Retrofittable foam ceramic filter system (fine dust filter) with partially open installation in the combustion chamber for the direct reduction of dust and gaseous pollutant emissions

Abstract

Retrofittable filter system (1) for reducing fine dust and gaseous emissions in existing solid fuel combustion systems, characterized in that an open-pore foam ceramic filter element (2) based on silicon carbide and / or aluminum oxide is mounted directly in the upper region of the combustion chamber, above the flame, wherein the filter element (2) is embedded in a carrier unit or carried by a frame, and a natural draft opening (4) remains in the upper / front combustion chamber section, through which flame tips and exhaust gases can escape unhindered.

Description

[0001] The present invention relates to a retrofittable filter system for reducing particulate matter and gaseous emissions in existing small combustion systems, in particular fireplace stoves, tiled stoves, stove fireplaces, and other solid fuel fireplaces. It particularly concerns a filter element arranged in the combustion chamber above the combustion zone, which is installed without completely sealing off the upper combustion chamber area and reduces emissions directly at the source.

[0002] The aim of the invention is to provide a retrofittable filter system that is positioned directly above the flame in the combustion chamber, while leaving a defined natural draft opening (bypass opening) open in the upper / front area of ​​the combustion chamber. This prevents the free flue gas path from being completely blocked while simultaneously maintaining sufficient flow and flame penetration.

[0003] The central filter element consists of an open-cell foam ceramic structure, preferably based on silicon carbide (SiC) or aluminum oxide (Al2O3). The porous structure allows for direct thermal and mechanical stress in the flame area, while fine dust particles and volatile pollutants are physically separated and, if necessary, catalytically converted.

[0004] The geometry of the filter element is conical or curved, allowing it to fit into the upper part of the combustion chamber without completely occluding it. It is mounted using a heat-resistant frame or mounting system, e.g., made of stainless steel or temperature-resistant ceramic fiberboard, which is firmly anchored or clamped into the combustion chamber.

[0005] A free space (bypass) is deliberately created in the front area of ​​the upper firebox to accommodate the stove's natural draft and allow hot flue gases to escape freely, as well as the passage of flame tips. This preserves the characteristic flame pattern and prevents the firebox from "suffocating."

[0006] The design allows the foam ceramic filter to be positioned precisely in the primary exhaust stream without completely throttling or encapsulating the exhaust path. At the same time, the ceramic mass and large active surface area achieve a significant reduction in particulate matter and carbon monoxide concentrations.

[0007] The invention claims the retrofitting of the described filter system into existing fireplaces without requiring any modification to the fireplace's external structure. Retrofitting can be carried out without tools or with minimal effort.

[0008] In a preferred embodiment, the foam ceramic is provided with a catalytically active layer which oxidatively converts in particular carbon monoxide, unburned hydrocarbons or organic compounds at temperatures between 200 °C and 500 °C.

[0009] The combination of direct placement above the combustion zone, partially open natural draft guidance and heat-resistant support integration represents a novel retrofitting principle that is both effective in terms of emissions technology and minimally invasive in terms of structure.

[0010] The scope of the invention includes: • the process of retrofitting existing fireplaces with an open-pore foam ceramic filter, • the device for partially open integration in the combustion chamber with open draught area, • all designs in which a bypass or an open flame outlet is retained to maintain natural draught in the upper combustion chamber area.

[0011] In a preferred embodiment, the filter support unit consists of a fireproof frame plate, for example, made of vermiculite or fireclay, into which the ceramic filter element is embedded. Alternatively, the support can be provided by a stainless steel retaining frame, which is attached to the inner casing of the combustion chamber using clamps, locking lugs, or screw flanges.

[0012] The filter element's geometry and conical arrangement can be designed to penetrate the central part of the flue gas flow above the flame, while allowing unthrottled flame and gas passage through a natural draft opening at the side or front. This opening can be fixed or of variable size (e.g., as an adjustable segment).

[0013] The filter element can be manufactured in various pore sizes (PPI values), depending on the desired balance between pressure drop and filtration performance. Typical values ​​range from 10 to 45 PPI. If required, the foam ceramic can be designed to be regenerable by being removable and thermally or mechanically cleanable.

[0014] The retrofit can be implemented as a plug-in module or as part of a customer-specific adaptation for existing fireplaces. The geometry of the component can be oval, round, segmented, or polygonal, as long as the central feature—a partially open arrangement in the upper combustion chamber with a defined bypass zone—is retained.

[0015] The system is suitable for all wood-fired single-room fireplaces as well as smaller, stationary biomass heating systems. It is particularly advantageous for use in older systems that no longer meet the current requirements of the 1st Federal Immission Control Ordinance (BImSchV) due to a lack of particulate matter separation. The system described allows operators to implement a cost-effective retrofit solution and avoid shutdowns.

[0016] The invention can also be combined with digital temperature sensors or simple thermal indicators to indicate the optimal exhaust gas temperature for the filter's catalytic effect. This also allows for optimized combustion control by the end user.

[0017] The retrofitting process can be performed by both specialist companies and end users themselves, as no complex interventions in the fireplace are required. Installation takes just a few minutes and requires no special tools.

[0018] The invention encompasses all designs in which a ceramic or metallically supported catalyst or filter is positioned within the combustion chamber in such a way that direct exhaust gas treatment is provided while maintaining natural draft.

[0019] All conceivable combinations of filter shape, carrier material, installation type and coating which implement the principle of partially open retrofitting above the flame with direct emission reduction are covered by the scope of protection of this invention.

[0020] In further embodiments, the filter element can be designed to automatically clean itself through the exhaust gas, especially at sufficiently high temperatures (pyrolysis effect). The open structure prevents complete blockage and allows for largely maintenance-free operation.

[0021] Optionally, the support unit can be equipped with secondary guide structures or baffles to specifically direct the flow through the filter area. These can also be made of ceramic or metal and can be integrated into the support unit or installed separately.

[0022] The natural draft opening can be designed not only as an open area in the upper combustion chamber, but also as a deliberately shaped flow channel or gap created by the design of the surround. This provides a low-pressure bypass through which excess flame and exhaust gas can be discharged unhindered, even under strong draft conditions.

[0023] The invention is particularly well-suited for systems with a viewing window or a glass flue, as the flame remains visually visible. This means that the retrofit poses no visual or practical disadvantages for the end user.

[0024] The design is suitable for both manually operated fireplaces and automated furnaces or systems with control systems. Temperature monitoring can be integrated if required, e.g., via thermocouples or color indicators, to indicate whether the filter unit is operating within the optimal temperature range.

[0025] The filter element's enclosure can be factory-adapted to various combustion chamber geometries or created on-site using replacement plates, ceramic inserts, or modular mounting kits. A multi-part design (filter insert + support system) is also possible.

[0026] In industrial or commercial systems, the invention can be scaled up or deployed serially in multiple stages. A combination with secondary air supply, electronic exhaust gas sensors, or existing cleaning mechanisms is possible, improving the overall effectiveness.

[0027] The invention offers an immediately effective, structurally simple, and economically viable option for retrofitting and reactivating existing, emission-critical systems that would otherwise be unusable. By installing the system, the user ensures legally compliant operation of their fireplace in accordance with the 1st Federal Immission Control Ordinance (BImSchV).

[0028] The invention can be offered in series or as a customized solution. Its modular design, shallow installation depth, and the variety of available materials make the system attractive for both new installations and renovation projects and for specialized tradespeople.

[0029] The invention relates to a retrofittable filter and catalyst system for the direct reduction of particulate matter and gaseous emissions in existing fireplaces. The central filter element consists of open-pore foam ceramic based on silicon carbide and / or aluminum oxide, which is arranged above the flame zone directly in the combustion chamber. It is installed partially open, leaving a defined natural draft opening in the front or upper area of ​​the combustion chamber. This preserves the flame passage, the natural flow, and the visual impression of the fire.

[0030] The enclosure is made of a temperature-resistant frame or a fireproof embedding (e.g., vermiculite, fireclay, or stainless steel). The retrofit is minimally invasive, without any structural changes to the fireplace, and can be carried out either at the factory or on-site. A catalytic coating is available as an option.

[0031] The invention thus enables legally compliant retrofitting of existing fireplaces in accordance with the 1st BImSchV while simultaneously maintaining draught characteristics and flame pattern. Fig. 1: Installation variant with conical support structure and front bypass channel

[0032] The invention has broad industrial applications in furnace and heating technology. It is suitable for fireplaces and tiled stoves, heating fireplaces, single-room heating systems, and commercial biomass combustion systems. Its modular and scalable design also allows for use in industrial flue gas or exhaust systems.

[0033] The features and methods presented in the description can be patented and legally protected both individually and in combination. All variants and further developments based on the basic principle of partially open filter integration in the combustion chamber are covered by the scope of protection of this invention.

[0034] In a further embodiment of the invention, the foam ceramic filter element is conically shaped and is embedded in a correspondingly shaped recess of a carrier plate made of vermiculite, fireclay, or a similar non-combustible material. The conicity serves to ensure secure axial fixation and increase the contact area with the exhaust gas flow.

[0035] Alternatively or additionally, the filter element can be encased in a metal support frame, preferably made of steel or stainless steel. This frame ensures mechanical stability and allows reversible installation and removal for maintenance or cleaning purposes.

[0036] The surface of the foam ceramic can be coated with a catalytically active coating, for example, based on metal oxides such as manganese oxide, cerium oxide, copper oxide, or precious metal compounds. This coating increases the effectiveness in the oxidative conversion of CO, VOCs, and other harmful gases and improves the overall performance of the filter, especially at medium exhaust gas temperatures (approximately 200 °C to 500 °C).

[0037] The combination of open-cell structure, catalytic activation and stable carrier integration enables a long-lasting, low-maintenance and emission-effective retrofit solution with high adaptability to existing combustion chamber geometries.

[0038] The conical geometry of the filter body allows the foam ceramic element to be securely and stress-free inserted into a precisely fitting receptacle. It is preferably embedded in a conical recess in a carrier plate made of vermiculite or fireclay, with the conicity ensuring self-centering and positive fixation. This design prevents unwanted movement or loosening during repeated temperature changes.

[0039] Alternatively or additionally, the filter element is mounted in a rigid metal support frame. The frame can be rectangular, round, or conical and is made of temperature-resistant steel or stainless steel, ideally V2A or V4A. The support can be equipped with mounting brackets, clamps, or threaded elements for direct installation in the combustion chamber.

[0040] In a further advantageous embodiment, the surface of the foam ceramic is provided with a catalytically active functional layer. This layer preferably consists of a combination of metal oxides, for example, based on manganese, cerium, copper, or platinum group metals. The catalytic surface reacts with exhaust gas components such as carbon monoxide (CO), organic compounds (VOCs), or other oxidizable gases, converting them into less harmful substances (e.g., CO2 and H2O) at temperatures above approximately 200 °C.

[0041] The coating can be applied by dipping, spraying, sol-gel, or flame spraying. It is permanently bonded to the ceramic substrate and resistant to thermal aging, soot, or condensate buildup. The coating's structure is designed to preserve the open pore structure of the foam ceramic, thus minimizing pressure loss in the system.

[0042] Through the combination of catalytic reaction and physical particle separation, a significant reduction of both solid and gaseous pollutants can be achieved - while at the same time maintaining the free natural draught via the deliberately left open opening in the upper / front combustion chamber.

[0043] The structure allows for easy maintenance or replacement of the filter, as the conical design allows the element to be removed either upwards or via a modular support system. The use of additional sealants is often unnecessary thanks to the self-centering conical shape.

[0044] The interaction of geometric embedding, mechanical framing and catalytic surface functionality creates a compact, durable and efficient filter system that is specifically designed for retrofitting single-room combustion systems with open combustion chamber designs.

[0045] The special innovation lies in the targeted positioning within the combustion chamber, the combination of partially open draft behavior and direct emission reduction through multifunctional filter ceramics, which are used in a physically, chemically and flow-optimized manner.

[0046] In a particularly preferred embodiment, the foam ceramic filter element has a structurally reinforced edge region consisting of densely sintered, closed solid ceramic. While the central surface of the filter element remains open-pored to conduct the exhaust gas flow and treat particulates and gaseous emissions, the outer region is designed as a closed, compact ceramic zone all around.

[0047] This edge zone serves to mechanically stabilize the component under high thermal and mechanical loads and at the same time increases the fracture and edge strength of the element, especially in the case of conical or cantilevered mounting.

[0048] The transition zone between the open-pore center and the closed outer edge is form-fitting and thermally homogeneous, ensuring a stress-free connection between the functional area and the edge reinforcement. Production can be achieved by controlled thickening of the ceramic material at the edge or by targeted post-treatment (e.g., densification, glazing, secondary sintering).

[0049] The closed ceramic zone can also be used as a fixing or pressing edge to insert the filter element into a conical or cylindrical support unit without additional retaining rings or clamping mechanisms. The combination of the open filter area and the closed edge area enables a very robust and simultaneously flow-optimized design.

[0050] Especially when embedded in fireproof panels (e.g., vermiculite or fireclay) or when mounted in steel frames, edge reinforcement supports seal-free installation, as the solid edge area acts as a stop surface. Furthermore, the risk of chipping or chipping at the edges is significantly reduced.

[0051] This design allows for a longer service life of the filter element, improves heat shock resistance and is particularly suitable for use in highly stressed combustion chamber positions with direct flame contact or high tensile load.

Claims

[1] Retrofittable filter system (1) for reducing particulate matter and gaseous emissions in existing solid fuel combustion plants, characterized by that an open-pore foam ceramic filter element (2) based on silicon carbide and / or aluminum oxide is mounted directly in the upper region of the combustion chamber, above the flame, wherein the filter element (2) is embedded in a support unit or carried by a frame, and a natural draft opening (4) remains in the upper / front combustion chamber section, through which flame tips and exhaust gases can escape unhindered. [2] Filter system (1) according to claim 1, characterized by that the filter element (2) is conical (3), curved or cylindrical and has a defined flow direction of the exhaust gases. [3] Filter system (1) according to one of the preceding claims, characterized bythat the filter element (2), wherein the ceramic element preferably consists of silicon carbide (SiC), aluminum oxide (Al2O3) or a combination of these materials and / or is coated with at least one catalytically active noble metal from the group platinum (Pt), palladium (Pd), rhodium (Rh) or mixtures thereof and with a catalytically active layer comprising metal oxides for converting carbon monoxide, VOC or other gaseous emissions. [4] Filter system (1) according to one of the preceding claims, characterized by that the support unit is made of vermiculite, fireclay or a comparable non-combustible, heat-resistant material. [5] Filter system (1) according to one of the preceding claims, characterized by that the support unit alternatively or additionally consists of a steel or stainless steel frame. [6] Filter system (1) according to one of the preceding claims, characterized bythat the natural draft opening (4) forms a fixed, partial or adjustable opening in the area above or in front of the filter element in order to maintain the free flow of exhaust gases and the escape of flames. [7] Filter system (1) for retrofitting existing fireplaces with a filter system according to one of claims 1 to 6, characterized by that the filter element (2) is inserted into the combustion chamber without structural changes to the fireplace, and that sufficient natural draught and flame escape are ensured by keeping the upper combustion chamber partially open. [8] Filter system (1) according to claim 7, characterized by that the filter system (1) is manufactured as a module with defined dimensions and is installed in the combustion chamber either without tools or by simple mechanical fixing (e.g. screws, clamps, insert). [9] Filter system (1) according to claim 7 or 8, characterized bythat the filter element (2) is replaceable and regenerable, for example by thermal cleaning or replacement. [10] Filter system (1) according to one of claims 1 to 9, characterized by that the system is used to comply with the requirements of the BImSchV (Federal Immission Control Ordinance) for the reduction of particulate matter and carbon monoxide in existing fireplaces. [11] Filter system (1) according to one of claims 1 to 10, characterized by that the filter element (2) is conically shaped and is positively inserted into a likewise conically shaped recess of a carrier unit made of vermiculite or fireclay. [12] Filter system (1) according to one of the preceding claims, characterized by that the filter element (2) is enclosed in a metallic holding frame, preferably made of steel or stainless steel. [13] Filter system (1) according to one of the preceding claims, characterized bythat the surface of the foam ceramic filter (2) is provided with a catalytically active coating, in particular based on metal oxides for reducing emissions of gaseous pollutants. [14] Filter system (1) according to one of the preceding claims, characterized by that the combination of conical shape (3), positive support embedding and / or metallic holding frame is used to combine the thermal, mechanical and catalytic functionality in a modular retrofit system. [15] Filter system (1) according to one of claims 1 to 14, characterized by that the foam ceramic filter element (2) has a circumferential edge region made of closed, densely sintered solid ceramic, while the central region is open-pored for flow through. [16] Filter system (1) according to claim 15, characterized bythat the closed edge zone (3) serves for mechanical stabilization, fracture resistance and as a stop surface for embedding in a carrier unit. [17] Filter system (1) according to one of claims 15 or 16, characterized by that the closed edge zone is positively and thermally homogeneously connected to the open-pore surface, and that the transition zone is stress-free. [18] Filter system (1) according to one of claims 1 to 17, characterized by that the filter element (2) with a closed edge zone is inserted conically (3) into a carrier plate (e.g. made of vermiculite or fireclay) or alternatively is held in a steel or stainless steel frame. [19] Filter system (1) according to one of the preceding claims, characterized by that the edge zone of the filter element (2) serves as a seal-free pressing surface or self-supporting fixation in the installation situation.

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