Field of the invention

The invention relates to an air cleaning device for removing compounds, in particular volatile organic compounds, from a flow of process air, and to a method for cleaning process air from compounds, in particular volatile organic compounds.

Background of the invention

EP1731213 in its abstract states: “A device for purifying a flow of fluid, such as air or water, comprising a chamber having an inlet and an outlet for said fluid, wherein the chamber is intended for containing filter material comprising randomly stacked inert particles, such as ceramic or synthetic particles, having a surface suitable for the attachment of micro-organisms able to digest contaminants from the fluid, wherein said chamber has a cylindrical, preferably circle-cylindrical, upper part as well as a cone-shaped lower part contiguous thereto and particularly situated underneath it, in which lower part the inlet or outlet has been arranged.”

EP3103545 in its abstract recites: The present invention relates to a method for purifying a gas comprising: a) feeding the gas to an absorber and bringing into contact said gas with a stream to obtain a liquid and a purified gas stream ; b) feeding the liquid to a conditioning tank and adding a mineral nutrient medium and a suitable amount of base to the liquid to obtain a liquid effluent; c) feeding the liquid effluent to an anaerobic bioreactor to obtain a biomethane stream and a liquid stream; d) feeding the liquid stream to a degasser to obtain a gas stream and a stream; and e) recirculating the stream by feeding it to the absorber.”

US5413936 in its abstract describes: “A cylindrical vessel having a horizontal, longitudinal axis of rotation is filled with biofilter material and receives gases through a perforated dispersion pipe located along the axis. Humidified gases pass through the biologically active filter material where the gases are converted into elemental gases, carbon dioxide, biomass, or water. The vessel is lined with geotextile material which acts as a collection plenum for the gases which flow radially outward to the lining. Collection pipes located at regular intervals between the lining and the vessel conduct the gases to a manifold, also located on the axis. The vessel is rotated periodically, e.g. weekly, for several rotations in order to mix the filter material, break up any compacted material, and collapse any fissures.”

KR100598317B1 in its abstract describes: “PURPOSE: A high efficiency deodorization equipment which can remove an inorganic odorous gas and an organic odorous gas respectively by installing two media modules within a biological deodorization equipment and varying microorganisms living in the respective media modules is provided.

CONSTITUTION: A high efficiency deodorization equipment comprises: a housing(20) having an inlet(40) formed on a lower portion thereof to flow in odorous gases and an outlet(220) formed on a top portion thereof to exhaust treated gases; a first media module(180) installed within the housing such that various sub-modules filled with biological media are fixed within a reactor; a second media module(140) installed under the first media module such that various sub-modules filled with biological media are fixed within a reactor; a first spray nozzle(200) installed between the first and second media modules; a spray amount control system installed on a lower portion of the housing to control a spray amount; and an inflow gas distribution pipe(120) for ejecting gas flown in through the inlet upward from a lower part of the second media module, wherein the inlet has a UV lamp(80) installed in an inner central portion of a predetermined space thereof and a photocatalyst(lOO) coated on an inner surface thereof.

US6644890 in its abstract describes: “A method for treating oxidable gas generated from waste at a dumping area and to the structure of the dumping area. The dumping area has an organic waste layer covered with a sealing layer that prevents the absorption of water, with a drying layer and a surface layer. Oxidable gas is generated and directed through an aperture formed in the sealing layer and made to spread in, the lateral direction with the help of one or several flow controllers so that the gas ends in the surface layer to become biologically oxidized. The aperture may be provided with a cover, and the gas flow controllers may be perforated pipes extending radially from a side of a well. The oxidation of gas may be intensified by directing air and/or moisture from a piping to the surface layer.”

US2004/023363 in its abstract describes: “A filter system for removing organic, odor-causing substances from air has a filter bed which includes porous, particulate, non-compostable material and microorganisms capable of digesting the odor-causing substances. The particulate material of the bed is preferably lava rock, pumice or sandstone. A method of filtering air which contains organic, odor-causing substances, such as exhaust air from a process of thermophilic bacterial digestion of organic waste matter, includes providing a filter bed of particulate, porous, non-compostable material, inoculating the filter bed with a culture of microorganisms and passing the air through the filter bed.”

Summary of the invention

A disadvantage of prior art is that in time, most of the devices clog due to excessive growth of microbiology. Air does not flow homogeneously through the known devices or may even get blocked. In particular, this takes place at or near the inlet of the known device.

Hence, it is an aspect of the invention to provide an alternative device, which preferably further at least partly obviates one or more of above-described drawbacks.

There is provide an air cleaning device for removing volatile organic compounds from a flow of process air, comprising:

- a container for holding filter material comprising particulate material and comprising a container air inlet and a container air outlet at opposite ends of said container and said filter material between said container air inlet and said container air outlet and providing an axial flow path from said container air inlet to said container air outlet through said filter material for bringing said process air and said filter material in contact with on another along said axial flow path;

- an airflow modifier in said container and comprising a modifier inlet fluidly coupled to said container air inlet and comprising at least one radial modifier outlet inside said container for in operation providing a flow of air in said container in a radial direction with respect to and away from said axial flow path, in particular a series of radial modifier outlets arranged radially about said axial flow path.

The proposed configuration allows a smaller space for the inlet construction in the container. Furthermore, it allows a larger opening for accessing the interior of the device. It was also found that the flow of air can be controlled better as the pressure drop at the inlet is reduced. The construction reduced the growth of biomass near the inlet. There is further provided a method for cleaning process air from volatile organic compounds, said method comprising providing a container substantially filled with filter material comprising particulate material and defining an axial flow path through said filter material, introducing said process air into said container contacting said filter material with an airflow substantially in a radial direction.

In an embodiment, the airflow modifier comprises a series of radial modifier all arranged radially about said axial flow path and near the modifier inlet.

The device can for instance be used to treat process air comprising organic compounds. Example of organic compounds, in particular volatile organic compounds (at atmospheric conditions) are styrene, ethanol, ethylacetate, etoxypropanol, n- propanol, xylenes, butanol, and combinations thereof. These can for instance be present in process air in painting or printing processes.

In operation, in an embodiment the axial flow path direction is functionally parallel to the working line of the force of gravity. In an embodiment, the axial direction will be functionally in vertical direction. In this way, in an embodiment where moisture is provided, the moisture will drip down and will be in counterflow with the flow of air.

In an embodiment, the airflow modifier comprises a radial flow outlet end for providing said flow of air in said radial direction, in particular said radial flow outlet end comprises said series of radial modifier outlets, in particular which in axial direction extends above said airflow modifier inlet.

In an embodiment, the airflow modifier comprises an inlet section comprising said modifier inlet and further comprising an air channel running into said container and ending in the radial flow outlet end. In particular, it debouching in, or flows out into, the radial flow outlet end.

In an embodiment, the radial flow outlet end is provided offset of said inlet section, in particular offset in direction of said container air outlet.

In an embodiment, the airflow modifier comprises a swirl section between said modifier inlet and said modifier outlet having a swirl axis substantially parallel to said axial flow path. In a particular embodiment, the swirl section is provided in said inlet section. In particular, the swirl section is provided in the air channel. In a more particular embodiment, it debouches in said radial flow outlet end. The additional swirl motion further reduced clogging though growth of microbiology. It further allows reduction of flow speed.

In an embodiment, the airflow modifier comprises said radial flow outlet end axially above the swirl section.

In an embodiment, the radial flow outlet end comprises an end plate. In a particular embodiment, the end plate extending beyond said series of radial modifier outlets to provide an overhang for said series of radial modifier outlets in said radial flow outlet end.

In an embodiment, the container has a substantially circular cross section, in particular said container is substantially circle cylindrical, in particular having said container inlet in an axial outer wall or a cylindrical wall near an end of said container.

In an embodiment, the container has an axial axis at its rotational axis and wherein said airflow modifier has its radial flow outlet aligned with said axial axis. A cylindrical shape further improves the flow in combination with placement of the inlet section.

In an embodiment, the air cleaning device further comprises a container fluid inlet, in particular a spray or vapour inlet, provided at or near the container air outlet for providing a fluid flow in counter current and substantially axial direction with respect to said process air. In an embodiment, the inlet section provides a flow channel for the process air, and a separated, parallel fluid channel for allowing a counter current flow of fluid. It allows spraying water to exit the container at the bottom unobstructed. Normally biomass can grow in the exit or outlet, making the water exit at the bottom of the air modifier increases the outlet sectional area decreasing obstruction by biomass.

In an embodiment of the method, the air is brought in a swirl flow motion about an axially directed swirl axis in addition to said substantially radial flow direction.

In an embodiment the method comprises providing a moisture of vapour flow comprising water in counter current with said airflow.

There is further provided a kit of parts for the air cleaning device, comprising said substantially cylindrical container and said airflow modifier, in an embodiment further comprising particulate filling material allowing grafting of bio-material microbiology, in particular comprising bacteria. In an embodiment, the airflow modified further comprises a swirl section for in operation adding a swirl to said flow of air, adding a tangential flow direction component to said flow of air, wherein said swirl section comprises a circle cylindrical chamber having an inlet in a cylinder wall for receiving said incoming flow of air and forcing it in a tangential direction, and opening axially into said radial flow outlet end.

In an embodiment, the inlet section is provided with an inlet section bottom wall and comprising supports for allowing a fluid flow path at an opposite side of said inlet section bottom wall and in counter current with said flow of air in said incoming flow direction F in the inlet section.

Use of an air cleaning device according to any one of the preceding claims for processing a flow of production air resulting from a printing process, a coating process, a painting process, in particular treating processing air comprising compounds selected from styrene, ethanol, ethylacetate, etoxypropanol, n-propanol, xylenes, butanol, and combinations thereof.

There is further provided an airflow modifier for an air cleaning device, comprising a modifier inlet, an inlet section providing a flow of air in an incoming flow direction F and comprising an outlet at an end remote from said modifier inlet and forcing said flow of air in an axial direction substantially perpendicular to said incoming flow of air, and comprising a radial flow outlet end for providing said flow of air to exit said airflow modifier in radial directions substantially perpendicular to said axial direction, in particular said radial flow outlet end comprises a series of radial modifier outlets, in particular said series of radial modifier outlets are in axial direction above said airflow modifier inlet, radially about said axial direction, more in particular said radial flow outlet end comprises a circumferential wall provided with said series of radial modifier outlets.

There is provide an air cleaning device for removing volatile organic compounds from a flow of process air, comprising:

- a container for holding filter material comprising particulate material and comprising a container air inlet and a container air outlet at opposite ends of said container and said filter material between said container air inlet and said container air outlet and providing an axial flow path from said container air inlet to said container air outlet for contacting said process air with said filter material;

- an airflow modifier in said container and comprising a modifier inlet fluidly coupled to said container air inlet and comprising at least one radial modifier outlet inside said container for in operation providing a flow of air in said container in a radial direction with respect to and away from said axial flow path, in particular a series of radial modifier outlets arranged radially about said axial flow path.

The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the flow of air or water a source to a drain, wherein relative to a first position within a flow of fluid from the source , a second position in the flow closer to the source is “upstream”, and a third position within the fluid flow further away from the source is “downstream”.

The term “substantially” herein, such as in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

The term "functionally" will be understood by, and be clear to, a person skilled in the art. The term “substantially” as well as “functionally” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective functionally may also be removed. When used, for instance in “functionally parallel”, a skilled person will understand that the adjective “functionally” includes the term substantially as explained above. Functionally in particular is to be understood to include a configuration of features that allows these features to function as if the adjective “functionally” was not present. The term “functionally” is intended to cover variations in the feature to which it refers, and which variations are such that in the functional use of the feature, possibly in combination with other features it relates to in the invention, that combination of features is able to operate or function. For instance, if an antenna is functionally coupled or functionally connected to a communication device, received electromagnetic signals that are receives by the antenna can be used by the communication device. The word “functionally” as for instance used in “functionally parallel” is used to cover exactly parallel, but also the embodiments that are covered by the word “substantially” explained above. For instance, “functionally parallel” relates to embodiments that in operation function as if the parts are for instance parallel. This covers embodiments for which it is clear to a skilled person that it operates within its intended field of use as if it were parallel.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices or apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to an apparatus or device comprising one or more of the characterising features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

Brief description of the drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 schematically depicts an embodiment of the air cleaning device in transparent view;

Figure 2 depict an embodiment of an airflow modifier;

Figure 3 the airflow modifier of figure 2 in transparent view, and

Figure 4 the swirl section of the airflow modifier of figures 2 and 3.

The drawings are not necessarily on scale

Description of preferred embodiments

Figure 1 schematically depicts an embodiment of the air cleaning device in transparent view. The air cleaning device 1 comprises a container 2 with a cylindrical wall 2 or axial outer wall 2. The container 2 has a container inlet 3 and a container outlet 4. The container inlet 3 is provided in the cylindrical wall 2 near an end of the container 2. In this embodiment, the container is circle cylindrical. It can also have a more elliptical cross section, but circle cylindrical is easy to make and to purchase. Furthermore, is has a minimal amount of corners and edges. The container outlet 4 is here provided at the axial axis A of the container 2. It provides an outflow of air (in operation) in axial direction. Air flowing from the container inlet 3 to the container outlet 4 will provide a largely axial flow of air if the airflow modifier 5 were not present.

Usually, the container 2 holds filter material, not indicated. In many state of the art devices, above the air inlet there is a grid holding the filter material. In this way, an axial air flow contacts the filler material in the container. Thus, an axial airflow is generated. A container can be up to 15 meters high. The container 2 can have a diameter of between 1 and 10 meter, in particular the diameter is between 3 and 5 meters.

The current air cleaning device comprises an airflow modifier 5. That will be further discussed with reference to figures 2-4. The airflow modifier 5 here rests on an end wall of the container 2, here the lower end wall of the container 2. The airflow modifier 5 here induces an outgoing flow of air having a swirl S as indicated. In this way, the air coming out of the airflow modifier 5 of this embodiment has both a radial directional component and a swirl S. The swirl S provides in fact a tangential directional component to the airflow.

In figure 1, the flow of incoming air is indicated with F. The axial axis A of the container 2 is indicated, as a reference for the axial direction A. Furthermore, the radial direction R is indicated.

In figures 2-4, an embodiment of an airflow modifier 5 is depicted in more detail, with figure 2 depicting a 3D view of an embodiment of an airflow modifier 5, figure 3 the airflow modifier 5 of figure 2 in transparent view, and figure 4 an inlet section with a swirl section of the airflow modifier 5 of figures 2 and 3. In this embodiment, a combination of radial airflow and the swirl or tangential flow component is provided.

The airflow modifier 5 has an inlet section 8 comprising the modifier inlet 6. The modifier inlet 6 is in figure 1 fluidly coupled with the container inlet 3. It provides a radially incoming flow or air F. Here, the inlet section 8 provides a flow of air F in radial direct R to the axis of container 2. The flow modifier 5 comprises a radial flow outlet end 9. The radial flow outlet end 9 is provided with radial modifier outlets 7. These outlets 7 are here openings in a circumferential wall of the radial flow outlet end 9. At its end remote from the inlet section 8, the end of the radial flow outlet end 9 comprises radial flow outlet end roof or wall 13. Here, the wall is provided with some small holes 14 for providing a small fraction of air in the axial direction. Usually, this axial fraction will be less than 10% (flow rate). Usually, the axial flow will be less than 5%. The radial flow outlet end roof or wall 13 has an overhang 15 extending beyond the radial modifier outlets 7 in order to force the air in even further radial direction away from the axial direction or axis of the container 2.

In its side directed towards the inlet section 8, the radial flow outlet end roof or wall 13 near the circumferential wall comprises a groove for preventing water to flow into the flow modifier 5.

Figures 3 and 4 show the interior of the airflow modifier 5. It shows a swirl section 12 in the inlet section, in particular, the swirl section 12 is provided at the end of the air channel provided by the inlet section 8. The inlet section 8 has an inlet section inlet here forming the air modifier inlet 6. In the current embodiment the inlet section has a rectangular cross section. Other cross sections may be possible, like round. Rectangular cross section provides an easier coupling to a swirl section 12, see further. The inlet section 8 has a bottom wall 11, inlet section upper wall 20, and inlet section side walls 18 and 19. The bottom wall 11 is raised or elevated with respect to the side walls 18, 19 in order to provide a fluid channel 10, in particular a water channel 10 below the bottom wall 11.

In order to provide a smooth flow of process air F into the swirl section, the inlet section 8 comprises a flow plate 16 which directs the flow of process air F into the swirl section 12. The swirl section 12 adds a tangential flow component to the flow of process air F. The swirl section 12 is in this embodiment comprises a circle cylindrical chamber. It comprises a swirl section cylindrical wall 17 (fig. 4). The axis of the swirl section, in particular of the circle cylindrical wall, is functionally aligned with the axial axis A. The flow of process air F (with the air cleaning device in operation) is brought into a rotation motion about the axis of the swirl section cylindrical wall 17 and about the axial direction A.

The swirl section connects to a radial flow outlet end 9. This has circumferential walls having outlet openings for a flow of process air F. These openings provide air flowing in a radial direction away from the axial axis A. Due to the swirl section 12, the flow of process air flowing out of the radial flow outlet end 9 has a tangential flow component. The openings in the circumferential wall or walls provide a radial flow component.

In the current embodiment, the radial flow outlet end 9 in axial direction extends from, in operation above, the inlet section 8.

The air cleaning device 1 further is adapted for providing a fluid flow G as a counter-current flow with respect to the flow of process air F. In particular, the air cleaning device 1 comprises a container fluid inlet, in particular a spray or vapour inlet, provided at or near the container air outlet for providing a fluid flow G in counter current and substantially axial direction with respect to said process air. In operation, the fluid flow is not always continuously, but can be intermittent.

The inlet section 8 is provided with an inlet section bottom wall 11. In an embodiment as depicted, it comprises supports at a side opposite to the process air side for allowing a fluid flow path at an opposite side of said inlet section bottom wall 11 and in counter current with said flow of air in said incoming flow direction F in said inlet section. In this way, fluid flowing down in counter current flow can be collected below the inlet section bottom wall 11. The inlet section bottom wall 11 this separates the incoming flow of process air F and the outgoing flow of fluid G.

In operation, the flow of process air can be between 50 m ³ and 5000 m ³ per m ² of container cross sectional area (with respect to the axial direction). In particular, the flow is 300-2000 m ³ per m ² of container cross sectional area (with respect to the axial direction). Air speed will be kept low enough to maintain a laminar flow. The flow of fluid, in particular water or water vapour, is 1-10 m ³ per m ² of container cross sectional area. In particular, the fluid flow is 2-5 m ³ per m ² of container cross sectional area. Often, fluid is sprayed for 3-6 minutes, for example. Then, a pause of 20-180 minutes is set. This is done intermittent. It may be done in regular cycles.

The container 2 will in most cases be filled with particulate material. Often, pearls or small spheres or beats of polymer material are used. In particular, rings of polymer, like polypropylene, polyethylene, and combinations thereof. These last longer. The particulate material is grafted with microbiology for instance bacteria. Often, a mixture of naturally available sludge bacteria and bio-material is used. After some time, an equilibrium is reached between the microbiology and the incoming VOC’s.

It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person. These embodiments are within the scope of protection and the essence of this invention and are obvious combinations of prior art techniques and the disclosure of this patent.

Reference numbers

1 air cleaning device

2 container/axial outer wall

3 container inlet

4 container outlet

5 airflow modifier

6 a modifier inlet

7 modifier outlet

8 inlet section

9 radial flow outlet end

10 moisture chamber

11 inlet section bottom wall

12 swirl section

13 radial flow outlet end wall or roof

14 water holes

15 overhang or offset

16 airflow guiding wall

17 swirl section cylinder wall

18 inlet section side wall

19 inlet section side wall

20 inlet section upper wall

21 container cylinder wall

A axial direction

R radial direction

F flow direction process air

G flow direction fluid

S swirl