Low-emission oven

Abstract

A furnace for operation with solid fuels and improved pollutant emissions, comprising a tubular combustion chamber 4 which is defined by a cross-section and a height and which has a fuel gas supply 1 for supplying combustion gas at its lower end, through which the combustion gas flows through the combustion chamber 4 to an exhaust pipe 10, as well as cooking, baking and / or radiator elements 8, 9, 11 and / or 12 arranged therebetween and heated by the fuel gas, and a burnout zone 7 located between the combustion chamber 4, the exhaust pipe 10 and the elements 8, 9, 11 and / or 12, characterized in that the combustion chamber 4 is surrounded in the form of a jacket by a space 5 which is thermally separated from the combustion chamber 4, said space 5 being supplied with secondary air via the fuel gas supply 1, which is heated in the space 5 by the combustion chamber 4,whereby heated secondary air is introduced into the primary combustion gas via openings 6 between the combustion chamber 4 and the burnout zone 7 in the space 5.

Description

[0001] The invention relates to an oven, in particular a cooker with low pollutant emissions.

[0002] Fuel-fired ovens and stoves are well known. Solid, liquid, or gaseous fuels are typically used to generate heat. Such stoves and stoves are described in many different ways.

[0003] Wood-fired stoves, particularly those with cooking, roasting, and baking functions, are also known. For example, DE 30 24 680 describes a solid fuel stove as a continuous burner or heating stove, which, in addition to a cooking and roasting area, also has a roasting or baking oven. A solid fuel, usually wood, is ignited by means of a through-burning process, with the combustion air being passed from below through the burning wood into a combustion chamber, and the hot exhaust gases (heating or flue gases) produced by combustion being guided upwards and under a cooking plate and / or around a roasting or baking chamber. Such kitchen stoves are used particularly when independence from an external gas and electricity supply is desired.However, baking temperatures on such kitchen stoves cannot be easily finely regulated, so that constant baking temperatures cannot be achieved in the oven without special precautions, with temperatures usually reaching well over 100°C.

[0004] EP 1 344 979 describes a wood-burning stove that can also be integrated into modern kitchens. The stove described therein features a movable or pivoting heating plate that is positioned horizontally above a firebox.

[0005] Furthermore, EP 2 399 459 describes a wood-fired oven that combines the advantages of vaulted ovens with those of non-vaulted ovens. Such ovens are said to have a specific geometry of the oven casing, with firebricks arranged in a movable manner within the oven casing.

[0006] Furthermore, a heating stove is known from IT 102016000018189 in which a fuel, usually wood, is first pyrolyzed in a separate room and the combustion gases produced are burned in a downstream combustion chamber with the supply of secondary combustion air or oxygen.

[0007] When such furnaces are operated, oxygen-containing gas, usually air, is introduced into a gas stream from the air inlet over the fuel to be burned in a combustion chamber, possibly over baking, cooking and heating surfaces, downstream to a gas outlet such as a stove pipe or chimney, where it is released into the environment.

[0008] The use of fuels, especially solid fuels, produces not only water and CO2, but also particulate matter emissions and climate-damaging emissions of hydrocarbon gases, methane, propane, and butane. The particulate matter emissions produced by wood combustion are particularly relevant. Traditional wood consists of around 50% cellulose, 25 to 30% lignin, and approximately 20% hemicelluloses. The remainder consists of resins, waxes, fats, and oils. When wood is burned, part of the energy must also be used to expel the residual moisture present in the wood. Only then does the decomposition and combustion of the wood begin, with the resulting wood gas reaching temperatures of 250 to 1100°C. The particulate matter pollution produced by wood combustion poses a particular environmental problem when using wood stoves and wood-burning ovens.

[0009] The invention therefore aims to provide a stove or a range that can be operated with solid fuels such as coal, charcoal, and especially wood, in which the aforementioned environmental problems are avoided or at least significantly reduced. This objective is achieved by a stove having the features defined in the main claim. Further preferred features can be found in the subclaims. Such a range is also particularly suitable as an outdoor range.

[0010] According to the invention, it was found that the problems associated with a conventional combustion chamber can be avoided in which, in the usual way, a hot combustion gas, in particular hot combustion air (flue gas), is generated by burning a solid fuel such as wood. This hot combustion gas is then further burned in a downstream burnout zone with the aid of additionally supplied heated secondary combustion gas, such as air (oxygen), in a so-called afterburn or burnout. The procedure according to the invention is that secondary air is passed around the combustion chamber, where it is preheated and heated. This heated secondary air is then fed to the hot primary combustion gas (flue gas) at the end of the combustion chamber. By feeding this preheated hot secondary combustion air, the remaining climate-damaging pollutants such as soot, etc.The fuel is then further combusted at a generally even higher temperature in a post-combustion or burnout zone, producing a low-pollutant exhaust gas that is almost or completely free of dust, organic hydrocarbons, particularly polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides, carbon monoxide, and particulate matter such as soot. It has been shown that the process according to the invention prevents the formation of thermally generated nitrogen oxides.

[0011] In the preferred embodiment, the combustion chamber of the furnace according to the invention has a wall with good heat conduction, preferably made of iron, steel or stainless steel but also ceramic.

[0012] The combustion chamber itself is usually elongated, preferably in the form of a shaft defined by its cross-section and its height / length. This shape allows the carbonization gases produced during combustion to mix well with the residual oxygen in the fuel or flue gas, thus optimizing combustion.

[0013] Around the wall surrounding the combustion chamber (primary combustion air or flue gas) is another chamber for secondary combustion air, which conducts heat but is separated by the wall. This secondary chamber is also supplied with an oxygen-containing gas, preferably air, which is warmed or heated to a high temperature. The supply can be separate or via the same supply opening for the primary combustion gas. The heated gas or air (secondary air) is then fed into the primary combustion air at the upper end of the combustion chamber (downstream of the entire exhaust gas / flue gas flow), where it burns the remaining unburned soot, particulate matter, and wood gases into water and CO2. Any nitrous gases and carbon monoxide present are also further burned. This essentially takes place in a burnout zone downstream of the combustion chamber.This additional post-combustion or burnout increases the temperature of the combustion gas / flue gas or air even further, which not only removes pollutants but also leads to an increased energy yield.

[0014] The supply from the secondary air chamber to the upper section of the combustion chamber is introduced into the combustion air (flue gas) flow through designated openings. Preferably, the combustion chamber is narrowed or tapered in its upper section, downstream of the combustion flow.

[0015] In a particularly preferred embodiment, the combustion chamber, which is usually designed with a round and / or oval cross-section, is narrowed or tapered in its upper region downstream of the combustion gas or air. This constriction is expediently annular or possibly oval. In this way, the exhaust gas flow of the combustion or flue gas is accelerated and, analogous to Bernoulli's law, a negative pressure is created in this region. It has therefore proven expedient to introduce the previously described, already heated secondary combustion air into the normal primary flow of combustion air (flue gas) precisely in this region. The negative pressure created in this region draws heated air generated in the secondary air shaft surrounding the combustion chamber into the primary combustion flow (flue gas).

[0016] Openings for supplying heated secondary air are therefore located in the upper narrowed or tapered cross-section of the combustion chamber. Venturi nozzles are preferred as the primary air inlet. Such nozzles are typically arranged in a ring-shaped pattern in this tapered area. By using Venturi nozzles, the secondary combustion air is introduced into the primary combustion air at an additional rate of acceleration and then directed into the burnout zone. This process has the effect of a bellows.

[0017] In this way, the combustion air flow is accelerated according to the Bernoulli effect. The primary combustion air, enriched with the heated secondary combustion air, is then mixed with the primary combustion air and then directed into the downstream burnout zone, where the remaining wood gases, soot, and fine dust particles or soot are combusted with additional energy recovery. This creates a low-emission, even hotter exhaust gas.

[0018] In a preferred embodiment, the combustion air is introduced into the combustion chamber from below, preferably above an ash box arranged below the combustion chamber, but preferably below the fuel, usually wood.

[0019] The combustion chamber itself is limited in its lower area by an air-permeable grate, which supports the fuel above it, such as coal and especially wood.

[0020] In a further preferred embodiment, the combustion chamber in this area is lined with a ceramic jacket or ceramic ring. A preferred ceramic is fireclay. The ceramic jacket serves to hold the fuel. The ceramic also stores the heat of combustion, so that when the chamber is refilled (preferably from above) with fuel, it heats up more quickly, resulting in even heat production. The ceramic jacket is preferably designed in such a way that it leads to a narrowing of the cross-section or diameter of the combustion chamber, which then widens again above the jacket, i.e. downstream of the burner, i.e. becomes larger. This also leads to an acceleration of the supply of combustion gas or combustion air. In addition, the resulting narrowing of the chamber cross-section accelerates the air supply, which increases combustion in a similar way to bellows, whereby the fuel or gas is heated up.The fuel gasifies better. This allows solid fuel, especially logs, to gasify particularly well, and the air temperature is increased even further.

[0021] The combustion air, preferably introduced below the air-permeable grate, is regulated in a suitable embodiment by means of a control mechanism. The incoming combustion air is usually passed above the combustion chamber and the burnout zone (i.e., downstream) to heat-conducting or heat-dissipating elements up to the exhaust pipe, where it heats them up and releases heat.

[0022] In a preferred embodiment, an opening that can be closed with a removable lid is provided above the combustion chamber, through which the fuel is introduced into the combustion chamber from above. The stove therefore has a large opening above the combustion chamber in the form of a submerged combustion stove, through which the solid fuel can be introduced into the combustion chamber from above. For this purpose, the stove according to the invention has a removable lid or plate above the opening of the combustion chamber. This lid can also be designed as a hotplate or as a pan or wok. This combustion according to the invention is suitable for cooking, baking and heating in places without electricity or other energy sources such as oil, etc., such as remote huts and alpine pastures.

[0023] The combustion technology can also be installed in room heaters / boilers, especially when very low power levels are required.

[0024] The invention will be explained in more detail with reference to the accompanying figures. Fig.1 shows a section through a furnace according to the invention. Incoming combustion air is introduced into the furnace via a power regulator 1 from below, but above an ash pan and below a support grate 2. Above this support grate 2, in the lower part of the combustion chamber 4, a ceramic ring 3 is arranged. The grate itself supports the wood, which is layered into the combustion chamber 4 from above via a removable plate 9 and is burned in the combustion chamber 4. The combustion chamber 4 is surrounded by a separate shaft or chamber for secondary air. This secondary air from the shaft 5 is strongly heated by the heat of the combustion chamber and is heated up considerably as it flows / migrates from bottom to top, where it is then introduced into a narrowed area of ​​the combustion chamber 4 via openings 6, which are preferably Venturi ring nozzles, in the upper area of ​​the combustion chamber 4, where it leads to intense afterburning which takes place in the burnout zone 7.The now extremely heated combustion air is then passed downstream via a heat channel 8, above which the hotplates 11 are arranged, into the exhaust air pipe 10. In a further preferred embodiment, mechanically adjustable slide valves or flaps 13 are preferably arranged in the burnout zone 6, which heat a hearth furnace 12. The hearth furnace 12 is either supplied directly with the combustion air, but preferably the furnace 12 is surrounded by a shell to be supplied with the combustion air. The oven 12 is then heated via the wall of this shell. List of reference symbols 1 combustion gas supply 1.1 Combustion gas supply regulator 2 grate for holding the fuel 3 Ceramic cladding, ceramic ring 4 combustion chamber 5 Shaft, chamber for heating the secondary air 6 Supply opening for secondary air 7 Burnout zone 8 hot air duct 9 Opening for loading / refilling fuel and for pans, pots, wok 10 Exhaust pipe, chimney 11 cooking zones 12 Oven 13 diverter controls for oven and stove 14 Narrowed area 15 ash drawer 16 Sealing of the shaft space for heating the secondary air QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 30 24 680

[0003] EP 1 344 979

[0004] EP 2 399 459

[0005]

Claims

[1] Oven for operation with solid fuels and improved pollutant emission comprising a tubular combustion chamber 4 which is defined by a cross-section and a height and which has at its lower end a fuel gas supply 1 for supplying combustion gas, through which the combustion gas flows through the combustion chamber 4 to an exhaust pipe 10, as well as cooking, baking and / or radiator elements 8, 9, 11 and / or 12 arranged therebetween and heated by the fuel gas and a burnout zone 7 lying between the combustion chamber 4, the exhaust pipe 10 and the elements 8, 9, 11 and / or 12, characterized bythat the combustion chamber 4 is surrounded in the form of a shell by a space 5 which is separated from the combustion chamber 4 in a heat-conducting manner, this space 5 being supplied with secondary air via the fuel gas supply 1, which is heated in the space 5 by means of the combustion chamber 4, heated secondary air being introduced into the primary combustion gas via openings 6 between the combustion chamber 4 and the burnout zone 7 in the space 5. [2] Oven according to claim 1, characterized by that the cross-section of the combustion chamber 4 is narrowed in its upper region 14 downstream of the combustion gas. [3] Oven according to one of the preceding claims, characterized by that in the narrowed area 14 Venturi nozzles (6) are arranged for introducing the heated secondary air. [4] Oven according to one of the preceding claims, characterized by that the combustion chamber (4) is lined in its lower area with a ceramic jacket (3) which narrows the primary gas flow. [5] Oven according to one of the preceding claims, characterized by that the combustion chamber (4) has an air-permeable grate (2) for holding the fuel. [6] Oven according to one of the preceding claims, characterized by that the furnace has an opening above the combustion chamber (4) with a removable lid (9) through which the combustion chamber (4) can be charged with fuel. [7] Oven according to one of the preceding claims, characterized by that the combustion air supply 1 can be controlled via a combustion air regulator 1.

1. [8] Oven according to one of the preceding claims, characterized by that the oven has a baking chamber 12 which can be operated additionally or separately with top and / or bottom heat by means of a changeover device, wherein the changeover device is connected downstream of the after-burning zone (7). [9] Oven according to one of the preceding claims, characterized bythat the furnace has a hearth plate 11 which is heated via a discharge channel 8 located downstream of the combustion. [10] Oven according to one of the preceding claims, characterized by that an ash drawer is arranged below the combustion chamber (4) and below the grate (2).

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