Biomass heating system with an improved electrostatic filter device

Description

TECHNICAL AREA

[0001] This application concerns a biomass heating system with an improved electrostatic filter system.

[0002] In particular, the invention relates to a biomass heating system with an electrostatic filter device having an improved electrode, an improved insulator, an improved cleaning mechanism and an improved control system. STATE OF THE ART

[0003] Biomass heating systems, especially biomass boilers, with a power output of 20 to 500 kW are well-known. Biomass can be considered an affordable, locally sourced, crisis-proof, and environmentally friendly fuel. Examples of combustible biomass, or biogenic solid fuels, include wood chips and pellets.

[0004] Pellets usually consist of wood shavings, sawdust, biomass, or other materials that have been compressed into small discs or cylinders with a diameter of approximately 3 to 15 mm and a length of 5 to 30 mm. Wood chips (also known as wood chips, wood shavings, or wood chips) are wood that has been shredded using cutting tools.

[0005] Biomass heating systems that use pellets and wood chips as fuel essentially consist of a boiler with a combustion chamber and an adjoining heat exchanger. Due to stricter legal regulations in many countries, some biomass heating systems also include a particulate filter or an electrostatic precipitator (also known as a "separator" or "e-filter").

[0006] Such filter devices or filters are disclosed in the prior art in EP 3 789 670 B1, EP 3 789 671 B1 and also EP 3 789 676 B1.

[0007] Due to the generally lower dust emissions compared to large combustion plants, there was long no need for this technology in small-scale biomass combustion systems. Therefore, the use of this technology in smaller-capacity biomass heating systems (under 500 kW) is relatively new, and there is considerable room for improvement. This application primarily concerns such smaller-capacity biomass heating systems.

[0008] It wasn't until the early 2000s that increased public awareness arose regarding particulate matter emissions from small combustion plants. For example, the introduction of the First Federal Immission Control Ordinance (1. BImSchV) in Germany in 2010 led to a change in thinking. The 1. BImSchV prescribes particularly stringent requirements for particulate matter emissions from pellet and wood chip combustion plants with a capacity of less than 500 kW for the period after December 31, 2014. Specifically, limit values ​​for particulate matter of less than 20 mg / Nm³ (based on dry flue gas and 13 vol% O₂) must be met. A key requirement of this law is that these particulate matter emissions must be verified not only during type testing but also through annual inspections by chimney sweeps during field operation. Similar regulations apply in many other countries.This means that filters for biomass heating systems in the lower power range (< 500 kW), which is the core focus of this revelation, require a long-term, increased filter effect (long-term operational stability with high separation efficiency), while at the same time the filter must be compact enough to be integrated into a small combustion boiler.

[0009] Biomass heating systems regularly include various other accessories, such as fuel conveying devices, control devices, probes, safety thermostats, pressure switches, flue gas or exhaust gas recirculation, boiler cleaning and a separate fuel container.

[0010] The combustion chamber typically includes a fuel supply system, an air supply system, and a fuel ignition device. The air supply system usually incorporates a low-pressure blower to optimize the thermodynamic conditions during combustion. The fuel supply system can be configured, for example, as a side-loading system (so-called cross-feed combustion). In this case, the fuel is fed into the combustion chamber from the side via a screw conveyor or piston.

[0011] In the combustion chamber of a fixed-bed furnace, a grate is typically provided, onto which the fuel is continuously fed and burned. This grate holds the fuel for combustion and has openings, such as slots, that allow some of the combustion air to pass through as primary air to the fuel. The grate can be either fixed or movable. There are also grate furnaces in which the combustion air is supplied not through the grate, but only laterally.

[0012] When primary air flows through the grate, it is also cooled, thus protecting the material. Furthermore, insufficient air supply can lead to slag formation on the grate. In particular, combustion systems intended to be fueled with different fuels, which is the primary focus of this disclosure, have the inherent problem that different fuels have different ash melting points, moisture contents, and combustion behavior. This makes it difficult to design a heating system that is equally suitable for different fuels. The combustion chamber can also be typically divided into a primary combustion zone (immediate combustion of the fuel on the grate and in the gas space above it before the supply of further combustion air) and a secondary combustion zone (afterburning of the flue gas after a further supply of air).In the combustion chamber, the fuel undergoes drying, pyrolytic decomposition, gasification, and charcoal combustion. To ensure complete combustion of the resulting flammable gases, additional combustion air is introduced in one or more stages (secondary or tertiary air) at the beginning of the secondary combustion zone.

[0013] The combustion of pellets or wood chips after drying essentially comprises two phases. In the first phase, the fuel is at least partially pyrolytically decomposed and converted into gas by high temperatures and air that can be blown into the combustion chamber. In the second phase, the combustion of the gasified portion, as well as any remaining solids (such as charcoal), takes place. The fuel then releases gas, and the resulting gas, along with any charcoal present, is combusted.

[0014] Pyrolysis is the thermal decomposition of a solid in the absence of oxygen. It can be divided into primary and secondary pyrolysis. The products of primary pyrolysis are pyrolysis coke and pyrolysis gases, which can be further subdivided into condensable and non-condensable gases at room temperature. Primary pyrolysis occurs at roughly 250–450°C, and secondary pyrolysis at approximately 450–600°C. The subsequent secondary pyrolysis is based on the further reaction of the primary pyrolysis products. Drying and pyrolysis largely occur without the use of air, as volatile CH₄ compounds escape from the particles, preventing air from reaching the particle surface. Gasification can be considered part of the oxidation process; it involves the reaction of the solid, liquid, and gaseous products formed during pyrolytic decomposition through further heat application.This occurs with the addition of a gasifying agent such as air, oxygen, water vapor, or carbon dioxide. The lambda value during gasification is greater than zero and less than one. Gasification takes place at temperatures of approximately 300 to 850°C or even up to 1,200°C. Complete oxidation with excess air (lambda greater than 1) subsequently occurs through the addition of further air to these processes. The reaction end products are essentially carbon dioxide, water vapor, and ash. The boundaries between all phases are not rigid but gradual. The combustion process can be effectively controlled using a lambda probe installed at the boiler's exhaust outlet.

[0015] In general terms, the efficiency of combustion is increased by converting the pellets into gas because gaseous fuel mixes better with the combustion air and is therefore more completely converted, resulting in lower emissions of pollutants, fewer unburned particles and ash (fly ash or dust particles).

[0016] The combustion of biomass produces gaseous or airborne combustion products, the main components of which are carbon, hydrogen, and oxygen. These can be categorized into emissions from complete oxidation, incomplete oxidation, and trace elements or impurities. Emissions from complete oxidation consist primarily of carbon dioxide (CO₂) and water vapor (H₂O). The formation of carbon dioxide from the carbon in the biomass is the goal of combustion, as this allows for more complete utilization of the released energy. The release of carbon dioxide (CO₂) is largely proportional to the carbon content of the fuel burned; thus, the amount of carbon dioxide also depends on the amount of usable energy to be provided. A reduction can essentially only be achieved by improving efficiency.Combustion residues, such as ash or slag, are also produced.

[0017] However, the complex combustion processes described above are not easy to control. Therefore, there is a general need for improvement regarding combustion processes in biomass heating systems.

[0018] In addition to the air supply to the combustion chamber, flue gas recirculation systems are also known, which return exhaust gas from the boiler to the combustion chamber for cooling and re-combustion. In the prior art, these systems typically include openings in the combustion chamber for the supply of primary air via a primary air line, and circumferential openings in the combustion chamber for the supply of secondary air from a secondary air line or possibly fresh air. Flue gas recirculation can occur below or above the grate. Furthermore, flue gas recirculation can be mixed with the combustion air or separate.

[0019] The flue gas or exhaust gas from the combustion in the combustion chamber is fed to the heat exchanger, so that the hot combustion gases flow through the heat exchanger to transfer heat to a heat exchange medium, which is usually water at around 80°C (typically between 70°C and 110°C). The boiler also typically has a radiant section integrated into the combustion chamber and a convection section (the heat exchanger connected to it).

[0020] The ignition device is usually a hot air system or a glow plug system. In the first case, combustion is initiated by supplying hot air to the combustion chamber, which is heated by an electrical resistor. In the second case, the ignition device has one or more glow plugs / rods to heat the pellets or wood chips through direct contact until combustion begins. The glow plugs can also be equipped with a motor to remain in contact with the pellets or wood chips during the ignition phase and then retract to avoid being exposed to the flames. This solution is prone to wear and tear and is more complex.

[0021] The main problems with conventional biomass heating systems are that gaseous or solid emissions are too high, efficiency is too low, and dust emissions are too high.

[0022] A further problem is the varying quality of the fuel, due to its differing moisture content and particle size, which makes consistent combustion with low emissions difficult. This is particularly problematic for biomass heating systems designed to be compatible with various types of biological or biogenic fuel. The varying quality and consistency of the fuel make it challenging to maintain consistently high efficiency. For example, significantly increased particle and soot emissions can occur with moist fuel, non-standardized fuel, or when the biomass heating system is not operating at its optimal point due to improperly stored fuel. However, it is desirable to operate a biomass heating system with the lowest possible emissions even under less than ideal conditions. There is considerable room for improvement in this area.

[0023] Regarding the prior art filters described in EP 3 789 670 B1, EP 3 789 671 B1, and EP 3 789 676 B1, improvements are needed concerning the problems mentioned above. Further boilers with electrostatic precipitators are known from publications EP 3 789 672 A1 and EP 2 208 538 A1. US 2011 / 047976 A1 discloses an electrostatic precipitator system with a porcelain feedthrough that can be heated for cleaning purposes.

[0024] With these state-of-the-art filters, it is desirable to improve their functionality and filtration efficiency. Testing of these filters has shown that soot buildup can lead to flashovers, and that this soot cannot be efficiently removed. Furthermore, the cleaning performance of these filters has been deemed insufficient, particularly considering the stricter legal regulations that have been introduced in many European countries in recent years.

[0025] It can therefore be an object of the invention to provide a biomass heating system in hybrid technology which is low in emissions (especially with regard to particulate matter, CO, hydrocarbons, NOx), which can in particular be operated flexibly with wood chips and pellets, and which has a high efficiency.

[0026] It may also be a task of the invention to provide a more efficient and functionally optimized electrostatic filter.

[0027] The following considerations can play a role in the invention and in addition: The hybrid technology should enable the use of both pellets and wood chips with water contents between 8 and 35 percent by weight.

[0028] The aim is to achieve the lowest possible gaseous emissions (less than 50 or 100 mg / Nm³ based on dry flue gas and 13% O₂ by volume).

[0029] Very low dust emissions of less than 15 mg / Nm³ without and less than 5 mg / Nm³ with electrostatic precipitator operation are targeted.

[0030] A high efficiency of up to 98% (based on the supplied fuel energy (heating value)) is to be achieved.

[0031] Furthermore, one can consider that the operation of the system should be optimized. For example, easy ash removal, easy cleaning, or easy maintenance should be possible.

[0032] Furthermore, a high level of system availability is required.

[0033] The aforementioned task(s) or potential individual problems may also relate to individual aspects of the overall system, for example to regulation and / or control.

[0034] The aforementioned task(s) is / are solved by the subject matter of the independent claim. Further aspects and advantageous developments are the subject matter of the dependent claims.

[0035] According to the present disclosure, a biomass heating plant is provided for the combustion of fuel in the form of pellets and / or wood chips.

[0036] The advantages of this configuration and also of the following aspects will become apparent from the following description of the associated exemplary implementations.

[0037] In this context, "horizontal" can refer to a planar orientation of an axis or cross-section, assuming that the boiler is also horizontally oriented, with the ground level serving as the reference point. Alternatively, "horizontal" can mean "parallel" to the boiler's base plane, as it is usually defined. Another alternative, particularly in the absence of a reference plane, is that "horizontal" can simply be understood as "parallel" to the combustion plane of the grate.

[0038] Within the scope of the present disclosure, an electrostatic filter device is disclosed independently of the biomass heating system, wherein the electrostatic filter device comprises the following: a tubular inner volume in which the flue gas flows; a first rod-shaped electrode, which is designed as a spray electrode; and a second tubular electrode, which is designed as a counter electrode; and an insulator for holding the spray electrode; and a filter inlet through which the flue gas can enter the filter device; and a filter outlet through which the flue gas can exit the filter device.

[0039] This electrostatic filter device can also be combined independently of the existing biomass heating system with individual aspects or features of the embodiments described below.

[0040] These individual aspects and also the standard procedures can also be combined with other aspects and individual features of the present disclosure disclosed herein, as the person skilled in the art considers technically feasible.

[0041] The biomass heating system according to the invention is explained in more detail below in exemplary embodiments and individual aspects with reference to the figures of the drawing: Fig. 1 shows a three-dimensional overview view of a biomass heating system according to an embodiment of the invention; Fig. 2 shows a cross-sectional view through the biomass heating system. Fig. 1 , which was carried out along a section line SL1 and which is shown viewed from the side view S; Fig. 3 also shows a cross-sectional view through the biomass heating plant of the Fig. 1 with a representation of the flow pattern, wherein the cross-sectional view was taken along a section line SL1 and is shown viewed from the side view S; Fig. 4 shows a highlighted part of the filter assembly from a side view of the biomass heating plant; Fig. 5 shows the highlighted part of the filter assembly of the Fig. 4 from a perspective view and from the side and from below; Fig. 6 shows different views of the spray electrode of the Fig. 5 , wherein individual parts of the spray electrode are shown as electrode parts, as well as a bottom view of the assembled electrode from direction F1 and a sectional view of the assembled electrode along the section line F2; Figs. 7a to 7d show alternative spray electrodes with alternative profiles; Fig. 8a shows a side view of an insulator 46; Fig. 8b shows a section IS of the Fig. 8a Fig. 9 shows a side view of the insulator of the Fig. 8a together with a mounting plate; Fig. 10 shows a highlighted perspective view of the Fig. 8a from a top-down oblique view; Fig. 11 shows a general operating procedure of the present biomass heating plant; Fig. 12a shows a method for controlling a filter device during combustion stabilization, i.e., a filter stabilization control method; Fig. 12b shows a method for controlling the filter device 4 during combustion (in normal combustion operation of the boiler), i.e., a filter combustion control method; Fig. 12c shows a method for controlling the filter device 4 during burnout, i.e., a filter burnout control method; Fig. 12d shows a method for controlling the filter device to prevent breakdown in the filter, i.e., a filter breakdown control method DU; Fig. 13 shows a power diagram, a voltage diagram, and a current diagram with a common time axis of an exemplary cycle of combustion operation of the biomass heating plant from ignition to burnout; Fig.Figure 14 shows a cross-section through the biomass heating system of the . Fig. 2 with the result of a CFD temperature simulation; Fig. 15 shows a cross-section through the biomass heating system of the Fig. 2 with the result of a CFD flow simulation, which is combined with the CFD temperature simulation of the Fig. 14 corresponds; Fig. 16a shows a three-dimensional sectional view of the filter device of the biomass heating plant of the Fig. 2 from behind (i.e. from a direction opposite to arrow V of the Fig. 1 is) in a resting state of cleaning; Fig. 16b shows a planar sectional view of the filter device of the biomass heating system from the rear in the resting state of cleaning. Fig. 16a Fig. 17a shows a three-dimensional sectional view of the filter device of the biomass heating plant from the rear in a first cleaning state; Fig. 17b shows a planar sectional view of the filter device of the biomass heating plant from the rear in the first cleaning state of the Fig. 17a Fig. 18a shows a three-dimensional sectional view of the filter device of the biomass heating plant from the rear in a second cleaning state; Fig. 18b shows a planar sectional view of the filter device of the biomass heating plant from the rear in the second cleaning state. Fig. 18a Fig. 19a shows a three-dimensional sectional view of the filter device of the biomass heating plant from the rear in a third cleaning state; Fig. 19b shows a planar sectional view of the filter device of the biomass heating plant from the rear in the third cleaning state of the Fig. 19a Fig. 20a shows a three-dimensional sectional view of the filter device of the biomass heating plant from the rear in a fourth cleaning state; Fig. 20b shows a planar sectional view of the filter device of the biomass heating plant from the rear in the fourth cleaning state of the Fig. 20a Figures 21a to 21d show different views of the stop lever 96 with its conical striking head 97. DESCRIPTION OF EXAMPLE EXECUTIONS OF THE INVENTION

[0042] Various embodiments of the present invention are disclosed below by way of example with reference to the accompanying drawings. However, the embodiments and the terms used therein are not intended to limit the present invention to specific embodiments.

[0043] If more general terms are used in the description for features or elements shown in the figures, it is intended that the person skilled in the art will not only be informed of the specific feature or element shown in the figures, but also of the more general technical teaching.

[0044] Regarding the description of the figures, the same reference symbols can be used in the individual figures to refer to similar or technically equivalent elements. Furthermore, for the sake of clarity, more elements or features with reference symbols may be shown in individual detail or section views than in the overview views. It should be assumed that these elements or features are also revealed accordingly in the overview views, even if they are not explicitly listed there.

[0045] It is to be understood that a singular form of a noun corresponding to an object may include one or more of the things, unless the context in question clearly indicates otherwise.

[0046] In the present disclosure, an expression such as "A or B," "at least one of A and / or B," or "one or more of A and / or B" can include all possible combinations of the listed features. Expressions such as "first," "second," "primary," or "secondary" used herein can represent different elements regardless of their order and / or meaning and do not limit corresponding elements. When it is described that an element (e.g., a first element) is "functionally" or "communicatively" coupled or connected to another element (e.g., a second element), the element can be connected directly to the other element or connected to the other element via another element (e.g., a third element).

[0047] The expression "configured to" (or "set up") used in this disclosure may, for example, be replaced by "suitable for", "fitted to", "adapted to", "made to", "capable of", or "designed to", depending on what is technically feasible. Alternatively, in a particular situation, the expression "device configured to" or "set up to" may mean that the device can work together with another device or component, or perform a corresponding function.

[0048] All dimensions given in "mm" are to be understood as a size range of +- 1 mm around the specified value, unless a different tolerance or other ranges are explicitly stated.

[0049] It should be noted that the individual aspects presented here, such as the rotary grate, the combustion chamber or the filter device, are disclosed separately from or distinct from the biomass heating system as individual parts or devices.

[0050] Furthermore, for the sake of clarity, not all features and elements are individually labeled in the figures, especially when they are repeated. Rather, the elements and features are labeled as examples. Analogous or identical elements should then be understood as such.

[0051] Fig. 1 Figure 1 shows a three-dimensional overview view of the biomass heating system 1 according to an embodiment of the invention.

[0052] In the figures, arrow V indicates the front view of plant 1, and arrow S indicates the side view of plant 1.

[0053] The biomass heating system 1 has a boiler 11, which is mounted on a boiler base 12. The boiler 11 has a boiler housing 13, for example made of sheet steel. The insulation of the boiler 11 is not fully shown.

[0054] In the front part of the boiler 11 is a combustion unit 2 (not shown), which can be accessed via a first maintenance opening with a closure 21. A rotary mechanism bracket 22 for a rotary grate 25 (not shown) supports a rotary mechanism 23, by which drive forces can be transmitted to bearing shafts 81 of the rotary grate 25.

[0055] In the middle part of the boiler 11 there is a heat exchanger 3 (not shown), which can be accessed from above via a second maintenance opening with a closure 31.

[0056] In the rear part of the boiler 11 there is an electrostatic filter device 4 (also referred to as filter 4) with an electrode 45 (cf. Fig. 2 ff.), which is suspended by an insulating electrode holder 43, and which is energized via an electrode supply line 42. The filter device 4 has a tubular inner volume 46b, which extends in a longitudinal direction of the filter device 4.

[0057] The exhaust gas from the biomass heating system 1, which has flowed through the filter unit 4, is discharged via an exhaust gas outlet 41, which is located downstream of the filter unit 4 (fluidically). A fan or a blower can be provided here.

[0058] Behind the boiler 11 a recirculation device 5 is provided, which recirculates part of the flue gas or exhaust gas via recirculation channels 51, 53 and 54 and flaps 52 for cooling the combustion process and reuse during the combustion process.

[0059] Furthermore, the biomass heating system 1 has a fuel supply 6, by which the fuel is conveyed in a controlled manner from the side onto the rotary grate 25 in the primary combustion zone 26 of the combustion unit 2. The fuel supply 6 has a rotary valve 61 with a fuel supply opening 65, the rotary valve 61 having a drive motor 66 with control electronics. An axle 62 driven by the drive motor 66 drives a transmission mechanism 63, which can drive a fuel auger 67 (not shown), so that the fuel is conveyed to the combustion unit 2 in a fuel supply channel 64.

[0060] In the lower part of the biomass heating system 1, an ash removal device 7 is provided, which has an ash discharge screw 71 in an ash discharge channel, which is operated by a motor 72.

[0061] The biomass heating system 1 also includes a control unit 100. This control unit 100 is equipped with a conventional processor, volatile and non-volatile memory (e.g., (S-)RAM, ROM, Flash, and / or cache memory), and various interfaces. These interfaces can be analog or digital inputs and outputs. For example, CAN bus interfaces, 0-10V analog inputs, or 4-20 mA analog inputs / outputs for sensors and actuators, and / or RS-232 interfaces can be provided. In addition, the control unit preferably (optionally) has at least one interface with an internet protocol (IP, Ethernet, WLAN) according to established standards. This allows the control unit to communicate, preferably via the internet, with data processing equipment installed remotely from the biomass heating system 1.

[0062] With the ability to communicate with remotely located data processing facilities or a central server, the control unit 100 can be part of a distributed machine learning system, which will later be used in relation to the Figuren 19 is explained in more detail.

[0063] Furthermore, the control unit 100 can have a keyboard and / or a display for showing operating data. The display can also have a touch function, allowing an operator to enter data on the display.

[0064] The control unit 100 can also include a voltage generation unit which provides the voltage required for the operation of the filter unit 4.

[0065] In addition to the control unit 100, several sensors are provided for recording physical and / or chemical parameters of the biomass heating system 1. Examples of such sensors are related to the Fig. 2 described in more detail.

[0066] One of the sensors that can be communicatively connected to the control unit 100 can be a boiler temperature sensor 115. A combustion chamber 24 or boiler tubes 32 (see below). Fig. 2 ) are at least partially separated by a heat exchange medium 38 (cf. Fig. 2 ), for example, (heating) water. The boiler temperature sensor 115 measures or records the temperature of the heat exchange medium 38 in the boiler 11, preferably at a location that is representative of an average temperature of the heat exchange medium 38 in the boiler 11.

[0067] The temperature detected by the boiler temperature sensor 115 is communicated to the control unit 100 (preferably as a signal, for example as a voltage signal, as a current signal or as a digital signal), which makes the temperature (which may still need to be calculated from the signal, for example a voltage of 1 volt could correspond to 10 degrees Celsius above zero) available to the control unit 100 for further processing.

[0068] The control unit can store the temperature detected by the boiler temperature sensor 115 in a (permanent or volatile) memory, and / or use the temperature as training data for machine learning.

[0069] The above statements concerning boiler temperature sensor 115 and the measured temperature (as a measured physical quantity) can also be applied to other sensors and physical or chemical quantities, in particular to sensors which relate to Fig. 2 can be described. In particular, the following sensors can be used: fuel bed height or glowing bed height sensor 86, lambda probe 112, exhaust gas temperature sensor 111, vacuum sensor 113, and heating water temperature sensor 114.

[0070] Furthermore, the control unit can have 100 sensors with which the (target) voltage that is to be applied to the electrode 45 of the filter unit 100 and the current If flowing in the filter unit 4 can be detected. Thus, the control unit 100 can have current sensing means for detecting the current through the electrode 45. Likewise, the control unit 100 can have voltage sensing means for detecting the filter voltage Vf that is applied to the electrode 45.

[0071] Furthermore, the actuators of the biomass heating system 1 can also be communicatively connected to the control unit 100. For example, the air valves 52 of the recirculation device 5, the ignition device 201, the motors 231 and 66, the electrostatic filter 4 or the electrostatic precipitator 4 (e.g., its on / off state Sf), the ash removal 7 or its motor 72, the fuel supply 6 with its rotary valve 61 or its drive motor 66, or the cleaning device 9 with its drive 91 can be controlled by the control unit 100.

[0072] The filter device 4 is also communicatively connected to the control device 100 in such a way that the state, voltage, and / or current of the electrode 45 can be controlled. The control device 100 can be configured such that the on / off state Sf of the electrode 45 and its voltage Vf can be set. For example, the voltage can be set in a range of 10–80 kV, preferably in a range of 10–60 kV.

[0073] The control unit 100 can thus regulate the biomass heating system 1. At least one measured physical / chemical quantity and / or at least one electrotechnical quantity from at least one sensor of the biomass heating system 1 is communicated to the control unit 100. The biomass heating system 1 uses this quantity(ies) to calculate a control response, which in turn is used to adjust at least one actuator of the biomass heating system 1. Based on the adjustment of at least one actuator, the physical / chemical processes in the biomass heating system 1 (especially those of combustion) are influenced, which is again detected by the at least one sensor. This completes at least one control loop. Due to the multitude of possible control tasks of the control unit 100, it can also control more than one control loop of the biomass heating system simultaneously.

[0074] In particular, the control of the filter device (voltage control of electrode 45) can be based on various measured parameters. This will be discussed in more detail later.

[0075] Fig. 2 shows a cross-sectional view through the biomass heating plant 1 of the Fig. 1 , which was carried out along a section line SL1 and which is shown viewed from side view S. In the corresponding Fig. 3 , which have the same cut as Fig. 2 For the sake of clarity, the flue gas flows "S" and flow-related cross-sections are shown schematically (these flows also correspond to process steps S1..., from the generation of the flue gas to its exit from the biomass heating plant 11). Fig. 3 It should be noted that individual areas, compared to the Fig. 2 are shown dimmed. This is only for the sake of clarity. Fig. 3 and the visibility of the flow arrows S5, S6 and S7.

[0076] From left to right are in Fig. 2 The combustion unit 2, the heat exchanger 3, and an (optional) filter unit 4 of the boiler 11 are provided. The boiler 11 is mounted on the boiler base 12 and has a multi-walled boiler housing 13 in which water or another fluid heat exchange medium 38 can circulate. A water circulation unit 14 with pump, valves, pipes, etc., is provided for the supply and discharge of the heat exchange medium.

[0077] The combustion unit 2 has a combustion chamber 24 in which the combustion process of the fuel takes place. The combustion chamber 24 has a multi-part rotary grate 25 on which the fuel bed 28 rests. The multi-part rotary grate 25 is rotatably mounted by means of a plurality of bearing shafts 81.

[0078] Further referring to Fig. 2 and Fig. 3 The primary combustion zone 26 of the combustion chamber 24 is enclosed by (a plurality of) combustion chamber bricks 29, whereby the combustion chamber bricks 29 define the geometry of the primary combustion zone 26. The cross-section of the primary combustion zone 26 (for example) along the horizontal section line A1 is essentially oval (for example, 380 mm ± 60 mm x 320 mm ± 60 mm; it should be noted that some of the above size combinations may also result in a circular cross-section). The arrow S1 schematically represents the flow from the secondary air nozzle 291, this flow (which is shown purely schematically) exhibiting a swirl induced by the secondary air nozzles 291 to improve the mixing of the flue gas.

[0079] The secondary air nozzles 291 are designed such that they introduce the secondary air (preheated by the combustion chamber bricks 29) tangentially into the combustion chamber 24 with its oval cross-section. This creates a turbulent or swirling flow S1, which roughly spirals upwards. In other words, an upward spiral flow rotating around a vertical axis is formed.

[0080] The secondary air nozzles 291 are thus oriented such that they introduce the secondary air – viewed in the horizontal plane – tangentially into the combustion chamber 24. In other words, the secondary air nozzles 291 are each designed as an inlet for the secondary air that is not aligned with the center of the combustion chamber. Furthermore, such a tangential inlet can also be used with a circular combustion chamber geometry.

[0081] All secondary air nozzles 291 are oriented such that each one produces either a clockwise or counterclockwise flow. Therefore, each secondary air nozzle 291 can contribute to the generation of the vortex flows, with each secondary air nozzle 291 having the same orientation. It should be noted that in exceptional cases, individual secondary air nozzles 291 may also be arranged in a neutral orientation (oriented towards the center) or in a counterclockwise orientation (with the opposite orientation), although this may impair the aerodynamic efficiency of the arrangement.

[0082] The combustion chamber bricks 29 form the inner lining of the primary combustion zone 26, store heat, and are directly exposed to the fire. Thus, the combustion chamber bricks 29 also protect the other materials of the combustion chamber 24, such as cast iron, from direct flame exposure. The combustion chamber bricks 29 are preferably adapted to the shape of the grate 25. The combustion chamber bricks 29 also feature secondary air or recirculation nozzles 291, which recirculate the flue gas into the primary combustion zone 26 for re-participation in the combustion process and, in particular, for cooling as needed. The secondary air nozzles 291 are not aligned towards the center of the primary combustion zone 26, but are oriented acentrically to create a swirl in the flow within the primary combustion zone 26 (i.e., a swirl and vortex flow, which will be explained in more detail later). The combustion chamber bricks 29 will be described in more detail later.An insulation 311 is provided at the boiler tube inlet. The oval cross-sectional shape of the primary combustion zone 26 (and the nozzle) as well as the length and position of the secondary air nozzles 291 advantageously promote the formation and maintenance of a vortex flow, preferably up to the ceiling of the combustion chamber 24.

[0083] A secondary combustion zone 27 adjoins the primary combustion zone 26 of the combustion chamber 26, either at the level of the combustion chamber nozzles 291 (from a functional or combustion-technical perspective) or at the level of the combustion chamber nozzle 203 (from a purely structural or constructional perspective), and defines the radiant section of the combustion chamber 26. In the radiant section, the flue gas produced during combustion transfers its thermal energy primarily through thermal radiation, particularly to the heat exchange medium, which is located in the two left-hand chambers for the heat exchange medium 38. The corresponding flue gas flows are shown in Fig. 3 Arrows S2 and S3 are shown purely as examples. These vortex flows may also include slight backflows or other turbulence, which are not represented by the purely schematic arrows S2 and S3. However, the basic principle of the flow pattern in combustion chamber 24 is clear or calculable to a person skilled in the art, based on arrows S2 and S3.

[0084] The secondary air injection causes pronounced swirling, rotational, and vortex flows to form in the isolated or confined combustion chamber 24. The oval geometry of the combustion chamber 24, in particular, contributes to the undisturbed and optimal development of these vortex flows.

[0085] After exiting the nozzle 203, which further concentrates these vortex flows, candle-flame-shaped rotational flows S2 appear, which can advantageously extend to the combustion chamber ceiling 204, thus making better use of the available space in the combustion chamber 24. The vortex flows are concentrated in the center of the combustion chamber and ideally utilize the volume of the secondary combustion zone 27. Furthermore, the constriction formed by the combustion chamber nozzle 203 reduces the rotational flows, thereby generating turbulence to improve the mixing of the air-flue gas mixture. Thus, cross-mixing occurs due to the constriction or narrowing caused by the combustion chamber nozzle 203. However, the rotational momentum of the flows is retained, at least partially, even above the combustion chamber nozzle 203, maintaining the propagation of these flows up to the combustion chamber ceiling 204.

[0086] The secondary air nozzles 291 are integrated into the elliptical or oval cross-section of the combustion chamber 24 in such a way that, due to their length and orientation, they induce vortex flows which set the flue gas-secondary air mixture into rotation and thereby (further improved by combination with the combustion chamber nozzle 203 positioned above it) enable complete combustion with minimal excess air and thus maximum efficiency.

[0087] The secondary air supply is designed in such a way that it cools the hot combustion chamber bricks 29 by flowing around them and the secondary air itself is preheated, thereby accelerating the combustion rate of the flue gases and ensuring complete combustion even at extreme partial load (e.g. 30% of the nominal load).

[0088] The first maintenance opening 21 is insulated with an insulating material, for example, Vermiculite™. The secondary combustion zone 27 is designed to ensure complete combustion of the flue gas. The specific geometric design of the secondary combustion zone 27 will be explained in more detail later.

[0089] After the secondary combustion zone 27, the flue gas flows into the heat exchanger 3, which has a bundle of boiler tubes 32 arranged parallel to each other. The flue gas then flows downwards in the boiler tubes 32, as described in Fig. 3 Indicated by arrows S4. This part of the flow can also be described as the convection section, since the heat transfer from the flue gas occurs primarily at the boiler tube walls via forced convection. The temperature gradients in the heat exchanger medium, for example the water, caused in boiler 11 result in natural water convection, which promotes mixing of the boiler water.

[0090] Spring turbulators 36 and spiral or belt turbulators 37 are arranged in the boiler tubes 32 to improve the efficiency of the heat exchanger 4. This will be explained in more detail later.

[0091] The outlet of the boiler tubes 32 leads via the reversing chamber inlet 34 into the reversing chamber 35. The reversing chamber 35 is sealed against the combustion chamber 24 in such a way that no flue gas can flow directly back from the reversing chamber 35 into the combustion chamber 24. However, a common (discharge) path is still provided for the combustion residues that can accumulate in the entire flow area of ​​the boiler 11. If the filter device 4 is not provided, the flue gas is discharged upwards again in the boiler 11. The other case, the optional filter device 4, is described in the Fig. 2 and 3The flue gas is shown. After passing through the turning chamber 35, it is directed upwards again into the filter unit 4 (see arrows S5), which in this case is an example of an electrostatic filter unit 4. Flow baffles can be provided at the inlet 44 of the filter unit 4 to even out the flow of flue gas into the filter.

[0092] Electrostatic precipitators, also known as electrostatic precipitators, are devices for separating particles from gases based on the electrostatic principle. These filter devices are used particularly for the electrical cleaning of exhaust gases. In electrostatic precipitators, dust particles are electrically charged by a corona discharge from a spray electrode and attracted to the oppositely charged electrode (precipitation electrode). The corona discharge takes place on a suitable, charged high-voltage electrode (also called a spray electrode) inside the electrostatic precipitator.

[0093] The (spray) electrode 45 is designed with protruding tips and possibly sharp edges because the density of the field lines, and thus the electric field strength, is greatest there, thereby promoting corona discharge. Further details on an optimized geometry can be found later in relation to the Figuren 4 bis 6 .

[0094] The opposite electrode (counter electrode or precipitation electrode) usually consists of a grounded section of exhaust pipe or a cage-like arrangement that is positioned or provided around the electrode.

[0095] The separation efficiency of an electrostatic precipitator depends in particular on the residence time of the exhaust gases in the filter system and the voltage between the spray and separation electrodes. The rectified high voltage required for this is provided by the voltage generation unit of the control device 100 (not shown). The electrode 45 consists at least largely of high-grade spring steel or chromium steel and is held by an electrode holder 43 via an insulator 46, i.e., an electrode insulation 46.

[0096] The holder 43 for the electrode 45 and, in particular, the insulator 46 are exposed to dust and dirt, as they are located on or in the flue gas-carrying interior. Therefore, special measures are required to prevent unwanted leakage currents, which will be discussed later in relation to the Figuren 8 will be described below.

[0097] As in Fig. 2 shown is an optimized rod-shaped electrode 45 (which is described in more detail later, see below). Figuren 4 bis 7 ) held approximately in the middle of an approximately chimney-shaped or elongated interior space of the filter device 4.

[0098] This (spray) electrode 45 hangs downwards in the interior of the filter device 4 in a way that allows it to oscillate or swing. The electrode 45 can, for example, swing back and forth perpendicular to its longitudinal axis.

[0099] A cage 48 serves simultaneously as a counter electrode and as a cleaning mechanism for the filter unit 4. The cage 48 is connected to ground potential. Due to the prevailing potential difference, the flue gas or exhaust gas flowing in the filter unit 4 (see arrows S6) is filtered, as explained above. Arrows S6 roughly indicate the range in which a flue gas flow velocity can be determined as a reference. In this range inside the tubular filter unit 4, the flow velocity is in the range of 0.5 to 3 m / s, preferably in the range of 1 to 2 m / s, when the biomass heating system is operating at full load. Full load operation is defined as the operation of the biomass heating system in which at least 90% of the nominal output [kW] (for which the boiler 11 is designed and regularly certified) is delivered.The biomass heating system 1 is designed accordingly. Partial load operation is understood to mean operation of boiler 11 or the biomass heating system 1 below this 90%.

[0100] The indicator line WT3 shows an exemplary cross-sectional line through the filter unit 4, in which the flow is set up as homogeneously as possible or roughly uniformly distributed across the cross-section of the boiler tubes 32 (due, among other things, to flow baffles at the inlet of the filter unit 4 and the geometry of the reversing chamber 35). A uniform flow through the filter unit 3 or the last boiler pass minimizes stringing and thus also optimizes the separation efficiency of the filter unit 4 as well as the heat transfer in the biomass heating system 1.

[0101] In the event of cleaning the filter device 4, the electrode 45 is de-energized. The cage 48 preferably has an octagonal regular cross-sectional profile, as can be seen, for example, in the view of the Fig. 13 The cage 48 can preferably be cut using a laser during manufacturing.

[0102] After exiting the heat exchanger 3 (from its outlet), the flue gas flows through the reversing chamber 34 into the inlet 44 of the filter device 4.

[0103] The filter unit 4 is advantageously fully integrated into the boiler 11, so that the wall surface facing the heat exchanger 3 and flushed by the heat exchange medium is also used for heat exchange from the direction of the filter unit 4, thus further improving the efficiency of the system 1. This allows at least part of the wall of the filter unit 4 to be flushed with the heat exchange medium, and thus at least part of this wall to be cooled by boiler water.

[0104] At filter outlet 47, the cleaned exhaust gas flows out of the filter unit 4, as indicated by arrows S7. After exiting the filter, a portion of the exhaust gas is returned to the primary combustion zone 26 via the recirculation unit 5. This will be explained in more detail later. This exhaust gas or flue gas intended for recirculation can also be referred to as "recirculation" or "recirculation gas." The remaining portion of the exhaust gas is discharged from the boiler 11 via exhaust outlet 41.

[0105] Arrow S8 indicates a flue gas flow or turbulence in which the flue gas does not exit directly from filter 4, but instead forms a reverse or vortex flow in a dead volume of filter 4 (which, from a fluid dynamics perspective, is located downstream of outlet 47, meaning it is not in the main flow path S6, S7 through filter 4) and can, in particular, flow over the insulator 46. Soot and ash can then be deposited on the insulator. In addition to non-mineral combustion residues, carbonaceous combustion residues can also be deposited on the insulator, impairing its function. Further details on this will be provided in the following section. Fig. 9 explained.

[0106] An ash removal system 7 is located in the lower part of the boiler 11. An ash discharge screw 71 conveys the ash, which has been separated and falls out of the combustion chamber 24, the boiler tubes 32 and the filter unit 4, laterally out of the boiler 11.

[0107] In Fig. 2 and Fig. 3 Further sensors are shown that are at least communicatively connected to the control unit 100. These sensors record (physical and / or chemical) parameters of the biomass heating system 1.

[0108] An exhaust gas temperature sensor 111 is provided downstream of the outlet of the heat exchanger 3. This sensor measures the temperature of the exhaust gas or flue gas after it has flowed through the heat exchanger 3. This sensor 111 can preferably be used to control the temperature of the flue gas flowing into the filter 4 for filtration. This is particularly important for maintaining the maximum flue gas temperature for the filter 4, as described later.

[0109] The exhaust gas temperature sensor 111 can be a conventional temperature sensor or a PT-100 or PT-1000 sensor, which is either installed in the wall of the exhaust duct or protrudes into the exhaust duct. The exhaust gas temperature sensor 111 allows the temperature of the exhaust gas to be determined in degrees Celsius.

[0110] The exhaust gas temperature sensor 111 can be located, for example, before or after the optional filter unit 4. Similarly, the exhaust gas sensor 111 can be located before the exhaust gas outlet 41. Furthermore, more than one exhaust gas temperature sensor 111 can be provided to increase measurement accuracy or to provide measurement redundancy. For example, one exhaust gas temperature sensor 111 can be located directly after the outlet of the heat exchanger 3, and another exhaust gas temperature sensor 111 can be located after the filter unit 4.

[0111] Furthermore, at least one lambda probe 112 is provided. It is intended as a sensor for the lambda control of the biomass heating system 1. The lambda probe measures at least one physical / chemical parameter that enables control of the combustion process in the boiler 11. The lambda probe 112 enables measurement of the O2 content, or oxygen content, of the exhaust gas or flue gas after the combustion chamber 24.

[0112] A lambda sensor typically compares the residual oxygen content in the exhaust gas with the oxygen content of a reference, usually the current atmospheric or ambient air. From this, the air-fuel ratio λ (ratio of combustion air to fuel) can be determined and adjusted. Two measurement principles can be used: voltage of a solid electrolyte (Nernst sensor) and resistance change of a ceramic (resistance sensor).

[0113] In the present application in the biomass heating system, the lambda probe 112 can measure the oxygen content of the exhaust gas (for example in vol-%) and thus an optimal mixture can be regulated at the boiler 11, preferably by means of an AI model, in order to prevent an oversupply of cooling supply air or carbon monoxide (with unused residual calorific value) resulting from a lack of oxygen, which would "rob" the heating system of energy.

[0114] For at least one lambda sensor 112, in Fig. 2 Two possible installation positions have been proposed. One is located adjacent to inlet 33 of heat exchanger 3 (see below). Fig. 2 , top, middle) and the other is located in the exhaust gas outlet 41 and thus after the outlet of the heat exchanger 3 (cf. Fig. 2 , top right). In general, the lambda probe 112 can be located at any position in the exhaust gas duct of the boiler 11, as long as it can measure the exhaust gas or flue gas.

[0115] However, the greater the distance between the flame in the combustion chamber 24 and the lambda probe 112, the more difficult it becomes to control the boiler 11 due to the resulting dead time. Therefore, it is preferable to mount the probe as close as possible to the combustion chamber 24. The signal from the lambda probe 112 can be used by the control unit 100 to regulate, for example, the supply of primary air to the combustion chamber and the fuel feed rate.

[0116] Furthermore, an (optional) vacuum sensor 113 or differential pressure sensor 113 is provided. This vacuum sensor 113 measures the (negative) pressure in the combustion chamber 24, for example in the unit [mPas], or the differential pressure of the combustion chamber 24 to the ambient air pressure. The primary air (and optionally the secondary air) is drawn into the combustion chamber 24 for combustion via this vacuum.

[0117] Furthermore, an (optional) return (or supply) temperature sensor 114 or a heating water temperature sensor 114 is provided. This is provided, for example, in the return or supply line of a conventional water circulation device 14 and detects the temperature of the heating water in the water circuit in which the boiler 11 is located. The heat exchange medium 38 is preferably the heating water.

[0118] This allows the temperature of the heat exchange medium 38 inside or outside the boiler to be measured using the previously explained boiler temperature sensor 115 or the heating water temperature sensor 114 (preferably a return temperature sensor 114).

[0119] A fuel bed height sensor 116 (shown here in the figures without an exemplary mechanism) detects the height of the fuel bed 28 above the grate and thus a quantity of fuel, for example wood chips, on the grate 25. An example of such a sensor in mechanical design is described in EP 3 789 670 B1 in relation to its Fig. 17 and 18 described, to which reference is made. Alternatively, the fuel bed height sensor 116 can, for example, be provided as an ultrasonic sensor.

[0120] Furthermore, a combustion chamber temperature sensor 117 is provided. This sensor measures the temperature of the combustion chamber 24, for example in degrees Celsius. The combustion chamber temperature sensor 117 can be located at the outlet of the combustion chamber 24 or within the combustion chamber 24 itself.

[0121] It should be noted that the locations of the sensors of the Fig. 2 and 3The locations may also differ from those shown, as deemed sensible by an expert. For example, the combustion chamber temperature can also be measured at a different location.

[0122] The combustion chamber 24, as well as the geometry of the filter unit 4 and the upstream reversing chamber 35 of this embodiment, were calculated using CFD simulations. Furthermore, practical experiments were carried out to confirm the CFD simulations. The starting point for the considerations were calculations for a 100 kW boiler, although a power range of 20 to 500 kW was taken into account.

[0123] A CFD simulation (CFD = Computational Fluid Dynamics) is the spatially and temporally resolved simulation of flow and heat transfer processes. These flow processes can be laminar and / or turbulent, accompanied by chemical reactions, or involve a multiphase system. CFD simulations are therefore well-suited as a design and optimization tool. In the present invention, CFD simulations were used to optimize the fluid dynamic parameters in such a way as to solve the aforementioned problems of the invention. In particular, the mechanical design and dimensioning of the boiler 11, the combustion chamber 24, the secondary air nozzles 291, and the combustion chamber nozzle 203 were largely defined by the CFD simulation and also by associated practical experiments. The simulation results are based on a flow simulation that takes heat transfer into account.

[0124] The results of the CFD simulation illustrating the flow optimization of filter unit 4 are discussed later in relation to the Figuren 14 and 15 explained in more detail. (Filter unit 4)

[0125] The biomass heating system 1 described above is provided with a filter device 4, which is discussed in more detail below.

[0126] Fig. 4 shows a highlighted part of the filter unit 4 from a side view of the biomass heating system 1. Fig. 5 time the highlighted part of the filter device 4 of the Fig. 4 from a perspective view, from the side and from below.

[0127] In the Figuren 4 and 5A filter insert 451 is shown, which holds the spray electrode 45 approximately in the center of the tubular inner volume of the filter assembly 4. This filter insert 451 can be removed from and reinserted into the boiler 11 or the biomass heating system 1 as a single unit. This allows one of the core elements of the filter assembly 4 to be easily maintained (i.e., replaced or exposed for cleaning) and also installed with minimal effort during initial assembly. Figuren 4 and 5 The spray electrode 45 is in its rest position or in the rest state of the Figuren 16a and 16b and is not deflected, for example for cleaning.

[0128] The filter insert 45 holds in particular the elongated or rod-shaped spray electrode 45, which extends along its longitudinal axis LAE, which is located in the Figuren 4 and 5The spray electrode 45 is shown with the dashed line LAE. In cross-section F2, which is perpendicular to the longitudinal axis LAE, the spray electrode 45 has a cross profile or a cross-shaped profile.

[0129] Preferably, the spray electrode 45 is arranged such that its longitudinal axis LAE coincides at least approximately with a central axis of the tubular inner volume of the filter device 4. In this respect, the longitudinal axis LAE can also be understood as approximately the longitudinal (central) axis of the filter device 4. Directions that are perpendicular, in particular perpendicular, to the longitudinal axis LAE are hereinafter referred to as "transverse" or "radial".

[0130] The longitudinal center axis LAE also defines a rest position of the movably mounted spray electrode 45.

[0131] The spray electrode 45 is, in this case, an electrode with projections 457, which can also be colloquially referred to as a sawtooth electrode. Alternatively, it can be provided with non-triangular projections, for example, with fin-shaped or quadrilateral projections. In this case, the spray electrode has a plurality of triangular or sawtooth-shaped projections 457, each with a single tip at which a high electric field strength is generated when the spray electrode 45 is energized. These projections 457 extend transversely to the longitudinal axis LAE. The spray electrode 45 has a length EL, which can be dimensioned such that the electrode 45 extends over a significant portion (more than 50%) of the longitudinal extent of the filter device 4.

[0132] The spray electrode 45 has a plurality of laterally arranged tips or projections 457, each of which causes a local increase in the electric field strength in the electrostatic filter device 4.

[0133] The filter insert 451 further comprises the electrode holder 43, which can also be referred to as the filter insert cover 43, and the insulator 46 for holding the spray electrode 45. An insulator-side or proximal suspension element 452 connects one end of the spray electrode 45 to the insulator 46. An (optional) tip-side or distal spring element 453 can flexibly connect a filter tip 454 to the lower or distal end of the spray electrode 45. In other words, a suspension element 452 can be provided at one end of the spray electrode 45 and a spring element 453 at the other end of the spray electrode 45.

[0134] The electrode holder 43 or the filter insert cover 43 has a mounting plate 431 made of a conductive material, which is provided on the inside of the electrode holder 43. The mounting plate 431 is grounded and provides at least partial shielding to the outside. Furthermore, the electrode holder 43 can include insulation to provide thermal insulation for the filter assembly 4 or the tank 11. Additionally, a connection 421 for the electrode supply line 42 is provided on the outside of the filter insert cover 43.

[0135] The insulator-side suspension element 452 is preferably designed to be flexible, so that the spray electrode 45 is suspended in the filter device 4 in a way that allows it to vibrate or oscillate. This freedom of movement for oscillation is provided in the Fig. 4 indicated by the double arrow SCH. The spray electrode 45 is thus suspended in such a way that it can swing back and forth like a pendulum. The suspension element 452 allows movement of the spray electrode 45 at least in one plane (for example, the plane of the paper). Fig. 4 ), however, it is preferable (and for the explanations regarding the Figuren 16a (also desirable) that the suspension element 452 allows movement of the spray electrode 45 in several directions.

[0136] The suspension element 452 can, for example, be a joint or a coil spring. It is preferable that the suspension element 452 be a coil spring 452, which exerts a spring-like restoring effect on the spray electrode 45 towards its rest position or its rest state.

[0137] The spring element 453 is, for example, a coil spring that is provided at the distal end of the spray electrode 45. The coil spring can, for example, be made of spring steel.

[0138] The filter tip 454 is made of an insulating (preferably with a specific resistance greater than 10< 10 Ω·cm, better greater than 10< 13 Ω·cm, even better greater than 10< 16 Ω·cm) and heat-resistant material, for example PTFE (polytetrafluoroethylene, or Teflon) or PEEK (polyetheretherketone).

[0139] In particular, the filter tip can be made of a temperature- and chemically resistant plastic. This includes various plastics from the polyhaloolefin class.

[0140] The material of the filter tip 454 can be designed to be resistant to temperatures up to at least 200 degrees Celsius (preferably at least 250 degrees Celsius). Furthermore, the plastic of the filter tip 454 can be designed to be resistant to the chemical composition of the combustion gases.

[0141] Furthermore, the filter tip 454 can preferably be provided in a pin-shaped form with a conical or frustoconical end. The filter tip 454 can have a round cross-section.

[0142] In the view of Fig. 5 The arrangement of the spray electrode 45 with the filter insert 451 and in particular the cross profile of the spray electrode 45 can be seen three-dimensionally.

[0143] The Fig. 6 shows different views of the spray electrode 45 of the Fig. 5 , wherein individual parts of the spray electrode 45 are shown as electrode parts 45a, 45b, as well as a bottom view of the assembled electrode 45 from the direction F1 and a sectional view of the assembled electrode 45 along the section line F2.

[0144] The spray electrode 45 consists of a conductive material, preferably a metal.

[0145] The spray electrode 45 can be composed of two electrode parts 45a, 45b. These metal parts can preferably be designed to be identical in such a way that they can be inserted into one another by means of a recess 458 to form the spray electrode 45 with the cross profile. This simplifies manufacturing and reduces production costs, since two identical parts can be produced.

[0146] The electrode parts 45a, 45b can be manufactured from a sheet of metal using a laser cutting process.

[0147] The electrode parts 45a, 45b have projections 457 which are preferably arranged at regular intervals over the entire length EL (or more than 90% of the total length) of the spray electrode 45.

[0148] The electrode parts 45a, 45b can have a width (horizontally) of 20-35 mm. Furthermore, the electrode parts 45a, 45b can have a thickness of 1.5 mm to 4.5 mm, preferably a thickness of 2.5 mm to 3.5 mm.

[0149] The electrode parts 45a, 45b are therefore generally elongated, plate-shaped parts which are connected to each other (for example by welding) in such a way that they form a spray electrode 45 with a profile, for example a cross profile or a star profile.

[0150] The section view F2 of the Fig. 6 shows that the cross profile of the spray electrode 45 has projections which point in four directions and thus into the four main quadrants of the tubular inner volume of the filter device 4.

[0151] At the ends of the electrode parts 45a, 45b, a first and a second transition element 455, 456 are provided. These optional transition elements 455, 456 (the suspension element 452 and the spring element 453 could also be attached differently, for example, by direct welding) can be received in recesses at the ends of the spray electrode 455 and may, for example, have a bolt shape. The transition elements 455, 456 allow a more stable and simpler transition from the spray electrode with its profile, for example, to a coil spring, which the suspension element 452 and the spring element 453 can form. The transition elements 455, 456 can be made of a plastic, for example, Teflon, or of a metal. View F1 of the Fig. 6 The figure below shows that the transition element 456 is arranged within the electrode parts 45a, b.

[0152] The Figuren 7a bis 7d Alternative spray electrodes 45 with alternative (star) profiles are shown. The profiles are shown as cross-sections at the level of line F2 of the Fig. 6 depicted.

[0153] The spray electrodes 45 of the Figuren 7a bis 7d The basic structure of the spray electrode corresponds to the Figuren 5 and 6 , for example, all spray electrodes have 45 projections 457, which will only be discussed below as differences between the various spray electrodes.

[0154] Fig. 7a Figure 1 shows a first alternative spray electrode 45 with a star or Y-profile. Three electrode parts 45a, 45b, 45c can be connected to each other in a star shape, for example by welding, to form the first alternative spray electrode 45. The first alternative spray electrode 45 can thus be used analogously to the spray electrode 45 of the Figuren 5 and 6, a rod-shaped spray electrode 45 with projections, the field maxima of which are located in three directions. In other words, the Y-profile has three legs 45a, 45b, 45c.

[0155] The angle between the three electrode parts 45a, 45b, 45c in cross-section is preferably 120 degrees (+-10° manufacturing inaccuracy) in order to provide a symmetrical electrode 45.

[0156] This first alternative spray electrode 45 can, for example (not shown), also be made from a first electrode part 45a, which is bent by 120 degrees, and a second electrode part 45b, which is welded to the bend of the first electrode part 45a.

[0157] Fig. 7b Figure 1 shows a second alternative spray electrode 45 with a further star profile. Three electrode parts 45a, 45b, 45c can be connected in this electrode. For example, electrode part 45a can be a rod-shaped plate, and two further bent plates, electrode parts 45b and 45c, can be connected to it. Alternatively (not shown), the second alternative spray electrode 45 can also be made from more electrode parts, for example, four, five, or six. Fig. 7b Six thighs are shown.

[0158] The angle between the electrode parts 45a, 45b, 45c, ... in cross-section is preferably 60 degrees (+-5° manufacturing inaccuracy) in order to provide a symmetrical electrode 45.

[0159] The second alternative spray electrode 45 can thus be used analogously to the spray electrode 45 of the Figuren 5 and 6, a rod-shaped spray electrode 45 with projections, which provides its field maxima in six directions.

[0160] The dashed circle of Fig. 7b Figure 1 shows a preferred maximum extent or maximum extension of the spray electrode in a direction perpendicular to the longitudinal direction of the electrode 45. Thus, the maximum extension of all electrode parts 45a, 45b, 45c can preferably be identical, thereby promoting a field formation in the filter that is as uniform as possible.

[0161] Fig. 7c Figure 3 shows a third alternative spray electrode 45 with a further star profile. A plurality of plate-shaped electrode parts 45a, 45b, 45c can be connected to one another, for example by welding. Fig. 7c Five thighs are shown. Fig. 7d Three thighs are shown.

[0162] The angle between the electrode parts 45a, 45b, 45c, 45d, 45e in cross-section is preferably 72 degrees (+-5° manufacturing inaccuracy) in order to provide a symmetrical electrode 45.

[0163] The third alternative spray electrode 45 can thus be used analogously to the spray electrode 45 of the Figuren 5 and 6 , a rod-shaped spray electrode 45 with projections, which provides its field maxima in five directions.

[0164] Fig. 7d Figure 45 shows a fourth alternative spray electrode 45 with a star or Y-profile. Three electrode parts 45a, 45b, 45c can be connected in a star shape, for example welded, to an inner tube 45f to form the first alternative spray electrode 45. The fourth alternative spray electrode 45 can thus be used analogously to the spray electrode 45 of the Figuren 5 and 6, a rod-shaped spray electrode 45 with projections, which provides field maxima in three directions.

[0165] The angle between the three electrode parts 45a, 45b, 45c in cross-section is preferably 120 degrees (+-10° manufacturing inaccuracy) in order to provide a symmetrical electrode 45.

[0166] This fourth alternative spray electrode 45 thus has a core 45f, for example the inner tube 45f, and three electrode parts 45a, 45b and 45c attached to it, which are elongated and plate-shaped, and which each have projections 457 analogous to those of the spray electrode 45 of the Figuren 5 and 6 exhibit.

[0167] The spray electrode 45 of the Fig. 5 bis 7d has a cross-sectional profile with at least three legs to improve the field formation in filter 4.

[0168] With this design, the field as a spray electrode 45 achieves a compromise between a field that is as homogeneous as possible in the filter and a field with the strongest possible field strengths (and with disadvantageous pass-through points with very low field strength) compared to a conventional elongated plate electrode (with 2 strong field maxima on the two longitudinal edges) or also compared to a conventional wire or round rod (with uniform field strength, but low maximum field strength).

[0169] This is what the proposed spray electrodes 45 look like. Fig. 5 bis 7d Advantageously, a large number of local field maxima are provided, which, compared to usual solutions, keep the probability low that particles pass through field minima and through filter 4 without being influenced or filtered out by the field.

[0170] A special characteristic of the in the Fig. 5 and 6The advantage of the profile shown is that the projections and edges of the spray electrode 45 point in different directions, thus forming a more effective electric field within the tubular inner volume of the filter device 4. In the (in-house) prior art, the spray electrode consists of a simple plate electrode, meaning that the resulting electric field has preferred directions in one plane, and the electric field perpendicular to the plane of the spray electrode is weaker than in the plane of the plate. This conventional field configuration, in contrast to the one described here, leads to suboptimal filter efficiency.

[0171] Another effect is the feedback of the charged particles on the electric field. Since the charging time of the particles is relatively short compared to the deposition time in filter 4, a cloud of negatively charged particles is formed. These negatively charged particles (particle space charge) interact with each other on their way to the deposition electrode (repulsion of like polarity), thereby limiting the ion current. This is a general process that typically occurs to a small extent in electrical precipitators. However, at very high inlet concentrations, especially of fine particles, this particle space charge can become so strong that the corona discharge current drops to per mille values ​​of the clean gas current. This is known as corona quenching.

[0172] This problem is largely minimized or even avoided by choosing a suitable distance between the spray and deposition electrodes and by using the spray electrode 45 with a small corona cut-off voltage relative to the generated field strength (i.e., due to its design as a sawtooth electrode).

[0173] The Fig. 8a Figure 1 shows a side view of an insulator 46, which is suitable as a high-voltage insulator 46 for insulation against voltages of several kV or even several tens of kV and for use in the filter device 4 and is a feature of the biomass heating system according to the invention. Preferably, the insulator 46 is designed to provide insulation against a voltage of at least 40 kV, preferably at least 60 kV. Fig. 8b shows an excerpt of IS of the Fig. 8a . The Fig. 9 shows a side view of insulator 46 of the Fig. 8a together with a mounting plate 431, which can also be referred to as a mounting plate 431. Here, the vertical or longitudinal position of the insulator 46 is slightly different than in Fig. 3 This is a variant of the embodiment of Fig. 2 and 3 .

[0174] The insulator 46 has a column-shaped base form, which includes an internal, approximately centrally located or axial passage 469 for the passage of a pin-shaped or tubular high-voltage conductor to supply the spray electrode 45. Preferably, the central axis of the insulator 46 and the central axis of the passage 469 coincide. The insulator 46 has a plurality of (preferably umbrella-shaped or ring-shaped) ribs 461, recesses 462, flanks 463 of the ribs 461, a foot 464, a (proximal) end rib 467, a (distal or electrode-side) transition element 468 (preferably a bushing made of a heat- and chemical-resistant and insulating material, for example Teflon or PEEK), as well as frustoconical first intermediate parts 465 (also referred to as intermediate cone parts 465) and cylindrical second intermediate parts 466 (also referred to as intermediate cylinder parts 466) located between the ribs 416.

[0175] Thus, between each pair of adjacent ribs 461, which are approximately disk-shaped with their disk plane perpendicular to the central axis IMI of the columnar base, lie a first intermediate part 465 (intermediate conical part 465) and a second intermediate part 466 (intermediate cylindrical part 466). It should be noted that the above does not necessarily apply to all spaces between ribs 461 (as in Fig. 8a shown), but alternatively only a part of the spaces between each two adjacent ribs 461 may be designed, as in Fig. 8a shown. The central axis IMI can preferably coincide with the longitudinal axis LAE of the electrode 45.

[0176] The intermediate conical section 465 has an outer conical surface 4651 which is perpendicular to the (longitudinal) central axis IMI of the insulator 46. This surface is preferably arranged at an angle over its entire outer circumference within a range of 15 to 35 degrees. The intermediate cylindrical section 466 has an outer cylindrical surface 4661 which is at least approximately parallel to the central axis IMI.

[0177] As shown in the excerpt of the Fig. 8b As can be seen, the intermediate conical part 465 serves to distance the recess 462 from the passage 496 by at least the depth TI1, thus ensuring an effective thickness TI2 or minimum thickness TI2 of the insulator 46 to maintain the insulating capacity of the insulator 46 despite the presence of the recess 462. In other words, the intermediate conical part 465 ensures a sufficient depth for the recess 462 and its function (see later), while at the same time the thickness of the insulator 46 does not need to be excessive.

[0178] The depth TI1 is preferably at least 2 mm, better at least 3 mm, and particularly preferably at least 5 mm. The same applies to the radial height of the intermediate conical part 465 above the intermediate cylindrical part 466.

[0179] Recesses 462 abut directly on one side the lower flanks 463 of the ribs 461. Furthermore, the recesses 462 abut directly the sharp (i.e., >90-degree tip angle) end edges 4652 of the intermediate conical sections 465. These end edges 4652 are recessed relative to the outer diameter of the annular ribs 461. The end edges 4652 are preferably circular. The adjoining intermediate conical sections 465 also taper conically towards the electrode-side end of the insulator 62 or towards the next rib 461, such that the smallest diameter of the insulator TI2 at the transition to the next rib 461 corresponds approximately to the diameter of the insulator at the recesses 462. Preferably, the lower flanks 463 are concave, i.e., curved inwards (like a fillet). This extends the effect of the recess 462 to the area of ​​the flank 463, and parts of the flank also burn.the concave area is free and / or protected against soot infestation by field action.

[0180] The insulator 46 has at least 5 ribs. Preferably, the insulator 46 has six (6) to eight (8) ribs 461. Alternatively, the insulator 46 has eight (8) to ten (10) ribs 461.

[0181] The insulator 46 can be provided as a single piece or as a multi-piece, preferably three-piece (as shown, with a supplementary rib 467a, the column-shaped main part 46a, and the transition element 468). The main part 46a of the insulator 46 is preferably made of a conventional ceramic material used in high-voltage insulators. The supplementary rib 467a can also be made of ceramic, but alternatively, it can be made of a high-performance insulating plastic, such as Teflon or PEEK. The supplementary rib 467a provides a large-area widening of the insulator 46 and thus of the insulator section, without increasing its overall height. In this respect, the additional rib 467a serves to increase the insulation resistance of the insulator 46 in a space-saving manner. With the additional rib 467a, at least one further rib 461 (which would require an increase in the overall height) of the insulator 46 can be eliminated.

[0182] The transition element 468 is designed in the form of a bushing or tube and serves as the transition between the main part of the insulator 46 and the suspension element 452 of the spray electrode 45. Since the spray electrode 45 is struck or moved for cleaning, the transition element 468 also provides mechanical protection for the brittle ceramic of the main part 46a of the insulator 46, as the pivot point for a pendulum-like movement of the spray electrode 45 is located at the distal end of the main part 45a, thus resulting in a transverse load on the insulator 46. However, the transition element 468 can also be omitted, for example for cost reasons, and is therefore optional.

[0183] The high-voltage insulator 46 is used in the electrostatic filter 4 to remove small foreign particles such as dust from the combustion gases. The commonly used high-voltage insulators have a column-shaped base structure with ring-shaped ribs and serve to hold the electrode(s) subjected to high voltage inside the filter.

[0184] After such conventional insulators, including insulator 46, are exposed to the contaminated gas, they can easily become coated with a layer of dirt or foreign matter. Adhesion processes on the surface of insulator 46 at the temperatures within filter 4 and in the filter's electric field play a role in the formation of this foreign layer.

[0185] Combustion processes under partial load play a particularly important role, as they produce a relatively large amount of soot. This soot quickly forms a continuous layer of uniform thickness on the insulators exposed to the exhaust gas atmosphere, and soot has the property of being relatively conductive. Therefore, the resulting foreign layer is conductive and thus poses a clear problem for the insulator's function.

[0186] Leakage currents flow through a conductive foreign layer thus formed, which often contains soot from the combustion process, leading to permanent power losses in the electrical supply unit of the electrostatic filter.

[0187] This usually leads to electrical short circuits across the insulator occurring quite quickly, especially when the boiler is started up or during partial load operation, which places a considerable load on the high-voltage supply of the electrostatic filter.

[0188] Furthermore, the filter performance decreases in the case of shunt circuits due to voltage dips. The high-voltage system supplying power to filter 4 should ideally be able to operate during combustion without shunt circuits and with minimal high-voltage power losses.

[0189] The one in the Figuren 8a und 8b Based on the above considerations, the insulator shown is designed in such a way that power losses due to leakage currents are minimized through a kind of self-cleaning of the insulator surface, while at the same time keeping the size and material requirements of the insulator 46 small. In exhaust gases heavily loaded with combustion residues and especially soot, the insulator surface is quickly and uniformly coated with a layer of soot, which may also contain other foreign substances.

[0190] This coating, or soot layer, is geometrically interrupted or specially shaped in the area of ​​the recesses 462 when the system is in operation, i.e., when a high voltage of at least 20 kV is applied between the electrodes of filter 4. When voltage is applied, leakage currents flow in the coating, whereby the recesses 462 can be considered a series of resistors in the equivalent circuit diagram. Even if these leakage currents are only slight, strong electric fields of, for example, E ≥ 10 kV / cm are generated between the flank 463 and the end edge 4652 of the ribs 461. These fields are sufficiently large to repeatedly ignite surface partial discharges such as glow or arc discharges at this point.

[0191] The high potential differences required for this between the end edge 4652 and the flank 463 arise from locally increased coating resistances in the area of ​​the surface of the recess (which can each be considered as an individual resistance in a series of resistances). This is caused, on the one hand, by the locally reduced diameter of the insulator at this point, and on the other hand, by the lower coating thicknesses in the area of ​​the recesses 462, because the electric fields E essentially shield the volume of the recesses 462 even against a large accumulation of coating particles.

[0192] Incoming combustion residues or soot particles are deposited by the field forces either on the cylinder shell surface 4661 or on the outer surface of the ribs 12 before they reach the surface in the area of ​​the recesses 462.

[0193] The ignited surface partial discharges effectively burn off the soot that has accumulated in the area of ​​the recesses 462, despite the field shielding. Low average total power losses of just a few watts, e.g., 5 watts, are sufficient to heat the soot locally to temperatures on the order of 1000 °C. The primary reason for this is that the high voltage requirement of the burning surface partial discharge leads to a highly concentrated local conversion of the total power drawn from the insulator in the area of ​​the recesses 462. Furthermore, the energy conversion from electrical to heating energy occurs essentially within the coating itself. Leakage heat flows through heat dissipation and heat transfer, which would occur with external heating of the soot layer, are thus largely avoided.

[0194] Glow and arc discharges contribute to soot removal through different mechanisms. Fine soot deposits with a thickness of less than 0.5 mm are completely and almost without loss removed by a regularly occurring glow discharge with a power output of P = 1 watt. Ideally, the insulator surface is cleaned to a shine by the bombardment of ions accelerated during the glow discharge. Thicker soot deposits with a layer thickness greater than 0.5 mm, which can form with larger soot deposits, for example, when the boiler is operating under partial load, are, however, burned off more rapidly due to the high heat generated at approximately 3500 Kelvin at the cathode-side base point of an arc discharge from the end edge 4652 to the flank 463. Because of these temperatures, a heat-resistant material is required for the main body 46a of the insulator 46.

[0195] For the stable operation of the insulator 46, sufficient flashover resistance of the insulator is generally required. While this increases with the number of soot burn-off points (recesses 462), it is also necessary that the remaining portions of the insulator surface, located between the burn-off points, remain covered with the thinnest and most evenly distributed layers of soot possible. The contaminated insulator surface can then be compared to a series connection of gas discharge paths in the area of ​​the recesses 462 and ohmic resistances in the area of ​​the remaining surfaces, i.e., the surface of the ribs 461 and the cylindrical shell surface 4661 up to the base point of the surface partial discharge.

[0196] When localized surface discharges are ignited, the interposed carbon black deposits act as current-stabilizing series resistors in the equivalent circuit. If the ohmic resistance of these deposits is not sufficiently high, the current would continuously increase after the surface discharges are ignited due to the falling current-voltage characteristic of discharges. A steady propagation of the partial discharge on the insulator surface, and thus a flashover of the carbon black layer, would be the inevitable consequence.

[0197] The umbrella-like, ring-shaped ribs 461, when the diameter ratio of the rib outer diameter to the diameter of the intermediate cylinder part 466 is correctly dimensioned, achieve a maximum creepage distance for a given insulation length. Furthermore, the diameters of the stubs of the intermediate cylinder part 466 should be chosen to be as small as possible, and the carbon black layer thickness should be kept as small as possible. The length of the insulator is selected according to these parameters and dimensioned to minimize flashovers at a given operating voltage.

[0198] The design of the high-voltage insulator 46 specifically provides a mechanism for self-cleaning and protection of the insulator surface by means of an electric field. Additional cleaning devices for the insulator surface are therefore unnecessary. This makes it possible, in particular, to integrate the filter unit 4 into the boiler 11 in a space-saving (compact) manner, especially since the insulator 46 can be located in the flue gas-laden interior of the filter unit 4.

[0199] Only minimal energy losses are required to maintain the insulating capacity of the insulator through the repeated burning off of the soot. This energy loss is directly converted into heating energy for burning off the soot and is reduced to a minimum by the self-regulating nature of the self-cleaning mechanism.

[0200] The position of the insulator 46 in the exhaust gas flow is also an important parameter, not only to allow the aforementioned effects to be realized more effectively, but also to utilize the flow pattern in the filter 4 to maintain the functionality of the insulator 46. The electric field between the end edge 4652 and the flank 463 exhibits a certain repulsive effect on particles, although the exhaust gas flow can at least partially counteract this effect.

[0201] Accordingly, the Fig. 9 The flow pattern in the internal volume of the filter 4 is greatly simplified using flow arrows S7 and S8, which exemplify air flows within the filter 4 that may be loaded with soot.

[0202] The filter outlet 47 of the filter 4 is arranged such that it is located at a height or longitudinal position of the filter 4 that is (preferably completely) different from the height or longitudinal position of the main body 46a of the insulator 46. The relevant longitudinal direction, along which the height is measured, is indicated by the correspondingly labeled double arrow in the Fig. 9 specified (this applies analogously to the Figuren 2 and 3 ). Therefore, given the present vertical orientation of the filter 4, the filter outlet 47 of the filter 4 is arranged such that it is provided below the main body 46a of the insulator 46.

[0203] In other words, the main body 46a of the insulator 46 can be arranged such that it is not located in the area of ​​a main outlet flow S7 in the internal volume of the filter 4, the upper limit of which, for the sake of simplicity, is defined here by the arrangement of the opening of the filter outlet 47 of the filter 4 (see the upper long-dash-short-dash line in Fig. 9 ). In other words, at least the main body 46a of the insulator 46 (or of the entire insulator 46) is not in the (height) range (cf. the area between the upper and lower long-dash / short-dash lines in Fig. 9 ) of exit 47 ordered.

[0204] Thus, the outlet 47 with its opening is located entirely below the main body 46a of the insulator 46 when the filter 4 is arranged vertically. In an embodiment not shown, if the filter 4 were arranged horizontally, the outlet 47 with its opening would be located entirely laterally offset from the main body 46a of the insulator 46.

[0205] Furthermore, the insulator 46 is provided at one end of the filter 4, opposite the other end of the filter 4 with its filter inlet 44. The tubular inner volume 46b of the filter 4 has two ends, with the filter inlet 44 at one end and the filter outlet 47 at the other end, and at least the main body 46a of the insulator 46 (or even better, the entire insulator 46) is provided at the end of the filter outlet 47 such that it is arranged offset longitudinally from the opening of the filter outlet 47.

[0206] As a result, at least the main body 46a of the insulator 46 (or preferably the entire insulator 46) is not arranged in the main flow S6, S7 between filter inlet 44 and filter outlet 47.

[0207] Initially, the insulator 46 is located in a position where the flue gas has already been largely filtered. Therefore, the exposure of the insulator 46 to soot during normal or full-load operation is significantly reduced, since the insulator 46 is positioned after the filtering stage, thus already reducing the soot load in the flow.

[0208] Furthermore, optionally, as in the Fig. 9 As shown, the arrangement of the insulator 46 at the top end of the filter also contributes to the fact that it is less exposed to soot or particles, since (with this vertical arrangement of the filter 4) gravity can simply contribute to the fact that, at low airflows (especially at low partial loads), the soot statistically tends to remain in the lower part of the filter 4 or is sucked out of the filter 4 via the main flow S7.

[0209] In essence, with the arrangement described above, at least the main body 46a of the insulator 46 (or even the entire insulator 46) lies in a dead volume in which eddy currents S8 occur to a lesser extent and therefore the particle or soot load is lower.

[0210] The ribs 461 can also serve as umbrella-like flow deflectors for the flue gas flow, potentially diverting larger portions of the vortex flow S8 away from the recesses 462. This allows the effect of the electric field at the trailing edge 4652 to be more pronounced on the flank 463. Therefore, it is advantageous that the recesses 462 are located directly below the ribs 461.

[0211] Because at least the main body 46a of the insulator 46 is not located in the main flow S6, S7 between filter inlet 44 and filter outlet 47, the particle or soot load with which the insulator 46 is subjected decreases. In In other words, this arrangement saves time until the cleaning of insulator 46 is carried out.

[0212] Fig. 10 shows a highlighted perspective view of the Fig. 8a from a slightly elevated angle. This is intended to show the geometries of the Fig. 8a, 8b and 9This will be clarified again. Furthermore, the mounting plate 431 is two-part and slotted, and features a maintenance opening from above. However, this design is optional.

[0213] To better discuss the control of biomass heating system 1, the following refers to Fig. 11 a combustion operation or an operating procedure of the biomass heating plant 1 is explained. (Operating procedure for biomass heating plant 1)

[0214] Fig. 11 shows a general operating procedure of the biomass heating plant 1.

[0215] After the combustion process has started, usually by switching on the biomass heating system 1 by a user or by an external automatic system, the combustion process can initially be prepared in the optional step S50.

[0216] During the preparation of step S50, the biomass heating system can be mechanically and electronically initialized. For example, the operating system of the control unit 100 boots up, a self-test of the electronics is performed, and / or the rotary grate elements 252, 253, 254 are rotated (opened) by a predetermined angle to remove any deposits on the grate and to test the mechanics before combustion. During such a mechanical test of the rotary grate 25, the rotary encoder sensors can be used to check whether controlling the motors 231 of the rotary mechanism produces the desired result or whether something is blocked. Furthermore, the mechanical boiler cleaning (via tubulators), ash removal, and the optional electrostatic precipitator cleaning can be operated for a predefined time (e.g., 30 seconds). The air passages of the boiler 11 can also be purged.For this purpose, the biomass heating system is purged with air by opening the primary and secondary air valves. Then the air dampers are closed and the flue gas recirculation line is purged.

[0217] In the next step S52, the combustion chamber 24 is filled with fuel. The fuel is conveyed via the fuel feed 6 onto the rotary grate 25 until a predetermined fuel bed height is reached. This fuel bed height is measured using the fuel bed height sensor 116. The fuel bed height sensor 116 is, for example, a mechanical leveling flap 86 with a rotary angle sensor.

[0218] Next, the fuel is ignited in step S52. This can also be referred to as the ignition phase. Energy is supplied to the fuel via the ignition device 201 until it ignites. Furthermore, the valves or valve positions can be adjusted during fuel ignition to facilitate ignition. During ignition, the blower 15 is also activated to create a corresponding vacuum in the combustion chamber 24. The primary and secondary air valves can be set to predefined values ​​(e.g., 60% and 15%), and a predefined vacuum is established in the combustion chamber (e.g., 75 Pa).

[0219] Once the biomass heating system 1 reaches a predetermined combustion chamber temperature (e.g., 50°C) and / or a predetermined lambda value (e.g., 17%), it transitions to step S53, the combustion stabilization phase. In this step, also known as the stabilization phase, ignition of the fuel bed is further promoted. Accordingly, the positions of the air valves 52, the function of the blower 15, and the fuel supply are adjusted. During this process, the boiler 11 and the combustion chamber 24 should continue to heat up. Preferably, the combustion process should gradually transition into a steady state, in which thermodynamic equilibrium prevails. Step S53 is completed when the combustion temperature rises to a predetermined value, for example, 400°C.

[0220] Accordingly, the process proceeds to step S54: stabilized combustion and the actual heating operation. In this step S54, the power output or combustion intensity is controlled by means of the fuel supply 6, the blower 15, the position of the valves 52, and other actuators based on sensor data from sensors of the biomass heating system 1, for example, based on the combustion chamber temperature, the lambda value, and / or the boiler (water or medium) temperature. Fuel-dependent power control can be used here.

[0221] Step S54 is terminated when, for example, sufficient heat output has been provided and / or complete combustion of the fuel in boiler 11 has been detected and calculated.

[0222] In step S55, the combustion chamber 24, and in particular the rotary grate 25, undergoes a burn-off process. During this process, the fuel supply is stopped and the combustion chamber temperature drops. The remaining fuel on the rotary grate 25 is then burned. The positions of the valves 52 and the blower 15 can be adjusted accordingly for this purpose. At the end of the burn-off process, the rotary grate 25 is cleaned by rotating or opening the grate elements.

[0223] After completion of step S55, the procedure can be deactivated (END), or after some time the procedure can proceed again to step S50, thus starting a new heating cycle. (Control procedure for filter unit 4)

[0224] The Figuren 12a , b , c and dThe figures show various methods for controlling the filter unit 4, which can be used together or individually. These methods can be integrated into the operating procedure of the biomass heating system 1 and are used depending on the operating state of the boiler 11. The method of Fig. 12d Furthermore, it can be used in any operating state of filter 4 if boiler 11 is active, in order to prevent damage to the biomass heating system 1.

[0225] Filter unit 4 has either a separate control unit or its own controller for regulating filter unit 4, or filter unit 4 is controlled via the control unit 100 explained above.

[0226] In general, it can be assumed that the control unit (100) and thus the procedures are set up in such a way that the operating state of the biomass heating plant 1 (see steps S50 to S55 of the Fig. 11 ), and at least one of the parameters of the filter voltage Vf [kV], the filter current If [µA], the filter power Wf [W], the filter status Sf [On / Off] and / or the boiler output Wk [kW] are recorded and thus known. Furthermore, the control device or the procedures are configured such that they can set the filter status [On / Off] and at least the parameter of the filter voltage Vf [kV] can be set. The various filter voltages Vf of these procedures denote the voltage applied to the spray electrode with respect to the counter electrode or ground.

[0227] Fig. 12a shows a method for controlling the filter device 4 during the stabilization S53 of the combustion, i.e. a filter stabilization control method HO.

[0228] Step S60 checks whether boiler 11 is in operation. Only if so does the procedure begin with step S61.

[0229] Step S61 checks whether boiler 11 is in the combustion stabilization state (S53) or not. If not, S61 is repeated at regular intervals. If it is, the procedure continues with step S62.

[0230] In step S62, a preset voltage Vmin of filter 4 is set as the specified minimum voltage of filter 4. Vmin can be, for example, 30 kV. This voltage is therefore the starting voltage of filter 4.

[0231] Then, in step S63, the voltage of filter 4 Vf is gradually increased by a predetermined voltage ramp value Vew over a specified time interval Terh. The time interval Terh can be, for example, one minute. The voltage ramp value Vew can be, for example, 500 V. Thus, the filter voltage increases via a (voltage ramp) of 500 V per minute. This ramp can be defined as power-dependent with respect to the boiler output. If boiler 11 is operating at maximum output, for example, the voltage ramp value can be defined as lower than if boiler 11 is only operating at partial load, since higher soot emissions are to be expected at partial load.

[0232] After step S63, step S54 checks whether the filter voltage Vf has reached a predefined maximum voltage Vmax. Vmax can be, for example, 48 kV or 60 kV. If the filter voltage Vf has not reached its maximum voltage Vmax, the process returns to step S63. If the filter voltage Vf has reached its maximum voltage Vmax, the process continues with step S65 and maintains the filter voltage Vf at the maximum voltage Vmax.

[0233] At S66, the system checks again whether the boiler's operating state is in the combustion stabilization state (S54) or not. If this is no longer the case, the process ends. If it is, the process continues with step S65 and maintains the filter voltage Vf at the maximum voltage Vmax.

[0234] In the next step, S66, as in step S61, it is checked whether the operating state of boiler 11 is in the combustion stabilization state (S53) or not. If this is not the case, S65 is repeated, i.e., the maximum voltage is maintained. If this is the case, the procedure ends.

[0235] This ramp-up of the filter voltage Vf serves to adapt the filter's effectiveness to the combustion processes during the combustion stabilization phase, in which the flue gas typically contains more combustion residues, and higher boiler temperatures and thus flue gas velocities are to be expected due to the boiler output exceeding the desired setpoint. In this respect, this control system takes into account the specific conditions and requirements of the combustion stabilization phase.

[0236] Fig. 12b shows a method for controlling the filter device 4 during combustion S54 (in normal combustion operation of the boiler 11), i.e. a filter combustion control method VR.

[0237] Step S70 checks whether boiler 11 is in operation. Only if so does the procedure begin with step 71.

[0238] In the following step S71, it is checked whether the boiler's operating state is in the combustion stabilization state (S61) or not. If this is not the case, S71 is repeated at regular time intervals. If this is the case, the procedure continues with step S72.

[0239] In step S72, the voltage Vf of the filter is regulated as a function of the boiler output according to a predefined function Vf = f(boiler output).

[0240] This function f(boiler output) can, for example, be a linear function in which, within a predefined power range (e.g., 30% to 70%), a linearly increasing control of the filter voltage Vf is carried out from a predefined minimum voltage Vfmin to a predefined maximum voltage Vfmax.

[0241] The function Vf can alternatively consist of a predefined table in which 11 predefined filter voltages Vf are specified for certain power values ​​(or value ranges) of the boiler.

[0242] After step S72, step S73 checks whether the boiler is still in the combustion state (S54) or not. If the boiler is in the combustion state (S54), the process returns to step S72 and continues the load-dependent control of the filter voltage Vf.

[0243] If the boiler operation is no longer in the combustion state (S54), the filter combustion control procedure VR is terminated.

[0244] Such a VR regulation saves energy (filter power) and places less strain on the power source of the filter voltage Vf, since the regulation of the filter voltage Vf is demand-dependent.

[0245] The procedure of Fig. 12b This option can only be performed if at least one predefined fuel type, such as pellets, is detected for combustion in boiler 11. If fuel types other than the predefined one are detected, the filter voltage Vf can be regulated differently; for example, a fixed voltage can be set. Consequently, if wood chips are detected, the filter voltage Vf can be set to a fixed value, such as 45 kV.

[0246] Fig. 12c Figure 55 shows a method for controlling the filter device 4 during the burn-out process, i.e., a filter burn-out control method.

[0247] Step S80 checks whether boiler 11 is in operation. The procedure only begins if it is.

[0248] Step S81 checks whether the operating state of boiler 11 is in the burnout stabilization state (S55). If not, S61 is repeated at regular intervals. If it is, the procedure continues with step S82. In this step, a preset voltage Vmin of filter 4 is set as the specified minimum voltage Vmin of filter 4. Vmin can be, for example, 30 kV. This voltage also serves as the starting voltage for a ramp to increase the filter voltage Vf (see the following steps).

[0249] Then, in step S83, the filter voltage Vf is gradually increased by a predetermined voltage increase value Vew1 over the specified time interval Terh1. The time interval Terh can be, for example, one minute. The voltage increase value Vew can be, for example, 500V. Thus, the filter voltage Vf increases via a (voltage increase) ramp of 500V per minute. This ramp can be defined as power-dependent with respect to the boiler output. If boiler 11 is operating at maximum output, for example, the voltage increase value can be defined as lower than if boiler 11 is only operating at partial load, since higher soot emissions are to be expected at partial load.

[0250] After step S83, step S84 checks whether the filter voltage Vf has reached a predefined maximum voltage Vmax. Vmax can be, for example, 48 kV or 60 kV. If the maximum voltage Vmax is not reached by the filter voltage Vf, the procedure returns to step S82. If the maximum voltage Vmax is reached by the filter voltage Vf, the procedure continues with step S85 and maintains the filter voltage Vf at the maximum voltage Vmax.

[0251] At S86, the system checks again whether the boiler's operating state is in the burn-off stabilization phase (S55). If this is no longer the case, the process ends. If it is, the process continues with step S85 and maintains the filter voltage Vf at the maximum voltage Vmax.

[0252] Depending on the composition of this dirt layer, i.e., depending on the type and quality of the combustion process in the combustion chamber, the threshold for the ignition of surface discharges is lowered. These surface discharges typically occur only briefly, as the voltage dips that occur during these discharges, caused by the limited capacity of the high-voltage system, interrupt them. The above method allows the insulator 46 to be selectively cleaned by burning off the dirt, since increasing the filter voltage Vf raises the threshold for the ignition of surface discharges, thus enabling these discharges to become effective.

[0253] Fig. 12d This document describes a method for controlling the filter unit 4 during operation to prevent breakdowns in the filter 4, thus a filter breakdown control method DU. This method serves to protect the biomass heating system 1, in particular the filter unit 4 and the control unit 100, from overload and damage. Therefore, this method takes precedence over the methods of Fig. 12a bis 12c . Therefore, the predefined maximum voltage Vmax of the methods of 12a to 12c can be "overwritten" or temporarily reduced using this method.

[0254] Step S90 checks whether boiler 11 is in operation. The procedure only begins if it is.

[0255] At step S91, at least one of the [items] is [incomplete]. Fig. 12d The following conditions are queried: 1) Does the filter current If exceed a predefined maximum permissible filter current (e.g., 5000 µA) or 2) does the filter voltage Vf drop below a predefined minimum voltage Vfmin of the filter (e.g., 15 kV)? However, the maximum permissible filter current and / or the predefined minimum voltage Vfmin of the filter can be predefined differently depending on the operating state (S53, S54, S55) (not shown). For example, when burning off the soot from boiler 11, the insulator 64 should also be burned off. For this purpose, a more generous design of the upper limit of the filter current If or the minimum voltage Vfmin of filter 4 is generally desirable to improve the burning off of the insulator 64.

[0256] If this is not the case, i.e., the query at S91 is negative, no action is required and step S91 is repeated.

[0257] If this is the case, i.e., if the query at S91 is positive, a breakdown or short circuit in filter 4 has been detected. Such a breakdown could, for example, be a flashover from the spray electrode 45 to the counter electrode 48 or a flashover across the insulator 46.

[0258] If the query at S91 is positive, then at S92 the maximum voltage of the filter Vfmax is temporarily reduced (e.g., for 10 minutes) by a voltage reduction value Vvw (e.g., 1 kV). This regulates the filter voltage Vf to a breakdown-free maximum, thus preventing damage while simultaneously maximizing the filter's effectiveness (particle removal and insulator erosion).

[0259] Alternatively, the filter voltage Vf can be set to zero for a predetermined period of time.

[0260] The procedure of Fig. 12d This can be done, for example, using the methods of Fig. 12a and / or 12b and / or 12c can be combined.

[0261] Furthermore, the filter penetration control method DU can be used by the Fig. 12d It includes a time component not shown there. This time component can consist of recording whether there was a predefined number of copies (i.e., S91: Yes) within a predetermined period. If this number of copies (e.g., 5) is exceeded, it is assumed that there is a fundamental problem with filter 4, and filter 4 is deactivated (filter status Sf: Off).

[0262] Furthermore, regarding the procedures of Fig. 12a bis 12c For example, if a breakdown is detected, the respective procedure can be restarted. In this respect, the ramps for increasing the filter voltage Vf can be restarted from the minimum voltage.

[0263] The separation efficiency of an electrostatic filter device depends primarily on the voltage between the spray and separation electrodes. However, a high voltage introduces the problem of electrical flashovers within the electrostatic filter device 4. The formation of electrical flashovers in the filter is promoted by the deposition of conductive combustion residues, such as soot. Furthermore, it is desirable to keep the overall size of the electrostatic filter device 4 as small as possible, which means minimizing the insulation distances and the size of the insulator. The control methods described above take these circumstances into account.

[0264] In summary, the filter control described above can fulfill the following functions: Burn-off of the insulator 46 during the burn-off of the biomass heating system 1, taking into account the capacity of the power supply or control unit 100 of the filter unit 4. Burn-off of the insulator during the stabilization of the combustion process, taking into account the capacity of the power supply or control unit 100 of the filter unit 4. Regulation of the electrode voltage Vf to the maximum possible value – just below the voltage breakdown but without a permanent breakdown, thus achieving a sufficient spray current even during combustion. General protection of the filter unit 4 by limiting the current to predetermined current values. Determining the breakdown limit, detecting a breakdown, differentiating between different types of breakdowns and reacting to them. Detecting back-spraying that occurs with high-resistance dusts and reacting to it.

[0265] Furthermore, functions for detecting the type of breakdown can be subordinated: If a breakdown is detected, the ramp-up can be aborted, the high voltage can possibly be set to zero for deionization for a predetermined period, and a new ramp-up is started, possibly with lower maximum voltage values.

[0266] Fig. 13 Figure 1 shows a power diagram, a voltage diagram, and a current diagram with a common time axis for an exemplary combustion cycle of biomass heating system 1 from ignition (S52) to burnout (S55). For the sake of simplicity, the preparation (S50) and filling (S50) processes are omitted here.

[0267] In the performance diagram of the Fig. 13 Arrow S52 roughly indicates the process of (re)igniting the fuel. The fuel ignites, and the output rises rapidly due to the remaining unburned fuel. Around the area indicated by arrow S53, the combustion process stabilizes, and after some fluctuation, the output stabilizes at the desired target value. Around the area indicated by arrow S54, the (stabilized) combustion process takes place, resulting in a relatively constant output from boiler 11. At approximately S55, the biomass heating system undergoes a burn-out phase, accompanied by a peak in output. This cycle then ends, and the output decreases.

[0268] The filter voltage Vf (i.e., the voltage applied to the spray electrode 45) is shown in the voltage diagram, and the filter current If flowing in filter 4 due to the applied filter voltage Vf is shown in the current diagram, representing the result of the control procedures of the Fig. 12a bis 12d are.

[0269] The arrows labeled HO1 and HO2 point to exemplary control results in voltage and current of the filter stabilization control method HO.

[0270] During combustion stabilization, normal combustion operation is prepared by gradually increasing the filter voltage Vf to promote or enable the cleaning of the insulator 56. During combustion stabilization, increased, often bulk-forming soot loads occur in the combustion air, which are countered by increasing the filter voltage Vf via the voltage ramp up to the breakdown limit.

[0271] The arrows labeled ABB1 and ABB2 point to exemplary control results in voltage and current of the filter burnout control procedure ABB. To burn off the conductive deposits on the insulator 46, the voltage Vf is increased in a ramp-like manner to induce a smoldering fire on the insulator 46.

[0272] The arrows labeled VR1, VR2, and VR3 point to exemplary (section-by-section) control results in voltage and current of the filter combustion control method VR. At these points, the filter voltage Vf correlates approximately linearly with the boiler output and is characterized by various outliers (e.g., passing bulk-like particle accumulations or breakdowns).

[0273] The arrows labeled DU1, DU2, and DU3 indicate the points where the filter breakdown control method DU is used. At DU1, the filter voltage Vf has fallen below the preset minimum voltage Vfmin, thus indicating a breakdown. As a result, the voltage ramp for the filter stabilization control method is activated. Fig. 12a The test was restarted with the minimum voltage Vfmin. DU2 experienced a single breakdown due to exceeding a maximum current of 5000 µA. The filter voltage Vf was set to zero for a predetermined period (one minute), thus resolving the issue associated with the breakdown. DU2 experienced several breakdowns, but the number of breakdowns per unit of time was not yet sufficient to permanently deactivate filter 4. Therefore, the filter was simply set to zero several times for a predetermined period (one minute). DU4 experienced a voltage drop below the minimum filter voltage Vfmin during the insulator burn-off or the burn-out of boiler 11. This can occur, for example, if soot detaches in bulk from combustion chamber 24 or heat exchanger 3.In this case, the filter voltage Vf was set to zero for a predetermined period (1 minute), and the voltage ramp was restarted at the minimum voltage according to the ABB filter burnout control procedure. This results in another attempt to burn off the insulator 46.

[0274] Fig. 14 shows a cross-section through the biomass heating system of the Fig. 2 with the result of a CFD temperature simulation, which was combined with practical measurements on a prototype of the biomass heating plant 1 of the Fig. 2 verified at 100 kW (with a maximum boiler output of 120 kW).

[0275] Fig. 15 shows a cross-section through the biomass heating system of the Fig. 2 with the result of a CFD flow simulation, which is combined with the CFD temperature simulation of the Fig. 14 corresponds, whereby the CFD flow simulation is combined with practical measurements on a prototype of the biomass heating plant 1 of the Fig. 2verified at 100 kW (with a maximum boiler output of 120 kW).

[0276] The individual features and components of the biomass heating system 1 of the Figure 14 and 15 correspond to those of Figures 2 and 3 , which is why these are omitted for the sake of clarity. Figure 14 and 15 show velocity and temperature distributions in the internal volume of the boiler 11 (e.g. the combustion chamber, the heat exchanger 3 and the electrostatic filter device 4) using isosurfaces in shades of gray.

[0277] Individual characteristic points of the simulation and the measurements are in the Figure 14 and 15 explicitly given as "approx.'" values.

[0278] The so-called particle transport in an electrostatic filter device depends on the applied electric field, as well as on the flow dynamics (e.g. the residence time of the particle in the electric field) of the flowing gas and the dust to be separated.

[0279] This flow dynamics is strongly determined by the geometry of the filter unit 4 and the flue gas routing in the boiler 11. Furthermore, the electrical conditions are determined in particular by the geometry of the separation and spray electrode.

[0280] In order to increase the residence time of the flue gas in the filter 4, the flue gas routing in the boiler 11 is arranged such that the flue gas velocity in the filter device 4 is below 2 m / s, preferably below 1.5 m / s.

[0281] To achieve this flow velocity, the boiler 11 or the heat exchanger is equipped with special turbulators 35, 36 developed using CFD simulations as flow brakes 35, 36, which also promote heat exchange in the heat exchanger.

[0282] The above ensures that, during nominal load operation of the 100 kW boiler, a heat exchanger outlet temperature of a maximum of 180°C, preferably a maximum of 160°C, can be achieved, resulting in an inlet temperature to the filter of a maximum of 170°C, preferably a maximum of 150°C. This is also confirmed by the results obtained in the Fig. 14 are specified. In general, the temperature of the flue gas at the filter inlet 44 during full load operation of the biomass heating system 1 should be less than 220°C, preferably less than 200°C, in order to optimize the filter effect.

[0283] Furthermore, the flue gas routing in boiler 11 is designed such that the flue gas velocity at the filter inlet is a maximum of 2 m / s, preferably a maximum of 1.8 m / s, or lies within a range of 1 to 2 m / s. At boiler outputs of 70 kW (i.e., in partial load operation), this flue gas velocity is reduced to a maximum of approximately 1.2 m / s, preferably a maximum of 1.0 m / s.

[0284] Optionally, the reversing chamber 35 and the filter inlet 44 can also be designed to further slow the flow during full-load operation. For example, flow guide plates or braking flows can be provided.

[0285] Furthermore, the turning chamber 35 and the filter inlet 44 can be designed in such a way that the flow into the filter 4 is homogeneous.

[0286] This also allows for a more uniform flow into filter 4, thereby reducing velocity peaks in the inlet area and in the ash screw area. This improves ash settling and reduces ash resuspension from the turning chamber 35. Furthermore, a uniform flow profile at the inlet is important to prevent stringing in the electrostatic precipitator.

[0287] Furthermore, boiler operation can be regulated in such a way that, based on the data relating to Fig. 2The sensors described above regulate the operating state of the biomass heating system 1 in such a way that the flow velocities and temperatures described above are achieved. Optionally, additional sensors, not explicitly mentioned herein, may be present to further regulate the operating state of the biomass heating system 1 to the aforementioned temperatures and flow velocities.

[0288] In In other words, the biomass heating system 1 can be regulated in such a way (for example, the air supply to combustion or the power of the induced draft fan or ventilator) that the filter is operated at least during combustion S54 in the above-mentioned physical ranges with regard to temperature and flow velocity. (Filter cleaning)

[0289] Another problem arises from the layer of dust or particles that accumulates on the electrodes during operation. These particles, as combustion residues, contain mineral and carbonaceous components, resulting in a significant electrical resistance. The problems caused by the deposition of conductive residues on the insulator 46 have already been discussed in relation to the Figs. 8a and 8b explained in more detail.

[0290] However, these problems are not the only ones caused by deposits in filter 4. The charge of the deposited particles and the incoming ion current must dissipate through the dust layer of already deposited particles on the electrodes (spray and collecting electrodes). This can lead to a relatively large voltage drop across the dust layer, which can ultimately result in a corona discharge within the dust layer. This generates charge carriers of both polarities, leading to an ion current flowing in the opposite direction to the collection current, towards the spray electrodes. In some cases, flashovers also occur within the already deposited dust layer, which, like an explosion, hurls dust back into the gas stream. This effect is called "back-corona" and leads to a reduction in particle transport velocity and a decrease in filter efficiency.

[0291] The problem of reentrainment persists. Reentrainment refers to the carrying over of already separated dust with the gas flow. The majority of reentrainment occurs when the electrodes are tapped (so-called knock losses). Reentrainment from tapping the electrodes is avoided or at least reduced in this case by either completely stopping boiler operation (i.e., tapping is performed after combustion has ceased) or by briefly deactivating blower 15 during tapping.

[0292] However, even during normal separation operation, reentrainment losses occur from the dust layer. These are referred to as erosion losses. In this case, reentrainment is counteracted by the design of the electrostatic filter device. Firstly, the volume at the top of the electrostatic filter device 4 around the insulator 46 serves as a trapping chamber in which incoming particles are forced to reverse direction and are thus captured within the volume of the filter device 4 before they exit the filter device through the outlet 47. This fluid dynamic mechanism is related to Fig. 9 (see flow arrow S8) described, to which reference is made.

[0293] Therefore, it has been shown that mechanical cleaning of both electrodes 45, 48 is necessary to ensure long-term stable operation of the filter device 4.

[0294] This mechanical cleaning is in relation to the Figures 16a to 20b described in more detail. Figures 16a to 20b Each shows sections of the embodiment of the Figure 1 ff. in various states. Identically represented features of the Figures 16a to 20b correspond to those of Figure 1 ff, which, for the sake of clarity, means that many reference symbols are not shown again, but are nevertheless sufficiently disclosed to the person skilled in the art. The states of the Figures 17a to 20b represent a temporal sequence of a cleaning process of the filter device 4 in the order of these figures.

[0295] The Fig. 16a shows a three-dimensional sectional view into the filter unit 4 of the biomass heating plant 1 from the rear (i.e., from a direction opposite to arrow V of the Fig. 1 is) in a resting state of cleaning. The Fig. 16b shows a flat cross-sectional view of the filter unit 4 of the biomass heating system 1 from the rear in a resting state of cleaning.

[0296] In this resting state, the spray electrode 45 (which is itself inflexible and suspended from the insulator 46) hangs downwards with the LAE axis as its axis of rest. The suspension element 452, in this case a spring, is also at rest and thus exerts no actuating force on the electrode 45. The spring element 453 and the attached filter tip 454 are also at rest and aligned with the LAE axis.

[0297] This standby state is the standard state during the combustion operation of boiler 11. The electrode 45 is energized, the filter 4 exerts an electrostatic cleaning effect, and both the spray electrode 45 and the precipitation electrode 48, or cage 48, become coated with flue gas residue. Residue also accumulates on the inner wall of the filter 4 and on the insulator 46.

[0298] The Fig. 17aFigure 1 shows a three-dimensional sectional view of the filter unit 4 of the biomass heating plant 1 from the rear in its first cleaning state. Fig. 17b shows a flat sectional view of the filter unit 4 of the biomass heating system 1 from the rear in the first cleaning state.

[0299] Filter 4 is typically cleaned after the boiler has been run through a burn-off cycle (S55). It can also be cleaned manually, or – if necessary – during combustion operation.

[0300] In the first cleaning state, the current to the electrode 45 is deactivated. A (preferably two-armed) striking lever 96 with a conical striking head is driven by a (not shown) motor, which is driven by a (also not shown) transmission mechanism by a axis of rotationThe SDREH is deflected in the direction of arrow FE1. Simultaneously, cage 48 can (optionally) be raised to clean the inner walls of filter 4, thereby scraping off deposits from the inner walls.

[0301] The Fig. 18a The figure shows a three-dimensional sectional view of the filter unit 4 of the biomass heating plant 1 from the rear in a second cleaning state. Fig. 18b shows a flat sectional view of the filter unit 4 of the biomass heating system 1 from the rear in the second cleaning state.

[0302] In this second cleaning state, the impact lever has been deflected further in the direction of arrow FE2. Because the path of the stop head 97 passes through the position of the filter tip 454 (and optionally also through the position of the spring element 453), the electrode 45 is deflected laterally (towards V (front) of the vessel 11) and, due to gravity and optionally due to the restoring force of the suspension element 452, returns to its rest position along the LAE axis. This movement is indicated by the double arrow FE3. In this case, after oscillating in the direction of the double arrow FE3, the electrode 45 has returned to its initial position.

[0303] During this initial movement of the striking lever 96, the electrode 45 is deflected in a first direction and back (see double arrow FE3), which is perpendicular to the direction of movement of the striking lever 96. This is due to the conical shape of the striking head, whose surfaces, arranged perpendicular to the direction of movement of the striking lever 96, cause a similarly perpendicular movement of the electrode 45.

[0304] Even during this process, residues are tapped off the electrode 45, with the force acting on the electrode 45 occurring in this initial direction. This can be illustrated in relation to the electrode 45 of the Fig. 6(cf. view F2), it becomes clear that such a directed force causes a tapping action on the electrode surfaces 45 in a preferred direction. This preferred direction is characterized by the fact that a tapping force direction perpendicular to the electrode surface is more effective than a force direction parallel to the surface.

[0305] In other words: Since electrode 45 of the Fig. 6 Since the surfaces have two main directions, by tapping in the first direction those surfaces with the main direction perpendicular to the force direction of the tapping, i.e. a first part of the surfaces of the electrode 45, are preferably cleaned.

[0306] Furthermore, if (optionally) the impact lever 96 moves quickly enough, the deflection of the electrode 45 is also large enough that it can strike the cage 48, thus also resulting in a further tapping on the cage 48.

[0307] The Fig. 19aFigure 1 shows a three-dimensional sectional view of the filter unit 4 of the biomass heating plant 1 from the rear in a third cleaning stage. Fig. 19b shows a flat sectional view of the filter unit 4 of the biomass heating system 1 from the rear in the third cleaning state.

[0308] In the third cleaning stage, the striking arm jerks abruptly or with high acceleration from its position. Figures 18a and b back, and strikes the filter tip 454 and optionally the spring element 453 with the flat side of the conical base of the stop head 97. The result of this striking is in the Figures 20a and 20b The image shows a snapshot shortly after impact in the third cleaning state.

[0309] The Fig. 20a Figure 1 shows a three-dimensional sectional view of the filter unit 4 of the biomass heating plant 1 from the rear in a fourth cleaning stage. Fig. 20bshows a flat sectional view of the filter unit 4 of the biomass heating system 1 from the rear in the fourth cleaning state.

[0310] As a result of the impact of the stop head 97 on the filter tip 454 and optionally on the spring element 453, the electrode 45 oscillates in a second direction (see double arrow FE5), which differs from the first direction, and (optionally) strikes the cage 48, thus producing a further cleaning effect. This impact exerts a force in the second direction, which is clearly different from the first. Depending on the shape of the cone of the stop head 97, the (horizontally viewed) angle between the first and second directions is greater than 45 degrees, preferably greater than 60 degrees.

[0311] Thus, the tapping in the third / fourth cleaning state has a preferred direction regarding the tapping, which differs from the preferred direction in the second cleaning state.

[0312] In other words, the present implementation of the tapping mechanism causes the electrode to be tapped from two different directions with two cleaning impulses, which takes into account the special shape of the electrode 45 and cleans it effectively.

[0313] The spring element 453 also protects the electrode 45 from the impact of the stop lever 96, in order to protect the electrode 45 and especially the insulator 46 from damage (e.g. deformation, breakage).

[0314] Furthermore, the insulator-side suspension 452 can be configured such that it promptly returns the electrode 45 to its rest position (along the LAE axis) after the second impact. This prevents prolonged and undesirable swinging of the electrode 45.

[0315] Furthermore, cage 48 moves back to its starting position.

[0316] Optionally, the second impact can be made with a force with which the electrode 45 strikes the cage 48 with its tip 454, thereby advantageously producing a second cleaning impulse on the cage 48 and a third cleaning impulse on the electrode 45 (each in a further direction).

[0317] In other words, cleaning in filter 4 can be done with the following steps: The striking lever 96 is swung from its rest position into a striking position; thereby contacting the stop head 97 of the striking lever 96 with at least a part of the electrode 45, preferably contacting the tip 454, and deflecting the electrode in a first direction FE3, thus producing a first cleaning pulse. The stop head 97 of the striking lever 96 is then moved such that at least a part of the electrode 45, preferably the tip 454, is struck, and the electrode 45 is deflected in a second direction FE5, which is different from the first direction FE3, thus producing a second cleaning pulse. Optionally, the deflection of the electrode 45 in the second direction FE5 occurs such that the electrode 45 strikes the cage 48, thus producing a third cleaning pulse on the cage 48 and the electrode 45.

[0318] The procedure or process of Figures 16a to 20bThis process can be repeated several times (iteratively) until the cleaning is sufficient.

[0319] The Figures 21a to 21d Figures 1 and 2 show different views of the stop lever 96 with its conical striking head 97, in order to illustrate the special design of the striking head in the context of the explanations of the Figures 16a to 20b to clarify. (Other embodiments)

[0320] Features of the different embodiments and aspects can be combined arbitrarily, as long as this is evident to a person skilled in the art as feasible.

[0321] In this case, the electrode 45 is suspended from above in a way that allows it to oscillate. However, this is not a requirement. For example, the electrode 45 can also be mounted in such a way that it is suspended from below, and the tip of the electrode swings back and forth at the top. Likewise, the electrode 45 can be suspended horizontally or at an angle instead of vertically.

[0322] Furthermore, the suspension element 452 and the spring element 453 can be omitted and are not strictly necessary for the operation of the filter unit 4. Likewise, the filter tip 454 can be omitted.

[0323] The recirculation device 5 is described here with primary and secondary recirculation. However, in its basic configuration, the recirculation device 5 can also have only primary recirculation and no secondary recirculation. In this basic configuration, the components required for secondary recirculation can be completely omitted.

[0324] An air volume sensor, a vacuum sensor, a temperature sensor, an exhaust gas sensor and / or a lambda sensor can be provided at the inlet of the flue gas recirculation device 5.

[0325] The term "tubular" refers not only to round cross-sections or shapes of the tube, but also, for example, to angular (e.g., four-, six- or eight-sided) cross-sections or shapes of the tube.

[0326] Furthermore, instead of just three rotary screen elements 252, 253, and 254, two, four, or more rotary screen elements can also be provided. For example, five rotary screen elements could be arranged with the same symmetry and functionality as the three rotary screen elements presented. In addition, the rotary screen elements can also have different shapes or designs relative to each other. More rotary screen elements have the advantage of increasing the crushing function.

[0327] Regarding the specified dimensions, it should be noted that other dimensions or combinations of dimensions may be provided.

[0328] Other fuels besides wood chips or pellets, such as elephant grass, can also be used as fuel for the biomass heating system.

[0329] The biomass heating system disclosed herein can also be fired exclusively with one type of fuel, for example only with pellets.

[0330] The combustion chamber bricks 29 can also be provided without the recirculation nozzles 291. This can apply in particular in cases where no secondary recirculation is provided.

[0331] The rotational flow or vortex flow in the combustion chamber 24 can be designed to be clockwise or counterclockwise.

[0332] The combustion chamber ceiling 204 can also be designed to be inclined in sections, for example in a stepped shape.

[0333] Secondary (re)circulation can also be supplied only with secondary air or fresh air, and therefore does not recirculate the flue gas, but merely supplies fresh air.

[0334] The secondary air nozzles 291 are not limited to purely cylindrical bores in the combustion chamber bricks 291. These can also be designed as frustoconical or waisted openings.

[0335] The dimensions and sizes given are for illustrative purposes only and may be modified.

[0336] The terms "top" and "bottom" refer only by way of example to the illustrated embodiment with a filter 4 in a vertical orientation. These terms can be understood, for example, as "right" and "left" for a filter 4 in a horizontal orientation. Likewise, the filter can also be arranged obliquely or at an angle to the horizontal plane, which is also covered by the present disclosure.

[0337] A sawtooth-shaped electrode generally has points or tapered extensions.

[0338] The nominal heat output of 100 kW for the biomass heating system 1 of boiler 11 is given here only as an example. Boiler 11 can alternatively be designed for other nominal outputs, e.g. 50 kW, 70 kW or 250 kW.

[0339] Temperature and flow velocity data should be understood within the scope of the usual measurement errors when recording these physical parameters. (Reference symbol list)

[0340] 1 Biomass heating system 11 Boiler 12 Boiler base 13 Boiler housing 14 Water circulation device 15 Blower 16 Exterior casing 100 Control unit / Client 111 Exhaust gas temperature sensor 112 Lambda probe 113 Underpressure sensor or differential pressure sensor 114 Return temperature sensor or heating water temperature sensor 115 Boiler temperature sensor 116 Fuel bed height sensor 117 Combustion chamber temperature sensor 101 Machine learning unit 102 User interface 103 AI 190 Server 198 Connection 199 Network connection 2 Combustion device 21 First maintenance opening for the combustion device 22 Rotating mechanism bracket 23 Rotating mechanism 24 Combustion chamber 25 Rotating grate 26 Primary combustion zone of the combustion chamber 27 Secondary combustion zone or radiation section of the combustion chamber 28 Fuel bed 29 Combustion chamber bricks A1 First horizontal section line A2 First vertical section line 201 Ignition device 202 Combustion chamber slope 203 Combustion chamber nozzle 204 Combustion chamber ceiling 211 Insulation material, e.g., vermiculite 231 Drive or motor(s) of the rotating mechanism 251 Base plate of the rotating grate 252 First rotating grate element 253 Second rotating grate element 254 Third rotating grate element 255 Transition element 256 Openings 257 Grate lips 258 Combustion area 260 Bearing surfaces of the combustion chamber bricks 261 Groove 262 Projection 263 Ring 264 Support bricks 265 Incline of the support bricks 291 Secondary air or recirculation nozzles 3 Heat exchanger 31 Maintenance opening for heat exchanger 32 Boiler tubes 33 Boiler tube inlet 34 Reversing chamber inlet 35 Reversing chamber 36 Spring turbulator 37 Belt or spiral turbulator 38 Heat exchange medium 331 Insulation at boiler tube inlet 4 Filter assembly 41 Exhaust gas outlet 42 Electrode supply line 421 Connection 43 Electrode holder / cover 431 Mounting plate 44 Filter inlet 45 Electrode 45a, 45b, 45c, 45d, 45e Electrode parts 451 Filter insert 452 (Insulator-side) suspension element 453 Spring element 454 Filter tip 455 Proximal connecting bolt 456 Distal connecting bolt 457 Electrode teeth 458 Slot 46 Electrode insulation / Insulator 46a Main body of the insulator 46b (Internal) volume of the electrostatic filter device 461 Ribs 461a Supplementary rib 462 Recesses 463 Flank 464 Foot 465 Intermediate cone parts 4651 Cone shell surface 4652 End edge of the intermediate cone part 466 Intermediate cylinder parts 4661 Cylinder shell surface 467 End rib 468 Transition element 469 Passage 47 Filter outlet 48 Cage / counter electrode 49 Flue gas condenser 411 Flue gas inlet to the flue gas condenser 412 Flue gas outlet from the flue gas condenser 481 Cage bracket 491 First fluid connection 491 Second fluid connection 493 Heat exchanger tube 4931 Tube retaining element 4932 Tube sheet element 4933 Loops / Reversal points 4934 First gaps between the heat exchanger tubes 4935 Second gaps between the heat exchanger tubes and the outer wall of the flue gas condenser 4936 Passages 495 Head element 4951 Head element flow guide 496 Condensate outlet 4961 Condensate collection funnel 497 Flange 498 Side surface with maintenance opening 499 Mounting device for the flue gas condenser 5 Recirculation device 50 Ring channel around combustion chamber bricks 52 Air valve 52s Slide valve 53 Recirculation inlet 54 Primary mixing channel 55 Secondary mixing channel 55a Secondary temperature control channel 56 Primary recirculation channel 57 Secondary recirculation channel 58 Primary air channel 59 Secondary air channel 5a Primary mixing unit 5b Secondary mixing unit 521 Valve actuator 522 Valve actuating shafts 523 Valve vane 524 Valve housing 525 Valve pre-chamber 526 Valve through-hole 527 Valve body 528 Valve surface 531 Recirculation inlet channel 532 Recirculation inlet channel divider 541 Primary passage 542 Primary mixing chamber 543 Primary mixing chamber outlet 544 Primary recirculation valve inlet 545 Primary air valve inlet 546 Primary mixing chamber housing 551 Secondary passage 552 Secondary mixing chamber 553 Secondary mixing chamber outlet 554 Secondary reciprocating valve inlet 555 Secondary air valve inlet 556 Secondary mixing chamber housing 581 Primary air inlet 582 Primary air sensor 591 Secondary air inlet 592 Secondary air sensor 6 Fuel supply 61 Rotary valve 62 Fuel supply shaft 63 Transmission mechanism 64 Fuel supply channel 65 Fuel supply opening 66 Drive motor 67 Fuel auger 7 Ash removal 71 Ash discharge screw 711 Screw shaft 712 Centering disc 713 Heat exchanger section 714 Burner section 72 Ash removal motor with mechanism 73 Transition screw 731 Right subsection - screw rising to the left 732 Left subsection - screw rising to the right 74 Ash container 75 Transition screw housing 751 Opening of the transition screw housing 752 Limit plate 753 Main body section of the housing 754 Fastening and separating element 755 Funnel element 81 Bearing axes 82 Pivot axis of the fuel level flap 83 Fuel level flap 831 Main surface 832 Center axis 833 Surface parallel 834 Openings 84 Bearing notch 85 Sensor flange 86 Firebed height measuring mechanism 9 Cleaning device 91 Cleaning drive 92 Cleaning shafts 93 Shaft support 94 Extension 95 Turbulator supports 951 Swivel bearing mount 952 Extensions 953 Passages 954 Recesses 955 Swivel bearing linkage 96 Two-armed impact lever 97 Stop head E Fuel insertion direction S* Flow arrows IMI Insulator center axis 46 TI1 Insulator recess depth 462 TI2 Effective insulator thickness Vf filter voltage, If filter current, Wf filter power, Sf filter status, Wk boiler power, Vfmin minimum voltage of the filter, Vfmax maximum voltage of the filter, EL electrode length

Claims

1. A biomass heating system (1) for burning fuel in the form of pellets and / or wood chips, comprising: a boiler (11) having a housing; a combustion device (2) having a combustion chamber (24); a heat exchanger (3) disposed downstream of the combustion chamber (24) and in fluid communication with the combustion chamber (24); an electrostatic filter device (4) for filtering a flue gas produced in the combustion device (2), wherein the filter device (4) is arranged downstream of the heat exchanger (3) and is fluidically connected to the heat exchanger (3); a control device (100) for controlling the electrostatic filter device (4); wherein the electrostatic filter device (4) comprises: a tubular internal volume (46b) in which the flue gas flows; a first rod-shaped electrode (45) formed as a discharge electrode (45); and a second tubular electrode (48) formed as a counter electrode (48); and an insulator (46) for supporting the sputter electrode (45); and a filter inlet (44) through which the flue gas can enter the filter device (4); and a filter outlet (47) through which the flue gas can exit the filter device (4); wherein: the insulator (46) is a rod-shaped ceramic or porcelain insulator (46); and the insulator (46) has ribs (461), wherein recesses (462) are provided between the ribs (461) of the insulator (46), characterized in that the recesses are provided for providing a plurality of desired burn-off points for conductive deposition on the surface of the insulator (46), wherein the desired burn-off points are configured in such a way that a burn-off can take place at these points by applying high voltage to the insulator (46).

2. The biomass heating system (1) as set forth in claim 1, wherein: the discharge electrode (45) has a cross profile or a star profile.

3. The biomass heating system (1) according to claim 1 or 2, wherein the discharge electrode (45) is swingably suspended from the insulator (46) and has a vertical longitudinal axis (LAe) IN the rest position, wherein the biomass heating system (1) is set up in such a way that the spray electrode (45) is deflected for cleaning in such a way that it oscillates in at least two directions.

4. The biomass heating system (1) according to any one of the preceding claims, wherein the discharge electrode (45) is provided from at least two interconnected, elongated and plate-shaped electrode parts, wherein at least one of the electrode parts (45a, 45b, 45c, 45d, 45e) has sawtooth-shaped projections (457).

5. The biomass heating system (1) as set forth in claim 1, wherein, a recess (462), an intermediate cone part (4651) with an end edge (4652) facing the recess (462) and an intermediate cylinder part (466) are provided between the ribs (461) of the insulator (46).

6. The biomass heating system (1) according to any one of the preceding claims, wherein a main body (46a) of the insulator (46) is disposed offset from an opening of the filter outlet (47) in a longitudinal direction of the tubular filter device (4); and wherein the insulator (46) is arranged at an end of the filter device (4), which is opposite to the end at which the filter inlet (44) is provided.

7. The biomass heating system (1) according to any one of the preceding claims, wherein the biomass heating system (1) is set up in such a way that the average flow velocity in the filter device (4) in full-load operation of the biomass heating system (1) is in a range of 0.5 to 3 m / s, preferably in a range of 1 to 2 m / s.

8. The biomass heating system (1) according to any one of the preceding claims, wherein the biomass heating system (1) is set up in such a way that the temperature of the flue gas in the filter inlet (44) during full-load operation of the biomass heating system (1) is less than 220°C, preferably less than 200°C.

9. The biomass heating system (1) according to any one of the preceding claims, wherein the combustion device (2), the heat exchanger (3) and the electrostatic filter device (4) are arranged together in the boiler (11), and in the heat exchanger (3), turbulators (36, 37) are arranged as flow brakes in such a way that the entry speed of the flue gas into the filter device (4), which is arranged downstream from the turbulators (36, 37) in terms of flow, is at most 2 m / s during full-load operation of the boiler (11).

10. The biomass heating system (1) according to any one of the preceding claims, further comprising: a cleaning device (9) having a cleaning drive (91) for actuating a percussion lever (96), wherein the percussion lever (96) has a conical percussion head (97).

11. The biomass heating system (1) according to any one of the preceding claims, wherein at least one main body (46a) of the insulator (46) are arranged in an end-side dead volume (S8) of the inner volume (46b) of the filter device (4).

12. The biomass heating system (1) according to any one of the preceding claims, wherein the filter outlet (47) of the filter (4) is arranged such that it is provided at a longitudinal position of the filter (4) that is, preferably completely, different from a longitudinal position of a main body (46a) of the insulator (46).

13. The biomass heating system (1) according to any one of the preceding claims, wherein the control device (100) is configured such that: in the operating state of a burning out of the boiler (11), which follows a state of a regular combustion operation of the boiler (11), and after termination of a fuel supply to the combustion device (2), a filter voltage (Vf) is successively increased so that conductive deposits on the surface of the insulator (46) are burned off by means of a glow discharge.

Images