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

DEVICE FOR TREATMENT OF EXHAUST GASES FROM A SMALL COMBUSTION PLANT Technical area

[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 purified exhaust gas. State of the art

[0002] Small combustion systems that use wood, wood pellets or coal as fuel are often found in private households, where they supplement or replace conventional heating systems. The sustainability of renewable fuels is leading to a growing proportion of pellet stoves for private use. The disadvantage of these systems is that the biomass fuel produces large quantities of particulate matter during combustion, which in turn represents a burden on the environment. Various methods are known to be able to largely remove particulate matter from exhaust gases. Filters or spray scrubbers can be used for this purpose, but these are particularly costly, space-consuming and require too much maintenance, especially for small combustion systems, and are therefore not economically viable. It is also possible to reduce particulate matter pollution by controlling the humidity in the combustion chamber.However, this leads to the heat exchanger surfaces adjacent to the combustion chamber corroding or slagging, which negatively affects the service life of the system. Description of the invention

[0003] The object of the present invention is to create a device for treating exhaust gases from a small combustion plant that can be implemented cost-effectively with a few components and that enables effective and efficient purification of the exhaust gases, in particular the separation of particulate matter. The system should also be easy to clean and operate fully automatically via the system control system, requiring virtually no maintenance for the user.

[0004] This object is achieved 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 lies below the liquid level and is surrounded in a flange-like manner by a perforated plate with grid-like holes for the gas passage, and wherein the perforated plate is bordered by side walls pointing downwards away from the liquid level, wherein a gap remains between the side walls of the perforated plate and the side walls of the treatment chamber, and in that the floor of the treatment chamber is inclined towards an outlet opening for the scrubbing liquid located at the lowest point. The exhaust gas entering the treatment chamber is distributed 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 sideways, so that the entire volume must flow through the holes to the surface. The large number of holes increases the reaction surface between the exhaust gas and the liquid. For the exhaust gas quantities that occur and the degree of particulate matter pollution to be taken into account, an average system requires a liquid overhang of around 3 cm above the perforated plate up to the liquid surface. The individual holes, for example, each have a diameter of 3 mm. Due to the circumferential gap between the side walls of the perforated plate and the side walls of the treatment chamber, the contaminants now released into the liquid can slide down towards the floor of the treatment chamber. Due to the sloped floor of the treatment chamber, the contaminants are further directed towards the drain opening.The advantage of this device is that it can be manufactured particularly cost-effectively, essentially from formed sheet metal parts. The flue gas scrubbing in the water bath is sufficient for the flue gas volumes generated by a small combustion plant, and no replaceable filters are required, nor is the combustion chamber slagged by the addition of substances or water.

[0005] A further preferred feature is that an S-shaped siphon is arranged adjacent to the drain opening for the washing liquid, the upper bend of which defines the liquid level in the treatment chamber. The siphon ensures that the correct level is always achieved when replenishing water lost through evaporation, without the need for complicated valves and controls. The liquid level can never rise higher than the height of the lower inner wall of the upper bend of the siphon. If more water is added, it flows out via the drain.

[0006] A further preferred feature is that a liquid supply line connected to the siphon via a shut-off valve is provided in the lower bend of the S-shaped siphon. This allows, on the one hand, water to be periodically refilled to keep the liquid level in the treatment chamber constant, and, at the same time, the contaminants accumulating in the lower bend of the siphon can be flushed out toward the drain. Since this periodic flushing can be automated, the entire device can be operated essentially maintenance-free over long periods of time.

[0007] Alternatively or additionally, a further feature is the provision of a liquid supply line, vertically above and / or below the perforated plate, connected to the treatment chamber via a shut-off valve. If, depending on the system, contaminants accumulate on the top of the perforated plate or at the bottom of the treatment chamber, targeted flushing processes can be carried out through the lateral supply lines at the appropriate height in the treatment chamber to transport the contaminants toward the drain. All supply lines or just individual ones can be provided.

[0008] According to a possible preferred embodiment, flow bodies are provided in the liquid in the treatment chamber above the perforated plate, which serve to increase the gas exchange between the incoming exhaust gas and the liquid, wherein a layer of steel wool is preferably provided as the flow body. Should a system require a higher exchange between gas and liquid, further flow bodies can be provided, which on the one hand reduce the bubble size of the incoming exhaust gas and on the other hand increase the 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 supply line above the perforated plate in order to periodically flush the flow body free of contaminants.

[0009] A further preferred feature is that the small combustion plant is a combustion furnace for biomass, in particular wood pellets, wherein the plant comprises a fluidized bed and is thus operated at positive pressure. Such a combustion furnace is described, for example, in EP 2827059 A1. This has the advantage that, thanks to the fluidized bed, the introduced biomass is burned as completely as possible with minimal particulate matter pollution, and that the plant is already operated at positive pressure due to the air flow in the fluidized bed. This eliminates the need for an additional fan to operate the exhaust gas treatment device, which further simplifies the plant and makes it 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 to the heating and / or hot water system. 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 harnessed via a heat exchanger connected to the treatment chamber, increasing the efficiency of the entire small-scale combustion system. Short description of the drawings

[0011] The invention will now be described in greater detail using an exemplary embodiment and with the aid of the accompanying figures. Figure 1 shows a schematic side sectional view of a device according to the invention, and Figure 2 shows a schematic plan view of a device according to the invention. Way(s) of carrying out the invention

[0012] Fig. 1 schematically shows 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 pipes 1 are located below the liquid level 5 of the water in the treatment chamber 2. All gas supply pipes 1 are surrounded at their outlet openings 4 by a perforated plate 6 that surrounds them all in a flange-like manner.

[0013] As can be seen particularly in Fig. 2 in a schematic plan 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 by a common perforated plate 6 below the liquid level 5. The perforated plate 6 has a plurality of evenly 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 and form side walls 8 so that the gas fed into the treatment chamber 2 can only flow through the perforated plate 6 and not past it. At the same time, 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 floor 10 of the treatment chamber 2 is also inclined towards the drain opening 11 to drain away any contaminants that arise. 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. In the area of ​​the lower bend 14 of the siphon 12, a liquid supply line 16 is connected via a shut-off valve 15. This line can be used to periodically flush the siphon 12 and also to equalize 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] Alternatively or additionally, liquid supply lines can also be arranged on the side wall of the treatment chamber 2, either above or below the perforated plate, in order to periodically flush areas of greater contamination. A heat exchanger (not shown) can also be connected to the treatment chamber 2 in order to further utilize the heat transferred from the exhaust gas to the liquid in the 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 bodies, for example in the form of a layer of steel wool, can be provided above the perforated plate 6.

Claims

Device for treating exhaust gases from a small combustion plant, in particular for separating particulate matter, 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 cleaned exhaust gas, characterized in that the treatment chamber (2) is at least partially filled with liquid, wherein the outlet opening (4) from the gas supply pipe (1) lies below the liquid level (5) and is flange-shaped and surrounded by a perforated plate (6) with grid-shaped holes (7) for gas passage, 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).and that the floor (10) of the treatment chamber (2) is inclined towards a drain opening (11) for the washing liquid located at the lowest point. Device for treating exhaust gases of a small combustion plant according to claim 1, characterized in that an S-shaped siphon (12) is arranged following the drain opening (1) for the washing liquid, the upper bend (13) of which defines the liquid level (5) in the treatment chamber (2). Device for treating exhaust gases of a small combustion plant according to claim 2, 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). Device for treating exhaust gases of a small combustion plant according to one of claims 1 to 3, characterized in that a liquid supply line is provided in a vertical direction above and / or below the perforated plate (6) and is laterally connected to the treatment chamber (2) via a shut-off valve. Device for treating exhaust gases of a small combustion plant according to one of claims 1 to 4, characterized in that flow elements 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, wherein a layer of steel wool is preferably provided as the flow element. Device for treating exhaust gases of a small combustion plant according to one of claims 1 to 5, characterized in that the small combustion plant is a combustion furnace for biomass, in particular wood pellets, wherein the plant comprises a fluidized bed and is thus operated under overpressure. Device for treating exhaust gases of a small combustion plant according to one of claims 1 to 6, characterized in that the heat transferred from 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 thus supplied to the heating and / or hot water preparation.

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