EXHAUST AFTERTREATMENT UNIT

Description

[0001] The invention relates to an exhaust gas aftertreatment device for a combustion appliance, comprising at least one flow path which extends from a first end of the exhaust gas aftertreatment device to a second end of the exhaust gas aftertreatment device in the form of a helical path. Such exhaust gas aftertreatment systems are known, for example, from US 5,633,066 A1.

[0002] From the subsequently published German patent application DE 10 2019 218 807 A1, an exhaust gas aftertreatment device is known which is composed of a plurality of disc-shaped elements. Each disc-shaped element has an opening. If a disc-shaped element is arranged rotated relative to the adjacent disc-shaped element by a predefinable angle, a helical flow path is created. During the flow, pollutants in the exhaust gas can be post-oxidized and / or fine dust particles can be separated.

[0003] However, it has been shown that this known exhaust aftertreatment device cannot ensure efficient pollutant reduction in all embodiments. Furthermore, the construction from individual disc-shaped elements can be complex. Based on the prior art, the invention therefore aims to provide an exhaust aftertreatment device with improved cleaning performance. In some embodiments, the invention also aims to simplify the construction of an exhaust aftertreatment device.

[0004] The problem is solved according to the invention by an exhaust aftertreatment device according to claim 1. Advantageous embodiments of the invention are found in the dependent claims.

[0005] According to the invention, an exhaust aftertreatment device is proposed which has at least one flow path. The flow path extends from a first end of the exhaust aftertreatment device to a second end of the exhaust aftertreatment device. The exhaust gas can thus enter the exhaust aftertreatment device at the first end, follow the flow path, and exit the exhaust aftertreatment device at the second end. Within the exhaust aftertreatment device, gaseous pollutants and / or particulate matter can be rendered harmless. For example, nitrogen oxides can be reduced. Carbon monoxide and / or hydrocarbons and / or particulate matter can be oxidized.

[0006] According to the invention, it is proposed that the flow path within the exhaust aftertreatment device runs, at least section by section, in the form of a helix. For the purposes of the present invention, a helix is ​​defined as a curve that winds around the surface of a cylinder with a predefinable pitch. The pitch can be constant or variable along its longitudinal extent. The distance by which the helix winds upwards in the direction of the cylinder axis during one complete revolution is referred to in the following description as the pitch. h denoted. The quotient of gear height h and extent is subsequently referred to as gradient. k denoted, i.e. k = h 2 πr According to the invention, it is proposed that the helix of the flow path has a slope k possesses a slope greater than 0.35. In other embodiments of the invention, the slope is kgreater than approximately 0.6. In other embodiments of the invention, the slope is k greater than approximately 0.8. In other embodiments of the invention, the slope is k greater than approximately 1.0. Finally, the slope can k In some embodiments, the value may be greater than approximately 1.2. This feature has the effect of allowing thorough mixing of the exhaust gas to be treated with an oxidizing and / or reducing agent, extending the residence time, and enabling the separation of fine dust particles by means of a cyclone effect. This allows the exhaust gas aftertreatment device according to the invention to ensure efficient exhaust gas purification.

[0007] The exhaust gas aftertreatment device according to the invention is used in combustion appliances, such as boilers or individual room heating systems, such as tiled stoves or fireplaces. In other embodiments of the invention, the exhaust gas aftertreatment device can also be used for industrial furnaces, thermal waste treatment plants, crematoria, or other facilities that generate hot exhaust gases.

[0008] In some embodiments of the invention, the helix of the flow path can have a slope. k exhibiting a slope less than approximately 1.0. In some embodiments of the invention, the helix can have a gradient. k exhibiting a slope of less than approximately 1.2. In other embodiments of the invention, the helix can have a gradient. k exhibiting a slope that is less than approximately 1.6. In other embodiments of the invention, the slope can be kThe helix angle should be less than approximately 2.0. According to the invention, the pitch is... k the helix angle is less than 2.5.

[0009] The slope k It can therefore be selected from the following ranges: 0.35 ≤ k ≤ 1.0 or 0.35 ≤ k ≤ 1.2 or 0.35 ≤ k ≤ 1.6 or 0.35 ≤ k ≤ 2.0 or 0.35 ≤ k ≤ 2.5 or 0.6 ≤ k ≤ 1.0 or 0.6 ≤ k ≤ 1.2 or 0.6 ≤ k ≤ 1.6 or 0.6 ≤ k ≤ 2.0 or 0.6 ≤ k ≤ 2.5 or 0.8 ≤ k ≤ 1.0 or 0.8 ≤ k ≤ 1.2 or 0.8 ≤ k ≤ 1.6 or 0.8 ≤ k ≤ 2.0 or 0.8 ≤ k ≤ 2.5 or 1.0 ≤ k ≤ 1.2 or 1.0 ≤ k ≤ 1.6 or 1.0 ≤ k ≤ 2.0 or 1.0 ≤ k ≤ 2.5 or 1.2 ≤ k ≤ 1.6 or 1.2 ≤ k ≤ 2.0 or 1.2 ≤ k≤ 2.5. The slope can be adjusted to the length of the exhaust aftertreatment system.

[0010] In some embodiments of the invention, the flow path can have a diameter of 20 cm to 150 cm. In other embodiments, the flow path can have a diameter of approximately 25 cm to approximately 80 cm. In yet other embodiments, the flow path can have a diameter of approximately 80 cm to approximately 120 cm. In still other embodiments, the flow path can have a diameter of approximately 20 cm to approximately 50 cm. The diameter, and thus the cross-section, of the flow path can be adapted to the volume of exhaust gas being produced, with the lower values ​​being used, for example, for individual room heating appliances and the larger values ​​for larger boilers, for example, for supplying a multi-family dwelling or an industrial plant.Adapting the diameter to the amount of exhaust gas ensures that the flow velocity remains within a predefinable range, which keeps the pressure loss of the exhaust gas in the exhaust aftertreatment system within a tolerable range and, on the other hand, enables a sufficiently turbulent flow that allows for good mixing of the exhaust gas with an oxidizing and / or reducing agent.

[0011] In some embodiments of the invention, the inner surface of the flow path can have a plurality of steps. In some embodiments of the invention, the steps can each have a height of 8 mm to 30 mm. In other embodiments of the invention, the steps can each have a height of approximately 15 mm to approximately 25 mm. The steps can be designed with sharp edges, so that flow separation occurs at the leading edges of the steps and the exhaust gas flowing in the exhaust aftertreatment system flows turbulently through the flow path. The additional turbulence introduced in this way enables efficient mixing of the exhaust gas with an oxidizing or reducing agent, thus potentially increasing the efficiency of the exhaust aftertreatment.

[0012] In some embodiments of the invention, the length of the flow path can be 0.5 to 5 times the pitch height h. In other embodiments of the invention, the length of the flow path can be approximately 0.9 to approximately 3 times the pitch height. h In other embodiments of the invention, the length of the flow path can be approximately 1 to approximately 2.5 times the pitch height. h Finally, in some embodiments of the invention, the length of the flow path can be approximately 0.9 to approximately 2 times the pitch height. h Such a designed exhaust aftertreatment system takes up little installation space and yet ensures that pollutants are removed from the exhaust gas with high efficiency.

[0013] In some embodiments of the invention, the cross-section, length and slope can be kThe flow path should be selected such that the pressure loss of an exhaust gas flowing through it is less than approximately 100 Pa. Such an exhaust gas aftertreatment system can, for example, efficiently clean the exhaust gases of a boiler or an industrial furnace equipped with a blower that circulates combustion air and exhaust gas through the boiler.

[0014] In some embodiments of the invention, the cross-section, length and slope can be k The flow path should be selected such that the pressure loss of an exhaust gas flowing through the flow path is less than approximately 50 Pa. The lower exhaust gas back pressure can increase the output and / or efficiency of a boiler equipped with the exhaust gas aftertreatment system.

[0015] According to the invention, the cross-section, length, and slope k of the flow path are selected such that the pressure loss of an exhaust gas flowing through the flow path is less than 10 Pa or less than approximately 3 Pa. In this case, the exhaust gas aftertreatment device is particularly well suited for individual room heating appliances whose exhaust gas flow is driven solely by the temperature difference between the embers and the chimney. Nevertheless, the low pressure loss ensures reliable flow through the exhaust gas aftertreatment device without causing exhaust gases to back up into the room where the individual room heating appliance is located.

[0016] In some embodiments of the invention, the cross-section of the flow path can comprise between 30% and 50% of the total cross-section of the exhaust aftertreatment device. In other embodiments of the invention, the cross-section of the flow path can comprise between approximately 35% and approximately 40% of the total cross-section of the exhaust aftertreatment device. A flow path cross-section designed in this way combines low pressure loss with high turbulence, thus ensuring reliable flow and sufficiently strong turbulence.

[0017] In some embodiments of the invention, the exhaust aftertreatment device can be manufactured as a casting. In some embodiments of the invention, the exhaust aftertreatment device can be manufactured by casting in a expendable mold.

[0018] In other embodiments of the invention, the exhaust aftertreatment device can be composed of several elements. For example, in some embodiments, the exhaust aftertreatment device can be composed of a plurality of disc-shaped elements, each forming a longitudinal section of the exhaust aftertreatment device and each having at least one recess. In other embodiments of the invention, the exhaust aftertreatment device can be composed of a plurality of elements, each forming a segment of the exhaust aftertreatment device.In some embodiments of the invention, an exhaust aftertreatment device composed of individual elements may require less manufacturing effort and / or be easier to transport and / or be manufactured modularly from identical parts in different sizes in order to adapt them flexibly to the respective application.

[0019] In some embodiments of the invention, the exhaust aftertreatment device can contain or consist of at least one inorganic, non-metallic material. Such a material can, on the one hand, have a high heat capacity and, on the other hand, exhibit high resistance to thermal or corrosive attack. In some embodiments of the invention, an inorganic, non-metallic material can contain or consist of at least one ceramic. In some embodiments of the invention, the exhaust aftertreatment device can be made of a material that contains or consists of at least one oxide ceramic, carbide, nitride, or oxynitride. In some embodiments of the invention, the exhaust aftertreatment device can contain or consist of at least silicon dioxide and / or aluminum oxide and / or magnesium oxide and / or calcium oxide and / or zirconium oxide and / or chromium oxide and / or silicon carbide.These materials are resistant to high temperatures, can exhibit catalytic properties in some embodiments of the invention, and are resistant to aggressive media that may be present in the exhaust gases or that may arise from the conversion of the exhaust gases in the exhaust aftertreatment device.

[0020] In some embodiments of the invention, the inside of the flow path can have an average roughness depth Rz of 10 µm to 3 µm. In other embodiments of the invention, the inside of the flow path can have an average roughness depth Rz of approximately 8 µm to approximately 4 µm. In still other embodiments of the invention, the inside of the flow path can have an average roughness depth Rz of approximately 6 µm to approximately 4.5 µm. For the purposes of this description, the average roughness depth Rz denotes the mean value of individual roughness depths from five consecutive individual measurement sections in the roughness profile. The extreme values ​​in each measurement section are added together, and the range is divided by the number of measurement sections.The roughness of the inside of the flow path can cause fine dust and soot particles to be deposited in the exhaust aftertreatment system and subsequently oxidized, so that they cannot leave the exhaust aftertreatment system in the form of unwanted particles.

[0021] The invention will now be explained in more detail using an exemplary embodiment without limiting the general concept of the invention. It will be shown that... Figure 1 shows an exhaust aftertreatment device according to the present invention in a view. Figure 2 shows the exhaust aftertreatment device according to Figure 1 along the section line AA. Figure 3 shows the exhaust aftertreatment system according to Figure 1 along the section line BB. Figure 4 shows the helical flow path according to the present invention in a partially cutaway, three-dimensional view.

[0022] Based on the Figures 1 to 4An exemplary embodiment of an exhaust gas aftertreatment device according to the invention is explained in more detail. The exhaust gas aftertreatment device 1 has at least one flow path 2, which runs in a helical shape from a first end 11 of the exhaust gas aftertreatment device 1 to a second end 12 of the exhaust gas aftertreatment device 1. When the exhaust gas aftertreatment device is in operation, exhaust gas is supplied to the flow path via the first end 11, for example from a boiler, an industrial furnace, or a room heating appliance. The exhaust gas flows through the flow path 2 and exits at the second end 12 of the exhaust gas aftertreatment device 1.

[0023] As from Figure 2 and Figure 4As can be seen, the flow path follows a helix, i.e., a curve that winds around the surface of a cylinder with a specific slope. In the illustrated embodiment, the slope is constant. In other embodiments of the invention, the slope can vary along the length of the helix.

[0024] The helix angle is determined by the pitch height h characterized, that is, the distance by which the flow path winds upwards during a full rotation, i.e., in the direction of the second end 12. Furthermore, the shape of the flow path is characterized by the slope. k characterized by the radius of the flow path and the pitch height k = h 2 πr This results in the following: According to the invention, the helix has a slope k which is greater than approximately 0.8 and less than approximately 1.2.

[0025] As shown in the cross-sections according to Figure 2 and Figure 3As can be seen, the inner surface 20 of the flow path 2 has a plurality of steps 25, each with a height of approximately 8 mm to approximately 30 mm or from approximately 15 mm to approximately 25 mm. The exhaust gas flowing in the flow path 2 thus experiences turbulent flow, which ensures that the exhaust gas mixes efficiently with an oxidizing and / or reducing agent, so that hydrocarbons, carbon monoxide, particulate matter, soot, or other pollutants are efficiently oxidized.

[0026] cross-section, length and slope k The flow path is chosen such that the pressure loss of an exhaust gas flowing through flow path 2 is less than approximately 10 Pa.

[0027] In the illustrated embodiment, the exhaust aftertreatment device is composed of a plurality of disks 3, each having a cloverleaf-shaped opening 35. By stacking the disks one above the other, each offset by a predetermined angle of rotation relative to the adjacent disk, the flow path 2 is formed in the desired shape. In some embodiments of the invention, the disk-shaped elements 3 can have a thickness of approximately 15 mm to approximately 25 mm and be rotated by an angle of between approximately 10° and approximately 30° relative to the adjacent disk-shaped elements 3. The angle of rotation can be larger the shorter the exhaust aftertreatment device 1 is overall, so that the pitch of the helix of the flow path lies within the aforementioned range.

[0028] The effectiveness of the exhaust gas aftertreatment device according to the invention will be explained in more detail below using a comparative example. In this example, a boiler with a thermal output of 85 kW is used, which is fired with wood chips and straw. The exhaust gases from the boiler are discharged via a conventional exhaust pipe and also fed to the exhaust gas aftertreatment device described above. In both cases, exhaust gas measurements are taken according to DIN 18895. The following improvements in the exhaust gas values ​​result when the exhaust gas aftertreatment device according to the invention is used: State of the art exhaust aftertreatment device according to the invention CO ≈ 120 ppm < 3 ppm CO2 < 12 % > 16% by volume O 2 ≈ 8 - 11 vol% < 3.8 vol% NO x 420 ppm 220 ppm CH x ≈ 100 ppm < 5 ppm

[0029] The preceding values ​​show that combustion can be significantly improved by the exhaust gas aftertreatment device according to the invention. The residual oxygen in the exhaust gas decreases and the CO₂ content increases, indicating complete combustion of the fuel. Likewise, the pollutant content of the exhaust gas decreases and reaches or falls below typical values ​​for a natural gas heating system.

[0030] Naturally, the invention is not limited to the embodiments shown. The foregoing description should therefore be regarded not as limiting, but as explanatory.

Claims

1. Exhaust gas aftertreatment device (1) for a fireplace, comprising at least one flow path (2) which extends from a first end (11) of the exhaust gas aftertreatment device (1) to a second end (12) of the exhaust gas aftertreatment device (1) in the form of a helical line, characterized in that the helical line has a pitch k which is greater than 0.35 or greater than approximately 0.6 or greater than approximately 0.8 or greater than approximately 1.0 or greater than approximately 1.2 and less than 2.5, and the cross-section, length and pitch k of the flow path (2) are selected in such a way that the pressure loss of an exhaust gas flowing through the flow path (2) is less than 10 Pa.

2. Exhaust gas aftertreatment device according to claim 1, characterized in that the helical line has a pitch k which is less than approximately 1.0 or less than approximately 1.2 or less than approximately 1.6 or less than approximately 2.0.

3. Exhaust gas aftertreatment device according to claim 1 or 2, characterized in that the flow path (2) has a diameter of 20 cm to 150 cm or of approximately 25 cm to approximately 80 cm or of approximately 80 cm to approximately 120 cm or of approximately 20 cm to approximately 50 cm.

4. Exhaust gas aftertreatment device according to any one of claims 1 to 3, characterized in that the inner side (20) of the flow path (2) has steps (25).

5. Exhaust gas aftertreatment device according to claim 4, characterized in that the steps (25) each have a height of 8 mm to 30 mm or of 15 mm to 25 mm.

6. Exhaust gas aftertreatment device according to any one of claims 1 to 5, characterized in that the length of the flow path (2) is 0.5 to 5 times or 0.9 to 3 times or 1 to 2.5 times or 0.9 to 2 times the pitch h.

7. Exhaust gas aftertreatment device according to any one of claims 1 to 6, characterized in that the pressure loss of an exhaust gas flowing through the flow path (2) is less than approximately 3 Pa.

8. Exhaust gas aftertreatment device according to any one of claims 1 to 7, characterized in that a cross-section of the flow path (2) is between 30% and 50% or between approximately 35% and approximately 45% of a total cross-section of the exhaust gas aftertreatment device (1).

9. Exhaust gas aftertreatment device according to any one of claims 1 to 8, characterized in that it is composed of a plurality of disk-shaped elements (3), each of which forms a longitudinal portion of the exhaust gas aftertreatment device (1) and each of which has at least one recess (35).

10. Exhaust gas aftertreatment device according to any one of claims 1 to 9, characterized in that it contains or consists of at least one inorganic, non-metallic material, or in that it contains or consists of at least one ceramic, or in that it contains or consists of at least one oxide ceramic or a carbide or a nitride or an oxynitride, or in that it contains or consists of at least silicon dioxide and / or aluminum oxide and / or magnesium oxide and / or calcium oxide and / or zirconium oxide and / or chromium oxide and / or silicon carbide.

11. Exhaust gas aftertreatment device according to any one of claims 1 to 10, characterized in that the inner side (20) of the flow path (2) has an average roughness depth Rz of 10 µm to 3 µm or of approximately 8 µm to approximately 4 µm or of approximately 6 µm to approximately 4.5 µm.

12. Fireplace comprising an exhaust gas aftertreatment device according to any one of claims 1 to 11.