Apparatus and method for reducing particulate matter emissions, and fire space

Abstract

The present invention relates to a device (10) for reducing particulate matter emissions from flue gas (S) in a batch-fueled fire space (12) equipped with a firebox (14). The device (10) is installed in a firebox (14) located within the flame (18) region or directly adjacent to the flame (18) and comprises an electrode (16) that generates an electric field (E), an insulator (24) that covers a part of the electrode (16), a power supply (22) that supplies voltage to the electrode, a transformer (30) that converts the voltage level of the electricity supplied by the power supply (22) to a voltage level of 1 to 100 kV, preferably 10 to 30 kV, and a collector (25) that can be installed within the flame (18) region or in a firebox (14) directly adjacent to the flame (18) to collect charged particles (15). The apparatus (10) is configured to charge particles (15) through an insulator (24) to allow a leakage current of 0.001 mA to 5.0 mA, preferably 0.1 mA to 5.0 mA, and optimally 2.0 mA to 3.0 mA. The insulator (24) and the collector (25) act as collection surfaces for the charged particles (15), and the particles (15) are oxidized on the collection surfaces under the influence of temperature. The present invention also relates to firespace and methods.

Description

Technical Field

[0001] The present invention relates to an apparatus for reducing particulate emissions from flue gas in a fire space equipped with a firebox. The apparatus of the present invention forms an electric field (or electric field; the same applies hereinafter) provided within the region of the flame or directly adjacent to the flame within the firebox, and an electrode that moves the particles charged by the flame by this electric field, an insulator that covers the portion of the electrode exposed to the flue gas to prevent the electrode from getting dirty, a ground plane, a collector for collecting charged particles, and is connected to the electrode and has a power supply that generates a voltage of 1 to 100 kV, preferably 10 to 30 kV, and generates an electric field between the electrode and the ground plane.

[0002] The present invention also relates to a fire space and a method for reducing particulate gas from flue gas in the fire space.

Background Art

[0003] Particulate emissions from residential combustion in residential areas degrade air quality and have an adverse impact on both health and the environment. Carbon soot emissions generated from incomplete combustion absorb solar radiation and worsen global warming by changing the reflectivity of ice. Therefore, the EU monitors emissions from residential combustion, and new technologies for reducing emissions generated from residential combustion are needed.

[0004] Conventionally, it is known to use electrostatic filters to reduce particulate emissions from flue gas, but these filters are suitable for larger-scale combustion plants and are costly to implement in a fire space used for residential combustion.

[0005] A previously known publication, German Patent Application Publication No. 102012023453A1, discloses a method of reducing particles in flue gas by using electrodes in a firebox to generate an electric field in the flame region and collecting particles on the electrode surface. The operation of this device is based on the fact that particles generated in the combustion process become charged by electrons and ions generated in the combustion process, i.e., particles are naturally charged by the flame. Due to the charging, particles move toward or away from the electrodes. However, a problem with this type of device is that, as a result of combustion, plasma is formed in the flame region, causing a short circuit at the electrodes and malfunctioning the device. On the other hand, if the electrodes are placed further away from the flame, the duration of ions is shortened, and the charges move within the electric field and neutralize before reaching the electrodes. This device has the problem of the electrodes becoming fouled and the device becoming inoperable. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102012023453A1 [Overview of the Initiative]

[0007] An object of the present invention is to provide a device for reducing particulate emissions that is more efficient and reliable than conventional devices. The features of the device according to the present invention are as described in claim 1. Another feature of the present invention is to provide a fire space that is more environmentally friendly and produces less particulate emissions than conventional fire spaces. The features of the fire space according to the present invention are as described in claim 12. Yet another object of the present invention is to provide a method for reducing particulate emissions from flue gas in a combustion area. The features of the method according to the present invention are as described in claim 14.

[0008] The objective of the apparatus according to the present invention is achieved by an apparatus for reducing particulate matter emissions from flue gas in a combustion space having a firebox. In this apparatus, there is an electrode placed in the firebox within or near the flame, which generates an electric field and moves particles charged by the flame through this electric field. This electrode has an insulator that covers a portion of the electrode to prevent it from being exposed to flue gas and becoming contaminated. Furthermore, the apparatus has a power supply that supplies voltage to the electrode and generates an electric field, a transformer that transforms the voltage level of the electricity supplied by this power supply to a voltage level of 1 to 100 kV, preferably 10 to 30 kV, and a recoverer that can be placed in the firebox within or near the flame and recovers charged particles. The apparatus is configured to allow a leakage current of 0.001 mA to 5.0 mA, preferably 0.1 to 5.0 mA, more preferably 2.0 to 3.0 mA, through the insulator, so that the particles become charged. These insulators and aggregates act as collection surfaces for charged particles, where the particles oxidize under the influence of temperature.

[0009] In the apparatus according to the present invention, particles collected on the electrode insulator, or more preferably mainly on the collecting body, burn when the electrode and collecting body are placed within or near the flame region, thus eliminating the need for a separate particle collection process. This is because the collected particles oxidize on the collection surface under the influence of temperature. The insulator protects the electrode from contamination and prevents a complete short circuit between the electrode and the firebox, thus preventing failure. Since leakage current compensates for the charging of particles already generated by the flame, more particles can be collected on the collection surface.

[0010] In this specification, unless otherwise specified, the voltage unit V refers to AC voltage.

[0011] For cleaning, it has been found to be particularly effective when the leakage current is 2.0-3.0 mA at voltages of 10-30 kV. The upper limit of the voltage level is determined by economic constraints, as the wattage of the device increases considerably as the voltage increases. On the other hand, the lower limit is determined by the filter efficiency.

[0012] This device is preferably used in conjunction with a so-called radiant combustion space. In other words, this device should not be used in boiler structures intended to heat liquids.

[0013] The apparatus according to the present invention is simple and has relatively few components that are prone to malfunction. Therefore, this apparatus is an economical investment for residential fire spaces and is easy to operate. This apparatus can be used in conjunction with new fire spaces or is suitable for retrofitting to existing fire spaces. The cleaning efficiency that can be achieved with this apparatus is 50-90% of the total mass of particulate matter.

[0014] As used herein, the term “particles” primarily refers to carbon soot, which may be mixed with other minute concentrations of particles.

[0015] The fire space in question is a so-called batch-fueled fire space, not, for example, a continuously operating industrial boiler. In this specification, "batch-fueled" refers to a fire space that supplies fuel in batches, rather than, for example, automatic continuous combustion. Specifically, this batch-fueled fire space is a residential fire space with a wattage of less than 50 kW. The advantages of the apparatus according to the present invention are particularly evident in batch-fueled fire spaces, where incomplete combustion conditions occur at a quantitatively much higher rate than in continuous-fueled fire spaces.

[0016] Instead of batch-type fuel firespaces, the present invention is also applicable to continuous-fuel household pellet stoves with a wattage of less than 50kW that automatically supply fuel using a small hopper.

[0017] The power supply and insulator are both configured to allow leakage current, which preferably generates corona discharge through the electrode insulator, causing the particles to become charged. The magnitude of the leakage current that can be generated is influenced by two factors: the power supply and the properties of the insulator. Corona discharge effectively charges the particles located in that region, but it does not cause a complete short circuit in the device.

[0018] The voltage required for effective filtering, and the resulting leakage current, are significantly influenced by the electrode configuration, shape, and number. A general rule of thumb for design is that lower voltages require a higher leakage current to generate corona discharge, while higher voltages require a lower leakage current.

[0019] The electrode insulator covers the electrode to prevent a complete short circuit caused by the flame plasma. In other words, leakage current preferably guides charged particles to the collector, while the charging of particles caused by corona discharge at a further distance from the electrode causes the particles to gather closer to the electrode, and the flame naturally charges the particles that gather on the surface of the electrode's insulator.

[0020] The device preferably has an auxiliary insulator that covers a portion of the electrodes passing through the duct that constitutes the fire space, which introduces the electrodes into the firebox. This auxiliary insulator is intended to prevent current leakage by being close to the surface of the fire space. This improves cleaning efficiency, as leakage occurs only within the flame region where it is expected to occur.

[0021] It is preferable that this device has a grounding mechanism. This ensures the safe operation of the device.

[0022] This device also preferably has a grounding surface formed inside the firebox to strengthen the electric field. This grounding surface makes it possible to secure some of the particles with the same charge as the electrodes, which helps to strengthen the electric field. In other words, the grounding surface is preferable because it acts as a particle collector.

[0023] Generally, the "collection surface" refers to, for example, the surface of the grounding plane acting as a collector or the outer surface of an insulator.

[0024] The grounding plane can be provided on the wall of the firebox within the region of the electric field and strengthens the electric field. Therefore, a part of the particles gathers on the side of the firebox.

[0025] Preferably, the grounding plane is provided within the region of the flame or in a region close to a flame having a temperature exceeding 500 °C. Thereby, the particles are also combusted and removed from the grounding plane.

[0026] The electrode is preferably a rod-shaped electrode. The rod-shaped electrode is simple to manufacture and insulate. Further, the rod-shaped electrode is easier to install compared with a flat electrode and is also easy to introduce into the firebox.

[0027] In a preferred embodiment where the electrode is rod-shaped, the insulator has an outer casing configured to partially surround the rod-shaped electrode and a plug provided on the outer casing to cover the end of the electrode. In such a design of the insulator, the leakage current automatically flows outward along the seam between the outer casing and the plug from the electrode, sets the corona discharge in a preferable control state, and charges the particles.

[0028] The electrode can be formed in a flat shape. The electrode having a flat shape homogenizes the electric field extremely, so that the collection of particles on the insulator surface of the electrode and the corresponding grounding plane becomes more efficient.

[0029] The plane of the flat-shaped electrode can be set in the moving direction of the flue gas. Therefore, the generated electric field becomes as wide as possible in the moving direction of the particles moving the flue gas, and there is sufficient time for as many particles as possible to move within the electric field and reach the insulator surface of the electrode or the grounding plane acting as a collection surface, and then flow toward the flue duct along with the flow of the flue gas in the fire space and exit from the region under the influence of the electric field.

[0030] Regarding the power supply, it is preferable that the electrodes generate negative polarity. Research has shown that using electrodes with negative polarity improves cleaning efficiency because combustion generates more strongly negatively charged particles. In this case, negative charge is generated in the particles by leakage current generated through the electrodes, preferably via corona discharge. The charged particles therefore have the same polarity and do not neutralize each other.

[0031] For the insulator, it is preferable to configure it according to one or more of the following characteristics for the selected leakage current: namely, the thickness of the insulator, the material of the insulator, the length of the air gap between the insulator and the electrode, the discontinuity of the insulator, and the shape of the insulator. By changing one or more of these characteristics, it is possible to affect the insulating ability of the insulator, and thereby affect the magnitude of the leakage current. The insulator may have small discontinuities resulting from potential corona discharge. These discontinuities may also be areas where the thickness of the insulator is thinner than any part around the electrode.

[0032] For the electrode insulator, it is preferable to use a material with a crystalline structure that recovers after corona discharge. Such materials are particularly suitable for applications where corona discharge occurs regularly, but the insulator is also necessary to provide continuous insulating capability.

[0033] Regarding the electrode insulator, mica insulators are preferred. The electrode position conditions within the flame region, or the conditions adjacent to this position, are very demanding on the material due to the high temperature. Mica insulators have been shown to exhibit high resistance to high temperatures and to exhibit high resistance to conditions that allow for sufficient leakage current to appear in the flame region even after prolonged use, while simultaneously enabling the implementation of the present invention. A key property of mica insulators is the recovery crystal structure that recovers after corona discharge.

[0034] Alternatively, HBN (hexagonal boron nitride) can also be used as an insulating material. HBN is a highly versatile material, and its heat transfer properties can be adjusted by its crystal structure. HBN is a durable and self-healing material; for example, it can repair cracks if they exist. Although HBN is currently an expensive material, it has the potential to become more economical in the future.

[0035] For the accompanying insulator, aluminum oxide (alumina) is preferred. Aluminum oxide has better heat resistance than mica, which is a suitable material for use as an insulator, and does not generate leakage current.

[0036] The apparatus according to one embodiment also has a second electrode, and the polarity of the first and second electrodes is the same to optimize the charging of particles. By using two electrodes, particles can be reliably charged over a wider area within the firebox, reducing the influence of the spontaneous charging phenomenon of particles due to the flame during particle collection.

[0037] Regarding the power supply, it is preferable to have a transformer that raises the voltage supplied to the electrodes by the power supply to the desired current level. The transformer includes a microprocessor, a control / drive circuit, a protection circuit, and a high-voltage converter.

[0038] By using such a transformer, for example, energy from a normal grid or DC power supply can be easily and inexpensively converted into the operating voltage required for electrode operation, which is relatively high compared to the input voltage. By using a high operating voltage and a relatively high frequency (around kHz or MHz), and depending on the waveform, the power consumption of the device can be significantly reduced to a level of 1 to 50 W, preferably 1 to 20 W.

[0039] Instead of alternating current, the power supplied by the power source can preferably be used as direct current in the range of 12 to 40 VDC. This simplifies the operation of the device because a grid voltage transformer is not required, and the device can be connected to an existing DC power source. As the power source, the power supply already used to power other electronic devices in the firespace can be used, or, for example, the power supply TEC means described below can be used. On the other hand, with this alternative method, proper grounding of the device at installation becomes more important because grounding is provided by an independent protective earthing conductor rather than the grid power cable. In general, residential buildings do not have existing grounding points in each room of an industrial plant, so the installation and wiring of an additional protective conductor must be considered on a case-by-case basis.

[0040] Since the power supplied by the power source can also be obtained from grid power, the device is otherwise the same as the aforementioned device, but the device is equipped with either an external grid power conversion circuit or an internal grid power conversion circuit (AC / DC transformer). An externally mounted so-called household transformer (standard transformer) or other means is used in a modified usage configuration using grid power. This is necessary when DC is not available in the fire space area, or when DC is not available, for example, at various demonstrations and presentations.

[0041] In one embodiment, the power source is an independent thermoelectric generator. In the case of a thermoelectric generator, the temperature difference between the external area of ​​the fire space or the outer surface of the firebox and the conditions inside the firebox can be used to generate a current that can be used for relatively low-power operation of the device, based on the Seebeck effect. This allows the device to be realized and implemented without an on-site grid socket or conductor to the grid supply, or to be used in locations where electricity is unavailable, such as traditional cottage saunas. In this variant, the device must be reliably grounded by a protective earthing conductor extending, for example, to a known grounding structure near the facility or to an existing grounding point.

[0042] In one embodiment, the power source consists of a physically small battery or rechargeable battery. These allow for balancing electricity consumption when the device is partially or fully powered by the thermoelectric generator or other “off-grid” systems, such as an external solar panel system that does not constitute part of the device. However, it should be noted that modern residential solar panel systems already include DC / AC inverters as standard components, so the system can supply AC power, not just DC power, similar to older small “summer cottage” systems. Modern photovoltaic systems also generally include rechargeable batteries at the consumer's request. In yet another variation, if it is deemed necessary and beneficial for the consumer to make the device rechargeable, for example, the device can conserve electrical energy used when electricity prices are low and consume electrical energy from the battery / rechargeable battery when energy prices are high. Alternatively, different portable means could be used.

[0043] The electrodes can be formed as part of the firespace structure. This ensures that the electrodes do not affect the flue gas flow within the firespace. Such a structure is easily implemented in a new firespace but more difficult to implement in an existing one. In some models, the electrodes can serve as a substitute for existing removable baffles that affect the firespace flow.

[0044] Alternatively, the electrodes are components separate from the fire space structure located within the firebox. Such components are very easy to add later.

[0045] In one embodiment, the transformer is configured to supply pulsed or mixed current to the electrodes. The pulsed power supply can particularly suppress the energy consumption of the device in a relatively high kHz range compared to, for example, the 50 / 60 Hz frequency of household grid power.

[0046] This device may be equipped with a control means that has a controller that controls the leakage current according to the state of the flame. The state inside the firebox changes as the flame progresses, and this change affects the insulating capacity of the insulator not only by temperature but also by the magnitude of the leakage current. By providing a control means, it becomes possible to attempt to standardize the magnitude of the leakage current. In fact, the controller can be implemented in a microprocessor, and in addition, another “controller” component can be implemented in case the microprocessor used is not fast enough to respond to the state of the flame, for example, and the control cycle is not appropriate.

[0047] In one embodiment, the control means includes an actuator that moves an electrode inside an insulator to adjust the air gap between the electrode and the plug based on the control of the controller. In this case, the controller controls the actuator to perform the electrode movement. The length of the air gap affects the magnitude of the leakage current and, therefore, the cleaning efficiency of the device.

[0048] Alternatively, or in addition to the above embodiments, the controller is configured to set the voltage generated from the power supply according to a calibration curve. A predetermined curve of the controller or control unit can be programmed, and this predetermined curve optimizes the output voltage level according to, for example, the measured current or the measured temperature, in addition to the control performed by the actual controller based on the control curve and the controller's setting parameters. The control curve can be generated experimentally to find the optimal setting range and limits, or it can be generated based on theoretical calculations to predict the optimal limits. Furthermore, the calibration curve can include different calculation correction coefficients, which, in addition to the basic calculations, enable different optimization methods depending on, for example, the type of fireplace. This control method is more multidimensional than a control curve based purely on measurement.

[0049] Suitable controllers include P, I, PI, or PID controllers.

[0050] The objective of the fire space according to the present invention is achieved by a firebox for burning fuel, preferably wood, and a device for reducing particles from flue gas according to any of the embodiments described herein. According to the present invention, particulate emissions from a fire space are significantly less than those from conventional fire spaces. In combustion phenomena within a fire space, complete combustion is rarely reached, and combustion is generally incomplete, resulting in the generation of particulate emissions. Since it is difficult to prevent incomplete combustion, the device according to the present invention is used to prevent particles from escaping into the environment by oxidizing the particles before they are discharged from the fire space.

[0051] The fire space according to the present invention can be, for example, a hearth, a hearth insert, a sauna stove, or a stove, but a pellet stove can also be used.

[0052] The electrodes are placed within the flame region or in the firebox near the flame where the temperature exceeds 500°C, to oxidize particles on the electrode's insulating surface. This region can be located behind the baffle plate in the fire space or in another sufficiently hot part of the flue system. The electrode's position is crucial for the temperature to be high enough for particles accumulating on the electrode's insulator or contact surface to undergo oxidation.

[0053] Alternatively, the catalytic structure can be used as a particle collection surface. The collected particles are then oxidized at temperatures below 150°C.

[0054] In one embodiment, the apparatus according to the present invention removes particles from flue gas. This apparatus allows for the use of another catalyst downstream in the flue, thus enabling the removal of gaseous contaminants. The use of catalytic converters was previously impossible because the large number of particles in the flue gas would interfere with the operation of the catalytic converter.

[0055] Regarding the electrodes, it is preferable that they be in at least partial contact with the flame. This will optimize the generation of corona discharge.

[0056] The electrodes are preferably placed in the center of the firebox, in an area a certain distance from the walls of the firebox, and this distance is 10-25% of the width of the firebox where the electrodes are located. In other words, the electrodes are placed in an area within the center of the firebox that covers 50-80% of the total width of the firebox. With such an electrode configuration, the distance that particles travel from the flue gas flow to the insulating surface of the electrodes, or preferably to the collector, is sufficiently short, and the particles are reliably moved through the electric field in the flue gas and can reach the insulating surface of the electrodes before the particles are carried out of the area affected by the electric field by the flue gas.

[0057] The objective of the method according to the present invention is a method for reducing particulate matter emissions from flue gas in a fire space equipped with a firebox, which is achieved by supplying voltage to electrodes by a power source, converting the voltage level of the electricity supplied by the power source to a voltage level of 1 to 100 kV, preferably 10 to 30 kV, by a transformer, protecting at least a portion of the electrodes exposed to the flue gas with an insulator, and preventing the electrodes from becoming contaminated. Furthermore, in this method, an electric field is generated in the firebox by electrodes placed in the flame region, or electrodes directly or immediately adjacent to the flame, causing particles charged by the flame to move toward the electrodes by the electric field, and a leakage current of 0.001 mA to 5 mA, preferably 2.0 to 3.0 mA, from the electrodes to flow through the insulator, thereby charging the particles. Furthermore, in this method, the charged particles are collected by a collector and electrodes provided in the flame region, or in the firebox directly or immediately adjacent to the flame, and the collected particles are oxidized under the effect of temperature.

[0058] In the method according to the present invention, particle collection is based on two parallel phenomena: spontaneous charging of particles caused by a flame and charging of particles caused by leakage current. The combined effect of these phenomena allows charged particles to be collected on a collection surface within an electric field. Since the particles on this collection surface are oxidized, i.e., burned, there is no need to collect them separately.

[0059] Leakage currents preferably generate corona discharge. Corona discharge imparts a strong charge to particles, but does not cause equipment failure or a complete short circuit.

[0060] In this method, it is preferable to adjust the magnitude of the leakage current using a controller configured in the control means of the device according to the flame state. The performance of this device can be optimized under all flame conditions, and therefore emissions can be reduced. [Brief explanation of the drawing]

[0061] The present invention, which is not limited to the embodiments described below, will be described in detail below with reference to the accompanying drawings. [Figure 1a] Figure 1a is a side cross-sectional view showing a device according to the first embodiment used in a fireplace. [Figure 1b] Figure 1b is a front cross-sectional view showing a device according to the first embodiment used in a fireplace. [Figure 2] Figure 2 is a front cross-sectional view showing a device according to a second embodiment used in a fireplace. [Figure 3] Figure 3 is a side cross-sectional view showing a device according to a third embodiment used in a sauna stove. [Figure 4] Figure 4 is a side cross-sectional view showing a device according to a fourth embodiment used in a sauna stove. [Figure 5] Figure 5 is a front cross-sectional view showing a device according to a fifth embodiment used in a fireplace.

[0062] The apparatus according to the present invention can be used in combination with a fireplace, sauna stove, stove, or similar fire space. Incidentally, Figures 1a and 2 show the first and second embodiments according to the present invention, in which the apparatus 10 is connected to a batch fuel fireplace 40. On the other hand, Figures 3 and 4 show an embodiment in which the apparatus 10 is combined with a sauna stove 42.

[0063] Figure 1a shows a first embodiment of the apparatus 10 according to the present invention, installed in a firebox 14 of a fireplace 40 operating as a firespace 12. In all embodiments, the basic components of the apparatus 10 include at least one electrode 16 located within or near the flame 18, an insulator 24 surrounding the electrode 16 and protecting it from flue gas S, a collector 25 which is preferably a ground surface 20, a power supply 22, and a transformer 30. The operation of the apparatus 10 is based on the ability of current to leak from the electrode 16 through the insulator 24, which preferably takes the form of a corona discharge body, and charge the collected particles. The operation of the apparatus 10 also relies in part on the movement of particles 15 that are naturally charged by the flame in accordance with the potential of the electrode in an electric field E, either away from the electrode and toward or away from the electrode 16. The electric field E generated by the electrode 16 preferably moves negatively charged particles 15 toward the collector 25 which is also negatively charged and has moved away from the electrode 16. Ultimately, the particles 15 adhere to the surface of the collection body 25. If there are any positively charged particles, they also move towards the insulator 24 of the electrode 16.

[0064] The particles 15 that accumulate on both the surface 26 of the insulator 24 of the electrode 16 and the collector 25 are oxidized, i.e., burned, at each of these locations as a result of the heat being widely distributed, producing only carbon dioxide and pure ash. In the drawing, the wood burning in the fire space 12 is indicated by reference numeral 46, the grate through which primary air is supplied to the firebox 14 is indicated by reference numeral 48, and the door is indicated by reference numeral 52.

[0065] Figure 1b shows a preferred modification of the apparatus 10 using two rod-shaped electrodes 16 on either side of a fire space 12. As shown in Figure 1b, the electrodes 16 and the insulator 24 surrounding them extend through the wall structure of the fire space 12. In this embodiment, the insulator 24 has a sheath 27 surrounding the sides of the rod-shaped electrodes 16 and a plug 29 closing the sheath 27 at the ends 31 of the electrodes. Leakage current from the electrodes 16 through the insulator 24 occurs along the seam between the sheath 27 and the plug 29, causing a corona discharge separated from the electrodes 16. The corona discharge efficiently charges the particles to the potential of the electrodes 16, and it is preferable that they become negatively charged when the cathode 16 is used.

[0066] The first embodiment shown in Figures 1a and 1b differs from the second embodiment in Figure 2 in the number of electrodes. In the first embodiment in Figures 1a and 1b, the electrodes 16 used in the apparatus 10 are rod-shaped. In Figure 1b, it is preferable to use two rod-shaped electrodes 16, but it is also possible to use only one electrode 16, or three electrodes 16. When only one electrode is used, it is preferable that the polarity of that electrode is negative, because most particles that are naturally charged by a flame are also negatively charged. When two or three electrodes are used, it is also preferable that the polarities of the electrodes are the same, so as to prevent the generation of charged particles with different polarities that cancel each other out. The plane 32 of the electrode 16 is preferably set parallel to the flue gas flow S.

[0067] From the standpoint of device efficiency, electrodes 16 are placed in the firebox 14 within the region of the flame 18, where the temperature exceeds 500°C, or in a region adjacent to the flame 18, to oxidize the particles that accumulate on the surface 26 of the insulator 24 of the electrodes 16. This temperature is generally already reached by the first batch of wood, but it is a temperature that depends on the combustion device.

[0068] The strength of the electric field around the electrodes affects how efficiently the combustion device collects particles. As the electric field strength increases, particles collect over a larger area relative to the electrodes, and the amount of particles collected also increases over time. The electric field strength varies depending on the voltage level used. If the electric field is homogeneous, the equation E = V / d holds true, where E is the electric field strength, V is the voltage, and d is the distance. Furthermore, the shape of the generated electric field, and therefore the shape, number, and configuration of the electrodes used, have an effect. In practice, the design is limited by the structure and materials of the fire space. A further objective is to optimize the residence time of flue gas within the area affected by the electric field. Here, the shape and path of the flue gas in the fire space as it moves from the firebox to the chimney must be considered. Generally, flue gas moves within the firebox at a speed of 0.2 to 2 m / s. This speed must also be considered when designing the required electric field strength, along with the electrode position and the size of the firebox. Regarding the electrodes, it is preferable to position them such that the electric field spreads over a wide area in the direction of the flue gas flow. Assuming the flue gas flow is laminar, it is preferable that the electrodes be located in the center of the flue gas flow. For the electrodes, or at least one of the electrodes, it is preferable that they be located in the center of the flue gas flow where most of the particles are in motion. Therefore, at least one electrode is positioned at a distance from the wall of the firebox in the area spreading in the center of the flue gas flow. The distance d of the electrode 16 from the wall 38 of the firebox 14 can be set to 5 to 30%, preferably 10 to 25%, of the width of the firebox 14.

[0069] As shown in Figure 1a, the apparatus 10 according to the present invention has a collector 25, preferably a ground surface 20, formed inside a firebox 14 adjacent to the electrode 16. The ground surface 20 may be, for example, a metal plate 44 attached to the wall portion 38 of the firebox 14 as shown in Figure 1a, or a metal structure incorporated into the wall portion 38 of the firebox 14. The electric field E formed by the electrode 16 is directed toward the ground surface 20, and because the ground surface 20 is on the wall portion 38 of the firebox 14, the electric field E covers the entire width of the firebox, and particles 15 charged by the flame 18 are attracted toward the electrode 16, and particles of the opposite electrode (opposite sign and charge) are attracted toward the ground surface.

[0070] To supply voltage to the electrodes, a sealed duct can be constructed within the firespace structure so that the conductor is connected to the electrodes, or the electrodes can partially extend outside the firespace via the duct, which may allow for lower heat resistance of the conductor compared to when the conductor is located within the firespace. Alternatively, rails can be used within the duct for electrical connections, and these rails are exposed to the highest temperatures. Using rails compared to cables has advantages in terms of conductor lifespan and fault tolerance.

[0071] For the device 10 to operate, it is essential that each electrode 16 of the device 10 be covered with an insulator 24 to prevent particles from accumulating directly on the contact surface of the electrode 16. This is essential to prevent the electrodes from being completely short-circuited by the plasma formed by the flame. Since the electrodes and insulators are located within the flame region or in a high-temperature region adjacent to it, the selection of the insulating material is important for the durability of the insulator. The electrodes extend from the fire space through the walls to the outside of the fire space, allowing cooler air to flow through the electrodes to the ends of the electrodes between the electrodes and the insulator, while the hotter air from the electrodes is removed from the inside of the insulator through the space between the electrodes and the insulator. The thickness of the insulating layer used in this case can be set to 0.5 to 5 mm, preferably 1 to 2 mm. To compensate for the highest thermal peak, thermal shielding with a covering material or other incidental material may be used in conjunction with the base insulation of the electrodes.

[0072] Mica insulators can and are preferred as insulators. Mica, or the silicate minerals known as mica, are heat-resistant even without cooling. The thickness of the mica insulator layer can be set to 0.5 to 30 mm, preferably 5 to 20 mm. From the viewpoint of durability, using a large insulating layer of 5 to 20 mm with mica insulators allows the thicker outer layer to protect the interior. The temperature within the flame region reaches 800 to 1200°C. Mica insulators are suitable for operating temperatures of 600 to 800°C and can therefore be set at a suitable distance from the flame.

[0073] Instead of mica insulators, HBN (hexagonal boron nitride), CFRC (carbon fiber reinforced carbon), C / C (carbon-carbon), or RCC (reinforced carbon-carbon) composite materials, in which carbon fibers are mixed into a graphite matrix, can also be used as insulators. While these composite materials are currently very expensive, they are expected to become more price-competitive in the future.

[0074] For the electrode material, for example, stainless steel can be used, or other materials suitable for the target application can be used, such as carbon-based compounds like glassy carbon whose conductivity improves as the temperature rises to the operating temperature.

[0075] Figure 2 shows a second embodiment of the apparatus 10 according to the present invention. This apparatus 10 has a single rod-shaped electrode 16. The advantage of the rod-shaped electrode lies in its small surface area, which has little effect on the flue gas flow in the fire space. On the other hand, this electrode has a smaller functional surface area for collecting particles on its insulating surface than a flat electrode. However, the surface area of ​​the electrode is of little importance because most of the particles accumulate on the surface of the collecting body.

[0076] As shown in Figure 1b, two rod-shaped electrodes 16 are provided with the same polarity and spaced apart from each other. When using two electrodes, the same power supply can be used.

[0077] Alternatively, two parallel power supplies can be used. Each power supply can be designed and configured to be sufficiently compact in terms of its physical dimensions.

[0078] In its simplest form, the power supply used in the device according to the present invention can be configured as a grid power supply having grid power of 100-240V in a frequency range of 50-60Hz at the time of use. This grid power supply is connected to a transformer. Incidentally, the transformer 30 has, at least preferably as shown in Figure 1a, a rectifier circuit 34 that converts the power supply voltage to a voltage supplied to electrodes on the order of kV, and an AC / DC converter 36 that converts the power received by the device to the level required by the electronic equipment. The transformer has a controller that controls the voltage supply in a desired manner, a safety circuit that protects the user and the device, and diagnostic functions such as indicator LEDs that show the user the operating status and potential fault conditions of the device. Another user interface (UI) that controls the performance of the device and displays status information or alarms to the user can be implemented wirelessly, for example, as a mobile application. The controller, basic diagnostic functions, and user interface are not shown. Instead of a controller, it is possible to use a power supply in which the controller manages both current and voltage based on a control curve and calibration.

[0079] The status data of the devices can be linked, making it useful when building management systems for target organizations such as holiday villages with multiple fire spaces. In a modified embodiment, the status data can be used to infer whether a fire space is in the combustion or cooling phase, and this data can be used to perform further calculations, for example, regarding emission measurement or monitoring, or to calculate operating time. This status data can then be transmitted to, for example, a home heating system using IoT technology, so that when a flame burns in a fire space, the building's central system can proactively suppress other combustion, even if, for example, the temperature sensors in each room have not yet reacted to the heat generated in the fire space.

[0080] As a controller, for example, a microcontroller can be used, and the device control is based on programmed sequences and functions such as the flame temperature setting when the device is activated, as well as on received signals. For controllers requiring more advanced functions or calculations, FPGA controllers (Field Programmable Gate Arrays) can also be used. The controller can output low-level device diagnostics to the user using, for example, another LED signal or similar means, and also enable more detailed diagnostics for the manufacturer. For safety circuits, partially direct or tripping protection circuits can be used.

[0081] In one embodiment, the apparatus according to the present invention can be implemented using commercially available solutions. In the first embodiment, the high voltage generated by the apparatus is produced by an experimental power supply. Existing power supplies capable of generating kV-class DC voltages at low currents are very expensive and usually need to be ordered from specialists in the field. Furthermore, the physical size of these power supplies is considerably larger than products suitable for real-world environments, such as consumer applications. An example of an experimental power supply is the ST225. * It was released commercially in 2010 and is an ST series model manufactured by SPELLMAN HIGH VOLTAGE ELECTRONICS CORPORATION.

[0082] Alternatively, implementation can be carried out by integrating commercially available solutions. In this case, the power supply would be a commercially available product in the YD series, product name YD-044S, manufactured by Yui Da Electrics Co., Ltd. While integration of commercially available solutions at the component level is possible, it is difficult because the components cannot be optimized for each other. Alternatively, the device could be implemented using hobby-grade or industrial-sized commercially available components.

[0083] In all embodiments, the power supply includes the necessary transformer. The transformer used is a transformer manufactured by Osram and commercially available under the product name OT FIT8 / 220~240 / 180CS PC SC from the OPTOTRONIC series. The controller used is the Curiosity 8-Bit Development Board / DM164137 from the Curiosity Development Board series, manufactured by Micro Technology. In this case, any metal or steel electrode of a size suitable for the application can be used as the electrode, and the insulator used is the Alumina Single Bore Tubes series model ASB00809, manufactured by LSP Industrial Ceramics Inc.

[0084] As a user interface, for example, one can be implemented through the application panel or display panel of a mobile device. These panels allow the user to check the status or function of the device, as well as operating time and other incidental information, such as diagnostic data in case of a malfunction.

[0085] The voltage level used for electrodes along with direct current (DC) is 1kV to 100kV, preferably 10 to 30kV. At voltage levels that are too low, no particle collection effect is observed. At voltage levels that are too high, safety measures and insulating materials, as well as user safety measures, become necessary, and the electrical energy used by the device increases. Instead of a single static voltage value, the voltage level can also be controlled, for example, in relation to the temperature of the firebox, or by other control circuits or modeled control curves.

[0086] Instead of using pure DC current, it is also possible to use pure AC current, and it is also possible to supply different pulse waves along with the base voltage.

[0087] Instead of using grid power as the power source, the device according to the present invention can also be implemented using a thermoelectric power source, i.e., a thermoelectric generator. As already described, the wattage required for the device according to the present invention is only a few watts or tens of watts. Power is consumed when the insulator is charged, similar to a capacitor, and when there is a loss of power in the electronic equipment. Almost no energy is consumed to maintain the electric field itself. The thermoelectric power source can utilize the Seebeck effect. In this case, the power source generates electricity based on the temperature difference. The amount of power generated depends on the magnitude of this temperature difference. Part of the power source is located at least partially outside the fire space where the temperature is lower, and the second part is located inside the firebox where the temperature is several hundred degrees Celsius.

[0088] Although the electrodes 16 shown in Figures 1a to 4 are presented as separate elements to be installed inside the firebox 14, the present invention also allows for implementation using electrodes incorporated into the structure of the fire space. For this purpose, the steel material of the electrodes can be incorporated into the bricks or other wall members that form the walls of the firebox.

[0089] Alternatively, as shown in Figure 3, the electrode 16 can be attached to the flue gas air guide 50, and the electrode can be incorporated into a guide structure that guides the flue gas in the fire space. In this case, the fire space 12 is the sauna stove 42.

[0090] The fire space according to the present invention is a fire space on which the apparatus according to the present invention is installed. Preferably, this fire space is a so-called batch-fuel type fire space. That is, the heat output generated by the fire space is a maximum of 2 to 50 kW, preferably 4 to 15 kW. This fire space is intended for batch combustion of wood or wood-based products such as pellets.

[0091] In one embodiment, the apparatus according to the present invention can be configured with a control means 37 having a controller 39 that adjusts the magnitude of the leakage current according to the combustion state. Since the combustion temperature and the temperature of the firebox vary with different combustion states, the insulating capacity of the insulator and its insulating capacity against leakage current also change. In the first embodiment shown in Figure 1a, the control means 37 can be implemented to optimize the leakage current under different conditions by converting the supply of current or voltage or both by a controller, preferably controller 39, of the power supply 22. When the temperature of the firebox decreases, the insulating capacity of the insulator decreases, but this decrease can be compensated by increasing the voltage to supply sufficient leakage current and efficiently charge the particles. Alternatively, when the temperature of the firebox rises and the insulating capacity of the insulator decreases, the current can be limited to avoid failure.

[0092] In the second embodiment shown in Figure 1b, the magnitude of the leakage current is affected by the movement of the electrode 16, which changes the length of the air gap 33 between the electrode 16 and the insulator 24. For this purpose, the electrode 16 can be connected to an actuator 41. This actuator 41 is, for example, a spindle motor that moves the electrode 16 inside the insulator 24 relative to the plug 29 of the insulator 24. When the temperature of the firebox rises, the air gap 33 lengthens, and when the temperature falls, it shortens. The actuator 41 can be controlled by a controller 39 configured in the control means 37. A PID controller is preferred as the controller.

[0093] In the embodiment shown in Figure 5, the electrode 16 is a T-shaped electrode, thus covering a large area of ​​the flue. Alternatively, an L-shaped electrode or an electrode of a similar shape can also be used.

[0094] The length of the electrode in the apparatus according to the present invention is preferably 10 to 60 cm when it is rod-shaped, and the diameter can be set to 1 to 20 mm, preferably 8 to 12 mm. On the other hand, when the electrode used is flat, the height can be set to 10 to 100 cm, the width to 10 to 60 cm, and the thickness to 0.5 to 12 mm. The total thickness of the electrode and the insulator can be set to, for example, 30 to 50 mm. The position of the electrode should be set so that the electrode is at least partially in contact with the flame or is close to a flame whose temperature exceeds 500°C. The grounding surface used should be smaller than the electrode and preferably located within the region of the electric field generated by the electrode.

[0095] The apparatus according to a preferred embodiment uses a 30kV power supply voltage and is implemented using a 10mm steel tube as the electrode and a mica mixture as the insulating material, taking the form of a tube with an outer diameter of 30mm and an inner diameter of 10mm. The mica mixture contains a mixture of 90% natural mica powder and 10% synthetic resin binder, such as silicone or epoxy. An example of such a mixture is the insulating material known as Micanite, manufactured by Dumico. Furthermore, the tube forming the insulator of the apparatus has a 10mm thick plug and an adjustable air gap between the electrode and the 30mm long plug. In such a structure of the apparatus, the leakage current is approximately 1mA and the cleaning efficiency is 75%.

[0096] In embodiments that do not form part of the present invention, the apparatus according to the present invention, scaled according to the intended application, can be used in batch-fueled firespaces and continuous-burning firespaces in boiler size classes. [Explanation of Symbols]

[0097] 10 equipment 12 Firespace 14 Firebox 15 particles 16 Electrode, cathode 18 Flames 20 Ground plane 22 Power supply 24 Insulator 25 collector 26 Surface 27. Sheath 29 plugs 30 Transformers 31 Electrode ends 32 plane 33 Air gap 34 Rectifier circuit 36 AC / DC Converters 37 Control means 38 Wall 39 Controller 40 Fireplace 41 Actuator 42 Sauna stove 44 Metal Plates 46 Wood 48 Great (fire grate) 50 Air Guide 52 doors d distance E electric field S Flue gas V Voltage

Claims

1. A device (10) for reducing particulate matter emissions from flue gas (S) in a fire space (12) having a firebox (14), The device (10) is An electrode (16) is located within the region of the flame (18) or within a firebox (14) immediately adjacent to the flame (18), and forms an electric field (E), which moves particles (15) charged by the flame (18). An insulator (24) covers the portion of the electrode (16) exposed to flue gas (S) to prevent the electrode (16) from becoming contaminated. ground plane (20), A collector (25) for collecting charged particles (15), and The electrode (16) is connected to a power supply (22) that generates a voltage of 1 to 100 kV, preferably 10 to 30 kV, and generates the electric field (E) between the electrode (16) and the ground surface (20). The power supply (22) and the insulator (24) are configured to generate corona discharge through the insulator (24) of the electrode (16) to charge the particles (15), and to generate a leakage current of 0.001 mA to 5.0 mA, preferably 0.1 mA to 5.0 mA, more preferably 2.0 mA to 3.0 mA, through the insulator (24), and the insulator (24) and the collector (25) act as collection surfaces for the charged particles (15), and oxidize the particles (15) under the effect of temperature. A device (10) characterized by the following.

2. The apparatus according to claim 1, wherein the power supply (22) has a transformer (30) that converts the voltage of the grid current supplied to the power supply (22) to a voltage of 1 to 100 kV, preferably 10 to 30 kV.

3. The apparatus according to claim 1 or 2, wherein the collecting body (25) is the ground surface (20).

4. The apparatus according to any one of claims 1 to 3, wherein the insulator (24) is configured based on one or more of the following characteristics of the insulator (24) with respect to a selected leakage current: the thickness of the insulator (24), the material of the insulator (24), the length of the air gap (33) between the insulator (24) and the electrode (16), the discontinuity of the insulator (24), and the shape of the insulator (24).

5. The apparatus according to any one of claims 1 to 4, wherein the electrode (16) is rod-shaped.

6. The apparatus according to claim 5, wherein the insulator (24) comprises an outer casing (27) configured to partially surround the rod-shaped electrode (16), and a plug (29) provided within the outer casing (27) configured to surround the end (31) of the electrode (16).

7. The apparatus according to any one of claims 1 to 6, wherein the insulator (24) of the electrode (16) is made of a material having a crystalline structure that recovers after corona discharge.

8. The apparatus according to any one of claims 4 to 7, wherein the insulator (24) is a mica insulator.

9. The apparatus according to any one of claims 1 to 8, further comprising an incidental insulator (54) that covers a portion of the electrode (16) passing through a duct (56) formed by the fire space (40) and introduces the electrode (16) into a fire box (14).

10. The apparatus according to any one of claims 4 to 9, wherein the incidental insulator (54) is aluminum oxide.

11. The apparatus according to any one of claims 1 to 10, wherein the apparatus (10) has a control means (37) equipped with a controller (39) that adjusts the leakage current according to the fire state, and the control means (37) has an actuator (41) that moves the electrode (16) into the insulator (24) and adjusts the air gap (33) between the electrode (16) and the plug (29) based on the control of the controller (39).

12. A fire space (12) having a firebox (14) for burning fuel, preferably wood, and a device (10) for reducing particulate matter (15) from flue gas (S), wherein the device (10) is the device (10) according to any one of claims 1 to 11.

13. The fire space according to claim 12, wherein an electrode (16) is provided in a firebox (14) in the region of the flame (18) or in a region adjacent to the flame (18) where the temperature is 500°C or higher, and the particles (15) on the surface (26) of the insulator (24) of the collector (25) and the electrode (16).

14. A method (10) for reducing particulate matter emissions from flue gas (S) in a fire space (12) having a firebox (14), A power supply (22) connected to the electrode (16) generates a voltage difference of 1 to 100 kV, preferably 10 to 30 kV, between the electrode (16) and the ground surface (20), and an electric field (E) is generated in the firebox (14) by the electrode (16) positioned within the flame (18) region or immediately adjacent to the flame (18), and the particles (15) charged by the flame (18) are moved toward the electrode (16) by the electric field (E). At least a portion of the electrode (16) exposed to the flue gas (S) is protected by an insulator (24) to prevent the electrode (16) from becoming contaminated. Charged particles (15) are collected by a collector (25) located within the flame (18) region or within a firebox (14) immediately adjacent to the flame (18). A leakage current of 0.001 mA to 5.0 mA, preferably 0.1 to 5.0 mA, and optimally 2.0 to 3.0 mA, is introduced from the electrode (16) through the insulator (24), causing a corona discharge through the insulator (24) to charge the particles (15). The collected particles (15) are oxidized under the effect of temperature. A method characterized by the following:

15. The method according to claim 14, wherein the magnitude of the leakage current is adjusted according to the fire state by a controller (39) configured by the control means (37) of the device (10).

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