EP0714497B1 - Use of a hydrophobic filter in a process for removing and oxidising organic components from kitchen fumes - Google Patents

Description

The invention relates to the use of a hydrophobic filter separated from the heated catalyst in a process for removing and oxidizing organic components of kitchen fumes from an exhaust air stream by passing the Exhaust air flow through a filter so that the organic components of the Filters are adsorbed, and then desorbing the filter by applying heat outside the adsorption phase, the desorbed components the kitchen vapors are catalytically converted using a heated catalyst become.

Kitchen vapors and, in the broader sense, also include those during production and preparation of food and dishes, for example by bakeries or chocolate manufacturers, resulting vapors, mostly contain organic Components depending on their concentration and the location of the Emission source to an odor nuisance in the area as well other undesirable phenomena, such as deposits and the they can lead to the formation of mold.

For this reason, efforts are made to keep the steam as close as possible to the point of origin intercept, preferably suction, and the one loaded with the fumes Exhaust air for cleaning the organic components, among other things To direct filters. However, the absorption capacity of each filter is limited, what affects its effectiveness when saturation is reached or even picks up. Replacing the filter involves labor and costs as well possibly associated with disposal problems.

The device known from DE-A-23 63 820 has an assembly of one Filters and a heated catalyst through which the organic Components contaminated exhaust air is passed through after pre-filtering, the organic components alternately adsorbed by the filter and desorbed by the application of heat and afterburned catalytically. The disadvantage this device is that the filter has to be desorbed frequently, preferably after each suction process. Given a high percentage of The filter is despite water vapor and water droplets in kitchen vapors of an upstream grease filter is no longer receptive after a short time. In addition comes that desorbing water because of the high specific heat and heat of vaporization of water a high energy expenditure for the Heating of the filter and the catalyst is required. To be effective catalysts generally have a large specific surface area, which in addition to transferring energy to the exhaust air flowing through it, in particular with exhaust air mixed with water vapor. Are correspondingly high the energy expenditure and the associated costs to the catalyst keep at operating temperature during catalysis. Comes on added that the generally in the air flow only in relatively low concentration present organic components because of the high air volume flow accompanying them only insignificant for the heating of the catalyst due to its exothermic can contribute to catalytic oxidation.

The invention is therefore based on the object, the method of the aforementioned Kind to design and develop in such a way that the energy expenditure for the desorbing and catalytic conversion of the adsorbed components Kitchen fumes is reduced. This task is characterized by the characteristics of the solved only claim.

According to the invention, a hydrophobic filter is used. That has the advantage, that the organic components of the kitchen vapors are selectively adsorbed, but not the water vapor or water droplets contained in the kitchen vapors, so that the filter of the water, which it does not even adsorb, also does not have to be freed again.

The filter is regenerated by supplying heat and the catalyst is only timed limited and therefore energy-saving for the catalytic oxidation of the organic Heated components. This is possible because the organic components of the kitchen vapor is not constantly subjected to catalysis, but initially adsorbed by the filter and cached and from time to time Time to be reacted on the heated catalyst, including the organic components desorbed from the filter - if it is in front of the catalytic converter - by heating become.

The desorption phase is carried out at the latest when the filter with organic Components is saturated. The catalytic oxidation of the organic Components then also take place, preferably when the kitchen operation is stopped is, for example at night.

The catalytic oxidation of those previously adsorbed and enriched in the filter organic constituents clearly increases through the more concentrated implementation less time and energy than that required as in the state of the art Technology must also desorb a significant amount of adsorbed water.

There are two ways of carrying out or embodying the invention. With both options, those that are transported in with the exhaust air flow are brought up organic components first adsorbed on a filter. This filter consists preferably of zeolitic material. Zeolites exhibit because of their specific chemical and physical properties in a wide range A particularly high range can be modified in their manufacture Adsorption capacity, especially for gaseous substances. When filtering For air vents that contain kitchen vapors, zeolites are suitable that are hydrophobic Have properties and therefore selectively the organic components of kitchen fumes adsorb, but not adherent to kitchen fumes Steam. Zeolites can be in the form of a powder bed, a bed of granules or a monolithic body. Preferably be Granulate fillings are used because they are better than the powder bed Have flowability and cheaper compared to the monolithic body are to be produced. A special property of zeolites is their reversible adsorption capacity, i.e. she give the previously adsorbed organic components when the temperature rises again. The desorption temperature depends on the one hand on the characteristic Properties of the zeolite, especially its optionally modified surface properties and the nature of the adsorbed organic components yourself. Suitable desorption temperatures are in the range of 150 ° C to 300 ° C, being a higher temperature leads to an advantageous high desorption rate, however the upper limit of the desorption temperature to avoid unwanted carburizing, what the regeneration ability of the zeolite and would affect the filter. Zeolites or filters, as described above, when heat is applied desorb the organic components again hereinafter referred to as "desorbing zeolites" or "desorbing Filter ".

The use of zeolites has compared to that in kitchens otherwise used, hardly desorbable adsorption filter the advantage of activated carbon or nonwoven mats, to be thermally more resilient.

One way to modify the specific Properties of the zeolite is that Surface of the zeolites with, among other things, catalytic effective and the organic components with the addition of oxygen to provide oxidizing substances, in particular with precious metal salts. The catalytic effect of the zeolite and thus of the filter Heat supply activated. The organic Ingredients without desorbing in the presence catalytically oxidized by oxygen. The one before adsorbing zeolite is expediently at Temperatures from 200 ° C to 900 ° C operated as a catalyst. Preferably in the range of 200 ° C to 450 ° C. Filters and zeolites that are the previously absorbed organic Components with the application of heat catalytically oxidize, are further referred to as "oxidizing zeolites" or "oxidizing filter" called.

The filter can be heated in a number of ways. The filter can be directly, in particular by means of be heated by an electric heating device. The filter can also be designed as a heat exchanger be, for example, according to the cross-flow principle, any waste heat to heat the filter to be able to use. The filter can be heated indirectly by giving him, for example, a heater is connected upstream, which heats the exhaust air flow, before entering the filter. The heater can, for example, in turn be operated electrically or as a heat exchanger be designed.

The inventive method can be carried out as a filter a "desorbable filter", in particular a zeolite, is used and the catalytic Oxidation in a separate but fluidically connected and heated catalyst is carried out. Here are the conditions for the catalytic oxidation of the organic components the same as for the oxidizing filter. In another embodiment of the method according to the invention the filter is also a catalyst, as was the case with the "oxidizing zeolite" described. This reduces the number of components and the device to carry out the method can be made more compact overall become. The advantage of a catalyst separated from the "desorbing filter", is that the catalyst, for example, several filters during which Desorption phases can be assigned simultaneously or at different times. This would be particularly true for canteen kitchens or large systems with several extraction points beneficial for organically contaminated vapors. In addition, one of the Filter separate catalyst can be arranged in a branch line, which in the Adsorption phase is not flowed through, so that the catalyst in the adsorption phase is not burdened, especially not with water vapor.

The catalyst downstream of the desorbing filter can be heated are heated directly or indirectly, the type of heating preferably is electrical.

Heaters of a "desorbing filter" and a downstream catalyst as well as an "oxidizing filter" can be assigned by them Switching devices regardless of the assigned and the exhaust air flow generating fan are switched so that when they reach the Saturation of the filter or can be operated earlier if required. The heaters of the "desorbing filter" and the downstream catalyst also be designed as a common heating device or a common one Have switching device because the desorption and the catalytic oxidation in the catalyst downstream of the filter takes place almost simultaneously. By certain circuitry precautions can be ensured that the Catalyst is heated to its operating temperature immediately before the Filter is heated and the desorption is started.

To avoid the catalyst in the not heated state during the adsorption phase Condensation is occupied, this is only in the heated State, preferably only in the desorption phase, the suspend the exhaust air flow leaving the filter. This is advantageously realized in that the catalyst is bypassed and shut-off devices in the bypass and / or through the bypass section of the exhaust air duct are provided with the catalyst and for example are designed as controllable valves.

The in the gaseous carrier medium after the catalytic Oxidation of the organic components stored Heat can at least partially desorb or fed to catalysis. This can happen, for example, in such a way that the heated one Exhaust air if necessary as a cross-flow heat exchanger designed filter or a heat exchanger that is upstream of the filter and the supplied to the filter Exhaust air should be heated, is supplied. It is also possible that part of the catalyst escaping and heated exhaust air in the filter entering, colder exhaust air is added to to heat them, but with a minimum oxygen content not in the exhaust air supplied to the filter may fall below, otherwise the following catalytic oxidation is incomplete.

Figur 1

zeigt die Blockdarstellung einer Vorrichtung zum Entfernen und Oxidieren organischer Bestandteile 1 von Küchendünsten in der Phase der Adsorption,

Figur 2

zeigt die Blockdarstellung der Vorrichtung aus Figur 1 in der Phase der Desorption und Katalyse, und

Figur 3

zeigt die Blockdarstellung der Vorrichtung aus Figur 1 am Schluß der Desorptionsphase.

An embodiment of the invention is shown schematically in the accompanying drawings.

Figure 1

shows the block diagram of a device for removing and oxidizing organic constituents 1 from kitchen fumes in the adsorption phase,

Figure 2

shows the block diagram of the device of Figure 1 in the phase of desorption and catalysis, and

Figure 3

shows the block diagram of the device of Figure 1 at the end of the desorption phase.

The device consists of a hydrophobic filter 2, a catalyst 3 and a fan 4 which generates an exhaust air flow 5, the filter 2, the catalyst 3 and the fan 4 being arranged downstream in terms of flow and connected via the exhaust air duct. The exhaust air duct 6 branches in front of the catalytic converter 3 into a bypass 7, which bridges the catalytic converter 3 and opens again into the exhaust air duct 6 in front of the fan 4. A first controllable shut-off device 8 is arranged in the bypass 7. In the part of the exhaust air duct 6 bridged by the bypass 7, a second controllable shut-off device 9 is provided in front of the catalytic converter 3. A heating device 10 or 11 is integrated in the filter 2 or the catalytic converter 3 and can be switched independently of one another and independently of the fan 4. In the adsorption phase (FIG. 1), the shut-off device 8 is open and the shut-off device 9 is closed, so that the exhaust air stream 5 is directed past the catalyst 3. The heating devices 10 and 11 are switched off and the filter 2 and the catalyst 3 are at a low temperature T ₀ , where T _{0 is} less than 100 ° C. The organic constituents 1 located in the exhaust air stream 5 adsorb in the filter 2. The exhaust air purified in this way is drawn off via the bypass. At the end of the adsorption phase, ie when the filter 2 is saturated, or if required, the catalyst 3 is heated to its operating temperature T ₂ (for example 350 ° C.) by means of the second electrical heating device 11. As soon as it reaches this temperature, the second shut-off device 9 is opened and then the first shut-off device 8 is closed. The first heating device 10 then brings the filter 2 to its desorption temperature T ₁ (for example 200 ° C.). The organic constituents 1 released from the filter during the desorption phase (FIG. 2) are transported to the catalytic converter 3 by means of the exhaust air flow 5 via the exhaust air duct 6. There, the desorbed organic constituents 1 are directly catalytically oxidized before they leave the device via the fan 4.

After the organic components enriched in the filter 2 have been completely desorbed (FIG. 3), the first heating device 10 and the second heating device 11 are switched off again, the first shut-off device 8 is opened again and the second shut-off device 9 is closed again. The filter 2 is now in a regenerated form and, after cooling to T _{0, can} again adsorb new organic constituents 1 from the exhaust air stream 5.

Claims (1)

1. Use of a hydrophobic filter (2), which is separated from the heated catalyst (3), in a process for removing and oxidising organic components (1) of kitchen fumes from an extracted air stream (5) by passing the extracted air stream (5) through the filter (2), so that the organic components (1) are absorbed by the filter (2), and subsequently out of the adsorption phase desorbing them from the filter (2) by heat input and catalytically converting the desorbed components (1) of the kitchen fumes by a heated catalyst (3).

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