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Title:
AN APPARATUS FOR REMOVING PARTICLES FROM THE AIR AND ELIMINATING SMOG AND A METHOD FOR USING IT
Document Type and Number:
WIPO Patent Application WO/2017/179984
Kind Code:
A1
Abstract:
An apparatus is provided for cleaning air polluted by solid particles. The apparatus comprises an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as an ionizer for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel. The apparatus comprises a filter located at a position between the ionizer and the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air and that have to be removed therefrom and wherein the flow area of the apparatus close to the ionizer is smaller than the flow area of the apparatus close to the filter at its upstream side.

Inventors:
VAN DER BURG, Simon (Middelzand 4439, 1788 JG Den Helder, 1788 JG, NL)
VAN WEES, Peter Willem (Ambonplein 64, 1094 RA Amsterdam, 1094 RA, NL)
Application Number:
NL2017/050236
Publication Date:
October 19, 2017
Filing Date:
April 14, 2017
Export Citation:
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Assignee:
VAN WEES OIL B.V. (Ambonplein 64, 1094 RA Amsterdam, 1094 RA, NL)
VAN DER BURG, Simon (Middelzand 4439, 1788 JG Den Helder, 1788 JG, NL)
International Classes:
B03C3/155; B01D53/32
Domestic Patent References:
WO2007085430A12007-08-02
Foreign References:
US20030079982A12003-05-01
US20100175389A12010-07-15
US6152988A2000-11-28
US20020134237A12002-09-26
Attorney, Agent or Firm:
AALBERS, Arnt Reinier et al. (Overschiestraat 180, 1062 XK Amsterdam, 1062 XK, NL)
Download PDF:
Claims:
CLAIMS

1. An apparatus for cleaning air polluted by solid

particles, comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as one or more ionizers for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel,

wherein the apparatus comprises a filter located at a position between the ionizers and the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air and that have to be removed therefrom and

wherein the flow area of the apparatus close to and/or at the ionizer (s) is smaller than the flow area of the apparatus close to and/or at the filter at its upstream side and

wherein the apparatus is configured to provide a low effective degree of ionization of the particles present in the air flow. 2. An apparatus according to claim 1, wherein for providing ionization to a low effective degree of ionization of the particles present in the air flow, the apparatus is adapted for, in particular the one or more ionizers being adapted for, ionizing only a part of the particles present in the airflow, in particular less than about 30% thereof, for example between 20%- 25% thereof,

and/or wherein the apparatus, in particular the ionizer is adapted for or, if applicable, the ionizers are adapted for, ionizing a part of the particles present in the air flow with mutually opposite polarities such that

the number of ionized particles of the one polarity and/or the total charge transferred to the particles of the one polarity forms an excess of more than about 20% of the particles of the other polarity and/or, respectively, of the total charge transferred to the particles of the other polarity, e.g. an excess of about 25% to 30% of that, and wherein in particular the one or more ionizers may have an operational ionizing range which is adapted such that only a part, in particular between about 20% and 40%, for example between about 25%-30%, of the flow area at the ionizer (s) is achieved operational for ionizing the particles.

3. An apparatus according to one of the preceding claims, wherein the apparatus comprises a driver, for example a fan, which is located in the airflow channel for transporting air to be cleaned through the apparatus,

wherein the fan is located upstream of the filter and/or downstream of at least a part of the one or more ionizers.

4. An apparatus according to one of the preceding claims, wherein the filter is a first filter and the apparatus comprises a second filter for filtering from the air at least a part of the solid particles that are present in the air, which second filter is located at a position between the first filter and the discharge opening and wherein the second filter particularly has a pore size which is larger than the pore size of the first filter .

5. An apparatus according to one of the preceding claims, wherein the filter, and/or, if present, the second filter comprises a carbon material, in particular active carbon, wherein preferably at least the filter comprises at least a layer of carbon material which is surrounded by the filter material and/or wherein the carbon material may be provided as a layer between layers of filter material.

6. An apparatus according to one of the preceding claims, wherein the filter is substantially made of a non-woven or woven material, and/or wherein filter comprises at least two layers of filter material which are mounted with respect to each other such that the air to be cleaned successively flows through the layers of filter material under operating conditions of the apparatus, and/or wherein the filter material is of F9 quality or a finer filter quality, and/or wherein the filter is shaped as a fabric filter or a bag filter, such that the airflow close to or at the filter is substantially grazing incident on the filter material, wherein for example the filter material is substantially oriented at an angle being smaller than 30 degrees with respect to the direction of the airflow close to and/or at the filter, preferably an angle being smaller than 15 degrees and more preferably an angle being smaller than 10 degrees, for example an angle between about 3 and 10 degrees.

7. An apparatus according to one of the preceding claims, wherein the filter and/or the second filter, if present, is electrically conductive and is grounded or electrically charged.

8. An apparatus according to one of the preceding claims, wherein close to the discharge opening the apparatus is provided with one or more air guides causing an increasing flow area of the apparatus between the filter and the discharge opening and/or between the second filter, if present, and the discharge opening .

9. An apparatus according to one of the preceding claims, wherein the airflow channel between the ionizer and the filter is provided with a widening and a restriction, such that the airflow channel in the direction of airflow successively

provides an increase and a reduction of the flow area and wherein the flow area of the apparatus at or close to the filter at the airflow upstream side thereof is larger than the flow area downstream of the restriction.

10. An apparatus according to one of the preceding claims, comprising a baffle located in the airflow channel,

wherein the baffle may be provided with a filter material, particularly a fabric filter which may be displaceable over the baffle plate and wherein a drive means may be provided for that displacement, and

wherein the baffle may be oriented in the airflow channel at a non-perpendicular angle with respect to the direction of airflow, particularly at a small angle and/or

wherein the position and/or angle of the baffle with the direction of airflow in the airflow channel is reversibly adjustable wherein a drive means may be provided for the adjustment .

11. An apparatus according to claim 10, wherein the baffle may be provided as a liquid support and/or a liquid guide and the apparatus can be provided with a liquid supply and/or a liquid drain and wherein the baffle may be profiled and/or may be provided with one or more projecting parts such as ribs, studs and/or a mesh, possibly adapted for supporting a filter material on the profile parts and/or projecting parts such that gaps for liquid are made between the baffle plate and the filter which can be such that contact between the filter and the liquid is avoided. 12. An apparatus according to one of the claims 10-11, comprising a number of baffle that are placed in the airflow channel, wherein a first baffle extends at a first angle with respect to the direction of airflow and a second baffle extends at a second angle with respect to the direction of airflow, such that at least a part of the airflow through the first baffle is directed onto the second baffle, and wherein at least a part of the airflow is directed by the second baffle around the first baffle plate. 13. An apparatus according to claim 9 and one of the claims

10-11, wherein the baffle is located in or close to the widening and the restriction in the airflow channel.

14. An apparatus according to one of the preceding claims, wherein at least the airflow channel is placed rotatably on a support .

15. A filter for an apparatus according to one of the preceding claims, comprising one or more layers of filter

material of F9 quality or a finer filter quality, wherein the filter material is provided with a carbon material, in

particular active carbon, wherein preferably the carbon material is provided as a layer between layers of the filter material, in particular as a layer of grains or powder between layers of the filter material, wherein the filter substantially can be a cloth material, for example made of a non-woven and/or woven material.

16. A filter according to claim 15, wherein the filter is shaped as a bag filter including an access opening wherein the walls of the bag or bags contain the one or more layers of filter material and the carbon material.

17. A method of cleaning air polluted by solid particles, comprising

transporting the air to be cleaned through an airflow channel of an apparatus via a supply opening of the airflow channel and discharging the air that is transported through the airflow channel via a discharge opening, and

guiding the air to be cleaned along an ionizer, which is placed in the airflow channel, for ionizing particles present in the airflow and for creating agglomeration of the ionized particles, wherein the flow area of the apparatus close to the ionizer is smaller than the flow area of the apparatus close to the filter at its upstream side, characterized in that the method comprises filtering with a filter which is located at a position between the ionizer and the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air, and removing agglomerated particles from the air with the filter, wherein the method comprises providing an ionization having a low effective degree of ionization of the particles that are present in the airflow by ionizing of only a part of the

particles that are present in the airflow, in particular less than about 30% thereof, e.g. 20%-25% thereof and/or by ionizing particles with mutually opposite polarities such that the number of ionized particles of the one polarity and/or the total charge transferred to the particles of the one polarity forms an excess of more than about 20% of the particles of the other polarity and/or, respectively, of the total charge transferred to the particles of the other polarity, e.g. an excess of about 25% to 30% of that.

18. A method according to claim 17, comprising the application of an apparatus according to one of the claims 1-15.

Description:
An apparatus for removing particles from the air and eliminating smog and a method for using it

The present invention relates to an apparatus for cleaning air polluted by solid particles, comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as an ionizer for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel. The invention also relates to a filter and to a method for using the apparatus for removing solid particle-shaped pollutants from the air.

Such an invention is known in the prior art. For example, the cleaning tower of Roosegaarde is known, with which particle-shaped pollutants are removed from the air by exposing the air to an ionizer.

However, such an apparatus does not work optimally.

Removal of particles is only limited because of the limited range of the conductors.

Therefore, there is a need of an improved apparatus for cleaning air by removing solid particles from it, in particular by means of an ionizer.

It is noted that WO 01/34854 discloses a method and a device for particle agglomeration, wherein fine particles of dust and other pollution in gas flows are agglomerated to form larger particles which are more easily filtered in downstream processing. In one embodiment, particles in successive portions of the gas stream are charged with opposite polarity, and the gas stream is introduced into an Evase portion (12) to slow it down. Particles of different sizes have differential

deceleration and therefore mix generally in the direction of flow, leading to agglomeration of oppositely-charged particles. In another embodiment, a gas stream is divided into substreams in respective parallel passages, and the particles in adjacent passages are charged to opposite polarity. Deflectors at the downstream end of the passages cause substreams of particles of opposite polarity to mix, with resultant agglomeration of oppositely charged particles. Fine particles of dust and other pollutants in gas streams entering a duct (10) are agglomerated to form larger particles which are more easily filtered in downstream processing. Particles in successive portions of the gas stream are charged by an AC ionizer (14) with opposite polarity, and the gas stream is introduced into an Evase portion (12) to slow it down. Particles of different sizes have

differential deceleration and therefore mix generally in the direction of flow, aided by vibrators (13), leading to

agglomeration of oppositely-charged particles.

Further ionization filters are known from EP 0 403 230 Al, US 2009/0084265 Al and US 2013/0255231.

An object of the invention is to provide an improved apparatus of the type as mentioned in the preamble.

Particularly, an object of the invention is to provide an apparatus of the type as mentioned in the preamble, which can provide an excellent removal of particles and wherein solid particles which are originally present in the airflow can be removed from substantially the entire airflow that is treated by the apparatus.

In order to obtain at least one of the advantages as mentioned hereinbefore a first embodiment of the invention provides an apparatus which contains the following features: apparatus for cleaning air polluted by solid particles,

comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as an ionizer for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel, wherein the apparatus comprises a filter located at a position between the ionizer and up to a side of the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles being present in the supplied air. This apparatus has the advantage that removal of solid particles can be 100% in a simple manner. Such a simple manner of cleaning of the air is an unexpected result.

It has also appeared that the filter including the collected particles therein, which is used in the apparatus according to the invention, can be re-used in a low-cost manner. For example, the filter can be used as insulation material in the construction industry. Such a synergetic functioning of the apparatus according to the invention is totally unexpected. The filter can be simply re-used by grinding the entire filter, together with the collected pollutants, and process it as a granulate in concrete. It can also be used as material for processing in foundation for roads. In this way the pollutants are effectively sealed and inactivated.

Therefore the invention is related to an apparatus for cleaning air polluted by solid particles, comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging airflow being transported through the airflow channel from the apparatus, as well as an ionizer for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel, wherein the apparatus is characterized in that it comprises a filter located at a position between the ionizer and up to the side of the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air.

Preferably, the filter is placed at the end of the airflow channel, but it can also be located at a position upstream thereof. That is advantageous especially when the filter could become wet in case of rain, snow or the like. A cover between the filter and the end of the apparatus could prevent the filter from wetting.

A wet filter will be able to provide an increased filter effect, on the one hand, but will be able to provide a higher resistance to the airflow, on the other hand, resulting in a strong increase of power required by the apparatus when using a fan to transport the air through the apparatus.

It is preferred that in the apparatus according to the invention the filter has a pore size which is larger than at least 80% of the solid particles that are present in the

supplied air. This leads to a substantially entire removal of the solid particles in practice, since the particles agglomerate due to ionization and consequently obtain a larger diameter than the separate particles. Therefore, they will be trapped in the filter. The larger pore size of the filter causes a significant lower resistance through the filter than in case of a filter having a smaller pore size. Such an advantageous combined effect is surprising.

A further reduction of the resistance is obtained when the flow area of the apparatus close to the ionizer is smaller than the flow area of the apparatus close to the filter. This results in a lower airflow velocity through the filter than the airflow velocity through the remainder of the apparatus, for example at the ionizer and the fan, which provides a high efficiency to the apparatus.

The flow area may vary by a factor between 5 and 10 per metre in the direction of the airflow, for example by a factor between 6-8 per metre, in particular about 7.5 per metre. For example, an increase of a circular duct having an inner diameter of 0.8 m, or a flow area of n(0.8/2) 2 = 0.503 m 2 , to a

rectangular inner shape of 1.22 m x 1.85 m = 2.257 m2, along a length of 0.6 m in the direction of the airflow, which means an increase of area of the flow area from about 7.5 times per metre flow length. Such a change can be obtained by placing walls of the airflow duct at an angle of 45-70 degrees, in particular about 60 degrees with respect to a longitudinal axis of (the airflow duct of) the apparatus.

An apparatus which can be built in a simple way is obtained when the airflow channel has a substantially

rectangular flow area along at least a part of its length. In that case the apparatus can be made simply of rectangular plate materials. This is particularly advantageous in case of

installing the filter, as well, since a rectangular filter generally has little or no material losses during manufacturing. The operating costs of the apparatus, in particular the filter costs, will be minimal in that case and can simply span the entire flow area.

The apparatus may be rotatable with respect to a fixed support and/or a chassis, in particular about a substantially vertical rotational axis. This makes it possible to vary the orientation of the apparatus with respect to the environment in a simple way, for example in order to adjust the apparatus with respect to a wind direction. The apparatus may be provided with a driving unit which can be operated remotely, wired and/or wireless. Furthermore, or instead thereof the apparatus can be rotatable passively, for example rotatable like a weather vane under the influence of the wind, in particular for that, the apparatus can be provided with one or more wings and/or

projecting control faces.

In order to make effective operation possible which is not dependent on the weather conditions, such as the wind, the apparatus comprises a fan which is located in the airflow channel for transporting air to be cleaned through the

apparatus. A fan may also boost a present natural airflow.

An effective transport of the air to be cleaned is specifically obtained if the airflow channel at the fan has a substantially circular flow area. As a consequence the fan, which will generally also have a circular diameter, can be effectively and efficiently placed in the airflow channel.

Therefore, the apparatus may comprise a widening close to the transfer of the airflow channel to the filter, which preferably contains a transfer from a circular cross-section to a

rectangular cross-section, as well.

The coagulated or agglomerated particles will have a charge because of the ionizer. In order to remove the

agglomerated particles effectively in the filter it is

advantageous when the filter is grounded. The filter can also be given a charge opposite with respect to the ionized particles, which may further improve trapping of the particles.

An effective removal is obtained specifically in case when the filter material is electrically conductive in order to obtain an optimal trapping of the charged particles.

Particularly, a preferable filter comprises a carbon-containing material, which has an excellent electrical conductivity and therefore traps the ionized and agglomerated particles very effectively and effectively.

An additional advantage of the apparatus according to the invention is that also ozone is removed from the air which flows through the apparatus. The system is not exactly clear, but probably the ionization causes ozone molecules to hit each other in an accelerated way and are converted into oxygen molecules. Another possibility of the functioning is based on the filter which causes due to the ionized particles and

grounding thereof the ozone molecules at the filter to be converted into oxygen molecules.

A surprising effect is further that the apparatus according to the invention is suitable to substantially

completely remove the so-called pmlO and pm2.5 particles

(particles having a size smaller than 10 and 2.5 micrometre, respectively) . The air is e.g. transported through the filter at a velocity of 4 to 8 m/s such that the cleaned air can partly return to the supply opening of the apparatus in order to be treated once again. The high effectiveness of removing very small solid particles from the air makes the apparatus according to the invention a real ' smog killer ' .

Efficiently trapping pollutants, in particular the agglomerated particles, is obtained when the filter comprises at least two layers of filter material which are enclosed in a housing such that the air to be cleaned successively flows through the layers of filter material. The filter material can be a non-woven material which is usually applied in air filter housings, like air conditioning systems, but, as mentioned hereinbefore, preferably comprising a carbon material as

additive. The carbon material may have a powder shape, for example 100 mesh size or smaller for 90% of the particles, and it can particularly be provided as active carbon. Appropriate filter material can have a thickness of 15 mm. Therefore, applying in a double layer results in a total thickness of 30 mm. A thicker layer causes better trapping of the (ionized) particles. However, a thinner layer thickness, even to a few mm, may be sufficient, as well.

The layers of filter material are preferably separated from each other through the housing, which housing is preferably made of a non-woven or woven material. The housing may be a surrounding of cotton or linen or something like that, such that the filter material is enclosed therein.

Furthermore, preferably the apparatus is provided with at least two ionizers in the airflow channel. This provides an even distribution of ionization to the air to be cleaned and transported through the apparatus . Especially, it is preferred that the ionizers in that case are substantially evenly distributed along the

circumference of the airflow channel. Possibly the ionizers can also be distributed in longitudinal direction of the apparatus (which is the direction in which the air through the apparatus is transported) . A combination in the longitudinal direction and along the circumference is also possible.

According to a further aspect the invention relates to a method of cleaning air polluted by solid particles, comprising transporting the air to be polluted through an airflow channel via a supply opening of the airflow channel and discharging the air that is transported through the airflow channel via a discharge opening, and guiding the air to be cleaned along an ionizer, which is placed in the airflow channel, for ionizing the airflow and particles in the airflow and for creating agglomeration of ionized solid particles. This method is

characterized in that the method comprises a filter, which is located at a position between the ionizer and up to the side of the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air, for removing agglomerated particles from the air with the filter.

According to a preferred embodiment the method according to the invention comprises the application of an apparatus according to the invention, for example as described specifically in one or more of the following numbered clauses:

1. An apparatus for cleaning air polluted by solid particles, comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as an ionizer for ionizing the airflow and particles in the airflow, characterized in that the apparatus comprises a filter located at a position between the ionizer and up to the side of the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air. 2. An apparatus according to clause 1, wherein the filter has a pore size which is larger than at least 80% of the solid particles that are present in the supplied air.

3. An apparatus according to clause 1, wherein the flow area of the apparatus close to the ionizer is smaller than the flow area of the apparatus close to the filter.

4. An apparatus according to clause 1, wherein the airflow channel has a substantially rectangular flow area along at least a part of its length.

5. An apparatus according to clause 1, wherein the apparatus comprises a fan which is located in the airflow channel for transporting air to be cleaned through the

apparatus .

6. An apparatus according to clause 1, wherein the airflow channel at the fan has a substantially circular flow area .

7. An apparatus according to clause 1, wherein the filter is grounded.

8. An apparatus according to clause 1, wherein the filter comprises a carbon-containing material.

9. An apparatus according to one of the preceding clauses, wherein the filter comprises at least two layers of filter material which are enclosed in a housing, such that the air to be cleaned successively flows through the layers of filter material.

10. An apparatus according to clause 9, wherein the layers of filter material are separated from each other by means of the housing, which housing is preferably made of a non-woven or a woven material.

11. An apparatus according to one of the preceding clauses, wherein at least two ionizers are provided in the airflow channel.

12. An apparatus according to clause 11, wherein the ionizers are provided substantially evenly along the

circumference of the airflow channel.

The advantages of the apparatus which are described hereinbefore, are obtained in a similar manner in the method.

In order to obtain at least one of the advantages as mentioned hereinbefore the invention according to an embodiment provides an apparatus which contains the following features: an apparatus for cleaning air polluted by solid particles,

comprising an airflow channel including a supply opening for supplying ambient air into the airflow channel and a discharge opening for discharging air transported through the airflow channel from the apparatus, as well as one or more ionizers for ionizing the airflow and particles in the airflow, which ionizer is located in the airflow channel, wherein the apparatus comprises a filter for removing at least a part of solid

particles in the supplied air, which filter is located at a position between the ionizer (s) and the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of the solid particles that are present in the supplied air and that are to be removed therefrom and wherein the flow area of the apparatus close to and/or at the ionizer (s) is smaller than the flow area of the apparatus close to and/or at the filter at its upstream side.

In the current disclosure the terms 'upstream' and 'downstream' are related to the airflow through the apparatus, particularly through its airflow channel.

By the airflow channel a controlled airflow is

provided. By the ionizer a part of the particles to be filtered are electrically charged such that they are stimulated to agglomerate. By the agglomerated particles are trapped and removed from the airflow. The relatively large pores decelerate clogging of the filter and lengthen useful operational life thereof. By the increase of the flow area of the apparatus causes the pressure of the airflow is reduced and turbulence is increased, which causes agglomeration of at least a part of the charged particles that are carried with the airflow. The

widening of the flow area and the resulting widening of the flow volume also facilitate the occurrence and/or continuation of velocity differences between the particles, which further stimulates agglomeration. By the apparatus agglomeration of small particles is promoted in an efficient manner such that the resulting agglomerated small particles can be trapped

effectively by a relatively coarse filter. The apparatus makes it possible to remove fine dust particles and smaller particles including ultra-fine dust particles effectively from the airflow .

In an embodiment the filter is a first filter and the apparatus comprises a second filter which is located at a position between the first filter and the discharge opening.

Thus, particles which pass through the first filter can still be trapped. The second filter may have a pore size which is larger than the pore size of the first filter, which means that the airflow after passing the first filter is not influenced heavily after the first filter.

In an embodiment the apparatus comprises a fan which is located in the airflow channel for transporting air to be cleaned through the apparatus. A thus forced airflow facilitates controlling the airflow and makes the airflow (at least almost completely) independent from external influences. The fan also allows to effectively accelerate particles of different sizes and/or different weights and furthermore turbulence can be provided in the airflow. The fan may be located upstream of the filter and/or downstream of at least a part of the one or more ionizers. A thus located fan or another blower causes

substantially a push flow instead of a suction flow, which may lead to increased turbulence and particle diffusion in the airflow channel relative to a suction flow, in particular downstream of objects in the airflow.

In an embodiment the airflow channel has a

substantially rectangular flow area along at least a part of its length. This makes it possible to manufacture and to operate the apparatus in a simple way by using rectangular materials, for example rectangular filter materials.

In an embodiment at least the airflow channel is placed rotatably on a support. This makes ( re ) orientation of the airflow channel possible.

In an embodiment the (first) filter and/or, if applicable, the second filter is grounded or electrically charged, respectively, for which it may be made electrically conductive. This facilitates agglomeration of particles,

particularly charged particles, and increases the chance of attracting and trapping charged particles. In an embodiment the first filter and/or, if present, the second filter comprises a carbon material, in particular active carbon. Carbon, in particular activated carbon, has a large physical filtering capacity by adsorption and/or

absorption and it can have a high chemical reaction capacity. Therefore, it is very suitable for the present application.

Furthermore, such carbon materials are easily electrically conductive which simplifies a combination with an ionizing step.

In an embodiment at least the (first) filter comprises at least a layer of carbon material which is surrounded by the filter material and/or wherein the carbon material is provided as a layer between layers of filter material. This protects (activated) carbon materials against external influences, including wear. It can also prevent pollution of the environment due to escaping carbon material.

In an embodiment the (first) filter comprises at least two layers of filter material which are mounted with respect to each other such, that the air to be cleaned successively flows through the layers of filter material under operating conditions of the apparatus. Suitable filter materials are cotton cloth and glass fibre cloth, but alternative materials are also possible. Thus, improved filter functioning can be achieved due to a higher chance of trapping particles which travel through the filter. Carbon material which may be present can be applied between the layers of filter material, such as described above. The carbon material may be provided as grain material or powder material with an average particle size of about 100 micrometre or smaller with a standard deviation of particle sizes of 5-15%, for example 10%, it may also be larger, for example 20%, but preferably in any case such that the carbon material remains in the filter material in case of normal use of the apparatus.

Preferably, the (first) filter is made of non-woven material and/or a woven material. This combines a large

effective area with advantageous properties for processing and use, for example pliability, transmissibility for air and mechanical strength, and generally low manufacturing costs.

The (first) filter may be made of a filter material of F9 quality (see standard EN779:2012, for example) . A finer filter quality, directed to better trapping of ultra-fine particles, may be used which could lead to accelerated clogging of the filter material. It is expected that an apparatus with a widening as generally described herein with an F9 filter or a finer filter that comprises a carbon material and/or is formed as an electrically conductive filter as described herein

elsewhere can on its own be useful for achieving a positive and useful filter result, e.g. also without ionization or with ionization to a high effective degree of ionization of the particles present in the airflow.

At least the (first) filter may be shaped as a bag filter, for example including a number of filter bags which are placed next to each other in a common holder, wherein the bags can substantially be circular or rectangular and closed at three circumferential sides such that a cavity being surrounded by the filter material is provided including a supply opening at one side which is, in use, directed in the direction of the arriving airflow, and wherein leakage along and between filter bags that are located next to each other is avoided, for example by connecting parts of filter bags which are located next to each other, such as by means of sewing, gluing, welding, clamping, etc. Bag filters combine a relatively large operational filter surface and a relatively small installation dimension (for example, expressed as surface extending transversely to an air supply flow) .

Preferably, the filter is formed and positioned such that the airflow close to or at the filter is grazing incident the filter material. The filter material may be substantially oriented at an angle being smaller than 30 degrees with respect to the direction of the airflow close to and/or at the filter, preferably an angle being smaller than 15 degrees and more preferably an angle being smaller than 10 degrees, for example an angle lying between about 3 and 10 degrees. Because of grazing incidence of the airflow the air can flow through the filter without or hardly any obstruction, but the particles will have a higher chance to touch the filter material due to their size, weight and/or inertia and consequently to be trapped. As a consequence, the filtering effectivity appears to rise to an unexpected extent, particularly for ultrafine dust. In such an embodiment, preferably more than 50% of the active filter surface, particularly more than 75% thereof, for example 80%-90% thereof, or even a higher part, is formed and positioned for such grazing incidence. Such an embodiment may be realised effectively if the filter is made as a conical filter and/or a bag filter, particularly a relatively narrow and deep bag filter relative to its opening and/or installation dimension (for example expressed as surface extending transverse to the air supply flow) .

In an embodiment the second filter comprises a support material and a carbon material, particularly active carbon which is applied as a layer on or in the support material, wherein 'in the layer' can be realized by a multilayer structure of the filter wherein the carbon material is provided as a layer between support layers. The support can be a mat of woven and/or non-woven material. A support in the form of a foam is also possible. The support and/or the layer of carbon material, for example active carbon, may be electrically conductive and/or chemically reactive.

In an embodiment at least two ionizers are provided in the airflow channel, wherein the ionizers can be provided substantially evenly along the circumference of the airflow channel. This enhances the functioning of the ionization. An even distribution advances a large and substantially homogeneous spatial distribution of ionization charge and charged particles.

The apparatus described herein may be arranged for providing ionization to a low effective degree of ionization of the particles present in the air flow.

In an embodiment the apparatus, in particular the ionizer or, if applicable, the ionizers is (are) adapted for ionizing only a part of the particles present in the airflow, in particular less than about 30% thereof, for example between 20%- 25% thereof.

Particularly, the ionizer has / the ionizers have an operational ionization range which is/are adapted such that only a part, particularly between 20 and 40%, for example between about 25%-30%, of the flow area at the ionizer / the ionizers is operably reached for ionizing the particles. Thus, only a part of the particles will be ionized. Also and/or alternatively, the apparatus, in particular the ionizer or, if applicable, the ionizers are, adapted for ionizing a part of the particles present in the air flow with mutually opposite polarities such that the number of ionized particles of the one polarity and/or the total charge

transferred to the particles of the one polarity forms an excess of more than about 20% of the particles of the other polarity and/or, respectively, of the total charge transferred to the particles of the other polarity, e.g. an excess of about 25% to 30% of that. Thus, the ionizer or, if applicable, the ionizers are, adapted to ionize a first part of the particles which are present in the airflow with a first polarity (positive or

negative) and a second part of the particles which are present in the airflow with an opposite polarity (negative or positive) and such that the number of particles of the first polarity and/or total charge of the first polarity transmitted to the particles is more than about 20% of the number and/or the charge of the second polarity, for example 25%-30% thereof. By

electrostatic interaction particles which are oppositely charged will adhere stronger to each other to neutral agglomerates, which can agglomerate further with the particles charged with the first polarity, which are present in excess, to agglomerates which are charged with the first polarity that can be filtered better, wherein little or no adverse influences of relatively high concentrations of similarly charged particles are present as described hereinbefore.

By providing a low effective degree of ionization, e.g. due to partial neutralization by agglomeration of oppositely charged particles and/or by providing only a partial ionization, the (further) agglomeration of particles is facilitated since mutual electrostatic repelling of particles with the same charge (positively or negatively) is reduced with respect to air in which a relatively large quantity of particles that are present are ionized, in particular being ionized with the same polarity. As a consequence the present apparatus may be operational by a combination of uncharged interaction (for example Van der Waals forces) and electrostatic interaction. Ionisation can also initiate and/or (make) sustain beneficial chemical processes. The result of a low effective ionization was unknown but turns out be very particularly effective for causing agglomeration and trapping ultrafine dust particles. An auxiliary benefit is that due a low effective degree of ionization, in particular

ionization of a small part of the particles, chances of forming of ozone are reduced. Ozone formation is further reduced by (operating ionizers for) positive ionization, relative to negative ionization.

In an embodiment one or more parts in the apparatus are provided for advancing turbulence in the airflow, which may promote coagulation of small particles to larger particles. For that, one or more ionizers may also be placed such that they project in the airflow.

In order to obtain sufficient ionization at a high airflow velocity an elongate ionizer may be provided and/or different ionizers may be placed behind each other in the airflow direction.

The rate of ionization may be determined by determining one or more operational parameters of one or more ionizers, for example a time and/or location dependent charge loss and/or current intensity of them. These one or more operational

parameters may be related to flow parameters of the air

transported through the airflow channel, for example a flow velocity, a humidity rate, a temperature, a particle quantity and the like. One or more flow parameters can be influenced by appropriately applied air treatment parts, in particular an air humidifier and/or the fan. A control unit may be provided in order to control operational parameters of one or more

ionizer (s) and one or more air treatment parts in adjustment to each other, possibly provided with a feedback system that can or cannot be automated.

In an embodiment the apparatus is provided with one or more air guides close to the discharge opening by which the flow area of the apparatus is enlarged between the filter and the discharge opening and/or, where appropriate, between the second filter and the discharge opening. As a consequence, an

additional pressure drop can be created downstream that filter which may improve flow through the filter. In an embodiment means are provided for creating and/or generating an additional airflow close to the supply opening and/or the discharge opening at and/or along the outer side of the apparatus, for example one or more fans, one or more

spoilers and the like, which may influence an airflow into or out of the airflow channel in a desired manner, for example generating suction or causing thrust.

In an embodiment the airflow channel between the ionizer and the filter is provided with a widening and a

restriction, such that the airflow channel in the direction of airflow successively provides an increase and a reduction of the flow area and wherein the flow area of the apparatus at or close to the filter at the airflow upstream side thereof is larger than the flow area downstream of the restriction. In this way additional regions of deceleration and acceleration,

respectively, or pressure increase and pressure decrease, respectively, are provided which may lead to enhanced relative velocity difference and interaction possibilities between the particles, and thus enhanced agglomeration of particles, prior to the widening of the flow area and the interaction region close to and/or at the filter, described elsewhere herein. The widening and a restriction may be in a range of 10% to 50% of the flow area adjacent the widening and/or the restriction

The apparatus may comprise a baffle in the airflow channel, wherein more than one baffle may be provided, as well. The baffle may be provided with a filter material, particularly a fabric filter which may be displaceable over the baffle and wherein drive means may be provided for that displacement. As a consequence of the displacement a part of the filter may be replaced and/or 'changed'. The baffle may be oriented in the airflow channel at a non-perpendicular angle with respect to the direction of airflow, particularly at a small angle, e.g. less than 45 degrees such as in a range of 20-30 degrees. The baffle may be substantially flat or may have an at least partially curved shape, for example being provided with an aerodynamic shape (wing, vane, etc.) for guiding, controlling and/or

alternatively affecting the airflow in a desired direction. The position and/or angle of the baffle with the direction of airflow in the airflow channel may be reversibly adjustable wherein a driver may be provided for the adjustment.

Such a baffle may be used for affecting a part of the airflow, for example for locally increasing and/or decreasing pressure and/or enhancing turbulence; it is also possible to generate a Venturi effect and/or a Coanda effect in a part of the apparatus for creating and/or enhancing a desired flow profile .

The baffle may be provided as liquid support and/or a liquid guide and the apparatus can be provided with a liquid supply and/or liquid drain which is connected or connectable therewith. As a consequence, particles can be trapped on liquid and/or a vapour can be provided for that in a part of the apparatus. The baffle may be profiled and/or may be provided with one or more projecting parts such as ribs, studs and/or a mesh. As a consequence, a desired liquid (flow) distribution across the baffle can be achieved. The projecting parts and/or mesh may be adapted for supporting a filter material on the profile parts and/or projecting parts such that gaps for liquid are created between the baffle and the filter which can be such that contact between the filter and the liquid is avoided. As a consequence, a wetted filter, in particular a fabric filter can be used, which has increased trapping capacity for particles and the filter may also at least partly affect and reduce

evaporation of the liquid from the gaps underneath. The liquid may be used for flushing at least a part of the filter and/or for trapping of particles and removing thereof. The filter may be relatively coarse, e.g. with a pore size in a range of 200- 2000 micrometre, preferably between 300 and 1000 micrometre such as between 500 and 800 micrometre. Relatively coarse particles may be trapped by the filter, smaller particles may pass through the filter and be trapped by the liquid and fine dust or

ultrafine dust may be agglomerated and/or trapped by an eventual vapour in the gap, and/or they can be flow again further through the filter into the apparatus to be filtered out eventually.

The apparatus may comprise a number of baffle that are placed in the airflow channel, wherein a first baffle extends at a first angle with respect to the direction of airflow and a second baffle extends at a second angle with respect to the direction of airflow, such that at least a part of the airflow is directed by the first baffle onto the second baffle, and wherein at least a part of the airflow is directed by the second baffle around the first baffle. Preferably, the baffles overlap each other, seen in the main direction of the airflow through the apparatus. In particular, the second baffle is provided as a liquid support and/or a liquid guide as indicated hereinbefore. Thus, by directing the airflow, a part of the particles which are present therein, in particular relatively large and heavy particles, are trapped by and/or on the second baffle plate, in particular on/in a filter and/or liquid which is provided on the second baffle.

One or more baffles may be located in or close to the above-described widening and/or restriction in the airflow channel, such that influencing of a flow profile and/or an installation space can be used effectively. More and/or

differently shaped baffles may be provided.

Furthermore, a filter is herewith provided for an apparatus as described herein, comprising one or more layers of filter material of F9 quality or a finer filter quality, wherein the filter material is provided with a carbon material, in particular active carbon, wherein the carbon material can be provided as powder between the layers of the filter material, wherein the filter can substantially be a cloth material, in particular a non-woven and/or woven material. The carbon may be provided with an average particle size of about 100 micrometre or smaller with a standard deviation of 5-15%, for example 10%, although it may also be more, for example 20%, but in any case such that the carbon material remains in the filter material.

The filter may be shaped as a bag filter wherein the walls of the bag or bags contain the one or more layers of filter material. In particular the filter may comprise F9 filter cloth .

Furthermore, in relation to the previous, herein a method for cleaning air polluted by solid particles is provided, comprising transporting the air to be polluted though an airflow channel of an apparatus via a supply opening of the airflow channel and discharging the air that is transported through the airflow channel via a discharge opening from the apparatus, and guiding the air to be cleaned along an ionizer, which is placed in the airflow channel, for ionizing the airflow and particles in the airflow and for creating agglomeration of ionized solid particles, wherein the flow area of the apparatus close to the ionizer is smaller than the flow area of the apparatus close to the filter at its upstream side,

characterized in that the method comprises filtering with a filter which is located at a position between the ionizer and the discharge opening, wherein the filter has a pore size which is larger than the size of at least a part of solid particles that are present in the supplied air and removing agglomerated particles from the air with the filter. The method may comprise the application of an apparatus as described herein.

The apparatus and/or the method as elucidated herein may trap particles of fine dust (particle size 10-2.5

micrometre) and ultra-fine dust (particle size up to 100

nanometre) and particles of intermediate size ranges (compare: Most Penetrating Particle Size " MPPS ' in HEPA filter) at high efficiency and with long operational life of the filters.

It is noted that filters of F9 quality and/or a finer quality are used only for filtering of - preferably pre-treated - indoor air up till now. However, it appears that such a material can be appropriately used in outdoor air, and for cleaning thereof, and in combination with large flow-through volumes, specifically when the flow area of the filter material is enlarged by providing the filter material in bag filter shape. It also appears that filters of F9 quality and/or a finer quality can be appropriately provided with an (active) carbon layer and that consequently an enhanced filter functioning for MPPS and ultra-fine dust particles can be achieved. Surprisingly it appears that in particular F9 material with a carbon powder layer of some dozens to a thickness of some hundreds micrometres (for example a thickness of 0.2 millimetre) in combination with high airflow velocities, despite of usual understandings, may be sufficient for trapping MPPS and ultra-fine dust particles from the air flowing through the filter. The interaction time of some minutes for adsorption of fine dust particles and smaller particles as being considered necessary up to now appears to be unnecessarily long when using the apparatus as described herein. The invention will hereafter be elucidated further with reference to the drawings. The drawings show in:

Fig. 1 a schematic cross-section through an apparatus according to the invention;

Fig. 2 a schematic cross-section through another apparatus according to the invention;

Fig. 3 a partly schematic cross-section through the apparatus according to Fig. 2, as indicated therein with the line III-III;

Fig. 4 a further embodiment of the apparatus;

Fig. 5 a schematic cross-section of still another embodiment of the invention.

In the figures the same parts are indicated by the same reference signs. However, not all of the parts required for a practical embodiment of the invention are shown in order to keep the picture simple.

Fig. 1 shows a schematic cross-section through an apparatus 1 according to the invention. The apparatus 1

substantially comprises an enclosure 2 which defines an airflow channel 3. The airflow channel 3 has a substantially elongate shape which extends from a supply opening 4 for supplying ambient air into the airflow channel. The airflow channel 3 extends up to a discharge opening 5 for removing air from the apparatus 1 which air flows through the airflow channel 3. The apparatus 1 further comprises an ionizer 6 for ionizing the airflow and particles present therein, which ionizer 6 is located in the airflow channel 3.

An effective transport of the air to be cleaned is obtained by a fan 7 which is located between the supply opening 4 and the ionizer 6 in the shown embodiment. The ionizer causes a static, electrical charge of particles being present in the airflow. If only a few particles are static charged remaining particles will be attracted by the electrical charge and

therefore form static charged agglomerates of particles. Such agglomerates have a larger size than the separate particles.

The particles, in particular the agglomerates, are trapped in a filter 8.

The apparatus 1 comprises a first part F which defines a first flow area of the airflow channel 3 and a flared second part S which forms a widening causing an increasing flow area of the airflow channel 3 of the apparatus 1 towards the filter 8, which substantially closes off the air transport channel.

Trapping of the agglomerates will may occur simply with a filter material that has significantly larger pores than the size of the separate, non-agglomerated particles. The effect of this is further that the filter 8 will have a significantly lower resistance than a filter which is designed for trapping the mentioned small particles and thus will have smaller pores.

The apparatus 1 is placed on an installation table 9 in order to be able to place the apparatus 1 on each desired surface. For example, the apparatus can be placed on a building in order to clean ambient air. The apparatus can also be placed in a residence room or the like in order to clean the air. In both cases an effect is obtained that solid particles are also removed from the air in the broad environment of the apparatus. According to the physical principle of distribution of materials in a medium such as solid dust particles in the air, the

distribution thereof will balance as much as possible. This means that the concentration of solid particles will be balanced quickly when the particles are removed from the air in a single position such as close to the apparatus 1 according to the present invention. Particles from the surrounding air will migrate in the direction of the apparatus 1 such that cleaning of the air is detectable at a large distance from the apparatus 1 according to the invention, as well.

The filter 8 may comprise a rectangular filter material, which provides the opportunity to cover a rectangular discharge opening 5 of the apparatus 1 by the filter material. The filter material may be accommodated in a cotton or linen cover in order to keep the filter material together. Preferably, the cover or the like has a light colour, such that it can be simply observed visually whether pollution has occurred and the filter has to be replaced. It is also possible to provide a pressure sensor in the apparatus 1 at the upstream side 10 and the downstream side 11 of the filter 8, such that the pressure difference can be used as a measure of pollution of the filter 8. A higher pressure difference will indicate a higher pollution than a lower pressure difference. A measurement with respect to an ambient air pressure and/or another reference value such as a measurement value after a maintenance inspection and/or during certain operational conditions can be used, as well.

Particularly, for such cases (using) a single sensor in the apparatus may suffice.

Preferably, the filter comprises an electrically conductive material which is applied through substantially the entire filter in order to optimize trapping of the ionized particles. For example, the filter material may comprise carbon, in particular active carbon, and the filter can be grounded. Due to the grounding the filter will become oppositely charged at the ionized particles and effectively trap and bind them.

Instead of a grounded filter it is also possible to apply an electrically charged filter wherein the electrical charge is opposite to the ionized charge of the particles.

The apparatus may be checked wireless or wired in order to monitor the condition. If a wireless system is used, this may be for example via wifi, gsm, Zigbee, or any other wireless system .

In order to facilitate access to the apparatus 1 a part

13 of the apparatus close to the fan may be pivotable away from a main part 12 of the apparatus 1, for example. In that case the main part 12 of the apparatus 1 may be fixed to the installation table 9, while the fan 7 is provided at the part 13 which is pivotable away. At the other end of the apparatus 1 a filter part 14 may be connected pivotable to the main part 12, such that the filter 8 can be replaced easily. By pivoting away the part 12 or 13 from the main part 12 access is also provided to the ionizers, for example for performing maintenance to them or to replace them.

The apparatus can be adapted in a simple way such that it is suitable for treating 15,000 cubic metres air per hour, through an airflow channel having a diameter of 80 cm and a discharge opening (filter surface) of 0.80 metre by 1.4 metre. In that case the air flows at 8 m/s through the airflow channel, and at about 4.5 m/s through the filter. By enlarging the filter surface (1.40 m by 2.4 m) and the diameter of the airflow channel to about 1.4 metre the capacity can be increased to 60,000 m3 per hour (the air flows at 30 km/h through the filter) . These values are indications and are not a limitation.

A self-supporting embodiment of the apparatus 1 can possibly be obtained when it comprises photovoltaic panels. The photovoltaic panels may drive the fan and the communication equipment for transferring the condition of the apparatus.

A rain sensor may be connected to the apparatus 1 in an advantageous manner when this is located in the ambient air in order to clean the ambient air. In case of rainy conditions the air pollution is very low since this will be washed away with the rain. Operation of the apparatus is not necessary in that case. Furthermore, a delay may be provided in order to keep the apparatus out of operation after a period of rain, for example during an hour, or any other desired time period.

A particle measurement device can measure the concentration of pollution in order to determine whether the apparatus 1 must be or must not be put in operation. The

particle measurement device may be placed in the near vicinity or at a larger distance, since the effectivity can be measured up to a large distance from the apparatus. For example, the distance may vary from about 0 metre to 500 metre, or even up to 1 kilometre.

Fig. 2 shows another embodiment which is the same as the one of Fig. 1 to a large extent, such that only deviations are emphasized. At the supply opening 4 an optional lattice 16 is applied in order to prevent disturbances of the apparatus due to heavy pollutions, objects and/or animals which could be carried by the airflow through the apparatus (see arrow W) . The ionizer 6 protrudes forwardly into the airflow channel 3.

The apparatus 1 is placed on the installation table 9 or an alternative chassis (not shown) rotatably around a

vertical axis A, for example by means of one or more bearings. Alternatively or additionally in an embodiment the apparatus 1 may be adapted rotatably about a horizontal axis transversely to the longitudinal axis, and/or the apparatus 1 can be adapted translatably, in particular height adjustable. Optionally the apparatus 1 is provided with one or more drive means (not shown) in order to set a position and/or orientation, which drive means can be operated and/or checked wireless or wired. The drive means may be adapted in order to allow non-driven changes of position and/or orientation of the apparatus, as well, for example by means of a de-locking and/or a freewheel device. An optional control face 17 may help to rotate the apparatus such that the supply opening 4 is in the wind direction.

The embodiment as shown has a first filter 18 and a second filter 19 in the airflow direction. The first filter 18 is a bag filter, for example, comprising, as usual in case of a bag filter, a series of bags 18A located next to each other (Fig. 3; only a few are shown), for example 5 or 10 bags, which together form the filter having a filter surface which is proportionally enlarged. However, in this case the bags 18A substantially consist of carbon material 21 arranged between two layers of F9 filter cloth 22. Other filter materials which have a higher filter capacity for MPPS particles and/or ultra-fine dust can be used, as well. Furthermore, it is possible to provide a first, possibly relatively wider, filter material in such a filter at an upstream side of the filter and to provide at a downstream side a different, possibly relatively finer filter material, and/or to provide two different layers of filter cloth. It is also possible to apply different layers of carbon material or different filter material in such bag

filters. A series of bag filters located behind each other and possibly different kinds of fine filters (for example HEPA or ULPA filters) is possible, but seems to be unnecessary. The filter materials may be provided with one or more electrically conductive materials and/or the carbon layer may be electrically conductive. At the front and/or rear side of the filter

conductive elements may be applied, as well, in order to apply a desired charge and/or a desired potential difference with the ionizers and/or in order to discharge static charge received by trapped charged particles.

The second filter 19 is located downstream of the first filter 18, close to the discharge opening 5. The second filter 19 comprises a support (not shown) being provided with an active carbon layer, for example an active carbon-coated PE foam (PE = polyethylene) . Preferably, the pore size of the second filter 19 is larger than the pore size of the first filter 18 but it may also be smaller or the same. Downstream of the second filter 19, as seen in the direction W of the airflow, an optional third filter 20 or a lattice is provided, which protects the first and second filters 18, 19. In case of a light-coloured second or third filter 19, 20 having sufficiently small pore size a discolouring on the second and third filter 19, 20, respectively, can indicate aging of filter material.

The first filter 18 may be electrically grounded or charged. Grounding may prevent building up of a charge on the filter 18 which is of the same type (negative/positive) as the one which is provided to the particles by the ionizer 6. The second filter 19 may be electrically grounded or charged, for example opposite (negative/positive) with respect to the ionizer 6 (negative/positive) . Due to this an electrical field may be applied between the first and second filters 18, 19 which may help agglomeration and/or attracting charged particles to one of both filters 18, 19.

In an embodiment (not shown) a chemical filter is applied on or close to the supply opening 4 of the apparatus 1 for trapping and/or for rendering aggressive chemicals harmless, for example sulphur-containing materials. This reduces quickly damaging the apparatus 1, and in particular the first and/or second filters 18, 19, by those materials.

An optional module 23 is connected to one or more optional sensors of the apparatus in order to detect and

possibly process its signals such as signals of the fan 7, the ionizer 6, a pressure sensor 24, a rain sensor 25, an airflow sensor and further sensors (not shown), for example. The module 23 may be connected (whether or not wireless) to an optional external control module 26 which may be in the form of an application or a more generally applicable user module, for example a mobile phone.

The apparatus is provided with optional air guides 27 at the discharge side 11, each having an entrance opening 28 including a first flow area and a discharge opening 5A including a second flow area which is larger than the first flow area which enlarges the flow area of the apparatus between the second filter 19 and separate partial discharge openings 5A which together form the entire discharge opening 5. An airflow through the apparatus 1 from the supply opening 4 to the discharge opening 5 experiences successively (i) an acceleration and pressure difference by the fan 7, (ii) ionizing of the particles being present in the airflow by the ionizer 6, (iii) a deceleration by the enlargement of the inner dimensions of the airflow channel, i.e. the flow area, wherein to present understandings of the applicant the deceleration causes uneven distributions between the particles and results in velocity differences between particles. After that (iv) a pressure increase occurs (just) upstream of the first filter 18 by mechanical and electrical effects of the first filter 18. One or more of these effects cause increased coagulation of small particles such that after that (v) a great part of particles present in the air are trapped in the first filter 18.

Subsequently, (vi) a new pressure loss occurs downstream of the first filter 18, and (vii) a new (local) pressure increase arises due to the presence of the second filter and (viii) a possible charge difference arises between the first and second filters 18, 19 which results in that particles which are not trapped yet will be promoted to coagulate in order to be trapped in the second filter 19.

In the present opinion of the applicants the varying pressures and potentials cause coagulation of particles in such a successful way that fine dust particles (particle size < 10 micrometre) up to ultra-fine dust particles (particle size < 0.1 micrometre) can be removed from an airflow at particular high effectivity also by relatively wide filters, up to about 100% in case of some particle sizes.

Fig. 4 shows an embodiment 100 which is similar to the one of Figs. 2-3 to a large extent, and which is further

provided with a widening D and a restriction C, such that the airflow channel 3 in the direction of airflow W provides

successively an increase and a reduction of the flow area.

Hence, the widening D functions like a diffusor and the

restriction C like a compressor. The widening S downstream of the restriction C causes a waist T and the flow area of the apparatus at or close to the filter 8 at the upstream side thereof is clearly larger than the flow area in the waist T downstream of the restriction C. The dimensions of the flow area of the airflow channel 3 downstream and upstream of the widening D and the restriction C may be unequal. The widenings D and S may lead to an increase of the flow area of 10%-50%; an increase between 50%-75% may be preferred. The widenings D and S may also lead to different sizes.

Fig. 5 shows an embodiment 110 which is comparable to Fig. 4. In this embodiment several ionizers 6 are visible, both in the first part F and in the waist T, and arranged such that they also increase turbulence in addition to ionization.

Furthermore, a first baffle 30 and a second baffle 32 are located in the airflow channel 3. The first baffle 30 extends at a first angle a with respect to the flow direction W, the second baffle 32 extends at a second angle β with respect to the flow direction W, both about 45 degrees or smaller; the angles a and β are reversibly adjustable, for example through pivots 34. An airflow from the first part F to the second baffle 32 is guided by the first baffle 30, after which the air flows through a gap between both baffles 30, 32, and around an end of the first baffle 30, guided by the second baffle 32. The baffle 30, 32 may be located at a distance from inner walls of and/or parts in the airflow channel 3 such that gaps are provided through which the air may flow. As a consequence, the baffles 30, 32 may cause increased pressure difference and/or turbulence in the air flow.

The second baffle 34 is provided with a filter material 36, particularly a fabric filter of which a supply may be present, for example on rolls 38. The baffle 34 is provided with ribs, in this case extending substantially in the plane of Fig. 5, such that the filter fabric 36 is supported and gaps for liquid transport are provided. A part of the filter material may be displaceable over the baffle 34, for example by rotation of the rolls 38 in order to be able to replace (parts of) the filter, for example due to fouling and/or wear. For such a displacement an adjustable drive means may be provided (not shown) . The baffle 34 is provided with a liquid support and a liquid guide and the apparatus 110 is provided with an optional liquid supply 40 and liquid drain 42 which are connected with respective optional reservoirs 44, 46 and in this case also with an optional pump and/or washing device 48 for pumping and/or cleaning or alternatively conditioning of one or more used liquids and/or liquids to be used. The liquid may be used for wetting and/or flushing the filter 36, for example, wherein liquid which has flown through the filter 36 can be drained by the baffle 34 and the drain 42, possibly for cleaning and/or re- use. Preferably, the liquid has a high vapour pressure such that it does not evaporate quickly at (expected) operating

temperatures and is preferably non-poisonous for the environment and biodegradable. Glycol solutions are deemed to be suitable. Preferably, the material of the filter 36 is machine washable.

Preferably, the filter 36 has larger pore size than the filters located further downstream. This filter can effectively remove gross pollutions, for example sand, pollen and the like from the airflow.

Furthermore, Fig. 5 shows bag filters 18A of which the filter material 18B is oriented at an angle γ of substantially about 5 degrees with respect to the direction of airflow W (the opening angle δ = 2γ of the filters as shown is about 10

degrees) causing grazing incidence on the filter material 18A of the direction of airflow W close to or at the filter 18 .

The invention is not limited to the embodiments as described hereinbefore and shown in the figures. The invention is only limited by the attached claims. For example, the

invention may comprise more widenings and reductions. The apparatus may be used on land and aboard ships.

The invention is also related to each combination of features which are described hereinbefore independently and/or in other combinations with respect to each other.