AIR SCRUBBER HAVING AN INTERIOR AIR EXHAUST

Abstract

An exhaust air scrubber for removing dust, abraded product, and water-soluble constituents from process exhaust air may include in a single housing a cleaning stage that includes a droplet separator and a packing disposed below the droplet separator. The exhaust air scrubber may also include an inlet apparatus for process exhaust air disposed in a lower portion of the housing, a withdrawal apparatus for scrubbing solution, and a withdrawal conduit for cleaned exhaust air, with the withdrawal conduit beginning inside the housing above the cleaning stage, passing downward inside the housing, and passing out of the housing to an outside in the lower portion of the housing below the cleaning stage. The scrubber may further include a feed conduit for scrubbing solution in an upper portion of the housing above the cleaning stage.

Claims

1.-19. (canceled)

20. An exhaust air scrubber for removing dust, abraded product, and water-soluble constituents from process exhaust air, the exhaust air scrubber comprising in a single housing: a cleaning stage that includes a droplet separator, and a packing disposed below the droplet separator; an inlet apparatus for process exhaust air disposed in a lower portion of the housing; a withdrawal apparatus for scrubbing solution; a withdrawal conduit for cleaned exhaust air, wherein the withdrawal conduit begins inside the housing above the cleaning stage, passes downward inside the housing, and passes out of the housing to an outside in the lower portion of the housing below the cleaning stage; and a feed conduit for scrubbing solution in an upper portion of the housing above the cleaning stage.

21. The exhaust air scrubber of claim 20 wherein the lower portion of the housing narrows, wherein the withdrawal apparatus is disposed at the lower portion of the housing.

22. The exhaust air scrubber of claim 21 wherein the withdrawal apparatus is disposed at a lowest point in a center of the housing where the housing narrows.

23. The exhaust air scrubber of claim 20 wherein the withdrawal conduit is disposed in a middle of the housing.

24. The exhaust air scrubber of claim 20 wherein the withdrawal conduit passes laterally outwards out of the housing in the lower portion of the housing below the cleaning stage.

25. The exhaust air scrubber of claim 20 wherein the withdrawal conduit inside the housing is configured as an anchoring point for internal attachments.

26. The exhaust air scrubber of claim 20 wherein the withdrawal conduit inside the housing is connected to at least one of a suction apparatus or an exhaust air blower via one or more conduits.

27. The exhaust air scrubber of claim 20 configured such that a portion of scrubbing solution or process medium withdrawn at a bottom is injected into a conical lower portion of the housing.

28. The exhaust air scrubber of claim 20 comprising an apparatus for measuring physical parameters of material that accumulates in the lower portion of the housing.

29. The exhaust air scrubber of claim 20 comprising nozzles that are attached upstream of the droplet separator for spraying water onto the droplet separator.

30. The exhaust air scrubber of claim 20 comprising a heat exchanger installed downstream of the cleaning stage.

31. The exhaust air scrubber of claim 20 comprising gas- or air-supplying means disposed downstream of the cleaning stage.

32. The exhaust air scrubber of claim 20 wherein the cleaning stage is a first cleaning stage, wherein the exhaust air scrubber includes a second cleaning stage and a third cleaning stage, wherein: each of the cleaning stages has independent feed and control apparatuses for scrubbing liquids, additions, and/or operating parameters to be used in the respective cleaning stage; the first and second cleaning stages, but not the third cleaning stage, have common feed and control apparatuses for scrubbing liquids, additions, and/or operating parameters to be used in the respective cleaning stage; or all of the cleaning stages have common feed and control apparatuses for scrubbing liquids, additions, and/or operating parameters to be used in the respective cleaning stage.

33. The exhaust air scrubber of claim 20 wherein the cleaning stage is a first cleaning stage, wherein the exhaust air scrubber includes a second cleaning stage, wherein the first and second cleaning stages are arranged in series, wherein the first cleaning stage in a flow direction of air is configured for alkaline and neutral operation, wherein the second cleaning stage is configured for acidic pH operation.

34. The exhaust air scrubber of claim 20 configured such that scrubbing solution withdrawn at a bottom is at least partially passed to the feed conduit in the upper portion of the housing.

35. The exhaust air scrubber of claim 20 configured such that at least a substream of previously-pre-cleaned air passes through a second cleaning stage.

36. The exhaust air scrubber of claim 20 configured such that the cleaning stage is pH-adjustable by adding mineral acid.

37. The exhaust air scrubber of claim 20 configured as part of a plant for producing ammonium nitrate- or urea-containing prilled or granulated product.

38. The exhaust air scrubber of claim 20 configured for offgas cleaning in a production of ammonium nitrate-, ammonium sulfate- or urea-containing prilled or granulated product.

Description

[0091] Description of the figures:

[0092] FIG. 1 shows an exhaust air scrubber according to the invention.

[0093] The process exhaust air 3 to be cleaned is passed into the housing Oa of the exhaust air scrubber 0 via a feed conduit. Simultaneously the cleaned exhaust air is withdrawn elsewhere on the exhaust air scrubber 0 via the exhaust air blower 7. As a result of the thus produced pressure difference, the process exhaust air 3 introduced into the exhaust air scrubber 0 is conveyed through the packing 2 or packings of an optionally present scrubbing tray 9, shown here in the drawing, and via a droplet separator 1 into the upper region of the exhaust air scrubber 0. The process exhaust air 3 is cleaned by a countercurrent of an aqueous scrubbing solution. The thus cleaned process exhaust air then in the upper region of the exhaust air scrubber 0 enters the centrally arranged withdrawal conduit 13, preferably in the form of a pipe, for the exhaust air 8 and is conveyed out of the exhaust air scrubber 0 and discharged as cleaned exhaust air via the exhaust air blower 7. The conveying of the air may alternatively also be effected via a blower arranged upstream of the exhaust air scrubber 0. The scrubbing solution 11 which may preferably be an aqueous solution of the scrubbed out substances and which is introduced above the scrubbing stage 2 in the upper region of the exhaust air scrubber 0 flows in conformance with the gravitational force and in countercurrent to the process exhaust air 3 to be cleaned through the scrubbing tray 9 and the packing 3 downward into the lower region of the exhaust air scrubber 0. Supplying of the scrubbing solution 11 into the scrubber is effected for example via customary liquid distributors, for example pipe or trough distributors. The figure shows a preferred embodiment of the present invention in which the lower region of the exhaust air scrubber 0 is here shown as conical though this is not mandatory for the present invention. The scrubbing stage 2 may also consist of a plurality of scrubbing stages each having assigned scrubbing water circuits. Arranged at the lower end of the exhaust air scrubber 0, at the tip of the conical portion in the drawing, is a withdrawal apparatus 4 for the scrubbing solution. The scrubbing solution is withdrawn from the lower region of the exhaust air scrubber 0 and recycled back to the upper portion of the exhaust air scrubber 0 via the recirculation pump 5. In contrast to FIG. 1 the scrubbing solution may also flow from the bottom of the scrubber into a separate container and from there be supplied to the recirculation pump 5. FIG. 1 shows a reintroduction of the supplied, recirculated scrubbing solution 11 between the packing 2 and the scrubbing tray 9 but it is likewise possible to introduce the recirculated scrubbing solution inside the packing region. The figure thus shows in simplified form that the recirculated scrubbing solution 11 is recycled into the exhaust air scrubber 0 at one site; however it is likewise possible and comprised by the present invention that the scrubbing solution may be passed into the housing Oa of the exhaust air scrubber 0 at a plurality of sites. The drawing further shows that the scrubbing liquid withdrawn from the exhaust air scrubber 0 at the lower end can be cleaned of accumulating impurities via a desludging 6. In the context of the present invention this desludging/cleaning of the scrubbing liquid is carried out according to the extent of contamination of the scrubbing liquid and thus also according to the extent of contamination of the supplied process exhaust air 3. The drawing shows an addition of feed water 10 which is supplied to the recirculated scrubbing solution 11. This water feed may also be effected at another site, for example directly into the scrubber or upstream of the recirculation pump 5. The figure shows water additions 14a for rinsing the droplet separator 1 and 14b for an optionally used scrubbing tray. These water additions may have the same origin as the feed water 10 but may also derive from various other systems. In the drawing stream 12 shows by way of example a scrubbing solution stream preferably tangentially introduced into the narrowing lower scrubber portion. However, this stream 12 may also employ a different medium, for example the feed water 10. In the drawing stream 15 shows the addition of a mineral acid for scavenging ammonia from the air 3 to be cleaned. This addition may for example also be carried out upstream of the recirculation pump 5 or directly into the exhaust air scrubber 0. Measurement of the pH necessary for the control may be carried out upstream or downstream of the acid addition. In the drawing the portion 13 of the withdrawal conduit for the exhaust air 8 that is inside the housing 0a is shown arranged in the middle and centrally in the housing 0a of the exhaust air scrubber 0 and the outlet of the withdrawal conduit for the exhaust air 8 out of the housing 0a is shown opposite the inlet for the process exhaust air 3 into the housing 0a of the exhaust air scrubber 0 at about the same height of the housing 0a. This represents a preferred embodiment of the present invention. It is not mandatory for the portion 13 of the withdrawal conduit for the exhaust air 8 that is inside the housing 0a to be arranged precisely in the middle of the exhaust air scrubber 0 but it is advantageous. It is likewise possible in the context of the present invention for the withdrawal conduit for the exhaust air 8 to exit the housing 0a at another site.

[0094] It should be noted that the drawing is not to scale and is moreover a simplified representation. Customary apparatus details/necessities not necessary for the understanding of the present invention and familiar to those skilled in the art have been omitted (for example screws, valves or the like).

LIST OF REFERENCE NUMERALS

[0095] 0 Exhaust air scrubber

[0096] 0a Housing

[0097] 1 Droplet separator

[0098] 2 Packing

[0099] 3 Process air to be cleaned

[0100] 4 Withdrawal apparatus (for scrubbing solution)

[0101] 5 Recirculation pump

[0102] 6 Desludging

[0103] 7 Exhaust air blower

[0104] 8 Withdrawal conduit (for cleaned exhaust air)

[0105] 9 Scrubbing tray

[0106] 10 Water addition (for example water, process condensate, diluted process solution)

[0107] 11 Recirculating scrubbing solution

[0108] 12 Injected scrubbing solution

[0109] 13 Internal portion of air withdrawal conduit

[0110] 14a, b Water addition to droplet separator/scrubbing tray

[0111] 15 Mineral acid (for example nitric acid, sulfuric acid)

[0112] A Flow direction of the scrubbing solution

[0113] B Flow direction of the air