Patent Application
20240269693
This application claims the benefit of priority to European Patent Application No. 23156075.6, filed on Feb. 10, 2023. The disclosure of the above-referenced application is hereby expressly incorporated by reference in its entirety.
The present invention relates to a system comprising a discharge electrode assembly, the system being for use in an electrostatic precipitator unit as well as such an electrostatic precipitator unit. In particular, it relates to such a system being designed to ensure that the different parts of the discharge electrode assembly remain aligned and in the correct mutual positions and orientations.
An electrostatic precipitator (ESP) unit can be used for reducing the number of fine and ultrafine particles in an aerosol or a flow of flue gas from e.g. a wood-burning stove or a pellet boiler. In an ESP, an electric field is generated by a discharge electrode connected to a high voltage generator. The electric field causes the aerosol or flue gas around the discharge electrode to become ionized. Hereby either free electrons or charged gas molecules become trapped on the particles and thereby charge the particles. The charged particles are repulsed from the discharge electrode towards a grounded collection electrode on which they settle and build up and from where they can subsequently be removed in a controlled manner. Hereby the amount of pollution can be significantly lowered.
In order to ensure a correct and efficient functioning of an ESP, it is important that the discharge electrode is arranged centrally in the flow passage along its full length, the flow passage forming part of a flue gas passageway. The discharge electrode and the parts of the electrostatic precipitator unit with which it is mechanically connected comprise several mutually connected components, and it can therefore be difficult to ensure a correct arrangement of the discharge electrode. Each point of assembly presents a risk of errors with respect to both translation and rotation. Therefore, both the initial installation and re-assembly after regular cleaning of the discharge electrode and the flow passage provide challenges for the person performing the job.
Hence, an improved discharge electrode assembly would be advantageous.
It is an object of the present invention to provide a system comprising a discharge electrode assembly which system is easier to assemble and arrange correctly in relation to a flow passage than what is known from prior art.
It is another object of the present invention to provide a system comprising a discharge electrode assembly, the system having a lower risk of misalignment of the discharge electrode with respect to the flow passage in which it is arranged than what is known from prior art.
It is an object of at least some embodiments of the present invention to provide a system comprising a discharge electrode assembly which facilitates cleaning of the discharge electrode itself as well as the flow passage in which it is arranged than what is known from prior art.
It is a further object of the present invention to provide an alternative to the prior art.
In particular, it may be seen as an object of the present invention to provide a discharge electrode assembly that solves the above-mentioned problems of the prior art.
The above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a system for an electrostatic precipitator unit, the electrostatic precipitator unit being for insertion in a flue gas passageway, such as a chimney, the system comprising:
In order for the system to function as intended, the system is designed and installed so that the insulator has a longitudinal axis fixedly arranged parallel to a central axis of the pipe forming the flow passage. This can e.g. be obtained by mounting the isolator to a plate forming part of a casing of the system as will be shown in the figures.
The design of the different components of the system, and in particular of the discharge electrode assembly, and the way components are connected provide a number of advantages. The various locking surfaces and the engagement between them ensure that all the components are in the correct location and thereby that the discharge electrode assembly works as intended. The system comprising the discharge electrode assembly is designed for use in an electrostatic precipitator unit for insertion in a flue gas passageway, such as a chimney, as will be described in further details below. The efficiency of such an electrostatic precipitator unit is dependent on the discharge electrode being arranged centrally in the flow passage and aligned therewith. Therefore, the discharge electrode assembly has been designed so that that it is easy and efficient to ensure such correct positioning in the flow passage which forms part of the flue gas passageway.
In presently preferred embodiments of the invention, the mutual engagement between the first and the third locking surfaces is releasable, and/or the mutual engagement between the second and the fourth locking surfaces is releasable. Hereby it is obtained that it is easy and efficient to ensure a correct positioning of the discharge electrode after a temporary removal of the discharge electrode for cleaning of the discharge electrode itself as well as the flow passage in which it is arranged during use.
In some embodiments of the invention, the first locking surface is a protrusion extending from the first end of the connector pin, and the third locking surface is a locking hole matching the shape and dimensions of the protrusion. The two parts are then preferably connected, e.g. by use of a matching screw, to ensure that they remain connected. Other means of connecting are also covered by the scope of protection. The first and third locking surfaces may e.g. be kept in place by a press fit, a pin or a clamp.
In some embodiments of the invention,
In such embodiments, the insulator connector may comprise the guiding hole, and the connector pin may be configured to slide along the guiding hole in the insulator connector to allow for movement of the discharge electrode relative to the insulator. Hereby it is possible and easy to move the discharge electrode sideways away from the normal central position in a flow passage in a guided manner. This movement will be relevant for regular cleaning of the discharge electrode and/or the flow passage. An example of such an embodiment will be shown in the figures.
The discharge electrode may comprise a first discharge electrode part and a second discharge electrode part, which first and second discharge electrode parts are aligned and releasably and fixedly connected to each other during use of the discharge electrode. Hereby a higher freedom is obtained with respect to the shape of the discharge electrode than if it had been made as a unitary element. An example of such a presently preferred design will be shown in the figures. Such a design allows for an efficient establishment of the third locking surface and the associated engagement with the first locking surface; this will be seen from the figures. Furthermore, it is an efficient way of increasing the stiffness and thereby a lowering the risk of damage and misalignment of the discharge electrode. The first and second discharge electrode parts may e.g. be assembled by rivets, screws, or bolts.
In a second aspect, the invention relates to an electrostatic precipitator unit for insertion in a flue gas passageway, such as a chimney, the electrostatic precipitator unit comprising:
As mentioned above, this is the intended use for which the system according to the first aspect of the invention has been developed. Therefore, some of the advantages of embodiments of the system, and in particular the discharge electrode assembly thereof, are most clearly understood in combination with the second aspect of the invention. The above-given comments on the different embodiments therefore also applies to an electrostatic precipitator unit according to the second aspect.
In some embodiments of the invention, the electrostatic precipitator unit further comprises a casing extending laterally from the pipe, the casing comprising:
When it is desired to provide an existing chimney with an electrostatic precipitator unit according to the present invention, a part of the chimney is removed and replaced by the electrostatic precipitator unit.
The feature that the casing extends laterally from the pipe comprises embodiments wherein the casing surrounds the pipe and embodiments wherein the casing is joined with the pipe so that they form one element. An example of a design of the casing will be shown in the figures. The casing will typically be made from stainless steel, but other materials which can withstand the high temperatures can also be used.
The heat shield plate is used to reduce the thermal radiation from the pipe heated by the hot flue gas flowing therein. Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. It is generated when heat from the movement of the material is converted to electromagnetic radiation. The heat shield plate reflects and possibly also absorbs some of the thermal radiation so that only a reduced amount of heat is transmitted into the second compartment.
In the second compartment, a large part of the heat is removed by convection, and therefore, the present invention is based on the combined protective effect of the heat shield plate and the convection area in the second compartment.
Convection can be defined as the transfer of heat form one place to another due to the movement of fluid. When natural buoyancy forces alone are responsible for fluid motion when the fluid is heated, the process is typically called “natural convection”. An example of this is the draft in a chimney such as in relation to the present invention. The arrangement of the at least one lower hole and the at least one upper hole at the lower and upper regions, respectively, of the second compartment, results in the main direction of the flow of air in the second compartment being vertically upwards. This flow of air means that hot air in the second compartment is removed by natural convection, and this results in a cooling whereby it can be ensured that the controller and the high voltage generator are not subjected to too high temperatures.
When the electrostatic precipitator unit is arranged in a chimney of a pellet burner, the temperature of the flue gas is typically in the order of up to 250 degrees Celsius. Tests have shown that by use of the present invention, it is possible to keep the temperature at the location of the controller and the high voltage generator below 50 degrees Celsius.
The casing may be provided with more holes than those mentioned above. It may e.g. be provided with holes in the part of the walls forming the first compartment in order to obtain additional cooling thereof. The at least one lower hole and the at least one upper hole are preferably arranged with as large vertical distance from each other as possible for a given size of the casing in order to provide venting of most of the second compartment. Typically there will be a plurality of lower holes and a plurality of upper holes; an example of such an embodiment will be shown in the figures.
In embodiments of the invention comprising a heat shield plate as just described, the heat shield plate may be bent or curved so that a horizontal distance between the heat shield plate and both the controller and the high voltage generator is larger adjacent to the walls of the casing than midway between the walls of the casing. Hereby it is ensured that there is as much space as possible for the flow of air along the second compartment so that an efficient cooling is ensured.
In presently preferred embodiments of the invention, both the at least one lower hole and the at least one upper hole are provided in two opposing walls of the casing. Hereby a widespread flow of air is obtained whereby it can be ensured that substantially all of the second compartment is efficiently cooled by the natural convection.
The insulator may be arranged in a fourth compartment of the casing, the fourth compartment being above and at least partly separated from the second or third compartment in which the controller and the high voltage generator are arranged. The insulator is connected to the discharge electrode via an opening in the pipe, and hot flue gas and ash may exit the pipe via the same opening. Therefore, by arranging the insulator in such a fourth compartment, it can be obtained that this flue gas and ash do not reach and possibly cause damage to the controller and the high voltage generator.
The controller and the high voltage generator may be arranged in a control box forming a unitary enclosure. Such a control box can provide protection against heat, moisture, and dirt. Furthermore, it can facilitate the installation and possible subsequent maintenance, because the control box can be handled as a separate unit.
A shortest horizontal distance between the pipe and the heat shield plate may be at least 10 mm, such as at least 13 mm, such as at least 15 mm. A shortest horizontal distance between the heat shield plate and both the controller and the high voltage generator may be at least 15 mm, such as at least 18 mm, such as at least 20 mm. These two measures have been found suitable at least for an electrostatic precipitator unit designed for use in a chimney with a flue pipe having a diameter of around 150 mm. However, similar distances may also be used for larger or smaller units.
An electrostatic precipitator unit according to the second aspect of the invention may further comprise a brush stop configured to be arranged at the flue gas outlet and extending across the flow passage, the brush stop being configured to prevent a sweeping brush from passing the brush stop when the unit is inserted in the flue gas passageway. In order to facilitate cleaning of the part of the flue gas passageway below the brush stop, it will typically be detachably arranged. It may be fully removable, or it may be hingely connected.
The first and second aspects of the present invention may be combined. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
The system and the electrostatic precipitator unit according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.
The insulator 7 is arranged between the discharge electrode 5 (negative polarity) and the location where the insulator 13 is mounted on the casing of the ESP (grounded—positive polarity). The insulator 7 prevents a shortcut between the two poles (i.e. the discharge electrode and the collection electrode). As shown
In the embodiment illustrated in
Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23156075.6 | Feb 2023 | EP | regional |
