DE202004021193U1 - Filter for air conditioning applications uses fibre fleece coated with a layer of activated carbon of controlled particle size - Google Patents

Abstract

Air filter, for air conditioning applications, comprises a fibre fleece e.g approximately 43g/m2> polyester, which is coated with a layer of 100-500 g/m2> activated carbon of controlled particle size, with 20% of particles not exceeding 0.180 mm. Filter material may have corrugated or pleated format. An independent claim is included for a combination particulates removal and adsorption filter.

Description

technical area

The The invention relates to an adsorption filter with at least one Layer of activated carbon particles.

State of technology

In many systems, especially in motor vehicle air conditioning systems, today so-called combination filters are used. These are particle filters for particle separation with a downstream activated carbon layer for the adsorption of gases. The activated carbon layer consists in this case usually of granular carbon, which may be bonded to a carrier, for example made of nonwoven fabric. The particle sizes and amounts of coal used represent a compromise between adsorption capacity, breakthrough characteristics and air permeability. The particle sizes of the activated carbon particles used are usually in the range 20 × 60 mesh (mesh size according to ASTM Designation D 2862-97). This corresponds to particle sizes between 0.25 mm and 0.85 mm. Usual application rates of activated carbon per unit area are between 250-500 g / m ² .

Out There are many proposals in the art for improving breakthrough performance an adsorption filter known. Usually this is to filter assemblies, where a conventional adsorption filter with grain or ball coal around a filter area with high spontaneous adsorption added becomes.

For example, from the DE 197 08 692 an adsorption filter is known, which is divided to improve the breakdown behavior while maintaining the highest possible air permeability and the highest possible adsorption capacity in two filter areas. The first filter area is to absorb up to 99% of the pollutants and thus have a high capacity. The second area should have a low capacity but a high adsorption rate. For the first range, the use of granular or spherical activated carbon (particle size about 0.3-1.0 mm, total carbon amount: about 400-500 g / m ² ) as adsorbent is proposed in the document, for the second region preferably textile fabrics of activated carbon.

With the well-known filter should have a very good breakdown characteristic be achievable. A disadvantage of this and the others, in the literature However, the proposed filters are usually very complex and elaborate Construction, resulting in both the material and the manufacturing costs reflected.

presentation the invention

task The invention is an adsorption filter of the aforementioned To develop the art so that it is as simple and inexpensive as possible Build one opposite the conventional one Filter has significantly improved breakdown characteristics.

These Task is solved with an adsorption filter having the features of patent claim 1. Advantageous embodiments of the invention are described in the subclaims.

According to the invention, in the case of an adsorption filter comprising at least one layer of activated carbon particles, at least 20% by weight of the activated carbon particles have a particle size of less than 0.180 mm and the total weight per unit area of activated carbon is between 100 and 500 g / m ² .

The adsorption filter according to the invention has a very good breakdown characteristic. By using smaller particle sizes, the adsorption rate could be significantly increased. With the reduction of the particle size is usually accompanied by an undesirable reduction in the air permeability of the filter medium. This is counteracted according to the invention in that the amount of activated carbon used can be reduced far below the quantities usually used at the expense of the adsorption capacity. Contrary to the opinion prevailing in the prior art that a high-performance adsorption filter in addition to a good adsorption must also have the highest possible adsorption capacity, which is why, for example, from the above-mentioned DE 197 08 692 C2 Known high-performance adsorption has both a high adsorption speed range and a high-carbon content range and thus high adsorption capacity, the inventors have realized that the height of the achievable adsorption capacity for the function of a filter is not important, which was suspected.

In particular, the inventors have recognized that the harmful gas pollutants occurring in road traffic usually occur only as short-term concentration peaks that can be very well eliminated by a fast-reacting adsorption filter with high spontaneous adsorption, wherein the adsorption capacity plays only a minor role. Furthermore, in the context of endurance tests and subjective performance assessments (DIN 10950: "sensory training" and DIN 13725: "olfactometry") of combination filters with conventional adsorption filters, it has been shown that the level of adsorption capacity according to DIN 71460/2 is not a measure of the fil term or the subjective odor control property of combination filters.

Finally, it has been recognized according to the invention that even an increase in the proportion of activated carbon particles to 20% by weight, which are smaller than 0.180 mm, leads to a significant improvement in spontaneous adsorption. According to the invention, the total weight per unit area of activated carbon is between 100 and 500 g / m ² . These values represent a compromise between a good air permeability of the filter medium and a sufficient adsorption capacity. If the total weight per unit area of activated carbon falls below 100 g / m ² , the contact probability of the molecules to be adsorbed with the activated carbon is too low. As a result, the adsorption performance of the filter deteriorates and the effect of channeling may occur. If, however, the upper limit of 500 g / m ^{2 is} exceeded, the air permeability of the filter medium deteriorates too much.

Of the Essence of the invention lies in the appropriate choice of the mixture of Application amount of fines and coarse fraction of activated carbon such, that a high adsorption speed with the best possible air permeability and filter effect is feasible. In that regard, the invention includes also adsorption filters, which comprise a mixture of activated carbon particles, wherein the mixture comprises coarse and fine fractions, the mixing ratios of rough shares and fine shares as well as the total amount of Activated carbon particles are chosen such that realizes the filter properties of the adsorption filter according to the invention are.

In a preferred embodiment of the invention have at least 30% by weight, more preferably more than 50% by weight of the activated carbon particles have a particle size smaller as 0.180 mm. This will further increase the adsorption rate elevated, On the other hand, the air permeability is still good enough.

Very good values in terms of air permeability are still achieved with a total weight per unit area of activated carbon of 250 g / m ² . Particularly good results in terms of the breakdown characteristic, the air permeability and the adsorption capacity are achieved with a total surface weight of activated carbon between 150 and 230 g / m ² .

Preferably are the activated carbon particles to a carrier material made of nonwoven fabric bound or involved in such. The techniques for this are known and described many times in the patent literature.

Of the Adsorption filter could in particular in a combination filter of the type mentioned use find which particle-filtering area, for example a particle filter made of nonwoven fabric, the electrostatically charged can be, and includes a pollutant adsorbing area.

Of the Adsorption filter can also be used in combination with several particulate filters and / or other adsorption filters, for example, each may be directed to specific pollutants and different adsorbents can have be used. The activated carbon particles and / or in combination Adsorbents used with the adsorption filter can be used in in a manner known per se, partially or in total acid, catalytically or basic be.

Of the Adsorption filter can be the same geometry as conventional Filter have, for example as a plate filter or zig-zag filter be educated.

Conceivable is also that the adsorption filter designed as a filter cartridge is. This configuration allows a compact arrangement of the filter in a suitable housing.

Of the Adsorption filter could be designed as a respiratory protection filter. This embodiment allows a Use in facilities that use substances harmful to the lungs.

The adsorption filter could be used, for example, as part of a combination filter, in particular in automatic motor vehicle (motor vehicle) air conditioning systems. Such air conditioning systems are increasingly characterized by the fact that at high pollutant gas pollution or - concentrations the circuit on recirculation mode, in which the air supply is stopped from the outside and instead the air is pumped in the car interiors, automatically done. For this purpose, noxious gas sensors are provided in the air inlet, which measure the noxious gas pollution or concentration of the intake air (especially hydrocarbons and nitrogen oxides) and give a signal to the control of the air conditioning to close the so-called recirculation damper. This prevents the entry of high pollutant gas concentrations from the outside air into the passenger compartment. The problem here is that from the time of exceeding the noxious gas concentration in the intake and the associated signal output of the noxious gas sensor to the complete closing of the recirculation damper passes a period of several seconds and in this time the noxious gas in high concentration in the air conditioner and thus by the combination filter is directed. The risk of the passage of harmful gases through the filter is great. It has been found that the adsorption filter according to the invention has such a high spontaneous adsorption performance that even at high levels of damage Gas concentrations a breakthrough of noxious gases in the vehicle interior during the system-related recirculation damper closing time of a few seconds is largely prevented. This effect makes it possible, when using the filter in question, to considerably simplify recirculating-air flap systems, thereby slowing down their closing behavior. This can save considerable costs. On the other hand, the adsorption capacity of the adsorption filter according to the invention is sufficient in order to adsorb the noxious gases flowing through at low harmful gas load, which does not yet result in a response of the noxious gas sensor.

sensors work partially selective and do not capture all molecules smells and noxious gases are inherent. The adsorption filter could however even if the sensor is not activated, all molecules passing through it will adsorb and thereby ensure that no undesirable noxious gases occur can.

It can also measures provided for desorbing the pollutants from the adsorption filter be like B. heating the filter, for example by flowing with hot Air, or increased flow of the Filters, with the outflowing, air laden with the noxious gases during the desorption process via a Bypass line must be passed to the vehicle interior.

Of the Adsorption filter also brings in conjunction with a manual activity the recirculation flap advantages.

Especially in connection with the possibility the switchover to recirculation mode at pollutant loads points the adsorption filter according to the invention despite lower metrological (according to DIN 71460/2) detectable adsorption capacity, as in practice at high pollutant gas pollution of the outside air the filter by closing the Recirculation damper is "protected" and thus the Adsorber material is not polluted with noxious gases, the same Filter life as the known filter on. In recirculation mode the adsorption filter can either be on the supply side of the Recirculation damper and are therefore not closed recirculation damper more of the outside air flows through or else can be downstream to the recirculation damper and in recirculation mode only from the Vehicle interior air flows through become. In contrast to the known filters is in the adsorption filter according to the invention the benefit, namely the subjective odor reduction, significantly improved.

Also if the properties and advantages of the adsorption filter according to the invention described above in the context of automotive applications, so is the adsorption filter according to the invention by no means limited to these applications. He can in any Filter systems, for example, in air conditioners for air conditioning of spaces used in real estate or in mobile air purification systems become.

following the invention is based on embodiments and the drawings explained in more detail.

Brief description of the drawing

In the drawing shows the only one

FIG. a diagram showing a standard filter with kinetically optimized Comparing filters for n-butane breakthrough measurements.

Execution of the invention

EXAMPLES

It was used on three combi filters with adsorption filters with different Quantities of activated carbon and n-butane breakthrough on a commercially available standard combination filter certainly. The filters were known per se with fold filters zig-zag folded filter medium, which is surrounded by a frame formed. All Filters were made of nonwoven fabric.

The production of a filter is subject to fluctuations. It should be noted that the actual application rate of activated carbon may differ by 20 g / m ² from the target quantity. The proportion of activated carbon particles whose size is below a certain particle size can deviate by 10% from the nominal quantity.

The Measurements were made after the for Car interior filter valid Standard DIN 71460-2 for carried out the adsorption of gases.

The structure of the filters in detail was as follows:
The combination filters had a single-layer polypropylene (PP) particle filter. The basis weight of the particulate filter was 60 g / m ² , the filter material was electrostatically charged. The fiber diameter was 20-40 microns.

The chemical filter area comprised a polyester carrier material (PES) with a basis weight of about 43 g / m ² and a fiber diameter of about 10 to 25 μm. This was loaded with granular activated carbon. The basis weights were 150, 200 and 250 g / m ² . The particle sizes were 0.106 to 0.425 mm. At this particle size distribution more than 40% by weight of the particles are smaller than 0,180 mm.

The standard combination filter used for comparison had a 1-layer particle filter with a filter layer of polypropylene (PP) with electrostatic charge, a basis weight of 60 g / m ² and a fiber diameter of about 30 μm.

The chemical filter section comprised granular activated carbon (0.25-0.6 mm) with a basis weight of 350 g / m ² . This was applied to a carrier made of PES with a basis weight of about 50g / m ² . The particle size was 0.25 to 0.6 mm. With this particle size, only about 1% by weight of the particles are smaller than 0.180 mm.

The Result of the measurements is shown in the only Fig. The drawing.

The graph of FIG. 1 represents measurements taken in n-butane breakthrough measurements using four different filters. The experiments were run with air at 23 ° Celsius and 50% relative humidity. The throughput was 180 m ³ / h. The air was loaded with 80 ppm of n-butane.

you recognizes in the diagram of Fig. That in the standard combi filter an immediate breakthrough in the order of magnitude of about 7%. This can be done by increasing the Total amount of activated carbon, although slightly reduced, but not completely eliminated because of the increasing pressure loss, the amount of activated carbon not increased arbitrarily can be.

In the case of the combined filters discussed here, the instantaneous breakdown is much lower depending on the amount of activated carbon, namely 2 and 3 with an activated charcoal quantity of 150 and 200 g / m ² and even reaches the value 0 at 250 g / m ² . Furthermore, it is striking that the increase in the breakdown in the standard filters is much steeper than in the adsorption filters in question here. After a maximum period of 10 seconds assumed for closing a recirculation flap, the value for the n-butane breakthrough for the standard filter is already relatively high at 17%, for the filters with 150, 200 and 250 g / m ² activated carbon at only 10%. , 5% and 3.5% significantly lower.

Claims (6)

Adsorption with at least one layer of activated carbon particles, characterized in that at least 20% of the activated carbon particles have a particle size of less than 0.180 mm and the total weight per unit area of activated carbon between 100 and 500 g / m ² . Adsorption filter according to claim 1, characterized that at least 30% of the activated carbon particles have a particle size of less than 0.180 mm Adsorption filter according to claim 1 or 2, characterized in that the total weight per unit area of activated carbon is between 150 and 230 g / m ² . Adsorption filter according to one of claims 1 to 3, characterized in that the carrier material for the activated carbon Nonwoven fabric includes. Combination filter comprising an adsorption filter according to one of the claims 1 to 4. Combination filter according to claim 5, characterized in that that the material for the particle-filtering portion of the combination filter comprises non-woven fabric.