Apparatus for treating exhaust gas from a small combustion plant

Abstract

The invention relates to an apparatus for treating exhaust gas from a small combustion plant, in particular for separating particulate matter, the apparatus comprising: a gas supply pipe (1) for the exhaust gas coming from the small combustion plant; a treatment chamber (2); and a gas outlet pipe (3) for the purified exhaust gas. The treatment chamber (2) is at least partially filled with liquid, wherein the outlet opening (4) from the gas supply pipe (1) is located below the liquid level (5) and is surrounded by a flange-type perforated plate (6) having perforations (7) for the passage of gas that are arranged in a grid shape. The perforated plate (6) is surrounded by side walls (8) facing downwards away from the liquid level (5), with a gap (9) remaining between the side walls (8) of the perforated plate (6) and the side walls of the treatment chamber (2). The bottom (10) of the treatment chamber (2) is inclined towards an outflow opening (11) for the washing liquid, which opening is placed at the lowest point.

Description

Technical field

[0001] The invention relates to a device for treating exhaust gases from a small combustion plant, in particular for separating fine dust, comprising a gas supply pipe for the exhaust gas coming from the small combustion plant, a treatment chamber and a gas outlet pipe for the cleaned exhaust gas. State of the art

[0002] Small combustion plants that use wood, wood pellets, or coal as fuel are commonly found in private homes, where they supplement or replace conventional heating systems. The popularity of pellet stoves for private use is growing, particularly due to the sustainability of renewable fuels. A disadvantage of these systems is that the combustion of biomass fuel produces larger quantities of particulate matter, which also poses a burden on the environment. Various methods exist to largely remove particulate matter from the exhaust gases. For example, filters or spray scrubbers can be used, but these are too expensive, space-consuming, and require too much maintenance, especially for small combustion plants, and are therefore not economically viable. It is also possible to reduce particulate matter emissions by controlling the humidity in the combustion chamber.However, this leads to corrosion or slagging of heat exchanger surfaces adjacent to the combustion chamber, which negatively affects the service life of the system. CH 676 436 A5 discloses the features of the preamble of claim 1. Description of the invention

[0003] The object of the present invention is to provide a device for treating exhaust gases from a small combustion plant, which can be implemented cost-effectively with few components and which enables effective and efficient cleaning of the exhaust gases, in particular the separation of particulate matter. The device should also be easy to clean and, ideally, operate fully automatically via the plant control system, requiring minimal maintenance from the user.

[0004] This problem is solved by the present invention in that the treatment chamber is at least partially filled with liquid, wherein the outlet opening from the gas supply pipe is located below the liquid level and is flange-shaped and surrounded by a perforated plate with grid-like holes for gas passage, and wherein the perforated plate is bordered by side walls extending downwards from the liquid level, with a gap remaining between the side walls of the perforated plate and the side walls of the treatment chamber, and wherein the bottom of the treatment chamber is inclined towards a drain opening for the washing liquid located at the lowest point. The exhaust gas entering the treatment chamber spreads out below the perforated plate, and individual bubbles pass through the holes and rise to the surface.The downward-facing side walls of the perforated plate prevent the introduced exhaust gas from rising laterally, forcing the entire volume to flow through the holes to the surface. The numerous holes increase the reaction surface area between the exhaust gas and the liquid. For the volume of exhaust gas and the level of particulate matter pollution, a liquid level of approximately 3 cm above the perforated plate to the liquid surface is required in an average system. The individual holes, for example, each have a diameter of 3 mm. Due to the gap between the side walls of the perforated plate and the side walls of the treatment chamber, the contaminants released into the liquid can slide downwards towards the bottom of the treatment chamber. Because of the inclined bottom of the treatment chamber, the contaminants are then directed further towards the drain opening.The advantage of this device is that it can be manufactured very cost-effectively, essentially using only formed sheet metal parts. The water bath exhaust gas scrubbing is sufficient for the exhaust gas volumes produced by a small combustion plant, and no replaceable filters are required, nor is the combustion chamber clogged with slag from the addition of substances or water.

[0005] Another key feature is the S-shaped siphon located after the drain opening for the washing liquid. The upper bend of this siphon defines the liquid level in the treatment chamber. When refilling to compensate for water lost through evaporation, the siphon ensures the correct liquid level is always maintained, eliminating the need for complex valves and controls. The liquid level can never rise above the height of the lower inner wall of the siphon's upper bend. Any excess water drains away through the outlet.

[0006] A further preferred feature is the provision of a liquid supply line in the lower bend of the S-shaped siphon, connected to the siphon via a shut-off valve. This allows water to be periodically refilled to maintain a constant liquid level in the treatment chamber, while simultaneously flushing out contaminants that collect in the lower bend of the siphon towards the drain. Since this periodic flushing can be automated, the entire device can operate essentially maintenance-free for extended periods.

[0007] Alternatively or additionally, another feature is the provision of a liquid inlet, connected laterally to the treatment chamber via a shut-off valve, in a vertical direction above and / or below the perforated plate. Should contaminants accumulate on the top of the perforated plate or on the bottom of the treatment chamber, depending on the system, targeted flushing processes can be carried out at the corresponding height within the treatment chamber via the lateral inlets to transport the contaminants towards the drain. All inlets or only some of them may be present for this purpose.

[0008] According to a possible preferred embodiment, flow elements are provided in the liquid within the treatment chamber above the perforated plate. These flow elements serve to increase the gas exchange between the incoming exhaust gas and the liquid, preferably consisting of a layer of steel wool. Should a system require a higher exchange rate between gas and liquid, additional flow elements can be provided. These reduce the bubble size of the incoming exhaust gas and increase its residence time in the liquid. As a particularly simple example, a layer of steel wool can be provided above the perforated plate. In this case, it is recommended to provide a corresponding lateral liquid inlet above the perforated plate to periodically flush the flow element free of contaminants.

[0009] Furthermore, a preferred feature is that the small combustion plant is a biomass combustion furnace, in particular for wood pellets, wherein the plant includes a fluidized bed and is thus operated under positive pressure. Such a combustion furnace is described, for example, in EP 2827059 A1. This has the advantage that, due to the fluidized bed, the introduced biomass is combusted as completely as possible with low particulate matter emissions, and that the plant is already operated under positive pressure due to the airflow in the fluidized bed. This eliminates the need for an additional blower for operating the exhaust gas treatment device, which further simplifies the plant and makes it more cost-effective to implement.

[0010] Finally, an additional preferred feature is that the heat transferred from the exhaust gas to the liquid in the treatment chamber can be dissipated via a heat exchanger connected to the treatment chamber and thus supplied for heating and / or hot water preparation. During operation of the device, temperatures of approximately 65°C can occur in the treatment chamber. This heat, which would otherwise be lost as waste heat, can be utilized via a heat exchanger connected to the treatment chamber, thereby increasing the efficiency of the entire small combustion plant. Brief description of the drawings

[0011] The invention will now be described in greater detail with reference to an exemplary embodiment and the accompanying figures. Fig. 1 a schematic lateral sectional view of a device according to the invention and Fig. 2 a schematic top view of a device according to the invention. Way(s) to implement the invention

[0012] In Fig. 1 Figure 1 schematically illustrates an embodiment of a device according to the invention in a side sectional view. Several gas supply lines 1 extend into a treatment chamber 2, which is partially filled with water. The outlet openings 4 of the gas supply lines 1 are located below the liquid level 5 of the water in the treatment chamber 2. All gas supply lines 1 are surrounded at their outlet openings 4 by a perforated plate 6, which is flange-shaped around all of them.

[0013] As particularly in Fig. 2As can be seen in a schematic top view of the treatment chamber 2 with the cover plate removed, in the exemplary embodiment eight gas supply pipes 1 are introduced, each of which is surrounded below the liquid level 5 by a common perforated plate 6. The perforated plate 6 has a plurality of uniformly distributed holes 7 through which the inflowing gas can rise in the form of small bubbles.

[0014] The edges of the perforated plate 6 are curved downwards, forming side walls 8, so that the gas introduced into the treatment chamber 2 can only flow through the perforated plate 6 and not around it. Simultaneously, a gap 9 remains between the side walls of the treatment chamber 2 and the side walls 8 of the perforated plate 6, through which any contaminants deposited on the perforated plate can be drained towards a drain opening 11. The bottom 10 of the treatment chamber 2 is also inclined towards the drain opening 11 to drain away any contaminants. The gas rising in bubbles in the liquid is cleaned of fine dust and then exits the device via a gas outlet pipe 3.

[0015] An S-shaped siphon 12 is connected to the drain opening 11. A liquid supply line 16, connected via a shut-off valve 15, is attached to the lower bend 14 of the siphon 12. This line allows for the periodic flushing of the siphon 12 and the equalization of the liquid level 5 in the treatment chamber 2 to its maximum height. The maximum height of the liquid level 5 is determined by the height of the upper bend 13 of the siphon 12.

[0016] Liquid supply lines can alternatively or additionally be arranged on the side wall of treatment chamber 2, either above or below the perforated plate, to periodically flush areas of heavier contamination. A heat exchanger (not shown) can also be connected to treatment chamber 2 to utilize the heat transferred from the exhaust gas to the liquid in treatment chamber 2. To further increase the reactive surface area between the gas and liquid, or the residence time of the gas in the liquid, flow media, for example in the form of a layer of steel wool, can be provided above the perforated plate 6.

Claims

1. Device for the treatment of exhaust gases from a small-scale furnace, in particular for the separation of particulate matter, comprising a gas supply pipe (1) for the exhaust gas coming from the small-scale furnace, a treatment chamber (2) and a gas outlet pipe (3) for the purified exhaust gas, wherein the treatment chamber (2) is at least partially filled with liquid, and wherein the outlet opening (4) from the gas supply pipe (1) is located below the liquid level (5) and is surrounded in the form of a flange by a perforated plate (6) with holes (7) arranged in a grid pattern for the passage of gas, and wherein the perforated plate (6) is surrounded by side walls (8) pointing downwards away from the liquid level (5), wherein a gap (9) remains between the side walls (8) of the perforated plate (6) and the side walls of the treatment chamber (2), characterized in that the bottom (10) of the treatment chamber (2) is inclined in the direction of an outflow opening (11) for the washing liquid located at the lowest point, an S-shaped siphon (12) being arranged adjacent to the outflow opening (11) for the washing liquid, the upper bend (13) of which defines the liquid level (5) in the treatment chamber (2).

2. Device for the treatment of exhaust gases of a small-scale furnace according to claim 1, characterized in that a liquid supply line (16) connected to the siphon (12) via a shut-off valve (15) is provided in the lower bend (14) of the S-shaped siphon (12).

3. Device for the treatment of exhaust gases of a small-scale furnace according to claim 1 or 2, characterized in that a liquid supply line connected laterally to the treatment chamber (2) via a shut-off valve is provided in the vertical direction above and / or below the perforated plate (6).

4. Device for the treatment of exhaust gases of a small-scale furnace according to one of claims 1 to 3, characterized in that flow bodies are provided in the liquid in the treatment chamber (2) above the perforated plate (6), which serve to increase the gas exchange between the incoming exhaust gas and the liquid, a layer of steel wool preferably being provided as the flow body.

5. Device for the treatment of exhaust gases of a small-scale furnace according to one of claims 1 to 4, characterized in that the heat emitted by the exhaust gas to the liquid in the treatment chamber (2) can be dissipated via a heat exchanger connected to the treatment chamber (2) and can thus be supplied to the heating and / or hot water preparation.

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