OVEN FOR BUILDING HEATING

Description

[0001] The present invention relates to a furnace for building heating, comprising a combustion chamber, an exhaust gas outlet, and a catalyst element. An exhaust gas duct connects the combustion chamber to the exhaust gas outlet.

[0002] When fossil or biogenic fuels, such as wood-based fuels, are burned in a furnace, for example for heating purposes, pollutants such as carbon monoxide and particulate matter are produced in the combustion gases. Catalysts, which are placed, for example, at the furnace's outlet, can be used to reduce these pollutants.

[0003] The combustion gases can reach temperatures exceeding 500 °C, but the effectiveness of known catalysts is limited at such temperatures. Therefore, the reduction in pollutants, particularly carbon monoxide, is relatively low.

[0004] Document WO 2013 / 159782 A1 describes a solid fuel stove with a catalyst unit comprising two insulating elements between which a catalyst element is arranged. Exhaust gases from a combustion chamber are guided through a curved edge to the catalyst element, which is located between the combustion chamber and a flue.

[0005] Document US 4,582,044 A describes a retrofit device that can be attached externally to a wood-burning stove. The retrofit device contains a heat exchanger that forms two passages. A catalytic igniter is located in the lower part of the retrofit device. The retrofit device can be attached to the wood-burning stove using a mounting bracket, allowing exhaust gases from the stove to enter the retrofit device and flow downwards through the first passage. They then flow through the catalytic igniter into the second passage. As the exhaust gases pass through the catalytic igniter, they are ignited and combust in a secondary combustion chamber.

[0006] It is therefore an object of the present invention to provide an improved concept for a furnace for building heating, which can reduce pollutant emissions.

[0007] According to the invention, this problem is solved by an oven according to the independent claim. Advantageous further developments and embodiments are the subject of the dependent claims.

[0008] The improved concept is based on the idea of ​​arranging a catalyst element in an exhaust gas channel inside the furnace, so that an inlet opening of the exhaust gas channel is located higher than the catalyst element.

[0009] According to the improved design, a furnace for building heating is specified, comprising a combustion chamber, an exhaust outlet, and a catalyst element. The furnace also features an exhaust duct connecting the combustion chamber to the exhaust outlet. The catalyst element is located within the exhaust duct, and an inlet opening of the exhaust duct is positioned higher than the catalyst element with respect to a vertical axis of the furnace. The inlet opening has a minimum dimension of less than 5 cm.

[0010] The oven can be designed, for example, to warm, heat or heat a building or one or more rooms of the building.

[0011] The exhaust outlet includes, in particular, an opening in the casing of the oven, through which combustion gases and smoke from the oven can be released, for example, into a chimney or a chimney pipe.

[0012] In this and the following, exhaust gases can be understood to mean combustion gases, i.e., gases produced during combustion, as well as mixtures of combustion gases with solid combustion residues, such as soot particles or other dust or fine dust particles, and / or with ambient air.

[0013] By connecting the combustion chamber to the exhaust outlet, the exhaust duct provides a path for the exhaust gas from the combustion chamber to the exhaust outlet, thus enabling a directed exhaust gas flow.

[0014] The fact that the catalyst element is located in the exhaust channel can be understood to mean that the exhaust gas, which flows from the combustion chamber through the exhaust channel to the exhaust outlet, must flow through the catalyst element.

[0015] The inlet opening is, in particular, an end of the exhaust duct facing the combustion chamber, for the entry of the exhaust gas into the exhaust duct.

[0016] The vertical axis refers in particular to a vertical spatial direction when the oven is aligned according to its intended use.

[0017] The furnace, particularly the combustion chamber, may have a base, such as a base plate or a base element. The vertical axis then corresponds to an axis that is perpendicular to the base plate or a flat part of the base element. The vertical axis points, for example, away from the base in the direction of the inlet opening and / or the exhaust outlet.

[0018] The floor, or floor plate or floor element, is in particular a surface or area intended for placing the fuel.

[0019] Alternatively, the vertical axis can also be interpreted as a direction parallel to gravity, i.e., the direction along which the exhaust gases would flow without any external disturbance. In this case, the vertical axis points specifically in the direction of decreasing gravity.

[0020] The fact that the inlet opening is positioned higher than the catalyst element can be understood, for example, to mean that the inlet opening has a higher position than the catalyst element with respect to the vertical axis.

[0021] In other words, a vertical distance between the ground and the inlet is greater than a vertical distance between the ground and the catalyst element.

[0022] Here and in the following, the term "distance" can be understood as a minimum distance. A vertical distance can be understood as a distance in the direction of the vertical axis.

[0023] In particular, in the vertical direction, i.e. in the direction parallel to the vertical axis, an upper edge of the catalyst element is located further from the ground than a lower edge of the inlet opening.

[0024] By connecting the combustion chamber, which is located inside the oven, and the exhaust outlet, the exhaust duct is located entirely inside the oven or within a housing of the oven.

[0025] The described arrangement of the inlet opening relative to the catalyst element results in exhaust gases rising from the combustion chamber, particularly from the immediate vicinity of the base, which enter the exhaust duct through the inlet opening, being deflected and, in a sense, reversed. This causes the exhaust gases to flow from the inlet opening back towards the base and thus towards the catalyst element. The exhaust gases are therefore forced onto a detour by the exhaust duct and the described arrangement of the inlet opening and catalyst element, allowing them to cool significantly on their way from their point of origin to the catalyst element.By cooling the exhaust gases and thus reducing their temperature as they flow through the catalyst element, the effectiveness of the catalytic reaction for pollutant reduction using the catalyst element, in particular for reducing the carbon monoxide content of the exhaust gases, is increased.

[0026] For example, exhaust gases can have a temperature well over 500 °C when they are generated, reaching 800 °C or more when burning wood or wood-based fuels. Guiding the exhaust gases through the flue in the described manner can then lead to a cooling of several hundred degrees Celsius before they flow through the catalyst. Consequently, the exhaust gases can then have temperatures at which the effectiveness of the catalytic reaction in the catalyst element is significantly increased. This can be the case, for example, at exhaust gas temperatures in the range of 170 to 250 °C. Test measurements on a furnace using the improved design have shown that exhaust gas temperatures of 200 to 250 °C can be achieved at the catalyst element using the described arrangement.

[0027] This significantly reduces the pollutant content in the exhaust gases, especially the carbon monoxide content.

[0028] The catalyst element can also contribute to the reduction of particle concentrations in the exhaust gases, for example soot or fine dust particles.

[0029] Test measurements have shown that, with stoves using the improved design, a carbon monoxide concentration of less than 400 mg / m³ and a particulate matter concentration of approximately 10–12 mg / m³ can be achieved in the exhaust gases when burning wood. This means that current limit values ​​in force in Europe, for example in Germany or Austria, are significantly lower, particularly for carbon monoxide concentration.

[0030] By redirecting the hot exhaust gases for cooling within the furnace, the thermal energy extracted from the exhaust gases can advantageously be used as usable heat. Components forming the exhaust duct, such as furnace casing parts or other structural elements, are heated by the flowing exhaust gas and in turn release the corresponding heat into the furnace's surroundings.

[0031] Test setups of ovens based on the improved concept have also shown that, with the design described, active ventilation devices, such as fans, are not required to draw exhaust gases from the combustion chamber through the flue and out of the oven. The natural draft due to the chimney effect is sufficient.

[0032] According to at least one embodiment of the furnace, the exhaust gas channel has a first part that is arranged between the catalyst element and the inlet opening, and a second part that is arranged between the catalyst element and the exhaust gas outlet.

[0033] According to at least one embodiment, the catalyst element is designed as a catalyst for carbon monoxide reduction.

[0034] According to at least one embodiment, the stove is designed as a fireplace or insert fireplace or as a fireplace insert.

[0035] According to at least one embodiment, the inlet opening is arranged on a top side, at an upper end, in an upper third or in an upper quarter of the combustion chamber.

[0036] According to at least one embodiment, the oven has a housing and the exhaust duct is formed at least partially by the housing.

[0037] In particular, at least one wall or at least part of a wall of the exhaust duct can be formed by one or more housing walls, for example a rear wall of the housing.

[0038] This reduces the number of components required for the furnace's construction and enables a compact design. Furthermore, the heat extracted from the exhaust gases as they pass through the flue can be effectively dissipated into the furnace's surroundings.

[0039] According to at least one embodiment, the furnace has a structure with at least two refractory plates made of a refractory material, for example a refractory fiber material or ceramic material. The structure forms at least part of the exhaust duct.

[0040] Alternatively or additionally, the refractory panels of the construction can contain fireclay brick or a silicate material, for example calcium silicate or vermiculite.

[0041] According to at least one embodiment, the oven has at least one baffle plate to direct the exhaust gas from the combustion chamber into the exhaust duct, in particular through the inlet opening.

[0042] At least one baffle plate is located above the combustion chamber, for example.

[0043] This allows the exhaust gases to be directed in one direction to enter the inlet opening, so that the removal of the exhaust gases from the combustion chamber can be faster or more complete and, in particular, exhaust gases do not accumulate in the combustion chamber.

[0044] According to at least one embodiment, the inlet opening has a minimum dimension of 2 cm or about 2 cm or less.

[0045] In other words, the entrance opening is smaller than 2 cm along one spatial dimension.

[0046] The term "approximately" indicates that standard tolerances may apply. These standard tolerances can range from 0.1 to 0.3 cm.

[0047] The relatively small minimum opening of the inlet port reduces turbulence in the exhaust gas flow.

[0048] According to at least one embodiment, the vertical distance of the exhaust gas outlet from the bottom of the combustion chamber is greater than or equal to the vertical distance of the inlet opening from the bottom.

[0049] Accordingly, in order to get from the combustion chamber to the exhaust outlet, the exhaust gas must first rise in the combustion chamber to reach the inlet opening, then descend in the exhaust channel to be led to the catalyst element, and then rise again to reach the exhaust outlet.

[0050] Accordingly, a particularly long path length is achieved within the exhaust gas channel, which leads to effective cooling of the exhaust gas before it passes through the catalyst element and also to particularly effective heat utilization of the heat extracted from the exhaust gas.

[0051] According to at least one embodiment, the catalyst element and the base are arranged at the same vertical height.

[0052] This can be understood, for example, to mean that the vertical distance of at least one point of the catalyst element from the ground is zero.

[0053] According to at least one embodiment, the vertical distance of the catalyst element from the ground is less than or equal to 20 cm, preferably less than or equal to 10 cm, for example less than or equal to 5 cm.

[0054] By arranging the catalyst element and the base at the same height or at a relatively small vertical distance, the entire height of the furnace is utilized as efficiently as possible, thus enabling the most effective cooling of the exhaust gases before they pass through the catalyst element or the best possible use of the heat extracted from the exhaust gas.

[0055] According to at least one embodiment, the vertical distance of the inlet opening from the floor is greater than or equal to 50 cm, preferably greater than or equal to 80 cm, for example equal to or approximately equal to 90 cm or greater.

[0056] Experiments have shown that the natural chimney effect is sufficient, particularly in such designs, to ensure the removal of exhaust gases without the use of an active ventilation device and at the same time to achieve the cooling of the exhaust gases required for the desired increase in the effectiveness of the catalytic reaction.

[0057] According to at least one embodiment, the length of the exhaust duct is at least twice as long as the vertical distance of the exhaust outlet from the ground, preferably at least three times as long.

[0058] The length of the exhaust duct can be understood as the minimum distance traveled by the exhaust gas within the exhaust duct.

[0059] The relatively long path length of the exhaust gas enables effective heat utilization and effective cooling of the exhaust gas.

[0060] According to at least one embodiment, the length of the first part of the exhaust duct is at least 50 cm.

[0061] It has been shown that this achieves sufficient cooling of the exhaust gas before it flows through the catalyst element.

[0062] According to at least one embodiment, the catalyst element contains a support material. The catalyst element also contains a metal and / or a metal oxide.

[0063] The substrate material can, for example, consist of or contain a ceramic material, or consist of or contain a metal. The substrate material can, for example, have a honeycomb or porous structure.

[0064] The metal oxide, for example aluminum oxide, can be formed as a coating on the substrate material.

[0065] The metal, for example platinum, rhodium and / or palladium, can be embedded in the metal oxide. Alternatively, the metal can be arranged directly on the substrate material.

[0066] The catalytic reaction for the reduction of carbon monoxide is based in particular on the contact of the exhaust gas with the metal and / or the metal oxide.

[0067] According to at least one embodiment, the furnace is designed for the combustion of solid fuels, in particular wood-based solid fuels, for example, for the combustion of wood, wood pellets and / or wood briquettes. Other solid fuels can also be used as fuels.

[0068] Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing.

[0069] The invention will be explained in more detail below with reference to specific exemplary embodiments and associated schematic drawings.

[0070] Figure 1 shows a cross-sectional view of an exemplary embodiment of a furnace 1 according to the improved concept. The furnace 1 is, for example, designed as an insert chimney.

[0071] The oven 1 has a housing 9, within which a combustion chamber 2 is provided. The combustion chamber 2 is closed on one front side of the oven 1, for example by a glass pane or other cover (not shown). The glass pane or cover can be opened, for example, to introduce fuel, such as firewood, into the combustion chamber 2. To operate the oven 1, the fuel can, for example, be placed on a base plate 10 of the combustion chamber 2 and ignited.

[0072] For example, the oven 1 can have a first air inlet opening 14 below the base plate 10 to supply fresh air 17 to the combustion chamber 2. Optionally, the oven 1 can also have a fresh air duct 15 to supply the fresh air 17, for example, to an area above the cover or glass plate. The introduction of fresh air 17 can, for example, be used to create an airwash system to reduce soot buildup on the glass pane.

[0073] For example, at one upper end of the oven 1 there is an exhaust outlet 3, by means of which the oven 1 can be connected to a chimney pipe.

[0074] "Above" and "below" here and in the following refer to a vertical direction 8, which, when the oven 1 is oriented as intended, corresponds to a vertical axis of the oven.

[0075] The oven 1 also features a construction consisting of several plates 11, 12, 13, 19. Together with a rear wall of the housing 9, the construction forms an exhaust duct that connects the combustion chamber 2 with the exhaust outlet 3.

[0076] The assembly includes, for example, a first plate 11, which may be configured, for example, as the rear wall of the combustion chamber 2 or parallel to a rear wall of the combustion chamber 2. A second plate 12 of the assembly is, for example, parallel or substantially parallel to the first plate 11 and arranged between the first plate 11 and the housing 9. A third plate 13 of the assembly, for example, at least partially delimits the combustion chamber 2 on an upper surface of the combustion chamber 2. A fourth plate 19 of the assembly is, for example, arranged parallel or substantially parallel to the third plate 13 and, in particular, between the third plate 13 and the exhaust outlet 3.

[0077] A baffle plate 18 of the furnace is also arranged above the combustion chamber 2 and serves, firstly, to direct exhaust gases 16 rising from or in the combustion chamber 2 into a space between the plates 13, 19, and secondly, to block the exhaust gases 16 from a direct path from the combustion chamber 2 to the exhaust gas outlet 3.

[0078] For example, a catalyst 4 of the furnace is arranged in a space between the first plate 11 and the housing 9. The catalyst 4 can, for example, be plate-shaped and aligned with the second plate 12.

[0079] A gap between the third and fourth plates 13, 19, and a gap between the first plate 11 and the second plate 12, forms a first part 5 of an exhaust gas channel, which directs the exhaust gases 16 from the combustion chamber 2 to the catalyst 4. At the ends of the third and fourth plates 13, 19, respectively, facing away from the first and second plates, there is an inlet opening 7 facing the combustion chamber 2, allowing the exhaust gases 16 to enter the first part 5 of the exhaust gas channel.

[0080] A second part 6 of the exhaust duct is formed by a gap between the second plate 12 and the wall of the housing 9, or by a gap between the catalyst 4 and the rear wall of the housing 9. In a part of the exhaust duct located in the immediate vicinity of the exhaust outlet 3, the exhaust gas 16 can be directed from the exhaust duct 5, 6 through the exhaust outlet 3 out of the furnace 1.

[0081] On their way from the combustion chamber 2 via the inlet opening 7 through the first part 5 of the exhaust gas channel to the second part 6 of the exhaust gas channel and finally to the exhaust gas outlet 3, the exhaust gases 16 must flow through the catalyst 4. This reduces, in particular, the carbon monoxide concentration and also the solid particle concentration, for example, the fine dust concentration, in the exhaust gases 16.

[0082] Because the inlet opening 7 is located above the combustion chamber 2 and the catalyst 4 is at the same height as the base plate 10—in other words, because the vertical distance, i.e., the distance relative to the vertical axis 8, between the base plate 10 and the inlet opening 7 is greater than the vertical distance between the base plate 10 and the catalyst 4, which is, for example, zero or approximately zero—the exhaust gases 16 are directed downwards again on their way through the first part 5 of the exhaust channel. Accordingly, the exhaust gases 16 can cool by several hundred degrees Celsius before flowing through the catalyst 4, which significantly increases the effectiveness of the catalyst 4 in reducing carbon monoxide.

[0083] Because in the described construction the exhaust gases 16 travel a very long path, which lies entirely within the furnace 1, in order to get from the combustion chamber 2 to the exhaust gas outlet 3, the waste heat extracted from the exhaust gases 16 is available as usable heat.

[0084] By using an oven based on the improved concept, the pollutant content of the exhaust gases is reduced in the manner described, and the efficiency of the oven is also increased.

[0085] By redirecting the exhaust gases from the combustion chamber upwards and then downwards at least once through the exhaust duct, the height of the stove is utilized for exhaust gas routing, thus enabling a compact design. In particular, this allows the stove's height to be kept to a minimum. REFERENCE MARK LIST:

[0086] 1 Oven 2 Combustion chamber 3 Exhaust outlet 4 Catalytic converter 5 Exhaust duct 6 Exhaust duct 7 Inlet opening 8 Vertical axis 9 Housing 10 Base plate 11 Plate 12 Plate 13 Plate 14 Air inlet opening 15 Fresh air duct 16 Exhaust 17 Fresh air 18 Baffle plate 19 Plate

Claims

1. A furnace for building heating, comprising a combustion chamber (2), a flue gas outlet (3), a catalytic element (4) as well as a flue gas channel (5, 6), which connects the combustion chamber (2) to the flue gas outlet (3), wherein - the catalytic element (4) is arranged in the flue gas channel (5, 6), - an inlet opening (7) of the flue gas channel (5, 6) is arranged at higher level than the catalytic element (4) with respect to a vertical axis (8) of the furnace (1); and - the inlet opening (7) has a minimum dimension of less than 5 cm.

2. The furnace according to claim 1, characterized in that the furnace (1) comprises a housing (9) and the flue gas channel (5, 6) is at least partially formed by the housing (9).

3. The furnace according to any one of claims 1 or 2, characterized in that the furnace (1) comprises a baffle (18), to pass flue gas (16) from the combustion chamber (2) into the flue gas channel (5, 6).

4. The furnace according to any one of claims 1 to 3, characterized in that the inlet opening (7) has a minimum dimension of 2 cm or about 2 cm or less.

5. The furnace according to any one of claims 1 to 4, characterized in that a vertical distance of the flue gas outlet (3) from a bottom (10) of the combustion chamber (2) is greater than or equal to a vertical distance of the inlet opening (7) from the bottom (10).

6. The furnace according to claim 5, characterized in that a vertical distance of the inlet opening (7) from the bottom (10) is greater than or equal to 50 cm, preferably greater than or equal to 80 cm, for example greater than or equal to 90 cm.

7. The furnace according to any one of claims 5 or 6, characterized in that the length of the flue gas channel (5, 6) is at least twice as large as the vertical distance of the flue gas outlet (3) from the bottom (10).

8. The furnace according to any one of claims 1 to 7, characterized in that the catalytic element (10) contains a carrier material and a metal and / or metal oxide.

9. The furnace according to any one of claims 1 to 8, characterized in that the furnace is configured for combusting solid fuels.

10. The furnace according to any one of claims 5 to 8, wherein the catalytic element (4) and the bottom (10) are arranged at the same vertical level or a vertical distance of the catalytic element (4) from the bottom (10) is less than or equal to 20 cm.