Chimney system and use of an exhaust gas aftertreatment unit

Abstract

The invention relates to a chimney system (1) comprising a chimney furnace (2) to which a furnace pipe (5) is connected for discharging exhaust gases (8) from the chimney furnace (2), wherein an exhaust gas aftertreatment unit (9) is provided in the furnace pipe (5), and at least two axial zones (10, 11) are mounted in the exhaust gas aftertreatment unit (9), a first zone (10) having a catalytic function and a second zone (11) having a filtering function. Each of the at least two zones (10, 11) comprises a plurality of channels (16) with a channel density of at most 600 cpsi [cells per square inch].

Description

[0001] Chimney system and use of an exhaust gas aftertreatment unit

[0002] The invention relates to a chimney system and a use of an exhaust gas aftertreatment unit.

[0003] For environmental protection reasons, chimney systems are now occasionally subjected to exhaust gas aftertreatment. For this purpose, exhaust gas cleaning units can be installed in a stove pipe in the immediate vicinity of an outlet from a combustion chamber of a fireplace stove in the chimney system to the stove pipe. Nitrogen oxides, carbon monoxide and / or hydrocarbons, for example, are catalytically converted from the exhaust gases and / or soot is filtered out. Soot is filtered out using passive filters. However, this requires regular filter cleaning. This requires that the filter be removed and cleaned at set intervals. This means a lot of effort for the user and a burden, particularly due to ash.

[0004] Unfortunately, conventional chimney exhaust systems have relatively low soot removal rates and / or high acquisition costs. Furthermore, continuous manual soot cleaning is (additionally) necessary.

[0005] Based on this, the object of the invention is to at least partially solve the problems described with reference to the prior art. In particular, it is intended to create a method for filtering soot from the exhaust gases of a chimney system and implementing it without active cleaning or other measures required by the user, in particular installation or removal at specified intervals for cleaning. Furthermore, it is intended to enable cost-effective production and reduced maintenance.

[0006] This object is achieved by the features of the independent claims. Further advantageous embodiments of the invention are specified in the dependent claims. It should be noted that features listed individually in the claims can be combined with one another in any technologically expedient manner and define further embodiments of the invention. Furthermore, the features listed in the claims are further specified and explained in the description, with further preferred embodiments of the inventions being presented.

[0007] A chimney system helps solve this problem. It includes a stove to which a flue pipe is connected for discharging exhaust gases from the stove. The flue pipe contains (at least) one exhaust aftertreatment unit with at least two axial zones. The first zone has a catalytic function, and the second zone a filtering function. Each zone is designed with a plurality of channels with a maximum channel density of 600 cpsi [cells per square inch].

[0008] A fireplace system can be a system for heating a (room of a) building, in particular for heating a residential building or a commercial building, especially an office building, a garage, workshop, hall, etc. It is also possible for a fireplace system to be used for central heating of several buildings, where the buildings are, in particular, part of a contiguous property, a courtyard, and / or a building complex. The fireplace system can (primarily or only) serve a decorative purpose, for example, for the appearance or well-being of people in a room of a building.

[0009] The fireplace system may include a (single) wood-burning stove. A wood-burning stove may be a stove designed for burning wood or other organic materials, such as wood pellets, paper, etc. Specifically, a wood-burning stove is a stove that is freestanding, suspended, and / or attached to a wall in a room / building. Fuel can be added to the stove (by hand) via a door or hatch to the combustion chamber.

[0010] The stovepipe connected to the fireplace can be designed as an exhaust pipe that is (partially) embedded in a wall of a building in which the fireplace is located, (partially) runs in / on the stove, (partially) protrudes from the fireplace, and (partially) runs freely in the room / building. In particular, the stovepipe is a pipe that is connected to the fireplace and leads through a building wall to the outside, where it is connected to an external chimney. The stovepipe can be equipped with a stovepipe heat exchanger that allows waste heat from exhaust gases to be used to further heat the building. The exhaust gases can pass through the stovepipe into the external chimney and from there be discharged to the surrounding area of ​​the building via an opening.

[0011] An exhaust gas treatment unit is located in the stovepipe, through which the exhaust gases from the stove can flow. The exhaust gas treatment unit spans a cross-sectional area of ​​the stovepipe, allowing all exhaust gases from the stove to pass through the exhaust gas treatment unit before being directed into the outdoor chimney or the surrounding area.

[0012] The at least two axial zones mounted in the exhaust gas aftertreatment unit are preferably part of the exhaust gas aftertreatment unit and completely span a cross-sectional area of ​​the stove pipe. This allows all exhaust gases from the fireplace stove to pass through the two axial zones before being directed into the external chimney. The term “axial zone” is intended to express that the zone should not comprise a two-dimensional area, such as the cross-sectional area of ​​the stove pipe, but should also extend in the direction of the stove pipe’s axis. In other words, this can mean that the functional surfaces of the zones extend along this axis, i.e. exhaust gas can flow along and / or through these axially extending functional surfaces. The zone can be designed as a three-dimensional, possibly regularly shaped, (partial) body.

[0013] The first and second zones can be arranged directly adjacent to one another in the axial direction, i.e., in particular, with an axial distance of less than 10 mm [millimeters] from one another. It can also be provided that these zones are present without any distance and / or gap between them. Both zones together have a length in the axial direction or in the flow direction of at least 50 millimeters [mm], preferably at least 100 mm. The cross-section of the furnace tube or the zones is preferably in the range of 7,500 to 35,000 mm 2 [square millimeters], particularly in the range from 11,000 to 32,000 mm 2 .

[0014] The first axial zone can have a catalytic function. The catalytic function is, in particular, an oxidation function, namely the oxidation of nitrogen monoxide to nitrogen dioxide. A catalyst can be provided in / on an (inert) support material, for example, embedded in a coating, so-called washcoat (porous aluminum oxide). The (oxidation) catalyst is, in particular, at least one selected from the following group: platinum, palladium, rhodium. The amount of catalyst per liter [1] of the volume of the first zone can be in the range of 0.35 to 3.53 grams [g]. This corresponds approximately to a loading of 10 to 60 grams per cubic foot [g / ft 3 ]. A precious metal quantity in the range of 1.3 g / l (or 36.8 g / ft 3 ) to 1.5 g / l (or 42.5 g / ft 3 ).

[0015] The second axial zone has a filtering function, in particular filtering out soot from the exhaust gas. A filter wall can be provided here, i.e., a wall through which the exhaust gas flows (forcedly) or even through. The filter wall can be provided with a porous or fibrous coating and / or wall structure. Metallic fibers are preferably considered for a filter wall. Such (at least partially metallic) fiber fleeces can also be used in combination with metal foils (comprising, for example, a corrugated structure configured with guide vanes and / or perforations). This combination is preferably realized by welding the fiber layer to at least one section of a metal foil. It is therefore possible for the channels formed in the second axial zone to be partially bounded by a metal foil and partially by a fiber layer / filter wall.Each of the zones can be designed with a plurality of channels through which the exhaust gas flows. The channels can redirect, retain, dam, and / or allow the exhaust gas to pass unhindered. The channels can run parallel along a center axis of the exhaust aftertreatment unit or parallel to one another, so that the exhaust gas is directed along the center axis. The channels can branch off to other channels. The channels can be partially closed (in the second zone) or closed at one end, so that exhaust gases are dammed within them or directed through the adjacent filter walls.

[0016] The channel density (especially for straight or axial channels) is a maximum of 400 cpsi, and is particularly in the range of 100 to 300 cpsi (conversion: 1 square inch corresponds to approximately 6.4516 square centimeters).

[0017] If the zone comprises a honeycomb body with adjacent sheet layers, each having a corrugation, with the corrugations arranged at an acute angle to each other, the channel density can be somewhat higher, e.g. a maximum of 600 cpsi or in the range of 150 to 400 cpsi.

[0018] Combustion in a stack system can be characterized by highly variable flue gas compositions, temperature fields, and / or flow velocities over time and location. Furthermore, combustion is also strongly influenced by the suction of the stack system, making overall combustion particularly vulnerable or incomplete, and thus even more pollutant-laden, if the flow resistance of the exhaust gas treatment unit with its two zones is too high, especially above 400 cpsi. A particularly important factor here is the sometimes relatively long / large particles produced during stack combustion, which are also easily degraded due to the specified (large) duct cross-section.

[0019] It is preferred that the cell density of the second axial zone be greater than the cell density of the first axial zone. The cell density in the second axial zone can be at least 30%, possibly even at least 50%, greater. The second axial zone has a predetermined or pronounced filtering and / or retention capacity to retain carbon particles (for a sufficient time) so that chemical reduction with the NO2 can occur or has occurred, because it is possible that both reactants are present locally at different times.

[0020] With a fireplace system, it is particularly important to maintain the correct backpressure in the flue pipe. If the backpressure is undesirably high, there is a risk that flue gases can back up into the combustion chamber and from there flow back into the interior of a building, for example, when new wood is added. The suction effect of the outdoor chimney must therefore be maintained.

[0021] The first axial zone and / or the second axial zone can be realized with one honeycomb body or with two honeycomb bodies. The honeycomb body is a regular body through which a plurality of (straight) channels extend along the axis. If several honeycomb bodies are provided, these can be provided in a common casing and / or connected to one another by material technology. It is possible for a single honeycomb body to form both zones, with some channel walls extending across both zones and some being provided in only one zone and / or with channel walls being composed together in the axial direction, for example with different materials or material shapes. The honeycomb body can have various shapes, in particular it can have or span a round, oval, polygonal or similar cross-section.During operation, the exhaust gas regularly enters via a first end face and exits again via a second end face. The end faces, which are preferably arranged substantially parallel to one another, regularly define the length of the honeycomb body in the direction of the (axial) central axis, which penetrates both end faces and is arranged perpendicularly and centrally to at least one, preferably both end faces. The honeycomb body preferably has at least one at least partially structured metallic layer (e.g., a metal foil, a metal sheet, etc.). It is possible for a (single) metallic layer to have smooth and structured sections or sections with different structures. This at least one metallic layer can, for example, be arranged in a meandering, S-shaped, or spiral manner around the central axis. It is possible for several metallic layers to be used, for examplesome of the layers are smooth and / or structured differently than at least one other metallic layer.

[0022] In particular, two metallic layers or a multiple thereof are used, with one pair of layers having the same structure (type, size, etc.) but with a different orientation relative to the axis, so that they intersect. It is possible for the honeycomb body to have only structured and no unstructured (smooth) metallic layers (metal foils).

[0023] At least one or a predetermined number of the metallic layers may also comprise slots, (hole) openings, or the like, in order to enable exhaust gas exchange through the layer itself or between adjacent channels.

[0024] At least one or a predetermined number of the metallic layers may have a secondary structure or microstructure (e.g. knobs, projections, wings, tabs) which (partially) protrude into the channels and thus provide inflow surfaces which result in a type of deflection and / or swirling of the partial exhaust gas flows in the interior of such a channel.

[0025] This can lead to intensive mixing of the partial exhaust gas streams themselves, ensuring intimate contact of the pollutants contained in the exhaust gas with the duct wall, which is particularly advantageous given the slow flow of chimney exhaust gases and the avoidable risk of exhaust backflow. In the second zone, the honeycomb body or the duct walls formed with it can be constructed with a metallic fleece. A "fleece" refers in particular to a flat structure, whereby the wire filaments (fibers) forming the fleece can be arranged in an orderly or random manner. Examples of fleeces include woven fabrics, grid structures, knitted fabrics, random layers, etc. The fleece can also comprise at least one additive, such as other types of fleeces, powders, or the like, which are ultimately permanently bonded to the fleece.The metallic wire filaments comprise in particular a material which essentially comprises steel as the base material, wherein preferably high proportions of chromium (e.g. in a range from 18 wt.% to 21 wt.%) and / or aluminum (e.g. at least.

[0026] 4.5 wt.%, in particular at least 5.5 wt.%) are intended. In principle, aluminized wire filaments can also be used.

[0027] It is possible for the second zone to comprise several honeycomb bodies spaced apart by axial gaps, so that the exhaust gas repeatedly exits a honeycomb body, (partially) mixes in the gap, and then impacts or enters another end face of the honeycomb body. These end faces can represent exposed positions for soot deposition and decomposition.

[0028] The two zones are preferably formed with at least one metallic honeycomb body and at least partially have a catalytic coating. If both zones are provided with a coating, the catalytic functions in each zone are different from each other. The coating can comprise a washcoat applied to the metallic layers or a portion thereof. The second zone can be uncoated.

[0029] The at least two zones can be axially spaced apart from one another in the exhaust gas aftertreatment unit along a central axis. The distance is preferably a maximum of 10 mm, in particular a maximum of 5 mm [millimeters]. The zones are arranged in particular such that the exhaust gases can pass through the axial zones one after the other, and a (non-catalytically active) mixing zone is provided between them for the exhaust gas exiting the first axial zone.

[0030] Preferably, the first zone is an oxidation zone in which NO X (Nitrogen oxide) from the exhaust gases are oxidized to NO2 (nitrogen dioxide), CO (carbon monoxide) to CO2 (nitrogen dioxide) and HC (hydrocarbon) to water (H2O).

[0031] The second zone preferably has an area with a filtering function in which soot can be separated and (temporarily) stored and reacted with the nitrogen dioxide produced. The second zone also has an area assigned to the filtering area with a regenerating function with which the soot particles can be regenerated in the exhaust gas aftertreatment unit. The second zone is preferably regenerable, wherein in the case of soot separation, the regeneration takes place by oxidation of the soot either by NO2 at a temperature above approximately 200°C [degrees Celsius] or with air or O2 (oxygen) thermally at, for example, temperatures above 500°C. The second axial zone can have an increased filtering or holding function. This allows soot particles to be held and a chemical reaction with NO2 is possible. This can ensure that both components are present in the second zone simultaneously.

[0032] In particular, the second zone is arranged in a section along the center axis of the exhaust pipe in which temperatures between 200 °C and 400 °C are regularly expected.

[0033] The stovepipe can be clamped and / or soldered into a combustion chamber of the chimney system. The stovepipe preferably represents the sole exit for the exhaust gases from the combustion chamber. The stovepipe, the external chimney, and the combustion chamber are preferably designed so that, in the event of a fire in the combustion chamber, the exhaust gases flow to the opening of the external chimney. Preferably, no active measures are required for this; rather, the natural suction of the external chimney sufficiently supports the exhaust gas flow. However, it is possible for an airflow and / or a fan to drive / pull the exhaust gases through the exhaust gas aftertreatment unit.

[0034] Preferably, a transition from the combustion chamber to the stove pipe is sealed. The stove pipe can be clamped into an outlet of the combustion chamber with a press fit. Additionally, the stove pipe is soldered at the press fit into a transition to the combustion chamber outside and / or inside the interior, in particular so that the transition to the combustion chamber is sealed and no exhaust gas can escape along such a soldered joint.

[0035] The stove pipe can have a bypass (which can be specifically adjusted and opened and closed if necessary). The bypass allows exhaust gases to bypass the exhaust gas aftertreatment unit. It is possible for all exhaust gases to be directed through the bypass, or for only a portion of the exhaust gases to reach it and the remainder to be directed through the exhaust gas aftertreatment unit. The bypass can be set up so that exhaust gases bypass both zones of the exhaust gas aftertreatment unit. It is also possible for the bypass to be set up so that the exhaust gases bypass only one of the two zones. Advantageously, the bypass is set up so that exhaust gases are at least partially directed into the bypass before entering the first zone and are fed back into the exhaust gas aftertreatment unit between exiting the first zone and entering the second zone.

[0036] A bypass, in which exhaust gases are diverted around the first zone, can be adjusted in such a way that a desired ratio of NO2 to soot content is present upstream of the second zone and the CRT effect can be fully utilized. In this way, soot regeneration in the second zone can be particularly advantageous. Especially when starting up the chimney system, the exhaust gas temperatures may not yet be high enough, making it necessary to regulate the ratio via the bypass. The flow of exhaust gas through the bypass can be induced actively or passively. Active measures include, in particular, flaps or bulkheads in the bypass, which are electronically controlled and / or can be opened or closed based on measured data in the exhaust gas and / or in the combustion chamber (e.g. exhaust gas temperature, combustion chamber temperature, flame temperature, etc.).Passive measures include, in particular, flaps or bulkheads to an inlet into the bypass, which can be opened or closed, for example, by means that expand or contract at different temperatures.

[0037] The fireplace system can be configured to achieve or be designed to achieve a (maximum) total output between 10 kW [kilowatts] and 120 kW. Particularly preferably, the fireplace system does not exceed a total output of 100 kW. The fireplace system is particularly designed for use in a building. To achieve a temperature typical for buildings, the fireplace system is preferably dimensioned so that the total output is not too high and an average amount of fuel is used to achieve this temperature.

[0038] A wood-burning stove can be a furnace or a wood gasification boiler. A wood-burning stove can be a wood-fired oven that heats a building, particularly as a central heat source. Such a stove can be located in a living room, a basement, and / or outside the building. A wood gasification boiler can be a wood-burning stove that uses logs as fuel. In contrast to a wood-burning stove, in which the wood burns completely, a wood gasification boiler preferably creates a bottom burn. Combustion air is preferably directed over the underside of the wood, so that the wood outgasses into a lower chamber and burns there. A wood gasification boiler can heat one or more buildings, particularly as a central heat source. The wood gasification boiler can be located in a building or next to a building.A furnace system or a wood gasification boiler located outside a building is preferably equipped so that the furnace pipe is the external chimney. In particular, the exhaust gas aftertreatment unit is then arranged in a part near an outlet from the combustion chamber into the furnace pipe or the external chimney. The use of an exhaust gas aftertreatment unit with at least two axial zones further contributes to the solution of the problem. A first zone has a catalytic function and a second zone a filtering function, and each of the at least two zones is designed with a plurality of channels. The exhaust gas aftertreatment unit serves to oxidize NOx and remove soot from a chimney system of a domestic combustion.

[0039] In particular, its use provides advantages or alleviates the problems mentioned above. The specific advantages and design features described for the chimney system are applicable and transferable to the described use of the exhaust gas aftertreatment unit, and vice versa.

[0040] In summary, a coordinated system for the chimney system is proposed here, whereby additional NOx reduction can be achieved as part of a self-cleaning process. The particularly low backpressure can be achieved with the low cell densities, for example, by eliminating smooth layers in the honeycomb structure. The CRT effect achieves continuous soot particle and NOx reduction, thus avoiding manual cleaning and preventing maintenance backlogs and incorrect operation. Furthermore, the system proposed here achieves consistently high separation rates.

[0041] The invention and the technical environment are explained in more detail below with the aid of figures. The representations are schematic and not intended to illustrate proportions. The explanations given with reference to individual details of the figures are extractable and can be freely combined with facts from the above description, unless something else necessarily follows for a person skilled in the art or such a combination is explicitly excluded. It shows schematically:

[0042] Fig. 1: schematic representation of the exhaust gas aftertreatment unit, and Fig. 2: representation of a schematic structure of a chimney system.

[0043] Fig. 1 shows a schematic representation of the exhaust gas aftertreatment unit 9. The exhaust gas aftertreatment unit 9 is arranged in a furnace tube 5. The exhaust gas aftertreatment unit 9 has a first zone 10 and a second zone 11. The zones 10, 11 are axially spaced from one another along a center axis 13. The first zone 10 is an oxidation zone in which CO (carbon monoxide), NOx (nitrogen oxides) and HC (hydrocarbons) are oxidized from exhaust gases 8 to CO2 (carbon dioxide), NO2 (nitrogen dioxide) and H2O (water). The second zone 11 is a filtering and regeneration zone. In the second zone 11, soot is filtered out of the exhaust gases 8 and separated. Both zones 10 and 11 are provided with a honeycomb body which has a plurality of channels 16. The exhaust gases 8 are then regenerated by oxidising the soot either by NO2 at a temperature above about 200°C [degrees Celsius] or with air or O2 (oxygen) thermally at e.g.Temperatures above 500° C.

[0044] Fig. 2 shows a schematic diagram of a chimney system 1. The chimney system 1 comprises a fireplace stove 2, which is arranged in an interior space 3 of a building 4. Connected to the fireplace stove 2 with its combustion chamber 14 is a chimney pipe 5, in which the exhaust gas aftertreatment unit 9 with two zones 10, 11 is arranged. The chimney pipe 5 also has a bypass 15, via which the exhaust gases 8 can be guided past the first zone 10 and, before the second zone 11, back into the chimney pipe 5 and thus into the exhaust gas aftertreatment unit 9. The exhaust gas aftertreatment unit 9 is arranged in the chimney pipe 5 along the central axis 13. After flowing through the exhaust gas aftertreatment unit 9, the exhaust gases 8 reach an external chimney 6 via the chimney pipe 5, through which the exhaust gases 8 are guided to an opening 7, where they can flow out into the environment 12. Reference numeral

[0045] 1 chimney system

[0046] 2 fireplaces

[0047] 3 Interior

[0048] 4 buildings

[0049] 5 Stovepipe

[0050] 6 outdoor fireplace

[0051] 7 Opening

[0052] 8 Exhaust

[0053] 9 Exhaust aftertreatment unit

[0054] 10 first zone

[0055] 11 second zone

[0056] 12 Surroundings

[0057] 13 Center axis

[0058] 14 Combustion chamber

[0059] 15 Bypass

[0060] 16 channels

Claims

Claims 1. Chimney system (1), comprising a fireplace (2) to which a stove pipe (5) for discharging exhaust gases (8) from the fireplace (2) is connected, wherein an exhaust gas aftertreatment unit (9) is arranged in the stove pipe (5), wherein at least two axial zones (10, 11) are mounted in the exhaust gas aftertreatment unit (9), wherein a first zone (10) has a catalytic function and a second zone (11) has a filtering function and each of the at least two zones (10, 11) is designed with a plurality of channels (16) with a channel density of maximum 600 cpsi.

2. Chimney system (1) according to the preceding claim, wherein the at least two zones (10, 11) are realized with one or two metallic honeycomb bodies.

3. Chimney system (1) according to one of the preceding claims, wherein the metallic honeycomb bodies of the at least two zones (10, 11) are partially provided with a catalytic coating.

4. Chimney system (1) according to one of the preceding claims, wherein the at least two zones (10, 11) are axially spaced from one another in the exhaust gas aftertreatment unit (9) along a central axis (13).

5. Chimney system (1) according to one of the preceding claims, wherein the first zone (10) is an oxidation zone in which NOx from the exhaust gases are oxidized to NO2 and CO to CO2.

6. Chimney system (1) according to one of the preceding claims, wherein the second zone (11) has a regenerating function with which the soot particles in the exhaust gas aftertreatment unit (9) can be regenerated.

7. Chimney system (1) according to one of the preceding claims, wherein the stove pipe (5) is clamped and / or soldered into a combustion chamber (14) of the chimney system (1).

8. Chimney system (1) according to one of the preceding claims, wherein the stove pipe (5) has a bypass (15), wherein exhaust gases can be guided past the exhaust gas aftertreatment unit (9) through the bypass (15).

9. Chimney system (1) according to one of the preceding claims, wherein the chimney system (1) does not exceed a total output of 100 kW [kilowatts].

10. Chimney system (1) according to one of the preceding claims, wherein the fireplace stove (2) is a furnace system or a wood gasification boiler.

11. Use of an exhaust gas aftertreatment unit (9) with at least two axial zones (10, 11), wherein a first zone (10) has a catalytic function and a second zone (11) has a filtering function and each of the at least two zones (10, 11) is designed with a plurality of channels (16), wherein the exhaust gas aftertreatment unit (9) is designed for the oxidation of NOx and soot removal from a chimney system (1) of a domestic combustion.

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