WO2003047723A1

WO2003047723A1 - Method for removing oxidable substances from an air flow, and device for carrying out the method

Info

Publication number: WO2003047723A1
Application number: PCT/DE2002/004190
Authority: WO
Inventors: Klaus Arnold; Harald Ertl; Johann Göbel; Helmut Oberpriller; Christian Wolff
Original assignee: Eads Deutschland Gmbh
Priority date: 2001-11-30
Filing date: 2002-11-13
Publication date: 2003-06-12
Also published as: DE10158970A1

Abstract

The invention relates to a method for removing oxidable substances from an air flow, especially from the air in aircraft cabins, and to a device for carrying out said method. The invention is characterised in that additional means (3a, 3b, 4; 12) are provided for producing oxidation agents which act on the substances adsorbed by the adsorbing agent (5; 6), decomposing said substances by means of oxidation, in order to regenerate the adsorbing agent (5; 6). The reaction products obtained exhibit a reduced adsorption capacity, such that they can be removed from the adsorbing agent (5; 6).

Description

Process for removing oxidizable substances from an air stream, and a device for carrying out the process

The present invention relates to a method for removing oxidizable substances from an air stream, in particular from the cabin air in aircraft, and a device for carrying out this method.

It is known that an air stream to be cleaned e.g. is passed through an adsorber. The adsorber adsorbs the pollutants contained in the air flow to a certain degree of saturation. When saturation is reached, the adsorber cannot absorb any more pollutants from the airflow to be cleaned, so that the degree of cleaning decreases significantly. In order to continue the adsorption process, a regeneration of the adsorber is required. The current technologies for regeneration of the adsorber are known to include thermal desorption, displacement desorption (e.g. by means of water vapor), and microwave desorption.

Thermal desorption takes place through targeted heating of the adsorber. However, this has the disadvantage that a high expenditure of energy is necessary in order to achieve the required high desorption temperatures. In addition, thermal desorption causes the adsorber to heat up considerably, which in turn can have a negative impact on its service life. In addition, the choice of adsorber materials is limited due to the required thermal stability.

Displacement desorption by means of water vapor also has the disadvantage that a high expenditure of energy is required. In addition, corrosion problems can be expected with this type of regeneration. In the case of microwave desorption, the relatively high technical outlay is disadvantageous. In addition, expensive precautions for shielding the microwave radiation are required, so that such treatment systems are usually bulky and expensive.

The present invention is therefore based on the object of providing a method and a device for removing oxidizable substances from an air stream which are distinguished by a simple design and require little energy expenditure. The cleaning effect should be as high as possible and the thermal load on the adsorber material should be as low as possible.

The object is achieved by a device which comprises an adsorbent for adsorbing oxidizable substances from an air stream to be cleaned, and which is characterized according to the invention in that a means for producing oxidizing agents is also provided, the oxidizing agents for regeneration of the adsorbent being affected by the Adsorber agent acts adsorbed substances and decompose them oxidatively, the resulting reaction products have a reduced adsorption capacity, so that they can be removed from the adsorbent.

The central idea here is that the regeneration of the adsorbent is based on an oxidation of the substances adsorbed by the adsorbent. This oxidative degradation leads to the formation of smaller molecules and / or molecular fragments as reaction products. The adsorbing capacity decreases with decreasing molecular size, so that the desorption of the organic degradation products and thus the regeneration of the adsorber is realized in a flow-through adsorber.

Such a device has the advantage that, due to the regeneration of the adsorbent by means of oxidative degradation, there is no heating of the adsorbent he follows. Thus, the adsorbent itself is not thermally stressed, which can have a positive effect on its life. In addition, due to the low thermal load, there is a greater variety in the choice of adsorber material.

The device according to the invention is particularly suitable for the degradation or removal of gaseous organic substances and / or organic particles from an air stream to be cleaned. Ozone and / or oxygen-containing radicals are preferably used as the oxidizing agent. These oxidants can be particularly easily and effectively with the help of a

Plasma generators, in particular via a dielectric barrier discharge, are generated.

According to a first embodiment, it is advantageous that the means for generating the oxidizing agent consists of an electrode system with barriers in between, the adsorber means also being integrated in the arrangement of electrodes and barriers. This means that the plasma generator and adsorbent are integrated in one unit. In this way it is achieved that the oxidizing agents required for the oxidative degradation of the adsorbed substances are generated in the immediate vicinity of the adsorbed substances. It is particularly expedient for the adsorber to sandwich an electrode with a barrier.

According to a further embodiment, which is based on a continuously operating rotary adsorber, the air flow to be cleaned provides a first one

Airflow that flows through a rotatably mounted adsorbent. The means for generating the oxidizing agents is connected upstream of the rotating adsorbent and the oxidizing agents are generated in a second air stream. The second air stream can be introduced into the adsorber via an inlet such that the second air stream spatially separates the adsorber from the first

Airflow flows through, due to the rotational movement of the adsorber second air stream flows through a different cross-sectional area of the adsorbent for regeneration purposes.

The advantage of this continuously operating rotary adsorber is that it ensures permanent operation in which adsorption and desorption take place in different sub-areas of the adsorbent due to the rotatable arrangement.

It is expedient to arrange the axis of rotation in the longitudinal direction of the adsorbent. In addition, the adsorber advantageously has a plurality of channels, which are also arranged to run in the longitudinal direction, so that the air currents flow through the adsorber along the channels.

It is also advantageous in this embodiment that the inlet has sealing lips which slide on the inlet cross-sectional area of the adsorbent when the adsorber is rotating, so that an airtight introduction of the second air stream into the adsorber is ensured. In this way, an unwanted escape of the second air stream is prevented simply and effectively. The inlet is expediently designed in the form of a sector.

According to a further embodiment, which represents a multi-flow adsorber system, the means for generating the oxidizing agents is in turn connected upstream of the adsorbing agent and the oxidizing agents are generated in a second air stream. However, the first and second air streams flow through the adsorbent alternately, clocked in time, so that adsorption and regeneration of the adsorbent take place successively in time. In this case, the adsorber can be arranged to be stationary but also rotating.

In this multi-flow adsorber system, too, the adsorber means expediently has a plurality of channels which are arranged running in the longitudinal direction thereof, so that the first and second air flows Flow through adsorbent along the channels. It is particularly effective to introduce the first and second air streams over the same inlet cross-sectional area in order to enable quasi-continuous operation.

Furthermore, it is expedient to connect a destroyer downstream of the adsorbent in order to remove the residual proportion of oxidizing agents that is possible in the air streams after flowing through the adsorbent. The residual proportion of oxidizing agents is expediently converted catalytically.

The object on which the invention is based is further achieved by a method in which the oxidizable substances contained in an air stream to be cleaned are adsorbed by an adsorbent, and which is characterized according to the invention by the following steps: generation of oxidizing agents;

Regeneration of the adsorbent by the action of the oxidizing agent on the substances adsorbed by the adsorbent and oxidative degradation of these substances, whereby reaction products are formed which have a reduced adsorption capacity; and removing the reaction products from the adsorbent.

A particularly effective embodiment is present when the reaction products are removed continuously or at intervals with the air flow to be cleaned (cf. first embodiment).

Another alternative of the method according to the invention is characterized in that the first air stream to be cleaned is passed through a rotating adsorber; that the oxidizing agents are generated in a second air stream; that the second air stream is introduced into the rotating adsorber in such a way that the first and second air streams flow through the adsorber spatially separated from each other, so that due to the rotation of the Another cross-sectional area of the adsorbent is flowed through by the second air stream for regeneration purposes.

Advantageously, the first and second air streams flow through the adsorber medium along channels formed therein, so that both air streams can be removed or discharged separately after flowing through the adsorber medium.

According to a further alternative method, the first air stream to be cleaned is passed through a rotating or stationary adsorber; the oxidizing agents are generated in a second air stream which is introduced into the adsorbent, the first and second air streams being alternately fed into the adsorbent so that adsorption and regeneration of the adsorbent are carried out in succession.

The first and second air stream expediently each flow through the same cross-sectional area of the adsorbent.

Furthermore, it is expedient to direct the air streams to a destroyer after they have flowed through the adsorber so that the respective air stream is removed from the residual proportion of oxidizing agents contained by catalytic degradation.

The device according to the invention and the method according to the invention are used in particular in the treatment of cabin air in aircraft or motor vehicles. In addition, however, an application is also conceivable in all areas where exhaust air has to be cleaned.

The invention is described in more detail below with reference to the attached figures. In which shows: Figure 1 is a schematic sectional view of a first embodiment according to the present invention.

Fig. 2 is a schematic representation of a further embodiment according to the present invention, which comprises a continuously operating rotary adsorber;

FIG. 3 shows a top view of the inlet cross section of the rotary adsorber according to FIG. 2; and

FIG. 4 shows a schematic three-dimensional representation of FIG. 3.

Fig. 1 shows a schematic representation of a sectional view of a first embodiment of the device according to the invention. For air treatment, the air stream 1 to be cleaned flows through the arrangement 2. The smallest amounts of pollutants must be removed from the air stream 1 (concentrations in the ppb to ppm range). The pollutants are primarily in the form of gaseous organic substances and organic particles and can be oxidized. The gaseous organic substances are in particular VOCs (English: olatile organic compounds), which among other things. all typical

Contains hydrocarbons, aldehydes, ketones etc. The substances that do not fall under this category, which are referred to here as organic particles, have a size of typically 0.01 μm to 10 μm.

The arrangement 2 through which the air stream 1 flows consists of a

Electrode system which has alternately arranged electrodes 3a and 3b which are acted upon by positive or negative voltage. In addition, a barrier 4 is arranged between the individual electrodes 3a, 3b. When a voltage is applied to the electrodes 3a, 3b, a so-called "cold" plasma is generated via a dielectric barrier discharge. As a result, ozone and / or in such an air-flowed plasma generator oxygen-containing radicals are generated, which are chemical oxidizing agents.

At the same time, an adsorber 5 is provided within the arrangement 2 shown in FIG. 1, which, for example, surrounds an electrode 3a or 3b with an associated barrier 4 in a sandwich-like manner. Of course, the adsorber 5 can also be arranged in a different way in the arrangement 2, but the arrangement shown in FIG. 1 is particularly easy to produce. The adsorber 5 consists of an adsorptive carrier material that is not sensitive to oxidation (e.g. zeolites). The adsorber 5 has the task of adsorbing the pollutants contained therein from the air stream 1 flowing through the arrangement 2. That is, the absorber 5 absorbs the gaseous organic substances and organic particles contained in the air stream 1. This is the well-known adsorption process which, however, leads to saturation of the adsorbent after a while if no further precautions are taken to regenerate it.

The regeneration of the adsorber 5 is brought about by the fact that due to the plasma generator 3a, 3b, 4 superimposed on the adsorber 5, oxidizing agents are formed within the arrangement 2, which act on the adsorbed substances and break them down oxidatively. The resulting reaction products have an increasingly smaller molecule or molecular fragment size. As the molecular size decreases, the adsorption capacity - i.e. the ability to be adsorbed by the adsorbent - decreases, these "downsized" molecules can no longer be adsorbed. They can be easily removed in a through-flow adsorbent, so that the desorption of the organic reaction products and thus the regeneration of the adsorbent is ensured.

Alternatively, the embodiment according to FIG. 1 can also be used for a multi-flow system. At least two of the arrangements 2 are necessary for this which the air flow to be cleaned is continuously conducted. By alternately switching the plasma generator on and off, one arrangement 2 is regenerated, while the other adsorbs the pollutants contained in the air stream to be cleaned.

The combination of adsorbent and plasma generator can of course also be realized in another way. Adsorber and plasma generator can e.g. be formed separately, the plasma generator being connected upstream of the absorber in order to load the air stream to be cleaned with oxidizing agents; similar to an arrangement which is described below with reference to FIG. 2.

FIG. 2 shows a further embodiment, which has a continuously operating rotary adsorber 6. The rotary adsorber 6 is of cylindrical symmetry and has a plurality of channels 7 which are arranged to run in the longitudinal direction A of the rotary adsorber 6. The axis of rotation 9 of the adsorber 6 also points in the longitudinal direction A. The rotation, which is approximately 10 revolutions per hour on the order of magnitude, takes place in the direction of the arrow B. The adsorber here also consists of an adsorptive, oxidation-insensitive material.

The air flow to be cleaned is denoted by reference numeral 1 analogously to the embodiment according to FIG. 1. The air stream 1 to be cleaned, hereinafter also referred to as the first air stream, flows via the inlet cross-sectional area 10 into the rotary adsorber 6, so that the air to be cleaned is inside the

Rotation adsorber 6 flows along the channels 7 in the longitudinal direction A. As can be seen from Fig. 2, the inlet cross-sectional area 10 is partially covered by an inlet 11, which will be described in more detail below.

As in the first embodiment according to FIG. 1, the adsorbs

Rotational adsorber 6 the oxidizable substances contained in the air stream 1, in particular gaseous organic substances and / or organic particles. The regeneration adsorber 6 is, however, regenerated with the aid of a second air stream 13. For this purpose, the plasma generator 12 is connected upstream of the rotation adsorber 6. The plasma generator 12 consists of an electrode system which has an anode 12a and a cathode 12b, and a barrier 12c arranged between them. The plasma generator 12 serves to generate oxidizing agents, in particular in the form of ozone and / or oxygen-containing radicals, in the second air stream 13. This second air stream 13 loaded with oxidizing agents is fed to the rotary adsorber 6 via the inlet 11 for regeneration purposes. In this case, the inlet 11 covers a partial area of the inlet cross-sectional area 10, which is designed as a sector in FIG. 2 by way of example. In addition, a sealing lip 14 is arranged on the inlet 11 on its surface sliding on the inlet cross-sectional area 10 of the rotary adsorber 6. This prevents the second air flow 13 from escaping when it is introduced into the rotating rotary adsorber 6.

Due to the rotation of the adsorber 6, both the first and second air stream 1, 13 are introduced into the rotary adsorber 6 at any time via a different cross-sectional area. The first air stream 1 flows in each case up to the inlet cross-sectional area 10 covered by the inlet 11. The second air flow 13 is introduced into the rotary adsorber 6 via the inlet 11 and the cross-sectional area Si shown hatched in FIG. 3. At a later point in time, this cross-sectional area is located at the point Si 'shown in dashed lines in FIG. 3 due to the rotation of the adsorber 6. At the same time, this means that at this later point in time the air flow 13 is introduced via another cross-sectional area of the adsorber 6, which in turn corresponds to the area covered by the inlet 11. Since the rotation is carried out continuously, the second air flow is continuously introduced into a different cross-sectional area, which is designated by an example Sj for a further point in time in FIG. The second air stream 13 thus flows through Regeneration purposes each have a different cross-sectional area Qι of the adsorber 5, as can be seen from the representation analogous to FIG. 3 in FIG. 4. When flowing through the respective cross-sectional areas Qj, the adsorbed substances are broken down in accordance with the oxidation reaction described above, with the formation of reaction products with reduced adsorption capacity.

It should also be noted that in the process described above, the first and second air streams 1, 13 flow through the rotary absorber 6 in a spatially separated manner due to its channel-shaped configuration. Thus on

The outlet of the adsorber cleaned air flow 1 and air flow 13 through which flow passes can be removed separately in a simple manner. The air flow 13 can be discharged via an outlet 16 which is configured analogously to the inlet 11. At the outlet 16 as well as at the inlet 11, a corresponding sealing lip (not shown) is provided for sealing.

According to a further embodiment, the cylindrical adsorber 6 shown in FIG. 2 and provided with channels 7 is used in a so-called multi-flow adsorber system. It can be dispensed with the rotatable mounting of the adsorber 6. As in the second embodiment, a plasma generator 12 is also connected upstream of the multi-flow adsorber system, in order in turn to generate oxidizing agents in the form of ozone and / or oxygen-containing radicals in a second air stream 13. However, the two air streams 1 and 13 are not introduced into the adsorber 6 at the same time, but are timed, alternately one after the other. This means that, for example, the air stream 1 to be cleaned is first introduced into the adsorber 6 via the inlet cross-sectional area 10, the adsorber 6 adsorbing the oxidizable substances contained in the air stream 1 to be cleaned. Subsequently, an introduction of the air stream 1 to be cleaned is prevented, for example, via a valve (not shown), and the second air stream 13 loaded with oxidizing agents is fed through the identical inlet cross-sectional area 10 for regeneration purposes Adsorbers 6 introduced. In this case, the regeneration again takes place by oxidative degradation of the substances adsorbed in the adsorber. The inflow of the air flow 13 into the adsorber 6 is then interrupted, so that the air flow 1 to be cleaned again flows through the adsorber 6. This alternating admission of the first and second air stream is repeated in the desired manner. Thus, at the outlet of the adsorber, the cleaned air stream 1 or the air stream 13 loaded with partially oxidized organic pollutants and residual ozone can be removed via a suitable valve control (not shown).

According to a further alternative, the embodiments described with reference to FIG. 2 can be used in a modified manner, the plasma generator being integrated with the adsorber 6 in an arrangement analogous to the embodiment according to FIG. 1. Of course, it must be ensured in rotating operation that a plasma for generating the oxidizing agent is present in the cross-sectional area of the adsorber, and the second stream of air flows through it just for regeneration purposes. This can be implemented by a suitable control circuit.

Finally, it should be noted that the air streams can be directed to a destroyer 15 after flowing through the adsorbent in order to break down any residual proportions of non-oxidized organic pollutants and / or residual ozone. The excess ozone or partially oxidized organic pollutants are converted catalytically to molecular oxygen at room temperature. In FIG. 2, the annihilation means 15 is connected downstream of the rotary adsorber 6 and the second air stream 13 is passed on to the adsorber 6 after flowing through it. Furthermore it is e.g. With this rotary adsorber it is possible to flush a sub-segment with ozone.

Claims

claims

1. Device for removing oxidizable substances from an air flow, in particular from the cabin air in aircraft, comprising a

Adsorber means (5; 6) for adsorbing oxidizable substances from an air stream (1) to be cleaned, characterized in that a means (3a, 3b, 4; 12) is provided for generating oxidizing agents, the oxidizing agents for regeneration of the adsorbent (5 ; 6) act on the substances adsorbed by the adsorbent (5; 6) and decompose them oxidatively, the resulting reaction products having a reduced adsorption capacity, so that they can be removed from the adsorbent (5; 6).

2. Device according to claim 1, characterized in that the oxidizable substances are gaseous organic and / or organic particles.

3. Device according to claim 1 or 2, characterized in that the oxidizing agents are ozone and / or oxygen-containing radicals.

4. Device according to one of claims 1 to 3, characterized in that the means (3a, 3b, 4; 12) for generating oxidizing agents is a plasma generator which generates the oxidizing agents via a dielectric barrier discharge.

5. Device according to one of claims 1 to 4, characterized in that the means for generating the oxidizing agent consists of an electrode system (3a, 3b) with intervening barriers (4), wherein also the adsorber means (5) in the arrangement of electrodes (3a, 3b) and barriers (4) is integrated.

6. The device according to claim 5, characterized in that the

Adsorber means (5) each surround an electrode (3a or 3b) with a barrier (4) in a sandwich-like manner.

7. Device according to one of claims 1 to 4, characterized in that

- The air flow to be cleaned represents a first air flow (1) which flows through a rotatably mounted adsorber (6);

- The means (12) for generating the oxidizing agent is connected upstream of the rotating adsorbent (6) and generates the oxidizing agent in a second air stream (13);

- The second air stream (13) via an inlet (11) can be introduced into the adsorbent (6) in such a way that the second air stream (13) flows through the adsorbent (6) spatially separated from the first air stream (1), due to the rotational movement of the Adsorber (6), the second air flow (13) flows through a different cross-sectional area (Qj) of the adsorbent (6) for regeneration purposes.

8. The device according to claim 7, characterized in that the axis of rotation (9) of the adsorbent (6) in its longitudinal direction (A).

9. The device according to claim 7 or 8, characterized in that the adsorber (6) has a plurality of channels (7) which are arranged in the longitudinal direction (A) of the adsorber (6) so that the air flows

(1, 13) flow through the adsorber (6) along the channels (7).

10. The device according to claim 7, characterized in that the inlet (1 1) sealing lips (14) which slide on rotation of the adsorber (6) on the inlet cross-sectional area (10) of the adsorber (6), so that a airtight introduction of the second air stream (13) into the adsorbent (6) is ensured.

11.The device according to claim 10, characterized in that the inlet (11) is sector-shaped.

12. Device according to one of claims 1 to 4, characterized in that

- The means (12) for generating the oxidizing agent is connected upstream of the adsorber means (6) and generates the oxidizing agent in a second air stream (13); in which

- The first and second air streams (1, 13) are timed, alternately flow through the adsorbent (6) so that adsorption and regeneration take place sequentially.

13. The apparatus according to claim 12, characterized in that the

Adsorber means (6) has a plurality of channels (7), which are arranged running in the longitudinal direction (A) of the adsorber means (6), so that the air currents (1, 13) flow through the adsorber means (6) along the channels (7).

14. The apparatus according to claim 12, characterized in that the first and second air flow (1, 13) can be introduced into the adsorbent (6) via the same inlet cross-sectional area (10).

15. Device according to one of claims 1 to 14, characterized in that the adsorbent (5; 6) is followed by a destroyer (15) to the remaining in the air streams (1; 13) after flowing through the adsorbent (6) to remove oxidizing agents by catalytic conversion.

16. A method for removing oxidizable substances from an air stream, in particular from the cabin air in aircraft, the oxidizable substances contained in an air stream to be cleaned (1) being adsorbed by an adsorbent (5; 6), characterized by - producing oxidizing agents;

- Regeneration of the adsorbent (5; 6) by the action of the oxidizing agent on the substances adsorbed by the adsorbent (5; 6) and oxidative degradation of these substances, reaction products being formed which have a reduced adsorption capacity; and - removing the reaction products from the adsorbent (5; 6).

17. The method according to claim 16, characterized in that gaseous organic substances and / or organic particles from the air stream to be cleaned (1) are adsorbed by the adsorber (5; 6).

18. The method according to claim 16 or 17, characterized in that ozone and / or oxygen-containing radicals are used as the oxidizing agent, which are generated via a dielectric barrier discharge.

19. The method according to any one of claims 16 to 18, characterized in that the reaction products with the air stream to be cleaned (1) are removed from the adsorbent (5).

20. The method according to any one of claims 16 to 18, characterized in that

- The first air stream (1) to be cleaned is passed through a rotating adsorber (6);

- The oxidizing agents are generated in a second air stream (13);

- The second air stream (13) is introduced into the rotating adsorbent (6) such that the first and second air stream (1, 13) the adsorbent

(6) flow spatially separated from each other, so that due to the Rotation of the adsorber (6) each has a different cross-sectional area (Qi) of the adsorber (6) through which the second air stream (13) flows for regeneration purposes.

21. The method according to claim 20, characterized in that the first and second air stream (1, 13) flow through the adsorber (6) along channels (7) formed therein in the longitudinal direction (A).

22. The method according to any one of claims 16 to 18, characterized in that

- The first air stream (1) to be cleaned is passed through a rotating or stationary adsorber (6);

- The oxidizing agents are generated in a second air stream (13) which is introduced into the adsorbent (6); where - the first and second air flow is timed, alternating in the

Adsorber means () are introduced so that adsorption and regeneration of the adsorber means (6) take place successively in time.

23. The method according to claim 22, characterized in that the first and second air stream (1, 13) each have the same cross section of the adsorbent

Flow through (6).

24. The method according to any one of claims 16 to 23, characterized in that the air streams (1; 13) after flowing through the adsorber (5; 6) are directed to a destroyer (15), so that in the air streams

(1; 13) residual amount of oxidizing agents is removed via catalytic degradation.