REACTOR FOR THE CATALYTIC TREATMENT OF A GAS STREAM

Abstract

A reactor may have a catalyst bed for the catalytic treatment of a gas stream, with the catalyst bed extending substantially over a cross section of the reactor. Gas to be treated may axially fly through the catalyst bed. A carrier structure for the catalyst bed that is at least partly floatingly mounted in the reactor may include a sieve element and, radially outwardly, carrier elements fixedly joined to the reactor wall below the sieve element. The sieve element provides a resting surface for the catalyst bed. The sieve element terminates, radially outwardly, at a distance from the reactor wall. The carrier structure also includes support elements for the sieve element that are floatingly mounted in the reactor. An improved floating mounting is thus provided where not only the sieve element itself but also further parts of the carrier structure are mounted to prevent stresses due to thermal expansion.

Claims

1.-21. (canceled)

22. A reactor for catalytic treatment of residual gas for reducing a content of nitrogen oxides in processes for producing nitric acid by the Ostwald process, comprising: a catalyst bed for catalytic treatment of a gas stream, wherein the catalyst bed extends substantially over a cross section of the reactor and the catalyst bed is axially flown through by gas to be treated; a carrier structure for the catalyst bed that is at least partly floatingly mounted in the reactor, wherein the carrier structure comprises: a sieve element, radially outwardly, carrier elements fixedly joined to a reactor wall below the sieve element, wherein the sieve element provides a resting surface for the catalyst bed, wherein the sieve element terminates, radially outwardly, at a distance from the reactor wall, and support elements for the sieve element that are floatingly mounted in the reactor.

23. The reactor of claim 22 wherein the carrier elements fixedly joined to the reactor wall comprise brackets on which the support elements displaceably rest, wherein the sieve element rests on the displaceable support elements.

24. The reactor of claim 23 wherein two or more of the brackets are respectively spaced apart from one another in a longitudinal direction or in a circumferential direction of the reactor, wherein the support elements displaceably rest on the two or more of the brackets, wherein the sieve element rests on one or more of the support elements.

25. The reactor of claim 23 wherein the support elements displaceably rest on the brackets with two degrees of freedom of motion in two directions approximately perpendicular to one another.

26. The reactor of claim 25 wherein the support elements rest on the brackets such that the support elements are displaceable in a longitudinal direction of the brackets and in a transverse direction of the brackets.

27. The reactor of claim 23 wherein the brackets are wider in a transverse direction of the brackets than the support elements.

28. The reactor of claim 23 wherein the support elements terminate at a distance from the reactor wall.

29. The reactor of claim 23 wherein cheeks are mounted to the brackets such that the cheeks limit displaceable motion of the support elements relative to the brackets in a transverse direction of the brackets.

30. The reactor of claim 29 wherein in each case two parallel cheeks of the cheeks are spaced apart from one another and are mounted on both sides of the brackets, wherein the two parallel cheeks are joined to one another via a spacer element extending in a transverse direction.

31. The reactor of claim 30 comprising a sleeve that is force-locked connected to the two parallel cheeks as the spacer element.

32. The reactor of claim 30 wherein each support element comprises a slot and extends through a slot transverse to the support element.

33. The reactor of claim 23 wherein the carrier structure comprises a carrier element circumferentially arranged at the reactor wall and jointed thereto, wherein the sieve element floatingly rests on the carrier element at a distance from the reactor wall such that an edge gap between the sieve element and the reactor wall remains.

34. The reactor of claim 22 comprising a circumferential cover plate that covers an edge gap between the sieve element and the reactor wall.

35. The reactor of claim 34 wherein an edge region of the sieve element that faces the reactor wall is enclosed by the circumferential cover plate and a carrier element of the carrier structure that is circumferentially arranged at the reactor wall and jointed thereto.

36. The reactor of claim 22 configured as: a horizontal reactor where the residual gas flows through the catalyst bed substantially perpendicularly or transversely to a vessel axis, or a vertical reactor where the residual gas flows through the catalyst bed substantially in an axis direction or parallel to a vessel axis.

37. The reactor of claim 22 comprising stiffening ribs that are approximately vertically oriented, extend along the sieve element, and are spaced apart from one another, with the stiffening ribs being disposed above or below the sieve element in the catalyst bed.

38. The reactor of claim 22 wherein the catalyst bed is a first catalyst bed, the reactor comprising a second catalyst bed, wherein the catalyst beds are spaced apart from one another, wherein at least a portion of the gas stream flows via a first inlet to the first catalyst bed, wherein at least a portion of the gas stream flows via a second inlet to the second catalyst bed.

39. The reactor of claim 38 wherein the first inlet and the second inlet are fluidically connected to one another via an inlet manifold.

40. The reactor of claim 38 wherein at least a portion of the gas stream is dischargeable from the reactor via a first outlet in a region of the first catalyst bed, wherein at least a portion of the gas stream is dischargeable from the reactor via a second outlet in a region of the second catalyst bed.

41. The reactor of claim 40 wherein the first outlet and the second outlet are fluidically connected to one another via an outlet manifold.

42. The reactor of claim 38 wherein the first catalyst bed and the second catalyst bed are fluidically separated from one another by a separating element.

Description

[0056] The present invention is described in more detail below on the basis of exemplary embodiments with reference to the enclosed drawings. In the figures:

[0057] FIG. 1 shows a schematically simplified longitudinal section through an inventive residual gas reactor of a plant for producing nitric acid according to an exemplary embodiment of the present invention;

[0058] FIG. 2 shows a schematically simplified cross section through the residual gas reactor according to the exemplary embodiment of FIG. 1;

[0059] FIG. 3 is an enlarged detail view showing part of a cross section through the residual gas reactor, wherein the floating mounting of the sieve plate is shown;

[0060] FIG. 4 is an enlarged detail view showing a vertical section through the view of FIG. 3 along the line A-A;

[0061] FIG. 5 is a schematic illustration of an exemplary embodiment of a reactor having two catalyst beds.

[0062] The following refers initially to FIG. 1 and a first exemplary variant of the invention is more particularly elucidated with reference to this illustration. The representation of the reactor in FIG. 1 is a simplified schematic diagram and only the plant components that are relevant in the context of the present invention are shown. FIG. 1 shows a possible alternative variant of the reactor according to the invention which is a horizontal reactor. This means that the axis 15 of the reactor vessel 10 is substantially horizontal and the catalyst bed 14 in principle extends in the direction of this axis or parallel thereto. FIG. 1 shows the catalyst bed 14 which extends in the longitudinal direction (axis direction) of the reactor vessel 10, generally over its entire length. Since the gases to be purified flow into the vessel at the top via the first inlet 16 and flow through said vessel perpendicular to its axis 15 the catalyst bed 14 is flown through by the gases axially in the arrowed direction. In the upper region of the reactor interior, the gases impact a deflection plate 17 so that they are more uniformly distributed over the vessel cross section. The gases then flow axially in the arrowed direction through the catalyst bed and then exit the vessel via the first outlet 18.

[0063] Stiffening ribs 19, which in the illustration according to FIG. 1 lie in the catalyst bed, extend in the longitudinal direction in the reaction vessel 10 above a sieve plate 20 on which the catalyst bed 14 rests.

[0064] FIG. 2 shows a simplified schematic cross section through the reactor vessel 10 of FIG. 1 from which it is apparent that the reactor vessel 10 has an approximately cylindrical shape and that the catalyst bed 14 also extends over the entire cross section of the reactor when viewed in the transverse direction of the reactor vessel 10, so that the gases to be purified must flow through the catalyst bed. Further details of the carrier structure for resting the sieve plate, on which the catalyst bed in turn rests, are apparent from the detail illustrations of FIGS. 3 and 4, which are referred to below.

[0065] FIG. 3 shows a detail view of a cross-sectional illustration of the reactor vessel, similar to that in FIG. 2, but on an enlarged scale. This view shows parts of the carrier structure for the floating mounting of the sieve plate 20 in the reactor vessel 10. This sieve plate 20 on which the catalyst bed 14 rests terminates at a slight distance to the reactor wall 11 so that an edge gap 21 between the outer edge of the sieve plate 20 and the reactor wall 11 remains, wherein the sieve plate 20 in its outer edge region floatingly rests at a distance from the reactor wall on a carrier element 22 circumferentially arranged at the reactor wall and joined, for example welded, thereto. This makes it possible for the perforated plate to be displaced further into the gap 21 in the event of thermal expansion without material stresses occurring. Also provided is at least one circumferential cover plate 23 which covers the edge 21 between the sieve plate 20 and the reactor wall 11, thus preventing the catalyst bed from trickling into the slot between the sieve element and the vessel wall. The edge region of the sieve plate 20 is thus sandwiched between the circumferential carrier element 22 and the cover plate 23. The circumferential carrier element 22 may be a flat iron or the like for example.

[0066] The carrier structure for the sieve plate 20 further comprises support elements 24 on which the underside of the sieve plate 20 rests, wherein the support elements 24 are likewise floatingly mounted and terminate at a distance from the circumferential carrier element 22 as indicated by the double arrow 25 in FIG. 3. This makes it possible for the support elements 24 to move in the direction of the double arrow 25, i.e. in the transverse direction, in the reactor vessel 10 in the event of thermal expansion. The carrier structure for the sieve plate 20 also comprises brackets 12 which are firmly joined to the wall 11 of the reactor vessel 10, for example by welding, and on which the support elements 24 are in turn floatingly mounted. A limiting of the transverse displacement of the support elements 24 is ensured by cheeks 13 which comprise a slot 27 or an elongate hole, through which a sleeve 26 extends in the transverse direction to the cheeks 13 (see FIG. 4).

[0067] Further details relating to the floating mounting of the support elements 24 are apparent from the illustration of FIG. 4 which shows a view in the direction of arrow A of FIG. 3 and thus a detail view in the longitudinal direction of the reactor vessel 10 and which is referred to below. Apparent in FIG. 4 are two of the brackets 12 of the carrier structure which are each enclosed on both sides by two cheeks 13 which are in turn fixedly joined to the brackets 12. These cheeks 13 extend parallel to the brackets 12 and are fixedly joined to the brackets, for example by a weld. The cheeks 13 respectively laterally flank the brackets 12 on both sides and extend beyond these in the upward direction. The brackets 12 extend radially outward towards the wall 11 of the reactor vessel and are fixedly joined thereto, as shown in FIG. 3. It is apparent from FIG. 4 that the brackets 12, on which the support elements 24 floatingly rest, are wider than the support elements 24 themselves. The sleeves 26 extend transversely to the support elements 24, extend through the support elements 24 and the two cheeks 13 and are fixed to the cheeks 13 via a screw connection for example. Since the support elements 24 which rest on the brackets 12 are narrower than the brackets they can also move in the transverse direction relative to the brackets, guided by the sleeves 26, to achieve a floating mounting of the support elements 24 resulting in two degrees of freedom of motion, namely in the transverse direction and in the longitudinal reaction toward the reactor wall (see double arrow 25 in FIG. 3). The cheeks 13 prevent the support elements 24 from slipping off the brackets 12 on which they rest in the event of excessive motion in the transverse direction.

[0068] The sieve plate 20 in turn rests on the top surface of the support elements 24, in each case bridging the distance between two adjacent support elements 24, as is apparent from FIG. 4. The sieve plate 20 rests loosely on the support elements and is thus also floatingly mounted. At its outer end, viewed in the transverse direction of the reactor vessel (see FIG. 3), the sieve plate 20 is enclosed between the circumferential carrier element 22 and the cover plate 23 and floatingly mounted. Viewed in the longitudinal direction of the reactor vessel 10 the sieve plate 20 likewise terminates before the wall of the reactor vessel so that here too there is clearance in the case of thermal expansion of the sieve plate 20, Resting on the sieve plate 20 is initially a wire mesh 28 (see FIGS. 3 and 4), the catalyst bed 14 then in turn resting thereupon.

[0069] The catalyst bed 14 may have a bed of ceramic beads applied atop it which is intended to compensate any nonuniform settling of the catalyst bed and prevent fluidization of the catalyst by the gas stream.

[0070] Alternatively, or optionally in addition, a grating with wire mesh attached below it may be placed directly on the catalyst bed 14 or on the ceramic beads. These serve as a hold-down for the catalyst bed and the use of gratings can additionally achieve gas flow alignment (the gas cannot flow transversely into the catalyst bed, only vertically through the grating).

[0071] FIG. 5 shows an embodiment of a reactor vessel 10 having a first catalyst bed 14 and a second catalyst bed 14′. The reactor vessel 10 is a dual-flow reactor. Via a first inlet 16, a portion of the gas stream can flow through the first catalyst bed 14 and exits the reactor vessel 10 through a first outlet 18. Via a second inlet 18 a further portion of the gas stream can flow through the second catalyst bed 14′ and exits the reactor vessel 10 through a second outlet 18′ The first inlet 16 and the second inlet 16′ are fluidically connected to one another via an inlet manifold 29. The gas stream is divided inside the inlet manifold 29 so that both the first catalyst bed 14 and the second catalyst bed 14′ are flown through.

[0072] The first outlet 18 and the second outlet 18′ are fluidically connected to one another by means of an outlet manifold 30, The gas stream passed through the first catalyst bed and the gas stream passed through the second catalyst bed are recombined via the outlet manifold 30. The two catalyst bed 14, 14′ are also fluidically separated from one another by means of a separating element 31 in the form of a separating plate. This makes it possible to avoid bypass flows. The two catalyst beds 14, 14′ are therefore connected in parallel, wherein respective portions of the gas stream are passed through the first catalyst bed 14 and the second catalyst bed 14′ respectively.

[0073] Access to the assembly and filling of the catalyst beds 14, 14′ with catalyst is carried out via manholes and, in this exemplary embodiment, via filling port 32. Used catalyst can also be replaced, in particular removed by suction, via filling port 32. The gas flow is uniformly distributed in the reactor vessel 10 via gas distributors 33.

LIST OF REFERENCE NUMERALS

[0074] 10 Reactor vessel [0075] 11 Wall of reactor vessel, reactor wall [0076] 12 Brackets, carrier elements [0077] 13 Cheeks [0078] 14 (First) catalyst bed [0079] 14′ Second catalyst bed [0080] 15 Axis [0081] 16 First inlet [0082] 16′ Second inlet [0083] 17 Deflection plate [0084] 18 First outlet [0085] 18′ Second outlet [0086] 19 Stiffening ribs [0087] 20 Sieve plate [0088] 21 Edge gap [0089] 22 Carrier element [0090] 23 Cover plate [0091] 24 Support elements [0092] 25 Double arrow [0093] 26 Sleeve, spacer element [0094] 27 Slot, elongate hole [0095] 28 Wire mesh [0096] 29 Intake manifold [0097] 30 Outlet manifold [0098] 31 Separating element [0099] 32 Filling port [0100] 33 Gas distributor