supply device is configured to distribute the combustion air to several inlet openings into the combustion chamber; and an intake opening for combustion air.

[0002] Furthermore, the invention relates to a method for operating a biomass boiler.

[0003] Biomass boilers are used for heat generation. An example of such a biomass boiler is shown in EP 3 495 045 A1. The combustion air required for combustion is drawn in through the intake opening and introduced into the combustion chamber via the combustion air supply device, where multi-stage combustion of the solid biomass fuel takes place. Many biomass boilers have several inlet openings in the combustion chamber for efficient and complete combustion, in particular to introduce primary and / or secondary and / or tertiary air into the combustion chamber.

[0004] A disadvantage of known biomass boilers is that the high temperatures in the combustion chamber can damage the solid fuel feeding system. This is particularly true during periods when no new, lower-temperature solid biomass fuel is being fed in.

[0005] To prevent damage from high temperatures, it is known in the art to cool those parts of the solid fuel conveying system of biomass boilers that are exposed to high temperatures using water. However, this technique has the disadvantage of being very complex.

[0006] Even though modern biomass boilers already achieve high efficiencies, it is always a concern of development engineers to further improve the efficiency of biomass boilers.

[0007] From PL 222 523 B1, a different type of burner for central heating boilers for the combustion of fine coal is known, in which the combustion air is directed outside the burner housing across the feed channel of a feed screw and then directly into the combustion chamber through an opening. Due to the brief heating via the feed channel and the subsequent direct introduction of the combustion air through the opening, the efficiency of the burner is only slightly increased.

[0008] Solid fuel boilers are also known from DE 43 44 760 A1 and KR 101 323 388 B1.

[0009] DE 43 44 760 A1 discloses a furnace for crushed, solid fuel material. The fuel material is conveyed from a storage chamber into a combustion chamber by means of a screw conveyor. An air supply duct is also provided.

[0010] KR 101 323 388 B1 discloses a pellet boiler. The pellets are fed into a combustion chamber together with combustion air, which is guided around a conveying device via a funnel-shaped nozzle. The combustion air is drawn in from outside by a blower and distributed to various channels. The air distribution is carried out by a distribution unit located outside the boiler housing.

[0011] In light of these considerations, the object of the present invention is to at least partially alleviate or even completely eliminate the disadvantages of the prior art. Preferably, the object of the invention is to increase the service life of the components, in particular the solid fuel conveying device, of a biomass boiler of the type mentioned above, while simultaneously improving its efficiency.

[0012] This problem is solved by a biomass boiler according to claim 1 and a method for operating a biomass boiler according to claim 12.

[0013] According to the invention, in a biomass boiler of the type mentioned above, the intake opening is provided on the solid fuel conveying device, and a combustion air flow path leads from the intake opening to the conveying channel and further into the combustion air supply device, wherein the combustion air flow path is guided at least partially along the conveying channel. Advantageously, the combustion air flow path according to the invention heats the combustion air over a longer period of time at the hot parts of the biomass boiler before it enters the combustion chamber, thereby increasing the efficiency of the biomass boiler compared to the prior art. The fact that the combustion air flow path is guided at least partially along the conveying channel also advantageously cools the solid fuel conveying device, in particular the conveying channel.Furthermore, the combustion air flow path according to the invention allows the conveying channel to be better protected from the heat of the combustion chamber, since the combustion air is not fed directly into the combustion chamber, but rather via the combustion air supply device. The combustion air supply device is arranged at least partially, preferably completely, within the boiler housing and is configured to direct the combustion air to at least one, preferably several, inlet opening(s) through which the combustion air is introduced into the combustion chamber. The combustion air supply device can have a cavity between two walls of the boiler housing. This cavity can also be referred to as the boiler air jacket. The cavity can be formed or delimited, for example, by pipes and / or baffles. The combustion air supply device extends at least partially around the combustion chamber.In one embodiment of the invention, the combustion air supply device is configured to introduce primary and / or secondary and / or tertiary air into the combustion chamber. For this purpose, primary, secondary, and / or tertiary inlet openings, which will be described in more detail below, can be provided, in particular on a wall of the boiler housing facing the combustion chamber. The intake opening can be covered by a grille. When primary and / or secondary and / or tertiary air is introduced into the combustion chamber by means of the combustion air supply device, the intake opening can preferably be a common intake opening for primary and / or secondary and / or tertiary air. Multiple intake openings or common intake openings can also be provided.During operation of the biomass boiler, ambient air is drawn in through the intake opening(s) and then guided as combustion air along the combustion air flow path to the combustion chamber. The combustion air initially flows along the combustion air flow path from the intake opening to the feed channel of the solid fuel conveying system, thus cooling it and reducing the risk of damage. Advantageously, the combustion air is heated in the process, which increases the efficiency of the biomass boiler. The combustion air flow path preferably runs along an outer wall of the feed channel, preferably made of metal, on the inside of which the conveying unit is located. The combustion air flowing along the combustion air flow path is therefore in contact with the outer wall of the feed channel.The combustion air flow path is preferably guided at least once transversely to the longitudinal axis of the conveying channel. "Transversely to the longitudinal axis" in this context means a direction that includes an angle other than 0° to the longitudinal axis. Preferably, the angle between the direction of the flow path and the longitudinal axis of the conveying channel is at least 45°, more preferably at least 70° or at least 80°, and most preferably substantially 90°. After the combustion air has been guided at least partially along the conveying channel, so that the conveying channel is cooled by the intake combustion air, it passes along the combustion air flow path into the combustion air supply device, where it is further heated and then fed into the combustion chamber.Within the conveying channel, which is preferably designed as a pipe with, for example, a round or n-sided cross-section, is the conveying unit for transporting the solid biomass fuel. The conveying channel can be designed as a stoker channel. The conveying unit is preferably designed as a screw conveyor. The conveying unit transports the solid biomass fuel from a storage area into the combustion chamber. For this purpose, the conveying channel penetrates the boiler casing through a through-opening. The biomass boiler can, for example, have a heating output between 20 kW and 2000 kW.

[0014] In this disclosure, directions and orientations refer to the intended operating condition of a biomass boiler. "Downwards" in this context, for example, means in the direction of gravity.

[0015] In one embodiment of the invention, the intake opening is provided on the underside of the conveying channel. The intake opening is preferably directed downwards, at least in part. Alternatively, it is also possible to arrange the intake opening on the top side of the conveying channel, preferably facing upwards. However, a preferably downward-facing intake opening has the advantage that the already heated and therefore rising ambient air can be drawn in more easily, and the interior of the biomass boiler is better protected from contamination.

[0016] A particularly advantageous way of guiding the combustion air, at least partially, along the conveying channel is achieved by arranging an outer casing on, preferably around, the conveying channel within which the combustion air flow path is guided. The outer casing can, in particular, only completely encircle the conveying channel along a limited longitudinal section of the channel. The outer casing can include the intake opening(s). The outer casing can be made of metal. The outer casing can be attached to the boiler housing and / or to the conveying channel. The outer casing can be at least partially integrated into the boiler housing. To allow ambient air to reach the intake opening in this case, the boiler housing can have at least one ventilation opening. The combustion air flow path is preferably formed between an inner wall of the outer casing and an outer wall of the conveying channel.For this purpose, the inner wall of the outer casing is spaced radially outwards from the outer wall of the conveying channel, preferably between 30 mm and 120 mm, and particularly between 45 mm and 95 mm. In one embodiment of the invention, the combustion air flow path can run along two opposite sides of the conveying channel, preferably between a bottom and a top surface of the conveying channel. Alternatively, the combustion air flow path can run in only one direction around the conveying channel, preferably completely around the conveying channel.

[0017] It is preferred that the boiler casing has an inlet opening for combustion air and that the outer jacket is arranged in the area of ​​the inlet opening, in particular flanged to the boiler casing. In this way, the outer jacket can guide the combustion air into the boiler casing and thus into the combustion air supply device. The inlet opening can be formed by one or more recesses in an outer wall of the boiler casing.

[0018] In one embodiment of the invention, the combustion air flow path leads from an underside of the conveying channel to an upper side of the conveying channel. Preferably, the combustion air flow path is guided from the underside to the upper side within the outer casing.

[0019] In one embodiment of the invention, the combustion air flow path leads from an upper surface of the conveying channel to an underside of the conveying channel. Preferably, the combustion air flow path is guided from the upper surface to the underside within the outer casing.

[0020] The combustion air flow path can initially be guided from a bottom to a top of the conveying channel and then, via a deflection device, back to the bottom of the conveying channel. In an alternative embodiment, the reverse configuration can also be implemented, so that the combustion air flow path can first be guided from a top to a bottom of the conveying channel and then, via a deflection device, back to the top of the conveying channel. By using multiple deflection devices, the combustion air flow path can also be guided between a bottom and a top of the conveying channel several times. By guiding the combustion air from the bottom or top to the top or bottom, the conveying channel is cooled and the combustion air is heated. It is preferred if the flow path is guided within the outer casing between the bottom and the top.For this purpose, the outer casing can also have a deflection device and / or corresponding guide plates, as described.

[0021] A particularly advantageous design results when the combustion air flow path leads into the combustion air supply device at the underside of the conveying channel.

[0022] To supply combustion air to the combustion chamber, it is advantageous to use a blower, particularly a suction blower. Preferably, the suction blower is arranged downstream of the heat exchanger in terms of gas flow. In particular, the blower can be located at an exhaust gas outlet of the biomass boiler. Alternatively, a blower can be provided at the combustion air intake to supply combustion air to the combustion air flow path.

[0023] The combustion air supply system is located at least partially around the combustion chamber within the boiler housing. This allows the combustion air to be introduced into the combustion chamber at various points.

[0024] It is advantageous that the combustion air supply system is designed to distribute the combustion air to several inlet openings in the combustion chamber. These one or more inlet openings can be located on a wall of the boiler casing facing the combustion chamber.

[0025] In one embodiment of the invention, the combustion air supply device can have at least one primary air inlet opening configured to introduce the combustion air preferably directly into a primary combustion zone of the combustion chamber, wherein the at least one primary air inlet opening is preferably arranged below a grate in the combustion chamber. In the primary combustion zone, during operation of the biomass boiler, direct combustion of the solid biomass fuel takes place, particularly on the grate. The at least one primary air inlet opening can be arranged on a wall of the boiler casing facing the combustion chamber. The at least one primary air inlet opening can have a controllable and / or adjustable air damper to regulate and / or control the amount of primary air introduced into the combustion chamber.

[0026] In one embodiment of the invention, the combustion air supply device can have at least one secondary air inlet opening configured to introduce the combustion air preferably directly into a secondary combustion zone of the combustion chamber, wherein the at least one secondary air inlet opening is preferably arranged above a grate in the combustion chamber. The combustion air introduced by the at least one secondary air inlet opening can also be referred to as secondary air. The at least one secondary air inlet opening can be arranged on a wall of the boiler casing facing the combustion chamber. In the secondary combustion zone, afterburning of the resulting flue gases takes place during operation of the biomass boiler. From a gas flow perspective, the secondary combustion zone is arranged downstream of the primary combustion zone. Preferably, the secondary combustion zone is arranged above the primary combustion zone.In an alternative embodiment, ambient air may be drawn in through a further intake opening, and the ambient air drawn in through this further intake opening enters the combustion chamber as combustion air via the at least one secondary air inlet opening. In this case, the at least one secondary air inlet opening is not part of the combustion air supply system, but receives combustion air exclusively via the further intake opening, which is independent of the intake opening. The at least one secondary air inlet opening may have a controllable and / or adjustable air flap to regulate and / or control the amount of secondary air introduced into the combustion chamber.

[0027] In one embodiment of the invention, the combustion air supply device can have at least one tertiary air inlet opening configured to introduce the combustion air preferably directly into a tertiary combustion zone of the combustion chamber, wherein the at least one tertiary air inlet opening is preferably arranged above a grate in the combustion chamber. The combustion air introduced by the at least one tertiary air inlet opening can also be referred to as tertiary air. The tertiary combustion zone can also be referred to as the secondary combustion zone and serves for further afterburning of the combustion gases. The at least one tertiary air inlet opening can be arranged on a wall of the boiler casing facing the combustion chamber. The tertiary combustion zone is fluidically connected to the secondary combustion zone and is preferably located above the grate.In an alternative embodiment, ambient air may be drawn in through a further intake opening, and the ambient air drawn in through this further intake opening enters the combustion chamber as tertiary air via the at least one tertiary air inlet opening. In this case, the at least one tertiary air inlet opening is not part of the combustion air supply system, but receives combustion air exclusively via the further intake opening, which is independent of the intake opening. The at least one tertiary air inlet opening may have a controllable and / or adjustable air flap to regulate and / or control the amount of tertiary air introduced into the combustion chamber.

[0028] The problem stated above is also solved by a method for operating a biomass boiler of the type described. In this method, the combustion air is guided through the combustion air flow path for preheating and / or cooling of the conveying channel. The advantages and effects described above in connection with the biomass boiler are transferable to the method according to the invention.

[0029] The invention is described in more detail below with reference to figures, to which, however, it is not limited. The figures show: Fig. 1 an oblique view of a biomass boiler with a solid fuel conveying system; Fig. 2 a cross-section of a biomass boiler with a solid fuel conveying system; Fig. 3 an oblique view of a biomass boiler with a solid fuel conveying system in a cutaway view; and Fig. 4 A cutaway view of a biomass boiler.

[0030] Fig. 1 shows a biomass boiler 1 for a biomass solid fuel 51 (see Fig. 2 ), in particular pellets and / or wood chips. The biomass boiler 1 has a boiler housing 2, inside of which is a combustion chamber 3 (see Fig. 2 ) is arranged. To convey the solid biomass fuel 51 into the combustion chamber 3, the biomass boiler 1 has a solid fuel conveying device 4. The illustrated solid fuel conveying device 4 has a conveying channel 5, inside of which is a conveying unit 6 in the form of a screw conveyor 7 (see Fig. 2 The conveying channel 5 is arranged as follows: A feed opening 8 is provided on the upper side 32 of the conveying channel 5 in the area of ​​the end facing away from the biomass boiler 1. The solid biomass fuel 51 enters the interior of the conveying channel 5 via a valve unit 9 flanged to the feed opening 8, in particular a rotary valve, and can from there be conveyed towards the combustion chamber 3. The conveying channel 5 is inclined downwards towards the end facing away from the biomass boiler 1.

[0031] Fig. 2 shows a longitudinal section of the biomass boiler 1. The auger 7 is driven by a motor 10 (see Fig. 1 The biomass solid fuel 51 is conveyed from the feed opening 8 to the combustion chamber 3 by the spiral 11 along the hollow shaft 12 of the auger 7. A grate 13 is arranged inside the combustion chamber 3. The combustion chamber 3 is lined with fireclay bricks 14 for heat protection.

[0032] To supply combustion air V to the combustion chamber 3, the biomass boiler 1 has a combustion air supply device 15 inside the boiler housing 2 for distributing and supplying the combustion air V. To draw in the combustion air V, the biomass boiler 1 may have a suction fan 28 (see Fig. 1 ), which is arranged at an exhaust gas outlet of the biomass boiler 1. The combustion air supply device 15 can have a cavity 16 between walls 17 of the boiler housing 2. The cavity 16 can also be bounded, for example, by pipes and / or baffles. Combustion air V can be directed through this cavity 16 to one or more primary air inlet openings 18. In the illustration shown, the one or more primary air inlet openings 18 are arranged below the grate 13. The combustion air V can also be directed via the combustion air supply device 15, in particular the cavity 16, to one or more secondary air inlet openings 19 and / or one or more tertiary air inlet openings 20 and finally into the combustion chamber 3.Alternatively, at least one further intake opening (not shown) can be provided in the boiler housing 2, through which ambient air U can be drawn in and directed to at least one secondary air inlet opening 19 and / or at least one tertiary air inlet opening 20, and finally into the combustion chamber 3. In this case, ambient air U or combustion air V from the combustion air supply device 15 reaches only the primary air inlet openings 18, but not the at least one secondary air inlet opening 19 and / or the at least tertiary air inlet opening 20. In this alternative variant, the at least one secondary air inlet opening 19 and / or the at least one tertiary air inlet opening 20 draw ambient air U exclusively through the at least one further intake opening. The inlet openings 18, 19, 20 can be arranged on a wall of the boiler housing 17 facing the combustion chamber 3.The fireclay blocks 14 can have corresponding recesses 50 for the inlet openings 18, 19, 20. The primary air inlet openings 18 are designed to direct combustion air V as primary combustion air VP preferably directly into a primary combustion zone 21. In the illustration shown, the primary combustion air VP enters the primary combustion zone 21 through the grate 13. In the primary combustion zone 21, the biomass solid fuel 51 is combusted directly during operation of the biomass boiler 1. Preferably, the primary air inlet openings 18 are arranged below the grate 13, as already mentioned. The secondary air inlet openings 19 are designed to direct combustion air V as secondary combustion air VS preferably directly into a secondary combustion zone 22. In the secondary combustion zone 22, the combustion gases produced during the operation of the biomass boiler 1 undergo further combustion.The secondary combustion zone 22 is arranged downstream of the primary combustion zone 21, specifically above it, in terms of gas flow. The tertiary air inlet openings 20 are designed to direct combustion air V, preferably directly into a tertiary combustion zone 23, as tertiary combustion air VT. The tertiary combustion zone 23 is connected to the secondary combustion zone 22 in terms of flue gas flow. In the tertiary combustion zone 23, also referred to as the burnout zone, further afterburning of the combustion gases takes place to reduce emissions.

[0033] Due to the high temperatures in the combustion chamber 3, which can reach up to 1100 °C, parts of the biomass boiler 1 that are not protected by fireclay or cooled can be damaged. In particular, parts of the solid fuel conveying system 4, such as the conveying channel 5 or the auger 7, can be damaged by the heat during periods when no new solid biomass fuel 51 is being conveyed.

[0034] To reduce the risk of damage to the solid fuel conveying device 4, the invention provides that at least one intake opening 24 is provided on the solid fuel conveying device 4 and that a combustion air flow path 25 leads from the intake opening 24 to the conveying channel 5 and further into the combustion air supply device 15. The combustion air flow path 25 is guided at least partially along the conveying channel 5.

[0035] In the illustration shown according to Fig. 2 An outer shell 26 is provided, which essentially completely surrounds a longitudinal section of the conveying channel 5. The outer shell 26 is in Fig. 2 The outer casing 26 is at least partially incorporated into the boiler housing 2. On the underside 27 of the conveying channel 5, the outer casing 26 has several downward-facing, slot-shaped intake openings 24 through which ambient air U can be drawn in as combustion air V. To allow the ambient air U to reach the intake openings 24, which are located inside the boiler housing 2, the boiler housing 2 can have one or more ventilation openings 52, which, in the illustrated embodiment, are located below the conveying channel 5. The outer casing 26 is connected to the boiler housing 2 and to a flange 29 of the conveying channel 5. In the illustration, the combustion air flow path 25 is formed between an inner wall 30 of the outer casing 26 and an outer wall 31 of the conveying channel 5. The inner wall 30 and the outer wall 31 are preferably spaced at least 40 mm apart, and in particular at least 45 mm apart.The combustion air V flowing past is thus in contact with the conveying channel 5.

[0036] The combustion air flow path 25 initially runs from the intake openings 24 on the underside 27 of the conveying channel 5 along a first flow path section 33a of the outer shell 26 to an upper surface 32 of the conveying channel 5. On the upper surface 32, the outer shell 26 has a deflector 34, at which the combustion air V is deflected and to which a second flow path section 33b connects, leading from the upper surface 32 back to the underside 27 of the conveying channel 5. A partition 35 of the outer shell 26 separates the first 33a from the second flow path section 33b. The partition 35 has a preferably substantially horizontally oriented opening 36 through which the combustion air V passes from the first flow path section 33a into the second flow path section 33b.In terms of fluid dynamics, the combustion air V in the illustrated diagram flows upwards from the intake openings 28 along the first flow path section 33a during operation of the biomass boiler 1, then through the opening 36 in the partition 35 and further downwards along the second flow path section 33b. The first 33a and the second flow path section 33b can each run along two opposite sides of the conveying channel 5 (see figure). Fig. 4 ).

[0037] On the underside 27 of the conveying channel 5, the combustion air V enters the combustion air supply device 15 through slot-like inlet openings 37 and can be supplied to the combustion chamber 3 as primary air VP, secondary air VS, and / or tertiary air VT, as described above. In this case, the intake openings 24 serve as common intake openings 24 for primary combustion air VP, secondary combustion air VS, and / or tertiary combustion air VT. Alternatively, as also described above, the combustion air supply device 15 can introduce only primary air VP into the combustion chamber 3. The secondary air VS and the tertiary air VT can be drawn in via at least one further intake opening (not shown) in the boiler housing 2, which is independent of the intake openings 24.

Claims

1. Biomass heating boiler (1) for a biomass solid fuel (51), in particular pellets and / or wood chips, comprising: a boiler housing (2); a combustion chamber (3); a solid fuel conveying device (4) for feeding the combustion chamber (3) with the biomass solid fuel (51), wherein the solid fuel conveying device (4) comprises a conveying channel (5) and a conveying unit (6) for conveying the biomass solid fuel (51) within the conveying channel (5); a combustion air supply device (15) within the boiler housing (2) for distributing and supplying combustion air (V), in particular primary (VP) and / or secondary (VS) and / or tertiary air (VT), into the combustion chamber (3), wherein the combustion air supply device (15) is arranged within the boiler housing (2) at least partially around the combustion chamber (3) and the combustion air supply device (15) is configured to distribute the combustion air (V) to a plurality of inlet openings (18, 19, 20) into the combustion chamber (3); and an intake opening (24) for the combustion air (V), wherein the intake opening (24) is provided on the solid fuel conveying device (15) and a combustion air flow path (25) for the combustion air (V) leads from the intake opening (24) to the conveying channel (5) and further into the combustion air supply device (15), wherein the combustion air flow path (25) is guided at least in sections along the conveying channel (5).

2. Biomass heating boiler (1) according to claim 1, characterized in that the intake opening (24) is provided on an underside (27) of the conveying channel (5).

3. Biomass heating boiler (1) according to claim 1 or 2, characterized in that an outer jacket (26) is arranged on, preferably around, the conveying channel (5), within which the combustion air flow path (25) is guided.

4. Biomass heating boiler (1) according to claim 3, characterized in that the boiler housing (2) has an inlet opening (37) for combustion air (V) and the outer jacket (26) is arranged in the region of the inlet opening, in particular is flanged to the boiler housing (2).

5. Biomass heating boiler (1) according to one of claims 1 to 4, characterized in that the combustion air flow path (25) leads from an underside (27) of the conveying channel (5) to an upper side (32) of the conveying channel (5).

6. Biomass heating boiler (1) according to one of claims 1 to 5, characterized in that the combustion air flow path (25) leads from an upper side (32) of the conveying channel (5) to an underside (27) of the conveying channel (5).

7. Biomass heating boiler (1) according to one of claims 1 to 6, characterized in that the combustion air flow path (25) opens at the underside (27) of the conveying channel (5) into the combustion air supply device (15).

8. Biomass heating boiler (1) according to one of claims 1 to 7, characterized in that a blower, in particular a suction blower (28), is provided for conveying the combustion air (V).

9. Biomass heating boiler (1) according to one of claims 1 to 8, characterized in that the combustion air supply device (15) comprises at least one primary inlet opening (18), which is configured to introduce the combustion air (V) preferably directly into a primary combustion zone (21) of the combustion chamber (3), wherein the at least one primary inlet opening (18) is preferably arranged below a grate (13) in the combustion chamber (3).

10. Biomass heating boiler (1) according to one of claims 1 to 9, characterized in that the combustion air supply device (15) comprises at least one secondary inlet opening (19), which is configured to introduce the combustion air (V) preferably directly into a secondary combustion zone (22) of the combustion chamber (3), wherein the at least one secondary inlet opening (19) is preferably arranged above a grate (13) in the combustion chamber (3).

11. Biomass heating boiler according to one of claims 1 to 10, characterized in that the combustion air supply device (15) comprises at least one tertiary inlet opening (20), which is configured to introduce the combustion air (V) preferably directly into a tertiary combustion zone (23) of the combustion chamber (3), wherein the at least one tertiary inlet opening (20) is preferably arranged above a grate (13) in the combustion chamber (3).

12. Method for operating a biomass heating boiler (1) according to one of claims 1 to 11, wherein the combustion air (V) is guided through the combustion air flow path (25) for preheating thereof and / or for cooling the conveying channel (5).