DE102019008612A1 - Fine dust separation device for small combustion systems - Google Patents

Abstract

The present invention relates to a device for filtering fine dust, in particular for small solid fuel firing systems, with a suction unit (30) comprising a connection pipe (32) for connecting the suction unit (30) to a flue gas path (10), from which a flue gas from a furnace (04) flows, and - a suction opening (34), and a filter unit (60) comprising - an inlet opening (66) connected to the suction opening (34) by means of a first connection unit (38), - an outlet opening (68), - a between the inlet opening (66) and the outlet opening (68) arranged filter element (50), and preferably - a fan (65) arranged between the outlet opening (68) and the filter element (50), which is set up to generate a suction pressure, wherein the suction unit (30) and the filter unit (60) are arranged spatially separated from one another as separate assemblies and flow-related by means of connection units or means (38, 48) h are interconnected or connectable.

Description

The present invention relates to a device for filtering fine dust, in particular for small solid fuel combustion systems.

Particulate matter emissions from small-scale combustion systems such as single-room burners, chimneys, stoves and smaller boilers have been the subject of intense public debate due to their health hazards. Both at the federal level and partly at the municipal level, regulations have been put into effect that contain limit values for dust emissions from small combustion systems.

For example, the legal situation in Germany from 2015 onwards for new firing systems requires dust emissions for small firing systems to be reduced to 20 mg / m ³ flue gas and for single ^{room firing to 40 mg / m 3} flue gas, in accordance with the first Federal Immission Control Ordinance (1st BlmSchV), are to be limited. Different transition periods apply to existing furnaces, depending on their age.

The major part, i.e. 80 - 95% of the mass, of the fine dust has a particle size of significantly less than one micrometer. Therefore, from a technical point of view, only electrostatic separation and filtration come into consideration for separating these small particles, which have degrees of separation in the submicrometer range of around 95% for electrostatic separators and over 99.5% for filtering separators [source: Fritz, W .; Kern, H .: Cleaning of exhaust gases, 3rd edition, 1992, Vogel Buchverlag].

It is known that various systems for dust separation for small combustion systems are available on the market, which can be retrofitted to existing systems. These are mostly electrostatic precipitators, which are also known as E-filters.

With such E-filters, an electrostatic field is generated in the gas flow to be cleaned via a high-voltage generator and a so-called spray electrode with a negative charge, in which dust particles are electrostatically charged. Due to the electrostatic field forces, the negatively charged dust particles move to a positively or neutrally charged so-called precipitation electrode, where they are removed from the gas flow by adhesion. The E-Filters available on the market have a concentric structure with a central spray electrode and use of an exhaust pipe as a collecting electrode. Due to this geometry, the free flow cross-section decreases with increasing operating time due to the separation of fine dust from the gas flow and its accumulation on the walls of the flue gas duct. This increases the flow resistance of the flue gas, so that maintenance in the form of manual cleaning, for example by the chimney sweep, is necessary.

Furthermore, from the DE 10 2008 059 432 a flue gas cleaning device is known, which is to be arranged in an exhaust duct and uses ceramic exhaust filters that are to be cleaned by reversing the flow. It should be noted, however, that the amount of dust to be separated per heating period (i.e. the difference between the limit value and the raw gas dust concentration) is generally rather low in conventional firing systems with a low thermal output such as fireplace stoves or pellet boilers, as it is usually less than 1 kg per heating period. In the case of furnaces with a higher thermal output such as log and wood chip boilers with, for example, 30 to 50 kW, significantly higher amounts of dust can be achieved with up to 20 kg.

The known filter techniques are technically complex and also prone to errors due to the automated cleaning of the filters used. The separation of condensing tars, which takes place parallel to the separation of dust, significantly increases the amount of pollution that is actually separated. However, this side effect of dust separation, which is positive for environmental and health protection reasons, leads to a reduction in the service life of the filter materials used, which are significantly more stressed by the larger quantities separated.

Against this background, it is the object of the invention to provide a device for dust separation which is robust in its operating properties and insensitive to malfunctions and incorrect operation, as well as having a sufficiently long service life without further maintenance.

• - ein Anschlussrohr zur Verbindung der Absaugeinheit mit einem Rauchgasweg, aus welchem von einer Feuerung ein Rauchgas strömt, und
• - eine Absaugöffnung, und einer Filtereinheit umfassend
• - eine mit der Absaugöffnung mittels einer ersten Verbindungseinheit verbundene Eintrittsöffnung,
• - eine Austrittsöffnung,
• - ein zwischen der Eintrittsöffnung und der Austrittsöffnung angeordnetes Filterelement, und vorzugsweise
• - einen zwischen der Austrittsöffnung und dem Filterelement angeordneten Lüfter, welcher dazu eingerichtet ist, einen Ansaugdruck zu erzeugen,

wobei die Absaugeinheit und die Filtereinheit als separate Baugruppen räumlich voneinander getrennt angeordnet und mittels Verbindungseinheiten bzw. -mitteln strömungstechnisch miteinander verbunden bzw. verbindbar sind, vorgeschlagen.To solve this problem, a device for filtering fine dust, in particular for solid fuel small combustion systems, is provided
comprising a suction unit

• - A connection pipe for connecting the suction unit to a flue gas path from which a flue gas flows from a furnace, and
• - A suction opening, and comprising a filter unit
• - an inlet opening connected to the suction opening by means of a first connection unit,
• - an outlet opening,
• - a filter element arranged between the inlet opening and the outlet opening, and preferably
• - A fan arranged between the outlet opening and the filter element, which is set up to generate a suction pressure,

the suction unit and the filter unit being arranged spatially separated from one another as separate assemblies and being fluidically connected or connectable to one another by means of connecting units or means.

• - eine mit der Austrittsöffnung mittels einer zweiten Verbindungseinheit verbundene Rezirkulationsöffnung, und
• - ein Leitblech, welches dazu eingerichtet ist, eine Mischung eines aus der Austrittsöffnung strömenden Reingases mit dem Rauchgas zu veranlassen,

An advantageous embodiment of the invention also provides a recirculation unit connected to the suction unit, comprising

• a recirculation opening connected to the outlet opening by means of a second connection unit, and
• - a baffle which is set up to cause a mixture of a clean gas flowing out of the outlet opening with the flue gas,

According to the invention, in view of the comparatively small amounts of dust, the use of depth filters or storage filters is initially proposed as a simple, inexpensive and robust alternative to filters that are to be cleaned automatically.

Such storage or depth filtration is known, for example, from the field of cleaning provided breathing gases, for example in the field of air conditioning or ventilation technology. In the particle size range of fine dust from small combustion systems, filtering separators have an approximately 5% better separation efficiency compared to electrostatic separators [source: Fritz, W .; Kern, H .: Cleaning of exhaust gases, 3rd edition, 1992, Vogel Buchverlag]. According to the invention, a solution is therefore proposed which achieves both robust and reliable storage filtration and also allows the filter system to operate in a fail-safe manner.

According to the invention, the flue gas cleaning device is both for connection to chimneys of small solid fuel systems, i.e. at the end of a flue gas path without a flue gas cleaning device, as well as for integration into the flue gas path of a small combustion system particularly suitable for solids. The flue gas from a combustion system is introduced into the cleaning device implemented by the device according to the invention, cleaned there and ultimately released into the environment.

The flue gas cleaning device according to the invention has at least two spatially separated assemblies with the suction unit and the filter unit, which are connected to one another by at least one connecting element, which is designed, for example, as an insulated metal hose and sealed off from the environment. To simplify the connection of these insulated metal hoses to the suction and filter unit and the recirculation unit, quick-release locking systems such as bayonet locks, fire brigade couplings, Kamlock couplings or similar connections can advantageously be used.

To overcome the operationally necessary differential pressure of the filter unit, a fan is used, which is preferably designed as a radial fan. The fan is preferably located in the housing of the filter unit. The housing of the filter unit preferably consists of so-called sandwich panels, in which an approximately 30 to 50 millimeter thick core made of thermally insulating mineral wool is enclosed by galvanized sheet metal. This type of construction is mechanically stable, weatherproof and advantageously prevents the loss of condensate due to excessive cooling of the flue gas.

The solutions according to the invention are primarily to be used, in accordance with the legal requirements of the 1st BlmSchV, for separating fine dust from the exhaust gas from small solid fuel systems. It has surprisingly been found that, together with the fine dust, condensate components such as tars are also deposited, since the temperatures prevailing in the device according to the invention are below the condensation points of the tars of approximately 400 degrees Celsius. This mixture of dust and tar is also referred to below as the pollution load.

According to a preferred embodiment, it is provided that the free flow cross section of the first connection unit and / or the second connection unit is smaller than the free flow cross section of the connection pipe of the suction unit to the flue gas path. By using these smaller cross-sections, the connecting elements can be made considerably more material and space-saving and easier to assemble. For example, the diameter of the connecting pipe in many chimneys is in practice in a range from about 130 mm to 150 mm. The inside diameters of the connecting elements can advantageously be made in sizes DN 100, DN 80, DN 65, DN 50 or even smaller. The advantages with regard to the use of materials and manageability are given in particular with a double line routing and with an additional insulating layer in each case.

It is also advantageously provided that the suction opening is provided along a pipe circumference of the suction unit and / or that the recirculation opening is provided along a pipe circumference of the recirculation unit. This has the advantage that the largest possible amount of flue gas to be cleaned can be fed to the filter unit and, after cleaning, can be fed back to the recirculation unit.

A temperature sensor arranged in the lower region of the suction opening or below the suction unit is preferably provided, which is advantageously set up to activate the fan when a predefined temperature of the flue gas is exceeded. This avoids unnecessary fan operation. If the maximum permissible operating temperature is exceeded on the flue gas side, in particular for the filter elements, the fan can advantageously be switched off in order to effectively prevent inadmissible overheating of the filter unit. In this case, the flue gas would briefly be discharged unfiltered into the atmosphere.

According to a preferred embodiment, the device has a unit for electrostatic pre-agglomeration, which has a spray electrode around which a high-voltage field is formed, an insulator connected to the spray electrode, which prevents the high voltage from flashing over to surrounding components, and one with the insulator by means of a high-voltage cable includes connected high voltage source. A further or further improvement of this effect can advantageously be achieved by introducing a large-area precipitation grid, which is advantageously arranged on the inflow side in front of the filter elements. By providing an electrostatic pre-agglomeration, the service life of the filter materials can be increased, since the filters are significantly less stressed by a few agglomerated large particles, which tend to form a porous layer on the inflow side on the filter elements, than by many very small particles that penetrate into the depths penetrate the filter material.

A non-regenerable depth filter is preferably provided as the filter element, which is set up to separate fine dust, condensate and / or condensate constituents. In the particle size range of fine dust from small combustion systems, such a depth filter offers a significantly better ratio of separation performance and service life than other types of filter.

The filter element advantageously comprises a filter according to filter class G4, M5, M6, F7 or F8 DIN EN 779 (2012) .

According to a preferred embodiment, a pre-filter according to filter class M5 or M6 and a fine filter according to filter class F7 or F8 are provided as the filter element, with a separating layer being provided between the pre-filter and the fine filter, which preferably consists of a coarse-pored material, in particular to prevent adhesions to prevent the boundary layer between the filter elements. Such an arrangement achieves multi-stage filtering, which leads to a high degree of cleaning of the flue gas.

Alternatively, a series connection of a separately arranged prefilter and a separately arranged fine filter can advantageously be provided as the filter element, the prefilter and the fine filter being spatially separated from one another by means of at least one partition. Among other things, this has the advantage that the respective filter can be replaced more easily.

The filter unit preferably has an additional filter element for the start of operation, which is connected downstream of the filter element. In particular when the device is operated with fresh or new fine dust filters, such an additional filter element can reliably clean the flue gas.

According to a further advantageous embodiment, a silencer and a switchover unit are also provided in the filter unit, the switchover unit serving and advantageously being set up to guide the flue gas through the additional filter element during operation with fresh filters until the pressure loss over the additional Filter element has reached a specified pressure drop. As an alternative and / or in addition to the control via the pressure loss, the switchover unit can advantageously also switch after a predetermined operating time in such a way that the additional filter is bypassed or bypassed. By this point in time, the fresh filter elements are usually so heavily loaded that they achieve a sufficiently high cleaning effect. The material of the additional filter can advantageously consist of a pack of mineral wool or wool, cotton or linen. This material is not regenerated and is exchanged when the filter elements are changed and preferably disposed of thermally. According to the invention, however, it can also be provided that the gas passes through the additional filter element and the silencer in parallel or both the additional filter element and the silencer.

The suction unit preferably has a conical shape that widens downwards. This has the advantage that it occurs over time Dust deposits can be better avoided.

According to a further preferred embodiment, the filter unit further comprises a desulfurization device.

The filter unit preferably further comprises a shaping element which is set up to counteract a collapse of filter elements, in particular when the device is operated with low volume flows. Such a shaping element can be provided in the interior of filter pockets or as a metallic separating layer between a prefilter and a fine filter. Since the filter elements can be prevented from collapsing in this way, the effective filter surface and thus the service life are advantageously increased. Furthermore, the maintenance effort of the device is considerably reduced.

A special feature of the present invention is the structural separation of the part located in the axis of the flue gas flow, consisting of suction unit, recirculation unit and electrostatic pre-agglomeration, and the filter unit.

This construction according to the invention advantageously completely eliminates the separately constructed bypass space, which is required for safety reasons for unfiltered discharge of the flue gases to the atmosphere and which was previously required in other fine dust filter concepts.

The construction according to the invention advantageously ensures a safe and robust operation without the need for fault-prone flue gas flaps or other throttling devices. Due to the structural separation of the filter unit, considerably larger filter surfaces can be used than, for example, with fine dust filter constructions that are mounted directly on the chimney. In the case of such previously known constructions, the design dictates that they cannot significantly exceed the dimensions of the chimney and that they are also limited in height. With an average external cross-section of the chimney of 50 cm by 50 cm, a filter area of more than one square meter is hardly possible with such a previously known fine dust filter construction due to the geometry and the structural dimensions of 50 cm by 50 cm by 50 cm with a filter with a depth of about 20 mm to accommodate, especially if the required space for the bypass between the individual filter elements and the side chamber with fan etc. is removed. This results in a considerable limitation of the service life.

In contrast, the construction according to the invention does not have any comparable limitation of the filter area, so that a comparatively significantly longer service life can be achieved simply by increasing the filter area.

In the event of malfunctions, such as power failure or insufficient maintenance of the filter elements, in the solution according to the invention the flue gas follows the path in extension of the axis of the original flue gas path without fine dust filter, for example the chimney.

Advantageously, according to the invention, the flue gas is deflected from the axis of the original flue gas path by the negative pressure prevailing in the suction unit only in normal operation and fed to the filter unit via a connection unit.

The solution according to the invention consists of a part or a component, namely the suction unit, recirculation unit and electrostatic pre-agglomeration located in the axis of the flue gas flow, which should only be serviced by specialist staff during practical operation. In particular, electrostatic pre-agglomeration is a source of danger due to the high voltage that precludes maintenance by laypeople. Due to the close proximity to the spray electrode and the high-voltage cable, laypeople should also refrain from servicing the suction unit and the recirculation unit. In a large number of houses, the chimney is in inaccessible places on the roof, so that there is an increased risk of falling when inspecting it. This risk of falling can be reduced to almost zero through the use of trained specialists with appropriate safety belts, etc.

In the solution according to the invention, the components located in the axis of the original flue gas path should only be serviced by trained specialist personnel with the appropriate safety precautions.

In comparison, the filter unit of the solution according to the invention is a comparatively simple component. If the filter unit according to the invention is set up on an easily accessible flat roof, the filter elements could in this respect also be changed by laypeople. Even with pitched roofs, there are components such as steps for chimney sweeps, railings, insert components to retrofit balconies, for example, so that, at least in theory, it is also possible for laypersons to visit without danger. In this respect, the filter unit according to the invention can, under favorable circumstances, also be serviced by laypeople. Otherwise, an exchange of the invention Filter elements are carried out exclusively by specialist companies or specialist personnel.

Further details, features and advantages of the invention are explained in more detail below with reference to the embodiments shown in the figures of the drawings.

• 1 ein Ausführungsbeispiel der Vorrichtung zur Filterung von Feinstaub, insbesondere Darstellung der Hauptkomponenten Kamin (10), Absaugeinheit (30), Filtereinheit (60), Rezirkulationseinheit (40), Verbindungseinheiten (38, 48), elektrostatischer Voragglomeration (20) und Regenschutz (16);
• 2 ein weiteres Ausführungsbeispiel der erfindungsgemäßen Vorrichtung, insbesondere mit Fluidwegen, vorliegend bei einer Auf-Dachmontage mit Rezirkulation;
• 3 ein weiteres Ausführungsbeispiel der erfindungsgemäßen Vorrichtung in Teil-Explosionsdarstellung der Baugruppen;
• 4 ein Ausführungsbeispiel der Absaugeinheit und der Rezirkulationseinheit, vorliegend Ausführung mit Rezirkulation und Montageart im Rauchrohr, beispielsweise zur Anwendung bei nachträglich installierten isolierten Rauchgasleitungen an den Außenseiten von Häusern;
• 5 ein weiteres Ausführungsbeispiel der erfindungsgemäßen Vorrichtung, insbesondere mit Fluidwegen, vorliegend bei einer Auf-Dach-Montage, insbesondere mit Rohgasverdünnung mit rezirkuliertem warmem Reingas;
• 6 ein Ausführungsbeispiel der Absaugeinheit, insbesondere mit Fluidwegen, vorliegend bei einer Auf-Dach-Montage, insbesondere Rohgasverdünnung mit kalter Umgebungsluft;
• 7 ein Ausführungsbeispiel eines Rauchgasaustritts in die Atmosphäre bei einem Kamin ohne Absaugeinheit und ohne Rezirkulationseinheit;
• 8 ein Ausführungsbeispiel eines Rauchgasaustritts in die Atmosphäre bei einem Kamin mit Absaugeinheit und ohne Rezirkulationseinheit, beispielsweise für Betriebsstörungen wie Stromausfall oder mangelnde Filterwartung;
• 9 ein Ausführungsbeispiel eines Rauchgasaustritts in die Atmosphäre bei einem Kamin mit Absaugeinheit und mit Rezirkulationseinheit, beispielsweise für Betriebsstörungen wie Stromausfall oder mangelnde Filterwartung;
• 10 ein erstes Ausführungsbeispiel einer Filtereinheit in seitlicher Schnittdarstellung mit Gehäuse (62), Wartungsdeckel (64), Filterelement (50), Ventilator (65), Rohgaseintritt (66) und Reingasaustritt (68);
• 11 ein zweites Ausführungsbeispiel einer Filtereinheit, ähnlich 10, jedoch mit Seitenkammer (67), u.a. zur Rauchgasführung, und in Kombination mit elektrostatischer Voragglomeration einsetzbarem Niederschlagsgitter (29);
• 12 ein drittes Ausführungsbeispiel einer Filtereinheit, vorliegend mit durch Trennwände (70) erzielter Reihenschaltung von Vorfilter (52) und Feinfilter (56), welche optional auch als hier nicht dargestellte Parallelschaltung von mindestens zwei gleichartigen Filterelementen (50) zur Erhöhung der Filterfläche und damit der Standzeiten sowie für den Einsatz bei größeren Feuerungen mit größeren Rauchgasvolumenströmen vorgesehen sein kann;
• 13 ein Ausführungsbeispiel eines Zusatzfilters (78) mit Umschalteinheit (76) und/oder Schalldämpfers (72);
• 14 ein Ausführungsbeispiel eines Filterelements mit Vorfilter (52), Feinfilter (56) und Trennschicht (54);
• 15 ein Ausführungsbeispiel einer Filtereinheit umfassend eine Entschwefelungsvorrichtung, insbesondere in verschiedenen Varianten;
• 16 ein erstes Ausführungsbeispiel der Vorrichtung zur Filterung von Feinstaub mit entsprechenden Temperaturmessstellen mit Rezirkulationseinheit;
• 17 ein zweites Ausführungsbeispiel der Vorrichtung zur Filterung von Feinstaub mit entsprechenden Temperaturmessstellen ohne Rezirkulationseinheit;;
• 18 ein erstes Ausführungsbeispiel eines Formgebungselements (58) innerhalb einer Filterelements (50), bestehend aus Vorfilter (52), Trennschicht (54) und Feinfilter (56), hier Darstellung im Längsschnitt durch eine Filtertasche;
• 19 ein zweites Ausführungsbeispiel eines Formgebungselements (58) innerhalb einer Filtereinheit als Darstellung im Querschnitt durch mehrere nebeneinander befindliche Filtertaschen eines Filterelements (50), bestehend aus Vorfilter (52), Trennschicht (54) und Feinfilter (56); und
• 20 ein Ausführungsbeispiel für eine zusätzliche Temperaturerhöhung bzw. -verringerung des Rauchgases sowie eine weitere einfache Variante der Befestigung eines der Verbindungselemente (38, 48).

Show:

• 1 an embodiment of the device for filtering fine dust, in particular representation of the main components of the chimney ( 10 ), Suction unit ( 30th ), Filter unit ( 60 ), Recirculation unit ( 40 ), Connection units ( 38 , 48 ), electrostatic pre-agglomeration ( 20th ) and rain protection ( 16 );
• 2 a further embodiment of the device according to the invention, in particular with fluid paths, in the present case in the case of an on-roof installation with recirculation;
• 3 a further embodiment of the device according to the invention in a partially exploded view of the assemblies;
• 4th an embodiment of the suction unit and the recirculation unit, in this case version with recirculation and type of installation in the flue pipe, for example for use in subsequently installed insulated flue gas pipes on the outside of houses;
• 5 a further exemplary embodiment of the device according to the invention, in particular with fluid paths, in the present case for on-roof installation, in particular with raw gas dilution with recirculated warm clean gas;
• 6th an embodiment of the suction unit, in particular with fluid paths, in the present case for on-roof installation, in particular raw gas dilution with cold ambient air;
• 7th an embodiment of a flue gas outlet into the atmosphere in a chimney without a suction unit and without a recirculation unit;
• 8th an embodiment of a flue gas outlet into the atmosphere in a chimney with a suction unit and without a recirculation unit, for example for operational malfunctions such as power failure or insufficient filter maintenance;
• 9 an embodiment of a flue gas outlet into the atmosphere in a chimney with a suction unit and with a recirculation unit, for example for malfunctions such as power failure or insufficient filter maintenance;
• 10 a first exemplary embodiment of a filter unit in a lateral sectional view with housing ( 62 ), Maintenance cover ( 64 ), Filter element ( 50 ), Fan ( 65 ), Raw gas inlet ( 66 ) and clean gas outlet ( 68 );
• 11 a second embodiment of a filter unit, similar 10 , but with side chamber ( 67 ), among other things for flue gas guidance, and in combination with electrostatic pre-agglomeration usable precipitation grid ( 29 );
• 12th a third embodiment of a filter unit, in this case with partition walls ( 70 ) achieved series connection of prefilter ( 52 ) and fine filter ( 56 ), which can optionally also be used as a parallel connection, not shown here, of at least two similar filter elements ( 50 ) can be provided to increase the filter area and thus the service life as well as for use in larger furnaces with larger flue gas volume flows;
• 13th an embodiment of an additional filter ( 78 ) with switching unit ( 76 ) and / or silencer ( 72 );
• 14th an embodiment of a filter element with pre-filter ( 52 ), Fine filter ( 56 ) and separating layer ( 54 );
• 15th an embodiment of a filter unit comprising a desulfurization device, in particular in different variants;
• 16 a first embodiment of the device for filtering fine dust with corresponding temperature measuring points with a recirculation unit;
• 17th a second embodiment of the device for filtering fine dust with corresponding temperature measuring points without a recirculation unit ;;
• 18th a first embodiment of a shaping element ( 58 ) within a filter element ( 50 ), consisting of a pre-filter ( 52 ), Interface ( 54 ) and fine filter ( 56 ), here representation in longitudinal section through a filter pocket;
• 19th a second embodiment of a shaping element ( 58 ) within a filter unit as a representation in cross section through several adjacent filter pockets of a filter element ( 50 ), consisting of a pre-filter ( 52 ), Interface ( 54 ) and fine filter ( 56 ); and
• 20th an embodiment for an additional temperature increase or decrease of the flue gas as well as another simple variant of the attachment of one of the connecting elements ( 38 , 48 ).

In 1 a general overview of a device for filtering fine dust is shown, which a suction unit 30th , a recirculation unit 40 , a filter unit 60 and an optionally provided device 20th includes for electrostatic pre-agglomeration. The suction unit 30th is the first assembly that goes into the flue gas path 10 is connected to the combustion system. The filter unit 60 as a second, via a connecting element 38 The connected assembly contains at least one filter element 50 , which is designed, for example, as a depth filter. To overcome the operationally necessary differential pressure of the filter unit 60 becomes a fan 65 used, which is preferably designed as a radial fan. The fan 65 is preferably located in the housing 62 the filter unit 60 . On the optionally provided device for clean gas recirculation via the connection unit 48 as well as the electrostatic pre-agglomeration will be discussed in more detail in the further course of the description.

The free flow cross-section of the suction unit 30th and / or the recirculation unit 40 is primarily based on the free flow cross-section of the combustion system itself, but can be used to a certain extent over defined long distances, for example through guide plates of the suction unit 30th and / or baffles 49 the recirculation unit 40 be narrowed. It is crucial that this narrowing does not have any significant negative effects on the operation of the combustion system. In particular, a constriction must not increase the flow resistance for the discharge of the flue gases to such an extent that flue gas 4th exits from the combustion system, for example into the surrounding living space. If such an unwanted leakage of smoke gas 4th can be excluded, a constriction of the flue gas path is permissible to a certain or limited extent.

The construction according to the invention ensures that when the flue gas cleaning device is inactive, for example in the event of malfunctions such as a power failure or the presence of clogged filters due to insufficient maintenance, the flue gas at the suction unit 30th can flow past and can be discharged uncleaned to the atmosphere. In the case of the malfunctions mentioned above, the negative pressure is necessary for the flue gases to be discharged from through the suction unit 30th via the connecting element or the connecting unit 38 towards the filter unit 60 either too low if the filters are clogged or not available in the event of a power failure.

2 shows, analogous to the general overview of 1 , a representation of the gas flows during the operation of the device, with dark arrows a raw gas 4th with a high fine dust content of, for example, 100 mg / m ³ _N and bright arrows a clean gas 8th label with a low fine dust content of 10 mg / m ³ _N , for example. The ambient air 2 with a fine dust content of, for example, 0 mg / m ³ _N , a mixture of raw gas 4th mixed with recirculated clean gas 8th is with the reference number 6th and has a fine dust content of 85 mg / m ³ _N, for example. That continues in 2 illustrated filter element 50 is designed here as a pocket filter and the fan 65 is designed, for example, as a centrifugal fan. If this radial fan, or also half-radial fan, is operated, a gas flow of flue gas is created by the negative pressure 4th , which through the suction opening 34 the suction unit 30th to storage filter arrangements, more precisely through the filter material in the filter unit. The flue gas 4th does not take the still free path along the axis of the flue gas path when the centrifugal fan is in operation 10 from the furnace, but - due to the pressure reduction in the suction unit 30th - the way through the filter unit 60 , whereby particles of the pollution load are separated. With this extraction of flue gas 4th A comparable volume is also achieved through the opening of the suction unit on the downstream side 30th withdrawn so that the filter assemblies from a mixture of flue gas 4th and recirculated clean gas 8th or ambient air 2 are flowed through. If the cleaning effect is reduced during the operation of the furnace, for example due to a failure of the fan 65 or the addition of the fiber material does not endanger the safe operation of the furnace at any time. Instead of going through the filter assemblies of the filter unit 60 to take, then takes the flue gas 4th the unfiltered path through the inner part of the recirculation unit towards the atmosphere. The outer part of the recirculation unit with the recirculation space 44 is not flowed through.

Because the centrifugal fan is behind the filter element 50 , so arranged in the clean gas path, this comes with dirt particles from the flue gas 4th less in contact, which leads to an increase in service life and a reduction in maintenance intensity. The filter elements are dependent on the level of contamination 50 to be replaced after a defined number of operating hours. It is preferably provided that the filter material consists of a synthetic fiber that is temperature-resistant up to 180 ° C., for example, and is designed as a depth filter in the form of a bag or as a bag filter in the form of a bag. Furthermore, designs in the form of filter bags or cassettes are possible.

Alternatively, artificial mineral fibers such as glass wool or mineral wool can also be used. One advantage of synthetic fibers is that they can be disposed of more easily via general waste incineration.

Alternatively, the filter elements can advantageously also be designed as ceramic filter filter elements.

Here is the clean gas outlet 68 (in 2 shown concealed; visible for example in 10 ) designed so that at least part of the clean gas 8th via the connection unit 49 and the recirculation unit 40 into one of the suction units 30th in the direction of flow of the flue gas 4th downstream area is directed. Through this - partial or complete - recirculation of cleaned, warm flue gas 8th , the mixing temperature of the in the suction unit 30th extracted gas 6th elevated. Instead of cold fresh air 2 is the flue gas coming from the furnace 4th with warm recirculated clean gas 8th mixed. The advantage of this increase in the mixed temperature of the gas fed to the filter unit is, in particular, the reduction in the accumulation of condensing moisture - in the form of water - from the exhaust gas.

A slight accumulation of condensate when heating up the furnace and starting the cold filter unit is part of normal operation. Excessive condensation of moisture should be avoided during continuous operation, as otherwise the accumulation of a lot of water on the one hand increases the weight of the filter unit and on the other hand the housing can be damaged by cracking ice if it is not in operation for a longer period of time. With suitable management, condensate that has already precipitated can advantageously be evaporated again, so that there is no steadily increasing amount of condensate. A moisture sensor can be used for additional security 61 Monitor the amount of condensate in the floor area. Above a permissible maximum value, the filter unit is advantageously taken out of operation and a maintenance notice can be sent or transmitted to the operator or the chimney sweep, for example via a cellular radio connection or the like.

In 3 is an overview of a suction unit 30th and a recirculation unit 40 which on a fireplace 10 are mounted, shown. Above the recirculation unit 40 is also a device 20th arranged for electrostatic pre-agglomeration, the spray electrode 22nd through suction unit 30th and recirculation unit 40 reaches through. The device is an optional assembly 20th provided for electrostatic pre-agglomeration, comprising at least one high voltage source 26th , a spray electrode 22nd , around which a high-voltage field is formed in the gas flow to be cleaned, and an insulator 24 which causes a flashover of the high voltage to the surrounding components such as the suction unit 30th and prevents the original smoke path. The high voltage source 26th is via appropriately suitable high-voltage cables 28 with the isolator 24 and the spray electrode 22nd connected. In addition, an in 11 shown grounded precipitation grid 29 Be arranged on the inflow side in front of the filter element in order to increase the effect of increasing the service life through pre-agglomeration.

Such a solution of dust separation, which has not yet been pursued for small firing systems, realizes a combination of components of electrostatic dust separation or electrostatic pre-agglomeration and filtration. The fine dust particles are initially exposed to an electrostatic field which is weaker than the electrostatic fields usually used for pure electrostatic fine dust separation. In this weakened electrostatic field there is a pre-agglomeration of many very small fine dust particles to form larger agglomerates. These larger agglomerates can be used in the subsequent filtration stage in the filter unit 60 are separated much more easily than small fine dust particles. In addition to improved cleaning performance, this also leads to a significant increase in the service life of the filter materials used, since the large agglomerates tend to form a porous dust coating on the inflow side than in the depths of the filter material 50 penetrate and thus lead to an increase in the pressure loss during operation. As the manufacturing cost for the high voltage generator 26th to generate the weakened electrostatic field are low, a good price-performance ratio can be achieved through the electrostatic pre-agglomeration. The electrostatic pre-agglomeration serves to increase the service life of the filter materials.

In 4th are, according to a further exemplary embodiment, the suction unit 30th and the recirculation unit 40 within an exhaust pipe or smoke pipe 12th mounted, for example inside an insulated stainless steel chimney for retrofitting on the outside of houses. Again, the respective gas flows are shown during the operation of the device, for the sake of clarity a representation of the device, which is optionally provided anyway, is shown 20th electrostatic pre-separation was dispensed with.

5 shows a representation of the gas flows within a suction unit 30th and a recirculation unit 40 during operation of the device. It can be seen or shown in particular that the mixture of a flue gas 4th with recirculated clean gas 8th to a diluted raw gas 6th leads.

6th relates to a representation of the gas flows within a suction unit 30th without the Recirculation unit 40 . It can be seen that the mixture of a flue gas 4th with false air 2 to a diluted raw gas 9 leads.

In 7th is from a chimney without an extraction unit 30th and without a recirculation unit 40 flue gas escaping into the atmosphere 4th shown, which has a high fine dust content of ^{100 mg / m 3} _{N, for example.}

8th shows like a flue gas stream 4th at a fireplace 10 with suction unit 30th in the event of a malfunction of the filter unit 60 , for example in the event of a power failure or lack of maintenance on the filters, escapes into the atmosphere, as the flue gas flow is not sucked in 4th through the filter unit 60 he follows.

9 relates to another representation in which a flue gas flow 4th at a fireplace 10 with suction unit 30th and with a recirculation unit 40 if the filter unit malfunctions 60 escapes into atmosphere.

In 10 is an embodiment of a filter unit 60 shown which a filter element 50 , a housing 62 , a maintenance cover 64 , a raw gas inlet 66 , a clean gas outlet 68 , a fan 65 as well as connecting elements designed as thermally insulated metal hose, for example 38 and 48 for raw and clean gas.

The filter elements 50 the filter unit 60 are preferably designed as so-called pocket filters. The design as a pocket filter is a simple, cost-effective design that has been tried and tested in ventilation technology, for example. An essential feature of pocket filters is that they often work according to the principle of depth filtration and, in contrast to surface filters, cannot be regenerated. Depth filters, also known as storage filters, are used, among other things, for lower volume flows and comparatively low dust / pollution loads, especially when the separated dust is not to be recovered as valuable material, as they store the dust etc. in the depth of the filter material, so that this cannot be returned, or only to a small extent [see: Löffler, Friedrich: Staubabscheiden, magazine / series: Textbook series of chemical engineering / process engineering, Thieme-Verlag, Stuttgart, 1988, ISBN: 3137122015].

In contrast to depth filters, surface filters are used for large dust / pollution loads and large volume flows, especially when the separated dust is to be recovered as valuable material. In the case of surface filters, the separation takes place on the filter surface, so that the dust separated on the surface can be thrown off by reversing the flow, for example.

When cleaning the exhaust gases from small solid fuel firing systems, the volume flows are comparatively low (with individual room firing well below 100 m ³ _N / h), with the dust content around 100 mg / m ³ _N and thus also low compared to many industrial applications. The separated dust should not be recovered as valuable material. Depth filters thus meet the requirements of the object according to the invention. A sufficient service life of the filter elements is decisive for the practical use of pocket depth filters for cleaning the exhaust gas from small solid fuel systems. Ideally, the service life of the filter elements is one year, so that the filter elements can be changed, for example by a chimney sweep, with annual cleaning even outside the heating season.

Typical market sizes of pocket filter elements in ventilation technology, which could also be used for cleaning the exhaust gas from small solid fuel firing systems, are frame dimensions of 598 mm x 598 mm with six to ten pockets and a pocket depth between 360 mm and 600 mm. Such a filter element with six pockets and a pocket ^{depth of 500 mm has a filter area of approximately 3.6 m 2} (0.598 m × 0.5 m × 6 pockets × 2 sides per pocket = 3.6 m ² ).

11 shows, according to a further embodiment, a filter unit 60 with a side chamber 67 , which for the gas supply and / or the sheltered accommodation of a fan 65 and / or a control unit is provided. Furthermore, a floor mat 63 is provided which serves to absorb condensate during the cold start-up phases and for later evaporation as the operating temperature increases and is designed, for example, as a mineral wool mat. At least one humidity sensor installed in the floor area 61 serves as additional security against excessive accumulation of condensate. If an impermissibly high level of condensate is detected, a warning can be sent to the operator or the chimney sweep, for example via a cellular network connection or the like, and the fan can be shut down to prevent further entry of condensate.

12th shows a further embodiment of a filter unit 60 with two filters connected in series, namely a pre-filter 52 and a fine filter 56 , as well as two between pre-filters 52 and fine filter 56 arranged partitions 70 . The pre-filter 52 cleans a raw gas diluted with recirculated clean gas 6th , for example with a Fine dust content of 85 mg / m ³ N. This results in a pre-cleaned raw gas 7th with a fine dust content of, for example, 50 mg / m ³ _N. After filtering through the fine filter 56 becomes a clean gas 8th obtained, which has a fine dust content of ^{10 mg / m 3} _{N, for example.} This increases the separation efficiency and increases the service life of the depth filter. Pre-filters function to separate the rather coarse pollutants, whereas fine filters, on the other hand, serve to clean the exhaust gas to the desired purity. According to EN 779 (2012), filter classes G4, M5 and M6 as pre-filters and F7 and F8 as fine filters have proven to be advantageous in practice.

In 13th is a filter unit 60 with a downstream silencer 72 , an additional filter 78 and a switching unit 76 shown. The additional filter 78 serves a company with fresh or newly inserted filter elements 50 in order to be able to filter out fine dust components that have not been filtered out. With fresh depth filters, the separation efficiency is initially lower, but increases significantly after some operating time. The additional filter 78 therefore serves according to the invention in particular to bridge a short-term lower deposition during such a running-in phase. The switching unit 76 directs a gas at the outlet of the fan towards the muffler 72 or additional filter 78 . The interconnection of additional filters 78 and muffler 72 both parallel and in 13th shown, as well as in series.

14th shows an embodiment of a multilayer fine dust filter 50 with a pre-filter 52 , a separating layer 54 and a fine filter 56 . The separation layer 54 prevents the two adjacent filter layers from “sticking together” and is designed, for example, as a coarse-fiber mat. The prefilter material corresponds to this variant of the series connection 52 and the fine filter material 56 in a filter element 50 installed. The advantage of this design is the more compact design, which in particular leads to smaller housings for the filter unit. In this type of filter element there is a separating layer 54 between the pre-filter 52 and the fine filter 56 required, since otherwise there will be sticking and blocking due to the separated pollution load at the boundary layer of the pre-filter 52 and fine filter 56 can come. In particular the pre-filter 52 facing upstream side of the fine filter 56 tends to stick together and block. This separating layer can consist of a material with large pores compared to the two adjacent filter materials. This can be, for example, a coarse filter material of filter classes G3 or G4. Another alternative, not shown, is a metallic design made of at least two layers of wire mesh, which can have a further spacer between them, such as a structure made of wire with a diameter that is thicker than the outer wire mesh. With a suitable design, this metallic spacer variant can also assume a supporting function and thus in particular additional shaping elements 58 replace.

15th shows a filter unit, for example for coal firing, with an additional device for desulfurization. According to a first variant, there is a desulfurization device upstream of the fine dust filter 80 provided, for example designed as a fixed bed made of lime. According to a second variant, there is a desulfurization device integrated into the filter unit 82 provided, for example designed as a layer of lime. According to a third variant, there is a desulfurization device downstream of the filter unit 84 provided, for example designed as a fixed bed made of lime. The fixed bed can be made of calcium hydroxide (slaked lime, Ca (OH) ₂ ), for example.

Lignite is predominantly used in small coal firing, the sulfur content of which can be estimated as the mean value of Rhenish and Lusatian lignite. With an annual throughput of two tons of lignite and an emissions-relevant share of 0.225%, this corresponds to emissions of 4.5 kg / a of pure sulfur or 9 kg of SO ₂ . A Ca (OH) ₂ molecule is required to separate a SO ₂ molecule, from which gypsum (CaSO ₄ ) is ultimately formed. Due to the molar masses of SO ₂ with 64 g / mol and Ca (OH) ₂ of 74 g / mol, there is an annual requirement of 10.5 kg Ca (OH) ₂ per year. Since this estimate is initially based on the assumption of ideal reaction conditions, ie a stoichiometric factor of 1.0, the real requirement is estimated at 10 to 40 kg Ca (OH) ₂ and an average of 25 kg Ca (OH) ₂ per year. This amount of Ca (OH) ₂ can be introduced into the flue gas flow both in fixed beds before and after the filter material. It is also conceivable to use this as a layer on the upstream side on the filter material for dust separation, between the filter materials for pre-cleaning and fine cleaning, or on the downstream side after the filter material for fine cleaning of the dust. With a bulk density of about 400 kg / m ³ for Ca (OH) ₂ , assuming a filter surface for dust separation of 5 m ^2, a layer thickness of 1.25 cm results. This layer thickness is in the order of magnitude of the depth filter materials for pre-separation and fine separation.

Preferably, the desulfurization with Ca (OH) _{2 takes place} in the temperature range around 140 ° C. These higher temperatures are more in the area of the raw gas inlet 66 of the filter 60 in front. At the same time, the Ca (OH) ₂ layer should be protected from excessive dust entry, otherwise the Pressure loss during the flow would increase. The most preferred location for using the Ca (OH) ₂ layer is therefore on the downstream side as an additional layer on the filter elements 50 after the fine separation of the dust. The desulphurisation layer can preferably be installed between the filter materials for pre-separation and fine separation of the dust. Installation as a fixed bed in front of the filter elements in the raw gas area of the filter housing or as a fixed bed after the filter elements in the clean gas area of the filter housing is also conceivable.

In 16 and 17th Embodiments of the functioning of a temperature control of the fine dust filter according to the invention with and without a recirculation unit are shown. Since there are no flue gas flaps or other throttling devices, the control takes place exclusively by influencing the speed of the fan. An increase in the fan speed also leads to an improved suction of the flue gases that come from below from the furnace to the suction unit, as well as to an increase in the proportion of false gas that reaches the suction unit from above. Since the free flow cross-sections above and below the suction point are of the same size, the negative pressure present in the suction point means that the proportions of the gases drawn in from above and below are approximately the same. Too high a proportion of false gas should be avoided as far as possible in order to keep the filter surface load low and to minimize the risk of condensate accumulation due to falling below the dew point due to excessive proportions of cold false air, especially if no recirculation unit is installed.

The required fan speed or the required negative pressure changes continuously during operation, especially since the amount and temperature of the flue gas is variable over the combustion phases of the fuel and the pressure loss of the filter due to the filter load increases with increasing operating time.

The fan speed should therefore be high enough to safely capture all of the flue gas coming from the furnace. On the other hand, the fan speed should not be too high in order to exclude the possibility of cooling down due to excessive infiltration of air.

• • Die untere Kamintemperatur-Messstelle T1 erkennt den Beginn und das Ende des Betriebs der Feuerung und schaltet die Ventilatorsteuerung ein bzw. aus, beispielsweise bei Temperaturen von größer 40 °C.
• • Die Filtereintrittstemperatur-Messstelle T2 schaltet bei Überschreitung der maximal zulässigen Betriebstemperatur der Filterelemente den Ventilator ab, um eine thermische Schädigung des Filtermaterials zu verhindern. Die Abschaltung des Ventilators führt zu einer Ableitung der ungefilterten heißen Rauchgas an die Atmosphäre, beispielsweise bei Temperaturen von größer 160 °C.

The controls of the two in 16 and 17th The variants shown with and without a recirculation unit have the following features in common:

• • The lower chimney temperature measuring point T1 recognizes the beginning and the end of the operation of the furnace and switches the fan control on or off, for example at temperatures above 40 ° C.
• • The filter inlet temperature measuring point T2 switches off the fan if the maximum permissible operating temperature of the filter elements is exceeded in order to prevent thermal damage to the filter material. Switching off the fan leads to the unfiltered hot flue gas being discharged into the atmosphere, for example at temperatures greater than 160 ° C.

The control of the fine dust filter according to the invention with a recirculation unit advantageously recognizes insufficient suction from the fact that there is a breakthrough of warmer flue gas, which is via the measuring point T4 is measured in the core flow of the extension of the original exhaust gas path. This temperature is compared with that of the recirculated clean gas that is in the recirculation room through the measuring point T3 is measured. If the difference of T4 and T3 is greater than a threshold value, the control detects a breakthrough of warmer flue gas and turns up the fan.

The fan is regulated down by the control when the temperature of the recirculated clean gas T3 is too low due to too high a proportion of false air and there is a risk of falling below the dew point. This is done T3 with a fixed value T _min compared for dew point detection. Another comparison takes place between T3 and T1 to evaluate the ratio of the temperatures of the raw gas to the recirculated clean gas.

The control of the fine dust filter according to the invention without a recirculation unit advantageously recognizes insufficient suction from the fact that there is a breakthrough of warmer flue gas, which is caused by the difference in gas temperature shortly before it escapes into the atmosphere T5 and the ambient temperature T6 is recognized. As long as T5 roughly in the range of T6 a flue gas breakthrough can be excluded. From the exceeding of a threshold value of the difference of T5 minus T6 the fan is turned up to increase the negative pressure in the extraction point so that the flue gas is completely captured and fed to the filter unit.

Similar to the variant with a recirculation circuit, the fan is switched off due to the clean gas temperatures being too low T7 turned down. This is done T7 compared with the minimum value due to the fact that the dew point is below Tmin as well as with the temperature of the raw gas T1 .

In both variants - with and without a recirculation unit - the fan speed is advantageously set as a dynamic equilibrium between the aforementioned boundary conditions "prevention of flue gas breakthrough" and "prevention of falling below the dew point". This dynamic equilibrium adapts itself advantageously to the flue gas quantities and temperatures, which change over the combustion phases of the furnace, as well as to the differential pressure across the filter medium, which increases over time.

A fully loaded filter medium is recognized by the control system in that not all of the flue gas is detected when the fan is running at maximum speed. The increasing filter loading can advantageously be recognized in advance via increasing speeds during the burn-off phase. This data can be sent from the control to the operator or chimney sweep, for example on a mobile phone, so that an early maintenance requirement can be reliably identified. On the other hand, it can also be recognized, for example, that the filter elements can be used for another heating period without replacement.

In addition to this data transmission, the control can also advantageously be parameterized remotely by sending changed threshold values for increasing and decreasing the fan speed to the control, for example by mobile phone.

18th shows a first embodiment of a shaping element 58 inside the filter bags in a filter unit 60 . A longitudinal section through a filter pocket is shown. When using pocket depth filters to clean exhaust gas from small solid fuel systems, the volume flow is less than 100 m ³ _N / h, in contrast to the usual use of these filter elements in ventilation technology with several 1,000 m ³ _N / h. As a result, there is the risk that the filter elements will not be set up due to the low volume flow or remain set up and collapse, so that not the entire filter surface of the pocket filter is used. According to the invention, this collapse can be achieved through the use of fixed shaping elements 58 be prevented. Wire bodies, for example, which are inside the filter elements or pockets, are used for this purpose 50 be arranged or - in 18th solid separating layers, not shown 54 , for example metallic separating layers 54 , between the pre-filter and the fine filter.

19th shows a second embodiment, which has several shaping elements 58 shows the inside of several filter bags in a filter unit 60 are arranged. A cross section through several filter pockets of a filter element located next to one another is shown 50 , consisting of a pre-filter 52 , Separation layer 54 and fine filter 56 .

20th shows an embodiment for expanding the temperature range of the device according to the invention. At locations with very low smoke gas temperatures at the extraction point, even when using recirculation circuits, there would be the risk of frequent drops below the dew point, which could sometimes limit the use of the device according to the invention. By additionally heating the flue gas, for example by 10 to 50 Kelvin, the device according to the invention can advantageously also be used at locations with very low flue gas temperatures that would otherwise not be possible. The energy requirement for the auxiliary heating is in the range of a few hundred watts and is therefore considerably smaller than the combustion output of the small combustion system, which is between 4,000 and 8,000 watts for individual room heating and is therefore an order of magnitude higher.

One example is a flexible inner tube 97 executed connecting element 38 and or 48 is advantageously with insulation to reduce heat loss 90 Mistake. A flexible outer hose is advantageously used as weather protection for the insulation 98 . Via electric heating elements 91 that are attached to the inner hose, additional heating can take place, through which the smoke gas temperature inside the inner hose 97 can be increased, so that this flue gas in heated form via the raw gas nozzle 66 enters the filter unit. Alternatively, the flue gas can also be heated via the nozzle 94 by the inflow of hot air, for example from a hot air blower, or the inflow of hot gas, for example combustion exhaust gas from a gas firing or an oil firing, whereby the flue gas is reheated.

20th also shows a preferred and simple way of fastening the connecting element 38 or. 48 on the filter unit. The inner tube 97 This is done by extending the raw gas inlet nozzle 66 slipped over and by means of clamps 95 attached. To protect against cutting into the clamps, a support for clamps is advantageously used as hose protection 96 used, for example designed as a thin sheet of metal in an open, overlapping design, which is wrapped around the inner hose and when tightening the clamps itself pulls itself around the inner hose. Advantageously, there is an additional seal, for example designed as a mat made of high-temperature silicone wound around the raw gas nozzle, between the raw gas nozzle 66 and inner tube 97 provided (not shown). According to the invention, this type of fastening of the connecting elements, like the camlock coupling, is one of the quick-release systems according to the invention.

It is also possible to use the present invention at locations with very high flue gas temperatures, in which the extracted flue gas is cooled to such an extent via false air 02 that the maximum operating temperature of the filter elements can be maintained.

This can be the case, for example, if the extraction point is close to the furnace and insulated flue gas pipes are used, as is the case with the subsequent installation of insulated stainless steel chimney pipes on the outside of buildings, in particular if the filter is at ground level, for example in the garden, according to 4th is involved.

The infiltration of air is advantageously carried out via the nozzle 92 and can have a regulating body 93 for air leakage can be regulated. The claim according to the invention of throttle-free flue gas paths still applies, since this throttle element only regulates the supply of false air. Due to a malfunction of the regulating organ 93 there can advantageously be no dangerous back pressure of flue gas.

The exemplary embodiments shown in the figures of the drawing and the exemplary embodiments explained in connection with them serve only to explain the invention and are not restrictive for it.

List of reference symbols

2

Ambient air / false air (fine dust content e.g. 0 mg / m ³ _N )

4th

Raw gas (fine dust content e.g. 100 mg / m ³ _N )

6th

Raw gas diluted with recirculated clean gas (fine dust content e.g. 85 mg / m ³ _N )

7th

Flue gas cleaned by a pre-filter (fine dust content e.g. 50 mg / m3 _N )

8th

Clean gas (fine dust content e.g. 10 mg / m3N)

9

Raw gas diluted with false air (fine dust content e.g. 80 mg / m ³ _N )

10

Flue gas path, for example chimney

12th

Exhaust pipe

14th

Weather protection and insulation

16

rain protection

20th

Device for electrostatic pre-agglomeration

22nd

Spray electrode

24

insulator

26th

High voltage generator

28

High voltage cables

29

Precipitation grid

30th

Suction unit

32

Connection pipe to the exhaust system

34

Suction opening (s)

36

Suction room

37

Outlet pipe

38

Connection unit / connection means from the suction unit to the filter unit

40

Recirculation unit

44

Recirculation room

46

Recirculation opening (s)

47

Recirculation connection

48

Connection unit / connection means from the filter unit to the recirculation unit

49

Baffle plate (s)

50

Filter element

52

Pre-filter

54

Separating layer

56

Fine filter

58

Shaping element

60

Filter unit

61

Humidity sensor

62

Filter housing

64

Maintenance cover

65

Fan

66

Raw gas inlet

67

Side chamber

68

Clean gas outlet

69

Holder for filter element

70

Partition walls for series connection of filter elements

72

silencer

76

Switching unit between silencer and additional filter

78

Additional filter

80

Desulfurization device upstream of the fine dust filter elements

82

Desulphurisation device integrated in fine dust filter elements

84

Desulfurization device, downstream of the fine dust filter elements

90

insulation

91

Heating element (s)

92

Support

93

Control organ for false air

94

Nozzle for hot air inflow

95

Clamps

96

Hose protection

97

Inner tube

98

Outer hose

T1

Chimney temperature measuring point below, connection piece 32 below

T2

Temperature measuring point filter inlet

T3

Temperature measuring point in the recirculation room

T4

Temperature measuring point for the exhaust gas core flow, approximately at the level of the recirculation room

T5

Chimney temperature measuring point at the top, just below the outlet to atmosphere

T6

Temperature measuring point atmosphere

T7

Temperature measuring point clean gas, after fan

Tmin

Minimum temperature filter element (s)

Tmax

Maximum temperature filter element (s)

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102008059432 [0007]

Non-patent literature cited

• DIN EN 779 (2012) [0023]

Claims (22)

Device for filtering fine dust, in particular for small solid fuel firing systems, comprising a suction unit (30) - A connecting pipe (32) for connecting the suction unit (30) to a flue gas path (10) from which a flue gas (04) flows from a furnace, and - a suction opening (34), and comprising a filter unit (60) - an inlet opening (66) connected to the suction opening (34) by means of a first connection unit (38), - an outlet opening (68), - A filter element (50) arranged between the inlet opening (66) and the outlet opening (68), and preferably - A fan (65) which is arranged between the outlet opening (68) and the filter element (50) and is set up to generate a suction pressure, wherein the suction unit (30) and the filter unit (60) are arranged spatially separated from one another as separate assemblies and are fluidically connected or connectable to one another by means of connecting units or means (38, 48). Device according to Claim 1 , further comprising a recirculation unit (40) connected to the suction unit (30) comprising - a recirculation opening (46) connected to the outlet opening (68) by means of a second connection unit (39), and - a guide plate (49) which is set up to to cause a mixture of a clean gas (08) flowing out of the outlet opening (68) with the flue gas (04). Device according to Claim 1 or Claim 2 , wherein the free flow cross section of the first connection unit (38) and / or the second connection unit (39) is smaller than the free flow cross section of the connecting pipe (32). Device according to one of the Claims 1 to 3 wherein the suction opening (34) is provided along a pipe circumference of the suction unit (30) and / or wherein the recirculation opening (46) is provided along a pipe circumference of the recirculation unit (40). Device according to one of the Claims 1 to 4th wherein a temperature sensor is provided which is arranged in the area of the suction opening (34) and is set up to activate the fan (65) when a predefined temperature of the flue gas (04) is exceeded. Device according to one of the Claims 1 to 5 , with a unit (20) for electrostatic pre-agglomeration, comprising - a spray electrode (22) around which a high voltage field is formed, - an insulator (24) connected to the spray electrode (22), which prevents the high voltage from flashing over to surrounding components, and - a high-voltage source (28) connected to the insulator (24) by means of a high-voltage cable (28). Device according to one of the Claims 1 to 6th , wherein a non-regenerable depth filter is provided as the filter element (50), which is designed to separate fine dust, condensate and / or condensate constituents. Device according to one of the Claims 1 to 7th , wherein the filter element comprises a filter according to filter class G4, M5, M6, F7 or F8 according to EN 779. Device according to one of the Claims 1 to 8th , a pre-filter (52) according to filter class M5 or M6 and a fine filter (56) according to filter class F7 or F8 being provided as the filter element, a separating layer (54) being provided between the pre-filter (52) and the fine filter (56) , which preferably consists of a coarse-pored material. Device according to one of the Claims 1 to 8th , a series connection of a separately arranged prefilter (52) and a separately arranged fine filter (56) being provided as the filter element, the prefilter (52) and the fine filter (56) being spatially separated from one another by means of at least one partition (70). Device according to one of the Claims 1 to 10 , wherein the filter unit (60) has an additional filter element (78) which is connected downstream of the filter element (50). Device according to Claim 11 , further comprising a silencer (72) and a switchover unit (76), which is set up to subsequently supply a gas that has already passed through the filter element (50) to the additional filter element (78) or the silencer (72). Device according to one of the Claims 1 to 12th , wherein the suction unit (30) has a conical, downwardly expanding shape. Device according to one of the Claims 1 to 13th wherein the filter unit (60) further comprises a desulfurization device (80, 82, 84). Device according to one of the Claims 1 to 14th , wherein the filter unit (60) further at least comprises a shaping element (58) which is set up to counteract a collapse of filter elements, in particular when the device is operated with low volume flows. Device according to one of the Claims 1 to 15th , whereby this fulfills the requirements of the First Ordinance for the Implementation of the Federal Immission Control Act as of June 13, 2019. Device according to one of the Claims 1 to 16 , the separating layer (54) between the pre-filter (52) and the fine filter (56) being made of sufficiently stable material so that it also takes over the function of the shaping element (58). Device according to one of the Claims 1 to 17th , wherein the connecting elements (38 and 48) can be mounted or denied using quick-release fasteners. Device according to one of the Claims 1 to 18th , a floor mat (63) for receiving and later evaporation of condensate occurring during start-up being attached or arranged on the filter base. Device according to one of the Claims 1 to 19th , whereby a moisture sensor (61) is provided in the area of the filter base to detect excessive condensate failure. Device according to one of the Claims 1 to 20th , whereby means or devices are provided which cause a change in the flue gas temperature before the flue gas enters the filter unit, preferably heating the flue gas by electrical heating elements (91) and / or by the inflow of hot air, preferably from a hot air blower, and / or a combustion exhaust gas, preferably from a gas firing or oil firing, or a cooling of the flue gas by false air (02), preferably by means of a regulating device (93) for false air. Device according to one of the Claims 1 to 21 , whereby the filter control enables a monitoring of the operation and / or a remote parameterization via a mobile radio-supported data transfer.

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