DK179332B1 - Electrofilter - Google Patents

Abstract

Electrofilter comprising a housing with an inlet for supply of flue gas / process air and an outlet for exit of purified flue gas / process air in which a rotatable shaft is arranged on which shaft is arranged a number of parallel electrically conductive plates adapted to act as cathodes where a number of conductive wires acting as anodes are placed between the cathode plates. A higher efficiency of the filter is achieved by the electro-filter comprising a device for regulating, distributing and dividing the flow of the flue gas from inlet to outlet.

Description

< ¹ θ> DENMARK (10)

< ¹² > PATENT WRITING

Patent and

Trademark Office (51) IC: B 03 C 3/36 (2006.01) B 03 C 3/08 (2006.01) B 03 C 3/10 (2006.01)

B 03 C 3/47 (2006.01) B 03 C 3/74 (2006.01) (21) Application number: PA 2016 00429 (22) Filing date: 2016-07-17 (24) Running day: 2016-07-17 (41) Aim . available: 2018-01-18 (45) Patent Notice bkg. on: 2018-05-07 (73) Patent holder: MACHINE FACTORY REKA HOLDING A / S, Vestvej 7, 9600 Aars, Denmark (72) Inventor: Christian Larsen, Østermarken 29, 9600 Aars, Denmark

Niels E. Linnemann Nielsen, Stenildhøjdalen 12, 9600 Aars, Denmark (74) Plenipotentiary: HØYER PATENT ApS, Højbovangen 36, 9200 Aalborg SV, Denmark (54) Title: Electrofilter (56) Published publications:

US 5084077 A EP 1892044 A1 EP 1721678 A1 DE 4326757 A1 CN 203972139 U US 2001039877 A1 (57) Summary:

Electrofilter comprising a housing with an inlet for supply of flue gas / process air and an outlet for exit of purified flue gas / process air in which a rotatable shaft is arranged on which shaft is arranged a number of parallel electrically conductive plates adapted to act as cathodes where a number of conductive wires acting as anodes are placed between the cathode plates. A higher efficiency of the filter is achieved by the electro-filter comprising a device for regulating, distributing and dividing the flue gas flow from inlet to outlet.

To be continued ...

in

ELECTRO FILTER

The present invention relates to an electrofilter of the kind set forth in the preamble of claim 1.

More particularly, the invention relates to the precipitation of harmful substances and dust from flue gas formed by the combustion of fuel in a combustion furnace, or of particles in process air from production.

Incinerators are well known and widely used. A combustion furnace generates heat when burning fuel. The fuel can be a raw material or a waste product.

For the sake of the surrounding environment, it is a desire that the fuel be converted as completely as possible and without the formation of toxic substances. Air supply control and combustion temperature have a major impact on the formation of toxic substances. Toxic substances produced by combustion are retained in the slag or released to the environment with the flue gas / process air.

As society's desire for a transition to sustainable resources increases, alternative fuels are being sought. For example, one is seeking to use rapidly growing crops such as elephant grass or willow chips. Cereals or grains from rye, barley, triticale or canola are also examples of fuels used. It is also sought to use the residual straw from grain cultivation as fuel.

It is a given that some of the above fuels are more combustible than others. Straw burning provides good heat but unfortunately a large emission of dust in the form of fine and ultra fine particles in the size of 0.1 to 1 pm. Since these particle sizes are suspected of causing lung damage, it is a desire to reduce or, if possible, eliminate the emission of particles into the environment. This is supported by upcoming regulatory requirements where it is expected that the limit value will be set as low as between 20 - 40 mg / nm3 at 10% oxygen.

Particle removal can be effectively done with scrubber, filter, possibly. The use of the cost of the residual product as a bag or with an electric filter.

scrubber has disadvantages in terms of shape and the surrounding environment including

In addition, water and chemistry provide. the residual product, which is aggressive in liquid form, has high requirements for material selection in the plant, which would otherwise wear out quickly. Bag filters give great pressure loss and have lower efficiency. Pressure loss increases rapidly when packing particles in the bag, which negatively impacts reliability. Scrubber and bag filters are also relatively expensive solutions in installation and operation, so it would be desirable to find an effective alternative in an electric filter if this could be applied and achieve greater efficiency and reliability as well as economy.

An electrofilter consists basically of an airlock in which anodes are placed, typically in the form of conductive wires with a counterpart in conductive metal plates forming cathode. The anode and cathode are connected to a power supply that supplies a voltage in the range of 20 to 100 kV. The power supply comprises a transformer and a rectifier circuit so that a pulsating or even voltage is obtained. The even voltage can also be superimposed with a short-lived pulsed voltage to better penetrate the dust layer. The particles are ionized by passage past the electric field and are attracted by the conductive metal plate constituting the cathode and can be removed relatively easily, for example, by knocking on the plate, which must be done at regular intervals.

Speaking of electro filters, they are extremely effective in removing dust and including fine and ultra fine particles. Therefore, electric filters are widely used in industry and in waste incineration. In ordinary waste for incineration, the flue gas contains the full range of particle sizes and since there is also some carbon in the dust, the cathode plate retains its effect even when a layer of dust is trapped on it. This is because the dust layer has electrically conductive properties in the same way as the cathode plate. An example of a smoke filter electro filter is known from US5084077A to LTV Lufttechnik GmbH. Here, it is claimed that the efficiency of the filter can be increased by aligning the tab of the flue gas in a direction towards the central region of the cathode plate, whereby the flue gas has the greatest migration across the surface of the cathode plate and thereby greater opportunity for attraction of particles. However, it has the consequence that the heat distribution over the area of the cathode plate is dissimilar to the disadvantages it must cause. Furthermore, it is given that the greater flow in the middle region places greater demands on the anode for particle charging as well as for the cathode plate for attracting particles due to greater flow and particle density in the concentrated flue gas tab.

However, the fine and ultrafine particles formed by burning straw consist of a large proportion of calcium chloride and are both light in weight and highly resistive, ie electrically insulating, which is why the effect of an electric filter decreases rapidly. This is because the cathode plate is quickly packed with ultra-fine and light dust that cannot be knocked off the plates. Furthermore, the dust is packed so hard on the cathode plate that it is difficult to remove. Therefore, it is generally known that electro filters are not considered suitable for smoke cleaning of smoke from the burning of straw or the like. A further disadvantage is that the power supply is loaded when the electrically insulating dust layer and thus the back radiation effect translates to short-circuiting and supply.

In order to solve the challenge, attempts have been made to supplement with other fuels, such as wood chips, which improve the smoke cleaning of the fine and ultrafine particles by lumping them into the larger particles, which are more easily removed from the filter by knocking. Although there is an improvement, the problem of isolating the cathode plate is still not solved as the fine and ultra fine particles continue to pack on the cathode plate.

In view of the drawbacks outlined, a solution is needed to improve the continuous cleaning performance of an electric filter when the flue gas contains large amounts of resistive fine and ultrafine particles.

Furthermore, it is also a desire to provide a simpler and more compact system with the advantages it has, but also with a view to cheaper production and cheaper transport to the installation site.

The object of the invention is therefore to provide an electrofilter which is more compact but persistently effective in removing fine and ultra fine resistive particles from flue gas or process air.

This is achieved according to the invention by, to shape electrostatic precipitator electrostatic precipitator as specified in comprising: requirements 1 by

- a cabinet with:

- an inlet for the supply of flue gas;

- an outlet for the discharge of purified flue gas;

a suspension arranged between inlet and outlet adapted to carry a pivotal shaft on which shaft is arranged a plurality of parallel electrically conductive plates adapted to act as cathodes;

- a motor for rotating the pivot shaft;

an arrangement for retaining a plurality of conductive wires which act as anodes and for arranging these wires so as to pass through the area between the cathode plates;

- a power supply with anode and cathode connection,

The electro filter comprises a device for regulating, distributing and dividing the flow of the flue gas from inlet to outlet.

Studies on prototype electric filters have shown that the distribution of the flue gas through the electric filter has a major influence on the continuous operation of the filter, as temperature differences will cause the metallic parts to deform. In particular, it has been seen that the cathode plates, which for practical reasons for being able to rotate about their axis, are formed within a circle in the shape of the cabinet, settle in uneven heat distribution. A higher temperature in the center of the electrofilter in the center of the cathode plates relative to the periphery of the cathode plates will mean that the cathode plates are subjected to internal mechanical stresses causing them to deform. At best, the slices become a little crooked or uneven. At worst, the plates become shaped. It may be in whole or in part over a stretch. This poses major challenges in maintaining a constant distance between anode and cathode and avoiding overestimation or direct short circuits. When estimated, it drastically reduces the efficiency of the electro filter and can cause the filter to break down. Another disadvantage is that the removal of dust attracted to the cathode plate is difficult to remove from skewed or plate-shaped cathode plates where an adaptive scraper is difficult to manufacture.

The solution according to the invention, which, in controlling, distributing and dividing the flow of the flue gas from inlet to outlet to ensure a uniform temperature distribution in the electro filter to prevent deformation of the cathode plates, may comprise one or more screens inserted in the inlet for supply of flue gas to the electro filter. The screens can thus divide the flue gas flow into layers or sections and direct the flow in the right direction so that the flue gas is distributed at the same pressure and thus temperature throughout the cabinet.

Conveniently, the plates are inserted into several sections. A first section in which the flue gas is fed through a relative pipe from the combustion part where an inlet is formed as a funnel with inserted plates for spreading the flue gas so that the flue gas at the mouth of the hopper is evenly distributed over the entire area of the outlet. The area of the outlet may reflect the interior width of the cabinet. This ensures a uniform rate of smoke in the cabinet so that all cathode plates are coated with the same amount of flue gas. The flue gas is introduced from above and directly down towards the bottom of the cabinet but can also be introduced at other angles, for example from the bottom. As the flue gas is hot it will search upwards. Therefore, blowing from the top to the bottom is advantageous. In order to further ensure the spread of the flue gas throughout the height of the cabinet, at various heights, plates are inserted which distribute the flow of flue gas from the inlet in a predominantly horizontal direction. It should be understood that in order to ensure that the flue gas is also distributed at the bottom of the cabinet, the screens may be angled so that they regulate the flue gas down towards the bottom. This counteracts the tendency for the hot flue gas to rise to the top of the cabinet due to the thermodynamics.

Furthermore, the invention further comprises a step adapted to regulate the distribution of the flue gas in the cabinet. In order to achieve better control and distribution of the flow of flue gas through the electric filter, the electric filter comprises in one embodiment at least one plate with a number of holes for flue gas passage arranged in a position between inlet and outlet so that the flow of flue gas through the holes is controlled. and evenly distributed between the cathode plates. An analysis of the flow of flue gas through the electro filter at different loads can determine the precise sizing of holes and their location. Multiple plates can be inserted into the cabinet at desired positions and angles to regulate the direction and distribution of the flue gas in order to obtain an even temperature distribution in the cabinet. It is noted that the regulation of the flue gas flow further intends to have as large as possible disposal of flue gas to the electric field between anode and cathode and thereby have a greater cleaning effect against dust in the filter.

In one embodiment, the device comprises at least one plate having a plurality of flue gas passage holes arranged in a position between the cathode plates such that the flow of flue gas upon passage through the holes is regulated and evenly distributed between the cathode plates. This position is desirable as the distribution of the flue gas is particularly important over the surface of the cathode plates in order to avoid temperature differences across the surface of the plate and resulting mechanical stresses and distortions. In a typical embodiment of this, the plate is arranged in the cabinet in a vertical direction relative to the flow of the flue gas from inlet to outlet through the electro filter.

It will be appreciated that the size and location of the holes are disposed for an even distribution of the flue gas between the cathode plates. This can be assured partly by measurements on specific embodiments. Furthermore, simulation programs can be used in connection with specific designs.

The device in the form of the flue gas flow regulating plate may in one embodiment be arranged in the housing outside the area where the cathode plates are arranged. In yet another embodiment, the plate is provided with recesses or grooves through which at least part of the cathode plates can be passed through.

In yet another embodiment, a distributor plate is arranged in connection with, preferably on or above, the device in the form of the plate for regulating flue gas flow. The distributor plate is mounted over the opening (s) in the flue gas regulation plate. This means that the device in the form of the flue gas flow regulating plate can be designed with one or more passages covered by the distributor plate. This makes it easier and easier to change the regulation of flue gas flow to the specific application and application. It is possible to measure the flue gas flow through the filter and subsequently calculate and design a distributor plate for mounting on top of the flue gas flow control plate, which distributor plate optimizes the function of the electric filter for the specific purpose.

In one embodiment, the device in the form of the flue gas control plate is itself or with a mounted distributor plate retained relative to the housing but is in movable contact with at least one cathode plate arranged on the pivot shaft and is adapted to act as a scraper upon contact with the cathode plate.

In yet another embodiment, the device is provided with a curved edge where the edge acts as a scraper. Conveniently, the scraper is formed of a flexible material and is arranged resiliently suspended in contact with the cathode plate. In order to obtain a good scraping effect, the scraper is arranged in contact with the cathode plate such that the curvature of the edge is made so that the edge forms a sharp angle to the direction of rotation of the cathode plate and thus acts as a cutting knife edge with respect to the rotation of the cathode plate. As previously mentioned, the cathode plate is quickly packed with the fine and ultra fine dust particles which form a hard layer which is electrically insulating, which is why the effect of the electrofilter decreases rapidly. A layer of 0.1 mm is thus enough to reduce the efficiency of the cathode plate's ability to attract dust and render the electrofilter unusable in practice. Studies have shown that the surface structure of the cathode plate is a major part of the explanation of why the fine and ultra fine particles bind so hard to the plate. Seen in a microscope, the plate is rough and filled with small holes and projections relative to the fine and ultra fine particles, which have fine structures in which the fine and ultra fine particles can pack. The cathode plate can not be completely cleaned of the fine and ultra fine particles by scraping why there is a fine thin and ultra hard layer of approx. 0.001 mm. Very surprisingly, it has been found that the ultra-hard thin layer is not electrically insulating but has substantially the same efficiency in terms of capturing particles as a new and unused cathode plate. It has been found that this effect is also achieved by compressing the fine thin and ultra hard layer. Concrete measurements have shown that an embodiment of a scraper pressing against the cathode plate having a force greater than 5 N / cm has a sufficient effect on removing the embroidery portion of the fine and ultrafine particles which have settled on the cathode plate and for compressing the remaining thin layer. .

In one embodiment, the scraper contains soft-grained stainless steel of the type designated 304. A plate thickness of between 0.5 and 2 mm has proved suitable where a thickness of 0.7 mm has proved most suitable for obtaining the desired resilient effect. The scraper has shown good function at a curved edge of 40 mm.

In one embodiment, the scraper is arranged in the side of the cabinet facing the inlet. When the particles are removed, it is possible that the flow of flue gas swirls the fine and light particles up before falling into a collection unit at the bottom of the cabinet. By having the scraper arranged in the inlet, the filter can handle any. particles that are scraped off the cathode plate and swirled up by the flue gas and capture these particles again, minimizing the amount of particles released into the outlet.

In yet another embodiment, the scraper is arranged in contact with the lower semicircle of the cathode plate. Scratching only particles from the lower semicircle prevents the particles from falling a long distance away from the collection unit at the bottom of the cabinet. It reduces the amount of particles that are swirled up and thereby the amount of particles released into the outlet.

Cathode plates are made of an electrically conductive material which may be, for example, metallic or ceramic. The material must be capable of withstanding the temperatures it is exposed to in the electro filter.

In one embodiment, the cathode plates are made of fine-grained alloy steel, which is rust-repellent in that the chromium content of the alloy in particular forms a protective surface which is nonetheless electrically conductive. A trade designation for the selected steel type is Cor Ten. It also has the English term weathering steel as it is used for facades on buildings and is characterized by its rusty red patina. A commercially available product useful for cathode plates is CORTEN A EN 10025-5 or Cor-Ten A / S355 JOW.

A suitable steel plate quality has a roughness of 2B with an Ra of approx. 0.3 microns and a Rz of 2.9 microns.

In one embodiment, the cathode plates have a thickness between 3 and 12 mm where a particularly appreciated thickness is 6 mm. This thickness is relatively easy to process and has so much heaviness and thermal conductivity that it is easier to avoid or minimize mechanical stresses that can lead to skew or plate shape. The diameter of the plate may in one embodiment be between 30 cm and 300 cm. In a particularly appreciated embodiment, plate thickness is adjusted to 6mm with a diameter of 150 cm.

Furthermore, it has been found that a cathode plate made of fine-grained alloy steel (COR TEN A) and a scraper made of soft-grained stainless steel (304) have good cooperative properties in removing particles from the cathode plate. Since the scraper is made of a softer material, it will wear out more than the cathode plate and not make any traces in the cathode plate. When the scraper is worn so much that it no longer presses with the necessary pressure against the cathode plate, it can be easily replaced with a new and affordable scraper. The scraper made of soft-grained stainless steel (304) also has good elastic and resilient properties, which allows the scraper to be in resilient contact with the cathode plate. If the scraper is arranged such that the spring force against the cathode plate is 5N / cm, tests show that the scraper works optimally. A spring force between 2N / cm and 10N / cm has an acceptable effect. A spring force exceeding 5N / cm is effective but results in greater abrasion of scraper and cathode plate.

Since the ability of the cathode plate to attract particles is determined by the electrical conductivity of the cathode plate and the ability to clean depends on the smoothness of the particles, a particular embodiment is devised. A metal plate is inherently rough and has a surface filled with small projections and small valleys where there are crevices and small holes in projections and valleys. The fine and ultra fine particles are trapped and can easily be released from these voids again. In order to make the surface smooth and thereby prevent particles from being trapped in voids, the plate in a stainless steel plate which is embodiment is electropolished.

is

Electropolishing is a treatment of the surface of a metal plate with a mixture of chemistry and electrical influence, after which the plate appears smooth and glossy.

In another embodiment, the cathode plate is coated or applied to an electrically conductive coating. The electrically conductive coating may be metallic or ceramic or a combination thereof. A coating consisting of smaller particles than the fine and ultrafine particles that are desired to be trapped will be particularly suitable as the fine and ultrafine particles in size will be more difficult to adhere to the surface. A coating of the cathode plates with an electrically conductive ceramic coating of nanoparticles is thus a suitable solution.

Thus, a cathode plate with a surface coated with nanoparticles will be easier to clean why the scraper is redundant and can be replaced with a brush with hair of a heat-resistant material. For example, the brush's hair may be made of copper, brass, steel but possibly. also of ceramic fibers.

Measurements have furthermore shown that the design of the edge of the cathode plate has a bearing on the efficiency of the electro filter. Thus, it has been found that a cathode plate having a rounded edge is more repellent to impact. Estimates are based on sharp edges and projections. During operation, a layer of particles may build up on the edge of the cathode plate. Although the area of the edge is negligible with respect to the area of the cathode plate, it has been found that cleaning of the edge is important to avoid overstating and that the efficiency of the electrofilter is increased by keeping the edge clean. Therefore, in one embodiment, the electrofilter comprises a scraper arranged in the housing in a position where it contacts the edge of a cathode plate and arranged to keep the edge free of particles by rotation of the plate.

In one embodiment, the scraper is specially adapted to act as a scraper against the round edge of the cathode plate by being formed with a corresponding circular shape which scrapes the entire semicircle of the round edge of the cathode plate.

Further features of the invention will become apparent from the following embodiment of the invention, which will be described in the following with reference to the accompanying drawings, in which:

FIG. 1 is a front view of an enclosure with a filter; FIG. 2, a cross-section A-A seen through the housing; FIG. 3, a cross-section B-B seen through the housing; FIG. 4, an inlet distributor screen; FIG. 5, a section C-C seen through the inlet; FIG. 6, a distributor plate for adjusting flow through the housing; FIG. 7, a profile of the edge of a distributor plate acting as a scraper; FIG. 8 is an enlarged view of the surface of a cathode plate; FIG. 9 is an enlarged view of the surface of a cathode plate with particles; FIG. 10 is an enlarged view of the surface of a cathode plate treated with electropolishing; and FIG. 11, a detail of the edge of a cathode plate and a scraper thereof.

As shown in FIG. 1, which shows a housing 2 for an electrophilic filter 1, an inlet 3 is shown on the left, where the flue gas which is desired to be cleaned of particles is supplied. The purified flue gas is fed out of the cabinet via an outlet 4 and on to a chimney (not shown). On the front of the cabinet there is a control 5 and a motor drive 6 with a gear. Motor drive 6 provides for rotating cathode plates 7 shown in FIG. 2 showing a section through the longitudinal direction of the housing 2. The cathode plates are suspended on a shaft 8 arranged in a bearing 9 on both sides of the housing 2. As an anode a number of metallic strings 10 are suspended in a frame 11, which frame is held at the top and bottom of the cabinet 2 and keeps the strings clamped so that they do not engage with or too close to a cathode plate 7 as otherwise it may cause overstating.

If you analyze the flow of the flue gas through the filter you will see that the distribution of the flue gas will follow the course where there is least resistance. This means that an unregulated flue gas will search towards the center of the cabinet 2 in an upward flow which depends on the flue gas rate determined by the combustion furnace's power in relation to the flue gas discharge conditions, especially the pressure loss in the piping, filter and chimney. Therefore, the efficiency of the filter without regulating the flue gas flow is not optimal. Furthermore, the parts that are in the part of the flue gas process which can be referred to as the smoke tab are heated more than the other areas of the cabinet, which causes a risk of tension and deformation of the materials where especially a deformation of the cathode plates 7 is problematic in connection with cleaning them.

Thus, it is important for the shape stability of the cathode plates 7 that the flue gas is evenly distributed in the cabinet so that the temperature distribution in the cabinet is not excessive. If the temperature of the cathode plates differs across the distribution they will settle and it will be difficult to keep them clean. There will also be a greater risk of overshoot between anode strings 10 and cathode plates 7. To ensure a homogeneous temperature distribution in the cabinet 2, inlets 3 are inserted screens 12 which regulate, distribute and divide the flue gas flow from inlet 3 towards the surface of the cathode plates 7 A detail view of a screen according to the invention is shown in FIG. 4. As can be seen from FIG. 5, which shows a section in inlet 3, the inlet is provided with a plurality of plates 13 which distribute the smoke in the inlet over the entire width of the filter. This gives a uniform velocity of smoke through the filter without turbulence and also a uniform heat distribution throughout the filter. Since the cathode plates 7 are not constantly rotated but only at intervals to clean the plates, obtaining an even heat distribution through the filter is important, since otherwise the cathode plates are at risk due to uneven heating and becoming irretrievably skewed, the cathode plates 7 become skewed, which means that the cathode plates are difficult can be kept clean with a scraper as well as changing distances between the anode and cathode which can cause power overload and filter breakdown.

To further ensure a good distribution of heat through the filter, a top of bottom cabinet 2 includes a smoke plate 14 (shown in Figure 2 and Figure 3)) where cutouts 15 are made for cathode plate penetrations 7. Further, the smoke plate 14 is provided. with holes 16 of different sizes, each adapted to control the flow of flue gas to achieve a uniform smoke rate and temperature distribution throughout the cabinet 2. It also ensures that the cathode plates 7 are evenly and uniformly coated by the flue gas, whereby electrically charged particles are deposited on the cathode plates. .

On the smoke plate 14 in the housing 2, distributor plates 17 are inserted between the cathode plates 7 for adjusting the flow of the flue gas through the housing 2 from inlet to outlet. A detailed drawing of a distributor plate 17 according to a homogeneous and size invention can be shown in FIG. 6, where a number of through holes 18 are shown. The holes 18 are arranged in a series, but the embodiment is not to be construed as limiting the invention, since the holes with their size and position are arranged to provide a smooth flow through the cabinet which provides heat distribution. The location of the holes is thus arbitrarily arranged by experiment or calculation in order to facilitate an even heat distribution in the cabinet and prevent the cathode plates from being skewed due to an uneven heat distribution. As noted in FIG. 7, which shows a cross section of a distributor plate 17, it is provided with a folded edge 19 on both sides. The width of the distributor plate 17 is so large that when mounted between the cathode plates 7, the edge forms a scraper 20 against the cathode plates 7 flanking the distributor plate 17 on both sides. The dimensioning of the distributor plate 17, including the width of the plate and the material thickness as well as the bending angle of the scraper portion, determines its resilient properties against the cathode plates 7. Hereby an appropriate spring force can be determined. A value of 5N / cm is appropriate.

A scraping of the cathode plates 7 is desired, which removes the particles attracted by the electric field but not so hard a scraping that the cathode plates 7 and scrapers 20 wear out too quickly. This is achieved partly by material selection where the cathode plates 7 are made of COR TEN A steel (fine-grained steel) and scrapers 20 formed on the distributor plate 17 are made of stainless steel, soft-grained steel of type 304.

FIG. 8 shows a microscopic image of a cross-section of the surface of a cathode plate 7. As can be seen, the plate has some roughness similar to a hill or mountain DK 179332 B1 landscape 21. As the unevenness is greater than the particle size of the particles sought to pack, the particles rapidly cathode plate 7 with electrically insulating dust which impedes the further operation of the electro filter 1. FIG. 9 shows a microscopic image where the cathode plate 7 has attracted a layer of particles 22. Due to peaks, scraping cannot remove all particles 22 and restore the full original function of the electrofilter. However, it has been found that the pressure exerted by the scraper 20 against the thin particle layer of approx. 100 microns makes the layer more electrically conductive so that the cathode plate 7 can again attract new particles 22.

While this seems satisfactory and is inexpensive to manufacture, it is desirable that the cathode plate 7 be as smooth as possible so that the cracks, elevations and recesses 21 in the surface are smaller than the particle size of the particles 22 attracted to the cathode plate 7. If a cathode plate 7 is selected from a stainless steel material, this can be polished, possibly. electropolished to completely smooth the surface as illustrated in FIG. 10. It is also possible to smooth the cathode plate by applying an electrically conductive layer, a coating. It can be a ceramic coating with conductive nanoparticles. Since the particles 22 in the flue gas attracted by the cathode plate in the electric field are larger than the particle size of the cathode plate coating, they will not be able to bond so hard to the cathode plate 7 and thus be easier to remove, possibly. with a brush.

As part of the invention, as shown in FIG. 11, a cross section of a cathode plate 7 is shown, showing its edge 23. As can be seen, the edge is 23 round as attempts have shown that many estimates start from the edge and that the round shape has been found to better counteract estimates. Tests also show that accumulation of dust particles on the edge can lead to several estimates. Therefore, according to the invention there is devised a scraper 24 arranged in the housing 2 in such a way that it wipes or scrapes the edge 23 of the cathode plate 7 and keeps it clean. As can be seen, the scraper 24 is provided with a recess 25 which is round which engages the edge rounding 23 and therefore the cathode plate 7 when rotated is kept clean.

Claims (3)

claims: 1.4 An electrofilter comprising: - a cabinet with: - an inlet for the supply of flue gas; - an outlet for the discharge of purified flue gas; a suspension arranged between inlet and outlet adapted to carry a pivotal shaft on which shaft is arranged a plurality of parallel electrically conductive plates adapted to act as cathodes; - a motor for rotating the pivot shaft; an arrangement for retaining a plurality of conductive wires which act as anodes and for arranging these wires so as to pass through the region between the cathode plates; - a power supply with connection to anode and cathode, characterized in that the electro filter comprises a device for regulating, distributing and dividing the flow of the flue gas from inlet to outlet. 2. I I Requirement no .: because a meaningful inquiry cannot be done, namely: 2.4 3.4 4.4 PATENT AND PRODUCT STARCHEY NEWS INVESTIGATION REPORT - PATENT application number PA 2016 00429 1. 1 1 Non-searchable requirements (see Box # I). 2. 1 1 Inventory unit is missing before the environmental survey (see Box No. II ·!). A. CLASSIFICATION B03C 3/36 (2006.01); B 03 C 3/08 (2006.01); B 03 C 3/10 (2006.01); B 03 C 3/47 (2006.01); B 03 C 3/74 (2006.01) According to International Patent Classification (IPC) B. SURVEY AREA PCT minimum documentation examined (classification system followed by classification symbols) IPC / CPC: B03C Examined documentation beyond PCT minimum Electronic databases used (database name and search terms, if any) EPODOC, WPI, FULL TEXT: ENGLISH C. RELEVANT DOCUMENTS Category* Documents cited stating relevant sections Relevant to requirement no. X US 5084077 A (JUNKER ERWIN et al.) 1992.01.28 1-3,5,8 Summary Column 4, line 39 - column 5, line 7 Column 6, lines 30-31 Figures 1, 7 X EP 1892044 Al (ZESU GIKO CO LTD et al.) 2008.02.27 1-3,5,8 Sections [0030] - [0035] Figure 1 M Additional documents are listed in Continuation of Box C. * Category of quoted documents: P Document published in the period between priority and A Document representing the prior art (state of the art) filing date. without anticipating news or significant separation. T Document that does not conflict with the application, but which is D Document cited in the application. quoted to understand the basic principle or theory behind E Document that has a submission or priority date that lies ahead the filing date of the processed application but that is X Particularly relevant document; the invention has no novelty or ad- published later than the filing date. does not differ significantly from prior art when evaluating the document L Document that may cast doubt on an alleged priority claim, or which is cited to determine the publication date of another Y Particularly relevant document; the invention does not differ significantly document, or cited for other reasons (as specified). from prior art when the document is combined with one or more O Document dealing with non-written disclosure, e.g. documents of the same kind, and the combination of these is blatant to the phased man. suits, exhibitions or movies. Document in the same patent family. Patent and Trademark Office Date of completion of the news survey Helgeshøj Allé 81 2630 Taastrun February 13, 2017 The news survey is done by Phone No. +45 4350 8000 Fax No. +45 4350 8001 Peter Philip Hoick Phone No. +45 4350 8558 Search report NEWS INVESTIGATION REPORT - PATENT application number PA 2016 00429 C (Continued). RELEVANT DOCUMENTS Category* Cited documents stating relevant sections Relevant to requirement no. X EP 1721678 A1 (ZESU GIKO CO LTD et al.) 2006.11.15 Sections [0030], [0031] Figure 1 1-3,5,8 X DE 4326757 Al (HANDLED SIEGFRIED DIPL ING) 1994.02.17 Claims 1, 2 Figure 1 1.8 A CN 203972139U U (ZHEJIANG SUNY ARD ENVIRONMENTAL PROT ENGINEERING CO LTD) 2014.12.03 The detailed description section in the machine translation Figures 1, 2 3.5 A US 2001039877 Al (HEIN ARTHUR G) 2001.11.15 Sections [0023], [0024] Figure 1 Search report NEWS INVESTIGATION REPORT - PATENT application number PA 2016 00429 Box # I Non-searchable claims The news survey has not been conducted for the following requirements:! □ Requirement no .: because the content of the claim (s) is not considered to be an invention: Electrofilter according to claim 1, characterized in that the device comprises at least one screen arranged in the inlet for supply of flue gas for regulating, distributing and dividing the flow of the flue gas from inlet to outlet. Electrofilter according to claim 1, characterized in that the device comprises at least one plate having a plurality of flue gas inlets, arranged in a position between inlet and outlet so that the flow of flue gas as it passes through the holes is evenly distributed between the cathode plates. . Electrofilter according to claim 1, characterized in that the device comprises at least one plate having a plurality of flue gas passage holes arranged in a position between the cathode plates such that the flow of flue gas through passage through the holes is regulated and distributed evenly between the cathode plates. Electrofilter according to claim 3 or 4, characterized in that the plate is arranged in the cabinet in a vertical direction relative to the flow of the flue gas from inlet to outlet through the electro filter and that the size and position of the holes are arranged for an even distribution of the flue gas between cathode the plates. Electrofilter according to one of claims 3 to 5, characterized in that the device in the form of the plate for regulating flue gas flow is maintained relative to the housing but is in movable contact with at least one cathode plate arranged on the rotatable shaft and is adapted to to act as a scraper upon contact with the cathode plate wherein the device is provided with a curved edge where the edge acts as a scraper and wherein the scraper is formed of a flexible material having a thickness of between 0.5 and 2.0 mm containing the soft grain stainless steel steel and that the device is arranged resiliently suspended in contact with the cathode plate with a force of between 2 and 10 N / cm, preferred value 5 N / cm. Electrofilter according to claim 6, characterized in that the scraper is arranged in the side of the housing facing the inlet and / or that the scraper is arranged in contact with the lower semicircle of the cathode plate. Electrofilter according to one of claims 1 to 7, characterized in that the cathode plate is made of an electrically conductive material. Electrofilter according to claim 8, characterized in that the cathode plate is made of fine-grained alloy steel having a thickness of between 4 and 10 mm and having a diameter of between 300 and 3000 mm, the preferred thickness being 6 mm with a diameter of 1500 mm. Electrofilter according to claim 8, characterized in that the cathode plate is made of stainless steel which is electropolished. Electrofilter according to one of claims 8 to 10, characterized in that the cathode plate is coated with an electrically conductive metallic and / or ceramic coating of nanoparticles. Electro filter according to one of claims 1 to 11, characterized in that the cathode plate has a rounded edge and the electro filter further comprises a scraper arranged 5 in the cabinet in a position where it is in contact with the cathode plate edge and where the scraper is specially adapted to keep the cathode plate edge free of particles. 3. □ Requirement no .: of other lands: Box No. II Inventive device missing before the news survey Several inventions have been found in the application: Search report NEWS INVESTIGATION REPORT - PATENT application number PA 2016 00429 SUPPLEMENTARY BOX Continuation of Box No. [.] Search report