EP2437895B2 - Recirculating-air spray booth - Google Patents

Description

The invention relates to a circulating air spray booth with a work area for coating workpieces, with an extraction zone from which pollutant-containing, in particular solvent-containing, exhaust air is extracted, and with a fan for air circulation, the exhaust air from the spray booth in circulating air operation in the working area at least partially via at least one filter unit can be supplied again as recycled air.

Such spray booths are known as circulating air booths. In the context of this application, the term “coating” is preferably understood to mean spray painting.

While the recycling of exhaust air can be highly effective in removing dust and foreign particles using high-quality separation systems or filter devices, the solvent concentration (measured in g / m ³ ) increases over time. The concentration of the solvents should, however, not exceed 5 g / m ³ because of explosion safety.

As long as the spray booth is operated automatically, the increase in the solvent concentration due to the recirculation mode does not play a special role as long as the permissible limit values are not exceeded. However, if the spray booth has to be entered by a worker, the maximum solvent concentration of 5 g / m ³ permitted for exhaust air is too high, especially when large spray booths are involved, such as those used in the automotive industry. If the spraying operation is interrupted, the solvent concentration will, however, only decrease very slowly. It usually takes about 30 to 60 minutes to lower the solvent concentration, starting from, for example, a maximum permissible value of 5.0 g / m ³ to an acceptable value of, for example, 0.01 g / m ³ .

For this reason, spray booths that work in recirculation mode have so far only been able to establish themselves in special cases. In particular, when it comes to large spray booths, such as those commonly used in the automotive industry, there are practically no circulating air spray booths.

From the U.S. 4,537,120 A a spray booth according to the preamble of claim 1 is known, which is divided into several zones, in a central working area in which a higher air flow rate is required because of the spray application, and in a side area in which a lower air flow rate is required. The spray booth can at least partially be operated in recirculation mode, which means that part of the less polluted air from the side area is processed again and fed as additional air into the application area in order to increase the air throughput here. The air throughput of recycled air and fresh air can be designed variably and controlled automatically.

However, this is not a circulating air spray booth in the actual sense, since the spray booth is used manually by a worker, which is why sufficient supply air must be provided in the worker's work area.

From the DE 33 34 257 A a circulating air spray booth according to the preamble of claim 1 is known, in which a switch is provided between a circulating air mode for painting and a quick venting mode for quick venting when the spray booth is to be entered. If you want to enter the spray booth, you can switch to quick ventilation mode. The air circulation mode is then ended and a vent is opened so that the solvent concentration inside the spray booth drops to a level that is permissible for entry.

Against this background, the invention is based on the object of creating a circulating air spray booth which, when the spraying operation is interrupted, enables the solvent concentration to be rapidly reduced to a permissible value for entering the spray booth. Furthermore, the most energy-saving operation of the spray booth should be ensured.

This object is achieved by a circulating air spray booth according to claim 1.

Since the spray booth can be switched to a quick ventilation mode and in which at least partially non-recycled, preferably filtered, supply air is supplied to the work area, the solvent-containing air present in the work area is exchanged more quickly and the solvent concentration is reduced to permissible values more quickly. A harmless solvent concentration is achieved after a short time after switching to quick exhaust operation, so that a worker can enter the spray booth without additional protective measures such as breathing masks.

According to a further embodiment of the invention, in recirculation mode, part of the exhaust air is fed back into the spray booth via a filter unit as recycled supply air and part of the exhaust air is released to the environment via the roof or an exhaust air purification system.

This results in a constant release of solvent from the recycled supply air and a constant supply of a certain proportion of non-recycled supply air.

According to a further embodiment of the invention, the exhaust air released into the environment is previously treated, preferably washed, filtered and / or thermally post-treated or air-conditioned.

In this way, the prescribed limit values are complied with or a further reduction in the pollutant concentration can be achieved by means of thermal post-treatment (thermal post-combustion).

According to a further embodiment of the invention, the spray booth can gradually be switched between a circulating air mode and a quick ventilation mode or vice versa.

In this way, the associated fans can gradually be brought into the other position will.

For this purpose, at least one controllable fan and one continuously variable air valve are provided. In this context, “air valve” is understood to mean a valve of some kind for regulating air. In the simplest case, this is a variable flap with a servomotor.

The controllable fan usually has a frequency converter for low-loss control.

According to a further embodiment of the invention, the spray booth comprises a conveyor for conveying workpieces through the spray booth via an entrance through the work area and an exit, at least one separate area being provided at the entrance and preferably at the exit of the spray booth, the connections for separate connections from the work area Has supply and exhaust air, each separated area being able to be subjected to an overpressure with respect to the environment.

In this way, entry of dusty air into the spray booth is definitely prevented.

In this case, at least one fan is preferably provided for the work area and at least one fan for each separated area, with non-recycled, filtered air being able to be supplied to the work area in the quick ventilation mode.

In this way, when switching to quick ventilation mode, the work area is also freed of solvents by supplying non-recycled, filtered air. This is particularly important in the case of spray booths with a long design, in order to ensure sufficiently rapid ventilation.

In this case, the air supplied to the work area in quick ventilation mode can be branched off from at least one separated area.

If the air supply continues to run for at least one separated area in quick ventilation mode, rapid ventilation of the work area can be ensured in this way with simple means.

Preferably, only non-recycled, filtered air is fed in, at least in the separated area at the entrance.

However, it is also conceivable that partially recycled, filtered air and partially non-recycled air are supplied in the separated area, in particular at the exit.

In this case, air sucked out of the work area in quick ventilation mode is preferably not recycled, but is discharged as exhaust air.

These measures prevent start-up problems such as vibrations and impacts when starting large fans and the associated risk of contamination.

In a further embodiment of the invention, at least one wet scrubber or suction device is provided, via which e.g. exhaust air is extracted at the bottom. The spray booth is basically constructed in a known manner according to the state of the art, whereby the spray booth can also have several water-flooded trickle walls, which finally open into a common receptacle, through which exhaust air can be sucked off at the bottom, for example a venturi washer or the like can act. Such wet scrubbers or suction devices are preferably provided in each sub-area of the spray booth.

According to a further advantageous embodiment of the invention, the fan for the work area is operated in quick ventilation mode with a reduced output such that an overpressure is maintained in the area of the filter ceiling (plenum).

In this way, dust and foreign matter from the filters are largely avoided.

When switching between recirculation mode and quick ventilation mode, the fan power of the working area is preferably gradually reduced and filtered air that is not recycled is gradually supplied from a separate area.

In this way, start-up problems that exist with large fans and that generally lead to shaking, vibrations and other disturbances can be largely avoided.

Conversely, when switching between quick ventilation mode and circulating air mode, the fan output of the work area is preferably gradually increased and non-recycled, filtered air supplied from a separated area is gradually diverted back into the separated area.

Overall, these measures largely avoid start-up problems with large fans, so that it is possible to significantly reduce the fan power in the work area for quick exhaust operation, while the fan power can be maintained in the separated areas.

The working area is preferably continuously supplied with air via a filter unit, that is to say both during circulating air operation and during quick ventilation operation.

In this way, the filter ceiling (the plenum) is constantly under a certain overpressure, so that no dust detachment and the like occur.

It goes without saying that the features of the invention mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention.

Fig. 1

eine stark vereinfachte Darstellung einer ersten Ausführung einer erfindungsgemäßen Umluftspritzkabine;

Fig. 2

eine abgewandelte Ausführung der Umluftspritzkabine gemäß Fig. 1;

Fig. 3

einen Teilbereich einer weiteren Ausführung einer erfindungsgemäßen Spritzkabine; und

Fig. 4

eine erfindungsgemäße Umluftspritzkabine, die insbesondere bei umfangreichen, besonders hochwertigen Lackierungen verwendet wird, wie etwa im Automobilbau.

Other features and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawing. Show it:

Fig. 1

a greatly simplified representation of a first embodiment of a circulating air spray booth according to the invention;

Fig. 2

a modified version of the air circulation spray booth according to Fig. 1 ;

Fig. 3

a portion of a further embodiment of a spray booth according to the invention; and

Fig. 4

a circulating air spray booth according to the invention, which is used in particular for extensive, particularly high-quality paintwork, such as in automobile construction.

In all Figures 1 to 4 fan outputs are given, which are given here as an example in m ³ / h. In some cases other values are given in brackets. The values without brackets stand for the air flow in recirculation mode, while the values in brackets stand for the air flow in quick exhaust operation.

In Fig. 1 a circulating air spray booth is shown in simplified form and denoted as a whole by the number 10. The circulating air spray booth 10 has a closed housing 12 in which a work area 14 for spray painting workpieces 16 is located. A wet scrubber 18 is provided below a floor 13, through which exhaust air is sucked off on the floor side. In recirculation mode, air is fed in at 90,000 m ³ / h via a fan 22 via one or more filters 24 and fed into the work area 14 from above via a filter ceiling 20 (also known as plenum). A part of the exhaust air sucked off via the wet scrubber 18 is sucked off via a further fan 28 and released to the outside, for example via the roof. This is 10,000 m ³ / h. These 10,000 m ³ / h are additionally sucked in as fresh air in the work area 14 from the installation room or outside the spray booth, as indicated by the arrow 15. As a result, 90% of the extracted exhaust air is recycled in recirculation mode and fed back as recycled, filtered air, while 10% is sucked in as fresh air and 10% is released as exhaust air. If a switch is to be made to a quick venting mode in order to quickly lower the solvent concentration in the spray booth to unproblematic values, the fan 22 is switched off and an air valve 26, via which it is coupled to the wet scrubber 18, is closed. No more circulating air is circulated in the quick ventilation mode while the exhaust fan 28 continues to operate, so that the work area 14 is quickly flooded with 10,000 m ³ / h of fresh air.

In Fig. 2 is a slightly modified version of the spray booth according to Fig. 1 shown and designated as a whole by numeral 10a. In this case, too, the working area 14 is supplied with circulating air via a fan 22 in circulating air mode via a filter 24 and a valve 32. In this case, the fan 22 has an output of 100,000 m ³ / h in recirculation mode. While 90,000 m ³ / h are passed into the working area 14 as recycled, filtered air, 10,000 m ³ / h are fed via a valve 32 to a thermal post-combustion 34, where it is thermally post-burned and finally released into the open. The thermal afterburning can preferably also be a regenerative thermal afterburning RNV. In recirculation mode, 100,000 m ³ / h are extracted from the working area 14 via the wet scrubber 18, while only 90,000 m ³ / h are fed back in as recycled, filtered air via the plenum 20. The remaining 10,000 m ³ / h are additionally sucked into the working area 14 via a filter 36 or via the plenum 20, as shown by the arrow 15. If the spray booth 10a is now to be vented quickly, the blower 22 is reduced in its output to 10,000 m ³ / h and the air valve 32 is closed. Recycled exhaust air is therefore no longer fed into the work area 14. So only exhaust air is released to the outside via the thermal post-combustion 34 and another 10,000 m ³ / h is introduced as fresh air via the filter 36.

In this way, quick ventilation is guaranteed. At the same time, the fan 22 is not shut down completely, but continues to run at 10% of its power. As a result, when switching between recirculation mode and quick ventilation mode, it is not necessary to start up the fan 22. In this way, strong shaking effects, impacts, etc., which occur when the blowers start up, are avoided. In this way, foreign particles, dust, dirt, etc., which could otherwise increasingly occur in the working area 14 when starting up, are largely avoided.

In Fig. 3 Another embodiment of a circulating air spray booth according to the invention is shown and denoted as a whole by number 10b. This is a larger spray booth, such as that used for painting vehicles in the automotive industry. The spray booth 10b has an elongated working area 14, which is only partially shown here, upstream of which an entrance area 38 (separate area at the entrance) is connected. A conveyor 50 runs through the spray booth 10b, by means of which workpieces 16 are moved continuously or cyclically over the input area 38 through the work area 14.

The work area 14 has its own air duct, which is shown here in Fig. 3 is not shown. A fan 40 is provided for the entrance area 38, by means of which fresh air is sucked in from the outside and is fed into the entrance area 38 from above via a filter 42 and a valve 44 via the plenum 20. This is, for example, 50,000 m ³ / h. A part, namely 20,000 m ³ / h, passes through a suction area 52 of the entrance area 38 and is finally released to the environment via a line 48. 25,000 m ³ / h are diverted to work area 14. The remaining 5,000 m ³ / h are released into the environment as "overpressure". The spray booth 10b is therefore completely under excess pressure, so that no dust, foreign particles, etc. can penetrate at the entrance area 38. The air duct in the working area 14 is not shown, to which a fan with a high volume of circulating air belongs, by means of which air recycled in the circulating air mode is supplied again. If the spray booth 10b is now to be switched from recirculation mode to quick ventilation mode, then fan 40 continues to run unchanged at the same output of 50,000 m ³ / h. A reduced air volume of 25,000 m ³ / h is passed into the entrance area 38 via the air valve 44, of which 20,000 m ³ / h reach the suction area 52 and from there into the surroundings via the line 48. Another 5,000 m ³ / h escape to the outside as "overpressure". Of the air flow of 50,000 m ³ / h supplied by the fan 40, the second part of 25,000 m ³ / h is supplied to the work area 14 via a further air valve 46. With the aid of this air flow, effective ventilation of the work area 14 is ensured, so that effective ventilation takes place even with very long work areas 14. In the quick ventilation mode, there is no further diversion of air from the entrance area 38 to the work area 14.

In Fig. 4 is based on the previously based on Fig. 3 The illustrated embodiment now shows a complete version of a spray booth 10c for vehicle painting in the automotive sector. The spray booth 10c has an elongated housing 12, with a work area 14, an entrance area 38 and an exit area 66. Again, workpieces 16 are guided by means of a conveyor 50 through the entrance area 38, the work area 14 and the exit area 66 of the spray booth 10c. The work area 14 as well as the entrance area 38 and the exit area 36 are provided with wet scrubbers or suction devices 18 and 52 and 54, respectively. Filtered air is supplied from above via the plenum 20.

First, the recirculation mode will be explained. A fan 22 with 300,000 m ³ / h is used to supply 250,000 m ³ / h via a valve 32 as recycled, filtered air via the plenum 20 from above into the work area 14. A total of 300,000 m ³ / h are sucked off by means of the blower 22 via a wet scrubber 18, the remaining 50,000 m ³ / h are discharged to the outside via a valve 30 or fed to a thermal post-combustion. A blower 40 is provided at the entrance area 38, by means of which 80,000 m ³ / h are sucked in in recirculation mode and fed into the entrance area 38 via a valve 44 via the plenum 20. 50,000 m ³ / h reach the outside as exhaust air via the suction device 52 and a further fan 28. Another 25,000 m ³ / h are diverted to work area 14. The remaining 5,000 m ³ / h escape to the outside as overpressure at the entrance. A further blower 56 with 80,000 m ³ / h is provided in the exit area 66. These 80,000 m ³ / h are passed through a valve 60 from above via the plenum 20 into the outlet area 66. Of this, 50,000 m ³ / h reach the blower 56 via the suction device 54 and a valve 64. A further 30,000 m ³ / h are drawn in as fresh air via a valve 62 from the outside via the blower 56. A further portion of 25,000 m ³ / h of the air flow of 80,000 m ³ / h supplied via the valve 60 is diverted into the working area 14. The remaining portion of 5,000 m ³ / h escapes to the outside from the exit area 66, so that no ingress of dust and the like is possible here either.

If the spray booth 10c is now switched to quick ventilation mode, the two fans 40, 56 continue to run with the same output of 80,000 m ³ / h. In contrast, the fan 22 is reduced to an output of 50,000 m ³ / h. These 50,000 m ³ / h continue to be discharged to the outside via the valve 30 or passed to thermal post-combustion. The valve 32 is closed so that no more recycled air can get into the working area 14. At the inlet area 38, the valve position of the valve 44 is changed in such a way that only 55,000 m ³ / h reach the inlet area 38 via this valve 44. The remaining portion of 25,000 m ³ / h is fed via a valve 46 into the working area 14 via the plenum 20. The air flow of 55,000 m ³ / h in the entrance area 38 reaches the outside at 50,000 m ³ / h via the suction device 52 and the fan 28 as exhaust air, while 5,000 m ³ / h escape at the entrance as overpressure. In the working area 14, air supplied from the valve 44 is no longer diverted into the working area 14. At the exit area 66, a valve 58 deflects part of the air flow of 80,000 m ³ / h, namely 25,000 m ³ / h, via the plenum 20 from above into the work area 14. The remaining portion of 55,000 m ³ / h is led through the exit area 66, with no more diversion into the work area 14. 50,000 m ³ / h return to the fan 56 via the suction device 54 and the valve 64, while the remaining 5,000 m ³ / h escape as overpressure at the outlet.

At the exit area 66, a part is thus still returned as recycled air in the quick ventilation mode. However, it would easily be conceivable to provide the air duct at the exit area 66 in the same way as at the entrance area 38, so that no recycled air is supplied.

Due to the measures shown, the spray booth 10c is ventilated very quickly when switching to rapid venting mode. At the same time, it is avoided that the fan 56 has to be started up again from zero, so that start-up vibrations etc. that arise as a result are avoided.

Claims (18)

1. Recirculating-air spray booth with a working region (14) for coating workpieces (16), with an extraction zone from which solvent-containing exhaust air is extracted, and with a fan (22) for circulating the air, and with a recirculating-air mode within which at least part of the exhaust air can be resupplied as recycled air to the spray booth (10, 10a, b, c) via at least one filter unit (20, 24), wherein the spray booth (10, 10a, b, c) can be switched over into a further mode of operation, wherein the supply of recycled air is interrupted or reduced and additional air which is at least partially not recycled, can be supplied to the working region (14), wherein the recirculating-air spray booth is configured for working in the recirculating-air mode during the coating of workpieces, and wherein a switching over into the further mode of operation is effected upon interruption of the recirculating-air mode, the further mode of operation being configured as a rapid venting mode for a fast reduction of a solvent concentration to an admissible value which allows access to the spray booth without any additional protective measures, characterized in that the fan (22) for the operating region (14), when being in rapid venting mode, is operated with reduced power.
2. The spray booth of claim 1, wherein a part of the exhaust air from the spray booth (10, 10a, b, c) is resupplied via a filter unit (20, 24) as recycled air, when being in recirculating-air mode, and a part of the exhaust air is released to the surroundings.
3. The spray booth of claim 2, wherein the exhaust air released to the surroundings is treated before, preferably being washed, filtered absorbed and/or thermally finally treated.
4. The spray booth according to any of the preceding claims which can be switched over gradually between a recirculating-air mode and a rapid venting mode.
5. The spray booth according to any of the preceding claims, which comprises at least an adjustable fan (22) and/or an air valve (30, 32, 44, 46, 58, 60) which can be continually adjusted.
6. The spray booth of claim 5, wherein the adjustable fan (22) comprises a frequency converter.
7. The spray booth of any of the preceding claims, with a conveyor (50) for transporting workpieces (16) through the spray booth (10b, c) via an entrance through the working region (14) and an exit, wherein at least a separated region (38, 66) is provided at the entrance and preferably at the exit of the spray booth (10b, c), the exit comprising connections for air supply and exhaust air separated from the working region (14), wherein each separated region (38, 66) can be accessed with a pressure which is higher than the surrounding pressure.
8. The spray booth of claim 7, with at least one fan (22) for the working region (14) and at least one fan (40, 56) for each separate region (38, 66), wherein non-recycled filtered air can be supplied to the working region (14) when being in rapid venting mode.
9. The spray booth of claim 8, wherein in the rapid venting mode the air supplied to the working region (14) is divided from at least one separated region (38, 66).
10. The spray booth of claim 8 or 9, wherein at least the separated region (38) at its entrance can be supplied only with recycled, filtered air.
11. The spray booth of any of claims 8 to 10, wherein which the separated region (66) at its exit can be supplied at least partially with recycled, filtered air, and at least partially with non-recycled air.
12. The spray booth according to any of claims 8 to 11, wherein air aspirated from the working region (14) in the rapid venting mode is not recycled, but output as exhaust air.
13. The spray booth of any of the preceding claims, further comprising at least one wet washer (18, 52, 54), from which exhaust air is aspirated on the bottom side.
14. The spray booth of any of claims 8 to 13, wherein the working region and each separated region (38, 66) comprises a wet washer (52, 54), a suction or a dry separator through which exhaust air is aspirated on the bottom side and/or wall side.
15. The spray booth of any of claims 12 to 13, wherein the fan (22) for the working region (14) is operated in the rapid venting mode at such a reduced power that an overpressure is maintained in the filter ceiling (20).
16. The spray booth of any of claims 8 to 15, wherein during switching between recirculating-air mode and rapid venting mode the fan power of the working region (14) is reduced gradually, and from a separated region (38) non-recycled, filtered air is supplied gradually.
17. The spray booth of any of claims 8 to 16, wherein, when switching between the rapid venting mode and the recirculating-air mode the fan power of the working region (14) is gradually increased, and previously supplied non-recycled, filtered air is gradually diverted again into the separated region (38).
18. The spray booth of any of the preceding claims, with a filter unit for supplying air into the working region, by means of which the working region is supplied with air during recirculating-air mode as well as during rapid venting mode.

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