Catalyst for exhaust systems (exhaust and / or flue pipe) of fireplaces and stoves, especially fireplaces, to reduce dust and gaseous pollutant emissions (OfenKAT)

Abstract

Catalyst (2) (OfenKAT) for reducing dust and gaseous pollutant emissions in exhaust gas systems of combustion plants, in particular fireplaces, tiled stoves and workshop stoves, characterized in that the catalyst comprises an open-pore, ceramic element which is arranged in a module frame within a module housing, 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.

Description

The invention relates to a catalytic converter, in particular a ceramic catalytic converter (hereinafter "FurnaceKAT"), for reducing dust and gaseous pollutant emissions in exhaust systems and / or exhaust systems. The catalyst is provided in particular for use in chimney furnaces, tile furnaces and conventional firing systems.The invention relates to the field of the furnace and furnace industry and is suitable for various applications such as industry, industrial, residential, agricultural and building equipment applications. It relates in particular to heating and firing systems and to their exhaust gas guidance systems.The object of the invention is to provide an apparatus by which both dust and gaseous pollutants such as carbon monoxide (CO), organic compounds (VOC) and nitrogen oxides (NOx) can be effectively reduced without excessively increasing the exhaust back pressure.This object is achieved by a catalytic converter which has an open-porous ceramic element which is arranged in a module frame within a module housing. The ceramic element is permeable to exhaust gases and can be installed in the smoke pipe or exhaust pipe of the firing system.The ceramic element preferably consists of an open-pore or foam-like structure, such as a foam ceramic, for example, and has a high inner surface. Silicon carbide (SiC) and aluminum oxide (Al 2 O 3) which are distinguished by high temperature and corrosion resistance, are used as base materials.The surface of the ceramic body is coated with at least one catalytically active noble metal. Platinum (Pt), palladium (Pd), rhodium (Rh) or combinations thereof are used as catalyst metals. The coating is preferably effected by impregnation or coating techniques which ensure uniform distribution of the catalyst on the inner structure.The catalyst is designed to be integrated into existing exhaust pipe systems without requiring extensive redesigns. The construction enables a modular construction which allows simple maintenance and exchangeability.The open-pore structure of the ceramic element retains particles (dust), while the catalytic surface simultaneously assists the conversion of gaseous pollutants into less harmful components such as CO 2 and water vapor.The use of the furnace KAT according to the invention thus contributes to compliance with legal emission limit values and at the same time increases the environmental friendliness of existing and new firing systems.Catalytic converter (FurnaceKAT) for reducing dust and gaseous pollutant emissions in exhaust systems of firing systems, in particular in chimney furnaces, tile furnaces and conventional heating furnaces, characterized in that the catalytic converter has an open-pored ceramic element which is arranged in a module frame within a module housing, wherein the ceramic element consists of silicon carbide (SiC), aluminium oxide (Al 2 O 3) or a combination of these materials and is coated with at least one catalytically active noble metal from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh) or a mixture thereof.Catalyst according to Claim 1, characterized in that the open-pore ceramic element is designed as foam ceramic.Catalyst according to any of the preceding claims, characterized in that the catalytically active coating is applied by means of impregnation or a comparable surface treatment.Catalytic converter according to one of the preceding claims, characterized in that the module housing is designed for integration into a smoke tube or exhaust pipe of a firing system.Catalyst according to one of the preceding claims, characterized in that the ceramic element has a high specific surface area in order to offer the largest possible catalytically active reaction surface.The invention relates to a ceramic catalytic converter (furnace KAT) for reducing pollutant emissions in exhaust gas systems of furnaces. The central element is an open-pored, preferably foam ceramic component made of silicon carbide or aluminum oxide, which is coated with noble metals such as platinum, palladium or rhodium. The construction is modular and permits simple retrofitting into existing systems for emissions reduction.The invention relates to a catalyst for reducing emissions in exhaust systems of combustion systems, in particular for reducing particulate matter, carbon monoxide (CO), volatile organic compounds (VOC) and nitrogen oxides (NOx). The invention is provided in particular for solid fuel furnaces, for example chimney furnaces, tile furnaces or single-space furnace installations.In conventional furnaces without downstream exhaust gas treatment, considerable quantities of substances harmful to the environment and health get into the atmosphere. The use of electrostatic filters or conventional particle traps is technically complicated and maintenance-intensive. A simple and at the same time effective possibility for reducing emissions is the use of catalytically active ceramics.It is therefore an object of the present invention to provide a simple, retrofittable, long-lived and low-maintenance catalyst which removes both dust and gaseous pollutants from the exhaust gas stream without substantially impairing the flue pull or the exhaust gas flow.This object is achieved by a catalyst according to claim 1. The core of the catalytic converter is an open-pored ceramic element with a high specific surface, which is integrated into a module housing and is inserted into the smoke tube or exhaust pipe. The porous structure allows for the mechanical retention of particles (e.g., soot) while the catalytic coating aids in the conversion of noxious gases.Heat-resistant ceramics such as silicon carbide (SiC) or aluminum oxide (Al 2 O 3) are used as carrier materials. These are distinguished by high temperature resistance (>180° C.), corrosion resistance and mechanical stability. The catalytic coating consists of at least one noble metal from the group platinum, palladium or rhodium. Depending on the application, it is also possible to use a multiple catalyst in which a plurality of these metals are combined.The open-pore ceramic element can be designed as foam ceramic with cell sizes between 10 and 50 ppi (pores per inch). This element is held in a metal or ceramic frame embedded in a durable housing. The entire module can be designed as a cartridge which can easily be inserted or screwed into existing smoke tubes.When the exhaust gas flows through the open-pored ceramic element, particles are mechanically separated. At the same time, CO, VOC and NOx are oxidized or reduced on the catalytically active surface under the action of oxygen. The exhaust gases leave the module in a cleaned manner without an electrical connection or active control being required.Advantages of the Invention:• Simple retroposability in existing ovens or installations• Passive operation without power supply• Low maintenance effort• High long-term stability of the ceramic structure• Modular construction which facilitates replacement or cleaning• Versatile in households, agriculture, industrial use and industryThe invention can be used in the following areas:• Single Room Firing Facilities in Residential Buildings• Workshop ovens or wood heaters in business• Mobile heaters in construction containers or construction sites• Agricultural small-firing installations• Combination with pellet furnaces or schewood furnacesThe central ceramic element of the catalyst is made of high-temperature-resistant, oxidation- and corrosion-resistant materials. Preference is given to:Silicon carbide (SiC): This material has a very high thermal conductivity, mechanical strength and temperature resistance of up to more than 1400° C. It is also insensitive to thermal shocks and is naturally suitable as a support material for catalytic coatings.Aluminum oxide (Al 2 O 3): aluminum oxide (also known as alumina or corundum) is a ceramic material with high chemical resistance and temperature stability. It forms a suitable base structure for catalysts in the temperature range up to about 1200° C.Both materials can be used individually or in combination (e.g. as composite ceramic).The open-pore structure can be produced by foam sintering, extrusion or slip casting.The pore size (e.g., 10-40 ppi) is adjusted to the desired pressure loss and filter properties.Catalytic Coating: The ceramic structure is coated with one or more layers of a catalytically active noble metal. The following are used:Platinum (Pt): Particularly effective in the oxidation of carbon monoxide (CO) and unburned hydrocarbons (VOC).Palladium (Pd): Less expensive than platinum, with high activity at lower temperatures.Rhodium (Rh): It is particularly suitable for reducing nitrogen oxides (NOx).The coating is effected by impregnation or sol-gel processes, so that a uniform, highly dispersed catalyst layer is formed on the inner surface. The contact of the exhaust gases with these active zones allows rapid and effective conversion of noxious constituents.Design of the exhaust pipe / installation environment: The exhaust pipe in which the catalytic converter is installed is typically manufactured from metal (e.g. stainless steel or enameled steel) and has standardized diameters (e.g. 120 mm, 130 mm, 150 mm) as used in single-chamber furnace installations. The tube carries the hot exhaust gases out of the combustion chamber to the outside.The catalytic converter is designed such that it can be inserted into the exhaust pipe in a form-fitting manner. Two typical variants are:• Insert cartridge: The catalytic converter is inserted axially into the tube and held by means of a sealing seat or spring clamp.• Screw-in module: The module is fixed in the tube by a screw or bayonet connection and can easily be removed during maintenance.A flexible seal or heat seal prevents exhaust gases from passing the cartridge. The module frame is made of temperature-resistant stainless steel (e.g., V4A) and mechanically protects the ceramic element.Thermodynamic aspects and integration: The ceramic element is positioned in the exhaust pipe in such a way that the hot exhaust gas stream flows directly through it. The catalytic activity begins at about 200°C and reaches its full effect at 300-500°C, which corresponds to the typical temperature range of chimney furnaces. The open-pore structure ensures that the pressure loss remains minimal and the train of the chimney is maintained. Radiating heat to the exhaust pipe helps the thermal stability of the plant and avoids condensation effects. If required, the catalytic converter can also be integrated into double-walled systems or can be thermally decoupled by heat shields.Cleaning and maintenance: Thanks to the open-pore structure, the catalyst is largely self-cleaning. However, in the case of fuels containing very soot or incomplete combustion, some of the pores may become clogged. In this case, the module can be removed and burnt out or mechanically cleaned. Alternatively, modular replacement is possible.Cascadable catalyst modular system: An important advantage of the invention lies in the modular design of the catalyst (FurnaceKAT). The ceramic element with catalytic coating is designed such that it can be installed in the exhaust pipe individually or several times in series (cascaded). As a result, the cleaning effect can be adapted flexibly to different requirements.Single module: For standard applications-e.g. in single-room firing systems in the residential sector-a single catalyst module is generally sufficient to fall below the legally required limit values for CO, VOC and fine dust. This module is inserted or screwed directly into the exhaust pipe.Multiple Arrangement / Cascade System: In more demanding applications, e.g., at higher emission loads or lower operating temperatures, the catalyst can be cascaded in multiple arrangements. The modules are installed in cascade axially within the exhaust pipe.• The following advantages result:• Increase in reaction time (residence time): The exhaust gases pass successively through several catalytic zones.• Optimization for different kinds of pollutants: it is possible to coat the modules differently, e.g. one more strongly on CO, the next on VOC or NOx.• Subsequent scalability: Plant operators can supplement an additional module if necessary without changing the overall system.• Better heat distribution: Several ceramic elements buffer temperature peaks and promote uniform catalytic activity.Mechanical embodiment: Each module is designed as an independent cartridge with a standard diameter (e.g. 130 mm) and can be connected to further modules by means of a bayonet, plug-in or screw connection. Mechanical guide rings or threads ensure that the modules can be arranged one behind the other in a positive and non-positive manner. Temperature resistant sealing tapes, ceramic fiber mats or conical press fit systems can be used to seal between the modules. The internal diameter of the exhaust pipe is almost completely maintained by the modular design, which does not impair the traction and the exhaust gas guidance.Variants: The modular system can also be combined with different lengths of the ceramic elements (e.g. 50 mm, 100 mm, 150 mm). The installation can thus be adapted flexibly to the existing pipe profile and the emission requirements. The subsequent exchange of individual modules with a specific catalyst coating (e.g. during fuel exchange) is also provided.Summary of the Cascade Principle:• The invention enables a cascading embodiment of the invention:• Individual adaptation of the cleaning performance to emission load and plant performance• Subsequent extensibility, for example at more stringent emission limit values• Segmented maintenance where only loaded modules need to be replaced• Flexibility when using different catalysts in seriesNatural draw opening / bypass flow path: A further constituent of the invention is an optionally integratable natural draw opening which serves as a bypass-like relief device. This function contributes in particular to operational reliability, flow stability and to the avoidance of back pressure effects in the exhaust pipe.Function of the natural draw opening: The natural draw opening is a noncatalytically treated partial region or a defined bypass channel inside or laterally next to the catalyst module, through which a partial stream of the exhaust gas is guided unfiltered and without appreciable flow resistance.This bypass is effective in particular when:• The operating temperature of the furnace is not yet high enough for a catalytic reaction (e.g. in the heating phase),• the catalyst module is clogged, added or iced (e.g. by condensate formation in the case of moist fuel),• There is an increased demand for traction (e.g. due to weather changes, wind pressure on the chimney),• or for relieving stress in the case of particularly high exhaust gas volume flows (for example when large amounts of fuel are being deposited).Construction and integration: The natural traction opening can be realized in various ways:• Lateral channel in the housing: An annular or semicircular opening in the module housing allows a parallel gas flow next to the ceramic body.• Longitudinal slots or bores at the edge region of the ceramic cartridge, through which a partial stream is conducted.• Pressure-dependent non-return flap (optional): A spring-loaded flap opens only when there is an increased differential pressure and acts as a safety valve.• Thermoactive control (optional): With increasing exhaust gas temperature, the bypass is closed (e.g. via a bimetallic element), so that the bypass is active only in the starting phase.Fluidic effect: The natural chimney flow is ensured by the natural chimney flow even when the resistance is increased by the catalyst element. The risk of a flue gas recirculation into the living space or of a waste gas poisoning is thereby significantly reduced. At the same time, the controlled bypass function assists the rapid heating of the ceramic element to catalytically active temperatures.Combination with cascade modules: The natural draw opening can also be integrated when using a plurality of catalyst modules in cascade. The bypass can be:• may be present only in the first module (e.g. for starting phase),• may be provided in each module (e.g. for load distribution),• or in a separate intermediate module (e.g. with active flap control).Advantages of the natural draft opening:• Ensuring functionality even in the event of faults• Avoidance of Pressure Build-up or Build-up Heat• Assistance in heating operations• Increase of operating safety by passive overload protection• Reduction of the fouling tendency of the catalyst in poor combustionOverall system description - FurnaceKAT with cascade and natural train opening: The invention represents a modular catalytic converter system for exhaust systems which consists of at least one ceramic catalytic converter element and can be expanded by a plurality of modules in cascade if required. The system is supplemented by an integrated natural traction opening, which functions as a bypass-like safety component.Modular Construction: Each catalyst module comprises:• an open-pored, high-temperature-resistant ceramic element preferably made of SiC and / or Al 2 O 3,• a catalytically active coating of platinum, palladium, rhodium or combinations thereof,• a modular frame for mechanical reception and guidance,• a heat- and corrosion-resistant housing (e.g. made of stainless steel),• and optionally a bypass structure or natural traction opening.The modules can be used individually or in series in series. The properties can be adapted by targeted combination and selection of the catalyst coatings (e.g. CO modulus+ VO modulus).Natural flue opening-safety and start-up aid: The natural flue opening is designed to support the natural flue train, in particular in operating phases with low exhaust gas temperatures or increased flow dynamics. It is designed fluidically such that:• In the cold state or at high counterpressure, a portion of the exhaust gases is conducted past the catalytic converter,• Automatically or passively closing on reaching the catalytically active temperatures (e.g. >250 ° C.),• or permanently functioning as a partial flow bypass, e.g. in installations with a high exhaust gas volume.• This function is particularly useful in the starting phase of burn-up when the ceramic element has not yet reached the necessary activation temperature.Flexible design for different applications: The invention can be used in different configurations:• Single module without bypass for simple applications with well controlled combustion,• Single module with natural draw opening for furnaces with varying fuels or poor draw characteristics,• Multi-module cascade without bypass for constant high temperature installations,• Cascade with selective bypass in one or more modules to achieve selective exhaust gas routing.Integration into existing systems: Thanks to the standard diameters (e.g. 120, 130 or 150 mm) and the standardized pipe geometries, the system can be retrofitted for existing furnace systems. It can be installed both horizontally and vertically and is suitable for:• Single-chamber firing installations,• warm air tile ovens,• Workshop heaters,• Agricultural small-firing installations,• Mobile firing devices,• Exhaust Systems and / or Exhaust SystemsAdvantages in overview: modular construction: adaptable to emission requirements and space conditions• Highly effective emission reduction for dust, CO, VOC and NOx• Cascadeability for stepwise increase in performance or targeted reaction• Natural traction opening to avoid back pressure, traction problems and starting difficulties• Mechanically robust, low-maintenance, passively functioning• No energy supply necessary - purely thermal and flow controlled• Retrofittable and replaceable without changing the firing site itselfFrom the viewpoint and variants: Future variants of the invention could also be found:• temperature sensors,• intelligent flap controls,• or automatic bypass control by means of bimetallic elements.It is also conceivable for the catalytic converter unit to be operated in combination with a fine dust electrostatic filter.Installation in bent, kinked or special tube guides: An important advantage of the furnace KAT system according to the invention is that it is suitable not only for straight tube segments but also for tube bends, bends, angle pieces or compact tube guides. Many furnace installations do not have straight flue gas lines, but rather curved or angled transitions, in particular in the region between furnace and chimney connection.Adaptation to bent tube profiles: The catalytic converter modules are designed such that they:• can be integrated into slightly angled furnace tubes (e.g. 15°, 30°, 45° or 90°),• either axially installed or distributed over modular spacers, also segmented around the bend,• optionally also in remote flow directions (e.g. T-pieces, S-arches, wall passages),• Flexible seals or segmented construction can be adapted to different flow directions.Commercial sizes and tube standards: The catalyst system is compatible with all commercial furnace tube sizes used in the German and European market. These include in particular diameters of:• 100 mm,• 120 mm,• 130 mm,• 150 mm,• 160 mm,• 180 mm,• 200 mm,• and special sizes in the industrial or industrial sector.Both round and oval cross sections can be fitted with matching module housings. Furthermore, integration into double-walled systems or insulated exhaust gas conduits is also possible.Flexible module design: For bent tube profiles, special module variants can be used with:• segmented ceramic element,• bent housing,• or multi-part installation concept.In such embodiments, it is also possible to integrate the bypass function in a targeted manner in the arc region, since it is often possible to expect here changed flow dynamics and locally increased tendency to deposit.Summary of Adaptability: The invention features its high compatibility with existing kiln systems, independent of:• Tube geometry (straight, curved, angled),• Tube diameter (all commercial sizes),• Flow direction (horizontal, vertical, diagonal),• Material design (stainless steel, steel, ceramic tube).As a result, the catalyst system is ideally suitable for retrofitting, but also for integration into new plant concepts in which emissions reduction is already provided in a constructional manner.Pipe geometry and connection possibilities: The catalyst module according to the invention is designed such that it can be integrated directly into the exhaust system between furnace and chimney. For this purpose, the FurnaceKAT module has a standardized tube geometry which is compatible with furnace tubes customary on the market.Tapering or widening at the pipe ends: In order to ensure compatibility with different pipe diameters, the pipe ends of the module can either:• tapered (reduced) to plug into a superordinate pipe piece (e.g. transition from 150 mm to 130 mm),• or widened to serve as a sleeve for the insertion of a smaller piece of pipe.• This shape enables the form-fitting and tight connection to existing exhaust pipes.Open pipe ends for passage and connection: The catalyst module is designed to be open both on the top side and on the bottom side. This enables:• the axial flow of the exhaust gases from bottom to top through the ceramic element,• The series connection with further tube segments, for example curved pieces, wall feedthroughs or further cleaning stages,• and the possibility of central placement in the exhaust system without additional openings or bypass lines being necessary.Placement on the connection piece of the firing system: The module is provided in particular for installation directly on the connection piece of the firing station, that is to say at the outlet of the combustion chamber. The advantages of this positioning are:• Maximum exhaust gas temperature immediately after combustion, enabling rapid activation of the catalytic action,• reduced condensate formation due to high thermal environment,• fewer deposits, since particles are reacted better in the high temperature range,• and a compact system construction which allows retrofitting even in the case of restricted space conditions.Mechanical connection: The integration can be effected by: 1. inserting between two pipe sections, 2. inserting into a sleeve section, 3. or inserting into a T-section or angle pipe if a lateral revision is necessary.Variants and areas of application: The open and flexible design makes the FurnaceKAT system usable for:• chimney furnaces,• Tiling furnaces with warm air system,• pellet furnaces,• Wood heaters with furnace tube connection,• and agricultural and mobile firing installations

Claims

Catalytic converter (2) (furnace KAT) for reducing dust and gaseous pollutant emissions in exhaust gas systems of combustion systems, in particular chimney, tile and workshop furnaces, characterized in that the catalytic converter comprises an open-pored, ceramic element which is arranged in a module frame within a module housing, wherein the ceramic element preferably consists of silicon carbide (SiC), aluminium oxide (Al 2 O 3) 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.Catalyst (2) according to Claim 1, characterized in that the ceramic element is designed as foam ceramic with an open cell structure.Catalyst (2) according to one of the preceding claims, characterized in that the catalytic coating is applied by impregnation, sol-gel processes or a comparable surface treatment.Catalytic converter (2) according to one of the preceding claims, characterized in that the module housing is designed for integration into a smoke tube (1) or exhaust tube with a standard diameter (preferably e.g. 120 mm, 130 mm, 150 mm or greater).Catalyst (2) according to any one of the preceding claims, characterized in that a plurality of catalyst modules can be arranged axially one behind the other in cascade, each module having a separate ceramic element.Catalytic converter (2) according to claim 5, characterised in that the cascade modules are mechanically connected via plug-in, screw-on or bayonet connections.Catalytic converter (2) according to one of the preceding claims, characterized in that a natural extraction opening is provided, which forms a bypass duct for exhaust gases in order to reduce the flow resistance in specific operating states.Catalytic converter (2) according to claim 7, characterised in that the bypass is formed as a lateral channel, a longitudinally extending opening or a temperature-controlled flap opening.Catalytic converter (2) according to one of the preceding claims, characterized in that the natural traction opening is activated at low temperatures or high differential pressure and is closed by temperature rise during normal operation.Catalytic converter (2) according to one of the preceding claims, characterized in that the system is operated without an external energy supply and functions exclusively by the natural train of the firing installation.Catalytic converter (2) according to one of the preceding claims, characterized in that the bypass duct is provided with a control which acts as a function of temperature and closes the bypass when a defined exhaust gas temperature is reached, preferably by means of a bimetallic element.Catalyst (2) according to one of the preceding claims, characterized in that the cascade modules are catalytically coated differently in order to convert different pollutants in a targeted manner in a plurality of reaction stages.Catalyst (2) according to one of the preceding claims, characterized in that the catalyst modules are designed to be replaceable, in particular as replaceable cartridges having a defined diameter and graduations in length.Catalytic converter (2) according to one of the preceding claims, characterized in that the ceramic element is secured by a support grid or a protective cage against mechanical damage or soot strike in the exhaust gas stream.Catalyst (2) according to any one of the preceding claims, characterized in that the module casing is thermally insulated or provided with a heat protection sleeve in order to ensure a stable operating temperature range in the interior.A catalyst (2) according to any preceding claim, characterised in that the system can be installed both vertically and horizontally in exhaust pipes.Catalyst (2) according to any of the preceding claims, characterized in that the ceramic support material has a specific surface area of at least 0.001 - 10,000 m 2 / m 3 in order to allow a high catalytic conversion rate.Catalytic converter (2) according to one of the preceding claims, characterized in that the system is provided as a retrofit module for existing ovens, in particular by inserting or screwing into the existing smoke tube (1) without structural changes.Catalyst (2) according to one of the preceding claims, characterized in that the ceramic element is inserted interchangeably into the module frame and can be fixed by means of a bayonet or screw connection.Catalytic converter (2) according to one of the preceding claims, characterized in that the system is suitable for use in individual-room firing stations, agricultural firing systems, workshop heaters or mobile heating apparatuses.Catalytic converter (2) according to one of the preceding claims, characterized in that the module housing is designed to be accommodated in kinked, bent or angled exhaust pipe profiles, in particular in pipe bends with angle degrees of 15° to 90°.Catalyst (2) according to claim 21, characterized in that the ceramic element is segmented or made in several sections to adapt to the curved pipe guide.Catalytic converter (2) according to one of the preceding claims, characterized in that the system is provided for installation in exhaust pipes with all commercially available cross sections and diameters, in particular with round or oval profiles in the sizes 100 mm to 200 mm.Catalyst (2) according to one of the preceding claims, characterized in that the module can be integrated into both single-wall and double-wall exhaust pipes.Catalytic converter (2) according to one of the preceding claims, characterized in that the system can be retrofitted without changing the existing furnace or chimney system, in particular by inserting, screwing or inserting it into existing pipe systems (1), including those with bends or bends.Catalytic converter (2) according to one of the preceding claims, characterized in that the system preferably comprises a European commercial exhaust pipe (1) and / or smoke pipe (1) according to standards.Catalyst (2) according to one of the preceding claims, characterized in that the catalyst tube has a taper or a widening at one end or at both ends in order to enable a positive connection (4 / 5) to connection tubes of different nominal width.Catalyst (2) according to one of the preceding claims, characterized in that the tube bottom side (5) and tube top side (4) are designed to be open in order to enable simple integration into an existing smoke tube system by axial connection of further tube segments.Catalyst (2) according to one of the preceding claims, characterized in that the catalyst system is installed directly in the connection (4 / 5) to the connection piece of the firing installation, preferably directly after the exhaust gas has discharged from the furnace or chimney insert.Catalyst (2) according to one of the preceding claims, characterized in that the housing shape of the FurnaceKAT module is cylindrical or conical and can be inserted with an exact fit into commercially available smoke tubes (1) with standard diameters (e.g. 120 mm, 130 mm, 150 mm).Catalyst (2) according to any one of the preceding claims, characterized in that the FurnaceKAT module has a depth of insertion of less than 50 mm into the smoke tube, whereby the tension is not substantially impaired and simple assembly is possible.Catalytic converter (2) according to one of the preceding claims, characterized in that the housing of the catalytic converter module is provided with positively locking latching lugs, sockets or clamping rings, which enable tool-free fastening between two furnace tube segments.Catalyst (2) according to one of the preceding claims, characterized in that the shape of the ceramic catalyst element is selected such that it is situated in a fluidically centred manner in the tube (1) and the exhaust gases are guided completely through the open-pore material.

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