WO2021107850A1

WO2021107850A1 - Particle eliminator

Info

Publication number: WO2021107850A1
Application number: PCT/SE2020/051133
Authority: WO
Inventors: Johnny GENTZEL
Original assignee: Gentzel Johnny
Priority date: 2019-11-27
Filing date: 2020-11-26
Publication date: 2021-06-03
Also published as: SE543755C2; CN114728293A; SE1951357A1

Abstract

A particle elimination system (1) comprises an ion emitting unit (10), and a collection unit (50). The ion emitting unit is configured for emission of negatively charged ions into a gas volume (2) having particles therein. Thereby, the negatively charged ions, when encountering the particles, charge the particles to form negatively charged particles (4). The collection unit is aimed for collection of the negatively charged particles. The ion emitting unit comprises a multitude of sharp ion-emission points (30) and a high-voltage source (40) connected to the multitude of sharp ion-emission points. The collection unit comprises a collection structure of metal, electrically connected to a zero or positive voltage. Each of the sharp ion-emission points is isolated from each other and, as the only electrical connection, is connected to the high-voltage source by a respective feed connection.

Description

PARTICLE ELIMINATOR

TECHNICAL FIELD

The present technology relates in general to particle elimination arrangements and in particular to such arrangements based on emission of ions.

BACKGROUND

Air quality inside buildings has often been discussed during many years. A high concentration of particles and/or viruses/ bacteria in the indoor environment may cause many problems. There is thus a need to clean the indoor air in many places. This is particularly important e.g. in hospitals or in indoor environments where many people pass.

One prior-art approach is to use so-called air cleaners based on ionization. An ionizer emits a stream of negative ions into the air volume to be cleaned. The number of ions may be extremely high. These negative ions will reach particles in the air and thereby charge these particles. The particles may range from a few nanometres up to visible sizes. The charged particles are typically agglomerated into larger particles and will eventually settle down at a surface, preferably a positively charged surface.

Many of the prior-art air cleaners have different kinds of problems. Particles may settle on the ionizer tips causing short-circuiting of the high voltage provided to the ionizer tips. Positively charged surfaces positioned in the vicinity of the ionizer may disturb the spreading of the negative ions in the room and/or give an inefficient collection of charged particles. The need for more stable and efficient arrangements is large.

The British patent specification GB 418,403 provides a system for the electrical precipitation of suspended particles from gases, comprising a source of high voltage current, collecting electrodes defining a plurality of parallel gas passages, and discharge electrodes opposed to the collecting electrodes and connected in parallel to the source of high voltage current so as all to receive the same potential, surge resisting means in each of the parallel supply connections between the source of high voltage current and the discharge electrodes and surge resisting means in the return connection between the source and the collecting electrodes.

In the published International Patent Application WO 2018/205719 Al, a negative ion generating device is disclosed. The negative ion generating device includes a high voltage power source, a negative ion guiding end and a plurality of negative ion emitting ends respectively connected to the plurality of negative ion emitting ends and the negative ion guiding end. The negative ion generating device further includes a current control device, wherein each of the negative ion emitting ends is connected to the high voltage power source through the current control device.

In the published US Patent Application US 2007/0091536 Al, an ion generating unit and an ion generating apparatus are disclosed. An ion generating component includes, on an insulating substrate, a ground electrode, a high-voltage electrode, an insulating film on the surface of the ground electrode, and a linear electrode. The ground electrode is disposed at the outer region of the insulating substrate and includes a pair of legs, which are substantially parallel to the linear electrode, which is disposed between the legs. The ground electrode further includes a contact portion in contact with a terminal and an insulating casing contact portion in contact with the upper resin casing. The insulating film is disposed on substantially the entire surface of the insulating substrate so that the high-voltage electrode, the contact portion, and the insulating casing contact portion of the ground electrode remain uncovered.

In the published US Patent Application US 2013/0047858 Al, an electrostatic precipitator cell is disclosed. The electrostatic precipitator contains a collection assembly, a plurality of collection assembly ground plates disposed in the collection assembly, a plurality of banks disposed in the collection assembly, wherein each bank containing a collection assembly charge plate and a voltage isolator is described. Electrically isolating portions of an electrostatic precipitator cell results in reduced arcing and overall increases in cleaning efficiency. As air cleaner utilizing the electrostatic precipitator with isolated banks is also described.

SUMMARY

A general object of the present technology is to provide a stable and efficient arrangement for particle elimination in a room.

The above object is achieved by methods and devices according to the independent claims. Preferred embodiments are defined in dependent claims.

In general words, a particle elimination system comprises an ion emitting unit, and a collection unit. The ion emitting unit is configured for emission of negatively charged ions into a gas volume having particles therein. Thereby, the negatively charged ions, when encountering the particles, charge the particles to form negatively charged particles. The collection unit is aimed for collection of the negatively charged particles. The ion emitting unit comprises a multitude of sharp ion-emission points and a high-voltage source connected to the multitude of sharp ion-emission points. The collection unit comprises a collection structure of metal, electrically connected to a zero or positive voltage. Each of the sharp ion-emission points is isolated from each other and, as the only electrical connection, is connected to the high-voltage source by a respective feed connection. The gas volume is comprised in a room of a building, and that a distance between the ion emitting unit and the collection unit is larger than 2 m and / or larger than half the distance between two walls of said room facing each other. One advantage with the proposed technology is that a stable and efficient elimination of particles is enabled. Other advantages will be appreciated when reading the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:

FIG. 1 schematically illustrates a prior art ion emitting unit;

FIG. 2 schematically illustrates an embodiment of an ion emitting unit having separate high-voltage connections;

FIG. 3 schematically illustrates an embodiment of a particle elimination system arranged in a room; and

FIGS. 4A-B schematically illustrates two view of an embodiment of a collection unit.

DETAILED DESCRIPTION

Throughout the drawings, the same reference numbers are used for similar or corresponding elements.

For a better understanding of the proposed technology, it may be useful to begin with a brief overview of a corona discharge. An electrode provided with an electrical potential will create an electrical field in the surroundings, typically in air. When the potential gradient, i.e. the electrical field is large enough, the air may ionize. If a charged object has a sharp point, the electric field strength around that point will be enhanced. Corona discharge in atmospheric pressure air typically occurs at 30 kilovolts per centimeter. At very sharp points, corona discharge can start at potentials of 2 - 6 kV. In most corona discharge ionizers, negative potentials are used, thus producing negative ions escaping from the sharp points. In many prior art ionizers 100, the sharp points 110 are provided attached to a common base 111, as schematically illustrated in Figure 1. The common base 111 is connected by a common connection 112 to the high voltage supply 113. The sharp points 110 are typically provided in holes 114 in a casing 115.

During operation, particles may settle down on the sharp points 110, potentially causing a contact between the casing 115 and the sharp points. This may e.g. be the case if positively charged particles are present in the vicinity of the ionizer and the sharp points are provided with a negative voltage. Such short-circuiting of one sharp point 110 will influence the operation of all sharp points 110 and the arrangement is thereby sensitive for such contamination particles.

Figure 2 schematically illustrates an embodiment of an ion emitting unit 10. The ion emitting unit 10 is configured for emission of negatively charged ions 5 (illustrated by the arrows 5) into a gas volume 2 having particles 3 therein. The negatively charged ions 5, when encountering the particles 3, charge the particles to form negatively charged particles 4.

The ion emitting unit 10 comprises a multitude of sharp ion-emission points 30 and a high-voltage source 40 connected to the multitude of sharp ion- emission points 30. Each of the sharp ion-emission points 30 is isolated from each other and, as the only electrical connection, being connected to said high- voltage 40 source by a respective feed connection 42A-42J. Preferably, each of said feed connections 42A-J has an individual electrical resistance 44A-J of at least 1 MO from the high voltage potential. The high-voltage source 40 is furthermore connected to ground 48 by a ground connection 46.

This configuration will result in that even if one of the sharp emission points 30 will be short-circuited, only that specific sharp emission point 30 will be severely affected. The remaining sharp emission points 30 will essentially remain undisturbed and will continue to deliver a stream of ions as requested. Cleaning of the ion emitting unit 10 can thereby wait for some time without harming the efficiency considerably. The cleaning can instead be scheduled to times when such activities are more appropriate and may even be scheduled in advance in a regular manner, regardless of any existing short-circuiting. In case of one defect or clogged sharp emission point, 90% of the unit performance is still available.

The ion emitting unit 10 has in this embodiment a casing 20 with holes 22. Each of the sharp ion-emission points 30 is positioned in or just inside a respective one of the holes 22. In other words, a casing outer plane, illustrated by the dotted line 29, is situated outside, with reference to the interior of the casing 20, a tip plane, illustrated by the dotted line 39, comprising the tips of the sharp ion-emission points 30.

Conducting casings are not to recommend due to the high risk of short- circuiting with the sharp ion-emission points 30, either by physical to the casing or sharp ion-emission points 30 or by contaminating particles. It is therefore preferred if at least the part of the casing 20 presenting the holes 22 has a low electrical conductivity. Preferably, the casing 20 has an electrical conductivity of less than 10^-4 S/m, and even more preferably less than 10^-8 S/m.

However, highly electrically isolating materials also have the tendency to charge up, presenting a static surface charge. Such static charge can distort a local electrical field just in front of the casing, which may alter the electrical field in which the ions are supposed to move. Therefore, in one embodiment, the casing has an electrical conductivity of more than 10^-12 S/m. In a particular embodiment, the casing is made of wood. Wood, especially with surface treatment to avoid humidity, is known to be electrically isolating, but will not build up any static surface charge.

As mentioned above, by using a very sharp ion-emission point 30, ions can efficiently be produced already around a potential of 2 kV. An even more efficient ion production is achieved if the voltage is increased, e.g. above 2.4 kV.

In other words, in one embodiment, the high-voltage source provides a voltage to the feed connections of at least 2.4 kV.

When a corona discharge takes place, the molecules in the gas in the vicinity of the sharp ion-emission points 30 achieve an extra electron and becomes a negatively charged ion. If this corona discharge takes place in air, the two main components present are nitrogen gas and oxygen gas. If oxygen gas becomes a negatively charged oxygen ion, such an ion may pick up an additional oxygen atom from another oxygen gas molecule, forming ozone. Ozone is a gas having a high oxidizing effect. This oxidizing effect is sometimes utilized for sanitizing or deodorizing actions. However, since the same oxidizing effect also causes damages to the respiratory organs in humans, high concentrations of ozone has to be avoided in rooms where humans are intended to be present.

The amount of production of ozone is dependent on the strength of the applied electrical field. The corona discharge first appearing at relatively low voltages, such as 2 kV mainly affects the nitrogen gas in the air. The production of ozone, however, occurs at higher applied voltages. Ozon is not created with lower voltages than 3kV when the surrounding material is isolated and cannot create arcs or plasma creeping.

In order to avoid ozone production, the voltage has been found to be kept below 3 kV. In other words, in one embodiment, the high-voltage source provides a voltage to the feed connections of at most 3 kV.

Figure 3 illustrates schematically an embodiment of a particle elimination system 1. The, particle elimination system 1 is installed in a room 6, enclosing a gas volume 2. In other words, in one embodiment, the gas volume 2 is comprised in a room 6 of a building. The particle elimination system 1 comprises an ion emitting unit 10, configured as described above. The particle elimination system 1 also comprises a collection unit 50 for collection of the negatively charged particles 4. The collection unit comprises a collection structure of metal, electrically connected to a zero or positive voltage. This will be described more in detail below.

The sharp ion-emission points 30 of the ion emitting unit 10, having a negative potential, and the positive-potential collection unit 50 creates an electrical field within the room 6. This is schematically illustrated by field lines 7. The negatively charged particles 4 are influenced by the electrical field and is drawn towards the collection unit 50. The collection of the negatively charged particles 4 is most efficient if the electrical field is a stationary and stable field. In order to assure that this electrical field is created and is reasonably stable, it is therefore preferred if the electrical systems of the ion emitting unit 10 and the collection unit 50 are interconnected. In other words, in one embodiment, the high-voltage source 40 of the ion emitting unit 10 and the collection unit 50 are connected to a same ground potential.

In order to achieve an efficient removal of particles within the gas volume 2, The stream of negatively charged ions from the ion emitting unit 10 is preferably spread over an as large volume as possible. Such a spreading is facilitated if the collection unit 50 is positioned relatively far from the emitting unit 10.

In the embodiment illustrated in Figure 3, the ion emitting unit 10 and the collection unit 50 are situated at opposite walls 9 of the room 6. In such a way, most of the gas volume will be penetrated by the electrical field and an efficient particle removal is expected.

However, in some applications, such arrangements may be difficult to achieve. However, it is still advantageous to separate the ion emitting unit 10 and the collection unit 50. In some simple tests, it has been shown that a distance between these two components preferably should exceed 2m, in particular in larger rooms.

Another measure that can be used for finding advantageous distances is to use a relative distance measure. If a room has a smallest distance between opposite walls, it has been found that an advantageous operation of the arrangement is achieved if the separation between the ion emitting unit 10 and the collection unit 50 is at least half this smallest distance. Even if the ion emitting unit 10 and the collection unit 50 in such a configuration do not enclose the entire gas volume in the room 6, regular convection within the gas volume 2 will typically be sufficient to achieve particle removal of the entire space.

In other words, in one embodiment, a distance between the ion emitting unit 10 and said collection unit 50 is at least larger than 2 m and/or larger than half the distance between two walls 9, facing each other, of the room 6.

In the illustration, the ion emitting unit 10 and said collection unit 50 are both provided at the walls 9 of the room 6. However, other mounting places may also be utilized, i.e. one or both of the components may be placed on a floor or in a ceiling.

The separation of the ion emitting unit 10 and said collection unit 50 and the preference to have a same ground potential may cause the need for providing of long cables between these two positions. In many applications, however, already existing power grids provided to the room can be utilized. This is schematically illustrated in Figure 3 by the electrical sockets 60 and the power grid connection 62. In other words, in one embodiment the same ground potential is zero potential or ground potential of an electrical power grid installed in connection to the gas volume 2.

Figures 4A and 4B illustrate schematically one embodiment of a collection unit 50 of a particle elimination system. Figure 4A is a side cross-sectional view and Figure 4B is a front view. The collection unit 50 comprises a collection structure 53 of metal, electrically connected to a zero or positive voltage via a cable 51 and connection piece 52. In this particular embodiment, the collection structure 53 comprises a mesh 54 of thin metal plates. The mesh 54 presents large open areas in the front direction, thus allowing air to pass through the mesh 54. In this embodiment, the collection unit 50 further comprises a fan 55 configured for sucking gas from the gas volume 2 in front of the collection unit 50 through the mesh 54.

The main collection of particles by the mesh 54 is caused by the electrostatic attraction of the neutral or positive-potential mesh with the negatively charged particles. The fan 55 is believed to be responsible only for a minor part of the direction of particles.

When the particles meet the mesh 54, they typically settle down at the front surface of the mesh 54. This means that during operation, particles are gathering on the collection structure 53, and the collection structure 53 therefore has to be cleaned regularly.

In areas where bacteria or viruses are present, such hazardous particles are also charged and collected by the collection structure 53. The front of the collection structure 53 thereby achieves large amounts of infection particles. In one embodiment, particularly advantageous for avoiding spreading of viruses and bacteria, the collection unit 50 is further equipped with a UV light source 70. In such an embodiment, the UV light source 70 is mounted in such a way that the beam 71 of UV light covers the entire front area of the collection structure 53. Preferably, a screen 72 is provided, which prohibits any UV light to escape from the UV light source 70 in any other directions, that may reach any human beings. The irradiation by UV light 71 is intended to destroy the bacteria and viruses collected at the collection structure 53.

The operation of the UV light source 70 can be configured in different ways. One alternative is to have a continuous illumination of UV light. In such applications, in particular if the system is installed in areas where human beings are present, the design of the screen 72 is important for avoiding any accidental UV radiation to the human beings. In another approach, the operation of the UV light source 70 could be intermittent, i.e. the collection structure 53 is only irradiated during some time periods. In such cases, such irradiation periods may be synchronized with time periods when there is a small risk of human beings being present in the vicinity. This could e.g. be used in an office or a waiting room, which is intended to be empty during nights, when the UV radiation can take place.

In other words, in one embodiment, the collection unit 50 further comprises a UV light source 70, configured for continuously or intermittently illuminating the collection structure 53. The embodiments described above are to be understood as a few illustrative examples of the present invention. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the scope of the present invention. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible. The scope of the present invention is, however, defined by the appended claims.

Claims

1. A particle elimination system (1), comprising:

- an ion emitting unit (10), configured for emission of negatively charged ions (5) into a gas volume (2) having particles (3) therein, whereby said negatively charged ions (5), when encountering said particles (3), charge said particles (3) to form negatively charged particles (4); and a collection unit (50) for collection of said negatively charged particles

(4) ; said ion emitting unit (10) comprising a multitude of sharp ion- emission points (30) and a high-voltage source (40) connected to said multitude of sharp ion-emission points (30); said collection unit (50) comprising a collection structure (53) of metal, electrically connected to a zero or positive voltage; each of said sharp ion-emission points (30) is isolated from each other and, as the only electrical connection, being connected to said high-voltage source (40) by a respective feed connection (42A-J), characterized in that said gas volume (2) is comprised in a room (6) of a building, and that a distance between said ion emitting unit (10) and said collection unit (50) is at least one of: larger than 2 m; and larger than half the distance between two walls of said room (6) facing each other.

2. The particle elimination system according to claim 1, characterized in that each of said feed connections (42A-J) has an individual electrical resistance (44A-J) of at least 1 MO from the high voltage potential.

3. The particle elimination system according to claim 1 or 2, characterized in that said high-voltage source (40) provides a voltage to said feed connections (42 A- J) of at least 2.4 kV.

4. The particle elimination system according to any of the claims 1 to 3, characterized in that said high-voltage source (40) and said collection unit (50) are connected to a same ground potential.

5. The particle elimination system according to claim 4, characterized in that said same ground potential is zero potential or ground potential of an electrical power grid installed in connection to said gas volume (2).

6. The particle elimination system according to any of the claims 1-5, characterized in that said collection structure (53) comprises a mesh (54); and said collection unit (50) further comprises a fan (55) configured for sucking gas from said gas volume (2) through said mesh (54).

7. The particle elimination system according to any of the claims 1-6, characterized in that said collection unit (50) further comprises a UV light source (70), configured for continuously or intermittently illuminating said collection structure (53) to destroy hazardous content of the collected particles.

8. The particle elimination system according to any of the claims 1-7, characterized in that ion emitting unit (10) has a casing (20) with holes (22); whereby each of said sharp ion-emission points (30) is positioned in or just inside a respective one of said holes (22); and whereby said casing (20) has an electrical conductivity of less than 10^-4 S/m, preferably less than 10^-8 S/m.

9. The particle elimination system according to claim 8, characterized in that said casing (20) has an electrical conductivity of more than 10^-12 S/m.