FROM AMBIENT AIR

The present invention relates to a device for capturing condensation nuclei, particularly pathogens and/or virulent particles, and preferably also fine dust particles, from ambient air. The invention also relates to a method for capturing condensation nuclei, pathogens and/or virulent particles and preferably also fine dust particles from ambient air, in particular by making use of a device according to the invention.

Fine dust consists of floating particles, generally particles smaller than 10 micrometres, in the ambient air which pose a danger to health. Fine dust particles can already cause symptoms here in relatively low concentrations. The smaller the particles, the deeper they can penetrate into the respiratory tract. The damage to health manifests itself in, among others, premature death, an increase in emergency hospitalizations for heart and respiratory conditions, respiratory disorders and functional disorders. Large dust particles are less harmful because they do not generally pass through the upper respiratory tract. Traffic (40%), industry (23%) and agriculture (20%) are the main sources of fine dust. Fine dust is created as a result of combustion processes in for instance cars (particularly diesel engines), electric power stations, industrial and private burner devices. It can however also be a result of the storage and transfer of for instance coal, ore and grain and of wear to car tyres and roads. Diverse devices are known for at least partially purifying the ambient air of the above stated particles. A known, efficient manner here is ionizing ambient air by means of high voltage and corona discharge, whereby an electric wind (ionic wind) can be generated between an ionizing positive electrode and a nearby negative electrode, and a part of the fine dust can be removed from the ambient air using the negative electrode. In addition to the above stated fine dust particles, the ambient air however also entrains pathogenic particles (biological pathogens) and virulent particles (non-biological pathogens), including viruses, bacteria, fungi and other types of spore. These pathogens and virulent particles are generally also microscopically small and cannot be detected with the naked eye. Pathogens and virulent particles entrained by the ambient air are breathed in directly and generally cause the immune system to be in a constant state of alert, with serious consequences for health. Particularly when the ratio of pathogenic and virulent particles to body cells is high, as is the case with children, which is confirmed by recent reporting from the World Health Organization. Virulent particles are for instance Virulent Anthropogenic Nuclei or Kerns, as described in chapter 3.2 of the book The Forgotten Pollution, ISBN 0792339177 Kluwer Academic Press 1996, written by Rein A. Roos. Since the fine dust particles and the pathogenic and/or virulent particles function in practice as

condensation nucleus in that water will condense onto such aerosols in moist cold air, which results in the formation of clouds, fog or mist, such particles are collectively referred to as condensation nuclei in the context of this patent publication.

An object of the invention is to provide an improved device and method for capturing condensation nuclei, in particular pathogens and/or virulent particles, and preferably also fine dust, from ambient air.

The invention provides for this purpose a device for capturing condensation nuclei, in particular pathogens and/or virulent particles, from ambient air comprising: at least one high voltage source and at least one primary positive electrode connected to the high voltage source and configured to ionize ambient air by means of corona discharge, at least one preferably substantially plate-like negative electrode which is positioned at a distance from the primary positive electrode such that an electric wind forms between the primary positive electrode and the negative electrode during use of the device, wherein the device comprises, downstream relative to the primary positive electrode and preferably at least partially upstream relative to the negative electrode, at least one preferably substantially plate-like secondary positive electrode configured to bind negatively charged condensation nuclei, in particular pathogens and/or virulent particles, from the ambient air. Research has shown that condensation nuclei such as pathogens and virulent particles are generally negatively charged, whereby these particles are repelled by the likewise negatively charged earth and in fact accumulate in the ambient air. These negative pathogenic and virulent particles are captured in the device according to the invention by applying one or more generally substantiate platelike secondary positive electrodes, to which the negatively charged pathogens and/or virulent particles can adhere. At least one secondary positive electrode is not directly connected to the high voltage source, whereby the potential of the secondary electrode(s) is generally lower, significantly lower, than the potential of the primary positive electrode(s). This at least one secondary positive electrode not connected to the high voltage source is configured to be positively charged through interaction with the positively charged particles from the electric wind, whereby negatively charged condensation nuclei, in particular pathogens and/or virulent particles, from the ambient air are bound by the at least one secondary positive electrode. At least one secondary positive electrode not connected to the high voltage source will generally be completely neutral initially and only be charged by positive particles which collide with this secondary electrode, whereby it is positively charged. This at least one secondary positive electrode is therefore also referred to as passive electrode, while the other electrodes which are connected to the high voltage source, including the at least one primary positive electrode and the at least one negative electrode, are deemed active electrodes. As stated, the at least one secondary positive (low-voltage) electrode plays a particularly important part in capturing negatively charged condensation nuclei, in particular pathogens and/or virulent particles, from the ambient air. By giving the at least one secondary positive electrode a substantially plate-like form and preferably the form of a substantially closed plate, more preferably a substantially flat closed plate, the capturing contact surface of the at least one secondary positive electrode can be configured such that sufficient, and even substantially all, negatively charged condensation nuclei which are guided through the device according to the invention can be captured and thereby removed from the ambient air. The primary positive electrode is particularly configured to create in an electric field, as a result of a corona discharge being generated, a charged particle cloud which is attracted by the negative electrode, which results in the electric wind. During the corona discharge ultraviolet radiation will moreover be emitted at the primary positive electrode which has a sterilizing effect on the pathogens and virulent particles present in the ambient air. In the device according to the invention the pathogens and virulent particles are thus rendered harmless by sterilization on the one hand and capture by means of the secondary positive electrode on the other. The negative electrode has the functionality of being able to create the electric wind and of binding positively charged particles from the ambient air. These positively charged particles can be positively charged naturally or be (further) positively charged by means of the primary positive electrode. Fine dust in particular will be captured by means of the negative electrode. The device therefore comprises at least one ionizing positive high- voltage electrode, at least one positive electrode for capturing negative particles, in particular pathogenic and/or virulent particles, and at least one negative electrode for capturing positive particles, in particular fine dust. Since the invention is not and need not be provided with temperature-increasing means, nor with filters which result in pressure loss, the device can operate in a relatively energy- efficient manner. The device can otherwise be applied as electrostatic precipitator both inside, such as for instance in hospitals and schools, and outside. A plate-like electrode is understood to mean an electrode which has a relatively large (plate-like) capturing surface. This capturing surface can be flat and/or curved, and can also take a closed and/or partially open form. The geometry of the plate-like electrode as such need not be limited to an actual two-dimensional plate-like geometry, but can also have a more three-dimensional geometry. The electrodes are manufactured at least partially from one or more electrically conductive materials, preferably metal. Space for generating electric wind formed between at least a part of the at least one primary positive electrode and at least a part of the at least one negative electrode will generally be free of intermediate components such as filters (filter cloths), dielectric layers or other (resistance- increasing) components. Owing to this free intermediate space, wherein the primary positive electrode and the negative electrode lie in each other's line of sight, the electric wind can be generated substantially unobstructed and displace substantially

unobstructed from the primary positive electrode to the negative electrode, which significantly enhances the efficiency of the device. It is for this reason also strongly recommended to position at least one secondary positive electrode, and more preferably all secondary positive electrodes, out of the centre of the electric wind, i.e. eccentrically. In the case a plurality of secondary positive electrodes are applied, at least two secondary positive electrodes preferably enclose the centre of the electric wind. The above stated secondary positive electrodes are here preferably positioned laterally on two sides (opposite sides) relative to the centre of the electric wind (to be generated). Each secondary positive electrode will generally intercept and possibly guide a fraction of the electric wind here, although as stated the heart of the electric wind will preferably be left free of (resistance-increasing) objects. The device is preferably configured to allow the electric wind to displace only under the influence of at least one electric field formed between the at least one primary positive electrode and the at least one negative electrode. This is understood to mean that no means are used for generating an airflow mechanically or in alternative manner, such as for instance a fan. Having the device function wholly and solely on the basis of generation of an electric wind makes it possible for the device to be given a structurally relatively simple, inexpensive and durable form, which is particularly advantageous. The use of a fan moreover generally results in an undesirably high wind speed, whereby more turbulence is created in the generated wind flow, and harder collisions with diverse electrodes, which can often have a particularly adverse effect on the efficiency of particle capture. The use of means for mechanical generation of an airflow is also undesirable for this reason.

At least one negative electrode is preferably embodied as a (substantially) completely closed plate. A closed plate has the advantage that the negative electrode is

impermeable to the electric wind, whereby particles entrained by the electric wind are forced to collide with the negative electrode, this considerably increasing the efficiency of the device in capturing (fine dust) particles. The electric wind will here usually collide frontally with a (closed) frontal surface of the negative electrode, after which the wind is forced to flow substantially parallel to the frontal surface of the negative electrode, or at least an (imaginary) plane defined by the frontal surface of the negative electrode, whereby the contact time of the electric wind with the particle-capturing negative electrode is increased, which further increases the efficiency of the negative electrode. The at least one negative electrode is preferably embodied here as a substantially completely closed, substantially flat plate. A flat plate is generally sufficiently effective and has the significant advantage that it is relatively easy to clean (compared to a folded, angled or otherwise profiled plate).

A further advantage of the device according to the invention is that odour-determining particles (condensation nuclei) can and generally will also be captured by the device during the capture of condensation nuclei from the ambient air, whereby the odour of the ambient air can be influenced, and particularly neutralized, by applying the device. The odour-determining condensation nuclei are usually formed by relatively long and/or complex organic molecules which are usually decomposed in effective manner by the typical 50-75 keV present in the corona gas discharge in the vicinity of the primary positive electrodes. The efficiency of this odour-neutralizing process increases greatly owing to the moving and preferably circulating airflow, whereby the whole in fact takes on the form of an effective reactor vessel (neutralization vessel). The at least one secondary positive electrode is preferably configured to be positively charged through interaction with the positively charged particles from the electric wind. The secondary positive electrodes need not therefore be connected here to a separate voltage source, and the secondary positive electrode takes on a passive character in that the secondary positive electrode is charged by positive particles from the ionized ambient air which come into contact with the secondary positive electrode during use. This passive secondary positive electrode will generally be connected in electrically insulated manner to the negative electrode and will preferably also be connected in electrically insulated manner to the primary positive electrode.

The secondary positive electrode is preferably positioned relative to the negative electrode such that a (secondary) electric field will form between the secondary positive electrode and the negative electrode during use. This allows the size of the overall electric field to be increased and/or the electric field to be given a more directed form, whereby the capture capacity of the device can be increased.

The ionization of the ambient air at and around the primary positive electrode is a direct consequence of the corona discharge generated using the high voltage source. Created by the high voltage source is an exceptionally strong electric field which is so strong that the breakdown field strength of air (3 MV/m for dry air) is reached. Above this field strength a discharge will take place in the air around the primary positive electrode, which is also referred to as corona discharge, whereby a non-thermally positively charged plasma ('positive corona') is created. These desired discharges occur mainly in the case of irregular, pointed and/or narrow surfaces. It is therefore advantageous for the primary positive electrode to comprise at least one electrically conductive wire, at least one electrically conductive pin or tip or other type of strip, or a combination thereof (wire provided with pins). The positive ions created in the corona follow the electric field lines of the emitting electrode (primary positive electrode) to a collector plate of the negative electrode. Radicals formed during the corona discharge, particularly oxygen radicals, are charge-neutral and are entrained by the electric wind. Owing to the high degree of reactivity these radicals will generally react rapidly with the condensation nuclei, such as pathogenic or virulent particles and/or fine dust, of the electric wind. The particles are oxidized here in the case the radical forms an oxygen radical, which results particularly in the case of pathogenic particles in inactivity, thereby rendering them harmless. Small (fine dust) particles (< 1 μιη) can absorb tens of ions before the overall charge is sufficient to repel other ions, large (fine dust) particles (> 10 μπι) can thus absorb tens of thousands. The electrostatic forces are thereby much stronger on large particles. The charged particles are driven to the collector plate of the negative electrode by the charge. The turbulence in the charged gas tends to mix the particles uniformly with the gas. The collection process is therefore a balance between electrostatic forces and dispersive forces. The positively charged particles finally approach the collector plate of the negative particles closely enough to the position where the turbulence is greatly decreased, whereby the particles are collected.

The high voltage source (electric modulator) is configured to generate a potential difference of at least 10 kV, preferably at least 20 kV and more preferably about 30 kV between the primary positive electrode and the negative electrode. The high voltage source preferably forms a direct current source. The electric current will generally be particularly low and be in the order of magnitude of microamperes, whereby the overall power of the high voltage source will remain limited to a safe order of magnitude of milliwatts.

The negative electrode is referred to as negative because this electrode will have a lower potential than the primary and secondary positive electrode(s). The term 'negative' must therefore be deemed relative in this context. It is possible to envisage the absolute potential of the negative electrode being charge-neutral, for instance by the negative electrode being given an earthed form. It is however also possible to envisage the high voltage source also being connected to the negative electrode for the purpose of charging the negative electrode with a (relatively) negative potential.

In order to improve the capture capacity of the device for negatively charged condensation nuclei, in particular pathogens and virulent particles, it is advantageous for the at least one secondary positive electrode to be positioned downstream relative to the primary positive electrode and upstream relative to the negative electrode such that the at least one secondary positive electrode is configured to guide the electric wind from the primary positive electrode to the negative electrode. Arranging the secondary positive electrode in the wind flow as guide (wind screen) guarantees intensive contact with the (turbulent) electric wind, which generally facilitates the ability to capture the condensation nuclei, in particular the pathogenic and virulent particles.

It is possible to envisage, and generally even advantageous, that the device comprises a plurality of secondary positive electrodes, whereby the capturing power (capture capacity) of the device can be further improved. It is particularly advantageous here for the secondary positive electrodes to be positioned downstream relative to the primary positive electrode and upstream relative to the negative electrode such that the secondary positive electrodes are configured to multilaterally bound and guide the electric wind flowing from the primary positive electrode to the negative electrode during use of the device.

A side of the primary positive electrode remote from the negative electrode is preferably uncovered (unprotected), whereby substantially unobstructed suction of ambient air can take place, this enhancing the creation of the desired (continuous) electric wind.

The primary positive electrode and at least a part of the negative electrode preferably extend substantially parallel. Owing to this parallel orientation an electric field with a relatively homogenous electric field strength can be created, and thereby a relatively constant electric wind speed between the positive and negative electrodes. This generally increases the controllability of the device. It is nevertheless also possible to envisage allowing the electric field strength to vary between the positive and negative electrodes, whereby more turbulence can be (deliberately) created.

The present invention also relates to a method for capturing condensation nuclei, in particular pathogens and/or virulent particles, from ambient air, particularly by making use of a device according to any of the foregoing claims, comprising the steps of: A) applying an electric field between a primary positive electrode and a negative electrode using a high voltage source such that ambient air present around the primary positive electrode is at least partially ionized and an electric wind will be created from the primary positive electrode to the negative electrode, B) positively charging at least one secondary positive electrode positioned downstream relative to the primary positive electrode by means of positively charged ions forming part of the electric wind, and C) having the charged secondary positive electrode bind negatively charged condensation nuclei, in particular pathogens and/or virulent particles, entrained by the electric wind.

The electric wind also entrains fine dust particles in the air. Large fine dust particles (with a typical diameter of 1 micrometre) will build up a relatively high speed in the electric wind and collide relatively rapidly with the negative electrode, whereby they can (also) be captured from the airflow. Small fine dust particles will hardly be influenced by the generated wind, but are susceptible to Brownian movement and are captured from the air by diffusion and interception with the negative electrode. Fine dust particles which are more difficult to capture from the air are medium-sized particles, which are relatively insusceptible to both forms of capture (collision and diffusion). Medium-sized fine dust particles (with a typical diameter of between 0.02 and 1.0 micrometre) generally have a high ratio of surface area to volume. As a result these particles are positively charged by the electric wind, with the additional consequence that the medium- sized particles repel each other and move toward the edge of the electric wind, where they can be as far apart as possible from each other and the mutual repelling forces are smallest. It will generally be precisely these medium- sized positively charged particles which collide with the at least one secondary positive electrode and provide for effective positive charging of this electrode.

Different preferred embodiments of the invention are enumerated in the clauses below. 1. Device for capturing condensation nuclei, in particular pathogens and/or virulent particles, from ambient air, comprising:

at least one high voltage source,

at least one primary positive electrode connected to the high voltage source and configured to ionize ambient air,

- at least one substantially plate-like negative electrode which is positioned at a distance from the primary positive electrode such that an electric wind forms between the primary positive electrode and the negative electrode during use of the device, wherein the device comprises, downstream relative to the primary positive electrode and preferably at least partially upstream relative to the negative electrode, at least one substantially plate-like secondary positive electrode configured to bind negatively charged condensation nuclei, in particular pathogens and/or virulent particles, from the ambient air.

2. Device according to clause 1, wherein the at least one secondary positive electrode is configured to be positively charged through interaction with the positively charged particles from the electric wind.

3. Device according to clause 1 or 2, wherein the secondary positive electrode is connected in electrically insulated manner to the negative electrode. 4. Device according to any of the foregoing clauses, wherein the secondary positive electrode is positioned relative to the negative electrode such that during use an electric field will form between the secondary positive electrode and the negative electrode.

5. Device according to any of the foregoing clauses, wherein the primary positive electrode is configured to generate at least one point discharge. 6. Device according to any of the foregoing clauses, wherein the primary positive electrode comprises at least one electrically conductive wire.

7. Device according to any of the foregoing clauses, wherein the primary positive electrode comprises at least one electrically conductive pin.

8. Device according to any of the foregoing clauses, wherein the high voltage source is configured to generate a potential difference of at least 10 kV, preferably at least 20 kV and more preferably about 30 kV between the primary positive electrode and the negative electrode.

9. Device according to any of the foregoing clauses, wherein the high voltage source forms a direct current source.

10. Device according to any of the foregoing clauses, wherein the high voltage source is also connected to the negative electrode for the purpose of charging the negative electrode with a negative potential.

1 1. Device according to any of the foregoing clauses, wherein the negative electrode is earthed.

12. Device according to any of the foregoing clauses, wherein the at least one secondary positive electrode is positioned downstream relative to the primary positive electrode and upstream relative to the negative electrode such that the at least one secondary positive electrode is configured to guide the electric wind from the primary positive electrode to the negative electrode.

13. Device according to any of the foregoing clauses, wherein the device comprises a plurality of secondary positive electrodes.

14. Device according to clause 13, wherein the secondary positive electrodes are positioned downstream relative to the primary positive electrode and upstream relative to the negative electrode such that the secondary positive electrodes are configured to multilaterally bound and guide the electric wind flowing from the primary positive electrode to the negative electrode during use of the device.

15. Device according to any of the foregoing clauses, wherein the primary positive electrode and at least a part of the negative electrode extend substantially parallel.

16. Method for capturing condensation nuclei, in particular pathogens and/or virulent particles, from ambient air, particularly by making use of a device according to any of the foregoing clauses, comprising the steps of:

A) applying an electric field between a primary positive electrode and a negative electrode using a high voltage source such that ambient air present around the primary positive electrode is at least partially ionized and an electric wind will be created from the primary positive electrode to the negative electrode,

B) positively charging at least one secondary positive electrode positioned downstream relative to the primary positive electrode by means of positively charged ions forming part of the electric wind, and

C) having the charged secondary positive electrode bind negatively charged condensation nuclei, in particular pathogens and/or virulent particles, entrained by the electric wind. The invention will be elucidated on the basis of non-limitative exemplary embodiments shown in the following figures. Herein:

Figure 1 shows schematically the capture of large and small fine dust particles in a device according to the present invention; Figure 2 shows schematically the capture of medium-sized fine dust particles in a device according to the present invention; and

Figure 3 shows schematically a post provided with a device according to the present invention.

Figure 1 shows schematically the capture of large and small fine dust particles in a device according to the present invention. Figure 1 shows for this purpose a pointed electrode (1) connected to a positive side of a high voltage (2) and a flat metal plate (3) connected to a negative side of the high voltage (2). An electric wind (A) is generated by ionizing of particles in the air. Large dust particles (4) are entrained (B) by this wind (A) and collide with the flat metal plate (3), where they are captured. Owing to their small mass, small fine dust particles (5) are relatively insusceptible to the electric wind (A). The small particles (5) are however susceptible to Brownian movement (C) and through diffusion come into contact of their own accord with the metal plate (3), where the small fine dust particles (5) are also captured.

Figure 2 shows schematically the capture of medium-sized fine dust particles in a device according to the present invention. Figure 2 shows for this purpose a pointed electrode (1) connected to a positive side of a high voltage (2) and a flat metal plate (3) connected to a negative side of the high voltage (2). An electric wind (A) is generated by ionizing of particles in the air. The medium-sized particles (6) are slightly positively charged by the electric wind (A), after which the particles (6) and the pointed electrode (1), likewise positively charged, repel each other.

These slightly positively charged medium-sized fine dust particles (6) are captured by an (initially neutral) additional plate (7), shown on the left-hand side of figure 2. This additional plate (7) is slowly positively charged and will then no longer capture the positively charged medium-sized particles (6), but repel them. Medium- sized particles (6) which are repelled by the additional plate (7) then enter an electric field (D) which extends between the positive additional plate (7) and the negative metal plate (3), where the positive medium-sized particles (6) will be forced in the direction of the negative plate (3) and there captured. The positively charged plate (7) also attracts substantially negatively charged pathogenic and virulent particles from the air.

Figure 3 shows schematically a post (10) provided with a device for capturing particles according to the present invention, comprising three first electrodes (11), three second electrodes (12), a generator (13) for charging the first electrodes (11), so forming an electric field between the electrodes (11, 12) and six electrically rechargeable panels (14). It will be apparent that the invention is not limited to the exemplary embodiments shown and described here, but that within the scope of the appended claims numerous variants are possible which will be self-evident to the skilled person in this field. It is possible here to envisage that different inventive concepts and/or technical measures of the above described embodiment variants can be wholly or partially combined without departing from the inventive concept described in the appended claims.

The verb "comprise" and conjugations thereof used in this patent publication are understood to mean not only "comprise", but are also understood to mean the phrases "contain", "substantially consist of, "formed by" and conjugations thereof.