Apparatus and method for wet cleaning a gas stream

Abstract

An apparatus and method for wet cleaning a gas stream has a housing with a gas inlet and a gas outlet, wherein, in the housing, there is at least a first washing segment that serves to clean the gas stream with a washing liquid and that is arranged in the flow path of the gas stream. Inside the housing of the apparatus, there is at least one fan that regulates air pressure along the flow path of the gas stream. A bypass channel for bypassing the flow path through the at least one washing segment as well as a regulator that is arranged in the bypass and that serves to discharge the gas stream being conveyed via the bypass channel are arranged inside the housing.

Claims

1. A device (10) for wet cleaning a gas stream, comprising: a housing (1) with a gas inlet (2) and a gas outlet (3); at least one washing segment (4) inside the housing (1) configured to clean the gas stream with a washing liquid, said at least one washing segment (4) being arranged in a flow path (15) of the gas stream; at least one fan (6) inside the housing (1) configured to regulate air pressure along the flow path (15) of the gas stream; a bypass channel (7) inside the housing (1) for bypassing the flow path (15) through the at least one washing segment (4); a baffle element (11) inside the housing (1), the baffle element (11) configured to switch over a gas feed between the flow path (15) through the at least one washing segment (4) and a second flow path (16) through the bypass channel (7); and a regulator (8) arranged in the bypass channel (7) and configured to maintain gas pressure and discharge the gas stream being conveyed along the second flow path (16) via the bypass channel (7).

2. The device (10) according to claim 1, characterized in that the regulator (8) is configured as a bypass pump.

3. The device (10) according to claim 1, wherein at least two washing segments (4, 5) are arranged in the flow path (15) of the gas stream in series one after the other.

4. The device (10) according to claim 3, wherein the bypass channel (7) runs substantially below the at least two washing segments (4, 5).

5. The device (10) according to claim 1, characterized in that the baffle element (11), irrespective of its position, is configured to convey the washing liquid from the first washing segment (4) into a collecting tank (12).

6. The device (10) according to claim 3, characterized in that the at least two washing segments (4, 5) are arranged in the housing (1) side by side, with the gas stream (15) flowing in a first direction through a first (4) of the at least two washing segments and flowing in an opposite direction through a second (5) of the at least two washing segments.

7. The device (10) according to claim 3, further comprising at least one liquid separator (17, 18) arranged downstream from the at least two washing segments (4, 5).

8. The device (10) according to claim 7, characterized in that the at least one liquid separator (17, 18) is provided in an area of the deflection (19, 20) of the flow path (15) through the at least two washing segments (4, 5).

9. The device (10) according to claim 3, further comprising a packed column (23, 24) associated with each of the at least two washing segments (4, 5).

10. The device (10) according to claim 3, further comprising detachable connections between a first washing segment (4) and a second washing segment (5) of the at least two washing segments (4,5), so that the device (10) is adapted for breaking apart to form at least two modules.

11. A method for wet cleaning a gas stream, comprising: (i) feeding the gas stream that is to be cleaned into a device (10) for wet cleaning gases, said device (10) having a housing (1) with a gas inlet (2) and a gas outlet (3), at least two washing segments (4, 5) inside the housing (1) configured to clean the gas stream with a washing liquid, said first and second washing segments (4, 5) being arranged in a flow path (15) of the gas stream, at least one fan (6) inside the housing (1) configured to regulate air pressure along the flow path (15) of the gas stream, and a bypass channel (7) inside the housing (1) for bypassing the flow path (15) through the at least two washing segments (4, 5) and a regulator (8), with said regulator (8) being arranged in the bypass channel (7) and configured to maintain gas pressure and discharge the gas stream being conveyed via the bypass channel (7), (ii) selectively switching the gas stream flow path to cause the gas stream to flow either (a) through at least a first washing segment (4) of the at least two washing segments and a second washing segment (5) of the at least two washing segments, to clean the gas stream with at least one aqueous washing liquid, or (b) through the bypass channel (7) for bypassing the flow path (15) through the at least two washing segments (4, 5) and in a flow path (16) through the bypass channel (7).

12. The method according to claim 11, characterized in that pressure loss is regulated independently in the flow path (15) and the second flow path (16), so that pressure fluctuations at the gas inlet (2) are minimized when switching between the flow path (15) and the second flow path (16).

13. The method according to claim 11, further comprising (iii) separating out from the gas stream a liquid that was loaded into the gas stream in order to reduce exhaust gas concentration.

14. An apparatus for wet cleaning a gas stream, comprising: a housing with a gas inlet and at least two gas outlets and defining a first flow path of the gas stream and a second flow path of the gas stream; at least one washing segment in the housing adapted to clean the gas stream with a washing liquid, said at least one washing segment being arranged in the first flow path of the gas stream; at least one fan inside the housing adapted to regulate air pressure along the first flow path of the gas stream; a bypass channel in the housing defining the second flow path, said second flow path bypassing the first flow path through the at least one washing segment; a baffle element adapted to switch over a gas feed between the second flow path through the bypass channel and the first flow path through the at least one washing segment; and a regulator installed in the bypass channel and adapted to discharge the gas stream being conveyed via the bypass channel and to maintain gas pressure of the gas stream in the bypass channel.

15. The apparatus of claim 14, further comprising a second washing segment arranged in the first flow path in series with the first washing segment.

16. The apparatus of claim 14, further comprising a second washing segment in the housing and arranged side by side with the first washing segment.

17. The apparatus of claim 15, further comprising at least one liquid separator arranged in the first flow path downstream from the first washing segment and in an area of deflection of the first flow path between the first washing segment and the second washing segment.

18. The apparatus of claim 14, wherein the regulator is a bypass pump.

Description

DESCRIPTION OF THE DRAWINGS

(1) In this context, the following is shown, at times schematically:

(2) FIG. 1 a device for the wet cleaning of a gas stream, comprising two washing segments and a bypass channel;

(3) FIG. 2 a view of a first flow path of the gas stream through the washing segments; and

(4) FIG. 3 a view of a second flow path of the gas stream through the bypass channel.

(5) For the sake of clarity, identical components or those having the same effect are provided with the same reference numerals in the following figures, making reference to an embodiment.

DETAILED DESCRIPTION

(6) FIG. 1 shows a device 10 for the wet cleaning of a gas stream, a so-called wet scrubber. This is a system for cleaning exhaust air from wet-chemical processes, for example, in the semiconductor industry. In this context, isopropyl alcohol (IPA), ammonia and hydrogen fluoride in the production installations have to be disposed of.

(7) The exhaust air that is to be cleaned is fed into a cleaning segment of the device 10 via a gas inlet 2 arranged in a housing 1 of the device 10 so that the noxious gases can be removed from the exhaust air by means of chemical absorption and can then be discharged via a gas outlet 3 likewise arranged in the housing 1.

(8) The device 10 can be equipped with a suitable adapter at the gas inlet 2 having up to twelve separate connections for feed lines. If the system is dimensioned to treat gas streams between 1000 m.sup.3/h and 4500 m.sup.3/h, the footprint of the device in the present embodiment amounts to a mere 2.5 m.sup.2, with a height of approximately 1.7 meters.

(9) The gas stream containing the noxious gases can first be fed into a pre-scrubber and pre-washed by means of spray nozzles 9.

(10) Subsequently, the gas stream reaches a first washing segment 4 arranged in the flow path 15 of the gas stream so that the gas stream can be cleaned with a washing liquid. In the present embodiment, the first washing segment 4 has a filler material packing or a packed column 23, wherein the gas stream flows through the washing segment 4 from the bottom to the top. The washing segment 4 can be supplied with a first washing liquid via additional spray nozzles 21 installed above the filler material packing 23.

(11) As shown in FIG. 1, the first washing liquid trickles through the filler material packing 23 from the top to the bottom. The filler material packing 23 can be implemented in the form of a packing of suitable filler material placed onto a perforated sieve tray. The gas stream is fed from below through the first washing segment 4. In this manner, the large surface area of the filler material and the counter-current principle ensure an optimal absorption of the noxious gases from the gas stream.

(12) After the gas stream has flowed through the first washing segment 4, it then flows through a droplet separator or liquid separator 17 that is located downstream from the first washing segment 4 in a first deflection area 19 in order to prevent any entrainment of washing liquid.

(13) Subsequently, the gas stream reaches a second washing segment 5 and, as a rule, it is washed with a different washing liquid. As an alternative, the same washing liquid as that of the first washing segment 4 can be used. Therefore, components of the noxious gases that have not reacted in the first washing segment 4 can be better absorbed in the second washing segment 5. In the present embodiment, the second washing segment 5 likewise has a filler material packing 24 or a packed column that is sprayed by means of additional spray nozzles 22 for the second washing liquid. The gas stream flows through the second washing segment 5 from the top to the bottom in the same direction as the washing liquid.

(14) After the gas stream has flowed through the second washing segment 5, it is then fed into a second liquid separator 18 that is located downstream from the second washing segment 5 in a second deflection area 20 of the device 10.

(15) In the present embodiment, both washing segments 4, 5 are arranged one after the other in the flow path 15, as can be seen in FIGS. 1 to 3. Moreover, the washing segments 4, 5 are arranged in the housing 1 side by side, with the gas stream flowing in opposite directions.

(16) In the present embodiment, in order to ensure a compact design for the device 10, the gas stream in the first washing segment 4 runs in an upwards direction in a counter-current to the washing liquid and then, in the second washing segment 5, it runs downwards in the same direction as the liquid. In this manner, a deflection found in prior-art devices can be dispensed with and both washing stages 4, 5 can be installed next to each other in a compact arrangement.

(17) As can also be seen in FIG. 1, the device 10 has at least one fan 6 to regulate the air pressure along the flow path 15 of the gas stream inside the housing 1 of the device 10. In this manner, the system pressure is regulated and kept constant by the fan 6. The fan 6, whose frequency is preferably regulated, can achieve a pressure stability of ±10 Pa during the entire cleaning process.

(18) The fan 6 for the at least one washing segment 4 can be a radial fan in which, however, the inlet can be at bottom and the outlet can be at the top, in other words, along a single axis. In particular, it can be provided for the gas stream to be conveyed from below centrally onto the horizontal impeller through an opening in the baseplate on which the fan is mounted. The impeller accelerates the gas away from the axis towards the outside, from where it is discharged upwards. The drive of the fan is arranged centrally in the flow channel and is surrounded by the gas stream. It can also be provided for the flow channel in which the impeller is installed to be shaped so as not be round, but rather rectangular.

(19) Moreover, a bypass channel 7 for bypassing the flow path 15 through the washing segments 4, 5 and a regulator 8 situated in the bypass channel 7 are arranged in the housing 1 in order to discharge the gas stream that is being conveyed via the bypass channel 7. The gas stream flowing through the flow path 16 in the bypass channel 7 is discharged from the device 10 through the gas outlet 14 of the bypass channel 7.

(20) The regulator 8 can be configured as an automatically adjustable throttle valve. In the present embodiment, the regulator is configured as a bypass pump 8.

(21) The bypass pump 8 that serves to discharge the gas stream conveyed via the bypass channel 7 can be, for instance, an axial fan. Owing to the shape of the bypass pump 8 as well as of the fan 6, it is possible for the device 10 to have a very compact design.

(22) Owing to the bypass channel 7, the pressure on the gas inlet side can be maintained, even, for example, during maintenance work or in the case of a failure of the device 10, so that impurities in the upstream process system caused by a standstill of the device 10 are virtually ruled out. In the case of maintenance work or a malfunction, the gas stream can bypass the two washing segments 4, 5 via the bypass channel 7.

(23) In the present embodiment, the bypass channel 7 runs essentially below the washing segments 4, 5, so that the compact design of the device 10 is improved even further.

(24) In the embodiment shown in FIG. 1, the gas outlet 3 for the washing segments 4, 5 and the gas outlet 14 of the bypass channel 7 are arranged next to each other in the housing 1; in particular, the fan 6 and the bypass pump 8 are arranged in adjacent channels of the device 10.

(25) As an alternative, these channels can also be arranged one after the other in the device, as can be seen in FIGS. 2 and 3.

(26) As can also be seen in FIGS. 1 to 3, a baffle element 11 is provided for switching the gas flow over between the flow path 16 of the gas stream through the bypass channel 7 and the flow path 15 through the at least one washing segment 4.

(27) Moreover, the baffle element 11 can be arranged in the vicinity of the gas inlet 2. The gas stream can be fed in from the side, below the first filler material packing 23.

(28) The baffle element 11 is configured so that, irrespective of its position, it conveys the washing liquid of the first washing segment 4 into a collecting tank 12 for the first washing liquid. Furthermore, a second collecting tank 13 can be provided for the second washing liquid. It is also conceivable for the first and second washing liquids to be fed into a single collecting tank 12, 13.

(29) The baffle element 11 can be moved by means of a drive (not shown here) between the bypass position and the position for the washing segments 4, 5.

(30) FIG. 1 shows the baffle element 11 with a solid line in a position in which the gas stream is being conveyed through the washing segments 4, 5. The dash-dot line of the baffle element 11 in FIG. 1 illustrates the bypass channel position of the baffle element 11.

(31) The arrows in FIG. 2 show the flow path of the gas stream through the washing segments 4, 5. The baffle element 11 is in a position in which the gas stream that is flowing into the gas inlet 2 is conveyed into the first washing segment 4. As already elaborated upon above, the gas stream then flows through the liquid separator 17 situated in the first deflection area 19 and enters the second washing segment 5. Subsequently, the gas stream flows through the second liquid separator 18 and is discharged from the device 10 via the fan 6 through the gas outlet 3.

(32) The bypass channel 7 is not shown in the depiction of the device 10 in FIG. 2 since it would obstruct the view of the outlet channel with the gas outlet 3 and the two collecting tanks 12, 13.

(33) The flow path 16 of the gas stream through the bypass channel 7 is indicated by the arrows in FIG. 3. In this case as well, the gas stream enters the device 10 via the gas inlet 2 and then, as a function of the position of the baffle element 11, it is not conveyed into the first washing segment 4 but rather into the bypass channel 7, in other words, it flows around the washing segments 4, 5. The gas stream is then discharged from the device 10 via the gas outlet 14 of the bypass channel 7. The regulator 8 supplies the pressure needed for the gas stream to flow through the bypass channel 7.

(34) The collecting tanks 12, 13 of the fan 6 and of the gas outlet 3 are not depicted in FIG. 3 because they are situated behind the bypass channel 7.

(35) Detachable connections can be provided on the device 10 between the first washing segment 4 and the second washing segment 5 so that the assembled device 10 can be broken down into at least two modules. In this manner, the components can be pre-assembled, which allows simple transportation as well as quick assembly of the device 10 at the installation site.

(36) Thanks to this device, air can be conveyed through the bypass channel 7 as well as through the washing segments 4, 5 inside a compact housing 1. There is no longer a need for external structures as is the case in prior-art devices for the wet cleaning of gas streams. This reduces not only the installation space but also the installation time.

(37) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this disclosure is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure as defined by the appended claims.

LIST OF REFERENCE NUMERALS

(38) 1 housing 2 gas inlet 3 gas outlet 4 first washing segment 5 second washing segment 6 fan 7 bypass channel 8 regulator 9 spray nozzle 10 device 11 baffle element 12 collecting tank for the first washing liquid 13 collecting tank for the second washing liquid 14 gas outlet of the bypass channel 15 flow path of the washing segment 16 flow path of the bypass channel 17 liquid separator 18 liquid separator 19 deflection area 20 deflection area 21 spray nozzles for the first washing liquid 22 spray nozzles for the second washing liquid 23 filler material packing 24 filler material packing