Biomass boiler

Abstract

The invention relates to a biomass boiler (1) with an exhaust gas duct (3) which, together with a combustion chamber (2), forms a hot gas zone. Outside the hot gas zone, a plasma chamber (5) is provided, connected to the exhaust gas duct (3), for generating a low-temperature plasma. A blower (6) is provided for generating a conveying flow (7) that passes through the plasma chamber (5) to convey the low-temperature plasma into the exhaust gas duct (3). The plasma chamber (5) is connected to an ambient air supply (10). To reduce potential odor emissions from existing biomass boilers (1) in a space-saving and retrofittable manner, it is proposed that the plasma chamber (5) be connected to the boiler housing (4) or supported by the exhaust gas duct (3).

Description

[0001] The invention relates to a biomass boiler with an exhaust gas line which, together with a combustion chamber, forms a hot gas area, wherein outside the hot gas area a plasma chamber flow-connected to the exhaust gas line for generating a low-temperature plasma and a blower for generating a conveying flow are provided which penetrates the plasma chamber for conveying the low-temperature plasma into the exhaust gas line and wherein the plasma chamber is flow-connected to an ambient air supply.

[0002] In the combustion chambers of biomass boilers for pellets, wood, or wood chips, the combustion of the biomass produces exhaust gas, which is discharged from the combustion chamber via an exhaust pipe. This exhaust gas typically contains residual organic components, which can lead to unpleasant odors.

[0003] While it is known in the field of waste incineration plants to treat exhaust gases with plasma to neutralize organic components, the high temperatures of the exhaust gases, well over 200°C, pose a risk of damage to conventional plasma generators, which can produce a low-temperature plasma using high voltage, and in particular a reduced service life. EP 2123344 A1 discloses, for example, a plasma chamber to solve this problem, which is connected to the exhaust gas line of a biomass boiler via a plasma line and is thus protected from the high temperatures.

[0004] Furthermore, there is a need to be able to retrofit existing biomass boilers in boiler rooms of single-family and multi-family houses with minimal effort and without structural changes, despite limited space in the boiler rooms.

[0005] The invention is therefore based on the objective of reducing a possible odor burden from existing biomass boilers of the type described above in a space-saving and retrofittable manner.

[0006] The invention solves the problem by connecting the plasma chamber to the boiler housing or supporting it on the exhaust pipe.

[0007] As a result of this design, the low-temperature plasma can be generated outside the hot gas area and conveyed into the exhaust duct by means of the blower, without the temperatures prevailing there affecting the plasma chamber. The highly reactive low-temperature plasma reacts with the organic components of the exhaust gas, breaking them down and / or oxidizing them, thus reducing odor emissions. At the same time, the blower prevents a backflow of hot exhaust gases towards the plasma chamber.Because the components required for generating the low-temperature plasma do not need to be located in the exhaust gas stream, thanks to the features of the invention, they can be easily retrofitted to an existing exhaust gas line. Both the plasma chamber and the blower required for the conveying flow can be designed to be correspondingly small, depending on their dimensions, thus reducing the required installation space. By providing thermal separation between the hot gas area and the plasma chamber and the blower, these components can be operated at a temperature range preferably below 200°C, allowing for non-destructive operation. Preferably, the plasma chamber also has a heat-insulating wall.

[0008] In general, inert gases are recommended for generating low-temperature plasma in the prior art; however, according to the invention, the plasma chamber can be connected to an ambient air supply only. This offers the advantage that only an ambient air supply needs to be provided for retrofitting, and neither additional storage space for inert gases nor further structural modifications are required. Furthermore, the ambient air is at room temperature and can be used not only to cool the plasma chamber and the blower, but also, by applying a sufficiently high voltage in the plasma chamber, at least partially converted into a low-temperature plasma state.

[0009] If the biomass boiler is housed in a boiler casing, and part of the casing incorporates the flue gas duct, causing the flue gas duct to run both inside and outside the boiler casing, the plasma chamber can be connected to the boiler casing. This allows for a direct connection of the plasma chamber to the flue gas duct or a flow connection between the plasma chamber and the flue gas duct, without requiring the plasma chamber to be supported by the flue gas duct for load-bearing purposes, as the forces acting on it can be transferred via the boiler casing. Furthermore, mounting the plasma chamber to the boiler casing is a simple, space-saving process that can be carried out during routine maintenance, without directly impacting surrounding structures.

[0010] Retrofitting a biomass boiler is particularly easy if the boiler casing has a service hatch. In such a case, the plasma chamber can be attached to the service hatch of the boiler casing. This eliminates the need to subsequently fabricate a connection to the boiler casing; only the service hatch needs to be replaced.

[0011] In one embodiment, the plasma chamber can be supported on the exhaust pipe. Particularly if the plasma chamber is connected to the exhaust pipe outside the biomass boiler, this offers the advantage that the biomass boiler does not need to be structurally modified to enable the odor reduction according to the invention. In this case as well, the plasma chamber can be thermally separated and connected directly to the exhaust pipe, allowing them to be flow-connected in a space-saving manner.

[0012] To further reduce the odor burden of the organic components in the exhaust gas, the exhaust pipe can be equipped with an activated carbon filter in the section following the flow connection to the plasma chamber. This filter not only removes the organic components, thus physically purifying the exhaust gas, but also increases the residence time of the organic components in close proximity to the low-temperature plasma by retaining them and allowing them to undergo further chemical reaction with the plasma.

[0013] In areas with particularly limited space around a retrofitted biomass boiler, it can be advantageous for the plasma chamber and the blower to form a single, easily retrofittable unit. The blower can be positioned either on the side of the plasma chamber facing away from the exhaust pipe or on the side facing it. Particularly advantageous conditions arise when the blower is located on the side of the plasma chamber facing away from the exhaust pipe, especially between an ambient air supply and the plasma chamber. Consequently, not only is the blower exposed to lower temperatures, but the highly reactive low-temperature plasma also does not flow through the blower. This makes the blower less susceptible to the surface-oxidizing effect of the low-temperature plasma, allowing it to be designed smaller and with a longer service life, further improving retrofitability and maintenance intervals.

[0014] The invention is illustrated in the drawing as an example. It shows Fig. 1 a schematic section through a biomass boiler with a plasma chamber supported on the exhaust pipe, Fig. 2 a schematic, partially cut-away section through a boiler housing of the biomass boiler of the Fig. 1 with a plasma chamber attached to the maintenance hatch of the boiler housing on a larger scale and Fig. 3 a schematic section through a biomass boiler with a plasma chamber flow-connected to the exhaust gas line

[0015] A biomass boiler 1 according to the invention comprises a combustion chamber 2 and an exhaust gas duct 3, which runs partly through the boiler housing 4 and partly outside the boiler housing 4. The combustion chamber 2 and the exhaust gas duct 3 together form a hot gas section.

[0016] Outside this hot gas area, a plasma chamber 5 and a blower 6 are arranged. The blower 6 generates a conveying flow 7 that permeates the plasma chamber 5 and conveys the low-temperature plasma generated in the plasma chamber 5 via a flow connection 8 into the exhaust line 3.

[0017] Preferably, the blower 6 is arranged on the side of the plasma chamber 5 facing away from the exhaust pipe 3 and forms a unit 9 with it. In one embodiment, the plasma chamber 5 is connected to an ambient air supply 10 on this side, so that ambient air at room temperature is conveyed into the plasma chamber 5 by the conveying flow 7.

[0018] Advantageously, a heat exchanger 11 is located within the boiler housing 4, in which the combustion chamber 2 is arranged, as part of the exhaust gas line 3, to which the flow connection 8 of the plasma chamber 5 with the exhaust gas line 3 is downstream.

[0019] In Fig. 1 The plasma chamber 5 is flow-connected to the exhaust pipe 3 outside the boiler housing 4 and supported on it.

[0020] In the embodiments of the Fig. 2 and Fig. 3 Each assembly 9, consisting of a plasma chamber 5 and a blower 6, is attached to a maintenance hatch 12 of the boiler housing 4 and is flow-connected to the exhaust gas line 3 running inside the boiler housing 4. The exhaust gas line 3 follows this flow connection 8. Fig. 2 an activated carbon filter 13.

Claims

1. Biomass boiler (1) with an exhaust gas line (3) which together with a combustion chamber (2) forms a hot gas region, wherein outside the hot gas region a plasma chamber (5) flow-connected to the exhaust gas line (3) for generating a low-temperature plasma and a blower (6) for generating a conveying flow (7) are provided, which penetrates the plasma chamber (5) for conveying the low-temperature plasma into the exhaust gas line (3) and wherein the plasma chamber (5) is flow-connected to an ambient air supply (10), characterized by the fact that the plasma chamber (5) is connected to the boiler housing (4) or supported on the exhaust pipe (3).

2. Biomass boiler (1) according to claim 1, characterized by the fact that the plasma chamber (5) is attached to a maintenance hatch (12) of the boiler housing (4).

3. Biomass boiler (1) according to claim 1 or 2, characterized by the fact thatThe flow connection (8) of the plasma chamber (5) with the exhaust gas line (3) is downstream of a heat exchanger (11) for removing the heat of the exhaust gas carried in the exhaust gas line (3).

4. Biomass boiler (1) according to one of claims 1 to 3, characterized by the fact that the exhaust pipe (3) has an activated carbon filter (13) in the area following the flow connection (8) to the plasma chamber (5).

5. Biomass boiler (1) according to one of claims 1 to 4 characterized by the fact that the plasma chamber (5) and the blower (6) form a retrofittable assembly (9).

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